+++ /dev/null
-#![allow(rustc::default_hash_types)]
-
-use std::borrow::Cow;
-use std::cmp::Ordering;
-use std::collections::BTreeMap;
-
-use if_chain::if_chain;
-use rustc_ast::{LitFloatType, LitIntType, LitKind};
-use rustc_errors::{Applicability, DiagnosticBuilder};
-use rustc_hir as hir;
-use rustc_hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
-use rustc_hir::{
- BinOpKind, Block, Body, Expr, ExprKind, FnDecl, FnRetTy, FnSig, GenericArg, GenericBounds, GenericParamKind, HirId,
- ImplItem, ImplItemKind, Item, ItemKind, LangItem, Lifetime, Lit, Local, MatchSource, MutTy, Mutability, Node,
- QPath, Stmt, StmtKind, SyntheticTyParamKind, TraitFn, TraitItem, TraitItemKind, TyKind, UnOp,
-};
-use rustc_lint::{LateContext, LateLintPass, LintContext};
-use rustc_middle::hir::map::Map;
-use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::TypeFoldable;
-use rustc_middle::ty::{self, FloatTy, InferTy, IntTy, Ty, TyCtxt, TyS, TypeAndMut, TypeckResults, UintTy};
-use rustc_semver::RustcVersion;
-use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
-use rustc_span::hygiene::{ExpnKind, MacroKind};
-use rustc_span::source_map::Span;
-use rustc_span::symbol::sym;
-use rustc_target::abi::LayoutOf;
-use rustc_target::spec::abi::Abi;
-use rustc_typeck::hir_ty_to_ty;
-
-use crate::consts::{constant, Constant};
-use crate::utils::paths;
-use crate::utils::sugg::Sugg;
-use crate::utils::{
- clip, comparisons, differing_macro_contexts, get_qpath_generic_tys, higher, in_constant, indent_of, int_bits,
- is_hir_ty_cfg_dependant, is_ty_param_diagnostic_item, is_ty_param_lang_item, is_type_diagnostic_item,
- last_path_segment, match_def_path, match_path, meets_msrv, method_chain_args, multispan_sugg,
- numeric_literal::NumericLiteral, reindent_multiline, sext, snippet, snippet_opt, snippet_with_applicability,
- snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then, unsext,
-};
-
-declare_clippy_lint! {
- /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
- /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
- ///
- /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
- /// the heap. So if you `Box` it, you just add another level of indirection
- /// without any benefit whatsoever.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust,ignore
- /// struct X {
- /// values: Box<Vec<Foo>>,
- /// }
- /// ```
- ///
- /// Better:
- ///
- /// ```rust,ignore
- /// struct X {
- /// values: Vec<Foo>,
- /// }
- /// ```
- pub BOX_VEC,
- perf,
- "usage of `Box<Vec<T>>`, vector elements are already on the heap"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
- /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
- ///
- /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
- /// the heap. So if you `Box` its contents, you just add another level of indirection.
- ///
- /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see [#3530](https://github.com/rust-lang/rust-clippy/issues/3530),
- /// 1st comment).
- ///
- /// **Example:**
- /// ```rust
- /// struct X {
- /// values: Vec<Box<i32>>,
- /// }
- /// ```
- ///
- /// Better:
- ///
- /// ```rust
- /// struct X {
- /// values: Vec<i32>,
- /// }
- /// ```
- pub VEC_BOX,
- complexity,
- "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
- /// definitions
- ///
- /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
- /// represents an optional optional value which is logically the same thing as an optional
- /// value but has an unneeded extra level of wrapping.
- ///
- /// If you have a case where `Some(Some(_))`, `Some(None)` and `None` are distinct cases,
- /// consider a custom `enum` instead, with clear names for each case.
- ///
- /// **Known problems:** None.
- ///
- /// **Example**
- /// ```rust
- /// fn get_data() -> Option<Option<u32>> {
- /// None
- /// }
- /// ```
- ///
- /// Better:
- ///
- /// ```rust
- /// pub enum Contents {
- /// Data(Vec<u8>), // Was Some(Some(Vec<u8>))
- /// NotYetFetched, // Was Some(None)
- /// None, // Was None
- /// }
- ///
- /// fn get_data() -> Contents {
- /// Contents::None
- /// }
- /// ```
- pub OPTION_OPTION,
- pedantic,
- "usage of `Option<Option<T>>`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
- /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
- ///
- /// **Why is this bad?** Gankro says:
- ///
- /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
- /// pointers and indirection.
- /// > It wastes memory, it has terrible cache locality, and is all-around slow.
- /// `RingBuf`, while
- /// > "only" amortized for push/pop, should be faster in the general case for
- /// almost every possible
- /// > workload, and isn't even amortized at all if you can predict the capacity
- /// you need.
- /// >
- /// > `LinkedList`s are only really good if you're doing a lot of merging or
- /// splitting of lists.
- /// > This is because they can just mangle some pointers instead of actually
- /// copying the data. Even
- /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
- /// can still be better
- /// > because of how expensive it is to seek to the middle of a `LinkedList`.
- ///
- /// **Known problems:** False positives – the instances where using a
- /// `LinkedList` makes sense are few and far between, but they can still happen.
- ///
- /// **Example:**
- /// ```rust
- /// # use std::collections::LinkedList;
- /// let x: LinkedList<usize> = LinkedList::new();
- /// ```
- pub LINKEDLIST,
- pedantic,
- "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a `VecDeque`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
- /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
- ///
- /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
- /// general.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust,ignore
- /// fn foo(bar: &Box<T>) { ... }
- /// ```
- ///
- /// Better:
- ///
- /// ```rust,ignore
- /// fn foo(bar: &T) { ... }
- /// ```
- pub BORROWED_BOX,
- complexity,
- "a borrow of a boxed type"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for use of redundant allocations anywhere in the code.
- ///
- /// **Why is this bad?** Expressions such as `Rc<&T>`, `Rc<Rc<T>>`, `Rc<Box<T>>`, `Box<&T>`
- /// add an unnecessary level of indirection.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// # use std::rc::Rc;
- /// fn foo(bar: Rc<&usize>) {}
- /// ```
- ///
- /// Better:
- ///
- /// ```rust
- /// fn foo(bar: &usize) {}
- /// ```
- pub REDUNDANT_ALLOCATION,
- perf,
- "redundant allocation"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for `Rc<T>` and `Arc<T>` when `T` is a mutable buffer type such as `String` or `Vec`.
- ///
- /// **Why is this bad?** Expressions such as `Rc<String>` usually have no advantage over `Rc<str>`, since
- /// it is larger and involves an extra level of indirection, and doesn't implement `Borrow<str>`.
- ///
- /// While mutating a buffer type would still be possible with `Rc::get_mut()`, it only
- /// works if there are no additional references yet, which usually defeats the purpose of
- /// enclosing it in a shared ownership type. Instead, additionally wrapping the inner
- /// type with an interior mutable container (such as `RefCell` or `Mutex`) would normally
- /// be used.
- ///
- /// **Known problems:** This pattern can be desirable to avoid the overhead of a `RefCell` or `Mutex` for
- /// cases where mutation only happens before there are any additional references.
- ///
- /// **Example:**
- /// ```rust,ignore
- /// # use std::rc::Rc;
- /// fn foo(interned: Rc<String>) { ... }
- /// ```
- ///
- /// Better:
- ///
- /// ```rust,ignore
- /// fn foo(interned: Rc<str>) { ... }
- /// ```
- pub RC_BUFFER,
- restriction,
- "shared ownership of a buffer type"
-}
-
-pub struct Types {
- vec_box_size_threshold: u64,
-}
-
-impl_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX, REDUNDANT_ALLOCATION, RC_BUFFER]);
-
-impl<'tcx> LateLintPass<'tcx> for Types {
- fn check_fn(&mut self, cx: &LateContext<'_>, _: FnKind<'_>, decl: &FnDecl<'_>, _: &Body<'_>, _: Span, id: HirId) {
- // Skip trait implementations; see issue #605.
- if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
- if let ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = item.kind {
- return;
- }
- }
-
- self.check_fn_decl(cx, decl);
- }
-
- fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
- self.check_ty(cx, &field.ty, false);
- }
-
- fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &TraitItem<'_>) {
- match item.kind {
- TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_ty(cx, ty, false),
- TraitItemKind::Fn(ref sig, _) => self.check_fn_decl(cx, &sig.decl),
- _ => (),
- }
- }
-
- fn check_local(&mut self, cx: &LateContext<'_>, local: &Local<'_>) {
- if let Some(ref ty) = local.ty {
- self.check_ty(cx, ty, true);
- }
- }
-}
-
-fn match_buffer_type(cx: &LateContext<'_>, qpath: &QPath<'_>) -> Option<&'static str> {
- if is_ty_param_diagnostic_item(cx, qpath, sym::string_type).is_some() {
- Some("str")
- } else if is_ty_param_diagnostic_item(cx, qpath, sym::OsString).is_some() {
- Some("std::ffi::OsStr")
- } else if is_ty_param_diagnostic_item(cx, qpath, sym::PathBuf).is_some() {
- Some("std::path::Path")
- } else {
- None
- }
-}
-
-fn match_borrows_parameter(_cx: &LateContext<'_>, qpath: &QPath<'_>) -> Option<Span> {
- let last = last_path_segment(qpath);
- if_chain! {
- if let Some(ref params) = last.args;
- if !params.parenthesized;
- if let Some(ty) = params.args.iter().find_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- });
- if let TyKind::Rptr(..) = ty.kind;
- then {
- return Some(ty.span);
- }
- }
- None
-}
-
-impl Types {
- pub fn new(vec_box_size_threshold: u64) -> Self {
- Self { vec_box_size_threshold }
- }
-
- fn check_fn_decl(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>) {
- for input in decl.inputs {
- self.check_ty(cx, input, false);
- }
-
- if let FnRetTy::Return(ref ty) = decl.output {
- self.check_ty(cx, ty, false);
- }
- }
-
- /// Recursively check for `TypePass` lints in the given type. Stop at the first
- /// lint found.
- ///
- /// The parameter `is_local` distinguishes the context of the type; types from
- /// local bindings should only be checked for the `BORROWED_BOX` lint.
- #[allow(clippy::too_many_lines)]
- fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, is_local: bool) {
- if hir_ty.span.from_expansion() {
- return;
- }
- match hir_ty.kind {
- TyKind::Path(ref qpath) if !is_local => {
- let hir_id = hir_ty.hir_id;
- let res = cx.qpath_res(qpath, hir_id);
- if let Some(def_id) = res.opt_def_id() {
- if Some(def_id) == cx.tcx.lang_items().owned_box() {
- if let Some(span) = match_borrows_parameter(cx, qpath) {
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- REDUNDANT_ALLOCATION,
- hir_ty.span,
- "usage of `Box<&T>`",
- "try",
- snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
- applicability,
- );
- return; // don't recurse into the type
- }
- if is_ty_param_diagnostic_item(cx, qpath, sym::vec_type).is_some() {
- span_lint_and_help(
- cx,
- BOX_VEC,
- hir_ty.span,
- "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
- None,
- "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation",
- );
- return; // don't recurse into the type
- }
- } else if cx.tcx.is_diagnostic_item(sym::Rc, def_id) {
- if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::Rc) {
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- REDUNDANT_ALLOCATION,
- hir_ty.span,
- "usage of `Rc<Rc<T>>`",
- "try",
- snippet_with_applicability(cx, ty.span, "..", &mut applicability).to_string(),
- applicability,
- );
- return; // don't recurse into the type
- }
- if let Some(ty) = is_ty_param_lang_item(cx, qpath, LangItem::OwnedBox) {
- let qpath = match &ty.kind {
- TyKind::Path(qpath) => qpath,
- _ => return,
- };
- let inner_span = match get_qpath_generic_tys(qpath).next() {
- Some(ty) => ty.span,
- None => return,
- };
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- REDUNDANT_ALLOCATION,
- hir_ty.span,
- "usage of `Rc<Box<T>>`",
- "try",
- format!(
- "Rc<{}>",
- snippet_with_applicability(cx, inner_span, "..", &mut applicability)
- ),
- applicability,
- );
- return; // don't recurse into the type
- }
- if let Some(alternate) = match_buffer_type(cx, qpath) {
- span_lint_and_sugg(
- cx,
- RC_BUFFER,
- hir_ty.span,
- "usage of `Rc<T>` when T is a buffer type",
- "try",
- format!("Rc<{}>", alternate),
- Applicability::MachineApplicable,
- );
- return; // don't recurse into the type
- }
- if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::vec_type) {
- let qpath = match &ty.kind {
- TyKind::Path(qpath) => qpath,
- _ => return,
- };
- let inner_span = match get_qpath_generic_tys(qpath).next() {
- Some(ty) => ty.span,
- None => return,
- };
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- RC_BUFFER,
- hir_ty.span,
- "usage of `Rc<T>` when T is a buffer type",
- "try",
- format!(
- "Rc<[{}]>",
- snippet_with_applicability(cx, inner_span, "..", &mut applicability)
- ),
- Applicability::MachineApplicable,
- );
- return; // don't recurse into the type
- }
- if let Some(span) = match_borrows_parameter(cx, qpath) {
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- REDUNDANT_ALLOCATION,
- hir_ty.span,
- "usage of `Rc<&T>`",
- "try",
- snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
- applicability,
- );
- return; // don't recurse into the type
- }
- } else if cx.tcx.is_diagnostic_item(sym::Arc, def_id) {
- if let Some(alternate) = match_buffer_type(cx, qpath) {
- span_lint_and_sugg(
- cx,
- RC_BUFFER,
- hir_ty.span,
- "usage of `Arc<T>` when T is a buffer type",
- "try",
- format!("Arc<{}>", alternate),
- Applicability::MachineApplicable,
- );
- return; // don't recurse into the type
- }
- if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::vec_type) {
- let qpath = match &ty.kind {
- TyKind::Path(qpath) => qpath,
- _ => return,
- };
- let inner_span = match get_qpath_generic_tys(qpath).next() {
- Some(ty) => ty.span,
- None => return,
- };
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- RC_BUFFER,
- hir_ty.span,
- "usage of `Arc<T>` when T is a buffer type",
- "try",
- format!(
- "Arc<[{}]>",
- snippet_with_applicability(cx, inner_span, "..", &mut applicability)
- ),
- Applicability::MachineApplicable,
- );
- return; // don't recurse into the type
- }
- } else if cx.tcx.is_diagnostic_item(sym::vec_type, def_id) {
- if_chain! {
- // Get the _ part of Vec<_>
- if let Some(ref last) = last_path_segment(qpath).args;
- if let Some(ty) = last.args.iter().find_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- });
- // ty is now _ at this point
- if let TyKind::Path(ref ty_qpath) = ty.kind;
- let res = cx.qpath_res(ty_qpath, ty.hir_id);
- if let Some(def_id) = res.opt_def_id();
- if Some(def_id) == cx.tcx.lang_items().owned_box();
- // At this point, we know ty is Box<T>, now get T
- if let Some(ref last) = last_path_segment(ty_qpath).args;
- if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- });
- let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
- if !ty_ty.has_escaping_bound_vars();
- if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env);
- if let Ok(ty_ty_size) = cx.layout_of(ty_ty).map(|l| l.size.bytes());
- if ty_ty_size <= self.vec_box_size_threshold;
- then {
- span_lint_and_sugg(
- cx,
- VEC_BOX,
- hir_ty.span,
- "`Vec<T>` is already on the heap, the boxing is unnecessary",
- "try",
- format!("Vec<{}>", snippet(cx, boxed_ty.span, "..")),
- Applicability::MachineApplicable,
- );
- return; // don't recurse into the type
- }
- }
- } else if cx.tcx.is_diagnostic_item(sym::option_type, def_id) {
- if is_ty_param_diagnostic_item(cx, qpath, sym::option_type).is_some() {
- span_lint(
- cx,
- OPTION_OPTION,
- hir_ty.span,
- "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
- enum if you need to distinguish all 3 cases",
- );
- return; // don't recurse into the type
- }
- } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
- span_lint_and_help(
- cx,
- LINKEDLIST,
- hir_ty.span,
- "you seem to be using a `LinkedList`! Perhaps you meant some other data structure?",
- None,
- "a `VecDeque` might work",
- );
- return; // don't recurse into the type
- }
- }
- match *qpath {
- QPath::Resolved(Some(ref ty), ref p) => {
- self.check_ty(cx, ty, is_local);
- for ty in p.segments.iter().flat_map(|seg| {
- seg.args
- .as_ref()
- .map_or_else(|| [].iter(), |params| params.args.iter())
- .filter_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- })
- }) {
- self.check_ty(cx, ty, is_local);
- }
- },
- QPath::Resolved(None, ref p) => {
- for ty in p.segments.iter().flat_map(|seg| {
- seg.args
- .as_ref()
- .map_or_else(|| [].iter(), |params| params.args.iter())
- .filter_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- })
- }) {
- self.check_ty(cx, ty, is_local);
- }
- },
- QPath::TypeRelative(ref ty, ref seg) => {
- self.check_ty(cx, ty, is_local);
- if let Some(ref params) = seg.args {
- for ty in params.args.iter().filter_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- }) {
- self.check_ty(cx, ty, is_local);
- }
- }
- },
- QPath::LangItem(..) => {},
- }
- },
- TyKind::Rptr(ref lt, ref mut_ty) => self.check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
- // recurse
- TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
- self.check_ty(cx, ty, is_local)
- },
- TyKind::Tup(tys) => {
- for ty in tys {
- self.check_ty(cx, ty, is_local);
- }
- },
- _ => {},
- }
- }
-
- fn check_ty_rptr(
- &mut self,
- cx: &LateContext<'_>,
- hir_ty: &hir::Ty<'_>,
- is_local: bool,
- lt: &Lifetime,
- mut_ty: &MutTy<'_>,
- ) {
- match mut_ty.ty.kind {
- TyKind::Path(ref qpath) => {
- let hir_id = mut_ty.ty.hir_id;
- let def = cx.qpath_res(qpath, hir_id);
- if_chain! {
- if let Some(def_id) = def.opt_def_id();
- if Some(def_id) == cx.tcx.lang_items().owned_box();
- if let QPath::Resolved(None, ref path) = *qpath;
- if let [ref bx] = *path.segments;
- if let Some(ref params) = bx.args;
- if !params.parenthesized;
- if let Some(inner) = params.args.iter().find_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- });
- then {
- if is_any_trait(inner) {
- // Ignore `Box<Any>` types; see issue #1884 for details.
- return;
- }
-
- let ltopt = if lt.is_elided() {
- String::new()
- } else {
- format!("{} ", lt.name.ident().as_str())
- };
-
- if mut_ty.mutbl == Mutability::Mut {
- // Ignore `&mut Box<T>` types; see issue #2907 for
- // details.
- return;
- }
-
- // When trait objects or opaque types have lifetime or auto-trait bounds,
- // we need to add parentheses to avoid a syntax error due to its ambiguity.
- // Originally reported as the issue #3128.
- let inner_snippet = snippet(cx, inner.span, "..");
- let suggestion = match &inner.kind {
- TyKind::TraitObject(bounds, lt_bound) if bounds.len() > 1 || !lt_bound.is_elided() => {
- format!("&{}({})", ltopt, &inner_snippet)
- },
- TyKind::Path(qpath)
- if get_bounds_if_impl_trait(cx, qpath, inner.hir_id)
- .map_or(false, |bounds| bounds.len() > 1) =>
- {
- format!("&{}({})", ltopt, &inner_snippet)
- },
- _ => format!("&{}{}", ltopt, &inner_snippet),
- };
- span_lint_and_sugg(
- cx,
- BORROWED_BOX,
- hir_ty.span,
- "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
- "try",
- suggestion,
- // To make this `MachineApplicable`, at least one needs to check if it isn't a trait item
- // because the trait impls of it will break otherwise;
- // and there may be other cases that result in invalid code.
- // For example, type coercion doesn't work nicely.
- Applicability::Unspecified,
- );
- return; // don't recurse into the type
- }
- };
- self.check_ty(cx, &mut_ty.ty, is_local);
- },
- _ => self.check_ty(cx, &mut_ty.ty, is_local),
- }
- }
-}
-
-// Returns true if given type is `Any` trait.
-fn is_any_trait(t: &hir::Ty<'_>) -> bool {
- if_chain! {
- if let TyKind::TraitObject(ref traits, _) = t.kind;
- if !traits.is_empty();
- // Only Send/Sync can be used as additional traits, so it is enough to
- // check only the first trait.
- if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
- then {
- return true;
- }
- }
-
- false
-}
-
-fn get_bounds_if_impl_trait<'tcx>(cx: &LateContext<'tcx>, qpath: &QPath<'_>, id: HirId) -> Option<GenericBounds<'tcx>> {
- if_chain! {
- if let Some(did) = cx.qpath_res(qpath, id).opt_def_id();
- if let Some(Node::GenericParam(generic_param)) = cx.tcx.hir().get_if_local(did);
- if let GenericParamKind::Type { synthetic, .. } = generic_param.kind;
- if synthetic == Some(SyntheticTyParamKind::ImplTrait);
- then {
- Some(generic_param.bounds)
- } else {
- None
- }
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for binding a unit value.
