1 #![allow(rustc::default_hash_types)]
4 use std::cmp::Ordering;
5 use std::collections::BTreeMap;
7 use if_chain::if_chain;
9 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
11 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
12 use rustc::ty::layout::LayoutOf;
13 use rustc::ty::{self, InferTy, Ty, TyCtxt, TypeckTables};
14 use rustc::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
15 use rustc_errors::Applicability;
16 use rustc_target::spec::abi::Abi;
17 use rustc_typeck::hir_ty_to_ty;
18 use syntax::ast::{FloatTy, IntTy, LitFloatType, LitIntType, LitKind, UintTy};
19 use syntax::errors::DiagnosticBuilder;
20 use syntax::source_map::Span;
21 use syntax::symbol::{sym, Symbol};
22 use syntax_pos::hygiene::{ExpnKind, MacroKind};
24 use crate::consts::{constant, Constant};
25 use crate::utils::paths;
27 clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
28 match_path, multispan_sugg, qpath_res, same_tys, sext, snippet, snippet_opt, snippet_with_applicability,
29 snippet_with_macro_callsite, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
32 declare_clippy_lint! {
33 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
35 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
36 /// the heap. So if you `Box` it, you just add another level of indirection
37 /// without any benefit whatsoever.
39 /// **Known problems:** None.
44 /// values: Box<Vec<Foo>>,
57 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
60 declare_clippy_lint! {
61 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
63 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
64 /// the heap. So if you `Box` its contents, you just add another level of indirection.
66 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
72 /// values: Vec<Box<i32>>,
85 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
88 declare_clippy_lint! {
89 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
92 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
93 /// represents an optional optional value which is logically the same thing as an optional
94 /// value but has an unneeded extra level of wrapping.
96 /// **Known problems:** None.
100 /// fn x() -> Option<Option<u32>> {
106 "usage of `Option<Option<T>>`"
109 declare_clippy_lint! {
110 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
111 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
113 /// **Why is this bad?** Gankro says:
115 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
116 /// pointers and indirection.
117 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
119 /// > "only" amortized for push/pop, should be faster in the general case for
120 /// almost every possible
121 /// > workload, and isn't even amortized at all if you can predict the capacity
124 /// > `LinkedList`s are only really good if you're doing a lot of merging or
125 /// splitting of lists.
126 /// > This is because they can just mangle some pointers instead of actually
127 /// copying the data. Even
128 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
129 /// can still be better
130 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
132 /// **Known problems:** False positives – the instances where using a
133 /// `LinkedList` makes sense are few and far between, but they can still happen.
137 /// # use std::collections::LinkedList;
138 /// let x: LinkedList<usize> = LinkedList::new();
142 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
145 declare_clippy_lint! {
146 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
148 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
151 /// **Known problems:** None.
155 /// fn foo(bar: &Box<T>) { ... }
161 /// fn foo(bar: &T) { ... }
165 "a borrow of a boxed type"
168 declare_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX]);
170 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Types {
171 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
172 // Skip trait implementations; see issue #605.
173 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
174 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.kind {
179 check_fn_decl(cx, decl);
182 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
183 check_ty(cx, &field.ty, false);
186 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
188 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
189 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
194 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
195 if let Some(ref ty) = local.ty {
196 check_ty(cx, ty, true);
201 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
202 for input in &decl.inputs {
203 check_ty(cx, input, false);
206 if let FunctionRetTy::Return(ref ty) = decl.output {
207 check_ty(cx, ty, false);
211 /// Checks if `qpath` has last segment with type parameter matching `path`
212 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
213 let last = last_path_segment(qpath);
215 if let Some(ref params) = last.args;
216 if !params.parenthesized;
217 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
218 GenericArg::Type(ty) => Some(ty),
221 if let TyKind::Path(ref qpath) = ty.kind;
222 if let Some(did) = qpath_res(cx, qpath, ty.hir_id).opt_def_id();
223 if match_def_path(cx, did, path);
231 /// Recursively check for `TypePass` lints in the given type. Stop at the first
234 /// The parameter `is_local` distinguishes the context of the type; types from
235 /// local bindings should only be checked for the `BORROWED_BOX` lint.
