1 #![allow(rustc::default_hash_types)]
4 use std::cmp::Ordering;
5 use std::collections::BTreeMap;
7 use if_chain::if_chain;
8 use rustc::hir::map::Map;
9 use rustc::lint::in_external_macro;
10 use rustc::ty::layout::LayoutOf;
11 use rustc::ty::{self, InferTy, Ty, TyCtxt, TypeckTables};
12 use rustc_ast::ast::{FloatTy, IntTy, LitFloatType, LitIntType, LitKind, UintTy};
13 use rustc_errors::{Applicability, DiagnosticBuilder};
15 use rustc_hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
17 BinOpKind, Body, Expr, ExprKind, FnDecl, FnRetTy, FnSig, GenericArg, GenericParamKind, HirId, ImplItem,
18 ImplItemKind, Item, ItemKind, Lifetime, Local, MatchSource, MutTy, Mutability, QPath, Stmt, StmtKind, TraitItem,
19 TraitItemKind, TraitMethod, TyKind, UnOp,
21 use rustc_lint::{LateContext, LateLintPass, LintContext};
22 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
23 use rustc_span::hygiene::{ExpnKind, MacroKind};
24 use rustc_span::source_map::Span;
25 use rustc_span::symbol::{sym, Symbol};
26 use rustc_target::spec::abi::Abi;
27 use rustc_typeck::hir_ty_to_ty;
29 use crate::consts::{constant, Constant};
30 use crate::utils::paths;
32 clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
33 match_path, method_chain_args, multispan_sugg, numeric_literal::NumericLiteral, qpath_res, same_tys, sext, snippet,
34 snippet_opt, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_help,
35 span_lint_and_sugg, span_lint_and_then, unsext,
38 declare_clippy_lint! {
39 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
41 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
42 /// the heap. So if you `Box` it, you just add another level of indirection
43 /// without any benefit whatsoever.
45 /// **Known problems:** None.
50 /// values: Box<Vec<Foo>>,
63 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
66 declare_clippy_lint! {
67 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
69 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
70 /// the heap. So if you `Box` its contents, you just add another level of indirection.
72 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
78 /// values: Vec<Box<i32>>,
91 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
94 declare_clippy_lint! {
95 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
98 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
99 /// represents an optional optional value which is logically the same thing as an optional
100 /// value but has an unneeded extra level of wrapping.
102 /// **Known problems:** None.
106 /// fn x() -> Option<Option<u32>> {
112 "usage of `Option<Option<T>>`"
115 declare_clippy_lint! {
116 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
117 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
119 /// **Why is this bad?** Gankro says:
121 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
122 /// pointers and indirection.
123 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
125 /// > "only" amortized for push/pop, should be faster in the general case for
126 /// almost every possible
127 /// > workload, and isn't even amortized at all if you can predict the capacity
130 /// > `LinkedList`s are only really good if you're doing a lot of merging or
131 /// splitting of lists.
132 /// > This is because they can just mangle some pointers instead of actually
133 /// copying the data. Even
134 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
135 /// can still be better
136 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
138 /// **Known problems:** False positives – the instances where using a
139 /// `LinkedList` makes sense are few and far between, but they can still happen.
143 /// # use std::collections::LinkedList;
144 /// let x: LinkedList<usize> = LinkedList::new();
148 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a `VecDeque`"
151 declare_clippy_lint! {
152 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
154 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
157 /// **Known problems:** None.
161 /// fn foo(bar: &Box<T>) { ... }
167 /// fn foo(bar: &T) { ... }
171 "a borrow of a boxed type"
175 vec_box_size_threshold: u64,
178 impl_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX]);
180 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Types {
183 cx: &LateContext<'_, '_>,
190 // Skip trait implementations; see issue #605.
191 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
192 if let ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
197 self.check_fn_decl(cx, decl);
200 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
201 self.check_ty(cx, &field.ty, false);
204 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem<'_>) {
206 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_ty(cx, ty, false),
207 TraitItemKind::Fn(ref sig, _) => self.check_fn_decl(cx, &sig.decl),
212 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local<'_>) {
213 if let Some(ref ty) = local.ty {
214 self.check_ty(cx, ty, true);
219 /// Checks if `qpath` has last segment with type parameter matching `path`
220 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath<'_>, path: &[&str]) -> bool {
221 let last = last_path_segment(qpath);
223 if let Some(ref params) = last.args;
224 if !params.parenthesized;
225 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
226 GenericArg::Type(ty) => Some(ty),
229 if let TyKind::Path(ref qpath) = ty.kind;
230 if let Some(did) = qpath_res(cx, qpath, ty.hir_id).opt_def_id();
231 if match_def_path(cx, did, path);
240 pub fn new(vec_box_size_threshold: u64) -> Self {
241 Self { vec_box_size_threshold }
244 fn check_fn_decl(&mut self, cx: &LateContext<'_, '_>, decl: &FnDecl<'_>) {
245 for input in decl.inputs {
246 self.check_ty(cx, input, false);
249 if let FnRetTy::Return(ref ty) = decl.output {
250 self.check_ty(cx, ty, false);
254 /// Recursively check for `TypePass` lints in the given type. Stop at the first
257 /// The parameter `is_local` distinguishes the context of the type; types from
258 /// local bindings should only be checked for the `BORROWED_BOX` lint.