- ///
- /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
- /// binding one is kind of pointless.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// let x = {
- /// 1;
- /// };
- /// ```
- pub LET_UNIT_VALUE,
- pedantic,
- "creating a `let` binding to a value of unit type, which usually can't be used afterwards"
-}
-
-declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
-
-impl<'tcx> LateLintPass<'tcx> for LetUnitValue {
- fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
- if let StmtKind::Local(ref local) = stmt.kind {
- if is_unit(cx.typeck_results().pat_ty(&local.pat)) {
- if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
- return;
- }
- if higher::is_from_for_desugar(local) {
- return;
- }
- span_lint_and_then(
- cx,
- LET_UNIT_VALUE,
- stmt.span,
- "this let-binding has unit value",
- |diag| {
- if let Some(expr) = &local.init {
- let snip = snippet_with_macro_callsite(cx, expr.span, "()");
- diag.span_suggestion(
- stmt.span,
- "omit the `let` binding",
- format!("{};", snip),
- Applicability::MachineApplicable, // snippet
- );
- }
- },
- );
- }
- }
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for comparisons to unit. This includes all binary
- /// comparisons (like `==` and `<`) and asserts.
- ///
- /// **Why is this bad?** Unit is always equal to itself, and thus is just a
- /// clumsily written constant. Mostly this happens when someone accidentally
- /// adds semicolons at the end of the operands.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// # fn foo() {};
- /// # fn bar() {};
- /// # fn baz() {};
- /// if {
- /// foo();
- /// } == {
- /// bar();
- /// } {
- /// baz();
- /// }
- /// ```
- /// is equal to
- /// ```rust
- /// # fn foo() {};
- /// # fn bar() {};
- /// # fn baz() {};
- /// {
- /// foo();
- /// bar();
- /// baz();
- /// }
- /// ```
- ///
- /// For asserts:
- /// ```rust
- /// # fn foo() {};
- /// # fn bar() {};
- /// assert_eq!({ foo(); }, { bar(); });
- /// ```
- /// will always succeed
- pub UNIT_CMP,
- correctness,
- "comparing unit values"
-}
-
-declare_lint_pass!(UnitCmp => [UNIT_CMP]);
-
-impl<'tcx> LateLintPass<'tcx> for UnitCmp {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
- if expr.span.from_expansion() {
- if let Some(callee) = expr.span.source_callee() {
- if let ExpnKind::Macro(MacroKind::Bang, symbol) = callee.kind {
- if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
- let op = cmp.node;
- if op.is_comparison() && is_unit(cx.typeck_results().expr_ty(left)) {
- let result = match &*symbol.as_str() {
- "assert_eq" | "debug_assert_eq" => "succeed",
- "assert_ne" | "debug_assert_ne" => "fail",
- _ => return,
- };
- span_lint(
- cx,
- UNIT_CMP,
- expr.span,
- &format!(
- "`{}` of unit values detected. This will always {}",
- symbol.as_str(),
- result
- ),
- );
- }
- }
- }
- }
- return;
- }
- if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
- let op = cmp.node;
- if op.is_comparison() && is_unit(cx.typeck_results().expr_ty(left)) {
- let result = match op {
- BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
- _ => "false",
- };
- span_lint(
- cx,
- UNIT_CMP,
- expr.span,
- &format!(
- "{}-comparison of unit values detected. This will always be {}",
- op.as_str(),
- result
- ),
- );
- }
- }
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for passing a unit value as an argument to a function without using a
- /// unit literal (`()`).
- ///
- /// **Why is this bad?** This is likely the result of an accidental semicolon.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust,ignore
- /// foo({
- /// let a = bar();
- /// baz(a);
- /// })
- /// ```
- pub UNIT_ARG,
- complexity,
- "passing unit to a function"
-}
-
-declare_lint_pass!(UnitArg => [UNIT_ARG]);
-
-impl<'tcx> LateLintPass<'tcx> for UnitArg {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- if expr.span.from_expansion() {
- return;
- }
-
- // apparently stuff in the desugaring of `?` can trigger this
- // so check for that here
- // only the calls to `Try::from_error` is marked as desugared,
- // so we need to check both the current Expr and its parent.
- if is_questionmark_desugar_marked_call(expr) {
- return;
- }
- if_chain! {
- let map = &cx.tcx.hir();
- let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
- if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
- if is_questionmark_desugar_marked_call(parent_expr);
- then {
- return;
- }
- }
-
- match expr.kind {
- ExprKind::Call(_, args) | ExprKind::MethodCall(_, _, args, _) => {
- let args_to_recover = args
- .iter()
- .filter(|arg| {
- if is_unit(cx.typeck_results().expr_ty(arg)) && !is_unit_literal(arg) {
- !matches!(
- &arg.kind,
- ExprKind::Match(.., MatchSource::TryDesugar) | ExprKind::Path(..)
- )
- } else {
- false
- }
- })
- .collect::<Vec<_>>();
- if !args_to_recover.is_empty() {
- lint_unit_args(cx, expr, &args_to_recover);
- }
- },
- _ => (),
- }
- }
-}
-
-fn fmt_stmts_and_call(
- cx: &LateContext<'_>,
- call_expr: &Expr<'_>,
- call_snippet: &str,
- args_snippets: &[impl AsRef<str>],
- non_empty_block_args_snippets: &[impl AsRef<str>],
-) -> String {
- let call_expr_indent = indent_of(cx, call_expr.span).unwrap_or(0);
- let call_snippet_with_replacements = args_snippets
- .iter()
- .fold(call_snippet.to_owned(), |acc, arg| acc.replacen(arg.as_ref(), "()", 1));
-
- let mut stmts_and_call = non_empty_block_args_snippets
- .iter()
- .map(|it| it.as_ref().to_owned())
- .collect::<Vec<_>>();
- stmts_and_call.push(call_snippet_with_replacements);
- stmts_and_call = stmts_and_call
- .into_iter()
- .map(|v| reindent_multiline(v.into(), true, Some(call_expr_indent)).into_owned())
- .collect();
-
- let mut stmts_and_call_snippet = stmts_and_call.join(&format!("{}{}", ";\n", " ".repeat(call_expr_indent)));
- // expr is not in a block statement or result expression position, wrap in a block
- let parent_node = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(call_expr.hir_id));
- if !matches!(parent_node, Some(Node::Block(_))) && !matches!(parent_node, Some(Node::Stmt(_))) {
- let block_indent = call_expr_indent + 4;
- stmts_and_call_snippet =
- reindent_multiline(stmts_and_call_snippet.into(), true, Some(block_indent)).into_owned();
- stmts_and_call_snippet = format!(
- "{{\n{}{}\n{}}}",
- " ".repeat(block_indent),
- &stmts_and_call_snippet,
- " ".repeat(call_expr_indent)
- );
- }
- stmts_and_call_snippet
-}
-
-fn lint_unit_args(cx: &LateContext<'_>, expr: &Expr<'_>, args_to_recover: &[&Expr<'_>]) {
- let mut applicability = Applicability::MachineApplicable;
- let (singular, plural) = if args_to_recover.len() > 1 {
- ("", "s")
- } else {
- ("a ", "")
- };
- span_lint_and_then(
- cx,
- UNIT_ARG,
- expr.span,
- &format!("passing {}unit value{} to a function", singular, plural),
- |db| {
- let mut or = "";
- args_to_recover
- .iter()
- .filter_map(|arg| {
- if_chain! {
- if let ExprKind::Block(block, _) = arg.kind;
- if block.expr.is_none();
- if let Some(last_stmt) = block.stmts.iter().last();
- if let StmtKind::Semi(last_expr) = last_stmt.kind;
- if let Some(snip) = snippet_opt(cx, last_expr.span);
- then {
- Some((
- last_stmt.span,
- snip,
- ))
- }
- else {
- None
- }
- }
- })
- .for_each(|(span, sugg)| {
- db.span_suggestion(
- span,
- "remove the semicolon from the last statement in the block",
- sugg,
- Applicability::MaybeIncorrect,
- );
- or = "or ";
- applicability = Applicability::MaybeIncorrect;
- });
-
- let arg_snippets: Vec<String> = args_to_recover
- .iter()
- .filter_map(|arg| snippet_opt(cx, arg.span))
- .collect();
- let arg_snippets_without_empty_blocks: Vec<String> = args_to_recover
- .iter()
- .filter(|arg| !is_empty_block(arg))
- .filter_map(|arg| snippet_opt(cx, arg.span))
- .collect();
-
- if let Some(call_snippet) = snippet_opt(cx, expr.span) {
- let sugg = fmt_stmts_and_call(
- cx,
- expr,
- &call_snippet,
- &arg_snippets,
- &arg_snippets_without_empty_blocks,
- );
-
- if arg_snippets_without_empty_blocks.is_empty() {
- db.multipart_suggestion(
- &format!("use {}unit literal{} instead", singular, plural),
- args_to_recover
- .iter()
- .map(|arg| (arg.span, "()".to_string()))
- .collect::<Vec<_>>(),
- applicability,
- );
- } else {
- let plural = arg_snippets_without_empty_blocks.len() > 1;
- let empty_or_s = if plural { "s" } else { "" };
- let it_or_them = if plural { "them" } else { "it" };
- db.span_suggestion(
- expr.span,
- &format!(
- "{}move the expression{} in front of the call and replace {} with the unit literal `()`",
- or, empty_or_s, it_or_them
- ),
- sugg,
- applicability,
- );
- }
- }
- },
- );
-}
-
-fn is_empty_block(expr: &Expr<'_>) -> bool {
- matches!(
- expr.kind,
- ExprKind::Block(
- Block {
- stmts: &[],
- expr: None,
- ..
- },
- _,
- )
- )
-}
-
-fn is_questionmark_desugar_marked_call(expr: &Expr<'_>) -> bool {
- use rustc_span::hygiene::DesugaringKind;
- if let ExprKind::Call(ref callee, _) = expr.kind {
- callee.span.is_desugaring(DesugaringKind::QuestionMark)
- } else {
- false
- }
-}
-
-fn is_unit(ty: Ty<'_>) -> bool {
- matches!(ty.kind(), ty::Tuple(slice) if slice.is_empty())
-}
-
-fn is_unit_literal(expr: &Expr<'_>) -> bool {
- matches!(expr.kind, ExprKind::Tup(ref slice) if slice.is_empty())
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts from any numerical to a float type where
- /// the receiving type cannot store all values from the original type without
- /// rounding errors. This possible rounding is to be expected, so this lint is
- /// `Allow` by default.
- ///
- /// Basically, this warns on casting any integer with 32 or more bits to `f32`
- /// or any 64-bit integer to `f64`.
- ///
- /// **Why is this bad?** It's not bad at all. But in some applications it can be
- /// helpful to know where precision loss can take place. This lint can help find
- /// those places in the code.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// let x = u64::MAX;
- /// x as f64;
- /// ```
- pub CAST_PRECISION_LOSS,
- pedantic,
- "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts from a signed to an unsigned numerical
- /// type. In this case, negative values wrap around to large positive values,
- /// which can be quite surprising in practice. However, as the cast works as
- /// defined, this lint is `Allow` by default.
- ///
- /// **Why is this bad?** Possibly surprising results. You can activate this lint
- /// as a one-time check to see where numerical wrapping can arise.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// let y: i8 = -1;
- /// y as u128; // will return 18446744073709551615
- /// ```
- pub CAST_SIGN_LOSS,
- pedantic,
- "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts between numerical types that may
- /// truncate large values. This is expected behavior, so the cast is `Allow` by
- /// default.
- ///
- /// **Why is this bad?** In some problem domains, it is good practice to avoid
- /// truncation. This lint can be activated to help assess where additional
- /// checks could be beneficial.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// fn as_u8(x: u64) -> u8 {
- /// x as u8
- /// }
- /// ```
- pub CAST_POSSIBLE_TRUNCATION,
- pedantic,
- "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts from an unsigned type to a signed type of
- /// the same size. Performing such a cast is a 'no-op' for the compiler,
- /// i.e., nothing is changed at the bit level, and the binary representation of
- /// the value is reinterpreted. This can cause wrapping if the value is too big
- /// for the target signed type. However, the cast works as defined, so this lint
- /// is `Allow` by default.
- ///
- /// **Why is this bad?** While such a cast is not bad in itself, the results can
- /// be surprising when this is not the intended behavior, as demonstrated by the
- /// example below.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// u32::MAX as i32; // will yield a value of `-1`
- /// ```
- pub CAST_POSSIBLE_WRAP,
- pedantic,
- "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts between numerical types that may
- /// be replaced by safe conversion functions.
- ///
- /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
- /// conversions, including silently lossy conversions. Conversion functions such
- /// as `i32::from` will only perform lossless conversions. Using the conversion
- /// functions prevents conversions from turning into silent lossy conversions if
- /// the types of the input expressions ever change, and make it easier for
- /// people reading the code to know that the conversion is lossless.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// fn as_u64(x: u8) -> u64 {
- /// x as u64
- /// }
- /// ```
- ///
- /// Using `::from` would look like this:
- ///
- /// ```rust
- /// fn as_u64(x: u8) -> u64 {
- /// u64::from(x)
- /// }
- /// ```
- pub CAST_LOSSLESS,
- pedantic,
- "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts to the same type, casts of int literals to integer types
- /// and casts of float literals to float types.
- ///
- /// **Why is this bad?** It's just unnecessary.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// let _ = 2i32 as i32;
- /// let _ = 0.5 as f32;
- /// ```
- ///
- /// Better:
- ///
- /// ```rust
- /// let _ = 2_i32;
- /// let _ = 0.5_f32;
- /// ```
- pub UNNECESSARY_CAST,
- complexity,
- "cast to the same type, e.g., `x as i32` where `x: i32`"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts, using `as` or `pointer::cast`,
- /// from a less-strictly-aligned pointer to a more-strictly-aligned pointer
- ///
- /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
- /// behavior.
- ///
- /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
- /// on the resulting pointer is fine. Is over-zealous: Casts with manual alignment checks or casts like
- /// u64-> u8 -> u16 can be fine. Miri is able to do a more in-depth analysis.
- ///
- /// **Example:**
- /// ```rust
- /// let _ = (&1u8 as *const u8) as *const u16;
- /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
- ///
- /// (&1u8 as *const u8).cast::<u16>();
- /// (&mut 1u8 as *mut u8).cast::<u16>();
- /// ```
- pub CAST_PTR_ALIGNMENT,
- pedantic,
- "cast from a pointer to a more-strictly-aligned pointer"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts of function pointers to something other than usize
- ///
- /// **Why is this bad?**
- /// Casting a function pointer to anything other than usize/isize is not portable across
- /// architectures, because you end up losing bits if the target type is too small or end up with a
- /// bunch of extra bits that waste space and add more instructions to the final binary than
- /// strictly necessary for the problem
- ///
- /// Casting to isize also doesn't make sense since there are no signed addresses.
- ///
- /// **Example**
- ///
- /// ```rust
- /// // Bad
- /// fn fun() -> i32 { 1 }
- /// let a = fun as i64;
- ///
- /// // Good
- /// fn fun2() -> i32 { 1 }
- /// let a = fun2 as usize;
- /// ```
- pub FN_TO_NUMERIC_CAST,
- style,
- "casting a function pointer to a numeric type other than usize"
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
- /// store address.
- ///
- /// **Why is this bad?**
- /// Such a cast discards some bits of the function's address. If this is intended, it would be more
- /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
- /// a comment) to perform the truncation.
- ///
- /// **Example**
- ///
- /// ```rust
- /// // Bad
- /// fn fn1() -> i16 {
- /// 1
- /// };
- /// let _ = fn1 as i32;
- ///
- /// // Better: Cast to usize first, then comment with the reason for the truncation
- /// fn fn2() -> i16 {
- /// 1
- /// };
- /// let fn_ptr = fn2 as usize;
- /// let fn_ptr_truncated = fn_ptr as i32;
- /// ```
- pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
- style,
- "casting a function pointer to a numeric type not wide enough to store the address"
-}
-
-/// Returns the size in bits of an integral type.
-/// Will return 0 if the type is not an int or uint variant
-fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
- match typ.kind() {
- ty::Int(i) => match i {
- IntTy::Isize => tcx.data_layout.pointer_size.bits(),
- IntTy::I8 => 8,
- IntTy::I16 => 16,
- IntTy::I32 => 32,
- IntTy::I64 => 64,
- IntTy::I128 => 128,
- },
- ty::Uint(i) => match i {
- UintTy::Usize => tcx.data_layout.pointer_size.bits(),
- UintTy::U8 => 8,
- UintTy::U16 => 16,
- UintTy::U32 => 32,
- UintTy::U64 => 64,
- UintTy::U128 => 128,
- },
- _ => 0,
- }
-}
-
-fn is_isize_or_usize(typ: Ty<'_>) -> bool {
- matches!(typ.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
-}
-
-fn span_precision_loss_lint(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to_f64: bool) {
- let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
- let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
- let arch_dependent_str = "on targets with 64-bit wide pointers ";
- let from_nbits_str = if arch_dependent {
- "64".to_owned()
- } else if is_isize_or_usize(cast_from) {
- "32 or 64".to_owned()
- } else {
- int_ty_to_nbits(cast_from, cx.tcx).to_string()
- };
- span_lint(
- cx,
- CAST_PRECISION_LOSS,
- expr.span,
- &format!(
- "casting `{0}` to `{1}` causes a loss of precision {2}(`{0}` is {3} bits wide, \
- but `{1}`'s mantissa is only {4} bits wide)",
- cast_from,
- if cast_to_f64 { "f64" } else { "f32" },
- if arch_dependent { arch_dependent_str } else { "" },
- from_nbits_str,
- mantissa_nbits
- ),
- );
-}
-
-fn should_strip_parens(op: &Expr<'_>, snip: &str) -> bool {
- if let ExprKind::Binary(_, _, _) = op.kind {
- if snip.starts_with('(') && snip.ends_with(')') {
- return true;
- }
- }
- false
-}
-
-fn span_lossless_lint(cx: &LateContext<'_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
- // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
- if in_constant(cx, expr.hir_id) {
- return;
- }
- // The suggestion is to use a function call, so if the original expression
- // has parens on the outside, they are no longer needed.
- let mut applicability = Applicability::MachineApplicable;
- let opt = snippet_opt(cx, op.span);
- let sugg = opt.as_ref().map_or_else(
- || {
- applicability = Applicability::HasPlaceholders;
- ".."
- },
- |snip| {
- if should_strip_parens(op, snip) {
- &snip[1..snip.len() - 1]
- } else {
- snip.as_str()
- }
- },
- );
-
- span_lint_and_sugg(
- cx,
- CAST_LOSSLESS,
- expr.span,
- &format!(
- "casting `{}` to `{}` may become silently lossy if you later change the type",
- cast_from, cast_to
- ),
- "try",
- format!("{}::from({})", cast_to, sugg),
- applicability,
- );
-}
-
-enum ArchSuffix {
- _32,
- _64,
- None,
-}
-
-fn check_loss_of_sign(cx: &LateContext<'_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
- if !cast_from.is_signed() || cast_to.is_signed() {
- return;
- }
-
- // don't lint for positive constants
- let const_val = constant(cx, &cx.typeck_results(), op);
- if_chain! {
- if let Some((Constant::Int(n), _)) = const_val;
- if let ty::Int(ity) = *cast_from.kind();
- if sext(cx.tcx, n, ity) >= 0;
- then {
- return
- }
- }
-
- // don't lint for the result of methods that always return non-negative values
- if let ExprKind::MethodCall(ref path, _, _, _) = op.kind {
- let mut method_name = path.ident.name.as_str();
- let allowed_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
-
- if_chain! {
- if method_name == "unwrap";
- if let Some(arglist) = method_chain_args(op, &["unwrap"]);
- if let ExprKind::MethodCall(ref inner_path, _, _, _) = &arglist[0][0].kind;
- then {
- method_name = inner_path.ident.name.as_str();
- }
- }
-
- if allowed_methods.iter().any(|&name| method_name == name) {
- return;
- }
- }
-
- span_lint(
- cx,
- CAST_SIGN_LOSS,
- expr.span,
- &format!(
- "casting `{}` to `{}` may lose the sign of the value",
- cast_from, cast_to
- ),
- );
-}
-
-fn check_truncation_and_wrapping(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
- let arch_64_suffix = " on targets with 64-bit wide pointers";
- let arch_32_suffix = " on targets with 32-bit wide pointers";
- let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
- let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
- let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
- let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
- match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
- (true, true) | (false, false) => (
- to_nbits < from_nbits,
- ArchSuffix::None,
- to_nbits == from_nbits && cast_unsigned_to_signed,
- ArchSuffix::None,
- ),
- (true, false) => (
- to_nbits <= 32,
- if to_nbits == 32 {
- ArchSuffix::_64
- } else {
- ArchSuffix::None
- },
- to_nbits <= 32 && cast_unsigned_to_signed,
- ArchSuffix::_32,
- ),
- (false, true) => (
- from_nbits == 64,
- ArchSuffix::_32,
- cast_unsigned_to_signed,
- if from_nbits == 64 {
- ArchSuffix::_64
- } else {
- ArchSuffix::_32
- },
- ),
- };
- if span_truncation {
- span_lint(
- cx,
- CAST_POSSIBLE_TRUNCATION,
- expr.span,
- &format!(
- "casting `{}` to `{}` may truncate the value{}",
- cast_from,
- cast_to,
- match suffix_truncation {
- ArchSuffix::_32 => arch_32_suffix,
- ArchSuffix::_64 => arch_64_suffix,
- ArchSuffix::None => "",
- }
- ),
- );
- }
- if span_wrap {
- span_lint(
- cx,
- CAST_POSSIBLE_WRAP,
- expr.span,
- &format!(
- "casting `{}` to `{}` may wrap around the value{}",
- cast_from,
- cast_to,
- match suffix_wrap {
- ArchSuffix::_32 => arch_32_suffix,
- ArchSuffix::_64 => arch_64_suffix,
- ArchSuffix::None => "",
- }
- ),
- );
- }
-}
-
-fn check_lossless(cx: &LateContext<'_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
- let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
- let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
- let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
- if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
- {
- span_lossless_lint(cx, expr, op, cast_from, cast_to);
- }
-}
-
-declare_lint_pass!(Casts => [
- CAST_PRECISION_LOSS,
- CAST_SIGN_LOSS,
- CAST_POSSIBLE_TRUNCATION,
- CAST_POSSIBLE_WRAP,
- CAST_LOSSLESS,
- UNNECESSARY_CAST,
- CAST_PTR_ALIGNMENT,
- FN_TO_NUMERIC_CAST,
- FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
-]);
-
-// Check if the given type is either `core::ffi::c_void` or
-// one of the platform specific `libc::<platform>::c_void` of libc.