236 #[allow(clippy::too_many_lines)]
237 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
238 if hir_ty.span.from_expansion() {
242 TyKind::Path(ref qpath) if !is_local => {
243 let hir_id = hir_ty.hir_id;
244 let res = qpath_res(cx, qpath, hir_id);
245 if let Some(def_id) = res.opt_def_id() {
246 if Some(def_id) == cx.tcx.lang_items().owned_box() {
247 if match_type_parameter(cx, qpath, &paths::VEC) {
252 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
253 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
255 return; // don't recurse into the type
257 } else if cx.tcx.is_diagnostic_item(Symbol::intern("vec_type"), def_id) {
259 // Get the _ part of Vec<_>
260 if let Some(ref last) = last_path_segment(qpath).args;
261 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
262 GenericArg::Type(ty) => Some(ty),
265 // ty is now _ at this point
266 if let TyKind::Path(ref ty_qpath) = ty.kind;
267 let res = qpath_res(cx, ty_qpath, ty.hir_id);
268 if let Some(def_id) = res.opt_def_id();
269 if Some(def_id) == cx.tcx.lang_items().owned_box();
270 // At this point, we know ty is Box<T>, now get T
271 if let Some(ref last) = last_path_segment(ty_qpath).args;
272 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
273 GenericArg::Type(ty) => Some(ty),
277 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
278 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
283 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
285 format!("Vec<{}>", ty_ty),
286 Applicability::MachineApplicable,
288 return; // don't recurse into the type
292 } else if match_def_path(cx, def_id, &paths::OPTION) {
293 if match_type_parameter(cx, qpath, &paths::OPTION) {
298 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
299 enum if you need to distinguish all 3 cases",
301 return; // don't recurse into the type
303 } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
308 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
309 "a VecDeque might work",
311 return; // don't recurse into the type
315 QPath::Resolved(Some(ref ty), ref p) => {
316 check_ty(cx, ty, is_local);
317 for ty in p.segments.iter().flat_map(|seg| {
320 .map_or_else(|| [].iter(), |params| params.args.iter())
321 .filter_map(|arg| match arg {
322 GenericArg::Type(ty) => Some(ty),
326 check_ty(cx, ty, is_local);
329 QPath::Resolved(None, ref p) => {
330 for ty in p.segments.iter().flat_map(|seg| {
333 .map_or_else(|| [].iter(), |params| params.args.iter())
334 .filter_map(|arg| match arg {
335 GenericArg::Type(ty) => Some(ty),
339 check_ty(cx, ty, is_local);
342 QPath::TypeRelative(ref ty, ref seg) => {
343 check_ty(cx, ty, is_local);
344 if let Some(ref params) = seg.args {
345 for ty in params.args.iter().filter_map(|arg| match arg {
346 GenericArg::Type(ty) => Some(ty),
349 check_ty(cx, ty, is_local);
355 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
357 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
358 check_ty(cx, ty, is_local)
360 TyKind::Tup(ref tys) => {
362 check_ty(cx, ty, is_local);
369 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
370 match mut_ty.ty.kind {
371 TyKind::Path(ref qpath) => {
372 let hir_id = mut_ty.ty.hir_id;
373 let def = qpath_res(cx, qpath, hir_id);
375 if let Some(def_id) = def.opt_def_id();
376 if Some(def_id) == cx.tcx.lang_items().owned_box();
377 if let QPath::Resolved(None, ref path) = *qpath;
378 if let [ref bx] = *path.segments;
379 if let Some(ref params) = bx.args;
380 if !params.parenthesized;
381 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
382 GenericArg::Type(ty) => Some(ty),
386 if is_any_trait(inner) {
387 // Ignore `Box<Any>` types; see issue #1884 for details.
391 let ltopt = if lt.is_elided() {
394 format!("{} ", lt.name.ident().as_str())
396 let mutopt = if mut_ty.mutbl == Mutability::Mutable {
401 let mut applicability = Applicability::MachineApplicable;
406 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
412 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
414 Applicability::Unspecified,
416 return; // don't recurse into the type
419 check_ty(cx, &mut_ty.ty, is_local);
421 _ => check_ty(cx, &mut_ty.ty, is_local),
425 // Returns true if given type is `Any` trait.
426 fn is_any_trait(t: &hir::Ty) -> bool {
428 if let TyKind::TraitObject(ref traits, _) = t.kind;
429 if traits.len() >= 1;
430 // Only Send/Sync can be used as additional traits, so it is enough to
431 // check only the first trait.
432 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
441 declare_clippy_lint! {
442 /// **What it does:** Checks for binding a unit value.
444 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
445 /// binding one is kind of pointless.
447 /// **Known problems:** None.
457 "creating a let binding to a value of unit type, which usually can't be used afterwards"
460 declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
462 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnitValue {
463 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
464 if let StmtKind::Local(ref local) = stmt.kind {
465 if is_unit(cx.tables.pat_ty(&local.pat)) {
466 if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
469 if higher::is_from_for_desugar(local) {
472 span_lint_and_then(cx, LET_UNIT_VALUE, stmt.span, "this let-binding has unit value", |db| {
473 if let Some(expr) = &local.init {
474 let snip = snippet_with_macro_callsite(cx, expr.span, "()");
477 "omit the `let` binding",
478 format!("{};", snip),
479 Applicability::MachineApplicable, // snippet
488 declare_clippy_lint! {
489 /// **What it does:** Checks for comparisons to unit. This includes all binary
490 /// comparisons (like `==` and `<`) and asserts.
492 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
493 /// clumsily written constant. Mostly this happens when someone accidentally
494 /// adds semicolons at the end of the operands.
496 /// **Known problems:** None.
527 /// assert_eq!({ foo(); }, { bar(); });
529 /// will always succeed
532 "comparing unit values"
535 declare_lint_pass!(UnitCmp => [UNIT_CMP]);
537 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
538 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
539 if expr.span.from_expansion() {
540 if let Some(callee) = expr.span.source_callee() {
541 if let ExpnKind::Macro(MacroKind::Bang, symbol) = callee.kind {
542 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
544 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
545 let result = match &*symbol.as_str() {
546 "assert_eq" | "debug_assert_eq" => "succeed",
547 "assert_ne" | "debug_assert_ne" => "fail",
555 "`{}` of unit values detected. This will always {}",
566 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
568 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
569 let result = match op {
570 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
578 "{}-comparison of unit values detected. This will always be {}",
588 declare_clippy_lint! {
589 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
590 /// unit literal (`()`).
