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_errors::{Applicability, DiagnosticBuilder};
14 use rustc_hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
16 use rustc_lint::{LateContext, LateLintPass, LintContext};
17 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
18 use rustc_span::hygiene::{ExpnKind, MacroKind};
19 use rustc_span::source_map::Span;
20 use rustc_span::symbol::{sym, Symbol};
21 use rustc_target::spec::abi::Abi;
22 use rustc_typeck::hir_ty_to_ty;
23 use syntax::ast::{FloatTy, IntTy, LitFloatType, LitIntType, LitKind, UintTy};
25 use crate::consts::{constant, Constant};
26 use crate::utils::paths;
28 clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
29 match_path, method_chain_args, multispan_sugg, qpath_res, same_tys, sext, snippet, snippet_opt,
30 snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg,
31 span_lint_and_then, unsext,
34 declare_clippy_lint! {
35 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
37 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
38 /// the heap. So if you `Box` it, you just add another level of indirection
39 /// without any benefit whatsoever.
41 /// **Known problems:** None.
46 /// values: Box<Vec<Foo>>,
59 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
62 declare_clippy_lint! {
63 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
65 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
66 /// the heap. So if you `Box` its contents, you just add another level of indirection.
68 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
74 /// values: Vec<Box<i32>>,
87 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
90 declare_clippy_lint! {
91 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
94 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
95 /// represents an optional optional value which is logically the same thing as an optional
96 /// value but has an unneeded extra level of wrapping.
98 /// **Known problems:** None.
102 /// fn x() -> Option<Option<u32>> {
108 "usage of `Option<Option<T>>`"
111 declare_clippy_lint! {
112 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
113 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
115 /// **Why is this bad?** Gankro says:
117 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
118 /// pointers and indirection.
119 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
121 /// > "only" amortized for push/pop, should be faster in the general case for
122 /// almost every possible
123 /// > workload, and isn't even amortized at all if you can predict the capacity
126 /// > `LinkedList`s are only really good if you're doing a lot of merging or
127 /// splitting of lists.
128 /// > This is because they can just mangle some pointers instead of actually
129 /// copying the data. Even
130 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
131 /// can still be better
132 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
134 /// **Known problems:** False positives – the instances where using a
135 /// `LinkedList` makes sense are few and far between, but they can still happen.
139 /// # use std::collections::LinkedList;
140 /// let x: LinkedList<usize> = LinkedList::new();
144 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a `VecDeque`"
147 declare_clippy_lint! {
148 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
150 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
153 /// **Known problems:** None.
157 /// fn foo(bar: &Box<T>) { ... }
163 /// fn foo(bar: &T) { ... }
167 "a borrow of a boxed type"
171 vec_box_size_threshold: u64,
174 impl_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX]);
176 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Types {
179 cx: &LateContext<'_, '_>,
186 // Skip trait implementations; see issue #605.
187 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
188 if let ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
193 self.check_fn_decl(cx, decl);
196 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField<'_>) {
197 self.check_ty(cx, &field.ty, false);
200 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem<'_>) {
202 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_ty(cx, ty, false),
203 TraitItemKind::Method(ref sig, _) => self.check_fn_decl(cx, &sig.decl),
208 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local<'_>) {
209 if let Some(ref ty) = local.ty {
210 self.check_ty(cx, ty, true);
215 /// Checks if `qpath` has last segment with type parameter matching `path`
216 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath<'_>, path: &[&str]) -> bool {
217 let last = last_path_segment(qpath);
219 if let Some(ref params) = last.args;
220 if !params.parenthesized;
221 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
222 GenericArg::Type(ty) => Some(ty),
225 if let TyKind::Path(ref qpath) = ty.kind;
226 if let Some(did) = qpath_res(cx, qpath, ty.hir_id).opt_def_id();
227 if match_def_path(cx, did, path);
236 pub fn new(vec_box_size_threshold: u64) -> Self {
237 Self { vec_box_size_threshold }
240 fn check_fn_decl(&mut self, cx: &LateContext<'_, '_>, decl: &FnDecl<'_>) {
241 for input in decl.inputs {
242 self.check_ty(cx, input, false);
245 if let FunctionRetTy::Return(ref ty) = decl.output {
246 self.check_ty(cx, ty, false);
250 /// Recursively check for `TypePass` lints in the given type. Stop at the first
253 /// The parameter `is_local` distinguishes the context of the type; types from
254 /// local bindings should only be checked for the `BORROWED_BOX` lint.