259 #[allow(clippy::too_many_lines)]
260 fn check_ty(&mut self, cx: &LateContext<'_, '_>, hir_ty: &hir::Ty<'_>, is_local: bool) {
261 if hir_ty.span.from_expansion() {
265 TyKind::Path(ref qpath) if !is_local => {
266 let hir_id = hir_ty.hir_id;
267 let res = qpath_res(cx, qpath, hir_id);
268 if let Some(def_id) = res.opt_def_id() {
269 if Some(def_id) == cx.tcx.lang_items().owned_box() {
270 if match_type_parameter(cx, qpath, &paths::VEC) {
275 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
276 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
278 return; // don't recurse into the type
280 } else if cx.tcx.is_diagnostic_item(Symbol::intern("vec_type"), def_id) {
282 // Get the _ part of Vec<_>
283 if let Some(ref last) = last_path_segment(qpath).args;
284 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
285 GenericArg::Type(ty) => Some(ty),
288 // ty is now _ at this point
289 if let TyKind::Path(ref ty_qpath) = ty.kind;
290 let res = qpath_res(cx, ty_qpath, ty.hir_id);
291 if let Some(def_id) = res.opt_def_id();
292 if Some(def_id) == cx.tcx.lang_items().owned_box();
293 // At this point, we know ty is Box<T>, now get T
294 if let Some(ref last) = last_path_segment(ty_qpath).args;
295 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
296 GenericArg::Type(ty) => Some(ty),
299 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
300 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env);
301 if let Ok(ty_ty_size) = cx.layout_of(ty_ty).map(|l| l.size.bytes());
302 if ty_ty_size <= self.vec_box_size_threshold;
308 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
310 format!("Vec<{}>", ty_ty),
311 Applicability::MachineApplicable,
313 return; // don't recurse into the type
316 } else if match_def_path(cx, def_id, &paths::OPTION) {
317 if match_type_parameter(cx, qpath, &paths::OPTION) {
322 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
323 enum if you need to distinguish all 3 cases",
325 return; // don't recurse into the type
327 } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
332 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
333 "a `VecDeque` might work",
335 return; // don't recurse into the type
339 QPath::Resolved(Some(ref ty), ref p) => {
340 self.check_ty(cx, ty, is_local);
341 for ty in p.segments.iter().flat_map(|seg| {
344 .map_or_else(|| [].iter(), |params| params.args.iter())
345 .filter_map(|arg| match arg {
346 GenericArg::Type(ty) => Some(ty),
350 self.check_ty(cx, ty, is_local);
353 QPath::Resolved(None, ref p) => {
354 for ty in p.segments.iter().flat_map(|seg| {
357 .map_or_else(|| [].iter(), |params| params.args.iter())
358 .filter_map(|arg| match arg {
359 GenericArg::Type(ty) => Some(ty),
363 self.check_ty(cx, ty, is_local);
366 QPath::TypeRelative(ref ty, ref seg) => {
367 self.check_ty(cx, ty, is_local);
368 if let Some(ref params) = seg.args {
369 for ty in params.args.iter().filter_map(|arg| match arg {
370 GenericArg::Type(ty) => Some(ty),
373 self.check_ty(cx, ty, is_local);
379 TyKind::Rptr(ref lt, ref mut_ty) => self.check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
381 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
382 self.check_ty(cx, ty, is_local)
384 TyKind::Tup(tys) => {
386 self.check_ty(cx, ty, is_local);
395 cx: &LateContext<'_, '_>,
396 hir_ty: &hir::Ty<'_>,
401 match mut_ty.ty.kind {
402 TyKind::Path(ref qpath) => {
403 let hir_id = mut_ty.ty.hir_id;
404 let def = qpath_res(cx, qpath, hir_id);
406 if let Some(def_id) = def.opt_def_id();
407 if Some(def_id) == cx.tcx.lang_items().owned_box();
408 if let QPath::Resolved(None, ref path) = *qpath;
409 if let [ref bx] = *path.segments;
410 if let Some(ref params) = bx.args;
411 if !params.parenthesized;
412 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
413 GenericArg::Type(ty) => Some(ty),
417 if is_any_trait(inner) {
418 // Ignore `Box<Any>` types; see issue #1884 for details.
422 let ltopt = if lt.is_elided() {
425 format!("{} ", lt.name.ident().as_str())
427 let mutopt = if mut_ty.mutbl == Mutability::Mut {
432 let mut applicability = Applicability::MachineApplicable;
437 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
443 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
445 Applicability::Unspecified,
447 return; // don't recurse into the type
450 self.check_ty(cx, &mut_ty.ty, is_local);
452 _ => self.check_ty(cx, &mut_ty.ty, is_local),
457 // Returns true if given type is `Any` trait.
458 fn is_any_trait(t: &hir::Ty<'_>) -> bool {
460 if let TyKind::TraitObject(ref traits, _) = t.kind;
461 if !traits.is_empty();
462 // Only Send/Sync can be used as additional traits, so it is enough to
463 // check only the first trait.
464 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
473 declare_clippy_lint! {
474 /// **What it does:** Checks for binding a unit value.
476 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
477 /// binding one is kind of pointless.
479 /// **Known problems:** None.
489 "creating a `let` binding to a value of unit type, which usually can't be used afterwards"
492 declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
494 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnitValue {
495 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt<'_>) {
496 if let StmtKind::Local(ref local) = stmt.kind {
497 if is_unit(cx.tables.pat_ty(&local.pat)) {
498 if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
501 if higher::is_from_for_desugar(local) {
504 span_lint_and_then(cx, LET_UNIT_VALUE, stmt.span, "this let-binding has unit value", |db| {
505 if let Some(expr) = &local.init {
506 let snip = snippet_with_macro_callsite(cx, expr.span, "()");
509 "omit the `let` binding",
510 format!("{};", snip),
511 Applicability::MachineApplicable, // snippet
520 declare_clippy_lint! {
521 /// **What it does:** Checks for comparisons to unit. This includes all binary
522 /// comparisons (like `==` and `<`) and asserts.
524 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
525 /// clumsily written constant. Mostly this happens when someone accidentally
526 /// adds semicolons at the end of the operands.
528 /// **Known problems:** None.