592 /// **Why is this bad?** This is likely the result of an accidental semicolon.
594 /// **Known problems:** None.
605 "passing unit to a function"
608 declare_lint_pass!(UnitArg => [UNIT_ARG]);
610 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
611 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
612 if expr.span.from_expansion() {
616 // apparently stuff in the desugaring of `?` can trigger this
617 // so check for that here
618 // only the calls to `Try::from_error` is marked as desugared,
619 // so we need to check both the current Expr and its parent.
620 if is_questionmark_desugar_marked_call(expr) {
624 let map = &cx.tcx.hir();
625 let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
626 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
627 if is_questionmark_desugar_marked_call(parent_expr);
634 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
636 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
637 if let ExprKind::Match(.., match_source) = &arg.kind {
638 if *match_source == MatchSource::TryDesugar {
647 "passing a unit value to a function",
648 "if you intended to pass a unit value, use a unit literal instead",
650 Applicability::MachineApplicable,
660 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
661 use syntax_pos::hygiene::DesugaringKind;
662 if let ExprKind::Call(ref callee, _) = expr.kind {
663 callee.span.is_desugaring(DesugaringKind::QuestionMark)
669 fn is_unit(ty: Ty<'_>) -> bool {
671 ty::Tuple(slice) if slice.is_empty() => true,
676 fn is_unit_literal(expr: &Expr) -> bool {
678 ExprKind::Tup(ref slice) if slice.is_empty() => true,
683 declare_clippy_lint! {
684 /// **What it does:** Checks for casts from any numerical to a float type where
685 /// the receiving type cannot store all values from the original type without
686 /// rounding errors. This possible rounding is to be expected, so this lint is
687 /// `Allow` by default.
689 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
690 /// or any 64-bit integer to `f64`.
692 /// **Why is this bad?** It's not bad at all. But in some applications it can be
693 /// helpful to know where precision loss can take place. This lint can help find
694 /// those places in the code.
696 /// **Known problems:** None.
700 /// let x = std::u64::MAX;
703 pub CAST_PRECISION_LOSS,
705 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
708 declare_clippy_lint! {
709 /// **What it does:** Checks for casts from a signed to an unsigned numerical
710 /// type. In this case, negative values wrap around to large positive values,
711 /// which can be quite surprising in practice. However, as the cast works as
712 /// defined, this lint is `Allow` by default.
714 /// **Why is this bad?** Possibly surprising results. You can activate this lint
715 /// as a one-time check to see where numerical wrapping can arise.
717 /// **Known problems:** None.
722 /// y as u128; // will return 18446744073709551615
726 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
729 declare_clippy_lint! {
730 /// **What it does:** Checks for casts between numerical types that may
731 /// truncate large values. This is expected behavior, so the cast is `Allow` by
734 /// **Why is this bad?** In some problem domains, it is good practice to avoid
735 /// truncation. This lint can be activated to help assess where additional
736 /// checks could be beneficial.
738 /// **Known problems:** None.
742 /// fn as_u8(x: u64) -> u8 {
746 pub CAST_POSSIBLE_TRUNCATION,
748 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
751 declare_clippy_lint! {
752 /// **What it does:** Checks for casts from an unsigned type to a signed type of
753 /// the same size. Performing such a cast is a 'no-op' for the compiler,
754 /// i.e., nothing is changed at the bit level, and the binary representation of
755 /// the value is reinterpreted. This can cause wrapping if the value is too big
756 /// for the target signed type. However, the cast works as defined, so this lint
757 /// is `Allow` by default.
759 /// **Why is this bad?** While such a cast is not bad in itself, the results can
760 /// be surprising when this is not the intended behavior, as demonstrated by the
763 /// **Known problems:** None.
767 /// std::u32::MAX as i32; // will yield a value of `-1`
769 pub CAST_POSSIBLE_WRAP,
771 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
774 declare_clippy_lint! {
775 /// **What it does:** Checks for casts between numerical types that may
776 /// be replaced by safe conversion functions.
778 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
779 /// conversions, including silently lossy conversions. Conversion functions such
780 /// as `i32::from` will only perform lossless conversions. Using the conversion
781 /// functions prevents conversions from turning into silent lossy conversions if
782 /// the types of the input expressions ever change, and make it easier for
783 /// people reading the code to know that the conversion is lossless.
785 /// **Known problems:** None.
789 /// fn as_u64(x: u8) -> u64 {
794 /// Using `::from` would look like this:
797 /// fn as_u64(x: u8) -> u64 {
803 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
806 declare_clippy_lint! {
807 /// **What it does:** Checks for casts to the same type.
809 /// **Why is this bad?** It's just unnecessary.
811 /// **Known problems:** None.
815 /// let _ = 2i32 as i32;
817 pub UNNECESSARY_CAST,
819 "cast to the same type, e.g., `x as i32` where `x: i32`"
822 declare_clippy_lint! {
823 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
824 /// more-strictly-aligned pointer
826 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
829 /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
830 /// on the resulting pointer is fine.