255 #[allow(clippy::too_many_lines)]
256 fn check_ty(&mut self, cx: &LateContext<'_, '_>, hir_ty: &hir::Ty<'_>, is_local: bool) {
257 if hir_ty.span.from_expansion() {
261 TyKind::Path(ref qpath) if !is_local => {
262 let hir_id = hir_ty.hir_id;
263 let res = qpath_res(cx, qpath, hir_id);
264 if let Some(def_id) = res.opt_def_id() {
265 if Some(def_id) == cx.tcx.lang_items().owned_box() {
266 if match_type_parameter(cx, qpath, &paths::VEC) {
271 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
272 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
274 return; // don't recurse into the type
276 } else if cx.tcx.is_diagnostic_item(Symbol::intern("vec_type"), def_id) {
278 // Get the _ part of Vec<_>
279 if let Some(ref last) = last_path_segment(qpath).args;
280 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
281 GenericArg::Type(ty) => Some(ty),
284 // ty is now _ at this point
285 if let TyKind::Path(ref ty_qpath) = ty.kind;
286 let res = qpath_res(cx, ty_qpath, ty.hir_id);
287 if let Some(def_id) = res.opt_def_id();
288 if Some(def_id) == cx.tcx.lang_items().owned_box();
289 // At this point, we know ty is Box<T>, now get T
290 if let Some(ref last) = last_path_segment(ty_qpath).args;
291 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
292 GenericArg::Type(ty) => Some(ty),
295 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
296 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env);
297 if let Ok(ty_ty_size) = cx.layout_of(ty_ty).map(|l| l.size.bytes());
298 if ty_ty_size <= self.vec_box_size_threshold;
304 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
306 format!("Vec<{}>", ty_ty),
307 Applicability::MachineApplicable,
309 return; // don't recurse into the type
312 } else if match_def_path(cx, def_id, &paths::OPTION) {
313 if match_type_parameter(cx, qpath, &paths::OPTION) {
318 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
319 enum if you need to distinguish all 3 cases",
321 return; // don't recurse into the type
323 } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
328 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
329 "a `VecDeque` might work",
331 return; // don't recurse into the type
335 QPath::Resolved(Some(ref ty), ref p) => {
336 self.check_ty(cx, ty, is_local);
337 for ty in p.segments.iter().flat_map(|seg| {
340 .map_or_else(|| [].iter(), |params| params.args.iter())
341 .filter_map(|arg| match arg {
342 GenericArg::Type(ty) => Some(ty),
346 self.check_ty(cx, ty, is_local);
349 QPath::Resolved(None, ref p) => {
350 for ty in p.segments.iter().flat_map(|seg| {
353 .map_or_else(|| [].iter(), |params| params.args.iter())
354 .filter_map(|arg| match arg {
355 GenericArg::Type(ty) => Some(ty),
359 self.check_ty(cx, ty, is_local);
362 QPath::TypeRelative(ref ty, ref seg) => {
363 self.check_ty(cx, ty, is_local);
364 if let Some(ref params) = seg.args {
365 for ty in params.args.iter().filter_map(|arg| match arg {
366 GenericArg::Type(ty) => Some(ty),
369 self.check_ty(cx, ty, is_local);
375 TyKind::Rptr(ref lt, ref mut_ty) => self.check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
377 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
378 self.check_ty(cx, ty, is_local)
380 TyKind::Tup(tys) => {
382 self.check_ty(cx, ty, is_local);
391 cx: &LateContext<'_, '_>,
392 hir_ty: &hir::Ty<'_>,
397 match mut_ty.ty.kind {
398 TyKind::Path(ref qpath) => {
399 let hir_id = mut_ty.ty.hir_id;
400 let def = qpath_res(cx, qpath, hir_id);
402 if let Some(def_id) = def.opt_def_id();
403 if Some(def_id) == cx.tcx.lang_items().owned_box();
404 if let QPath::Resolved(None, ref path) = *qpath;
405 if let [ref bx] = *path.segments;
406 if let Some(ref params) = bx.args;
407 if !params.parenthesized;
408 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
409 GenericArg::Type(ty) => Some(ty),
413 if is_any_trait(inner) {
414 // Ignore `Box<Any>` types; see issue #1884 for details.
418 let ltopt = if lt.is_elided() {
421 format!("{} ", lt.name.ident().as_str())
423 let mutopt = if mut_ty.mutbl == Mutability::Mut {
428 let mut applicability = Applicability::MachineApplicable;
433 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
439 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
441 Applicability::Unspecified,
443 return; // don't recurse into the type
446 self.check_ty(cx, &mut_ty.ty, is_local);
448 _ => self.check_ty(cx, &mut_ty.ty, is_local),
453 // Returns true if given type is `Any` trait.
454 fn is_any_trait(t: &hir::Ty<'_>) -> bool {
456 if let TyKind::TraitObject(ref traits, _) = t.kind;
457 if !traits.is_empty();
458 // Only Send/Sync can be used as additional traits, so it is enough to
459 // check only the first trait.
460 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
469 declare_clippy_lint! {
470 /// **What it does:** Checks for binding a unit value.
472 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
473 /// binding one is kind of pointless.
475 /// **Known problems:** None.
485 "creating a `let` binding to a value of unit type, which usually can't be used afterwards"
488 declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
490 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnitValue {
491 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt<'_>) {
492 if let StmtKind::Local(ref local) = stmt.kind {
493 if is_unit(cx.tables.pat_ty(&local.pat)) {
494 if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
497 if higher::is_from_for_desugar(local) {
500 span_lint_and_then(cx, LET_UNIT_VALUE, stmt.span, "this let-binding has unit value", |db| {
501 if let Some(expr) = &local.init {
502 let snip = snippet_with_macro_callsite(cx, expr.span, "()");
505 "omit the `let` binding",
506 format!("{};", snip),
507 Applicability::MachineApplicable, // snippet
516 declare_clippy_lint! {
517 /// **What it does:** Checks for comparisons to unit. This includes all binary
518 /// comparisons (like `==` and `<`) and asserts.
520 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
521 /// clumsily written constant. Mostly this happens when someone accidentally
522 /// adds semicolons at the end of the operands.
524 /// **Known problems:** None.
555 /// assert_eq!({ foo(); }, { bar(); });
557 /// will always succeed
560 "comparing unit values"
563 declare_lint_pass!(UnitCmp => [UNIT_CMP]);
565 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
566 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) {
567 if expr.span.from_expansion() {
568 if let Some(callee) = expr.span.source_callee() {
569 if let ExpnKind::Macro(MacroKind::Bang, symbol) = callee.kind {
570 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
572 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
573 let result = match &*symbol.as_str() {
574 "assert_eq" | "debug_assert_eq" => "succeed",
575 "assert_ne" | "debug_assert_ne" => "fail",
583 "`{}` of unit values detected. This will always {}",
594 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
596 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
597 let result = match op {
598 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
606 "{}-comparison of unit values detected. This will always be {}",
616 declare_clippy_lint! {
617 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
618 /// unit literal (`()`).