-fn is_c_void(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
- if let ty::Adt(adt, _) = ty.kind() {
- let names = cx.get_def_path(adt.did);
-
- if names.is_empty() {
- return false;
- }
- if names[0] == sym::libc || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
- return true;
- }
- }
- false
-}
-
-/// Returns the mantissa bits wide of a fp type.
-/// Will return 0 if the type is not a fp
-fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
- match typ.kind() {
- ty::Float(FloatTy::F32) => 23,
- ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
- _ => 0,
- }
-}
-
-impl<'tcx> LateLintPass<'tcx> for Casts {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- if expr.span.from_expansion() {
- return;
- }
- if let ExprKind::Cast(ref ex, cast_to) = expr.kind {
- if is_hir_ty_cfg_dependant(cx, cast_to) {
- return;
- }
- let (cast_from, cast_to) = (cx.typeck_results().expr_ty(ex), cx.typeck_results().expr_ty(expr));
- lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
- if let Some(lit) = get_numeric_literal(ex) {
- let literal_str = snippet_opt(cx, ex.span).unwrap_or_default();
-
- if_chain! {
- if let LitKind::Int(n, _) = lit.node;
- if let Some(src) = snippet_opt(cx, lit.span);
- if cast_to.is_floating_point();
- if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node);
- let from_nbits = 128 - n.leading_zeros();
- let to_nbits = fp_ty_mantissa_nbits(cast_to);
- if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits && num_lit.is_decimal();
- then {
- let literal_str = if is_unary_neg(ex) { format!("-{}", num_lit.integer) } else { num_lit.integer.into() };
- show_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
- return;
- }
- }
-
- match lit.node {
- LitKind::Int(_, LitIntType::Unsuffixed) if cast_to.is_integral() => {
- show_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
- },
- LitKind::Float(_, LitFloatType::Unsuffixed) if cast_to.is_floating_point() => {
- show_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
- },
- LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
- _ => {
- if cast_from.kind() == cast_to.kind() && !in_external_macro(cx.sess(), expr.span) {
- span_lint(
- cx,
- UNNECESSARY_CAST,
- expr.span,
- &format!(
- "casting to the same type is unnecessary (`{}` -> `{}`)",
- cast_from, cast_to
- ),
- );
- }
- },
- }
- }
- if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
- lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
- }
-
- lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
- } else if let ExprKind::MethodCall(method_path, _, args, _) = expr.kind {
- if_chain! {
- if method_path.ident.name == sym!(cast);
- if let Some(generic_args) = method_path.args;
- if let [GenericArg::Type(cast_to)] = generic_args.args;
- // There probably is no obvious reason to do this, just to be consistent with `as` cases.
- if !is_hir_ty_cfg_dependant(cx, cast_to);
- then {
- let (cast_from, cast_to) =
- (cx.typeck_results().expr_ty(&args[0]), cx.typeck_results().expr_ty(expr));
- lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
- }
- }
- }
- }
-}
-
-fn is_unary_neg(expr: &Expr<'_>) -> bool {
- matches!(expr.kind, ExprKind::Unary(UnOp::Neg, _))
-}
-
-fn get_numeric_literal<'e>(expr: &'e Expr<'e>) -> Option<&'e Lit> {
- match expr.kind {
- ExprKind::Lit(ref lit) => Some(lit),
- ExprKind::Unary(UnOp::Neg, e) => {
- if let ExprKind::Lit(ref lit) = e.kind {
- Some(lit)
- } else {
- None
- }
- },
- _ => None,
- }
-}
-
-fn show_unnecessary_cast(cx: &LateContext<'_>, expr: &Expr<'_>, literal_str: &str, cast_from: Ty<'_>, cast_to: Ty<'_>) {
- let literal_kind_name = if cast_from.is_integral() { "integer" } else { "float" };
- span_lint_and_sugg(
- cx,
- UNNECESSARY_CAST,
- expr.span,
- &format!("casting {} literal to `{}` is unnecessary", literal_kind_name, cast_to),
- "try",
- format!("{}_{}", literal_str.trim_end_matches('.'), cast_to),
- Applicability::MachineApplicable,
- );
-}
-
-fn lint_numeric_casts<'tcx>(
- cx: &LateContext<'tcx>,
- expr: &Expr<'tcx>,
- cast_expr: &Expr<'_>,
- cast_from: Ty<'tcx>,
- cast_to: Ty<'tcx>,
-) {
- match (cast_from.is_integral(), cast_to.is_integral()) {
- (true, false) => {
- let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
- let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind() {
- 32
- } else {
- 64
- };
- if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
- span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
- }
- if from_nbits < to_nbits {
- span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
- }
- },
- (false, true) => {
- span_lint(
- cx,
- CAST_POSSIBLE_TRUNCATION,
- expr.span,
- &format!("casting `{}` to `{}` may truncate the value", cast_from, cast_to),
- );
- if !cast_to.is_signed() {
- span_lint(
- cx,
- CAST_SIGN_LOSS,
- expr.span,
- &format!(
- "casting `{}` to `{}` may lose the sign of the value",
- cast_from, cast_to
- ),
- );
- }
- },
- (true, true) => {
- check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
- check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
- check_lossless(cx, expr, cast_expr, cast_from, cast_to);
- },
- (false, false) => {
- if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.kind(), &cast_to.kind()) {
- span_lint(
- cx,
- CAST_POSSIBLE_TRUNCATION,
- expr.span,
- "casting `f64` to `f32` may truncate the value",
- );
- }
- if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.kind(), &cast_to.kind()) {
- span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
- }
- },
- }
-}
-
-fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
- if_chain! {
- if let ty::RawPtr(from_ptr_ty) = &cast_from.kind();
- if let ty::RawPtr(to_ptr_ty) = &cast_to.kind();
- if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
- if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
- if from_layout.align.abi < to_layout.align.abi;
- // with c_void, we inherently need to trust the user
- if !is_c_void(cx, from_ptr_ty.ty);
- // when casting from a ZST, we don't know enough to properly lint
- if !from_layout.is_zst();
- then {
- span_lint(
- cx,
- CAST_PTR_ALIGNMENT,
- expr.span,
- &format!(
- "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
- cast_from,
- cast_to,
- from_layout.align.abi.bytes(),
- to_layout.align.abi.bytes(),
- ),
- );
- }
- }
-}
-
-fn lint_fn_to_numeric_cast(
- cx: &LateContext<'_>,
- expr: &Expr<'_>,
- cast_expr: &Expr<'_>,
- cast_from: Ty<'_>,
- cast_to: Ty<'_>,
-) {
- // We only want to check casts to `ty::Uint` or `ty::Int`
- match cast_to.kind() {
- ty::Uint(_) | ty::Int(..) => { /* continue on */ },
- _ => return,
- }
- match cast_from.kind() {
- ty::FnDef(..) | ty::FnPtr(_) => {
- let mut applicability = Applicability::MaybeIncorrect;
- let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
-
- let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
- if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
- span_lint_and_sugg(
- cx,
- FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
- expr.span,
- &format!(
- "casting function pointer `{}` to `{}`, which truncates the value",
- from_snippet, cast_to
- ),
- "try",
- format!("{} as usize", from_snippet),
- applicability,
- );
- } else if *cast_to.kind() != ty::Uint(UintTy::Usize) {
- span_lint_and_sugg(
- cx,
- FN_TO_NUMERIC_CAST,
- expr.span,
- &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
- "try",
- format!("{} as usize", from_snippet),
- applicability,
- );
- }
- },
- _ => {},
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for types used in structs, parameters and `let`
- /// declarations above a certain complexity threshold.
- ///
- /// **Why is this bad?** Too complex types make the code less readable. Consider
- /// using a `type` definition to simplify them.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust
- /// # use std::rc::Rc;
- /// struct Foo {
- /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
- /// }
- /// ```
- pub TYPE_COMPLEXITY,
- complexity,
- "usage of very complex types that might be better factored into `type` definitions"
-}
-
-pub struct TypeComplexity {
- threshold: u64,
-}
-
-impl TypeComplexity {
- #[must_use]
- pub fn new(threshold: u64) -> Self {
- Self { threshold }
- }
-}
-
-impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
-
-impl<'tcx> LateLintPass<'tcx> for TypeComplexity {
- fn check_fn(
- &mut self,
- cx: &LateContext<'tcx>,
- _: FnKind<'tcx>,
- decl: &'tcx FnDecl<'_>,
- _: &'tcx Body<'_>,
- _: Span,
- _: HirId,
- ) {
- self.check_fndecl(cx, decl);
- }
-
- fn check_struct_field(&mut self, cx: &LateContext<'tcx>, field: &'tcx hir::StructField<'_>) {
- // enum variants are also struct fields now
- self.check_type(cx, &field.ty);
- }
-
- fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
- match item.kind {
- ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
- // functions, enums, structs, impls and traits are covered
- _ => (),
- }
- }
-
- fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
- match item.kind {
- TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
- TraitItemKind::Fn(FnSig { ref decl, .. }, TraitFn::Required(_)) => self.check_fndecl(cx, decl),
- // methods with default impl are covered by check_fn
- _ => (),
- }
- }
-
- fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
- match item.kind {
- ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
- // methods are covered by check_fn
- _ => (),
- }
- }
-
- fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
- if let Some(ref ty) = local.ty {
- self.check_type(cx, ty);
- }
- }
-}
-
-impl<'tcx> TypeComplexity {
- fn check_fndecl(&self, cx: &LateContext<'tcx>, decl: &'tcx FnDecl<'_>) {
- for arg in decl.inputs {
- self.check_type(cx, arg);
- }
- if let FnRetTy::Return(ref ty) = decl.output {
- self.check_type(cx, ty);
- }
- }
-
- fn check_type(&self, cx: &LateContext<'_>, ty: &hir::Ty<'_>) {
- if ty.span.from_expansion() {
- return;
- }
- let score = {
- let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
- visitor.visit_ty(ty);
- visitor.score
- };
-
- if score > self.threshold {
- span_lint(
- cx,
- TYPE_COMPLEXITY,
- ty.span,
- "very complex type used. Consider factoring parts into `type` definitions",
- );
- }
- }
-}
-
-/// Walks a type and assigns a complexity score to it.
-struct TypeComplexityVisitor {
- /// total complexity score of the type
- score: u64,
- /// current nesting level
- nest: u64,
-}
-
-impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
- type Map = Map<'tcx>;
-
- fn visit_ty(&mut self, ty: &'tcx hir::Ty<'_>) {
- let (add_score, sub_nest) = match ty.kind {
- // _, &x and *x have only small overhead; don't mess with nesting level
- TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
-
- // the "normal" components of a type: named types, arrays/tuples
- TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
-
- // function types bring a lot of overhead
- TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
-
- TyKind::TraitObject(ref param_bounds, _) => {
- let has_lifetime_parameters = param_bounds.iter().any(|bound| {
- bound
- .bound_generic_params
- .iter()
- .any(|gen| matches!(gen.kind, GenericParamKind::Lifetime { .. }))
- });
- if has_lifetime_parameters {
- // complex trait bounds like A<'a, 'b>
- (50 * self.nest, 1)
- } else {
- // simple trait bounds like A + B
- (20 * self.nest, 0)
- }
- },
-
- _ => (0, 0),
- };
- self.score += add_score;
- self.nest += sub_nest;
- walk_ty(self, ty);
- self.nest -= sub_nest;
- }
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for expressions where a character literal is cast
- /// to `u8` and suggests using a byte literal instead.
- ///
- /// **Why is this bad?** In general, casting values to smaller types is
- /// error-prone and should be avoided where possible. In the particular case of
- /// converting a character literal to u8, it is easy to avoid by just using a
- /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
- /// than `'a' as u8`.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust,ignore
- /// 'x' as u8
- /// ```
- ///
- /// A better version, using the byte literal:
- ///
- /// ```rust,ignore
- /// b'x'
- /// ```
- pub CHAR_LIT_AS_U8,
- complexity,
- "casting a character literal to `u8` truncates"
-}
-
-declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
-
-impl<'tcx> LateLintPass<'tcx> for CharLitAsU8 {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- if_chain! {
- if !expr.span.from_expansion();
- if let ExprKind::Cast(e, _) = &expr.kind;
- if let ExprKind::Lit(l) = &e.kind;
- if let LitKind::Char(c) = l.node;
- if ty::Uint(UintTy::U8) == *cx.typeck_results().expr_ty(expr).kind();
- then {
- let mut applicability = Applicability::MachineApplicable;
- let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
-
- span_lint_and_then(
- cx,
- CHAR_LIT_AS_U8,
- expr.span,
- "casting a character literal to `u8` truncates",
- |diag| {
- diag.note("`char` is four bytes wide, but `u8` is a single byte");
-
- if c.is_ascii() {
- diag.span_suggestion(
- expr.span,
- "use a byte literal instead",
- format!("b{}", snippet),
- applicability,
- );
- }
- });
- }
- }
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for comparisons where one side of the relation is
- /// either the minimum or maximum value for its type and warns if it involves a
- /// case that is always true or always false. Only integer and boolean types are
- /// checked.
- ///
- /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
- /// that it is possible for `x` to be less than the minimum. Expressions like
- /// `max < x` are probably mistakes.
- ///
- /// **Known problems:** For `usize` the size of the current compile target will
- /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
- /// a comparison to detect target pointer width will trigger this lint. One can
- /// use `mem::sizeof` and compare its value or conditional compilation
- /// attributes
- /// like `#[cfg(target_pointer_width = "64")] ..` instead.
- ///
- /// **Example:**
- ///
- /// ```rust
- /// let vec: Vec<isize> = Vec::new();
- /// if vec.len() <= 0 {}
- /// if 100 > i32::MAX {}
- /// ```
- pub ABSURD_EXTREME_COMPARISONS,
- correctness,
- "a comparison with a maximum or minimum value that is always true or false"
-}
-
-declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
-
-enum ExtremeType {
- Minimum,
- Maximum,
-}
-
-struct ExtremeExpr<'a> {
- which: ExtremeType,
- expr: &'a Expr<'a>,
-}
-
-enum AbsurdComparisonResult {
- AlwaysFalse,
- AlwaysTrue,
- InequalityImpossible,
-}
-
-fn is_cast_between_fixed_and_target<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
- if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
- let precast_ty = cx.typeck_results().expr_ty(cast_exp);
- let cast_ty = cx.typeck_results().expr_ty(expr);
-
- return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
- }
-
- false
-}
-
-fn detect_absurd_comparison<'tcx>(
- cx: &LateContext<'tcx>,
- op: BinOpKind,
- lhs: &'tcx Expr<'_>,
- rhs: &'tcx Expr<'_>,
-) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
- use crate::types::AbsurdComparisonResult::{AlwaysFalse, AlwaysTrue, InequalityImpossible};
- use crate::types::ExtremeType::{Maximum, Minimum};
- use crate::utils::comparisons::{normalize_comparison, Rel};
-
- // absurd comparison only makes sense on primitive types
- // primitive types don't implement comparison operators with each other
- if cx.typeck_results().expr_ty(lhs) != cx.typeck_results().expr_ty(rhs) {
- return None;
- }
-
- // comparisons between fix sized types and target sized types are considered unanalyzable
- if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
- return None;
- }
-
- let (rel, normalized_lhs, normalized_rhs) = normalize_comparison(op, lhs, rhs)?;
-
- let lx = detect_extreme_expr(cx, normalized_lhs);
- let rx = detect_extreme_expr(cx, normalized_rhs);
-
- Some(match rel {
- Rel::Lt => {
- match (lx, rx) {
- (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
- (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
- _ => return None,
- }
- },
- Rel::Le => {
- match (lx, rx) {
- (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
- (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
- (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
- (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
- _ => return None,
- }
- },
- Rel::Ne | Rel::Eq => return None,
- })
-}
-
-fn detect_extreme_expr<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<ExtremeExpr<'tcx>> {
- use crate::types::ExtremeType::{Maximum, Minimum};
-
- let ty = cx.typeck_results().expr_ty(expr);
-
- let cv = constant(cx, cx.typeck_results(), expr)?.0;
-
- let which = match (ty.kind(), cv) {
- (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
- (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::MIN >> (128 - int_bits(cx.tcx, ity)), ity) => {
- Minimum
- },
-
- (&ty::Bool, Constant::Bool(true)) => Maximum,
- (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::MAX >> (128 - int_bits(cx.tcx, ity)), ity) => {
- Maximum
- },
- (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::MAX, uty) == i => Maximum,
-
- _ => return None,
- };
- Some(ExtremeExpr { which, expr })
-}
-
-impl<'tcx> LateLintPass<'tcx> for AbsurdExtremeComparisons {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- use crate::types::AbsurdComparisonResult::{AlwaysFalse, AlwaysTrue, InequalityImpossible};
- use crate::types::ExtremeType::{Maximum, Minimum};
-
- if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
- if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
- if !expr.span.from_expansion() {
- let msg = "this comparison involving the minimum or maximum element for this \
- type contains a case that is always true or always false";
-
- let conclusion = match result {
- AlwaysFalse => "this comparison is always false".to_owned(),
- AlwaysTrue => "this comparison is always true".to_owned(),
- InequalityImpossible => format!(
- "the case where the two sides are not equal never occurs, consider using `{} == {}` \
- instead",
- snippet(cx, lhs.span, "lhs"),
- snippet(cx, rhs.span, "rhs")
- ),
- };
-
- let help = format!(
- "because `{}` is the {} value for this type, {}",
- snippet(cx, culprit.expr.span, "x"),
- match culprit.which {
- Minimum => "minimum",
- Maximum => "maximum",
- },
- conclusion
- );
-
- span_lint_and_help(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, None, &help);
- }
- }
- }
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for comparisons where the relation is always either
- /// true or false, but where one side has been upcast so that the comparison is
- /// necessary. Only integer types are checked.
- ///
- /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
- /// will mistakenly imply that it is possible for `x` to be outside the range of
- /// `u8`.