834 /// let _ = (&1u8 as *const u8) as *const u16;
835 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
837 pub CAST_PTR_ALIGNMENT,
839 "cast from a pointer to a more-strictly-aligned pointer"
842 declare_clippy_lint! {
843 /// **What it does:** Checks for casts of function pointers to something other than usize
845 /// **Why is this bad?**
846 /// Casting a function pointer to anything other than usize/isize is not portable across
847 /// architectures, because you end up losing bits if the target type is too small or end up with a
848 /// bunch of extra bits that waste space and add more instructions to the final binary than
849 /// strictly necessary for the problem
851 /// Casting to isize also doesn't make sense since there are no signed addresses.
857 /// fn fun() -> i32 { 1 }
858 /// let a = fun as i64;
861 /// fn fun2() -> i32 { 1 }
862 /// let a = fun2 as usize;
864 pub FN_TO_NUMERIC_CAST,
866 "casting a function pointer to a numeric type other than usize"
869 declare_clippy_lint! {
870 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
873 /// **Why is this bad?**
874 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
875 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
876 /// a comment) to perform the truncation.
882 /// fn fn1() -> i16 {
885 /// let _ = fn1 as i32;
887 /// // Better: Cast to usize first, then comment with the reason for the truncation
888 /// fn fn2() -> i16 {
891 /// let fn_ptr = fn2 as usize;
892 /// let fn_ptr_truncated = fn_ptr as i32;
894 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
896 "casting a function pointer to a numeric type not wide enough to store the address"
899 /// Returns the size in bits of an integral type.
900 /// Will return 0 if the type is not an int or uint variant
901 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
903 ty::Int(i) => match i {
904 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
911 ty::Uint(i) => match i {
912 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
923 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
925 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
930 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
931 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
932 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
933 let arch_dependent_str = "on targets with 64-bit wide pointers ";
934 let from_nbits_str = if arch_dependent {
936 } else if is_isize_or_usize(cast_from) {
937 "32 or 64".to_owned()
939 int_ty_to_nbits(cast_from, cx.tcx).to_string()
946 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
947 is only {4} bits wide)",
949 if cast_to_f64 { "f64" } else { "f32" },
950 if arch_dependent { arch_dependent_str } else { "" },
957 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
958 if let ExprKind::Binary(_, _, _) = op.kind {
959 if snip.starts_with('(') && snip.ends_with(')') {
966 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
967 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
968 if in_constant(cx, expr.hir_id) {
971 // The suggestion is to use a function call, so if the original expression
972 // has parens on the outside, they are no longer needed.
973 let mut applicability = Applicability::MachineApplicable;
974 let opt = snippet_opt(cx, op.span);
975 let sugg = if let Some(ref snip) = opt {
976 if should_strip_parens(op, snip) {
977 &snip[1..snip.len() - 1]
982 applicability = Applicability::HasPlaceholders;
991 "casting {} to {} may become silently lossy if you later change the type",
995 format!("{}::from({})", cast_to, sugg),
1006 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1007 if !cast_from.is_signed() || cast_to.is_signed() {
1011 // don't lint for positive constants
1012 let const_val = constant(cx, &cx.tables, op);
1014 if let Some((const_val, _)) = const_val;
1015 if let Constant::Int(n) = const_val;
1016 if let ty::Int(ity) = cast_from.kind;
1017 if sext(cx.tcx, n, ity) >= 0;
1023 // don't lint for the result of `abs`
1024 // `abs` is an inherent impl of `i{N}`, so a method call with ident `abs` will always
1025 // resolve to that spesific method
1027 if let ExprKind::MethodCall(ref path, _, _) = op.kind;
1028 if path.ident.name.as_str() == "abs";
1038 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1042 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1043 let arch_64_suffix = " on targets with 64-bit wide pointers";
1044 let arch_32_suffix = " on targets with 32-bit wide pointers";
1045 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1046 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1047 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1048 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1049 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1050 (true, true) | (false, false) => (
1051 to_nbits < from_nbits,
1053 to_nbits == from_nbits && cast_unsigned_to_signed,
1063 to_nbits <= 32 && cast_unsigned_to_signed,
1069 cast_unsigned_to_signed,
1070 if from_nbits == 64 {
1077 if span_truncation {
1080 CAST_POSSIBLE_TRUNCATION,
1083 "casting {} to {} may truncate the value{}",
1086 match suffix_truncation {
1087 ArchSuffix::_32 => arch_32_suffix,
1088 ArchSuffix::_64 => arch_64_suffix,
1089 ArchSuffix::None => "",
1100 "casting {} to {} may wrap around the value{}",
1104 ArchSuffix::_32 => arch_32_suffix,
1105 ArchSuffix::_64 => arch_64_suffix,
1106 ArchSuffix::None => "",
1113 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1114 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1115 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1116 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1117 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1119 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1123 declare_lint_pass!(Casts => [
1124 CAST_PRECISION_LOSS,
1126 CAST_POSSIBLE_TRUNCATION,
1132 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1135 // Check if the given type is either `core::ffi::c_void` or
1136 // one of the platform specific `libc::<platform>::c_void` of libc.
1137 fn is_c_void(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1138 if let ty::Adt(adt, _) = ty.kind {
1139 let names = cx.get_def_path(adt.did);
1141 if names.is_empty() {
1144 if names[0] == sym!(libc) || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
1151 /// Returns the mantissa bits wide of a fp type.