620 /// **Why is this bad?** This is likely the result of an accidental semicolon.
622 /// **Known problems:** None.
633 "passing unit to a function"
636 declare_lint_pass!(UnitArg => [UNIT_ARG]);
638 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
639 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
640 if expr.span.from_expansion() {
644 // apparently stuff in the desugaring of `?` can trigger this
645 // so check for that here
646 // only the calls to `Try::from_error` is marked as desugared,
647 // so we need to check both the current Expr and its parent.
648 if is_questionmark_desugar_marked_call(expr) {
652 let map = &cx.tcx.hir();
653 let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
654 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
655 if is_questionmark_desugar_marked_call(parent_expr);
662 ExprKind::Call(_, args) | ExprKind::MethodCall(_, _, args) => {
664 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
665 if let ExprKind::Match(.., match_source) = &arg.kind {
666 if *match_source == MatchSource::TryDesugar {
675 "passing a unit value to a function",
676 "if you intended to pass a unit value, use a unit literal instead",
678 Applicability::MachineApplicable,
688 fn is_questionmark_desugar_marked_call(expr: &Expr<'_>) -> bool {
689 use rustc_span::hygiene::DesugaringKind;
690 if let ExprKind::Call(ref callee, _) = expr.kind {
691 callee.span.is_desugaring(DesugaringKind::QuestionMark)
697 fn is_unit(ty: Ty<'_>) -> bool {
699 ty::Tuple(slice) if slice.is_empty() => true,
704 fn is_unit_literal(expr: &Expr<'_>) -> bool {
706 ExprKind::Tup(ref slice) if slice.is_empty() => true,
711 declare_clippy_lint! {
712 /// **What it does:** Checks for casts from any numerical to a float type where
713 /// the receiving type cannot store all values from the original type without
714 /// rounding errors. This possible rounding is to be expected, so this lint is
715 /// `Allow` by default.
717 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
718 /// or any 64-bit integer to `f64`.
720 /// **Why is this bad?** It's not bad at all. But in some applications it can be
721 /// helpful to know where precision loss can take place. This lint can help find
722 /// those places in the code.
724 /// **Known problems:** None.
728 /// let x = std::u64::MAX;
731 pub CAST_PRECISION_LOSS,
733 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
736 declare_clippy_lint! {
737 /// **What it does:** Checks for casts from a signed to an unsigned numerical
738 /// type. In this case, negative values wrap around to large positive values,
739 /// which can be quite surprising in practice. However, as the cast works as
740 /// defined, this lint is `Allow` by default.
742 /// **Why is this bad?** Possibly surprising results. You can activate this lint
743 /// as a one-time check to see where numerical wrapping can arise.
745 /// **Known problems:** None.
750 /// y as u128; // will return 18446744073709551615
754 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
757 declare_clippy_lint! {
758 /// **What it does:** Checks for casts between numerical types that may
759 /// truncate large values. This is expected behavior, so the cast is `Allow` by
762 /// **Why is this bad?** In some problem domains, it is good practice to avoid
763 /// truncation. This lint can be activated to help assess where additional
764 /// checks could be beneficial.
766 /// **Known problems:** None.
770 /// fn as_u8(x: u64) -> u8 {
774 pub CAST_POSSIBLE_TRUNCATION,
776 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
779 declare_clippy_lint! {
780 /// **What it does:** Checks for casts from an unsigned type to a signed type of
781 /// the same size. Performing such a cast is a 'no-op' for the compiler,
782 /// i.e., nothing is changed at the bit level, and the binary representation of
783 /// the value is reinterpreted. This can cause wrapping if the value is too big
784 /// for the target signed type. However, the cast works as defined, so this lint
785 /// is `Allow` by default.
787 /// **Why is this bad?** While such a cast is not bad in itself, the results can
788 /// be surprising when this is not the intended behavior, as demonstrated by the
791 /// **Known problems:** None.
795 /// std::u32::MAX as i32; // will yield a value of `-1`
797 pub CAST_POSSIBLE_WRAP,
799 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
802 declare_clippy_lint! {
803 /// **What it does:** Checks for casts between numerical types that may
804 /// be replaced by safe conversion functions.
806 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
807 /// conversions, including silently lossy conversions. Conversion functions such
808 /// as `i32::from` will only perform lossless conversions. Using the conversion
809 /// functions prevents conversions from turning into silent lossy conversions if
810 /// the types of the input expressions ever change, and make it easier for
811 /// people reading the code to know that the conversion is lossless.
813 /// **Known problems:** None.
817 /// fn as_u64(x: u8) -> u64 {
822 /// Using `::from` would look like this:
825 /// fn as_u64(x: u8) -> u64 {
831 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
834 declare_clippy_lint! {
835 /// **What it does:** Checks for casts to the same type.
837 /// **Why is this bad?** It's just unnecessary.
839 /// **Known problems:** None.
843 /// let _ = 2i32 as i32;
845 pub UNNECESSARY_CAST,
847 "cast to the same type, e.g., `x as i32` where `x: i32`"
850 declare_clippy_lint! {
851 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
852 /// more-strictly-aligned pointer
854 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
857 /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
858 /// on the resulting pointer is fine.
862 /// let _ = (&1u8 as *const u8) as *const u16;
863 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
865 pub CAST_PTR_ALIGNMENT,
867 "cast from a pointer to a more-strictly-aligned pointer"
870 declare_clippy_lint! {
871 /// **What it does:** Checks for casts of function pointers to something other than usize
873 /// **Why is this bad?**
874 /// Casting a function pointer to anything other than usize/isize is not portable across
875 /// architectures, because you end up losing bits if the target type is too small or end up with a
876 /// bunch of extra bits that waste space and add more instructions to the final binary than
877 /// strictly necessary for the problem
879 /// Casting to isize also doesn't make sense since there are no signed addresses.