559 /// assert_eq!({ foo(); }, { bar(); });
561 /// will always succeed
564 "comparing unit values"
567 declare_lint_pass!(UnitCmp => [UNIT_CMP]);
569 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
570 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) {
571 if expr.span.from_expansion() {
572 if let Some(callee) = expr.span.source_callee() {
573 if let ExpnKind::Macro(MacroKind::Bang, symbol) = callee.kind {
574 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
576 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
577 let result = match &*symbol.as_str() {
578 "assert_eq" | "debug_assert_eq" => "succeed",
579 "assert_ne" | "debug_assert_ne" => "fail",
587 "`{}` of unit values detected. This will always {}",
598 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
600 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
601 let result = match op {
602 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
610 "{}-comparison of unit values detected. This will always be {}",
620 declare_clippy_lint! {
621 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
622 /// unit literal (`()`).
624 /// **Why is this bad?** This is likely the result of an accidental semicolon.
626 /// **Known problems:** None.
637 "passing unit to a function"
640 declare_lint_pass!(UnitArg => [UNIT_ARG]);
642 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
643 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
644 if expr.span.from_expansion() {
648 // apparently stuff in the desugaring of `?` can trigger this
649 // so check for that here
650 // only the calls to `Try::from_error` is marked as desugared,
651 // so we need to check both the current Expr and its parent.
652 if is_questionmark_desugar_marked_call(expr) {
656 let map = &cx.tcx.hir();
657 let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
658 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
659 if is_questionmark_desugar_marked_call(parent_expr);
666 ExprKind::Call(_, args) | ExprKind::MethodCall(_, _, args) => {
668 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
669 if let ExprKind::Match(.., match_source) = &arg.kind {
670 if *match_source == MatchSource::TryDesugar {
679 "passing a unit value to a function",
680 "if you intended to pass a unit value, use a unit literal instead",
682 Applicability::MachineApplicable,
692 fn is_questionmark_desugar_marked_call(expr: &Expr<'_>) -> bool {
693 use rustc_span::hygiene::DesugaringKind;
694 if let ExprKind::Call(ref callee, _) = expr.kind {
695 callee.span.is_desugaring(DesugaringKind::QuestionMark)
701 fn is_unit(ty: Ty<'_>) -> bool {
703 ty::Tuple(slice) if slice.is_empty() => true,
708 fn is_unit_literal(expr: &Expr<'_>) -> bool {
710 ExprKind::Tup(ref slice) if slice.is_empty() => true,
715 declare_clippy_lint! {
716 /// **What it does:** Checks for casts from any numerical to a float type where
717 /// the receiving type cannot store all values from the original type without
718 /// rounding errors. This possible rounding is to be expected, so this lint is
719 /// `Allow` by default.
721 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
722 /// or any 64-bit integer to `f64`.
724 /// **Why is this bad?** It's not bad at all. But in some applications it can be
725 /// helpful to know where precision loss can take place. This lint can help find
726 /// those places in the code.
728 /// **Known problems:** None.
732 /// let x = std::u64::MAX;
735 pub CAST_PRECISION_LOSS,
737 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
740 declare_clippy_lint! {
741 /// **What it does:** Checks for casts from a signed to an unsigned numerical
742 /// type. In this case, negative values wrap around to large positive values,
743 /// which can be quite surprising in practice. However, as the cast works as
744 /// defined, this lint is `Allow` by default.
746 /// **Why is this bad?** Possibly surprising results. You can activate this lint
747 /// as a one-time check to see where numerical wrapping can arise.
749 /// **Known problems:** None.
754 /// y as u128; // will return 18446744073709551615
758 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
761 declare_clippy_lint! {
762 /// **What it does:** Checks for casts between numerical types that may
763 /// truncate large values. This is expected behavior, so the cast is `Allow` by
766 /// **Why is this bad?** In some problem domains, it is good practice to avoid
767 /// truncation. This lint can be activated to help assess where additional
768 /// checks could be beneficial.
770 /// **Known problems:** None.
774 /// fn as_u8(x: u64) -> u8 {
778 pub CAST_POSSIBLE_TRUNCATION,
780 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
783 declare_clippy_lint! {
784 /// **What it does:** Checks for casts from an unsigned type to a signed type of
785 /// the same size. Performing such a cast is a 'no-op' for the compiler,
786 /// i.e., nothing is changed at the bit level, and the binary representation of
787 /// the value is reinterpreted. This can cause wrapping if the value is too big
788 /// for the target signed type. However, the cast works as defined, so this lint
789 /// is `Allow` by default.
791 /// **Why is this bad?** While such a cast is not bad in itself, the results can
792 /// be surprising when this is not the intended behavior, as demonstrated by the
795 /// **Known problems:** None.
799 /// std::u32::MAX as i32; // will yield a value of `-1`
801 pub CAST_POSSIBLE_WRAP,
803 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
806 declare_clippy_lint! {
807 /// **What it does:** Checks for casts between numerical types that may
808 /// be replaced by safe conversion functions.
810 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
811 /// conversions, including silently lossy conversions. Conversion functions such
812 /// as `i32::from` will only perform lossless conversions. Using the conversion
813 /// functions prevents conversions from turning into silent lossy conversions if
814 /// the types of the input expressions ever change, and make it easier for
815 /// people reading the code to know that the conversion is lossless.
817 /// **Known problems:** None.
821 /// fn as_u64(x: u8) -> u64 {
826 /// Using `::from` would look like this:
829 /// fn as_u64(x: u8) -> u64 {
835 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
838 declare_clippy_lint! {
839 /// **What it does:** Checks for casts to the same type.
841 /// **Why is this bad?** It's just unnecessary.
843 /// **Known problems:** None.
847 /// let _ = 2i32 as i32;
849 pub UNNECESSARY_CAST,
851 "cast to the same type, e.g., `x as i32` where `x: i32`"
854 declare_clippy_lint! {
855 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
856 /// more-strictly-aligned pointer
858 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
861 /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
862 /// on the resulting pointer is fine.