- ///
- /// **Known problems:**
- /// https://github.com/rust-lang/rust-clippy/issues/886
- ///
- /// **Example:**
- /// ```rust
- /// let x: u8 = 1;
- /// (x as u32) > 300;
- /// ```
- pub INVALID_UPCAST_COMPARISONS,
- pedantic,
- "a comparison involving an upcast which is always true or false"
-}
-
-declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
-
-#[derive(Copy, Clone, Debug, Eq)]
-enum FullInt {
- S(i128),
- U(u128),
-}
-
-impl FullInt {
- #[allow(clippy::cast_sign_loss)]
- #[must_use]
- fn cmp_s_u(s: i128, u: u128) -> Ordering {
- if s < 0 {
- Ordering::Less
- } else if u > (i128::MAX as u128) {
- Ordering::Greater
- } else {
- (s as u128).cmp(&u)
- }
- }
-}
-
-impl PartialEq for FullInt {
- #[must_use]
- fn eq(&self, other: &Self) -> bool {
- self.partial_cmp(other).expect("`partial_cmp` only returns `Some(_)`") == Ordering::Equal
- }
-}
-
-impl PartialOrd for FullInt {
- #[must_use]
- fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
- Some(match (self, other) {
- (&Self::S(s), &Self::S(o)) => s.cmp(&o),
- (&Self::U(s), &Self::U(o)) => s.cmp(&o),
- (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
- (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
- })
- }
-}
-
-impl Ord for FullInt {
- #[must_use]
- fn cmp(&self, other: &Self) -> Ordering {
- self.partial_cmp(other)
- .expect("`partial_cmp` for FullInt can never return `None`")
- }
-}
-
-fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_>, expr: &'a Expr<'_>) -> Option<(FullInt, FullInt)> {
- if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
- let pre_cast_ty = cx.typeck_results().expr_ty(cast_exp);
- let cast_ty = cx.typeck_results().expr_ty(expr);
- // if it's a cast from i32 to u32 wrapping will invalidate all these checks
- if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
- return None;
- }
- match pre_cast_ty.kind() {
- ty::Int(int_ty) => Some(match int_ty {
- IntTy::I8 => (FullInt::S(i128::from(i8::MIN)), FullInt::S(i128::from(i8::MAX))),
- IntTy::I16 => (FullInt::S(i128::from(i16::MIN)), FullInt::S(i128::from(i16::MAX))),
- IntTy::I32 => (FullInt::S(i128::from(i32::MIN)), FullInt::S(i128::from(i32::MAX))),
- IntTy::I64 => (FullInt::S(i128::from(i64::MIN)), FullInt::S(i128::from(i64::MAX))),
- IntTy::I128 => (FullInt::S(i128::MIN), FullInt::S(i128::MAX)),
- IntTy::Isize => (FullInt::S(isize::MIN as i128), FullInt::S(isize::MAX as i128)),
- }),
- ty::Uint(uint_ty) => Some(match uint_ty {
- UintTy::U8 => (FullInt::U(u128::from(u8::MIN)), FullInt::U(u128::from(u8::MAX))),
- UintTy::U16 => (FullInt::U(u128::from(u16::MIN)), FullInt::U(u128::from(u16::MAX))),
- UintTy::U32 => (FullInt::U(u128::from(u32::MIN)), FullInt::U(u128::from(u32::MAX))),
- UintTy::U64 => (FullInt::U(u128::from(u64::MIN)), FullInt::U(u128::from(u64::MAX))),
- UintTy::U128 => (FullInt::U(u128::MIN), FullInt::U(u128::MAX)),
- UintTy::Usize => (FullInt::U(usize::MIN as u128), FullInt::U(usize::MAX as u128)),
- }),
- _ => None,
- }
- } else {
- None
- }
-}
-
-fn node_as_const_fullint<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<FullInt> {
- let val = constant(cx, cx.typeck_results(), expr)?.0;
- if let Constant::Int(const_int) = val {
- match *cx.typeck_results().expr_ty(expr).kind() {
- ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
- ty::Uint(_) => Some(FullInt::U(const_int)),
- _ => None,
- }
- } else {
- None
- }
-}
-
-fn err_upcast_comparison(cx: &LateContext<'_>, span: Span, expr: &Expr<'_>, always: bool) {
- if let ExprKind::Cast(ref cast_val, _) = expr.kind {
- span_lint(
- cx,
- INVALID_UPCAST_COMPARISONS,
- span,
- &format!(
- "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
- snippet(cx, cast_val.span, "the expression"),
- if always { "true" } else { "false" },
- ),
- );
- }
-}
-
-fn upcast_comparison_bounds_err<'tcx>(
- cx: &LateContext<'tcx>,
- span: Span,
- rel: comparisons::Rel,
- lhs_bounds: Option<(FullInt, FullInt)>,
- lhs: &'tcx Expr<'_>,
- rhs: &'tcx Expr<'_>,
- invert: bool,
-) {
- use crate::utils::comparisons::Rel;
-
- if let Some((lb, ub)) = lhs_bounds {
- if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
- if rel == Rel::Eq || rel == Rel::Ne {
- if norm_rhs_val < lb || norm_rhs_val > ub {
- err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
- }
- } else if match rel {
- Rel::Lt => {
- if invert {
- norm_rhs_val < lb
- } else {
- ub < norm_rhs_val
- }
- },
- Rel::Le => {
- if invert {
- norm_rhs_val <= lb
- } else {
- ub <= norm_rhs_val
- }
- },
- Rel::Eq | Rel::Ne => unreachable!(),
- } {
- err_upcast_comparison(cx, span, lhs, true)
- } else if match rel {
- Rel::Lt => {
- if invert {
- norm_rhs_val >= ub
- } else {
- lb >= norm_rhs_val
- }
- },
- Rel::Le => {
- if invert {
- norm_rhs_val > ub
- } else {
- lb > norm_rhs_val
- }
- },
- Rel::Eq | Rel::Ne => unreachable!(),
- } {
- err_upcast_comparison(cx, span, lhs, false)
- }
- }
- }
-}
-
-impl<'tcx> LateLintPass<'tcx> for InvalidUpcastComparisons {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
- let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
- let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
- val
- } else {
- return;
- };
-
- let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
- let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
-
- upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
- upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
- }
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for public `impl` or `fn` missing generalization
- /// over different hashers and implicitly defaulting to the default hashing
- /// algorithm (`SipHash`).
- ///
- /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
- /// used with them.
- ///
- /// **Known problems:** Suggestions for replacing constructors can contain
- /// false-positives. Also applying suggestions can require modification of other
- /// pieces of code, possibly including external crates.
- ///
- /// **Example:**
- /// ```rust
- /// # use std::collections::HashMap;
- /// # use std::hash::{Hash, BuildHasher};
- /// # trait Serialize {};
- /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
- ///
- /// pub fn foo(map: &mut HashMap<i32, i32>) { }
- /// ```
- /// could be rewritten as
- /// ```rust
- /// # use std::collections::HashMap;
- /// # use std::hash::{Hash, BuildHasher};
- /// # trait Serialize {};
- /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
- ///
- /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
- /// ```
- pub IMPLICIT_HASHER,
- pedantic,
- "missing generalization over different hashers"
-}
-
-declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
-
-impl<'tcx> LateLintPass<'tcx> for ImplicitHasher {
- #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
- fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
- use rustc_span::BytePos;
-
- fn suggestion<'tcx>(
- cx: &LateContext<'tcx>,
- diag: &mut DiagnosticBuilder<'_>,
- generics_span: Span,
- generics_suggestion_span: Span,
- target: &ImplicitHasherType<'_>,
- vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
- ) {
- let generics_snip = snippet(cx, generics_span, "");
- // trim `<` `>`
- let generics_snip = if generics_snip.is_empty() {
- ""
- } else {
- &generics_snip[1..generics_snip.len() - 1]
- };
-
- multispan_sugg(
- diag,
- "consider adding a type parameter",
- vec![
- (
- generics_suggestion_span,
- format!(
- "<{}{}S: ::std::hash::BuildHasher{}>",
- generics_snip,
- if generics_snip.is_empty() { "" } else { ", " },
- if vis.suggestions.is_empty() {
- ""
- } else {
- // request users to add `Default` bound so that generic constructors can be used
- " + Default"
- },
- ),
- ),
- (
- target.span(),
- format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
- ),
- ],
- );
-
- if !vis.suggestions.is_empty() {
- multispan_sugg(diag, "...and use generic constructor", vis.suggestions);
- }
- }
-
- if !cx.access_levels.is_exported(item.hir_id()) {
- return;
- }
-
- match item.kind {
- ItemKind::Impl(ref impl_) => {
- let mut vis = ImplicitHasherTypeVisitor::new(cx);
- vis.visit_ty(impl_.self_ty);
-
- for target in &vis.found {
- if differing_macro_contexts(item.span, target.span()) {
- return;
- }
-
- let generics_suggestion_span = impl_.generics.span.substitute_dummy({
- let pos = snippet_opt(cx, item.span.until(target.span()))
- .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
- if let Some(pos) = pos {
- Span::new(pos, pos, item.span.data().ctxt)
- } else {
- return;
- }
- });
-
- let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
- for item in impl_.items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
- ctr_vis.visit_impl_item(item);
- }
-
- span_lint_and_then(
- cx,
- IMPLICIT_HASHER,
- target.span(),
- &format!(
- "impl for `{}` should be generalized over different hashers",
- target.type_name()
- ),
- move |diag| {
- suggestion(cx, diag, impl_.generics.span, generics_suggestion_span, target, ctr_vis);
- },
- );
- }
- },
- ItemKind::Fn(ref sig, ref generics, body_id) => {
- let body = cx.tcx.hir().body(body_id);
-
- for ty in sig.decl.inputs {
- let mut vis = ImplicitHasherTypeVisitor::new(cx);
- vis.visit_ty(ty);
-
- for target in &vis.found {
- if in_external_macro(cx.sess(), generics.span) {
- continue;
- }
- let generics_suggestion_span = generics.span.substitute_dummy({
- let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
- .and_then(|snip| {
- let i = snip.find("fn")?;
- Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
- })
- .expect("failed to create span for type parameters");
- Span::new(pos, pos, item.span.data().ctxt)
- });
-
- let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
- ctr_vis.visit_body(body);
-
- span_lint_and_then(
- cx,
- IMPLICIT_HASHER,
- target.span(),
- &format!(
- "parameter of type `{}` should be generalized over different hashers",
- target.type_name()
- ),
- move |diag| {
- suggestion(cx, diag, generics.span, generics_suggestion_span, target, ctr_vis);
- },
- );
- }
- }
- },
- _ => {},
- }
- }
-}
-
-enum ImplicitHasherType<'tcx> {
- HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
- HashSet(Span, Ty<'tcx>, Cow<'static, str>),
-}
-
-impl<'tcx> ImplicitHasherType<'tcx> {
- /// Checks that `ty` is a target type without a `BuildHasher`.
- fn new(cx: &LateContext<'tcx>, hir_ty: &hir::Ty<'_>) -> Option<Self> {
- if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.kind {
- let params: Vec<_> = path
- .segments
- .last()
- .as_ref()?
- .args
- .as_ref()?
- .args
- .iter()
- .filter_map(|arg| match arg {
- GenericArg::Type(ty) => Some(ty),
- _ => None,
- })
- .collect();
- let params_len = params.len();
-
- let ty = hir_ty_to_ty(cx.tcx, hir_ty);
-
- if is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) && params_len == 2 {
- Some(ImplicitHasherType::HashMap(
- hir_ty.span,
- ty,
- snippet(cx, params[0].span, "K"),
- snippet(cx, params[1].span, "V"),
- ))
- } else if is_type_diagnostic_item(cx, ty, sym!(hashset_type)) && params_len == 1 {
- Some(ImplicitHasherType::HashSet(
- hir_ty.span,
- ty,
- snippet(cx, params[0].span, "T"),
- ))
- } else {
- None
- }
- } else {
- None
- }
- }
-
- fn type_name(&self) -> &'static str {
- match *self {
- ImplicitHasherType::HashMap(..) => "HashMap",
- ImplicitHasherType::HashSet(..) => "HashSet",
- }
- }
-
- fn type_arguments(&self) -> String {
- match *self {
- ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
- ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
- }
- }
-
- fn ty(&self) -> Ty<'tcx> {
- match *self {
- ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
- }
- }
-
- fn span(&self) -> Span {
- match *self {
- ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
- }
- }
-}
-
-struct ImplicitHasherTypeVisitor<'a, 'tcx> {
- cx: &'a LateContext<'tcx>,
- found: Vec<ImplicitHasherType<'tcx>>,
-}
-
-impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
- fn new(cx: &'a LateContext<'tcx>) -> Self {
- Self { cx, found: vec![] }
- }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
- type Map = Map<'tcx>;
-
- fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
- if let Some(target) = ImplicitHasherType::new(self.cx, t) {
- self.found.push(target);
- }
-
- walk_ty(self, t);
- }
-
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
- }
-}
-
-/// Looks for default-hasher-dependent constructors like `HashMap::new`.
-struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
- cx: &'a LateContext<'tcx>,
- maybe_typeck_results: Option<&'tcx TypeckResults<'tcx>>,
- target: &'b ImplicitHasherType<'tcx>,
- suggestions: BTreeMap<Span, String>,
-}
-
-impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
- fn new(cx: &'a LateContext<'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
- Self {
- cx,
- maybe_typeck_results: cx.maybe_typeck_results(),
- target,
- suggestions: BTreeMap::new(),
- }
- }
-}
-
-impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
- type Map = Map<'tcx>;
-
- fn visit_body(&mut self, body: &'tcx Body<'_>) {
- let old_maybe_typeck_results = self.maybe_typeck_results.replace(self.cx.tcx.typeck_body(body.id()));
- walk_body(self, body);
- self.maybe_typeck_results = old_maybe_typeck_results;
- }
-
- fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
- if_chain! {
- if let ExprKind::Call(ref fun, ref args) = e.kind;
- if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.kind;
- if let TyKind::Path(QPath::Resolved(None, ty_path)) = ty.kind;
- then {
- if !TyS::same_type(self.target.ty(), self.maybe_typeck_results.unwrap().expr_ty(e)) {
- return;
- }
-
- if match_path(ty_path, &paths::HASHMAP) {
- if method.ident.name == sym::new {
- self.suggestions
- .insert(e.span, "HashMap::default()".to_string());
- } else if method.ident.name == sym!(with_capacity) {
- self.suggestions.insert(
- e.span,
- format!(
- "HashMap::with_capacity_and_hasher({}, Default::default())",
- snippet(self.cx, args[0].span, "capacity"),
- ),
- );
- }
- } else if match_path(ty_path, &paths::HASHSET) {
- if method.ident.name == sym::new {
- self.suggestions
- .insert(e.span, "HashSet::default()".to_string());
- } else if method.ident.name == sym!(with_capacity) {
- self.suggestions.insert(
- e.span,
- format!(
- "HashSet::with_capacity_and_hasher({}, Default::default())",
- snippet(self.cx, args[0].span, "capacity"),
- ),
- );
- }
- }
- }
- }
-
- walk_expr(self, e);
- }
-
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
- }
-}
-
-declare_clippy_lint! {
- /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
- ///
- /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
- /// `UnsafeCell` is the only way to obtain aliasable data that is considered
- /// mutable.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- /// ```rust,ignore
- /// fn x(r: &i32) {
- /// unsafe {
- /// *(r as *const _ as *mut _) += 1;
- /// }
- /// }
- /// ```
- ///
- /// Instead consider using interior mutability types.
- ///
- /// ```rust
- /// use std::cell::UnsafeCell;
- ///
- /// fn x(r: &UnsafeCell<i32>) {
- /// unsafe {
- /// *r.get() += 1;
- /// }
- /// }
- /// ```
- pub CAST_REF_TO_MUT,
- correctness,
- "a cast of reference to a mutable pointer"
-}
-
-declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
-
-impl<'tcx> LateLintPass<'tcx> for RefToMut {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- if_chain! {
- if let ExprKind::Unary(UnOp::Deref, e) = &expr.kind;
- if let ExprKind::Cast(e, t) = &e.kind;
- if let TyKind::Ptr(MutTy { mutbl: Mutability::Mut, .. }) = t.kind;
- if let ExprKind::Cast(e, t) = &e.kind;
- if let TyKind::Ptr(MutTy { mutbl: Mutability::Not, .. }) = t.kind;
- if let ty::Ref(..) = cx.typeck_results().node_type(e.hir_id).kind();
- then {
- span_lint(
- cx,
- CAST_REF_TO_MUT,
- expr.span,
- "casting `&T` to `&mut T` may cause undefined behavior, consider instead using an `UnsafeCell`",
- );
- }
- }
- }
-}
-
-const PTR_AS_PTR_MSRV: RustcVersion = RustcVersion::new(1, 38, 0);
-
-declare_clippy_lint! {
- /// **What it does:**
- /// Checks for `as` casts between raw pointers without changing its mutability,
- /// namely `*const T` to `*const U` and `*mut T` to `*mut U`.
- ///
- /// **Why is this bad?**
- /// Though `as` casts between raw pointers is not terrible, `pointer::cast` is safer because
- /// it cannot accidentally change the pointer's mutability nor cast the pointer to other types like `usize`.
- ///
- /// **Known problems:** None.
- ///
- /// **Example:**
- ///
- /// ```rust
- /// let ptr: *const u32 = &42_u32;
- /// let mut_ptr: *mut u32 = &mut 42_u32;
- /// let _ = ptr as *const i32;
- /// let _ = mut_ptr as *mut i32;
- /// ```
- /// Use instead:
- /// ```rust
- /// let ptr: *const u32 = &42_u32;
- /// let mut_ptr: *mut u32 = &mut 42_u32;
- /// let _ = ptr.cast::<i32>();
- /// let _ = mut_ptr.cast::<i32>();
- /// ```
- pub PTR_AS_PTR,
- pedantic,
- "casting using `as` from and to raw pointers that doesn't change its mutability, where `pointer::cast` could take the place of `as`"
-}
-
-pub struct PtrAsPtr {
- msrv: Option<RustcVersion>,
-}
-
-impl PtrAsPtr {
- #[must_use]
- pub fn new(msrv: Option<RustcVersion>) -> Self {
- Self { msrv }
- }
-}
-
-impl_lint_pass!(PtrAsPtr => [PTR_AS_PTR]);
-
-impl<'tcx> LateLintPass<'tcx> for PtrAsPtr {
- fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
- if !meets_msrv(self.msrv.as_ref(), &PTR_AS_PTR_MSRV) {
- return;
- }
-
- if expr.span.from_expansion() {
- return;
- }
-
- if_chain! {
- if let ExprKind::Cast(cast_expr, cast_to_hir_ty) = expr.kind;
- let (cast_from, cast_to) = (cx.typeck_results().expr_ty(cast_expr), cx.typeck_results().expr_ty(expr));
- if let ty::RawPtr(TypeAndMut { mutbl: from_mutbl, .. }) = cast_from.kind();
- if let ty::RawPtr(TypeAndMut { ty: to_pointee_ty, mutbl: to_mutbl }) = cast_to.kind();
- if matches!((from_mutbl, to_mutbl),
- (Mutability::Not, Mutability::Not) | (Mutability::Mut, Mutability::Mut));
- // The `U` in `pointer::cast` have to be `Sized`
- // as explained here: https://github.com/rust-lang/rust/issues/60602.
- if to_pointee_ty.is_sized(cx.tcx.at(expr.span), cx.param_env);
- then {
- let mut applicability = Applicability::MachineApplicable;
- let cast_expr_sugg = Sugg::hir_with_applicability(cx, cast_expr, "_", &mut applicability);
- let turbofish = match &cast_to_hir_ty.kind {
- TyKind::Infer => Cow::Borrowed(""),
- TyKind::Ptr(mut_ty) if matches!(mut_ty.ty.kind, TyKind::Infer) => Cow::Borrowed(""),
- _ => Cow::Owned(format!("::<{}>", to_pointee_ty)),
- };
- span_lint_and_sugg(
- cx,
- PTR_AS_PTR,
- expr.span,
- "`as` casting between raw pointers without changing its mutability",
- "try `pointer::cast`, a safer alternative",
- format!("{}.cast{}()", cast_expr_sugg.maybe_par(), turbofish),
- applicability,
- );
- }
- }
- }
-
- extract_msrv_attr!(LateContext);
-}
--- /dev/null
+#![allow(rustc::default_hash_types)]
+
+use std::borrow::Cow;
+use std::cmp::Ordering;
+use std::collections::BTreeMap;
+
+use if_chain::if_chain;
+use rustc_ast::{LitFloatType, LitIntType, LitKind};
+use rustc_errors::{Applicability, DiagnosticBuilder};
+use rustc_hir as hir;
+use rustc_hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
+use rustc_hir::{
+ BinOpKind, Block, Body, Expr, ExprKind, FnDecl, FnRetTy, FnSig, GenericArg, GenericBounds, GenericParamKind, HirId,
+ ImplItem, ImplItemKind, Item, ItemKind, LangItem, Lifetime, Lit, Local, MatchSource, MutTy, Mutability, Node,
+ QPath, Stmt, StmtKind, SyntheticTyParamKind, TraitFn, TraitItem, TraitItemKind, TyKind, UnOp,
+};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::hir::map::Map;
+use rustc_middle::lint::in_external_macro;
+use rustc_middle::ty::TypeFoldable;
+use rustc_middle::ty::{self, FloatTy, InferTy, IntTy, Ty, TyCtxt, TyS, TypeAndMut, TypeckResults, UintTy};
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
+use rustc_span::hygiene::{ExpnKind, MacroKind};
+use rustc_span::source_map::Span;
+use rustc_span::symbol::sym;
+use rustc_target::abi::LayoutOf;
+use rustc_target::spec::abi::Abi;
+use rustc_typeck::hir_ty_to_ty;
+
+use crate::consts::{constant, Constant};
+use crate::utils::paths;
+use crate::utils::sugg::Sugg;
+use crate::utils::{
+ clip, comparisons, differing_macro_contexts, get_qpath_generic_tys, higher, in_constant, indent_of, int_bits,
+ is_hir_ty_cfg_dependant, is_ty_param_diagnostic_item, is_ty_param_lang_item, is_type_diagnostic_item,
+ last_path_segment, match_def_path, match_path, meets_msrv, method_chain_args, multispan_sugg,
+ numeric_literal::NumericLiteral, reindent_multiline, sext, snippet, snippet_opt, snippet_with_applicability,
+ snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then, unsext,
+};
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
+ /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
+ ///
+ /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
+ /// the heap. So if you `Box` it, you just add another level of indirection
+ /// without any benefit whatsoever.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// struct X {
+ /// values: Box<Vec<Foo>>,
+ /// }
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust,ignore
+ /// struct X {
+ /// values: Vec<Foo>,
+ /// }
+ /// ```
+ pub BOX_VEC,
+ perf,
+ "usage of `Box<Vec<T>>`, vector elements are already on the heap"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
+ /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
+ ///
+ /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
+ /// the heap. So if you `Box` its contents, you just add another level of indirection.