885 /// fn fun() -> i32 { 1 }
886 /// let a = fun as i64;
889 /// fn fun2() -> i32 { 1 }
890 /// let a = fun2 as usize;
892 pub FN_TO_NUMERIC_CAST,
894 "casting a function pointer to a numeric type other than usize"
897 declare_clippy_lint! {
898 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
901 /// **Why is this bad?**
902 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
903 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
904 /// a comment) to perform the truncation.
910 /// fn fn1() -> i16 {
913 /// let _ = fn1 as i32;
915 /// // Better: Cast to usize first, then comment with the reason for the truncation
916 /// fn fn2() -> i16 {
919 /// let fn_ptr = fn2 as usize;
920 /// let fn_ptr_truncated = fn_ptr as i32;
922 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
924 "casting a function pointer to a numeric type not wide enough to store the address"
927 /// Returns the size in bits of an integral type.
928 /// Will return 0 if the type is not an int or uint variant
929 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
931 ty::Int(i) => match i {
932 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
939 ty::Uint(i) => match i {
940 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
951 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
953 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
958 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to_f64: bool) {
959 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
960 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
961 let arch_dependent_str = "on targets with 64-bit wide pointers ";
962 let from_nbits_str = if arch_dependent {
964 } else if is_isize_or_usize(cast_from) {
965 "32 or 64".to_owned()
967 int_ty_to_nbits(cast_from, cx.tcx).to_string()
974 "casting `{0}` to `{1}` causes a loss of precision {2}(`{0}` is {3} bits wide, \
975 but `{1}`'s mantissa is only {4} bits wide)",
977 if cast_to_f64 { "f64" } else { "f32" },
978 if arch_dependent { arch_dependent_str } else { "" },
985 fn should_strip_parens(op: &Expr<'_>, snip: &str) -> bool {
986 if let ExprKind::Binary(_, _, _) = op.kind {
987 if snip.starts_with('(') && snip.ends_with(')') {
994 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
995 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
996 if in_constant(cx, expr.hir_id) {
999 // The suggestion is to use a function call, so if the original expression
1000 // has parens on the outside, they are no longer needed.
1001 let mut applicability = Applicability::MachineApplicable;
1002 let opt = snippet_opt(cx, op.span);
1003 let sugg = if let Some(ref snip) = opt {
1004 if should_strip_parens(op, snip) {
1005 &snip[1..snip.len() - 1]
1010 applicability = Applicability::HasPlaceholders;
1019 "casting `{}` to `{}` may become silently lossy if you later change the type",
1023 format!("{}::from({})", cast_to, sugg),
1034 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1035 if !cast_from.is_signed() || cast_to.is_signed() {
1039 // don't lint for positive constants
1040 let const_val = constant(cx, &cx.tables, op);
1042 if let Some((const_val, _)) = const_val;
1043 if let Constant::Int(n) = const_val;
1044 if let ty::Int(ity) = cast_from.kind;
1045 if sext(cx.tcx, n, ity) >= 0;
1051 // don't lint for the result of methods that always return non-negative values
1052 if let ExprKind::MethodCall(ref path, _, _) = op.kind {
1053 let mut method_name = path.ident.name.as_str();
1054 let whitelisted_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
1057 if method_name == "unwrap";
1058 if let Some(arglist) = method_chain_args(op, &["unwrap"]);
1059 if let ExprKind::MethodCall(ref inner_path, _, _) = &arglist[0][0].kind;
1061 method_name = inner_path.ident.name.as_str();
1065 if whitelisted_methods.iter().any(|&name| method_name == name) {
1075 "casting `{}` to `{}` may lose the sign of the value",
1081 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1082 let arch_64_suffix = " on targets with 64-bit wide pointers";
1083 let arch_32_suffix = " on targets with 32-bit wide pointers";
1084 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1085 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1086 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1087 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1088 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1089 (true, true) | (false, false) => (
1090 to_nbits < from_nbits,
1092 to_nbits == from_nbits && cast_unsigned_to_signed,
1102 to_nbits <= 32 && cast_unsigned_to_signed,
1108 cast_unsigned_to_signed,
1109 if from_nbits == 64 {
1116 if span_truncation {
1119 CAST_POSSIBLE_TRUNCATION,
1122 "casting `{}` to `{}` may truncate the value{}",
1125 match suffix_truncation {
1126 ArchSuffix::_32 => arch_32_suffix,
1127 ArchSuffix::_64 => arch_64_suffix,
1128 ArchSuffix::None => "",
1139 "casting `{}` to `{}` may wrap around the value{}",
1143 ArchSuffix::_32 => arch_32_suffix,
1144 ArchSuffix::_64 => arch_64_suffix,
1145 ArchSuffix::None => "",
1152 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr<'_>, op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1153 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1154 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1155 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1156 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1158 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1162 declare_lint_pass!(Casts => [
1163 CAST_PRECISION_LOSS,
1165 CAST_POSSIBLE_TRUNCATION,
1171 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1174 // Check if the given type is either `core::ffi::c_void` or
1175 // one of the platform specific `libc::<platform>::c_void` of libc.
1176 fn is_c_void(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1177 if let ty::Adt(adt, _) = ty.kind {
1178 let names = cx.get_def_path(adt.did);
1180 if names.is_empty() {
1183 if names[0] == sym!(libc) || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
1190 /// Returns the mantissa bits wide of a fp type.