866 /// let _ = (&1u8 as *const u8) as *const u16;
867 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
869 pub CAST_PTR_ALIGNMENT,
871 "cast from a pointer to a more-strictly-aligned pointer"
874 declare_clippy_lint! {
875 /// **What it does:** Checks for casts of function pointers to something other than usize
877 /// **Why is this bad?**
878 /// Casting a function pointer to anything other than usize/isize is not portable across
879 /// architectures, because you end up losing bits if the target type is too small or end up with a
880 /// bunch of extra bits that waste space and add more instructions to the final binary than
881 /// strictly necessary for the problem
883 /// Casting to isize also doesn't make sense since there are no signed addresses.
889 /// fn fun() -> i32 { 1 }
890 /// let a = fun as i64;
893 /// fn fun2() -> i32 { 1 }
894 /// let a = fun2 as usize;
896 pub FN_TO_NUMERIC_CAST,
898 "casting a function pointer to a numeric type other than usize"
901 declare_clippy_lint! {
902 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
905 /// **Why is this bad?**
906 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
907 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
908 /// a comment) to perform the truncation.
914 /// fn fn1() -> i16 {
917 /// let _ = fn1 as i32;
919 /// // Better: Cast to usize first, then comment with the reason for the truncation
920 /// fn fn2() -> i16 {
923 /// let fn_ptr = fn2 as usize;
924 /// let fn_ptr_truncated = fn_ptr as i32;
926 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
928 "casting a function pointer to a numeric type not wide enough to store the address"
931 /// Returns the size in bits of an integral type.
932 /// Will return 0 if the type is not an int or uint variant
933 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
935 ty::Int(i) => match i {
936 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
943 ty::Uint(i) => match i {
944 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
955 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
957 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
962 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to_f64: bool) {
963 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
964 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
965 let arch_dependent_str = "on targets with 64-bit wide pointers ";
966 let from_nbits_str = if arch_dependent {
968 } else if is_isize_or_usize(cast_from) {
969 "32 or 64".to_owned()
971 int_ty_to_nbits(cast_from, cx.tcx).to_string()
978 "casting `{0}` to `{1}` causes a loss of precision {2}(`{0}` is {3} bits wide, \
979 but `{1}`'s mantissa is only {4} bits wide)",
981 if cast_to_f64 { "f64" } else { "f32" },
982 if arch_dependent { arch_dependent_str } else { "" },
989 fn should_strip_parens(op: &Expr<'_>, snip: &str) -> bool {
990 if let ExprKind::Binary(_, _, _) = op.kind {
991 if snip.starts_with('(') && snip.ends_with(')') {
998 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
999 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
1000 if in_constant(cx, expr.hir_id) {
1003 // The suggestion is to use a function call, so if the original expression
1004 // has parens on the outside, they are no longer needed.
1005 let mut applicability = Applicability::MachineApplicable;
1006 let opt = snippet_opt(cx, op.span);
1007 let sugg = if let Some(ref snip) = opt {
1008 if should_strip_parens(op, snip) {
1009 &snip[1..snip.len() - 1]
1014 applicability = Applicability::HasPlaceholders;
1023 "casting `{}` to `{}` may become silently lossy if you later change the type",
1027 format!("{}::from({})", cast_to, sugg),
1038 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1039 if !cast_from.is_signed() || cast_to.is_signed() {
1043 // don't lint for positive constants
1044 let const_val = constant(cx, &cx.tables, op);
1046 if let Some((const_val, _)) = const_val;
1047 if let Constant::Int(n) = const_val;
1048 if let ty::Int(ity) = cast_from.kind;
1049 if sext(cx.tcx, n, ity) >= 0;
1055 // don't lint for the result of methods that always return non-negative values
1056 if let ExprKind::MethodCall(ref path, _, _) = op.kind {
1057 let mut method_name = path.ident.name.as_str();
1058 let whitelisted_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
1061 if method_name == "unwrap";
1062 if let Some(arglist) = method_chain_args(op, &["unwrap"]);
1063 if let ExprKind::MethodCall(ref inner_path, _, _) = &arglist[0][0].kind;
1065 method_name = inner_path.ident.name.as_str();
1069 if whitelisted_methods.iter().any(|&name| method_name == name) {
1079 "casting `{}` to `{}` may lose the sign of the value",
1085 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1086 let arch_64_suffix = " on targets with 64-bit wide pointers";
1087 let arch_32_suffix = " on targets with 32-bit wide pointers";
1088 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1089 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1090 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1091 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1092 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1093 (true, true) | (false, false) => (
1094 to_nbits < from_nbits,
1096 to_nbits == from_nbits && cast_unsigned_to_signed,
1106 to_nbits <= 32 && cast_unsigned_to_signed,
1112 cast_unsigned_to_signed,
1113 if from_nbits == 64 {
1120 if span_truncation {
1123 CAST_POSSIBLE_TRUNCATION,
1126 "casting `{}` to `{}` may truncate the value{}",
1129 match suffix_truncation {
1130 ArchSuffix::_32 => arch_32_suffix,
1131 ArchSuffix::_64 => arch_64_suffix,
1132 ArchSuffix::None => "",
1143 "casting `{}` to `{}` may wrap around the value{}",
1147 ArchSuffix::_32 => arch_32_suffix,
1148 ArchSuffix::_64 => arch_64_suffix,
1149 ArchSuffix::None => "",
1156 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1157 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1158 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1159 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1160 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1162 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1166 declare_lint_pass!(Casts => [
1167 CAST_PRECISION_LOSS,
1169 CAST_POSSIBLE_TRUNCATION,
1175 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1178 // Check if the given type is either `core::ffi::c_void` or
1179 // one of the platform specific `libc::<platform>::c_void` of libc.
1180 fn is_c_void(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1181 if let ty::Adt(adt, _) = ty.kind {
1182 let names = cx.get_def_path(adt.did);
1184 if names.is_empty() {
1187 if names[0] == sym!(libc) || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
1194 /// Returns the mantissa bits wide of a fp type.
