1 #![allow(clippy::default_hash_types)]
3 use crate::consts::{constant, Constant};
4 use crate::reexport::*;
5 use crate::utils::paths;
7 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
8 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
9 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
12 use if_chain::if_chain;
14 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
16 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
17 use rustc::ty::layout::LayoutOf;
18 use rustc::ty::{self, Ty, TyCtxt, TypeckTables};
19 use rustc::{declare_tool_lint, lint_array};
20 use rustc_errors::Applicability;
21 use rustc_target::spec::abi::Abi;
22 use rustc_typeck::hir_ty_to_ty;
24 use std::cmp::Ordering;
25 use std::collections::BTreeMap;
26 use syntax::ast::{FloatTy, IntTy, UintTy};
27 use syntax::errors::DiagnosticBuilder;
28 use syntax::source_map::Span;
30 /// Handles all the linting of funky types
33 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
35 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
36 /// the heap. So if you `Box` it, you just add another level of indirection
37 /// without any benefit whatsoever.
39 /// **Known problems:** None.
44 /// values: Box<Vec<Foo>>,
55 declare_clippy_lint! {
58 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
61 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
63 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
64 /// the heap. So if you `Box` its contents, you just add another level of indirection.
66 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
72 /// values: Vec<Box<i32>>,
83 declare_clippy_lint! {
86 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
89 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
92 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
93 /// represents an optional optional value which is logically the same thing as an optional
94 /// value but has an unneeded extra level of wrapping.
96 /// **Known problems:** None.
100 /// fn x() -> Option<Option<u32>> {
103 declare_clippy_lint! {
106 "usage of `Option<Option<T>>`"
109 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
110 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
112 /// **Why is this bad?** Gankro says:
114 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
115 /// pointers and indirection.
116 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
118 /// > "only" amortized for push/pop, should be faster in the general case for
119 /// almost every possible
120 /// > workload, and isn't even amortized at all if you can predict the capacity
123 /// > `LinkedList`s are only really good if you're doing a lot of merging or
124 /// splitting of lists.
125 /// > This is because they can just mangle some pointers instead of actually
126 /// copying the data. Even
127 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
128 /// can still be better
129 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
131 /// **Known problems:** False positives – the instances where using a
132 /// `LinkedList` makes sense are few and far between, but they can still happen.
136 /// let x = LinkedList::new();
138 declare_clippy_lint! {
141 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
144 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
146 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
149 /// **Known problems:** None.
153 /// fn foo(bar: &Box<T>) { ... }
159 /// fn foo(bar: &T) { ... }
161 declare_clippy_lint! {
164 "a borrow of a boxed type"
167 impl LintPass for TypePass {
168 fn get_lints(&self) -> LintArray {
169 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
172 fn name(&self) -> &'static str {
177 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
178 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
179 // skip trait implementations, see #605
180 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(id)) {
181 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
186 check_fn_decl(cx, decl);
189 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
190 check_ty(cx, &field.ty, false);
193 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
195 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
196 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
201 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
202 if let Some(ref ty) = local.ty {
203 check_ty(cx, ty, true);
208 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
209 for input in &decl.inputs {
210 check_ty(cx, input, false);
213 if let FunctionRetTy::Return(ref ty) = decl.output {
214 check_ty(cx, ty, false);
218 /// Check if `qpath` has last segment with type parameter matching `path`
219 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
220 let last = last_path_segment(qpath);
222 if let Some(ref params) = last.args;
223 if !params.parenthesized;
224 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
225 GenericArg::Type(ty) => Some(ty),
226 GenericArg::Lifetime(_) => None,
228 if let TyKind::Path(ref qpath) = ty.node;
229 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
230 if match_def_path(cx.tcx, did, path);
238 /// Recursively check for `TypePass` lints in the given type. Stop at the first
241 /// The parameter `is_local` distinguishes the context of the type; types from
242 /// local bindings should only be checked for the `BORROWED_BOX` lint.