1152 /// Will return 0 if the type is not a fp
1153 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1155 ty::Float(FloatTy::F32) => 23,
1156 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1161 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
1162 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1163 if expr.span.from_expansion() {
1166 if let ExprKind::Cast(ref ex, _) = expr.kind {
1167 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1168 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1169 if let ExprKind::Lit(ref lit) = ex.kind {
1170 if let LitKind::Int(n, _) = lit.node {
1171 if cast_to.is_floating_point() {
1172 let from_nbits = 128 - n.leading_zeros();
1173 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1174 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1179 &format!("casting integer literal to {} is unnecessary", cast_to),
1181 format!("{}_{}", n, cast_to),
1182 Applicability::MachineApplicable,
1189 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
1191 if cast_from.kind == cast_to.kind && !in_external_macro(cx.sess(), expr.span) {
1197 "casting to the same type is unnecessary (`{}` -> `{}`)",
1205 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1206 lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
1209 lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
1214 fn lint_numeric_casts<'tcx>(
1215 cx: &LateContext<'_, 'tcx>,
1218 cast_from: Ty<'tcx>,
1221 match (cast_from.is_integral(), cast_to.is_integral()) {
1223 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1224 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind {
1229 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1230 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1232 if from_nbits < to_nbits {
1233 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1239 CAST_POSSIBLE_TRUNCATION,
1241 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1243 if !cast_to.is_signed() {
1248 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1253 check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
1254 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1255 check_lossless(cx, expr, cast_expr, cast_from, cast_to);
1258 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.kind, &cast_to.kind) {
1261 CAST_POSSIBLE_TRUNCATION,
1263 "casting f64 to f32 may truncate the value",
1266 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.kind, &cast_to.kind) {
1267 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1273 fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
1275 if let ty::RawPtr(from_ptr_ty) = &cast_from.kind;
1276 if let ty::RawPtr(to_ptr_ty) = &cast_to.kind;
1277 if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
1278 if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
1279 if from_layout.align.abi < to_layout.align.abi;
1280 // with c_void, we inherently need to trust the user
1281 if !is_c_void(cx, from_ptr_ty.ty);
1282 // when casting from a ZST, we don't know enough to properly lint
1283 if !from_layout.is_zst();
1290 "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
1293 from_layout.align.abi.bytes(),
1294 to_layout.align.abi.bytes(),
1301 fn lint_fn_to_numeric_cast(
1302 cx: &LateContext<'_, '_>,
1308 // We only want to check casts to `ty::Uint` or `ty::Int`
1309 match cast_to.kind {
1310 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1313 match cast_from.kind {
1314 ty::FnDef(..) | ty::FnPtr(_) => {
1315 let mut applicability = Applicability::MaybeIncorrect;
1316 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1318 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1319 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1322 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1325 "casting function pointer `{}` to `{}`, which truncates the value",
1326 from_snippet, cast_to
1329 format!("{} as usize", from_snippet),
1332 } else if cast_to.kind != ty::Uint(UintTy::Usize) {
1337 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1339 format!("{} as usize", from_snippet),
1348 declare_clippy_lint! {
1349 /// **What it does:** Checks for types used in structs, parameters and `let`
1350 /// declarations above a certain complexity threshold.
1352 /// **Why is this bad?** Too complex types make the code less readable. Consider
1353 /// using a `type` definition to simplify them.
1355 /// **Known problems:** None.
1359 /// # use std::rc::Rc;
1361 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1364 pub TYPE_COMPLEXITY,
1366 "usage of very complex types that might be better factored into `type` definitions"
1369 pub struct TypeComplexity {
1373 impl TypeComplexity {
1375 pub fn new(threshold: u64) -> Self {
1380 impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
1382 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexity {
1385 cx: &LateContext<'a, 'tcx>,
1392 self.check_fndecl(cx, decl);
1395 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1396 // enum variants are also struct fields now
1397 self.check_type(cx, &field.ty);
1400 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1402 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1403 // functions, enums, structs, impls and traits are covered
1408 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1410 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1411 TraitItemKind::Method(FnSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1412 // methods with default impl are covered by check_fn
1417 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1419 ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
1420 // methods are covered by check_fn
1425 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1426 if let Some(ref ty) = local.ty {
1427 self.check_type(cx, ty);
1432 impl<'a, 'tcx> TypeComplexity {
1433 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1434 for arg in &decl.inputs {
1435 self.check_type(cx, arg);
1437 if let Return(ref ty) = decl.output {
1438 self.check_type(cx, ty);
1442 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1443 if ty.span.from_expansion() {
1447 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1448 visitor.visit_ty(ty);
1452 if score > self.threshold {
1457 "very complex type used. Consider factoring parts into `type` definitions",
1463 /// Walks a type and assigns a complexity score to it.
1464 struct TypeComplexityVisitor {
1465 /// total complexity score of the type
1467 /// current nesting level
1471 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1472 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1473 let (add_score, sub_nest) = match ty.kind {
1474 // _, &x and *x have only small overhead; don't mess with nesting level
1475 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1477 // the "normal" components of a type: named types, arrays/tuples
1478 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1480 // function types bring a lot of overhead
1481 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1483 TyKind::TraitObject(ref param_bounds, _) => {
1484 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1485 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1486 GenericParamKind::Lifetime { .. } => true,
1490 if has_lifetime_parameters {
1491 // complex trait bounds like A<'a, 'b>
1494 // simple trait bounds like A + B
1501 self.score += add_score;
1502 self.nest += sub_nest;
1504 self.nest -= sub_nest;
1506 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1507 NestedVisitorMap::None
1511 declare_clippy_lint! {
1512 /// **What it does:** Checks for expressions where a character literal is cast
1513 /// to `u8` and suggests using a byte literal instead.