1195 /// Will return 0 if the type is not a fp
1196 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1198 ty::Float(FloatTy::F32) => 23,
1199 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1204 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
1205 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
1206 if expr.span.from_expansion() {
1209 if let ExprKind::Cast(ref ex, _) = expr.kind {
1210 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1211 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1212 if let ExprKind::Lit(ref lit) = ex.kind {
1214 if let LitKind::Int(n, _) = lit.node;
1215 if let Some(src) = snippet_opt(cx, lit.span);
1216 if cast_to.is_floating_point();
1217 if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node);
1218 let from_nbits = 128 - n.leading_zeros();
1219 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1220 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits && num_lit.is_decimal();
1226 &format!("casting integer literal to `{}` is unnecessary", cast_to),
1228 format!("{}_{}", n, cast_to),
1229 Applicability::MachineApplicable,
1235 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
1237 if cast_from.kind == cast_to.kind && !in_external_macro(cx.sess(), expr.span) {
1243 "casting to the same type is unnecessary (`{}` -> `{}`)",
1251 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1252 lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
1255 lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
1260 fn lint_numeric_casts<'tcx>(
1261 cx: &LateContext<'_, 'tcx>,
1263 cast_expr: &Expr<'_>,
1264 cast_from: Ty<'tcx>,
1267 match (cast_from.is_integral(), cast_to.is_integral()) {
1269 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1270 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind {
1275 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1276 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1278 if from_nbits < to_nbits {
1279 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1285 CAST_POSSIBLE_TRUNCATION,
1287 &format!("casting `{}` to `{}` may truncate the value", cast_from, cast_to),
1289 if !cast_to.is_signed() {
1295 "casting `{}` to `{}` may lose the sign of the value",
1302 check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
1303 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1304 check_lossless(cx, expr, cast_expr, cast_from, cast_to);
1307 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.kind, &cast_to.kind) {
1310 CAST_POSSIBLE_TRUNCATION,
1312 "casting `f64` to `f32` may truncate the value",
1315 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.kind, &cast_to.kind) {
1316 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1322 fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
1324 if let ty::RawPtr(from_ptr_ty) = &cast_from.kind;
1325 if let ty::RawPtr(to_ptr_ty) = &cast_to.kind;
1326 if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
1327 if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
1328 if from_layout.align.abi < to_layout.align.abi;
1329 // with c_void, we inherently need to trust the user
1330 if !is_c_void(cx, from_ptr_ty.ty);
1331 // when casting from a ZST, we don't know enough to properly lint
1332 if !from_layout.is_zst();
1339 "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
1342 from_layout.align.abi.bytes(),
1343 to_layout.align.abi.bytes(),
1350 fn lint_fn_to_numeric_cast(
1351 cx: &LateContext<'_, '_>,
1353 cast_expr: &Expr<'_>,
1357 // We only want to check casts to `ty::Uint` or `ty::Int`
1358 match cast_to.kind {
1359 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1362 match cast_from.kind {
1363 ty::FnDef(..) | ty::FnPtr(_) => {
1364 let mut applicability = Applicability::MaybeIncorrect;
1365 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1367 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1368 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1371 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1374 "casting function pointer `{}` to `{}`, which truncates the value",
1375 from_snippet, cast_to
1378 format!("{} as usize", from_snippet),
1381 } else if cast_to.kind != ty::Uint(UintTy::Usize) {
1386 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1388 format!("{} as usize", from_snippet),
1397 declare_clippy_lint! {
1398 /// **What it does:** Checks for types used in structs, parameters and `let`
1399 /// declarations above a certain complexity threshold.
1401 /// **Why is this bad?** Too complex types make the code less readable. Consider
1402 /// using a `type` definition to simplify them.
1404 /// **Known problems:** None.
1408 /// # use std::rc::Rc;
1410 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1413 pub TYPE_COMPLEXITY,
1415 "usage of very complex types that might be better factored into `type` definitions"
1418 pub struct TypeComplexity {
1422 impl TypeComplexity {
1424 pub fn new(threshold: u64) -> Self {
1429 impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
1431 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexity {
1434 cx: &LateContext<'a, 'tcx>,
1436 decl: &'tcx FnDecl<'_>,
1441 self.check_fndecl(cx, decl);
1444 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField<'_>) {
1445 // enum variants are also struct fields now
1446 self.check_type(cx, &field.ty);
1449 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
1451 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1452 // functions, enums, structs, impls and traits are covered
1457 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem<'_>) {
1459 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1460 TraitItemKind::Fn(FnSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1461 // methods with default impl are covered by check_fn
1466 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem<'_>) {
1468 ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
1469 // methods are covered by check_fn
1474 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
1475 if let Some(ref ty) = local.ty {
1476 self.check_type(cx, ty);
1481 impl<'a, 'tcx> TypeComplexity {
1482 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl<'_>) {
1483 for arg in decl.inputs {
1484 self.check_type(cx, arg);
1486 if let FnRetTy::Return(ref ty) = decl.output {
1487 self.check_type(cx, ty);
1491 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty<'_>) {
1492 if ty.span.from_expansion() {
1496 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1497 visitor.visit_ty(ty);
1501 if score > self.threshold {
1506 "very complex type used. Consider factoring parts into `type` definitions",
1512 /// Walks a type and assigns a complexity score to it.