1191 /// Will return 0 if the type is not a fp
1192 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1194 ty::Float(FloatTy::F32) => 23,
1195 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1200 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
1201 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
1202 if expr.span.from_expansion() {
1205 if let ExprKind::Cast(ref ex, _) = expr.kind {
1206 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1207 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1208 if let ExprKind::Lit(ref lit) = ex.kind {
1209 if let LitKind::Int(n, _) = lit.node {
1210 if cast_to.is_floating_point() {
1211 let from_nbits = 128 - n.leading_zeros();
1212 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1213 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1218 &format!("casting integer literal to `{}` is unnecessary", cast_to),
1220 format!("{}_{}", n, cast_to),
1221 Applicability::MachineApplicable,
1228 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
1230 if cast_from.kind == cast_to.kind && !in_external_macro(cx.sess(), expr.span) {
1236 "casting to the same type is unnecessary (`{}` -> `{}`)",
1244 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1245 lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
1248 lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
1253 fn lint_numeric_casts<'tcx>(
1254 cx: &LateContext<'_, 'tcx>,
1256 cast_expr: &Expr<'_>,
1257 cast_from: Ty<'tcx>,
1260 match (cast_from.is_integral(), cast_to.is_integral()) {
1262 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1263 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind {
1268 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1269 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1271 if from_nbits < to_nbits {
1272 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1278 CAST_POSSIBLE_TRUNCATION,
1280 &format!("casting `{}` to `{}` may truncate the value", cast_from, cast_to),
1282 if !cast_to.is_signed() {
1288 "casting `{}` to `{}` may lose the sign of the value",
1295 check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
1296 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1297 check_lossless(cx, expr, cast_expr, cast_from, cast_to);
1300 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.kind, &cast_to.kind) {
1303 CAST_POSSIBLE_TRUNCATION,
1305 "casting `f64` to `f32` may truncate the value",
1308 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.kind, &cast_to.kind) {
1309 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1315 fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
1317 if let ty::RawPtr(from_ptr_ty) = &cast_from.kind;
1318 if let ty::RawPtr(to_ptr_ty) = &cast_to.kind;
1319 if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
1320 if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
1321 if from_layout.align.abi < to_layout.align.abi;
1322 // with c_void, we inherently need to trust the user
1323 if !is_c_void(cx, from_ptr_ty.ty);
1324 // when casting from a ZST, we don't know enough to properly lint
1325 if !from_layout.is_zst();
1332 "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
1335 from_layout.align.abi.bytes(),
1336 to_layout.align.abi.bytes(),
1343 fn lint_fn_to_numeric_cast(
1344 cx: &LateContext<'_, '_>,
1346 cast_expr: &Expr<'_>,
1350 // We only want to check casts to `ty::Uint` or `ty::Int`
1351 match cast_to.kind {
1352 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1355 match cast_from.kind {
1356 ty::FnDef(..) | ty::FnPtr(_) => {
1357 let mut applicability = Applicability::MaybeIncorrect;
1358 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1360 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1361 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1364 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1367 "casting function pointer `{}` to `{}`, which truncates the value",
1368 from_snippet, cast_to
1371 format!("{} as usize", from_snippet),
1374 } else if cast_to.kind != ty::Uint(UintTy::Usize) {
1379 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1381 format!("{} as usize", from_snippet),
1390 declare_clippy_lint! {
1391 /// **What it does:** Checks for types used in structs, parameters and `let`
1392 /// declarations above a certain complexity threshold.
1394 /// **Why is this bad?** Too complex types make the code less readable. Consider
1395 /// using a `type` definition to simplify them.
1397 /// **Known problems:** None.
1401 /// # use std::rc::Rc;
1403 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1406 pub TYPE_COMPLEXITY,
1408 "usage of very complex types that might be better factored into `type` definitions"
1411 pub struct TypeComplexity {
1415 impl TypeComplexity {
1417 pub fn new(threshold: u64) -> Self {
1422 impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
1424 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexity {
1427 cx: &LateContext<'a, 'tcx>,
1429 decl: &'tcx FnDecl<'_>,
1434 self.check_fndecl(cx, decl);
1437 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField<'_>) {
1438 // enum variants are also struct fields now
1439 self.check_type(cx, &field.ty);
1442 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
1444 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1445 // functions, enums, structs, impls and traits are covered
1450 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem<'_>) {
1452 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1453 TraitItemKind::Method(FnSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1454 // methods with default impl are covered by check_fn
1459 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem<'_>) {
1461 ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
1462 // methods are covered by check_fn
1467 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>) {
1468 if let Some(ref ty) = local.ty {
1469 self.check_type(cx, ty);
1474 impl<'a, 'tcx> TypeComplexity {
1475 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl<'_>) {
1476 for arg in decl.inputs {
1477 self.check_type(cx, arg);
1479 if let FunctionRetTy::Return(ref ty) = decl.output {
1480 self.check_type(cx, ty);
1484 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty<'_>) {
1485 if ty.span.from_expansion() {
1489 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1490 visitor.visit_ty(ty);
1494 if score > self.threshold {
1499 "very complex type used. Consider factoring parts into `type` definitions",
1505 /// Walks a type and assigns a complexity score to it.
1506 struct TypeComplexityVisitor {
1507 /// total complexity score of the type
1509 /// current nesting level
1513 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1514 type Map = Map<'tcx>;
1516 fn visit_ty(&mut self, ty: &'tcx hir::Ty<'_>) {
1517 let (add_score, sub_nest) = match ty.kind {
1518 // _, &x and *x have only small overhead; don't mess with nesting level
1519 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1521 // the "normal" components of a type: named types, arrays/tuples
1522 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1524 // function types bring a lot of overhead
1525 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1527 TyKind::TraitObject(ref param_bounds, _) => {
1528 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1529 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1530 GenericParamKind::Lifetime { .. } => true,
1534 if has_lifetime_parameters {
1535 // complex trait bounds like A<'a, 'b>
1538 // simple trait bounds like A + B
1545 self.score += add_score;
1546 self.nest += sub_nest;
1548 self.nest -= sub_nest;
1550 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
1551 NestedVisitorMap::None
1555 declare_clippy_lint! {
1556 /// **What it does:** Checks for expressions where a character literal is cast
1557 /// to `u8` and suggests using a byte literal instead.