1515 /// **Why is this bad?** In general, casting values to smaller types is
1516 /// error-prone and should be avoided where possible. In the particular case of
1517 /// converting a character literal to u8, it is easy to avoid by just using a
1518 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1519 /// than `'a' as u8`.
1521 /// **Known problems:** None.
1528 /// A better version, using the byte literal:
1535 "casting a character literal to u8 truncates"
1538 declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
1540 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1541 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1543 if !expr.span.from_expansion();
1544 if let ExprKind::Cast(e, _) = &expr.kind;
1545 if let ExprKind::Lit(l) = &e.kind;
1546 if let LitKind::Char(c) = l.node;
1547 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).kind;
1549 let mut applicability = Applicability::MachineApplicable;
1550 let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
1556 "casting a character literal to `u8` truncates",
1558 db.note("`char` is four bytes wide, but `u8` is a single byte");
1563 "use a byte literal instead",
1564 format!("b{}", snippet),
1574 declare_clippy_lint! {
1575 /// **What it does:** Checks for comparisons where one side of the relation is
1576 /// either the minimum or maximum value for its type and warns if it involves a
1577 /// case that is always true or always false. Only integer and boolean types are
1580 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1581 /// that it is possible for `x` to be less than the minimum. Expressions like
1582 /// `max < x` are probably mistakes.
1584 /// **Known problems:** For `usize` the size of the current compile target will
1585 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1586 /// a comparison to detect target pointer width will trigger this lint. One can
1587 /// use `mem::sizeof` and compare its value or conditional compilation
1589 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1594 /// let vec: Vec<isize> = vec![];
1595 /// if vec.len() <= 0 {}
1596 /// if 100 > std::i32::MAX {}
1598 pub ABSURD_EXTREME_COMPARISONS,
1600 "a comparison with a maximum or minimum value that is always true or false"
1603 declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
1610 struct ExtremeExpr<'a> {
1615 enum AbsurdComparisonResult {
1618 InequalityImpossible,
1621 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1622 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1623 let precast_ty = cx.tables.expr_ty(cast_exp);
1624 let cast_ty = cx.tables.expr_ty(expr);
1626 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1632 fn detect_absurd_comparison<'a, 'tcx>(
1633 cx: &LateContext<'a, 'tcx>,
1637 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1638 use crate::types::AbsurdComparisonResult::*;
1639 use crate::types::ExtremeType::*;
1640 use crate::utils::comparisons::*;
1642 // absurd comparison only makes sense on primitive types
1643 // primitive types don't implement comparison operators with each other
1644 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1648 // comparisons between fix sized types and target sized types are considered unanalyzable
1649 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1653 let normalized = normalize_comparison(op, lhs, rhs);
1654 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1660 let lx = detect_extreme_expr(cx, normalized_lhs);
1661 let rx = detect_extreme_expr(cx, normalized_rhs);
1666 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1667 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1673 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1674 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1675 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1676 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1680 Rel::Ne | Rel::Eq => return None,
1684 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1685 use crate::types::ExtremeType::*;
1687 let ty = cx.tables.expr_ty(expr);
1689 let cv = constant(cx, cx.tables, expr)?.0;
1691 let which = match (&ty.kind, cv) {
1692 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1693 (&ty::Int(ity), Constant::Int(i))
1694 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1699 (&ty::Bool, Constant::Bool(true)) => Maximum,
1700 (&ty::Int(ity), Constant::Int(i))
1701 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1705 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1709 Some(ExtremeExpr { which, expr })
1712 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1713 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1714 use crate::types::AbsurdComparisonResult::*;
1715 use crate::types::ExtremeType::*;
1717 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
1718 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1719 if !expr.span.from_expansion() {
1720 let msg = "this comparison involving the minimum or maximum element for this \
1721 type contains a case that is always true or always false";
1723 let conclusion = match result {
1724 AlwaysFalse => "this comparison is always false".to_owned(),
1725 AlwaysTrue => "this comparison is always true".to_owned(),
1726 InequalityImpossible => format!(
1727 "the case where the two sides are not equal never occurs, consider using {} == {} \
1729 snippet(cx, lhs.span, "lhs"),
1730 snippet(cx, rhs.span, "rhs")
1735 "because {} is the {} value for this type, {}",
1736 snippet(cx, culprit.expr.span, "x"),
1737 match culprit.which {
1738 Minimum => "minimum",
1739 Maximum => "maximum",
1744 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1751 declare_clippy_lint! {
1752 /// **What it does:** Checks for comparisons where the relation is always either
1753 /// true or false, but where one side has been upcast so that the comparison is
1754 /// necessary. Only integer types are checked.