1513 struct TypeComplexityVisitor {
1514 /// total complexity score of the type
1516 /// current nesting level
1520 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1521 type Map = Map<'tcx>;
1523 fn visit_ty(&mut self, ty: &'tcx hir::Ty<'_>) {
1524 let (add_score, sub_nest) = match ty.kind {
1525 // _, &x and *x have only small overhead; don't mess with nesting level
1526 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1528 // the "normal" components of a type: named types, arrays/tuples
1529 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1531 // function types bring a lot of overhead
1532 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1534 TyKind::TraitObject(ref param_bounds, _) => {
1535 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1536 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1537 GenericParamKind::Lifetime { .. } => true,
1541 if has_lifetime_parameters {
1542 // complex trait bounds like A<'a, 'b>
1545 // simple trait bounds like A + B
1552 self.score += add_score;
1553 self.nest += sub_nest;
1555 self.nest -= sub_nest;
1557 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
1558 NestedVisitorMap::None
1562 declare_clippy_lint! {
1563 /// **What it does:** Checks for expressions where a character literal is cast
1564 /// to `u8` and suggests using a byte literal instead.
1566 /// **Why is this bad?** In general, casting values to smaller types is
1567 /// error-prone and should be avoided where possible. In the particular case of
1568 /// converting a character literal to u8, it is easy to avoid by just using a
1569 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1570 /// than `'a' as u8`.
1572 /// **Known problems:** None.
1579 /// A better version, using the byte literal:
1586 "casting a character literal to `u8` truncates"
1589 declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
1591 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1592 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
1594 if !expr.span.from_expansion();
1595 if let ExprKind::Cast(e, _) = &expr.kind;
1596 if let ExprKind::Lit(l) = &e.kind;
1597 if let LitKind::Char(c) = l.node;
1598 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).kind;
1600 let mut applicability = Applicability::MachineApplicable;
1601 let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
1607 "casting a character literal to `u8` truncates",
1609 db.note("`char` is four bytes wide, but `u8` is a single byte");
1614 "use a byte literal instead",
1615 format!("b{}", snippet),
1625 declare_clippy_lint! {
1626 /// **What it does:** Checks for comparisons where one side of the relation is
1627 /// either the minimum or maximum value for its type and warns if it involves a
1628 /// case that is always true or always false. Only integer and boolean types are
1631 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1632 /// that it is possible for `x` to be less than the minimum. Expressions like
1633 /// `max < x` are probably mistakes.
1635 /// **Known problems:** For `usize` the size of the current compile target will
1636 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1637 /// a comparison to detect target pointer width will trigger this lint. One can
1638 /// use `mem::sizeof` and compare its value or conditional compilation
1640 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1645 /// let vec: Vec<isize> = vec![];
1646 /// if vec.len() <= 0 {}
1647 /// if 100 > std::i32::MAX {}
1649 pub ABSURD_EXTREME_COMPARISONS,
1651 "a comparison with a maximum or minimum value that is always true or false"
1654 declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
1661 struct ExtremeExpr<'a> {
1666 enum AbsurdComparisonResult {
1669 InequalityImpossible,
1672 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
1673 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1674 let precast_ty = cx.tables.expr_ty(cast_exp);
1675 let cast_ty = cx.tables.expr_ty(expr);
1677 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1683 fn detect_absurd_comparison<'a, 'tcx>(
1684 cx: &LateContext<'a, 'tcx>,
1686 lhs: &'tcx Expr<'_>,
1687 rhs: &'tcx Expr<'_>,
1688 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1689 use crate::types::AbsurdComparisonResult::{AlwaysFalse, AlwaysTrue, InequalityImpossible};
1690 use crate::types::ExtremeType::{Maximum, Minimum};
1691 use crate::utils::comparisons::{normalize_comparison, Rel};
1693 // absurd comparison only makes sense on primitive types
1694 // primitive types don't implement comparison operators with each other
1695 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1699 // comparisons between fix sized types and target sized types are considered unanalyzable
1700 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1704 let (rel, normalized_lhs, normalized_rhs) = normalize_comparison(op, lhs, rhs)?;
1706 let lx = detect_extreme_expr(cx, normalized_lhs);
1707 let rx = detect_extreme_expr(cx, normalized_rhs);
1712 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1713 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1719 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1720 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1721 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1722 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1726 Rel::Ne | Rel::Eq => return None,
1730 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) -> Option<ExtremeExpr<'tcx>> {
1731 use crate::types::ExtremeType::{Maximum, Minimum};
1733 let ty = cx.tables.expr_ty(expr);
1735 let cv = constant(cx, cx.tables, expr)?.0;
1737 let which = match (&ty.kind, cv) {
1738 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1739 (&ty::Int(ity), Constant::Int(i))
1740 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1745 (&ty::Bool, Constant::Bool(true)) => Maximum,
1746 (&ty::Int(ity), Constant::Int(i))
1747 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1751 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1755 Some(ExtremeExpr { which, expr })
1758 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1759 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
1760 use crate::types::AbsurdComparisonResult::{AlwaysFalse, AlwaysTrue, InequalityImpossible};
1761 use crate::types::ExtremeType::{Maximum, Minimum};
1763 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
1764 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1765 if !expr.span.from_expansion() {
1766 let msg = "this comparison involving the minimum or maximum element for this \
1767 type contains a case that is always true or always false";
1769 let conclusion = match result {
1770 AlwaysFalse => "this comparison is always false".to_owned(),
1771 AlwaysTrue => "this comparison is always true".to_owned(),
1772 InequalityImpossible => format!(
1773 "the case where the two sides are not equal never occurs, consider using `{} == {}` \
1775 snippet(cx, lhs.span, "lhs"),
1776 snippet(cx, rhs.span, "rhs")
1781 "because `{}` is the {} value for this type, {}",
1782 snippet(cx, culprit.expr.span, "x"),
1783 match culprit.which {
1784 Minimum => "minimum",
1785 Maximum => "maximum",
1790 span_lint_and_help(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1797 declare_clippy_lint! {
1798 /// **What it does:** Checks for comparisons where the relation is always either
1799 /// true or false, but where one side has been upcast so that the comparison is
1800 /// necessary. Only integer types are checked.