1559 /// **Why is this bad?** In general, casting values to smaller types is
1560 /// error-prone and should be avoided where possible. In the particular case of
1561 /// converting a character literal to u8, it is easy to avoid by just using a
1562 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1563 /// than `'a' as u8`.
1565 /// **Known problems:** None.
1572 /// A better version, using the byte literal:
1579 "casting a character literal to `u8` truncates"
1582 declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
1584 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1585 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
1587 if !expr.span.from_expansion();
1588 if let ExprKind::Cast(e, _) = &expr.kind;
1589 if let ExprKind::Lit(l) = &e.kind;
1590 if let LitKind::Char(c) = l.node;
1591 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).kind;
1593 let mut applicability = Applicability::MachineApplicable;
1594 let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
1600 "casting a character literal to `u8` truncates",
1602 db.note("`char` is four bytes wide, but `u8` is a single byte");
1607 "use a byte literal instead",
1608 format!("b{}", snippet),
1618 declare_clippy_lint! {
1619 /// **What it does:** Checks for comparisons where one side of the relation is
1620 /// either the minimum or maximum value for its type and warns if it involves a
1621 /// case that is always true or always false. Only integer and boolean types are
1624 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1625 /// that it is possible for `x` to be less than the minimum. Expressions like
1626 /// `max < x` are probably mistakes.
1628 /// **Known problems:** For `usize` the size of the current compile target will
1629 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1630 /// a comparison to detect target pointer width will trigger this lint. One can
1631 /// use `mem::sizeof` and compare its value or conditional compilation
1633 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1638 /// let vec: Vec<isize> = vec![];
1639 /// if vec.len() <= 0 {}
1640 /// if 100 > std::i32::MAX {}
1642 pub ABSURD_EXTREME_COMPARISONS,
1644 "a comparison with a maximum or minimum value that is always true or false"
1647 declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
1654 struct ExtremeExpr<'a> {
1659 enum AbsurdComparisonResult {
1662 InequalityImpossible,
1665 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
1666 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1667 let precast_ty = cx.tables.expr_ty(cast_exp);
1668 let cast_ty = cx.tables.expr_ty(expr);
1670 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1676 fn detect_absurd_comparison<'a, 'tcx>(
1677 cx: &LateContext<'a, 'tcx>,
1679 lhs: &'tcx Expr<'_>,
1680 rhs: &'tcx Expr<'_>,
1681 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1682 use crate::types::AbsurdComparisonResult::*;
1683 use crate::types::ExtremeType::*;
1684 use crate::utils::comparisons::*;
1686 // absurd comparison only makes sense on primitive types
1687 // primitive types don't implement comparison operators with each other
1688 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1692 // comparisons between fix sized types and target sized types are considered unanalyzable
1693 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1697 let normalized = normalize_comparison(op, lhs, rhs);
1698 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1704 let lx = detect_extreme_expr(cx, normalized_lhs);
1705 let rx = detect_extreme_expr(cx, normalized_rhs);
1710 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1711 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1717 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1718 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1719 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1720 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1724 Rel::Ne | Rel::Eq => return None,
1728 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) -> Option<ExtremeExpr<'tcx>> {
1729 use crate::types::ExtremeType::*;
1731 let ty = cx.tables.expr_ty(expr);
1733 let cv = constant(cx, cx.tables, expr)?.0;
1735 let which = match (&ty.kind, cv) {
1736 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1737 (&ty::Int(ity), Constant::Int(i))
1738 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1743 (&ty::Bool, Constant::Bool(true)) => Maximum,
1744 (&ty::Int(ity), Constant::Int(i))
1745 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1749 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1753 Some(ExtremeExpr { which, expr })
1756 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1757 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
1758 use crate::types::AbsurdComparisonResult::*;
1759 use crate::types::ExtremeType::*;
1761 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
1762 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1763 if !expr.span.from_expansion() {
1764 let msg = "this comparison involving the minimum or maximum element for this \
1765 type contains a case that is always true or always false";
1767 let conclusion = match result {
1768 AlwaysFalse => "this comparison is always false".to_owned(),
1769 AlwaysTrue => "this comparison is always true".to_owned(),
1770 InequalityImpossible => format!(
1771 "the case where the two sides are not equal never occurs, consider using `{} == {}` \
1773 snippet(cx, lhs.span, "lhs"),
1774 snippet(cx, rhs.span, "rhs")
1779 "because `{}` is the {} value for this type, {}",
1780 snippet(cx, culprit.expr.span, "x"),
1781 match culprit.which {
1782 Minimum => "minimum",
1783 Maximum => "maximum",
1788 span_lint_and_help(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1795 declare_clippy_lint! {
1796 /// **What it does:** Checks for comparisons where the relation is always either
1797 /// true or false, but where one side has been upcast so that the comparison is
1798 /// necessary. Only integer types are checked.