243 #[allow(clippy::too_many_lines)]
244 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
245 if in_macro(hir_ty.span) {
249 TyKind::Path(ref qpath) if !is_local => {
250 let hir_id = cx.tcx.hir().node_to_hir_id(hir_ty.id);
251 let def = cx.tables.qpath_def(qpath, hir_id);
252 if let Some(def_id) = opt_def_id(def) {
253 if Some(def_id) == cx.tcx.lang_items().owned_box() {
254 if match_type_parameter(cx, qpath, &paths::VEC) {
259 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
260 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
262 return; // don't recurse into the type
264 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
266 // Get the _ part of Vec<_>
267 if let Some(ref last) = last_path_segment(qpath).args;
268 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
269 GenericArg::Type(ty) => Some(ty),
270 GenericArg::Lifetime(_) => None,
272 // ty is now _ at this point
273 if let TyKind::Path(ref ty_qpath) = ty.node;
274 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
275 if let Some(def_id) = opt_def_id(def);
276 if Some(def_id) == cx.tcx.lang_items().owned_box();
277 // At this point, we know ty is Box<T>, now get T
278 if let Some(ref last) = last_path_segment(ty_qpath).args;
279 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
280 GenericArg::Type(ty) => Some(ty),
281 GenericArg::Lifetime(_) => None,
283 if let TyKind::Path(ref ty_qpath) = ty.node;
284 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
285 if let Some(def_id) = opt_def_id(def);
286 let boxed_type = cx.tcx.type_of(def_id);
287 if boxed_type.is_sized(cx.tcx.at(ty.span), cx.param_env);
293 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
295 format!("Vec<{}>", boxed_type),
296 Applicability::MaybeIncorrect,
298 return; // don't recurse into the type
301 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
302 if match_type_parameter(cx, qpath, &paths::OPTION) {
307 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
308 enum if you need to distinguish all 3 cases",
310 return; // don't recurse into the type
312 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
317 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
318 "a VecDeque might work",
320 return; // don't recurse into the type
324 QPath::Resolved(Some(ref ty), ref p) => {
325 check_ty(cx, ty, is_local);
326 for ty in p.segments.iter().flat_map(|seg| {
329 .map_or_else(|| [].iter(), |params| params.args.iter())
330 .filter_map(|arg| match arg {
331 GenericArg::Type(ty) => Some(ty),
332 GenericArg::Lifetime(_) => None,
335 check_ty(cx, ty, is_local);
338 QPath::Resolved(None, ref p) => {
339 for ty in p.segments.iter().flat_map(|seg| {
342 .map_or_else(|| [].iter(), |params| params.args.iter())
343 .filter_map(|arg| match arg {
344 GenericArg::Type(ty) => Some(ty),
345 GenericArg::Lifetime(_) => None,
348 check_ty(cx, ty, is_local);
351 QPath::TypeRelative(ref ty, ref seg) => {
352 check_ty(cx, ty, is_local);
353 if let Some(ref params) = seg.args {
354 for ty in params.args.iter().filter_map(|arg| match arg {
355 GenericArg::Type(ty) => Some(ty),
356 GenericArg::Lifetime(_) => None,
358 check_ty(cx, ty, is_local);
364 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
366 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
367 check_ty(cx, ty, is_local)
369 TyKind::Tup(ref tys) => {
371 check_ty(cx, ty, is_local);
378 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
379 match mut_ty.ty.node {
380 TyKind::Path(ref qpath) => {
381 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
382 let def = cx.tables.qpath_def(qpath, hir_id);
384 if let Some(def_id) = opt_def_id(def);
385 if Some(def_id) == cx.tcx.lang_items().owned_box();
386 if let QPath::Resolved(None, ref path) = *qpath;
387 if let [ref bx] = *path.segments;
388 if let Some(ref params) = bx.args;
389 if !params.parenthesized;
390 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
391 GenericArg::Type(ty) => Some(ty),
392 GenericArg::Lifetime(_) => None,
395 if is_any_trait(inner) {
396 // Ignore `Box<Any>` types, see #1884 for details.
400 let ltopt = if lt.is_elided() {
403 format!("{} ", lt.name.ident().as_str())
405 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
410 let mut applicability = Applicability::MachineApplicable;
415 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
421 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
423 Applicability::Unspecified,
425 return; // don't recurse into the type
428 check_ty(cx, &mut_ty.ty, is_local);
430 _ => check_ty(cx, &mut_ty.ty, is_local),
434 // Returns true if given type is `Any` trait.
435 fn is_any_trait(t: &hir::Ty) -> bool {
437 if let TyKind::TraitObject(ref traits, _) = t.node;
438 if traits.len() >= 1;
439 // Only Send/Sync can be used as additional traits, so it is enough to
440 // check only the first trait.
441 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
452 /// **What it does:** Checks for binding a unit value.
454 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
455 /// binding one is kind of pointless.
457 /// **Known problems:** None.
465 declare_clippy_lint! {
468 "creating a let binding to a value of unit type, which usually can't be used afterwards"
471 impl LintPass for LetPass {
472 fn get_lints(&self) -> LintArray {
473 lint_array!(LET_UNIT_VALUE)
476 fn name(&self) -> &'static str {
481 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
482 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
483 if let StmtKind::Local(ref local) = stmt.node {
484 if is_unit(cx.tables.pat_ty(&local.pat)) {
485 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
488 if higher::is_from_for_desugar(local) {
496 "this let-binding has unit value. Consider omitting `let {} =`",
497 snippet(cx, local.pat.span, "..")
505 /// **What it does:** Checks for comparisons to unit.
507 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
508 /// clumsily written constant. Mostly this happens when someone accidentally
509 /// adds semicolons at the end of the operands.
511 /// **Known problems:** None.
531 declare_clippy_lint! {
534 "comparing unit values"
539 impl LintPass for UnitCmp {
540 fn get_lints(&self) -> LintArray {
541 lint_array!(UNIT_CMP)
544 fn name(&self) -> &'static str {
549 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
550 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
551 if in_macro(expr.span) {
554 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
556 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
557 let result = match op {
558 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
566 "{}-comparison of unit values detected. This will always be {}",
576 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
577 /// unit literal (`()`).