1802 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1803 /// will mistakenly imply that it is possible for `x` to be outside the range of
1806 /// **Known problems:**
1807 /// https://github.com/rust-lang/rust-clippy/issues/886
1812 /// (x as u32) > 300;
1814 pub INVALID_UPCAST_COMPARISONS,
1816 "a comparison involving an upcast which is always true or false"
1819 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
1821 #[derive(Copy, Clone, Debug, Eq)]
1828 #[allow(clippy::cast_sign_loss)]
1830 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1833 } else if u > (i128::max_value() as u128) {
1841 impl PartialEq for FullInt {
1843 fn eq(&self, other: &Self) -> bool {
1844 self.partial_cmp(other).expect("`partial_cmp` only returns `Some(_)`") == Ordering::Equal
1848 impl PartialOrd for FullInt {
1850 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1851 Some(match (self, other) {
1852 (&Self::S(s), &Self::S(o)) => s.cmp(&o),
1853 (&Self::U(s), &Self::U(o)) => s.cmp(&o),
1854 (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
1855 (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
1859 impl Ord for FullInt {
1861 fn cmp(&self, other: &Self) -> Ordering {
1862 self.partial_cmp(other)
1863 .expect("`partial_cmp` for FullInt can never return `None`")
1867 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr<'_>) -> Option<(FullInt, FullInt)> {
1868 use std::{i128, i16, i32, i64, i8, isize, u128, u16, u32, u64, u8, usize};
1870 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1871 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1872 let cast_ty = cx.tables.expr_ty(expr);
1873 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1874 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1877 match pre_cast_ty.kind {
1878 ty::Int(int_ty) => Some(match int_ty {
1880 FullInt::S(i128::from(i8::min_value())),
1881 FullInt::S(i128::from(i8::max_value())),
1884 FullInt::S(i128::from(i16::min_value())),
1885 FullInt::S(i128::from(i16::max_value())),
1888 FullInt::S(i128::from(i32::min_value())),
1889 FullInt::S(i128::from(i32::max_value())),
1892 FullInt::S(i128::from(i64::min_value())),
1893 FullInt::S(i128::from(i64::max_value())),
1895 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1897 FullInt::S(isize::min_value() as i128),
1898 FullInt::S(isize::max_value() as i128),
1901 ty::Uint(uint_ty) => Some(match uint_ty {
1903 FullInt::U(u128::from(u8::min_value())),
1904 FullInt::U(u128::from(u8::max_value())),
1907 FullInt::U(u128::from(u16::min_value())),
1908 FullInt::U(u128::from(u16::max_value())),
1911 FullInt::U(u128::from(u32::min_value())),
1912 FullInt::U(u128::from(u32::max_value())),
1915 FullInt::U(u128::from(u64::min_value())),
1916 FullInt::U(u128::from(u64::max_value())),
1918 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1920 FullInt::U(usize::min_value() as u128),
1921 FullInt::U(usize::max_value() as u128),
1931 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) -> Option<FullInt> {
1932 let val = constant(cx, cx.tables, expr)?.0;
1933 if let Constant::Int(const_int) = val {
1934 match cx.tables.expr_ty(expr).kind {
1935 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1936 ty::Uint(_) => Some(FullInt::U(const_int)),
1944 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr<'_>, always: bool) {
1945 if let ExprKind::Cast(ref cast_val, _) = expr.kind {
1948 INVALID_UPCAST_COMPARISONS,
1951 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1952 snippet(cx, cast_val.span, "the expression"),
1953 if always { "true" } else { "false" },
1959 fn upcast_comparison_bounds_err<'a, 'tcx>(
1960 cx: &LateContext<'a, 'tcx>,
1962 rel: comparisons::Rel,
1963 lhs_bounds: Option<(FullInt, FullInt)>,
1964 lhs: &'tcx Expr<'_>,
1965 rhs: &'tcx Expr<'_>,
1968 use crate::utils::comparisons::Rel;
1970 if let Some((lb, ub)) = lhs_bounds {
1971 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1972 if rel == Rel::Eq || rel == Rel::Ne {
1973 if norm_rhs_val < lb || norm_rhs_val > ub {
1974 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1976 } else if match rel {
1991 Rel::Eq | Rel::Ne => unreachable!(),
1993 err_upcast_comparison(cx, span, lhs, true)
1994 } else if match rel {
2009 Rel::Eq | Rel::Ne => unreachable!(),
2011 err_upcast_comparison(cx, span, lhs, false)
2017 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
2018 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
2019 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
2020 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
2021 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
2027 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
2028 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
2030 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
2031 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
2036 declare_clippy_lint! {
2037 /// **What it does:** Checks for public `impl` or `fn` missing generalization
2038 /// over different hashers and implicitly defaulting to the default hashing
2039 /// algorithm (`SipHash`).
2041 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
2044 /// **Known problems:** Suggestions for replacing constructors can contain
2045 /// false-positives. Also applying suggestions can require modification of other
2046 /// pieces of code, possibly including external crates.