+ ///
+ /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see [#3530](https://github.com/rust-lang/rust-clippy/issues/3530),
+ /// 1st comment).
+ ///
+ /// **Example:**
+ /// ```rust
+ /// struct X {
+ /// values: Vec<Box<i32>>,
+ /// }
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust
+ /// struct X {
+ /// values: Vec<i32>,
+ /// }
+ /// ```
+ pub VEC_BOX,
+ complexity,
+ "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
+ /// definitions
+ ///
+ /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
+ /// represents an optional optional value which is logically the same thing as an optional
+ /// value but has an unneeded extra level of wrapping.
+ ///
+ /// If you have a case where `Some(Some(_))`, `Some(None)` and `None` are distinct cases,
+ /// consider a custom `enum` instead, with clear names for each case.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example**
+ /// ```rust
+ /// fn get_data() -> Option<Option<u32>> {
+ /// None
+ /// }
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust
+ /// pub enum Contents {
+ /// Data(Vec<u8>), // Was Some(Some(Vec<u8>))
+ /// NotYetFetched, // Was Some(None)
+ /// None, // Was None
+ /// }
+ ///
+ /// fn get_data() -> Contents {
+ /// Contents::None
+ /// }
+ /// ```
+ pub OPTION_OPTION,
+ pedantic,
+ "usage of `Option<Option<T>>`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
+ /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
+ ///
+ /// **Why is this bad?** Gankro says:
+ ///
+ /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
+ /// pointers and indirection.
+ /// > It wastes memory, it has terrible cache locality, and is all-around slow.
+ /// `RingBuf`, while
+ /// > "only" amortized for push/pop, should be faster in the general case for
+ /// almost every possible
+ /// > workload, and isn't even amortized at all if you can predict the capacity
+ /// you need.
+ /// >
+ /// > `LinkedList`s are only really good if you're doing a lot of merging or
+ /// splitting of lists.
+ /// > This is because they can just mangle some pointers instead of actually
+ /// copying the data. Even
+ /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
+ /// can still be better
+ /// > because of how expensive it is to seek to the middle of a `LinkedList`.
+ ///
+ /// **Known problems:** False positives – the instances where using a
+ /// `LinkedList` makes sense are few and far between, but they can still happen.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// # use std::collections::LinkedList;
+ /// let x: LinkedList<usize> = LinkedList::new();
+ /// ```
+ pub LINKEDLIST,
+ pedantic,
+ "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a `VecDeque`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
+ /// Check the [Box documentation](https://doc.rust-lang.org/std/boxed/index.html) for more information.
+ ///
+ /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
+ /// general.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// fn foo(bar: &Box<T>) { ... }
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust,ignore
+ /// fn foo(bar: &T) { ... }
+ /// ```
+ pub BORROWED_BOX,
+ complexity,
+ "a borrow of a boxed type"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for use of redundant allocations anywhere in the code.
+ ///
+ /// **Why is this bad?** Expressions such as `Rc<&T>`, `Rc<Rc<T>>`, `Rc<Box<T>>`, `Box<&T>`
+ /// add an unnecessary level of indirection.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// fn foo(bar: Rc<&usize>) {}
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust
+ /// fn foo(bar: &usize) {}
+ /// ```
+ pub REDUNDANT_ALLOCATION,
+ perf,
+ "redundant allocation"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for `Rc<T>` and `Arc<T>` when `T` is a mutable buffer type such as `String` or `Vec`.
+ ///
+ /// **Why is this bad?** Expressions such as `Rc<String>` usually have no advantage over `Rc<str>`, since
+ /// it is larger and involves an extra level of indirection, and doesn't implement `Borrow<str>`.
+ ///
+ /// While mutating a buffer type would still be possible with `Rc::get_mut()`, it only
+ /// works if there are no additional references yet, which usually defeats the purpose of
+ /// enclosing it in a shared ownership type. Instead, additionally wrapping the inner
+ /// type with an interior mutable container (such as `RefCell` or `Mutex`) would normally
+ /// be used.
+ ///
+ /// **Known problems:** This pattern can be desirable to avoid the overhead of a `RefCell` or `Mutex` for
+ /// cases where mutation only happens before there are any additional references.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// # use std::rc::Rc;
+ /// fn foo(interned: Rc<String>) { ... }
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust,ignore
+ /// fn foo(interned: Rc<str>) { ... }
+ /// ```
+ pub RC_BUFFER,
+ restriction,
+ "shared ownership of a buffer type"
+}
+
+pub struct Types {
+ vec_box_size_threshold: u64,
+}
+
+impl_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX, REDUNDANT_ALLOCATION, RC_BUFFER]);
+
+impl<'tcx> LateLintPass<'tcx> for Types {
+ fn check_fn(&mut self, cx: &LateContext<'_>, _: FnKind<'_>, decl: &FnDecl<'_>, _: &Body<'_>, _: Span, id: HirId) {
+ // Skip trait implementations; see issue #605.
+ if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
+ if let ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = item.kind {
+ return;
+ }
+ }
+
+ self.check_fn_decl(cx, decl);
+ }
+
+ fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &hir::StructField<'_>) {
+ self.check_ty(cx, &field.ty, false);
+ }
+
+ fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &TraitItem<'_>) {
+ match item.kind {
+ TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_ty(cx, ty, false),
+ TraitItemKind::Fn(ref sig, _) => self.check_fn_decl(cx, &sig.decl),
+ _ => (),
+ }
+ }
+
+ fn check_local(&mut self, cx: &LateContext<'_>, local: &Local<'_>) {
+ if let Some(ref ty) = local.ty {
+ self.check_ty(cx, ty, true);
+ }
+ }
+}
+
+fn match_buffer_type(cx: &LateContext<'_>, qpath: &QPath<'_>) -> Option<&'static str> {
+ if is_ty_param_diagnostic_item(cx, qpath, sym::string_type).is_some() {
+ Some("str")
+ } else if is_ty_param_diagnostic_item(cx, qpath, sym::OsString).is_some() {
+ Some("std::ffi::OsStr")
+ } else if is_ty_param_diagnostic_item(cx, qpath, sym::PathBuf).is_some() {
+ Some("std::path::Path")
+ } else {
+ None
+ }
+}
+
+fn match_borrows_parameter(_cx: &LateContext<'_>, qpath: &QPath<'_>) -> Option<Span> {
+ let last = last_path_segment(qpath);
+ if_chain! {
+ if let Some(ref params) = last.args;
+ if !params.parenthesized;
+ if let Some(ty) = params.args.iter().find_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ });
+ if let TyKind::Rptr(..) = ty.kind;
+ then {
+ return Some(ty.span);
+ }
+ }
+ None
+}
+
+impl Types {
+ pub fn new(vec_box_size_threshold: u64) -> Self {
+ Self { vec_box_size_threshold }
+ }
+
+ fn check_fn_decl(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>) {
+ for input in decl.inputs {
+ self.check_ty(cx, input, false);
+ }
+
+ if let FnRetTy::Return(ref ty) = decl.output {
+ self.check_ty(cx, ty, false);
+ }
+ }
+
+ /// Recursively check for `TypePass` lints in the given type. Stop at the first
+ /// lint found.
+ ///
+ /// The parameter `is_local` distinguishes the context of the type; types from
+ /// local bindings should only be checked for the `BORROWED_BOX` lint.
+ #[allow(clippy::too_many_lines)]
+ fn check_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, is_local: bool) {
+ if hir_ty.span.from_expansion() {
+ return;
+ }
+ match hir_ty.kind {
+ TyKind::Path(ref qpath) if !is_local => {
+ let hir_id = hir_ty.hir_id;
+ let res = cx.qpath_res(qpath, hir_id);
+ if let Some(def_id) = res.opt_def_id() {
+ if Some(def_id) == cx.tcx.lang_items().owned_box() {
+ if let Some(span) = match_borrows_parameter(cx, qpath) {
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ REDUNDANT_ALLOCATION,
+ hir_ty.span,
+ "usage of `Box<&T>`",
+ "try",
+ snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
+ applicability,
+ );
+ return; // don't recurse into the type
+ }
+ if is_ty_param_diagnostic_item(cx, qpath, sym::vec_type).is_some() {
+ span_lint_and_help(
+ cx,
+ BOX_VEC,
+ hir_ty.span,
+ "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
+ None,
+ "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation",
+ );
+ return; // don't recurse into the type
+ }
+ } else if cx.tcx.is_diagnostic_item(sym::Rc, def_id) {
+ if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::Rc) {
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ REDUNDANT_ALLOCATION,
+ hir_ty.span,
+ "usage of `Rc<Rc<T>>`",
+ "try",
+ snippet_with_applicability(cx, ty.span, "..", &mut applicability).to_string(),
+ applicability,
+ );
+ return; // don't recurse into the type
+ }
+ if let Some(ty) = is_ty_param_lang_item(cx, qpath, LangItem::OwnedBox) {
+ let qpath = match &ty.kind {
+ TyKind::Path(qpath) => qpath,
+ _ => return,
+ };
+ let inner_span = match get_qpath_generic_tys(qpath).next() {
+ Some(ty) => ty.span,
+ None => return,
+ };
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ REDUNDANT_ALLOCATION,
+ hir_ty.span,
+ "usage of `Rc<Box<T>>`",
+ "try",
+ format!(
+ "Rc<{}>",
+ snippet_with_applicability(cx, inner_span, "..", &mut applicability)
+ ),
+ applicability,
+ );
+ return; // don't recurse into the type
+ }
+ if let Some(alternate) = match_buffer_type(cx, qpath) {
+ span_lint_and_sugg(
+ cx,
+ RC_BUFFER,
+ hir_ty.span,
+ "usage of `Rc<T>` when T is a buffer type",
+ "try",
+ format!("Rc<{}>", alternate),
+ Applicability::MachineApplicable,
+ );
+ return; // don't recurse into the type
+ }
+ if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::vec_type) {
+ let qpath = match &ty.kind {
+ TyKind::Path(qpath) => qpath,
+ _ => return,
+ };
+ let inner_span = match get_qpath_generic_tys(qpath).next() {
+ Some(ty) => ty.span,
+ None => return,
+ };
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ RC_BUFFER,
+ hir_ty.span,
+ "usage of `Rc<T>` when T is a buffer type",
+ "try",
+ format!(
+ "Rc<[{}]>",
+ snippet_with_applicability(cx, inner_span, "..", &mut applicability)
+ ),
+ Applicability::MachineApplicable,
+ );
+ return; // don't recurse into the type
+ }
+ if let Some(span) = match_borrows_parameter(cx, qpath) {
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ REDUNDANT_ALLOCATION,
+ hir_ty.span,
+ "usage of `Rc<&T>`",
+ "try",
+ snippet_with_applicability(cx, span, "..", &mut applicability).to_string(),
+ applicability,
+ );
+ return; // don't recurse into the type
+ }
+ } else if cx.tcx.is_diagnostic_item(sym::Arc, def_id) {
+ if let Some(alternate) = match_buffer_type(cx, qpath) {
+ span_lint_and_sugg(
+ cx,
+ RC_BUFFER,
+ hir_ty.span,
+ "usage of `Arc<T>` when T is a buffer type",
+ "try",
+ format!("Arc<{}>", alternate),
+ Applicability::MachineApplicable,
+ );
+ return; // don't recurse into the type
+ }
+ if let Some(ty) = is_ty_param_diagnostic_item(cx, qpath, sym::vec_type) {
+ let qpath = match &ty.kind {
+ TyKind::Path(qpath) => qpath,
+ _ => return,
+ };
+ let inner_span = match get_qpath_generic_tys(qpath).next() {
+ Some(ty) => ty.span,
+ None => return,
+ };
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ RC_BUFFER,
+ hir_ty.span,
+ "usage of `Arc<T>` when T is a buffer type",
+ "try",
+ format!(
+ "Arc<[{}]>",
+ snippet_with_applicability(cx, inner_span, "..", &mut applicability)
+ ),
+ Applicability::MachineApplicable,
+ );
+ return; // don't recurse into the type
+ }
+ } else if cx.tcx.is_diagnostic_item(sym::vec_type, def_id) {
+ if_chain! {
+ // Get the _ part of Vec<_>
+ if let Some(ref last) = last_path_segment(qpath).args;
+ if let Some(ty) = last.args.iter().find_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ });
+ // ty is now _ at this point
+ if let TyKind::Path(ref ty_qpath) = ty.kind;
+ let res = cx.qpath_res(ty_qpath, ty.hir_id);
+ if let Some(def_id) = res.opt_def_id();
+ if Some(def_id) == cx.tcx.lang_items().owned_box();
+ // At this point, we know ty is Box<T>, now get T
+ if let Some(ref last) = last_path_segment(ty_qpath).args;
+ if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ });
+ let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
+ if !ty_ty.has_escaping_bound_vars();
+ if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env);
+ if let Ok(ty_ty_size) = cx.layout_of(ty_ty).map(|l| l.size.bytes());
+ if ty_ty_size <= self.vec_box_size_threshold;
+ then {
+ span_lint_and_sugg(
+ cx,
+ VEC_BOX,
+ hir_ty.span,
+ "`Vec<T>` is already on the heap, the boxing is unnecessary",
+ "try",
+ format!("Vec<{}>", snippet(cx, boxed_ty.span, "..")),
+ Applicability::MachineApplicable,
+ );
+ return; // don't recurse into the type
+ }
+ }
+ } else if cx.tcx.is_diagnostic_item(sym::option_type, def_id) {
+ if is_ty_param_diagnostic_item(cx, qpath, sym::option_type).is_some() {
+ span_lint(
+ cx,
+ OPTION_OPTION,
+ hir_ty.span,
+ "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
+ enum if you need to distinguish all 3 cases",
+ );
+ return; // don't recurse into the type
+ }
+ } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
+ span_lint_and_help(
+ cx,
+ LINKEDLIST,
+ hir_ty.span,
+ "you seem to be using a `LinkedList`! Perhaps you meant some other data structure?",
+ None,
+ "a `VecDeque` might work",
+ );
+ return; // don't recurse into the type
+ }
+ }
+ match *qpath {
+ QPath::Resolved(Some(ref ty), ref p) => {
+ self.check_ty(cx, ty, is_local);
+ for ty in p.segments.iter().flat_map(|seg| {
+ seg.args
+ .as_ref()
+ .map_or_else(|| [].iter(), |params| params.args.iter())
+ .filter_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ })
+ }) {
+ self.check_ty(cx, ty, is_local);
+ }
+ },
+ QPath::Resolved(None, ref p) => {
+ for ty in p.segments.iter().flat_map(|seg| {
+ seg.args
+ .as_ref()
+ .map_or_else(|| [].iter(), |params| params.args.iter())
+ .filter_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ })
+ }) {
+ self.check_ty(cx, ty, is_local);
+ }
+ },
+ QPath::TypeRelative(ref ty, ref seg) => {
+ self.check_ty(cx, ty, is_local);
+ if let Some(ref params) = seg.args {
+ for ty in params.args.iter().filter_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ }) {
+ self.check_ty(cx, ty, is_local);
+ }
+ }
+ },
+ QPath::LangItem(..) => {},
+ }
+ },
+ TyKind::Rptr(ref lt, ref mut_ty) => self.check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
+ // recurse
+ TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
+ self.check_ty(cx, ty, is_local)
+ },
+ TyKind::Tup(tys) => {
+ for ty in tys {
+ self.check_ty(cx, ty, is_local);
+ }
+ },
+ _ => {},
+ }
+ }
+
+ fn check_ty_rptr(
+ &mut self,
+ cx: &LateContext<'_>,
+ hir_ty: &hir::Ty<'_>,
+ is_local: bool,
+ lt: &Lifetime,
+ mut_ty: &MutTy<'_>,
+ ) {
+ match mut_ty.ty.kind {
+ TyKind::Path(ref qpath) => {
+ let hir_id = mut_ty.ty.hir_id;
+ let def = cx.qpath_res(qpath, hir_id);
+ if_chain! {
+ if let Some(def_id) = def.opt_def_id();
+ if Some(def_id) == cx.tcx.lang_items().owned_box();
+ if let QPath::Resolved(None, ref path) = *qpath;
+ if let [ref bx] = *path.segments;
+ if let Some(ref params) = bx.args;
+ if !params.parenthesized;
+ if let Some(inner) = params.args.iter().find_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ });
+ then {
+ if is_any_trait(inner) {
+ // Ignore `Box<Any>` types; see issue #1884 for details.
+ return;
+ }
+
+ let ltopt = if lt.is_elided() {
+ String::new()
+ } else {
+ format!("{} ", lt.name.ident().as_str())
+ };
+
+ if mut_ty.mutbl == Mutability::Mut {
+ // Ignore `&mut Box<T>` types; see issue #2907 for
+ // details.
+ return;
+ }
+
+ // When trait objects or opaque types have lifetime or auto-trait bounds,
+ // we need to add parentheses to avoid a syntax error due to its ambiguity.
+ // Originally reported as the issue #3128.
+ let inner_snippet = snippet(cx, inner.span, "..");
+ let suggestion = match &inner.kind {
+ TyKind::TraitObject(bounds, lt_bound) if bounds.len() > 1 || !lt_bound.is_elided() => {
+ format!("&{}({})", ltopt, &inner_snippet)
+ },
+ TyKind::Path(qpath)
+ if get_bounds_if_impl_trait(cx, qpath, inner.hir_id)
+ .map_or(false, |bounds| bounds.len() > 1) =>
+ {
+ format!("&{}({})", ltopt, &inner_snippet)
+ },
+ _ => format!("&{}{}", ltopt, &inner_snippet),
+ };
+ span_lint_and_sugg(
+ cx,
+ BORROWED_BOX,
+ hir_ty.span,
+ "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
+ "try",
+ suggestion,
+ // To make this `MachineApplicable`, at least one needs to check if it isn't a trait item
+ // because the trait impls of it will break otherwise;
+ // and there may be other cases that result in invalid code.
+ // For example, type coercion doesn't work nicely.
+ Applicability::Unspecified,
+ );
+ return; // don't recurse into the type
+ }
+ };
+ self.check_ty(cx, &mut_ty.ty, is_local);
+ },
+ _ => self.check_ty(cx, &mut_ty.ty, is_local),
+ }
+ }
+}
+
+// Returns true if given type is `Any` trait.
+fn is_any_trait(t: &hir::Ty<'_>) -> bool {
+ if_chain! {
+ if let TyKind::TraitObject(ref traits, _) = t.kind;
+ if !traits.is_empty();
+ // Only Send/Sync can be used as additional traits, so it is enough to
+ // check only the first trait.
+ if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
+ then {
+ return true;
+ }
+ }
+
+ false
+}
+
+fn get_bounds_if_impl_trait<'tcx>(cx: &LateContext<'tcx>, qpath: &QPath<'_>, id: HirId) -> Option<GenericBounds<'tcx>> {
+ if_chain! {
+ if let Some(did) = cx.qpath_res(qpath, id).opt_def_id();
+ if let Some(Node::GenericParam(generic_param)) = cx.tcx.hir().get_if_local(did);
+ if let GenericParamKind::Type { synthetic, .. } = generic_param.kind;
+ if synthetic == Some(SyntheticTyParamKind::ImplTrait);
+ then {
+ Some(generic_param.bounds)
+ } else {
+ None
+ }
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for binding a unit value.
+ ///
+ /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
+ /// binding one is kind of pointless.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let x = {
+ /// 1;
+ /// };
+ /// ```
+ pub LET_UNIT_VALUE,
+ pedantic,
+ "creating a `let` binding to a value of unit type, which usually can't be used afterwards"
+}
+
+declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
+
+impl<'tcx> LateLintPass<'tcx> for LetUnitValue {
+ fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
+ if let StmtKind::Local(ref local) = stmt.kind {
+ if is_unit(cx.typeck_results().pat_ty(&local.pat)) {
+ if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
+ return;
+ }
+ if higher::is_from_for_desugar(local) {
+ return;
+ }
+ span_lint_and_then(
+ cx,
+ LET_UNIT_VALUE,
+ stmt.span,
+ "this let-binding has unit value",
+ |diag| {
+ if let Some(expr) = &local.init {
+ let snip = snippet_with_macro_callsite(cx, expr.span, "()");
+ diag.span_suggestion(
+ stmt.span,
+ "omit the `let` binding",
+ format!("{};", snip),
+ Applicability::MachineApplicable, // snippet
+ );
+ }
+ },
+ );
+ }
+ }
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for comparisons to unit. This includes all binary
+ /// comparisons (like `==` and `<`) and asserts.