1800 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1801 /// will mistakenly imply that it is possible for `x` to be outside the range of
1804 /// **Known problems:**
1805 /// https://github.com/rust-lang/rust-clippy/issues/886
1810 /// (x as u32) > 300;
1812 pub INVALID_UPCAST_COMPARISONS,
1814 "a comparison involving an upcast which is always true or false"
1817 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
1819 #[derive(Copy, Clone, Debug, Eq)]
1826 #[allow(clippy::cast_sign_loss)]
1828 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1831 } else if u > (i128::max_value() as u128) {
1839 impl PartialEq for FullInt {
1841 fn eq(&self, other: &Self) -> bool {
1842 self.partial_cmp(other).expect("`partial_cmp` only returns `Some(_)`") == Ordering::Equal
1846 impl PartialOrd for FullInt {
1848 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1849 Some(match (self, other) {
1850 (&Self::S(s), &Self::S(o)) => s.cmp(&o),
1851 (&Self::U(s), &Self::U(o)) => s.cmp(&o),
1852 (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
1853 (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
1857 impl Ord for FullInt {
1859 fn cmp(&self, other: &Self) -> Ordering {
1860 self.partial_cmp(other)
1861 .expect("`partial_cmp` for FullInt can never return `None`")
1865 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr<'_>) -> Option<(FullInt, FullInt)> {
1868 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1869 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1870 let cast_ty = cx.tables.expr_ty(expr);
1871 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1872 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1875 match pre_cast_ty.kind {
1876 ty::Int(int_ty) => Some(match int_ty {
1878 FullInt::S(i128::from(i8::min_value())),
1879 FullInt::S(i128::from(i8::max_value())),
1882 FullInt::S(i128::from(i16::min_value())),
1883 FullInt::S(i128::from(i16::max_value())),
1886 FullInt::S(i128::from(i32::min_value())),
1887 FullInt::S(i128::from(i32::max_value())),
1890 FullInt::S(i128::from(i64::min_value())),
1891 FullInt::S(i128::from(i64::max_value())),
1893 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1895 FullInt::S(isize::min_value() as i128),
1896 FullInt::S(isize::max_value() as i128),
1899 ty::Uint(uint_ty) => Some(match uint_ty {
1901 FullInt::U(u128::from(u8::min_value())),
1902 FullInt::U(u128::from(u8::max_value())),
1905 FullInt::U(u128::from(u16::min_value())),
1906 FullInt::U(u128::from(u16::max_value())),
1909 FullInt::U(u128::from(u32::min_value())),
1910 FullInt::U(u128::from(u32::max_value())),
1913 FullInt::U(u128::from(u64::min_value())),
1914 FullInt::U(u128::from(u64::max_value())),
1916 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1918 FullInt::U(usize::min_value() as u128),
1919 FullInt::U(usize::max_value() as u128),
1929 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) -> Option<FullInt> {
1930 let val = constant(cx, cx.tables, expr)?.0;
1931 if let Constant::Int(const_int) = val {
1932 match cx.tables.expr_ty(expr).kind {
1933 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1934 ty::Uint(_) => Some(FullInt::U(const_int)),
1942 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr<'_>, always: bool) {
1943 if let ExprKind::Cast(ref cast_val, _) = expr.kind {
1946 INVALID_UPCAST_COMPARISONS,
1949 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1950 snippet(cx, cast_val.span, "the expression"),
1951 if always { "true" } else { "false" },
1957 fn upcast_comparison_bounds_err<'a, 'tcx>(
1958 cx: &LateContext<'a, 'tcx>,
1960 rel: comparisons::Rel,
1961 lhs_bounds: Option<(FullInt, FullInt)>,
1962 lhs: &'tcx Expr<'_>,
1963 rhs: &'tcx Expr<'_>,
1966 use crate::utils::comparisons::*;
1968 if let Some((lb, ub)) = lhs_bounds {
1969 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1970 if rel == Rel::Eq || rel == Rel::Ne {
1971 if norm_rhs_val < lb || norm_rhs_val > ub {
1972 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1974 } else if match rel {
1989 Rel::Eq | Rel::Ne => unreachable!(),
1991 err_upcast_comparison(cx, span, lhs, true)
1992 } else if match rel {
2007 Rel::Eq | Rel::Ne => unreachable!(),
2009 err_upcast_comparison(cx, span, lhs, false)
2015 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
2016 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
2017 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
2018 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
2019 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
2025 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
2026 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
2028 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
2029 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
2034 declare_clippy_lint! {
2035 /// **What it does:** Checks for public `impl` or `fn` missing generalization
2036 /// over different hashers and implicitly defaulting to the default hashing
2037 /// algorithm (`SipHash`).
2039 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
2042 /// **Known problems:** Suggestions for replacing constructors can contain
2043 /// false-positives. Also applying suggestions can require modification of other
2044 /// pieces of code, possibly including external crates.