1756 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1757 /// will mistakenly imply that it is possible for `x` to be outside the range of
1760 /// **Known problems:**
1761 /// https://github.com/rust-lang/rust-clippy/issues/886
1766 /// (x as u32) > 300;
1768 pub INVALID_UPCAST_COMPARISONS,
1770 "a comparison involving an upcast which is always true or false"
1773 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
1775 #[derive(Copy, Clone, Debug, Eq)]
1782 #[allow(clippy::cast_sign_loss)]
1784 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1787 } else if u > (i128::max_value() as u128) {
1795 impl PartialEq for FullInt {
1797 fn eq(&self, other: &Self) -> bool {
1798 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1802 impl PartialOrd for FullInt {
1804 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1805 Some(match (self, other) {
1806 (&Self::S(s), &Self::S(o)) => s.cmp(&o),
1807 (&Self::U(s), &Self::U(o)) => s.cmp(&o),
1808 (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
1809 (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
1813 impl Ord for FullInt {
1815 fn cmp(&self, other: &Self) -> Ordering {
1816 self.partial_cmp(other)
1817 .expect("partial_cmp for FullInt can never return None")
1821 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1824 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1825 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1826 let cast_ty = cx.tables.expr_ty(expr);
1827 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1828 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1831 match pre_cast_ty.kind {
1832 ty::Int(int_ty) => Some(match int_ty {
1834 FullInt::S(i128::from(i8::min_value())),
1835 FullInt::S(i128::from(i8::max_value())),
1838 FullInt::S(i128::from(i16::min_value())),
1839 FullInt::S(i128::from(i16::max_value())),
1842 FullInt::S(i128::from(i32::min_value())),
1843 FullInt::S(i128::from(i32::max_value())),
1846 FullInt::S(i128::from(i64::min_value())),
1847 FullInt::S(i128::from(i64::max_value())),
1849 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1851 FullInt::S(isize::min_value() as i128),
1852 FullInt::S(isize::max_value() as i128),
1855 ty::Uint(uint_ty) => Some(match uint_ty {
1857 FullInt::U(u128::from(u8::min_value())),
1858 FullInt::U(u128::from(u8::max_value())),
1861 FullInt::U(u128::from(u16::min_value())),
1862 FullInt::U(u128::from(u16::max_value())),
1865 FullInt::U(u128::from(u32::min_value())),
1866 FullInt::U(u128::from(u32::max_value())),
1869 FullInt::U(u128::from(u64::min_value())),
1870 FullInt::U(u128::from(u64::max_value())),
1872 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1874 FullInt::U(usize::min_value() as u128),
1875 FullInt::U(usize::max_value() as u128),
1885 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1886 let val = constant(cx, cx.tables, expr)?.0;
1887 if let Constant::Int(const_int) = val {
1888 match cx.tables.expr_ty(expr).kind {
1889 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1890 ty::Uint(_) => Some(FullInt::U(const_int)),
1898 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1899 if let ExprKind::Cast(ref cast_val, _) = expr.kind {
1902 INVALID_UPCAST_COMPARISONS,
1905 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1906 snippet(cx, cast_val.span, "the expression"),
1907 if always { "true" } else { "false" },
1913 fn upcast_comparison_bounds_err<'a, 'tcx>(
1914 cx: &LateContext<'a, 'tcx>,
1916 rel: comparisons::Rel,
1917 lhs_bounds: Option<(FullInt, FullInt)>,
1922 use crate::utils::comparisons::*;
1924 if let Some((lb, ub)) = lhs_bounds {
1925 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1926 if rel == Rel::Eq || rel == Rel::Ne {
1927 if norm_rhs_val < lb || norm_rhs_val > ub {
1928 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1930 } else if match rel {
1945 Rel::Eq | Rel::Ne => unreachable!(),
1947 err_upcast_comparison(cx, span, lhs, true)
1948 } else if match rel {
1963 Rel::Eq | Rel::Ne => unreachable!(),
1965 err_upcast_comparison(cx, span, lhs, false)
1971 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1972 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1973 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
1974 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1975 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1981 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1982 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1984 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1985 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1990 declare_clippy_lint! {
1991 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1992 /// over different hashers and implicitly defaulting to the default hashing
1993 /// algorithm (`SipHash`).
1995 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1998 /// **Known problems:** Suggestions for replacing constructors can contain
1999 /// false-positives. Also applying suggestions can require modification of other
2000 /// pieces of code, possibly including external crates.