+ ///
+ /// **Why is this bad?** Unit is always equal to itself, and thus is just a
+ /// clumsily written constant. Mostly this happens when someone accidentally
+ /// adds semicolons at the end of the operands.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// # fn foo() {};
+ /// # fn bar() {};
+ /// # fn baz() {};
+ /// if {
+ /// foo();
+ /// } == {
+ /// bar();
+ /// } {
+ /// baz();
+ /// }
+ /// ```
+ /// is equal to
+ /// ```rust
+ /// # fn foo() {};
+ /// # fn bar() {};
+ /// # fn baz() {};
+ /// {
+ /// foo();
+ /// bar();
+ /// baz();
+ /// }
+ /// ```
+ ///
+ /// For asserts:
+ /// ```rust
+ /// # fn foo() {};
+ /// # fn bar() {};
+ /// assert_eq!({ foo(); }, { bar(); });
+ /// ```
+ /// will always succeed
+ pub UNIT_CMP,
+ correctness,
+ "comparing unit values"
+}
+
+declare_lint_pass!(UnitCmp => [UNIT_CMP]);
+
+impl<'tcx> LateLintPass<'tcx> for UnitCmp {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+ if expr.span.from_expansion() {
+ if let Some(callee) = expr.span.source_callee() {
+ if let ExpnKind::Macro(MacroKind::Bang, symbol) = callee.kind {
+ if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
+ let op = cmp.node;
+ if op.is_comparison() && is_unit(cx.typeck_results().expr_ty(left)) {
+ let result = match &*symbol.as_str() {
+ "assert_eq" | "debug_assert_eq" => "succeed",
+ "assert_ne" | "debug_assert_ne" => "fail",
+ _ => return,
+ };
+ span_lint(
+ cx,
+ UNIT_CMP,
+ expr.span,
+ &format!(
+ "`{}` of unit values detected. This will always {}",
+ symbol.as_str(),
+ result
+ ),
+ );
+ }
+ }
+ }
+ }
+ return;
+ }
+ if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
+ let op = cmp.node;
+ if op.is_comparison() && is_unit(cx.typeck_results().expr_ty(left)) {
+ let result = match op {
+ BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
+ _ => "false",
+ };
+ span_lint(
+ cx,
+ UNIT_CMP,
+ expr.span,
+ &format!(
+ "{}-comparison of unit values detected. This will always be {}",
+ op.as_str(),
+ result
+ ),
+ );
+ }
+ }
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for passing a unit value as an argument to a function without using a
+ /// unit literal (`()`).
+ ///
+ /// **Why is this bad?** This is likely the result of an accidental semicolon.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// foo({
+ /// let a = bar();
+ /// baz(a);
+ /// })
+ /// ```
+ pub UNIT_ARG,
+ complexity,
+ "passing unit to a function"
+}
+
+declare_lint_pass!(UnitArg => [UNIT_ARG]);
+
+impl<'tcx> LateLintPass<'tcx> for UnitArg {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if expr.span.from_expansion() {
+ return;
+ }
+
+ // apparently stuff in the desugaring of `?` can trigger this
+ // so check for that here
+ // only the calls to `Try::from_error` is marked as desugared,
+ // so we need to check both the current Expr and its parent.
+ if is_questionmark_desugar_marked_call(expr) {
+ return;
+ }
+ if_chain! {
+ let map = &cx.tcx.hir();
+ let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
+ if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
+ if is_questionmark_desugar_marked_call(parent_expr);
+ then {
+ return;
+ }
+ }
+
+ match expr.kind {
+ ExprKind::Call(_, args) | ExprKind::MethodCall(_, _, args, _) => {
+ let args_to_recover = args
+ .iter()
+ .filter(|arg| {
+ if is_unit(cx.typeck_results().expr_ty(arg)) && !is_unit_literal(arg) {
+ !matches!(
+ &arg.kind,
+ ExprKind::Match(.., MatchSource::TryDesugar) | ExprKind::Path(..)
+ )
+ } else {
+ false
+ }
+ })
+ .collect::<Vec<_>>();
+ if !args_to_recover.is_empty() {
+ lint_unit_args(cx, expr, &args_to_recover);
+ }
+ },
+ _ => (),
+ }
+ }
+}
+
+fn fmt_stmts_and_call(
+ cx: &LateContext<'_>,
+ call_expr: &Expr<'_>,
+ call_snippet: &str,
+ args_snippets: &[impl AsRef<str>],
+ non_empty_block_args_snippets: &[impl AsRef<str>],
+) -> String {
+ let call_expr_indent = indent_of(cx, call_expr.span).unwrap_or(0);
+ let call_snippet_with_replacements = args_snippets
+ .iter()
+ .fold(call_snippet.to_owned(), |acc, arg| acc.replacen(arg.as_ref(), "()", 1));
+
+ let mut stmts_and_call = non_empty_block_args_snippets
+ .iter()
+ .map(|it| it.as_ref().to_owned())
+ .collect::<Vec<_>>();
+ stmts_and_call.push(call_snippet_with_replacements);
+ stmts_and_call = stmts_and_call
+ .into_iter()
+ .map(|v| reindent_multiline(v.into(), true, Some(call_expr_indent)).into_owned())
+ .collect();
+
+ let mut stmts_and_call_snippet = stmts_and_call.join(&format!("{}{}", ";\n", " ".repeat(call_expr_indent)));
+ // expr is not in a block statement or result expression position, wrap in a block
+ let parent_node = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(call_expr.hir_id));
+ if !matches!(parent_node, Some(Node::Block(_))) && !matches!(parent_node, Some(Node::Stmt(_))) {
+ let block_indent = call_expr_indent + 4;
+ stmts_and_call_snippet =
+ reindent_multiline(stmts_and_call_snippet.into(), true, Some(block_indent)).into_owned();
+ stmts_and_call_snippet = format!(
+ "{{\n{}{}\n{}}}",
+ " ".repeat(block_indent),
+ &stmts_and_call_snippet,
+ " ".repeat(call_expr_indent)
+ );
+ }
+ stmts_and_call_snippet
+}
+
+fn lint_unit_args(cx: &LateContext<'_>, expr: &Expr<'_>, args_to_recover: &[&Expr<'_>]) {
+ let mut applicability = Applicability::MachineApplicable;
+ let (singular, plural) = if args_to_recover.len() > 1 {
+ ("", "s")
+ } else {
+ ("a ", "")
+ };
+ span_lint_and_then(
+ cx,
+ UNIT_ARG,
+ expr.span,
+ &format!("passing {}unit value{} to a function", singular, plural),
+ |db| {
+ let mut or = "";
+ args_to_recover
+ .iter()
+ .filter_map(|arg| {
+ if_chain! {
+ if let ExprKind::Block(block, _) = arg.kind;
+ if block.expr.is_none();
+ if let Some(last_stmt) = block.stmts.iter().last();
+ if let StmtKind::Semi(last_expr) = last_stmt.kind;
+ if let Some(snip) = snippet_opt(cx, last_expr.span);
+ then {
+ Some((
+ last_stmt.span,
+ snip,
+ ))
+ }
+ else {
+ None
+ }
+ }
+ })
+ .for_each(|(span, sugg)| {
+ db.span_suggestion(
+ span,
+ "remove the semicolon from the last statement in the block",
+ sugg,
+ Applicability::MaybeIncorrect,
+ );
+ or = "or ";
+ applicability = Applicability::MaybeIncorrect;
+ });
+
+ let arg_snippets: Vec<String> = args_to_recover
+ .iter()
+ .filter_map(|arg| snippet_opt(cx, arg.span))
+ .collect();
+ let arg_snippets_without_empty_blocks: Vec<String> = args_to_recover
+ .iter()
+ .filter(|arg| !is_empty_block(arg))
+ .filter_map(|arg| snippet_opt(cx, arg.span))
+ .collect();
+
+ if let Some(call_snippet) = snippet_opt(cx, expr.span) {
+ let sugg = fmt_stmts_and_call(
+ cx,
+ expr,
+ &call_snippet,
+ &arg_snippets,
+ &arg_snippets_without_empty_blocks,
+ );
+
+ if arg_snippets_without_empty_blocks.is_empty() {
+ db.multipart_suggestion(
+ &format!("use {}unit literal{} instead", singular, plural),
+ args_to_recover
+ .iter()
+ .map(|arg| (arg.span, "()".to_string()))
+ .collect::<Vec<_>>(),
+ applicability,
+ );
+ } else {
+ let plural = arg_snippets_without_empty_blocks.len() > 1;
+ let empty_or_s = if plural { "s" } else { "" };
+ let it_or_them = if plural { "them" } else { "it" };
+ db.span_suggestion(
+ expr.span,
+ &format!(
+ "{}move the expression{} in front of the call and replace {} with the unit literal `()`",
+ or, empty_or_s, it_or_them
+ ),
+ sugg,
+ applicability,
+ );
+ }
+ }
+ },
+ );
+}
+
+fn is_empty_block(expr: &Expr<'_>) -> bool {
+ matches!(
+ expr.kind,
+ ExprKind::Block(
+ Block {
+ stmts: &[],
+ expr: None,
+ ..
+ },
+ _,
+ )
+ )
+}
+
+fn is_questionmark_desugar_marked_call(expr: &Expr<'_>) -> bool {
+ use rustc_span::hygiene::DesugaringKind;
+ if let ExprKind::Call(ref callee, _) = expr.kind {
+ callee.span.is_desugaring(DesugaringKind::QuestionMark)
+ } else {
+ false
+ }
+}
+
+fn is_unit(ty: Ty<'_>) -> bool {
+ matches!(ty.kind(), ty::Tuple(slice) if slice.is_empty())
+}
+
+fn is_unit_literal(expr: &Expr<'_>) -> bool {
+ matches!(expr.kind, ExprKind::Tup(ref slice) if slice.is_empty())
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts from any numerical to a float type where
+ /// the receiving type cannot store all values from the original type without
+ /// rounding errors. This possible rounding is to be expected, so this lint is
+ /// `Allow` by default.
+ ///
+ /// Basically, this warns on casting any integer with 32 or more bits to `f32`
+ /// or any 64-bit integer to `f64`.
+ ///
+ /// **Why is this bad?** It's not bad at all. But in some applications it can be
+ /// helpful to know where precision loss can take place. This lint can help find
+ /// those places in the code.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let x = u64::MAX;
+ /// x as f64;
+ /// ```
+ pub CAST_PRECISION_LOSS,
+ pedantic,
+ "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts from a signed to an unsigned numerical
+ /// type. In this case, negative values wrap around to large positive values,
+ /// which can be quite surprising in practice. However, as the cast works as
+ /// defined, this lint is `Allow` by default.
+ ///
+ /// **Why is this bad?** Possibly surprising results. You can activate this lint
+ /// as a one-time check to see where numerical wrapping can arise.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let y: i8 = -1;
+ /// y as u128; // will return 18446744073709551615
+ /// ```
+ pub CAST_SIGN_LOSS,
+ pedantic,
+ "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts between numerical types that may
+ /// truncate large values. This is expected behavior, so the cast is `Allow` by
+ /// default.
+ ///
+ /// **Why is this bad?** In some problem domains, it is good practice to avoid
+ /// truncation. This lint can be activated to help assess where additional
+ /// checks could be beneficial.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// fn as_u8(x: u64) -> u8 {
+ /// x as u8
+ /// }
+ /// ```
+ pub CAST_POSSIBLE_TRUNCATION,
+ pedantic,
+ "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts from an unsigned type to a signed type of
+ /// the same size. Performing such a cast is a 'no-op' for the compiler,
+ /// i.e., nothing is changed at the bit level, and the binary representation of
+ /// the value is reinterpreted. This can cause wrapping if the value is too big
+ /// for the target signed type. However, the cast works as defined, so this lint
+ /// is `Allow` by default.
+ ///
+ /// **Why is this bad?** While such a cast is not bad in itself, the results can
+ /// be surprising when this is not the intended behavior, as demonstrated by the
+ /// example below.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// u32::MAX as i32; // will yield a value of `-1`
+ /// ```
+ pub CAST_POSSIBLE_WRAP,
+ pedantic,
+ "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts between numerical types that may
+ /// be replaced by safe conversion functions.
+ ///
+ /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
+ /// conversions, including silently lossy conversions. Conversion functions such
+ /// as `i32::from` will only perform lossless conversions. Using the conversion
+ /// functions prevents conversions from turning into silent lossy conversions if
+ /// the types of the input expressions ever change, and make it easier for
+ /// people reading the code to know that the conversion is lossless.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// fn as_u64(x: u8) -> u64 {
+ /// x as u64
+ /// }
+ /// ```
+ ///
+ /// Using `::from` would look like this:
+ ///
+ /// ```rust
+ /// fn as_u64(x: u8) -> u64 {
+ /// u64::from(x)
+ /// }
+ /// ```
+ pub CAST_LOSSLESS,
+ pedantic,
+ "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts to the same type, casts of int literals to integer types
+ /// and casts of float literals to float types.
+ ///
+ /// **Why is this bad?** It's just unnecessary.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let _ = 2i32 as i32;
+ /// let _ = 0.5 as f32;
+ /// ```
+ ///
+ /// Better:
+ ///
+ /// ```rust
+ /// let _ = 2_i32;
+ /// let _ = 0.5_f32;
+ /// ```
+ pub UNNECESSARY_CAST,
+ complexity,
+ "cast to the same type, e.g., `x as i32` where `x: i32`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts, using `as` or `pointer::cast`,
+ /// from a less-strictly-aligned pointer to a more-strictly-aligned pointer
+ ///
+ /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
+ /// behavior.
+ ///
+ /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
+ /// on the resulting pointer is fine. Is over-zealous: Casts with manual alignment checks or casts like
+ /// u64-> u8 -> u16 can be fine. Miri is able to do a more in-depth analysis.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let _ = (&1u8 as *const u8) as *const u16;
+ /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
+ ///
+ /// (&1u8 as *const u8).cast::<u16>();
+ /// (&mut 1u8 as *mut u8).cast::<u16>();
+ /// ```
+ pub CAST_PTR_ALIGNMENT,
+ pedantic,
+ "cast from a pointer to a more-strictly-aligned pointer"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts of function pointers to something other than usize
+ ///
+ /// **Why is this bad?**
+ /// Casting a function pointer to anything other than usize/isize is not portable across
+ /// architectures, because you end up losing bits if the target type is too small or end up with a
+ /// bunch of extra bits that waste space and add more instructions to the final binary than
+ /// strictly necessary for the problem
+ ///
+ /// Casting to isize also doesn't make sense since there are no signed addresses.
+ ///
+ /// **Example**
+ ///
+ /// ```rust
+ /// // Bad
+ /// fn fun() -> i32 { 1 }
+ /// let a = fun as i64;
+ ///
+ /// // Good
+ /// fn fun2() -> i32 { 1 }
+ /// let a = fun2 as usize;
+ /// ```
+ pub FN_TO_NUMERIC_CAST,
+ style,
+ "casting a function pointer to a numeric type other than usize"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
+ /// store address.
+ ///
+ /// **Why is this bad?**
+ /// Such a cast discards some bits of the function's address. If this is intended, it would be more
+ /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
+ /// a comment) to perform the truncation.
+ ///
+ /// **Example**
+ ///
+ /// ```rust
+ /// // Bad
+ /// fn fn1() -> i16 {
+ /// 1
+ /// };
+ /// let _ = fn1 as i32;
+ ///
+ /// // Better: Cast to usize first, then comment with the reason for the truncation
+ /// fn fn2() -> i16 {
+ /// 1
+ /// };
+ /// let fn_ptr = fn2 as usize;
+ /// let fn_ptr_truncated = fn_ptr as i32;
+ /// ```
+ pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
+ style,
+ "casting a function pointer to a numeric type not wide enough to store the address"
+}
+
+/// Returns the size in bits of an integral type.
+/// Will return 0 if the type is not an int or uint variant
+fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
+ match typ.kind() {
+ ty::Int(i) => match i {
+ IntTy::Isize => tcx.data_layout.pointer_size.bits(),
+ IntTy::I8 => 8,
+ IntTy::I16 => 16,
+ IntTy::I32 => 32,
+ IntTy::I64 => 64,
+ IntTy::I128 => 128,
+ },
+ ty::Uint(i) => match i {
+ UintTy::Usize => tcx.data_layout.pointer_size.bits(),
+ UintTy::U8 => 8,
+ UintTy::U16 => 16,
+ UintTy::U32 => 32,
+ UintTy::U64 => 64,
+ UintTy::U128 => 128,
+ },
+ _ => 0,
+ }
+}
+
+fn is_isize_or_usize(typ: Ty<'_>) -> bool {
+ matches!(typ.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
+}
+
+fn span_precision_loss_lint(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to_f64: bool) {
+ let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
+ let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
+ let arch_dependent_str = "on targets with 64-bit wide pointers ";
+ let from_nbits_str = if arch_dependent {
+ "64".to_owned()
+ } else if is_isize_or_usize(cast_from) {
+ "32 or 64".to_owned()
+ } else {
+ int_ty_to_nbits(cast_from, cx.tcx).to_string()
+ };
+ span_lint(
+ cx,
+ CAST_PRECISION_LOSS,
+ expr.span,
+ &format!(
+ "casting `{0}` to `{1}` causes a loss of precision {2}(`{0}` is {3} bits wide, \
+ but `{1}`'s mantissa is only {4} bits wide)",
+ cast_from,
+ if cast_to_f64 { "f64" } else { "f32" },
+ if arch_dependent { arch_dependent_str } else { "" },
+ from_nbits_str,
+ mantissa_nbits
+ ),
+ );
+}
+
+fn should_strip_parens(op: &Expr<'_>, snip: &str) -> bool {
+ if let ExprKind::Binary(_, _, _) = op.kind {
+ if snip.starts_with('(') && snip.ends_with(')') {
+ return true;
+ }
+ }
+ false
+}
+
+fn span_lossless_lint(cx: &LateContext<'_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+ // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
+ if in_constant(cx, expr.hir_id) {
+ return;
+ }
+ // The suggestion is to use a function call, so if the original expression
+ // has parens on the outside, they are no longer needed.
+ let mut applicability = Applicability::MachineApplicable;
+ let opt = snippet_opt(cx, op.span);
+ let sugg = opt.as_ref().map_or_else(
+ || {
+ applicability = Applicability::HasPlaceholders;
+ ".."
+ },
+ |snip| {
+ if should_strip_parens(op, snip) {
+ &snip[1..snip.len() - 1]
+ } else {
+ snip.as_str()
+ }
+ },
+ );
+
+ span_lint_and_sugg(
+ cx,
+ CAST_LOSSLESS,
+ expr.span,
+ &format!(
+ "casting `{}` to `{}` may become silently lossy if you later change the type",
+ cast_from, cast_to
+ ),
+ "try",
+ format!("{}::from({})", cast_to, sugg),
+ applicability,
+ );
+}
+
+enum ArchSuffix {
+ _32,
+ _64,
+ None,
+}
+
+fn check_loss_of_sign(cx: &LateContext<'_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+ if !cast_from.is_signed() || cast_to.is_signed() {
+ return;
+ }
+
+ // don't lint for positive constants
+ let const_val = constant(cx, &cx.typeck_results(), op);
+ if_chain! {
+ if let Some((Constant::Int(n), _)) = const_val;
+ if let ty::Int(ity) = *cast_from.kind();
+ if sext(cx.tcx, n, ity) >= 0;
+ then {
+ return
+ }
+ }
+
+ // don't lint for the result of methods that always return non-negative values
+ if let ExprKind::MethodCall(ref path, _, _, _) = op.kind {
+ let mut method_name = path.ident.name.as_str();
+ let allowed_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
+
+ if_chain! {
+ if method_name == "unwrap";
+ if let Some(arglist) = method_chain_args(op, &["unwrap"]);
+ if let ExprKind::MethodCall(ref inner_path, _, _, _) = &arglist[0][0].kind;
+ then {
+ method_name = inner_path.ident.name.as_str();
+ }
+ }
+
+ if allowed_methods.iter().any(|&name| method_name == name) {
+ return;
+ }
+ }
+
+ span_lint(
+ cx,
+ CAST_SIGN_LOSS,
+ expr.span,
+ &format!(
+ "casting `{}` to `{}` may lose the sign of the value",
+ cast_from, cast_to
+ ),
+ );
+}
+
+fn check_truncation_and_wrapping(cx: &LateContext<'_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+ let arch_64_suffix = " on targets with 64-bit wide pointers";
+ let arch_32_suffix = " on targets with 32-bit wide pointers";
+ let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
+ let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
+ let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
+ let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
+ match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
+ (true, true) | (false, false) => (
+ to_nbits < from_nbits,
+ ArchSuffix::None,
+ to_nbits == from_nbits && cast_unsigned_to_signed,
+ ArchSuffix::None,
+ ),
+ (true, false) => (
+ to_nbits <= 32,
+ if to_nbits == 32 {
+ ArchSuffix::_64
+ } else {
+ ArchSuffix::None
+ },
+ to_nbits <= 32 && cast_unsigned_to_signed,
+ ArchSuffix::_32,
+ ),
+ (false, true) => (
+ from_nbits == 64,
+ ArchSuffix::_32,
+ cast_unsigned_to_signed,
+ if from_nbits == 64 {
+ ArchSuffix::_64
+ } else {
+ ArchSuffix::_32
+ },
+ ),
+ };
+ if span_truncation {
+ span_lint(
+ cx,
+ CAST_POSSIBLE_TRUNCATION,
+ expr.span,
+ &format!(
+ "casting `{}` to `{}` may truncate the value{}",
+ cast_from,
+ cast_to,
+ match suffix_truncation {
+ ArchSuffix::_32 => arch_32_suffix,
+ ArchSuffix::_64 => arch_64_suffix,
+ ArchSuffix::None => "",
+ }
+ ),
+ );
+ }
+ if span_wrap {
+ span_lint(
+ cx,
+ CAST_POSSIBLE_WRAP,
+ expr.span,
+ &format!(
+ "casting `{}` to `{}` may wrap around the value{}",
+ cast_from,
+ cast_to,
+ match suffix_wrap {
+ ArchSuffix::_32 => arch_32_suffix,
+ ArchSuffix::_64 => arch_64_suffix,
+ ArchSuffix::None => "",
+ }
+ ),
+ );
+ }
+}
+
+fn check_lossless(cx: &LateContext<'_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+ let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
+ let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
+ let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
+ if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
+ {
+ span_lossless_lint(cx, expr, op, cast_from, cast_to);
+ }
+}
+
+declare_lint_pass!(Casts => [
+ CAST_PRECISION_LOSS,
+ CAST_SIGN_LOSS,
+ CAST_POSSIBLE_TRUNCATION,
+ CAST_POSSIBLE_WRAP,
+ CAST_LOSSLESS,
+ UNNECESSARY_CAST,
+ CAST_PTR_ALIGNMENT,
+ FN_TO_NUMERIC_CAST,
+ FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
+]);
+
+// Check if the given type is either `core::ffi::c_void` or
+// one of the platform specific `libc::<platform>::c_void` of libc.