2048 /// # use std::collections::HashMap;
2049 /// # use std::hash::{Hash, BuildHasher};
2050 /// # trait Serialize {};
2051 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
2053 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
2055 /// could be rewritten as
2057 /// # use std::collections::HashMap;
2058 /// # use std::hash::{Hash, BuildHasher};
2059 /// # trait Serialize {};
2060 /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
2062 /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
2064 pub IMPLICIT_HASHER,
2066 "missing generalization over different hashers"
2069 declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
2071 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
2072 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
2073 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
2074 use rustc_span::BytePos;
2076 fn suggestion<'a, 'tcx>(
2077 cx: &LateContext<'a, 'tcx>,
2078 db: &mut DiagnosticBuilder<'_>,
2079 generics_span: Span,
2080 generics_suggestion_span: Span,
2081 target: &ImplicitHasherType<'_>,
2082 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2084 let generics_snip = snippet(cx, generics_span, "");
2086 let generics_snip = if generics_snip.is_empty() {
2089 &generics_snip[1..generics_snip.len() - 1]
2094 "consider adding a type parameter".to_string(),
2097 generics_suggestion_span,
2099 "<{}{}S: ::std::hash::BuildHasher{}>",
2101 if generics_snip.is_empty() { "" } else { ", " },
2102 if vis.suggestions.is_empty() {
2105 // request users to add `Default` bound so that generic constructors can be used
2112 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2117 if !vis.suggestions.is_empty() {
2118 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2122 if !cx.access_levels.is_exported(item.hir_id) {
2133 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2136 for target in &vis.found {
2137 if differing_macro_contexts(item.span, target.span()) {
2141 let generics_suggestion_span = generics.span.substitute_dummy({
2142 let pos = snippet_opt(cx, item.span.until(target.span()))
2143 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2144 if let Some(pos) = pos {
2145 Span::new(pos, pos, item.span.data().ctxt)
2151 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2152 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2153 ctr_vis.visit_impl_item(item);
2161 "impl for `{}` should be generalized over different hashers",
2165 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2170 ItemKind::Fn(ref sig, ref generics, body_id) => {
2171 let body = cx.tcx.hir().body(body_id);
2173 for ty in sig.decl.inputs {
2174 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2177 for target in &vis.found {
2178 if in_external_macro(cx.sess(), generics.span) {
2181 let generics_suggestion_span = generics.span.substitute_dummy({
2182 let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
2184 let i = snip.find("fn")?;
2185 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2187 .expect("failed to create span for type parameters");
2188 Span::new(pos, pos, item.span.data().ctxt)
2191 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2192 ctr_vis.visit_body(body);
2199 "parameter of type `{}` should be generalized over different hashers",
2203 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2214 enum ImplicitHasherType<'tcx> {
2215 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2216 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2219 impl<'tcx> ImplicitHasherType<'tcx> {
2220 /// Checks that `ty` is a target type without a `BuildHasher`.
2221 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty<'_>) -> Option<Self> {
2222 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.kind {
2223 let params: Vec<_> = path
2231 .filter_map(|arg| match arg {
2232 GenericArg::Type(ty) => Some(ty),
2236 let params_len = params.len();
2238 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2240 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2241 Some(ImplicitHasherType::HashMap(
2244 snippet(cx, params[0].span, "K"),
2245 snippet(cx, params[1].span, "V"),
2247 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2248 Some(ImplicitHasherType::HashSet(
2251 snippet(cx, params[0].span, "T"),
2261 fn type_name(&self) -> &'static str {
2263 ImplicitHasherType::HashMap(..) => "HashMap",
2264 ImplicitHasherType::HashSet(..) => "HashSet",
2268 fn type_arguments(&self) -> String {
2270 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2271 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2275 fn ty(&self) -> Ty<'tcx> {
2277 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2281 fn span(&self) -> Span {
2283 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2288 struct ImplicitHasherTypeVisitor<'a, 'tcx> {
2289 cx: &'a LateContext<'a, 'tcx>,
2290 found: Vec<ImplicitHasherType<'tcx>>,
2293 impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
2294 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2295 Self { cx, found: vec![] }
2299 impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2300 type Map = Map<'tcx>;
2302 fn visit_ty(&mut self, t: &'tcx hir::Ty<'_>) {
2303 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2304 self.found.push(target);
2310 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
2311 NestedVisitorMap::None
2315 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2316 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2317 cx: &'a LateContext<'a, 'tcx>,
2318 body: &'a TypeckTables<'tcx>,
2319 target: &'b ImplicitHasherType<'tcx>,
2320 suggestions: BTreeMap<Span, String>,
2323 impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2324 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2329 suggestions: BTreeMap::new(),
2334 impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2335 type Map = Map<'tcx>;
2337 fn visit_body(&mut self, body: &'tcx Body<'_>) {
2338 let prev_body = self.body;
2339 self.body = self.cx.tcx.body_tables(body.id());
2340 walk_body(self, body);
2341 self.body = prev_body;
2344 fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
2346 if let ExprKind::Call(ref fun, ref args) = e.kind;
2347 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.kind;
2348 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.kind;
2350 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2354 if match_path(ty_path, &paths::HASHMAP) {
2355 if method.ident.name == sym!(new) {
2357 .insert(e.span, "HashMap::default()".to_string());
2358 } else if method.ident.name == sym!(with_capacity) {
2359 self.suggestions.insert(
2362 "HashMap::with_capacity_and_hasher({}, Default::default())",
2363 snippet(self.cx, args[0].span, "capacity"),
2367 } else if match_path(ty_path, &paths::HASHSET) {
2368 if method.ident.name == sym!(new) {
2370 .insert(e.span, "HashSet::default()".to_string());
2371 } else if method.ident.name == sym!(with_capacity) {
2372 self.suggestions.insert(
2375 "HashSet::with_capacity_and_hasher({}, Default::default())",
2376 snippet(self.cx, args[0].span, "capacity"),
2387 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
2388 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2392 declare_clippy_lint! {
2393 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2395 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2396 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2399 /// **Known problems:** None.
2405 /// *(r as *const _ as *mut _) += 1;
2410 /// Instead consider using interior mutability types.
2413 /// use std::cell::UnsafeCell;
2415 /// fn x(r: &UnsafeCell<i32>) {
2421 pub CAST_REF_TO_MUT,
2423 "a cast of reference to a mutable pointer"
2426 declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
2428 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2429 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
2431 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.kind;
2432 if let ExprKind::Cast(e, t) = &e.kind;
2433 if let TyKind::Ptr(MutTy { mutbl: Mutability::Mut, .. }) = t.kind;
2434 if let ExprKind::Cast(e, t) = &e.kind;
2435 if let TyKind::Ptr(MutTy { mutbl: Mutability::Not, .. }) = t.kind;
2436 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).kind;
2442 "casting `&T` to `&mut T` may cause undefined behavior, consider instead using an `UnsafeCell`",