579 /// **Why is this bad?** This is likely the result of an accidental semicolon.
581 /// **Known problems:** None.
590 declare_clippy_lint! {
593 "passing unit to a function"
598 impl LintPass for UnitArg {
599 fn get_lints(&self) -> LintArray {
600 lint_array!(UNIT_ARG)
603 fn name(&self) -> &'static str {
608 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
609 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
610 if in_macro(expr.span) {
614 // apparently stuff in the desugaring of `?` can trigger this
615 // so check for that here
616 // only the calls to `Try::from_error` is marked as desugared,
617 // so we need to check both the current Expr and its parent.
618 if is_questionmark_desugar_marked_call(expr) {
622 let map = &cx.tcx.hir();
623 let opt_parent_node = map.find(map.get_parent_node(expr.id));
624 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
625 if is_questionmark_desugar_marked_call(parent_expr);
632 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
634 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
635 if let ExprKind::Match(.., match_source) = &arg.node {
636 if *match_source == MatchSource::TryDesugar {
645 "passing a unit value to a function",
646 "if you intended to pass a unit value, use a unit literal instead",
648 Applicability::MachineApplicable,
658 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
659 use syntax_pos::hygiene::CompilerDesugaringKind;
660 if let ExprKind::Call(ref callee, _) = expr.node {
661 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
667 fn is_unit(ty: Ty<'_>) -> bool {
669 ty::Tuple(slice) if slice.is_empty() => true,
674 fn is_unit_literal(expr: &Expr) -> bool {
676 ExprKind::Tup(ref slice) if slice.is_empty() => true,
683 /// **What it does:** Checks for casts from any numerical to a float type where
684 /// the receiving type cannot store all values from the original type without
685 /// rounding errors. This possible rounding is to be expected, so this lint is
686 /// `Allow` by default.
688 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
689 /// or any 64-bit integer to `f64`.
691 /// **Why is this bad?** It's not bad at all. But in some applications it can be
692 /// helpful to know where precision loss can take place. This lint can help find
693 /// those places in the code.
695 /// **Known problems:** None.
699 /// let x = u64::MAX;
702 declare_clippy_lint! {
703 pub CAST_PRECISION_LOSS,
705 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
708 /// **What it does:** Checks for casts from a signed to an unsigned numerical
709 /// type. In this case, negative values wrap around to large positive values,
710 /// which can be quite surprising in practice. However, as the cast works as
711 /// defined, this lint is `Allow` by default.
713 /// **Why is this bad?** Possibly surprising results. You can activate this lint
714 /// as a one-time check to see where numerical wrapping can arise.
716 /// **Known problems:** None.
721 /// y as u128 // will return 18446744073709551615
723 declare_clippy_lint! {
726 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
729 /// **What it does:** Checks for on casts between numerical types that may
730 /// truncate large values. This is expected behavior, so the cast is `Allow` by
733 /// **Why is this bad?** In some problem domains, it is good practice to avoid
734 /// truncation. This lint can be activated to help assess where additional
735 /// checks could be beneficial.
737 /// **Known problems:** None.
741 /// fn as_u8(x: u64) -> u8 {
745 declare_clippy_lint! {
746 pub CAST_POSSIBLE_TRUNCATION,
748 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
751 /// **What it does:** Checks for casts from an unsigned type to a signed type of
752 /// the same size. Performing such a cast is a 'no-op' for the compiler,
753 /// i.e. nothing is changed at the bit level, and the binary representation of
754 /// the value is reinterpreted. This can cause wrapping if the value is too big
755 /// for the target signed type. However, the cast works as defined, so this lint
756 /// is `Allow` by default.
758 /// **Why is this bad?** While such a cast is not bad in itself, the results can
759 /// be surprising when this is not the intended behavior, as demonstrated by the
762 /// **Known problems:** None.
766 /// u32::MAX as i32 // will yield a value of `-1`
768 declare_clippy_lint! {
769 pub CAST_POSSIBLE_WRAP,
771 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
774 /// **What it does:** Checks for on casts between numerical types that may
775 /// be replaced by safe conversion functions.
777 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
778 /// conversions, including silently lossy conversions. Conversion functions such
779 /// as `i32::from` will only perform lossless conversions. Using the conversion
780 /// functions prevents conversions from turning into silent lossy conversions if
781 /// the types of the input expressions ever change, and make it easier for
782 /// people reading the code to know that the conversion is lossless.
784 /// **Known problems:** None.
788 /// fn as_u64(x: u8) -> u64 {
793 /// Using `::from` would look like this:
796 /// fn as_u64(x: u8) -> u64 {
800 declare_clippy_lint! {
803 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
806 /// **What it does:** Checks for casts to the same type.
808 /// **Why is this bad?** It's just unnecessary.
810 /// **Known problems:** None.
814 /// let _ = 2i32 as i32
816 declare_clippy_lint! {
817 pub UNNECESSARY_CAST,
819 "cast to the same type, e.g. `x as i32` where `x: i32`"
822 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
823 /// more-strictly-aligned pointer
825 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
828 /// **Known problems:** None.