+fn is_c_void(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
+ if let ty::Adt(adt, _) = ty.kind() {
+ let names = cx.get_def_path(adt.did);
+
+ if names.is_empty() {
+ return false;
+ }
+ if names[0] == sym::libc || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
+ return true;
+ }
+ }
+ false
+}
+
+/// Returns the mantissa bits wide of a fp type.
+/// Will return 0 if the type is not a fp
+fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
+ match typ.kind() {
+ ty::Float(FloatTy::F32) => 23,
+ ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
+ _ => 0,
+ }
+}
+
+impl<'tcx> LateLintPass<'tcx> for Casts {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if expr.span.from_expansion() {
+ return;
+ }
+ if let ExprKind::Cast(ref ex, cast_to) = expr.kind {
+ if is_hir_ty_cfg_dependant(cx, cast_to) {
+ return;
+ }
+ let (cast_from, cast_to) = (cx.typeck_results().expr_ty(ex), cx.typeck_results().expr_ty(expr));
+ lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
+ if let Some(lit) = get_numeric_literal(ex) {
+ let literal_str = snippet_opt(cx, ex.span).unwrap_or_default();
+
+ if_chain! {
+ if let LitKind::Int(n, _) = lit.node;
+ if let Some(src) = snippet_opt(cx, lit.span);
+ if cast_to.is_floating_point();
+ if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node);
+ let from_nbits = 128 - n.leading_zeros();
+ let to_nbits = fp_ty_mantissa_nbits(cast_to);
+ if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits && num_lit.is_decimal();
+ then {
+ let literal_str = if is_unary_neg(ex) { format!("-{}", num_lit.integer) } else { num_lit.integer.into() };
+ show_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
+ return;
+ }
+ }
+
+ match lit.node {
+ LitKind::Int(_, LitIntType::Unsuffixed) if cast_to.is_integral() => {
+ show_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
+ },
+ LitKind::Float(_, LitFloatType::Unsuffixed) if cast_to.is_floating_point() => {
+ show_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
+ },
+ LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
+ _ => {
+ if cast_from.kind() == cast_to.kind() && !in_external_macro(cx.sess(), expr.span) {
+ span_lint(
+ cx,
+ UNNECESSARY_CAST,
+ expr.span,
+ &format!(
+ "casting to the same type is unnecessary (`{}` -> `{}`)",
+ cast_from, cast_to
+ ),
+ );
+ }
+ },
+ }
+ }
+ if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
+ lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
+ }
+
+ lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
+ } else if let ExprKind::MethodCall(method_path, _, args, _) = expr.kind {
+ if_chain! {
+ if method_path.ident.name == sym!(cast);
+ if let Some(generic_args) = method_path.args;
+ if let [GenericArg::Type(cast_to)] = generic_args.args;
+ // There probably is no obvious reason to do this, just to be consistent with `as` cases.
+ if !is_hir_ty_cfg_dependant(cx, cast_to);
+ then {
+ let (cast_from, cast_to) =
+ (cx.typeck_results().expr_ty(&args[0]), cx.typeck_results().expr_ty(expr));
+ lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
+ }
+ }
+ }
+ }
+}
+
+fn is_unary_neg(expr: &Expr<'_>) -> bool {
+ matches!(expr.kind, ExprKind::Unary(UnOp::Neg, _))
+}
+
+fn get_numeric_literal<'e>(expr: &'e Expr<'e>) -> Option<&'e Lit> {
+ match expr.kind {
+ ExprKind::Lit(ref lit) => Some(lit),
+ ExprKind::Unary(UnOp::Neg, e) => {
+ if let ExprKind::Lit(ref lit) = e.kind {
+ Some(lit)
+ } else {
+ None
+ }
+ },
+ _ => None,
+ }
+}
+
+fn show_unnecessary_cast(cx: &LateContext<'_>, expr: &Expr<'_>, literal_str: &str, cast_from: Ty<'_>, cast_to: Ty<'_>) {
+ let literal_kind_name = if cast_from.is_integral() { "integer" } else { "float" };
+ span_lint_and_sugg(
+ cx,
+ UNNECESSARY_CAST,
+ expr.span,
+ &format!("casting {} literal to `{}` is unnecessary", literal_kind_name, cast_to),
+ "try",
+ format!("{}_{}", literal_str.trim_end_matches('.'), cast_to),
+ Applicability::MachineApplicable,
+ );
+}
+
+fn lint_numeric_casts<'tcx>(
+ cx: &LateContext<'tcx>,
+ expr: &Expr<'tcx>,
+ cast_expr: &Expr<'_>,
+ cast_from: Ty<'tcx>,
+ cast_to: Ty<'tcx>,
+) {
+ match (cast_from.is_integral(), cast_to.is_integral()) {
+ (true, false) => {
+ let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
+ let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind() {
+ 32
+ } else {
+ 64
+ };
+ if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
+ span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
+ }
+ if from_nbits < to_nbits {
+ span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
+ }
+ },
+ (false, true) => {
+ span_lint(
+ cx,
+ CAST_POSSIBLE_TRUNCATION,
+ expr.span,
+ &format!("casting `{}` to `{}` may truncate the value", cast_from, cast_to),
+ );
+ if !cast_to.is_signed() {
+ span_lint(
+ cx,
+ CAST_SIGN_LOSS,
+ expr.span,
+ &format!(
+ "casting `{}` to `{}` may lose the sign of the value",
+ cast_from, cast_to
+ ),
+ );
+ }
+ },
+ (true, true) => {
+ check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
+ check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
+ check_lossless(cx, expr, cast_expr, cast_from, cast_to);
+ },
+ (false, false) => {
+ if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.kind(), &cast_to.kind()) {
+ span_lint(
+ cx,
+ CAST_POSSIBLE_TRUNCATION,
+ expr.span,
+ "casting `f64` to `f32` may truncate the value",
+ );
+ }
+ if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.kind(), &cast_to.kind()) {
+ span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
+ }
+ },
+ }
+}
+
+fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
+ if_chain! {
+ if let ty::RawPtr(from_ptr_ty) = &cast_from.kind();
+ if let ty::RawPtr(to_ptr_ty) = &cast_to.kind();
+ if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
+ if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
+ if from_layout.align.abi < to_layout.align.abi;
+ // with c_void, we inherently need to trust the user
+ if !is_c_void(cx, from_ptr_ty.ty);
+ // when casting from a ZST, we don't know enough to properly lint
+ if !from_layout.is_zst();
+ then {
+ span_lint(
+ cx,
+ CAST_PTR_ALIGNMENT,
+ expr.span,
+ &format!(
+ "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
+ cast_from,
+ cast_to,
+ from_layout.align.abi.bytes(),
+ to_layout.align.abi.bytes(),
+ ),
+ );
+ }
+ }
+}
+
+fn lint_fn_to_numeric_cast(
+ cx: &LateContext<'_>,
+ expr: &Expr<'_>,
+ cast_expr: &Expr<'_>,
+ cast_from: Ty<'_>,
+ cast_to: Ty<'_>,
+) {
+ // We only want to check casts to `ty::Uint` or `ty::Int`
+ match cast_to.kind() {
+ ty::Uint(_) | ty::Int(..) => { /* continue on */ },
+ _ => return,
+ }
+ match cast_from.kind() {
+ ty::FnDef(..) | ty::FnPtr(_) => {
+ let mut applicability = Applicability::MaybeIncorrect;
+ let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
+
+ let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
+ if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
+ span_lint_and_sugg(
+ cx,
+ FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
+ expr.span,
+ &format!(
+ "casting function pointer `{}` to `{}`, which truncates the value",
+ from_snippet, cast_to
+ ),
+ "try",
+ format!("{} as usize", from_snippet),
+ applicability,
+ );
+ } else if *cast_to.kind() != ty::Uint(UintTy::Usize) {
+ span_lint_and_sugg(
+ cx,
+ FN_TO_NUMERIC_CAST,
+ expr.span,
+ &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
+ "try",
+ format!("{} as usize", from_snippet),
+ applicability,
+ );
+ }
+ },
+ _ => {},
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for types used in structs, parameters and `let`
+ /// declarations above a certain complexity threshold.
+ ///
+ /// **Why is this bad?** Too complex types make the code less readable. Consider
+ /// using a `type` definition to simplify them.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// # use std::rc::Rc;
+ /// struct Foo {
+ /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
+ /// }
+ /// ```
+ pub TYPE_COMPLEXITY,
+ complexity,
+ "usage of very complex types that might be better factored into `type` definitions"
+}
+
+pub struct TypeComplexity {
+ threshold: u64,
+}
+
+impl TypeComplexity {
+ #[must_use]
+ pub fn new(threshold: u64) -> Self {
+ Self { threshold }
+ }
+}
+
+impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
+
+impl<'tcx> LateLintPass<'tcx> for TypeComplexity {
+ fn check_fn(
+ &mut self,
+ cx: &LateContext<'tcx>,
+ _: FnKind<'tcx>,
+ decl: &'tcx FnDecl<'_>,
+ _: &'tcx Body<'_>,
+ _: Span,
+ _: HirId,
+ ) {
+ self.check_fndecl(cx, decl);
+ }
+
+ fn check_struct_field(&mut self, cx: &LateContext<'tcx>, field: &'tcx hir::StructField<'_>) {
+ // enum variants are also struct fields now
+ self.check_type(cx, &field.ty);
+ }
+
+ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+ match item.kind {
+ ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
+ // functions, enums, structs, impls and traits are covered
+ _ => (),
+ }
+ }
+
+ fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
+ match item.kind {
+ TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
+ TraitItemKind::Fn(FnSig { ref decl, .. }, TraitFn::Required(_)) => self.check_fndecl(cx, decl),
+ // methods with default impl are covered by check_fn
+ _ => (),
+ }
+ }
+
+ fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
+ match item.kind {
+ ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
+ // methods are covered by check_fn
+ _ => (),
+ }
+ }
+
+ fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
+ if let Some(ref ty) = local.ty {
+ self.check_type(cx, ty);
+ }
+ }
+}
+
+impl<'tcx> TypeComplexity {
+ fn check_fndecl(&self, cx: &LateContext<'tcx>, decl: &'tcx FnDecl<'_>) {
+ for arg in decl.inputs {
+ self.check_type(cx, arg);
+ }
+ if let FnRetTy::Return(ref ty) = decl.output {
+ self.check_type(cx, ty);
+ }
+ }
+
+ fn check_type(&self, cx: &LateContext<'_>, ty: &hir::Ty<'_>) {
+ if ty.span.from_expansion() {
+ return;
+ }
+ let score = {
+ let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
+ visitor.visit_ty(ty);
+ visitor.score
+ };
+
+ if score > self.threshold {
+ span_lint(
+ cx,
+ TYPE_COMPLEXITY,
+ ty.span,
+ "very complex type used. Consider factoring parts into `type` definitions",
+ );
+ }
+ }
+}
+
+/// Walks a type and assigns a complexity score to it.
+struct TypeComplexityVisitor {
+ /// total complexity score of the type
+ score: u64,
+ /// current nesting level
+ nest: u64,
+}
+
+impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
+ type Map = Map<'tcx>;
+
+ fn visit_ty(&mut self, ty: &'tcx hir::Ty<'_>) {
+ let (add_score, sub_nest) = match ty.kind {
+ // _, &x and *x have only small overhead; don't mess with nesting level
+ TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
+
+ // the "normal" components of a type: named types, arrays/tuples
+ TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
+
+ // function types bring a lot of overhead
+ TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
+
+ TyKind::TraitObject(ref param_bounds, _) => {
+ let has_lifetime_parameters = param_bounds.iter().any(|bound| {
+ bound
+ .bound_generic_params
+ .iter()
+ .any(|gen| matches!(gen.kind, GenericParamKind::Lifetime { .. }))
+ });
+ if has_lifetime_parameters {
+ // complex trait bounds like A<'a, 'b>
+ (50 * self.nest, 1)
+ } else {
+ // simple trait bounds like A + B
+ (20 * self.nest, 0)
+ }
+ },
+
+ _ => (0, 0),
+ };
+ self.score += add_score;
+ self.nest += sub_nest;
+ walk_ty(self, ty);
+ self.nest -= sub_nest;
+ }
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::None
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for expressions where a character literal is cast
+ /// to `u8` and suggests using a byte literal instead.
+ ///
+ /// **Why is this bad?** In general, casting values to smaller types is
+ /// error-prone and should be avoided where possible. In the particular case of
+ /// converting a character literal to u8, it is easy to avoid by just using a
+ /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
+ /// than `'a' as u8`.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// 'x' as u8
+ /// ```
+ ///
+ /// A better version, using the byte literal:
+ ///
+ /// ```rust,ignore
+ /// b'x'
+ /// ```
+ pub CHAR_LIT_AS_U8,
+ complexity,
+ "casting a character literal to `u8` truncates"
+}
+
+declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
+
+impl<'tcx> LateLintPass<'tcx> for CharLitAsU8 {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if_chain! {
+ if !expr.span.from_expansion();
+ if let ExprKind::Cast(e, _) = &expr.kind;
+ if let ExprKind::Lit(l) = &e.kind;
+ if let LitKind::Char(c) = l.node;
+ if ty::Uint(UintTy::U8) == *cx.typeck_results().expr_ty(expr).kind();
+ then {
+ let mut applicability = Applicability::MachineApplicable;
+ let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
+
+ span_lint_and_then(
+ cx,
+ CHAR_LIT_AS_U8,
+ expr.span,
+ "casting a character literal to `u8` truncates",
+ |diag| {
+ diag.note("`char` is four bytes wide, but `u8` is a single byte");
+
+ if c.is_ascii() {
+ diag.span_suggestion(
+ expr.span,
+ "use a byte literal instead",
+ format!("b{}", snippet),
+ applicability,
+ );
+ }
+ });
+ }
+ }
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for comparisons where one side of the relation is
+ /// either the minimum or maximum value for its type and warns if it involves a
+ /// case that is always true or always false. Only integer and boolean types are
+ /// checked.
+ ///
+ /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
+ /// that it is possible for `x` to be less than the minimum. Expressions like
+ /// `max < x` are probably mistakes.
+ ///
+ /// **Known problems:** For `usize` the size of the current compile target will
+ /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
+ /// a comparison to detect target pointer width will trigger this lint. One can
+ /// use `mem::sizeof` and compare its value or conditional compilation
+ /// attributes
+ /// like `#[cfg(target_pointer_width = "64")] ..` instead.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// let vec: Vec<isize> = Vec::new();
+ /// if vec.len() <= 0 {}
+ /// if 100 > i32::MAX {}
+ /// ```
+ pub ABSURD_EXTREME_COMPARISONS,
+ correctness,
+ "a comparison with a maximum or minimum value that is always true or false"
+}
+
+declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
+
+enum ExtremeType {
+ Minimum,
+ Maximum,
+}
+
+struct ExtremeExpr<'a> {
+ which: ExtremeType,
+ expr: &'a Expr<'a>,
+}
+
+enum AbsurdComparisonResult {
+ AlwaysFalse,
+ AlwaysTrue,
+ InequalityImpossible,
+}
+
+fn is_cast_between_fixed_and_target<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
+ if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
+ let precast_ty = cx.typeck_results().expr_ty(cast_exp);
+ let cast_ty = cx.typeck_results().expr_ty(expr);
+
+ return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
+ }
+
+ false
+}
+
+fn detect_absurd_comparison<'tcx>(
+ cx: &LateContext<'tcx>,
+ op: BinOpKind,
+ lhs: &'tcx Expr<'_>,
+ rhs: &'tcx Expr<'_>,
+) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
+ use crate::types::AbsurdComparisonResult::{AlwaysFalse, AlwaysTrue, InequalityImpossible};
+ use crate::types::ExtremeType::{Maximum, Minimum};
+ use crate::utils::comparisons::{normalize_comparison, Rel};
+
+ // absurd comparison only makes sense on primitive types
+ // primitive types don't implement comparison operators with each other
+ if cx.typeck_results().expr_ty(lhs) != cx.typeck_results().expr_ty(rhs) {
+ return None;
+ }
+
+ // comparisons between fix sized types and target sized types are considered unanalyzable
+ if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
+ return None;
+ }
+
+ let (rel, normalized_lhs, normalized_rhs) = normalize_comparison(op, lhs, rhs)?;
+
+ let lx = detect_extreme_expr(cx, normalized_lhs);
+ let rx = detect_extreme_expr(cx, normalized_rhs);
+
+ Some(match rel {
+ Rel::Lt => {
+ match (lx, rx) {
+ (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
+ (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
+ _ => return None,
+ }
+ },
+ Rel::Le => {
+ match (lx, rx) {
+ (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
+ (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
+ (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
+ (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
+ _ => return None,
+ }
+ },
+ Rel::Ne | Rel::Eq => return None,
+ })
+}
+
+fn detect_extreme_expr<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<ExtremeExpr<'tcx>> {
+ use crate::types::ExtremeType::{Maximum, Minimum};
+
+ let ty = cx.typeck_results().expr_ty(expr);
+
+ let cv = constant(cx, cx.typeck_results(), expr)?.0;
+
+ let which = match (ty.kind(), cv) {
+ (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
+ (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::MIN >> (128 - int_bits(cx.tcx, ity)), ity) => {
+ Minimum
+ },
+
+ (&ty::Bool, Constant::Bool(true)) => Maximum,
+ (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::MAX >> (128 - int_bits(cx.tcx, ity)), ity) => {
+ Maximum
+ },
+ (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::MAX, uty) == i => Maximum,
+
+ _ => return None,
+ };
+ Some(ExtremeExpr { which, expr })
+}
+
+impl<'tcx> LateLintPass<'tcx> for AbsurdExtremeComparisons {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ use crate::types::AbsurdComparisonResult::{AlwaysFalse, AlwaysTrue, InequalityImpossible};
+ use crate::types::ExtremeType::{Maximum, Minimum};
+
+ if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
+ if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
+ if !expr.span.from_expansion() {
+ let msg = "this comparison involving the minimum or maximum element for this \
+ type contains a case that is always true or always false";
+
+ let conclusion = match result {
+ AlwaysFalse => "this comparison is always false".to_owned(),
+ AlwaysTrue => "this comparison is always true".to_owned(),
+ InequalityImpossible => format!(
+ "the case where the two sides are not equal never occurs, consider using `{} == {}` \
+ instead",
+ snippet(cx, lhs.span, "lhs"),
+ snippet(cx, rhs.span, "rhs")
+ ),
+ };
+
+ let help = format!(
+ "because `{}` is the {} value for this type, {}",
+ snippet(cx, culprit.expr.span, "x"),
+ match culprit.which {
+ Minimum => "minimum",
+ Maximum => "maximum",
+ },
+ conclusion
+ );
+
+ span_lint_and_help(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, None, &help);
+ }
+ }
+ }
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for comparisons where the relation is always either
+ /// true or false, but where one side has been upcast so that the comparison is
+ /// necessary. Only integer types are checked.
+ ///
+ /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
+ /// will mistakenly imply that it is possible for `x` to be outside the range of
+ /// `u8`.