2004 /// # use std::collections::HashMap;
2005 /// # use std::hash::{Hash, BuildHasher};
2006 /// # trait Serialize {};
2007 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
2009 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
2011 /// could be rewritten as
2013 /// # use std::collections::HashMap;
2014 /// # use std::hash::{Hash, BuildHasher};
2015 /// # trait Serialize {};
2016 /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
2018 /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
2020 pub IMPLICIT_HASHER,
2022 "missing generalization over different hashers"
2025 declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
2027 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
2028 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
2029 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
2030 use syntax_pos::BytePos;
2032 fn suggestion<'a, 'tcx>(
2033 cx: &LateContext<'a, 'tcx>,
2034 db: &mut DiagnosticBuilder<'_>,
2035 generics_span: Span,
2036 generics_suggestion_span: Span,
2037 target: &ImplicitHasherType<'_>,
2038 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2040 let generics_snip = snippet(cx, generics_span, "");
2042 let generics_snip = if generics_snip.is_empty() {
2045 &generics_snip[1..generics_snip.len() - 1]
2050 "consider adding a type parameter".to_string(),
2053 generics_suggestion_span,
2055 "<{}{}S: ::std::hash::BuildHasher{}>",
2057 if generics_snip.is_empty() { "" } else { ", " },
2058 if vis.suggestions.is_empty() {
2061 // request users to add `Default` bound so that generic constructors can be used
2068 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2073 if !vis.suggestions.is_empty() {
2074 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2078 if !cx.access_levels.is_exported(item.hir_id) {
2083 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2084 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2087 for target in &vis.found {
2088 if differing_macro_contexts(item.span, target.span()) {
2092 let generics_suggestion_span = generics.span.substitute_dummy({
2093 let pos = snippet_opt(cx, item.span.until(target.span()))
2094 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2095 if let Some(pos) = pos {
2096 Span::new(pos, pos, item.span.data().ctxt)
2102 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2103 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2104 ctr_vis.visit_impl_item(item);
2112 "impl for `{}` should be generalized over different hashers",
2116 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2121 ItemKind::Fn(ref sig, ref generics, body_id) => {
2122 let body = cx.tcx.hir().body(body_id);
2124 for ty in &sig.decl.inputs {
2125 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2128 for target in &vis.found {
2129 if in_external_macro(cx.sess(), generics.span) {
2132 let generics_suggestion_span = generics.span.substitute_dummy({
2133 let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
2135 let i = snip.find("fn")?;
2136 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2138 .expect("failed to create span for type parameters");
2139 Span::new(pos, pos, item.span.data().ctxt)
2142 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2143 ctr_vis.visit_body(body);
2150 "parameter of type `{}` should be generalized over different hashers",
2154 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2165 enum ImplicitHasherType<'tcx> {
2166 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2167 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2170 impl<'tcx> ImplicitHasherType<'tcx> {
2171 /// Checks that `ty` is a target type without a `BuildHasher`.
2172 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2173 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.kind {
2174 let params: Vec<_> = path
2182 .filter_map(|arg| match arg {
2183 GenericArg::Type(ty) => Some(ty),
2187 let params_len = params.len();
2189 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2191 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2192 Some(ImplicitHasherType::HashMap(
2195 snippet(cx, params[0].span, "K"),
2196 snippet(cx, params[1].span, "V"),
2198 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2199 Some(ImplicitHasherType::HashSet(
2202 snippet(cx, params[0].span, "T"),
2212 fn type_name(&self) -> &'static str {
2214 ImplicitHasherType::HashMap(..) => "HashMap",
2215 ImplicitHasherType::HashSet(..) => "HashSet",
2219 fn type_arguments(&self) -> String {
2221 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2222 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2226 fn ty(&self) -> Ty<'tcx> {
2228 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2232 fn span(&self) -> Span {
2234 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2239 struct ImplicitHasherTypeVisitor<'a, 'tcx> {
2240 cx: &'a LateContext<'a, 'tcx>,
2241 found: Vec<ImplicitHasherType<'tcx>>,
2244 impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
2245 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2246 Self { cx, found: vec![] }
2250 impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2251 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2252 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2253 self.found.push(target);
2259 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2260 NestedVisitorMap::None
2264 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2265 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2266 cx: &'a LateContext<'a, 'tcx>,
2267 body: &'a TypeckTables<'tcx>,
2268 target: &'b ImplicitHasherType<'tcx>,
2269 suggestions: BTreeMap<Span, String>,
2272 impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2273 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2278 suggestions: BTreeMap::new(),
2283 impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2284 fn visit_body(&mut self, body: &'tcx Body) {
2285 let prev_body = self.body;
2286 self.body = self.cx.tcx.body_tables(body.id());
2287 walk_body(self, body);
2288 self.body = prev_body;
2291 fn visit_expr(&mut self, e: &'tcx Expr) {
2293 if let ExprKind::Call(ref fun, ref args) = e.kind;
2294 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.kind;
2295 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.kind;
2297 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2301 if match_path(ty_path, &paths::HASHMAP) {
2302 if method.ident.name == sym!(new) {
2304 .insert(e.span, "HashMap::default()".to_string());
2305 } else if method.ident.name == sym!(with_capacity) {
2306 self.suggestions.insert(
2309 "HashMap::with_capacity_and_hasher({}, Default::default())",
2310 snippet(self.cx, args[0].span, "capacity"),
2314 } else if match_path(ty_path, &paths::HASHSET) {
2315 if method.ident.name == sym!(new) {
2317 .insert(e.span, "HashSet::default()".to_string());
2318 } else if method.ident.name == sym!(with_capacity) {
2319 self.suggestions.insert(
2322 "HashSet::with_capacity_and_hasher({}, Default::default())",
2323 snippet(self.cx, args[0].span, "capacity"),
2334 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2335 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2339 declare_clippy_lint! {
2340 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2342 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2343 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2346 /// **Known problems:** None.
2352 /// *(r as *const _ as *mut _) += 1;
2357 /// Instead consider using interior mutability types.
2360 /// use std::cell::UnsafeCell;
2362 /// fn x(r: &UnsafeCell<i32>) {
2368 pub CAST_REF_TO_MUT,
2370 "a cast of reference to a mutable pointer"
2373 declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
2375 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2376 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2378 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.kind;
2379 if let ExprKind::Cast(e, t) = &e.kind;
2380 if let TyKind::Ptr(MutTy { mutbl: Mutability::Mutable, .. }) = t.kind;
2381 if let ExprKind::Cast(e, t) = &e.kind;
2382 if let TyKind::Ptr(MutTy { mutbl: Mutability::Immutable, .. }) = t.kind;
2383 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).kind;
2389 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",