832 /// let _ = (&1u8 as *const u8) as *const u16;
833 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
835 declare_clippy_lint! {
836 pub CAST_PTR_ALIGNMENT,
838 "cast from a pointer to a more-strictly-aligned pointer"
841 /// **What it does:** Checks for casts of function pointers to something other than usize
843 /// **Why is this bad?**
844 /// Casting a function pointer to anything other than usize/isize is not portable across
845 /// architectures, because you end up losing bits if the target type is too small or end up with a
846 /// bunch of extra bits that waste space and add more instructions to the final binary than
847 /// strictly necessary for the problem
849 /// Casting to isize also doesn't make sense since there are no signed addresses.
855 /// fn fun() -> i32 {}
856 /// let a = fun as i64;
859 /// fn fun2() -> i32 {}
860 /// let a = fun2 as usize;
862 declare_clippy_lint! {
863 pub FN_TO_NUMERIC_CAST,
865 "casting a function pointer to a numeric type other than usize"
868 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
871 /// **Why is this bad?**
872 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
873 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
874 /// a comment) to perform the truncation.
880 /// fn fn1() -> i16 {
883 /// let _ = fn1 as i32;
885 /// // Better: Cast to usize first, then comment with the reason for the truncation
886 /// fn fn2() -> i16 {
889 /// let fn_ptr = fn2 as usize;
890 /// let fn_ptr_truncated = fn_ptr as i32;
892 declare_clippy_lint! {
893 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
895 "casting a function pointer to a numeric type not wide enough to store the address"
898 /// Returns the size in bits of an integral type.
899 /// Will return 0 if the type is not an int or uint variant
900 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
902 ty::Int(i) => match i {
903 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
910 ty::Uint(i) => match i {
911 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
922 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
924 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
929 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
930 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
931 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
932 let arch_dependent_str = "on targets with 64-bit wide pointers ";
933 let from_nbits_str = if arch_dependent {
935 } else if is_isize_or_usize(cast_from) {
936 "32 or 64".to_owned()
938 int_ty_to_nbits(cast_from, cx.tcx).to_string()
945 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
946 is only {4} bits wide)",
948 if cast_to_f64 { "f64" } else { "f32" },
949 if arch_dependent { arch_dependent_str } else { "" },
956 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
957 if let ExprKind::Binary(_, _, _) = op.node {
958 if snip.starts_with('(') && snip.ends_with(')') {
965 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
966 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
967 if in_constant(cx, expr.id) {
970 // The suggestion is to use a function call, so if the original expression
971 // has parens on the outside, they are no longer needed.
972 let mut applicability = Applicability::MachineApplicable;
973 let opt = snippet_opt(cx, op.span);
974 let sugg = if let Some(ref snip) = opt {
975 if should_strip_parens(op, snip) {
976 &snip[1..snip.len() - 1]
981 applicability = Applicability::HasPlaceholders;
990 "casting {} to {} may become silently lossy if types change",
994 format!("{}::from({})", cast_to, sugg),
1005 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1006 let arch_64_suffix = " on targets with 64-bit wide pointers";
1007 let arch_32_suffix = " on targets with 32-bit wide pointers";
1008 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1009 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1010 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1011 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1012 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1013 (true, true) | (false, false) => (
1014 to_nbits < from_nbits,
1016 to_nbits == from_nbits && cast_unsigned_to_signed,
1026 to_nbits <= 32 && cast_unsigned_to_signed,
1032 cast_unsigned_to_signed,
1033 if from_nbits == 64 {
1040 if span_truncation {
1043 CAST_POSSIBLE_TRUNCATION,
1046 "casting {} to {} may truncate the value{}",
1049 match suffix_truncation {
1050 ArchSuffix::_32 => arch_32_suffix,
1051 ArchSuffix::_64 => arch_64_suffix,
1052 ArchSuffix::None => "",
1063 "casting {} to {} may wrap around the value{}",
1067 ArchSuffix::_32 => arch_32_suffix,
1068 ArchSuffix::_64 => arch_64_suffix,
1069 ArchSuffix::None => "",
1076 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1077 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1078 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1079 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1080 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1082 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1086 impl LintPass for CastPass {
1087 fn get_lints(&self) -> LintArray {
1089 CAST_PRECISION_LOSS,
1091 CAST_POSSIBLE_TRUNCATION,
1097 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1101 fn name(&self) -> &'static str {
1106 // Check if the given type is either `core::ffi::c_void` or
1107 // one of the platform specific `libc::<platform>::c_void` of libc.