2050 /// # use std::collections::HashMap;
2051 /// # use std::hash::{Hash, BuildHasher};
2052 /// # trait Serialize {};
2053 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
2055 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
2057 /// could be rewritten as
2059 /// # use std::collections::HashMap;
2060 /// # use std::hash::{Hash, BuildHasher};
2061 /// # trait Serialize {};
2062 /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
2064 /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
2066 pub IMPLICIT_HASHER,
2068 "missing generalization over different hashers"
2071 declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
2073 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
2074 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
2075 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
2076 use rustc_span::BytePos;
2078 fn suggestion<'a, 'tcx>(
2079 cx: &LateContext<'a, 'tcx>,
2080 db: &mut DiagnosticBuilder<'_>,
2081 generics_span: Span,
2082 generics_suggestion_span: Span,
2083 target: &ImplicitHasherType<'_>,
2084 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2086 let generics_snip = snippet(cx, generics_span, "");
2088 let generics_snip = if generics_snip.is_empty() {
2091 &generics_snip[1..generics_snip.len() - 1]
2096 "consider adding a type parameter".to_string(),
2099 generics_suggestion_span,
2101 "<{}{}S: ::std::hash::BuildHasher{}>",
2103 if generics_snip.is_empty() { "" } else { ", " },
2104 if vis.suggestions.is_empty() {
2107 // request users to add `Default` bound so that generic constructors can be used
2114 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2119 if !vis.suggestions.is_empty() {
2120 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2124 if !cx.access_levels.is_exported(item.hir_id) {
2135 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2138 for target in &vis.found {
2139 if differing_macro_contexts(item.span, target.span()) {
2143 let generics_suggestion_span = generics.span.substitute_dummy({
2144 let pos = snippet_opt(cx, item.span.until(target.span()))
2145 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2146 if let Some(pos) = pos {
2147 Span::new(pos, pos, item.span.data().ctxt)
2153 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2154 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2155 ctr_vis.visit_impl_item(item);
2163 "impl for `{}` should be generalized over different hashers",
2167 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2172 ItemKind::Fn(ref sig, ref generics, body_id) => {
2173 let body = cx.tcx.hir().body(body_id);
2175 for ty in sig.decl.inputs {
2176 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2179 for target in &vis.found {
2180 if in_external_macro(cx.sess(), generics.span) {
2183 let generics_suggestion_span = generics.span.substitute_dummy({
2184 let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
2186 let i = snip.find("fn")?;
2187 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2189 .expect("failed to create span for type parameters");
2190 Span::new(pos, pos, item.span.data().ctxt)
2193 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2194 ctr_vis.visit_body(body);
2201 "parameter of type `{}` should be generalized over different hashers",
2205 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2216 enum ImplicitHasherType<'tcx> {
2217 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2218 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2221 impl<'tcx> ImplicitHasherType<'tcx> {
2222 /// Checks that `ty` is a target type without a `BuildHasher`.
2223 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty<'_>) -> Option<Self> {
2224 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.kind {
2225 let params: Vec<_> = path
2233 .filter_map(|arg| match arg {
2234 GenericArg::Type(ty) => Some(ty),
2238 let params_len = params.len();
2240 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2242 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2243 Some(ImplicitHasherType::HashMap(
2246 snippet(cx, params[0].span, "K"),
2247 snippet(cx, params[1].span, "V"),
2249 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2250 Some(ImplicitHasherType::HashSet(
2253 snippet(cx, params[0].span, "T"),
2263 fn type_name(&self) -> &'static str {
2265 ImplicitHasherType::HashMap(..) => "HashMap",
2266 ImplicitHasherType::HashSet(..) => "HashSet",
2270 fn type_arguments(&self) -> String {
2272 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2273 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2277 fn ty(&self) -> Ty<'tcx> {
2279 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2283 fn span(&self) -> Span {
2285 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2290 struct ImplicitHasherTypeVisitor<'a, 'tcx> {
2291 cx: &'a LateContext<'a, 'tcx>,
2292 found: Vec<ImplicitHasherType<'tcx>>,
2295 impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
2296 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2297 Self { cx, found: vec![] }
2301 impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2302 type Map = Map<'tcx>;
2304 fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
2305 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2306 self.found.push(target);
2312 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
2313 NestedVisitorMap::None
2317 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2318 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2319 cx: &'a LateContext<'a, 'tcx>,
2320 body: &'a TypeckTables<'tcx>,
2321 target: &'b ImplicitHasherType<'tcx>,
2322 suggestions: BTreeMap<Span, String>,
2325 impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2326 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2331 suggestions: BTreeMap::new(),
2336 impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2337 type Map = Map<'tcx>;
2339 fn visit_body(&mut self, body: &'tcx Body<'_>) {
2340 let prev_body = self.body;
2341 self.body = self.cx.tcx.body_tables(body.id());
2342 walk_body(self, body);
2343 self.body = prev_body;
2346 fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
2348 if let ExprKind::Call(ref fun, ref args) = e.kind;
2349 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.kind;
2350 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.kind;
2352 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2356 if match_path(ty_path, &paths::HASHMAP) {
2357 if method.ident.name == sym!(new) {
2359 .insert(e.span, "HashMap::default()".to_string());
2360 } else if method.ident.name == sym!(with_capacity) {
2361 self.suggestions.insert(
2364 "HashMap::with_capacity_and_hasher({}, Default::default())",
2365 snippet(self.cx, args[0].span, "capacity"),
2369 } else if match_path(ty_path, &paths::HASHSET) {
2370 if method.ident.name == sym!(new) {
2372 .insert(e.span, "HashSet::default()".to_string());
2373 } else if method.ident.name == sym!(with_capacity) {
2374 self.suggestions.insert(
2377 "HashSet::with_capacity_and_hasher({}, Default::default())",
2378 snippet(self.cx, args[0].span, "capacity"),
2389 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
2390 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2394 declare_clippy_lint! {
2395 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2397 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2398 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2401 /// **Known problems:** None.
2407 /// *(r as *const _ as *mut _) += 1;
2412 /// Instead consider using interior mutability types.
2415 /// use std::cell::UnsafeCell;
2417 /// fn x(r: &UnsafeCell<i32>) {
2423 pub CAST_REF_TO_MUT,
2425 "a cast of reference to a mutable pointer"
2428 declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
2430 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2431 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
2433 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.kind;
2434 if let ExprKind::Cast(e, t) = &e.kind;
2435 if let TyKind::Ptr(MutTy { mutbl: Mutability::Mut, .. }) = t.kind;
2436 if let ExprKind::Cast(e, t) = &e.kind;
2437 if let TyKind::Ptr(MutTy { mutbl: Mutability::Not, .. }) = t.kind;
2438 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).kind;
2444 "casting `&T` to `&mut T` may cause undefined behavior, consider instead using an `UnsafeCell`",