+ ///
+ /// **Known problems:**
+ /// https://github.com/rust-lang/rust-clippy/issues/886
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let x: u8 = 1;
+ /// (x as u32) > 300;
+ /// ```
+ pub INVALID_UPCAST_COMPARISONS,
+ pedantic,
+ "a comparison involving an upcast which is always true or false"
+}
+
+declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
+
+#[derive(Copy, Clone, Debug, Eq)]
+enum FullInt {
+ S(i128),
+ U(u128),
+}
+
+impl FullInt {
+ #[allow(clippy::cast_sign_loss)]
+ #[must_use]
+ fn cmp_s_u(s: i128, u: u128) -> Ordering {
+ if s < 0 {
+ Ordering::Less
+ } else if u > (i128::MAX as u128) {
+ Ordering::Greater
+ } else {
+ (s as u128).cmp(&u)
+ }
+ }
+}
+
+impl PartialEq for FullInt {
+ #[must_use]
+ fn eq(&self, other: &Self) -> bool {
+ self.partial_cmp(other).expect("`partial_cmp` only returns `Some(_)`") == Ordering::Equal
+ }
+}
+
+impl PartialOrd for FullInt {
+ #[must_use]
+ fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+ Some(match (self, other) {
+ (&Self::S(s), &Self::S(o)) => s.cmp(&o),
+ (&Self::U(s), &Self::U(o)) => s.cmp(&o),
+ (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
+ (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
+ })
+ }
+}
+
+impl Ord for FullInt {
+ #[must_use]
+ fn cmp(&self, other: &Self) -> Ordering {
+ self.partial_cmp(other)
+ .expect("`partial_cmp` for FullInt can never return `None`")
+ }
+}
+
+fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_>, expr: &'a Expr<'_>) -> Option<(FullInt, FullInt)> {
+ if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
+ let pre_cast_ty = cx.typeck_results().expr_ty(cast_exp);
+ let cast_ty = cx.typeck_results().expr_ty(expr);
+ // if it's a cast from i32 to u32 wrapping will invalidate all these checks
+ if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
+ return None;
+ }
+ match pre_cast_ty.kind() {
+ ty::Int(int_ty) => Some(match int_ty {
+ IntTy::I8 => (FullInt::S(i128::from(i8::MIN)), FullInt::S(i128::from(i8::MAX))),
+ IntTy::I16 => (FullInt::S(i128::from(i16::MIN)), FullInt::S(i128::from(i16::MAX))),
+ IntTy::I32 => (FullInt::S(i128::from(i32::MIN)), FullInt::S(i128::from(i32::MAX))),
+ IntTy::I64 => (FullInt::S(i128::from(i64::MIN)), FullInt::S(i128::from(i64::MAX))),
+ IntTy::I128 => (FullInt::S(i128::MIN), FullInt::S(i128::MAX)),
+ IntTy::Isize => (FullInt::S(isize::MIN as i128), FullInt::S(isize::MAX as i128)),
+ }),
+ ty::Uint(uint_ty) => Some(match uint_ty {
+ UintTy::U8 => (FullInt::U(u128::from(u8::MIN)), FullInt::U(u128::from(u8::MAX))),
+ UintTy::U16 => (FullInt::U(u128::from(u16::MIN)), FullInt::U(u128::from(u16::MAX))),
+ UintTy::U32 => (FullInt::U(u128::from(u32::MIN)), FullInt::U(u128::from(u32::MAX))),
+ UintTy::U64 => (FullInt::U(u128::from(u64::MIN)), FullInt::U(u128::from(u64::MAX))),
+ UintTy::U128 => (FullInt::U(u128::MIN), FullInt::U(u128::MAX)),
+ UintTy::Usize => (FullInt::U(usize::MIN as u128), FullInt::U(usize::MAX as u128)),
+ }),
+ _ => None,
+ }
+ } else {
+ None
+ }
+}
+
+fn node_as_const_fullint<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<FullInt> {
+ let val = constant(cx, cx.typeck_results(), expr)?.0;
+ if let Constant::Int(const_int) = val {
+ match *cx.typeck_results().expr_ty(expr).kind() {
+ ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
+ ty::Uint(_) => Some(FullInt::U(const_int)),
+ _ => None,
+ }
+ } else {
+ None
+ }
+}
+
+fn err_upcast_comparison(cx: &LateContext<'_>, span: Span, expr: &Expr<'_>, always: bool) {
+ if let ExprKind::Cast(ref cast_val, _) = expr.kind {
+ span_lint(
+ cx,
+ INVALID_UPCAST_COMPARISONS,
+ span,
+ &format!(
+ "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
+ snippet(cx, cast_val.span, "the expression"),
+ if always { "true" } else { "false" },
+ ),
+ );
+ }
+}
+
+fn upcast_comparison_bounds_err<'tcx>(
+ cx: &LateContext<'tcx>,
+ span: Span,
+ rel: comparisons::Rel,
+ lhs_bounds: Option<(FullInt, FullInt)>,
+ lhs: &'tcx Expr<'_>,
+ rhs: &'tcx Expr<'_>,
+ invert: bool,
+) {
+ use crate::utils::comparisons::Rel;
+
+ if let Some((lb, ub)) = lhs_bounds {
+ if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
+ if rel == Rel::Eq || rel == Rel::Ne {
+ if norm_rhs_val < lb || norm_rhs_val > ub {
+ err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
+ }
+ } else if match rel {
+ Rel::Lt => {
+ if invert {
+ norm_rhs_val < lb
+ } else {
+ ub < norm_rhs_val
+ }
+ },
+ Rel::Le => {
+ if invert {
+ norm_rhs_val <= lb
+ } else {
+ ub <= norm_rhs_val
+ }
+ },
+ Rel::Eq | Rel::Ne => unreachable!(),
+ } {
+ err_upcast_comparison(cx, span, lhs, true)
+ } else if match rel {
+ Rel::Lt => {
+ if invert {
+ norm_rhs_val >= ub
+ } else {
+ lb >= norm_rhs_val
+ }
+ },
+ Rel::Le => {
+ if invert {
+ norm_rhs_val > ub
+ } else {
+ lb > norm_rhs_val
+ }
+ },
+ Rel::Eq | Rel::Ne => unreachable!(),
+ } {
+ err_upcast_comparison(cx, span, lhs, false)
+ }
+ }
+ }
+}
+
+impl<'tcx> LateLintPass<'tcx> for InvalidUpcastComparisons {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
+ let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
+ let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
+ val
+ } else {
+ return;
+ };
+
+ let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
+ let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
+
+ upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
+ upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
+ }
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for public `impl` or `fn` missing generalization
+ /// over different hashers and implicitly defaulting to the default hashing
+ /// algorithm (`SipHash`).
+ ///
+ /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
+ /// used with them.
+ ///
+ /// **Known problems:** Suggestions for replacing constructors can contain
+ /// false-positives. Also applying suggestions can require modification of other
+ /// pieces of code, possibly including external crates.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// # use std::collections::HashMap;
+ /// # use std::hash::{Hash, BuildHasher};
+ /// # trait Serialize {};
+ /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
+ ///
+ /// pub fn foo(map: &mut HashMap<i32, i32>) { }
+ /// ```
+ /// could be rewritten as
+ /// ```rust
+ /// # use std::collections::HashMap;
+ /// # use std::hash::{Hash, BuildHasher};
+ /// # trait Serialize {};
+ /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
+ ///
+ /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
+ /// ```
+ pub IMPLICIT_HASHER,
+ pedantic,
+ "missing generalization over different hashers"
+}
+
+declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
+
+impl<'tcx> LateLintPass<'tcx> for ImplicitHasher {
+ #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
+ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+ use rustc_span::BytePos;
+
+ fn suggestion<'tcx>(
+ cx: &LateContext<'tcx>,
+ diag: &mut DiagnosticBuilder<'_>,
+ generics_span: Span,
+ generics_suggestion_span: Span,
+ target: &ImplicitHasherType<'_>,
+ vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
+ ) {
+ let generics_snip = snippet(cx, generics_span, "");
+ // trim `<` `>`
+ let generics_snip = if generics_snip.is_empty() {
+ ""
+ } else {
+ &generics_snip[1..generics_snip.len() - 1]
+ };
+
+ multispan_sugg(
+ diag,
+ "consider adding a type parameter",
+ vec![
+ (
+ generics_suggestion_span,
+ format!(
+ "<{}{}S: ::std::hash::BuildHasher{}>",
+ generics_snip,
+ if generics_snip.is_empty() { "" } else { ", " },
+ if vis.suggestions.is_empty() {
+ ""
+ } else {
+ // request users to add `Default` bound so that generic constructors can be used
+ " + Default"
+ },
+ ),
+ ),
+ (
+ target.span(),
+ format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
+ ),
+ ],
+ );
+
+ if !vis.suggestions.is_empty() {
+ multispan_sugg(diag, "...and use generic constructor", vis.suggestions);
+ }
+ }
+
+ if !cx.access_levels.is_exported(item.hir_id()) {
+ return;
+ }
+
+ match item.kind {
+ ItemKind::Impl(ref impl_) => {
+ let mut vis = ImplicitHasherTypeVisitor::new(cx);
+ vis.visit_ty(impl_.self_ty);
+
+ for target in &vis.found {
+ if differing_macro_contexts(item.span, target.span()) {
+ return;
+ }
+
+ let generics_suggestion_span = impl_.generics.span.substitute_dummy({
+ let pos = snippet_opt(cx, item.span.until(target.span()))
+ .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
+ if let Some(pos) = pos {
+ Span::new(pos, pos, item.span.data().ctxt)
+ } else {
+ return;
+ }
+ });
+
+ let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
+ for item in impl_.items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
+ ctr_vis.visit_impl_item(item);
+ }
+
+ span_lint_and_then(
+ cx,
+ IMPLICIT_HASHER,
+ target.span(),
+ &format!(
+ "impl for `{}` should be generalized over different hashers",
+ target.type_name()
+ ),
+ move |diag| {
+ suggestion(cx, diag, impl_.generics.span, generics_suggestion_span, target, ctr_vis);
+ },
+ );
+ }
+ },
+ ItemKind::Fn(ref sig, ref generics, body_id) => {
+ let body = cx.tcx.hir().body(body_id);
+
+ for ty in sig.decl.inputs {
+ let mut vis = ImplicitHasherTypeVisitor::new(cx);
+ vis.visit_ty(ty);
+
+ for target in &vis.found {
+ if in_external_macro(cx.sess(), generics.span) {
+ continue;
+ }
+ let generics_suggestion_span = generics.span.substitute_dummy({
+ let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
+ .and_then(|snip| {
+ let i = snip.find("fn")?;
+ Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
+ })
+ .expect("failed to create span for type parameters");
+ Span::new(pos, pos, item.span.data().ctxt)
+ });
+
+ let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
+ ctr_vis.visit_body(body);
+
+ span_lint_and_then(
+ cx,
+ IMPLICIT_HASHER,
+ target.span(),
+ &format!(
+ "parameter of type `{}` should be generalized over different hashers",
+ target.type_name()
+ ),
+ move |diag| {
+ suggestion(cx, diag, generics.span, generics_suggestion_span, target, ctr_vis);
+ },
+ );
+ }
+ }
+ },
+ _ => {},
+ }
+ }
+}
+
+enum ImplicitHasherType<'tcx> {
+ HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
+ HashSet(Span, Ty<'tcx>, Cow<'static, str>),
+}
+
+impl<'tcx> ImplicitHasherType<'tcx> {
+ /// Checks that `ty` is a target type without a `BuildHasher`.
+ fn new(cx: &LateContext<'tcx>, hir_ty: &hir::Ty<'_>) -> Option<Self> {
+ if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.kind {
+ let params: Vec<_> = path
+ .segments
+ .last()
+ .as_ref()?
+ .args
+ .as_ref()?
+ .args
+ .iter()
+ .filter_map(|arg| match arg {
+ GenericArg::Type(ty) => Some(ty),
+ _ => None,
+ })
+ .collect();
+ let params_len = params.len();
+
+ let ty = hir_ty_to_ty(cx.tcx, hir_ty);
+
+ if is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) && params_len == 2 {
+ Some(ImplicitHasherType::HashMap(
+ hir_ty.span,
+ ty,
+ snippet(cx, params[0].span, "K"),
+ snippet(cx, params[1].span, "V"),
+ ))
+ } else if is_type_diagnostic_item(cx, ty, sym!(hashset_type)) && params_len == 1 {
+ Some(ImplicitHasherType::HashSet(
+ hir_ty.span,
+ ty,
+ snippet(cx, params[0].span, "T"),
+ ))
+ } else {
+ None
+ }
+ } else {
+ None
+ }
+ }
+
+ fn type_name(&self) -> &'static str {
+ match *self {
+ ImplicitHasherType::HashMap(..) => "HashMap",
+ ImplicitHasherType::HashSet(..) => "HashSet",
+ }
+ }
+
+ fn type_arguments(&self) -> String {
+ match *self {
+ ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
+ ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
+ }
+ }
+
+ fn ty(&self) -> Ty<'tcx> {
+ match *self {
+ ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
+ }
+ }
+
+ fn span(&self) -> Span {
+ match *self {
+ ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
+ }
+ }
+}
+
+struct ImplicitHasherTypeVisitor<'a, 'tcx> {
+ cx: &'a LateContext<'tcx>,
+ found: Vec<ImplicitHasherType<'tcx>>,
+}
+
+impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
+ fn new(cx: &'a LateContext<'tcx>) -> Self {
+ Self { cx, found: vec![] }
+ }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
+ type Map = Map<'tcx>;
+
+ fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
+ if let Some(target) = ImplicitHasherType::new(self.cx, t) {
+ self.found.push(target);
+ }
+
+ walk_ty(self, t);
+ }
+
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::None
+ }
+}
+
+/// Looks for default-hasher-dependent constructors like `HashMap::new`.
+struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
+ cx: &'a LateContext<'tcx>,
+ maybe_typeck_results: Option<&'tcx TypeckResults<'tcx>>,
+ target: &'b ImplicitHasherType<'tcx>,
+ suggestions: BTreeMap<Span, String>,
+}
+
+impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
+ fn new(cx: &'a LateContext<'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
+ Self {
+ cx,
+ maybe_typeck_results: cx.maybe_typeck_results(),
+ target,
+ suggestions: BTreeMap::new(),
+ }
+ }
+}
+
+impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
+ type Map = Map<'tcx>;
+
+ fn visit_body(&mut self, body: &'tcx Body<'_>) {
+ let old_maybe_typeck_results = self.maybe_typeck_results.replace(self.cx.tcx.typeck_body(body.id()));
+ walk_body(self, body);
+ self.maybe_typeck_results = old_maybe_typeck_results;
+ }
+
+ fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
+ if_chain! {
+ if let ExprKind::Call(ref fun, ref args) = e.kind;
+ if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.kind;
+ if let TyKind::Path(QPath::Resolved(None, ty_path)) = ty.kind;
+ then {
+ if !TyS::same_type(self.target.ty(), self.maybe_typeck_results.unwrap().expr_ty(e)) {
+ return;
+ }
+
+ if match_path(ty_path, &paths::HASHMAP) {
+ if method.ident.name == sym::new {
+ self.suggestions
+ .insert(e.span, "HashMap::default()".to_string());
+ } else if method.ident.name == sym!(with_capacity) {
+ self.suggestions.insert(
+ e.span,
+ format!(
+ "HashMap::with_capacity_and_hasher({}, Default::default())",
+ snippet(self.cx, args[0].span, "capacity"),
+ ),
+ );
+ }
+ } else if match_path(ty_path, &paths::HASHSET) {
+ if method.ident.name == sym::new {
+ self.suggestions
+ .insert(e.span, "HashSet::default()".to_string());
+ } else if method.ident.name == sym!(with_capacity) {
+ self.suggestions.insert(
+ e.span,
+ format!(
+ "HashSet::with_capacity_and_hasher({}, Default::default())",
+ snippet(self.cx, args[0].span, "capacity"),
+ ),
+ );
+ }
+ }
+ }
+ }
+
+ walk_expr(self, e);
+ }
+
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
+ }
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
+ ///
+ /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
+ /// `UnsafeCell` is the only way to obtain aliasable data that is considered
+ /// mutable.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// fn x(r: &i32) {
+ /// unsafe {
+ /// *(r as *const _ as *mut _) += 1;
+ /// }
+ /// }
+ /// ```
+ ///
+ /// Instead consider using interior mutability types.
+ ///
+ /// ```rust
+ /// use std::cell::UnsafeCell;
+ ///
+ /// fn x(r: &UnsafeCell<i32>) {
+ /// unsafe {
+ /// *r.get() += 1;
+ /// }
+ /// }
+ /// ```
+ pub CAST_REF_TO_MUT,
+ correctness,
+ "a cast of reference to a mutable pointer"
+}
+
+declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
+
+impl<'tcx> LateLintPass<'tcx> for RefToMut {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if_chain! {
+ if let ExprKind::Unary(UnOp::Deref, e) = &expr.kind;
+ if let ExprKind::Cast(e, t) = &e.kind;
+ if let TyKind::Ptr(MutTy { mutbl: Mutability::Mut, .. }) = t.kind;
+ if let ExprKind::Cast(e, t) = &e.kind;
+ if let TyKind::Ptr(MutTy { mutbl: Mutability::Not, .. }) = t.kind;
+ if let ty::Ref(..) = cx.typeck_results().node_type(e.hir_id).kind();
+ then {
+ span_lint(
+ cx,
+ CAST_REF_TO_MUT,
+ expr.span,
+ "casting `&T` to `&mut T` may cause undefined behavior, consider instead using an `UnsafeCell`",
+ );
+ }
+ }
+ }
+}
+
+const PTR_AS_PTR_MSRV: RustcVersion = RustcVersion::new(1, 38, 0);
+
+declare_clippy_lint! {
+ /// **What it does:**
+ /// Checks for `as` casts between raw pointers without changing its mutability,
+ /// namely `*const T` to `*const U` and `*mut T` to `*mut U`.
+ ///
+ /// **Why is this bad?**
+ /// Though `as` casts between raw pointers is not terrible, `pointer::cast` is safer because
+ /// it cannot accidentally change the pointer's mutability nor cast the pointer to other types like `usize`.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// let ptr: *const u32 = &42_u32;
+ /// let mut_ptr: *mut u32 = &mut 42_u32;
+ /// let _ = ptr as *const i32;
+ /// let _ = mut_ptr as *mut i32;
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// let ptr: *const u32 = &42_u32;
+ /// let mut_ptr: *mut u32 = &mut 42_u32;
+ /// let _ = ptr.cast::<i32>();
+ /// let _ = mut_ptr.cast::<i32>();
+ /// ```
+ pub PTR_AS_PTR,
+ pedantic,
+ "casting using `as` from and to raw pointers that doesn't change its mutability, where `pointer::cast` could take the place of `as`"
+}
+
+pub struct PtrAsPtr {
+ msrv: Option<RustcVersion>,
+}
+
+impl PtrAsPtr {
+ #[must_use]
+ pub fn new(msrv: Option<RustcVersion>) -> Self {
+ Self { msrv }
+ }
+}
+
+impl_lint_pass!(PtrAsPtr => [PTR_AS_PTR]);
+
+impl<'tcx> LateLintPass<'tcx> for PtrAsPtr {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if !meets_msrv(self.msrv.as_ref(), &PTR_AS_PTR_MSRV) {
+ return;
+ }
+
+ if expr.span.from_expansion() {
+ return;
+ }
+
+ if_chain! {
+ if let ExprKind::Cast(cast_expr, cast_to_hir_ty) = expr.kind;
+ let (cast_from, cast_to) = (cx.typeck_results().expr_ty(cast_expr), cx.typeck_results().expr_ty(expr));
+ if let ty::RawPtr(TypeAndMut { mutbl: from_mutbl, .. }) = cast_from.kind();
+ if let ty::RawPtr(TypeAndMut { ty: to_pointee_ty, mutbl: to_mutbl }) = cast_to.kind();
+ if matches!((from_mutbl, to_mutbl),
+ (Mutability::Not, Mutability::Not) | (Mutability::Mut, Mutability::Mut));
+ // The `U` in `pointer::cast` have to be `Sized`
+ // as explained here: https://github.com/rust-lang/rust/issues/60602.
+ if to_pointee_ty.is_sized(cx.tcx.at(expr.span), cx.param_env);
+ then {
+ let mut applicability = Applicability::MachineApplicable;
+ let cast_expr_sugg = Sugg::hir_with_applicability(cx, cast_expr, "_", &mut applicability);
+ let turbofish = match &cast_to_hir_ty.kind {
+ TyKind::Infer => Cow::Borrowed(""),
+ TyKind::Ptr(mut_ty) if matches!(mut_ty.ty.kind, TyKind::Infer) => Cow::Borrowed(""),
+ _ => Cow::Owned(format!("::<{}>", to_pointee_ty)),
+ };
+ span_lint_and_sugg(
+ cx,
+ PTR_AS_PTR,
+ expr.span,
+ "`as` casting between raw pointers without changing its mutability",
+ "try `pointer::cast`, a safer alternative",
+ format!("{}.cast{}()", cast_expr_sugg.maybe_par(), turbofish),
+ applicability,
+ );
+ }
+ }
+ }
+
+ extract_msrv_attr!(LateContext);
+}
projects / rust.git / commitdiff