1108 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1109 if let ty::Adt(adt, _) = ty.sty {
1110 let mut apb = AbsolutePathBuffer { names: vec![] };
1111 tcx.push_item_path(&mut apb, adt.did, false);
1113 if apb.names.is_empty() {
1116 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1123 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1124 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1125 if let ExprKind::Cast(ref ex, _) = expr.node {
1126 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1127 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1128 if let ExprKind::Lit(ref lit) = ex.node {
1129 use syntax::ast::{LitIntType, LitKind};
1131 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1133 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1139 "casting to the same type is unnecessary (`{}` -> `{}`)",
1147 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1148 match (cast_from.is_integral(), cast_to.is_integral()) {
1150 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1151 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1156 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1157 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1159 if from_nbits < to_nbits {
1160 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1166 CAST_POSSIBLE_TRUNCATION,
1168 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1170 if !cast_to.is_signed() {
1175 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1180 if cast_from.is_signed() && !cast_to.is_signed() {
1185 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1188 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1189 check_lossless(cx, expr, ex, cast_from, cast_to);
1192 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1195 CAST_POSSIBLE_TRUNCATION,
1197 "casting f64 to f32 may truncate the value",
1200 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1201 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1208 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1209 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1210 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1211 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1212 if from_align < to_align;
1213 // with c_void, we inherently need to trust the user
1214 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1220 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1228 fn lint_fn_to_numeric_cast(
1229 cx: &LateContext<'_, '_>,
1235 // We only want to check casts to `ty::Uint` or `ty::Int`
1237 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1240 match cast_from.sty {
1241 ty::FnDef(..) | ty::FnPtr(_) => {
1242 let mut applicability = Applicability::MachineApplicable;
1243 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1245 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1246 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1249 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1252 "casting function pointer `{}` to `{}`, which truncates the value",
1253 from_snippet, cast_to
1256 format!("{} as usize", from_snippet),
1259 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1264 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1266 format!("{} as usize", from_snippet),
1275 /// **What it does:** Checks for types used in structs, parameters and `let`
1276 /// declarations above a certain complexity threshold.
1278 /// **Why is this bad?** Too complex types make the code less readable. Consider
1279 /// using a `type` definition to simplify them.
1281 /// **Known problems:** None.
1286 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1289 declare_clippy_lint! {
1290 pub TYPE_COMPLEXITY,
1292 "usage of very complex types that might be better factored into `type` definitions"
1295 pub struct TypeComplexityPass {
1299 impl TypeComplexityPass {
1300 pub fn new(threshold: u64) -> Self {
1305 impl LintPass for TypeComplexityPass {
1306 fn get_lints(&self) -> LintArray {
1307 lint_array!(TYPE_COMPLEXITY)
1310 fn name(&self) -> &'static str {
1311 "TypeComplexityPass"
1315 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1318 cx: &LateContext<'a, 'tcx>,
1325 self.check_fndecl(cx, decl);
1328 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1329 // enum variants are also struct fields now
1330 self.check_type(cx, &field.ty);
1333 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1335 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1336 // functions, enums, structs, impls and traits are covered
1341 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1343 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1344 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1345 // methods with default impl are covered by check_fn
1350 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1352 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1353 // methods are covered by check_fn
1358 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1359 if let Some(ref ty) = local.ty {
1360 self.check_type(cx, ty);
1365 impl<'a, 'tcx> TypeComplexityPass {
1366 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1367 for arg in &decl.inputs {
1368 self.check_type(cx, arg);
1370 if let Return(ref ty) = decl.output {
1371 self.check_type(cx, ty);
1375 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1376 if in_macro(ty.span) {
1380 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1381 visitor.visit_ty(ty);
1385 if score > self.threshold {
1390 "very complex type used. Consider factoring parts into `type` definitions",
1396 /// Walks a type and assigns a complexity score to it.
1397 struct TypeComplexityVisitor {
1398 /// total complexity score of the type
1400 /// current nesting level
1404 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1405 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1406 let (add_score, sub_nest) = match ty.node {
1407 // _, &x and *x have only small overhead; don't mess with nesting level
1408 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1410 // the "normal" components of a type: named types, arrays/tuples
1411 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1413 // function types bring a lot of overhead
1414 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1416 TyKind::TraitObject(ref param_bounds, _) => {
1417 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1418 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1419 GenericParamKind::Lifetime { .. } => true,
1423 if has_lifetime_parameters {
1424 // complex trait bounds like A<'a, 'b>
1427 // simple trait bounds like A + B
1434 self.score += add_score;
1435 self.nest += sub_nest;
1437 self.nest -= sub_nest;
1439 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1440 NestedVisitorMap::None
1444 /// **What it does:** Checks for expressions where a character literal is cast
1445 /// to `u8` and suggests using a byte literal instead.
1447 /// **Why is this bad?** In general, casting values to smaller types is
1448 /// error-prone and should be avoided where possible. In the particular case of
1449 /// converting a character literal to u8, it is easy to avoid by just using a
1450 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1451 /// than `'a' as u8`.
1453 /// **Known problems:** None.
1460 /// A better version, using the byte literal:
1465 declare_clippy_lint! {
1468 "casting a character literal to u8"
1471 pub struct CharLitAsU8;
1473 impl LintPass for CharLitAsU8 {
1474 fn get_lints(&self) -> LintArray {
1475 lint_array!(CHAR_LIT_AS_U8)
1478 fn name(&self) -> &'static str {
1483 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1484 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1485 use syntax::ast::{LitKind, UintTy};
1487 if let ExprKind::Cast(ref e, _) = expr.node {
1488 if let ExprKind::Lit(ref l) = e.node {
1489 if let LitKind::Char(_) = l.node {
1490 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1491 let msg = "casting character literal to u8. `char`s \
1492 are 4 bytes wide in rust, so casting to u8 \
1495 "Consider using a byte literal instead:\nb{}",
1496 snippet(cx, e.span, "'x'")
1498 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1506 /// **What it does:** Checks for comparisons where one side of the relation is
1507 /// either the minimum or maximum value for its type and warns if it involves a
1508 /// case that is always true or always false. Only integer and boolean types are
1511 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1512 /// that is is possible for `x` to be less than the minimum. Expressions like
1513 /// `max < x` are probably mistakes.
1515 /// **Known problems:** For `usize` the size of the current compile target will
1516 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1517 /// a comparison to detect target pointer width will trigger this lint. One can
1518 /// use `mem::sizeof` and compare its value or conditional compilation
1520 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1525 /// 100 > std::i32::MAX
1527 declare_clippy_lint! {
1528 pub ABSURD_EXTREME_COMPARISONS,
1530 "a comparison with a maximum or minimum value that is always true or false"
1533 pub struct AbsurdExtremeComparisons;
1535 impl LintPass for AbsurdExtremeComparisons {
1536 fn get_lints(&self) -> LintArray {
1537 lint_array!(ABSURD_EXTREME_COMPARISONS)
1540 fn name(&self) -> &'static str {
1541 "AbsurdExtremeComparisons"
1550 struct ExtremeExpr<'a> {
1555 enum AbsurdComparisonResult {
1558 InequalityImpossible,
1561 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1562 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1563 let precast_ty = cx.tables.expr_ty(cast_exp);
1564 let cast_ty = cx.tables.expr_ty(expr);
1566 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1572 fn detect_absurd_comparison<'a, 'tcx>(
1573 cx: &LateContext<'a, 'tcx>,
1577 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1578 use crate::types::AbsurdComparisonResult::*;
1579 use crate::types::ExtremeType::*;
1580 use crate::utils::comparisons::*;
1582 // absurd comparison only makes sense on primitive types
1583 // primitive types don't implement comparison operators with each other
1584 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1588 // comparisons between fix sized types and target sized types are considered unanalyzable
1589 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1593 let normalized = normalize_comparison(op, lhs, rhs);
1594 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1600 let lx = detect_extreme_expr(cx, normalized_lhs);
1601 let rx = detect_extreme_expr(cx, normalized_rhs);
1606 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1607 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1613 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1614 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1615 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1616 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1620 Rel::Ne | Rel::Eq => return None,
1624 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1625 use crate::types::ExtremeType::*;
1627 let ty = cx.tables.expr_ty(expr);
1629 let cv = constant(cx, cx.tables, expr)?.0;
1631 let which = match (&ty.sty, cv) {
1632 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1633 (&ty::Int(ity), Constant::Int(i))
1634 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1639 (&ty::Bool, Constant::Bool(true)) => Maximum,
1640 (&ty::Int(ity), Constant::Int(i))
1641 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1645 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1649 Some(ExtremeExpr { which, expr })
1652 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1653 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1654 use crate::types::AbsurdComparisonResult::*;
1655 use crate::types::ExtremeType::*;
1657 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1658 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1659 if !in_macro(expr.span) {
1660 let msg = "this comparison involving the minimum or maximum element for this \
1661 type contains a case that is always true or always false";
1663 let conclusion = match result {
1664 AlwaysFalse => "this comparison is always false".to_owned(),
1665 AlwaysTrue => "this comparison is always true".to_owned(),
1666 InequalityImpossible => format!(
1667 "the case where the two sides are not equal never occurs, consider using {} == {} \
1669 snippet(cx, lhs.span, "lhs"),
1670 snippet(cx, rhs.span, "rhs")
1675 "because {} is the {} value for this type, {}",
1676 snippet(cx, culprit.expr.span, "x"),
1677 match culprit.which {
1678 Minimum => "minimum",
1679 Maximum => "maximum",
1684 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1691 /// **What it does:** Checks for comparisons where the relation is always either
1692 /// true or false, but where one side has been upcast so that the comparison is
1693 /// necessary. Only integer types are checked.
1695 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1696 /// will mistakenly imply that it is possible for `x` to be outside the range of
1699 /// **Known problems:**
1700 /// https://github.com/rust-lang/rust-clippy/issues/886
1704 /// let x : u8 = ...; (x as u32) > 300
1706 declare_clippy_lint! {
1707 pub INVALID_UPCAST_COMPARISONS,
1709 "a comparison involving an upcast which is always true or false"
1712 pub struct InvalidUpcastComparisons;
1714 impl LintPass for InvalidUpcastComparisons {
1715 fn get_lints(&self) -> LintArray {
1716 lint_array!(INVALID_UPCAST_COMPARISONS)
1719 fn name(&self) -> &'static str {
1720 "InvalidUpcastComparisons"
1724 #[derive(Copy, Clone, Debug, Eq)]
1731 #[allow(clippy::cast_sign_loss)]
1732 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1735 } else if u > (i128::max_value() as u128) {
1743 impl PartialEq for FullInt {
1744 fn eq(&self, other: &Self) -> bool {
1745 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1749 impl PartialOrd for FullInt {
1750 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1751 Some(match (self, other) {
1752 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1753 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1754 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1755 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1759 impl Ord for FullInt {
1760 fn cmp(&self, other: &Self) -> Ordering {
1761 self.partial_cmp(other)
1762 .expect("partial_cmp for FullInt can never return None")
1766 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1768 use syntax::ast::{IntTy, UintTy};
1770 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1771 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1772 let cast_ty = cx.tables.expr_ty(expr);
1773 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1774 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1777 match pre_cast_ty.sty {
1778 ty::Int(int_ty) => Some(match int_ty {
1780 FullInt::S(i128::from(i8::min_value())),
1781 FullInt::S(i128::from(i8::max_value())),
1784 FullInt::S(i128::from(i16::min_value())),
1785 FullInt::S(i128::from(i16::max_value())),
1788 FullInt::S(i128::from(i32::min_value())),
1789 FullInt::S(i128::from(i32::max_value())),
1792 FullInt::S(i128::from(i64::min_value())),
1793 FullInt::S(i128::from(i64::max_value())),
1795 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1797 FullInt::S(isize::min_value() as i128),
1798 FullInt::S(isize::max_value() as i128),
1801 ty::Uint(uint_ty) => Some(match uint_ty {
1803 FullInt::U(u128::from(u8::min_value())),
1804 FullInt::U(u128::from(u8::max_value())),
1807 FullInt::U(u128::from(u16::min_value())),
1808 FullInt::U(u128::from(u16::max_value())),
1811 FullInt::U(u128::from(u32::min_value())),
1812 FullInt::U(u128::from(u32::max_value())),
1815 FullInt::U(u128::from(u64::min_value())),
1816 FullInt::U(u128::from(u64::max_value())),
1818 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1820 FullInt::U(usize::min_value() as u128),
1821 FullInt::U(usize::max_value() as u128),
1831 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1832 let val = constant(cx, cx.tables, expr)?.0;
1833 if let Constant::Int(const_int) = val {
1834 match cx.tables.expr_ty(expr).sty {
1835 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1836 ty::Uint(_) => Some(FullInt::U(const_int)),
1844 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1845 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1848 INVALID_UPCAST_COMPARISONS,
1851 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1852 snippet(cx, cast_val.span, "the expression"),
1853 if always { "true" } else { "false" },
1859 fn upcast_comparison_bounds_err<'a, 'tcx>(
1860 cx: &LateContext<'a, 'tcx>,
1862 rel: comparisons::Rel,
1863 lhs_bounds: Option<(FullInt, FullInt)>,
1868 use crate::utils::comparisons::*;
1870 if let Some((lb, ub)) = lhs_bounds {
1871 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1872 if rel == Rel::Eq || rel == Rel::Ne {
1873 if norm_rhs_val < lb || norm_rhs_val > ub {
1874 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1876 } else if match rel {
1891 Rel::Eq | Rel::Ne => unreachable!(),
1893 err_upcast_comparison(cx, span, lhs, true)
1894 } else if match rel {
1909 Rel::Eq | Rel::Ne => unreachable!(),
1911 err_upcast_comparison(cx, span, lhs, false)
1917 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1918 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1919 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1920 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1921 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1927 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1928 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1930 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1931 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1936 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1937 /// over different hashers and implicitly defaulting to the default hashing
1938 /// algorithm (SipHash).
1940 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1943 /// **Known problems:** Suggestions for replacing constructors can contain
1944 /// false-positives. Also applying suggestions can require modification of other
1945 /// pieces of code, possibly including external crates.
1949 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1951 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1953 declare_clippy_lint! {
1954 pub IMPLICIT_HASHER,
1956 "missing generalization over different hashers"
1959 pub struct ImplicitHasher;
1961 impl LintPass for ImplicitHasher {
1962 fn get_lints(&self) -> LintArray {
1963 lint_array!(IMPLICIT_HASHER)
1966 fn name(&self) -> &'static str {
1971 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1972 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
1973 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1974 use syntax_pos::BytePos;
1976 fn suggestion<'a, 'tcx>(
1977 cx: &LateContext<'a, 'tcx>,
1978 db: &mut DiagnosticBuilder<'_>,
1979 generics_span: Span,
1980 generics_suggestion_span: Span,
1981 target: &ImplicitHasherType<'_>,
1982 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1984 let generics_snip = snippet(cx, generics_span, "");
1986 let generics_snip = if generics_snip.is_empty() {
1989 &generics_snip[1..generics_snip.len() - 1]
1994 "consider adding a type parameter".to_string(),
1997 generics_suggestion_span,
1999 "<{}{}S: ::std::hash::BuildHasher{}>",
2001 if generics_snip.is_empty() { "" } else { ", " },
2002 if vis.suggestions.is_empty() {
2005 // request users to add `Default` bound so that generic constructors can be used
2012 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2017 if !vis.suggestions.is_empty() {
2018 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2022 if !cx.access_levels.is_exported(item.id) {
2027 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2028 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2031 for target in &vis.found {
2032 if differing_macro_contexts(item.span, target.span()) {
2036 let generics_suggestion_span = generics.span.substitute_dummy({
2037 let pos = snippet_opt(cx, item.span.until(target.span()))
2038 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2039 if let Some(pos) = pos {
2040 Span::new(pos, pos, item.span.data().ctxt)
2046 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2047 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2048 ctr_vis.visit_impl_item(item);
2056 "impl for `{}` should be generalized over different hashers",
2060 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2065 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2066 let body = cx.tcx.hir().body(body_id);
2068 for ty in &decl.inputs {
2069 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2072 for target in &vis.found {
2073 let generics_suggestion_span = generics.span.substitute_dummy({
2074 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2076 let i = snip.find("fn")?;
2077 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2079 .expect("failed to create span for type parameters");
2080 Span::new(pos, pos, item.span.data().ctxt)
2083 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2084 ctr_vis.visit_body(body);
2091 "parameter of type `{}` should be generalized over different hashers",
2095 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2106 enum ImplicitHasherType<'tcx> {
2107 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2108 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2111 impl<'tcx> ImplicitHasherType<'tcx> {
2112 /// Checks that `ty` is a target type without a BuildHasher.
2113 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2114 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2115 let params: Vec<_> = path
2123 .filter_map(|arg| match arg {
2124 GenericArg::Type(ty) => Some(ty),
2125 GenericArg::Lifetime(_) => None,
2128 let params_len = params.len();
2130 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2132 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2133 Some(ImplicitHasherType::HashMap(
2136 snippet(cx, params[0].span, "K"),
2137 snippet(cx, params[1].span, "V"),
2139 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2140 Some(ImplicitHasherType::HashSet(
2143 snippet(cx, params[0].span, "T"),
2153 fn type_name(&self) -> &'static str {
2155 ImplicitHasherType::HashMap(..) => "HashMap",
2156 ImplicitHasherType::HashSet(..) => "HashSet",
2160 fn type_arguments(&self) -> String {
2162 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2163 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2167 fn ty(&self) -> Ty<'tcx> {
2169 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2173 fn span(&self) -> Span {
2175 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2180 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2181 cx: &'a LateContext<'a, 'tcx>,
2182 found: Vec<ImplicitHasherType<'tcx>>,
2185 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2186 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2187 Self { cx, found: vec![] }
2191 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2192 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2193 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2194 self.found.push(target);
2200 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2201 NestedVisitorMap::None
2205 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2206 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2207 cx: &'a LateContext<'a, 'tcx>,
2208 body: &'a TypeckTables<'tcx>,
2209 target: &'b ImplicitHasherType<'tcx>,
2210 suggestions: BTreeMap<Span, String>,
2213 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2214 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2219 suggestions: BTreeMap::new(),
2224 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2225 fn visit_body(&mut self, body: &'tcx Body) {
2226 self.body = self.cx.tcx.body_tables(body.id());
2227 walk_body(self, body);
2230 fn visit_expr(&mut self, e: &'tcx Expr) {
2232 if let ExprKind::Call(ref fun, ref args) = e.node;
2233 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2234 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2236 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2240 if match_path(ty_path, &paths::HASHMAP) {
2241 if method.ident.name == "new" {
2243 .insert(e.span, "HashMap::default()".to_string());
2244 } else if method.ident.name == "with_capacity" {
2245 self.suggestions.insert(
2248 "HashMap::with_capacity_and_hasher({}, Default::default())",
2249 snippet(self.cx, args[0].span, "capacity"),
2253 } else if match_path(ty_path, &paths::HASHSET) {
2254 if method.ident.name == "new" {
2256 .insert(e.span, "HashSet::default()".to_string());
2257 } else if method.ident.name == "with_capacity" {
2258 self.suggestions.insert(
2261 "HashSet::with_capacity_and_hasher({}, Default::default())",
2262 snippet(self.cx, args[0].span, "capacity"),
2273 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2274 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2278 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2280 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2281 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2284 /// **Known problems:** None.
2290 /// *(r as *const _ as *mut _) += 1;
2295 /// Instead consider using interior mutability types.
2298 /// fn x(r: &UnsafeCell<i32>) {
2304 declare_clippy_lint! {
2305 pub CAST_REF_TO_MUT,
2307 "a cast of reference to a mutable pointer"
2310 pub struct RefToMut;
2312 impl LintPass for RefToMut {
2313 fn get_lints(&self) -> LintArray {
2314 lint_array!(CAST_REF_TO_MUT)
2317 fn name(&self) -> &'static str {
2322 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2323 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2325 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2326 if let ExprKind::Cast(e, t) = &e.node;
2327 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2328 if let ExprKind::Cast(e, t) = &e.node;
2329 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2330 if let ty::Ref(..) = cx.tables.node_id_to_type(e.hir_id).sty;
2336 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",