1 #![allow(clippy::default_hash_types)]
3 use crate::consts::{constant, Constant};
4 use crate::utils::paths;
6 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
7 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
8 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
11 use if_chain::if_chain;
13 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
15 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
16 use rustc::ty::layout::LayoutOf;
17 use rustc::ty::{self, Ty, TyCtxt, TypeckTables};
18 use rustc::{declare_tool_lint, lint_array};
19 use rustc_errors::Applicability;
20 use rustc_target::spec::abi::Abi;
21 use rustc_typeck::hir_ty_to_ty;
23 use std::cmp::Ordering;
24 use std::collections::BTreeMap;
25 use syntax::ast::{FloatTy, IntTy, UintTy};
26 use syntax::errors::DiagnosticBuilder;
27 use syntax::source_map::Span;
29 /// Handles all the linting of funky types
32 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
34 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
35 /// the heap. So if you `Box` it, you just add another level of indirection
36 /// without any benefit whatsoever.
38 /// **Known problems:** None.
43 /// values: Box<Vec<Foo>>,
54 declare_clippy_lint! {
57 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
60 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
62 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
63 /// the heap. So if you `Box` its contents, you just add another level of indirection.
65 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
71 /// values: Vec<Box<i32>>,
82 declare_clippy_lint! {
85 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
88 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
91 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
92 /// represents an optional optional value which is logically the same thing as an optional
93 /// value but has an unneeded extra level of wrapping.
95 /// **Known problems:** None.
99 /// fn x() -> Option<Option<u32>> {
102 declare_clippy_lint! {
105 "usage of `Option<Option<T>>`"
108 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
109 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
111 /// **Why is this bad?** Gankro says:
113 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
114 /// pointers and indirection.
115 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
117 /// > "only" amortized for push/pop, should be faster in the general case for
118 /// almost every possible
119 /// > workload, and isn't even amortized at all if you can predict the capacity
122 /// > `LinkedList`s are only really good if you're doing a lot of merging or
123 /// splitting of lists.
124 /// > This is because they can just mangle some pointers instead of actually
125 /// copying the data. Even
126 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
127 /// can still be better
128 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
130 /// **Known problems:** False positives – the instances where using a
131 /// `LinkedList` makes sense are few and far between, but they can still happen.
135 /// let x = LinkedList::new();
137 declare_clippy_lint! {
140 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
143 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
145 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
148 /// **Known problems:** None.
152 /// fn foo(bar: &Box<T>) { ... }
158 /// fn foo(bar: &T) { ... }
160 declare_clippy_lint! {
163 "a borrow of a boxed type"
166 impl LintPass for TypePass {
167 fn get_lints(&self) -> LintArray {
168 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
171 fn name(&self) -> &'static str {
176 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
179 cx: &LateContext<'_, '_>,
186 // skip trait implementations, see #605
187 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find_by_hir_id(
188 cx.tcx.hir().get_parent_item(id))
190 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
195 check_fn_decl(cx, decl);
198 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
199 check_ty(cx, &field.ty, false);
202 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
204 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
205 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
210 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
211 if let Some(ref ty) = local.ty {
212 check_ty(cx, ty, true);
217 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
218 for input in &decl.inputs {
219 check_ty(cx, input, false);
222 if let FunctionRetTy::Return(ref ty) = decl.output {
223 check_ty(cx, ty, false);
227 /// Check if `qpath` has last segment with type parameter matching `path`
228 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
229 let last = last_path_segment(qpath);
231 if let Some(ref params) = last.args;
232 if !params.parenthesized;
233 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
234 GenericArg::Type(ty) => Some(ty),
237 if let TyKind::Path(ref qpath) = ty.node;
238 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
239 if match_def_path(cx.tcx, did, path);
247 /// Recursively check for `TypePass` lints in the given type. Stop at the first
250 /// The parameter `is_local` distinguishes the context of the type; types from
251 /// local bindings should only be checked for the `BORROWED_BOX` lint.
252 #[allow(clippy::too_many_lines)]
253 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
254 if in_macro(hir_ty.span) {
258 TyKind::Path(ref qpath) if !is_local => {
259 let hir_id = cx.tcx.hir().node_to_hir_id(hir_ty.id);
260 let def = cx.tables.qpath_def(qpath, hir_id);
261 if let Some(def_id) = opt_def_id(def) {
262 if Some(def_id) == cx.tcx.lang_items().owned_box() {
263 if match_type_parameter(cx, qpath, &paths::VEC) {
268 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
269 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
271 return; // don't recurse into the type
273 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
275 // Get the _ part of Vec<_>
276 if let Some(ref last) = last_path_segment(qpath).args;
277 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
278 GenericArg::Type(ty) => Some(ty),
281 // ty is now _ at this point
282 if let TyKind::Path(ref ty_qpath) = ty.node;
283 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
284 if let Some(def_id) = opt_def_id(def);
285 if Some(def_id) == cx.tcx.lang_items().owned_box();
286 // At this point, we know ty is Box<T>, now get T
287 if let Some(ref last) = last_path_segment(ty_qpath).args;
288 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
289 GenericArg::Type(ty) => Some(ty),
293 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
294 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
299 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
301 format!("Vec<{}>", ty_ty),
302 Applicability::MachineApplicable,
304 return; // don't recurse into the type
308 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
309 if match_type_parameter(cx, qpath, &paths::OPTION) {
314 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
315 enum if you need to distinguish all 3 cases",
317 return; // don't recurse into the type
319 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
324 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
325 "a VecDeque might work",
327 return; // don't recurse into the type
331 QPath::Resolved(Some(ref ty), ref p) => {
332 check_ty(cx, ty, is_local);
333 for ty in p.segments.iter().flat_map(|seg| {
336 .map_or_else(|| [].iter(), |params| params.args.iter())
337 .filter_map(|arg| match arg {
338 GenericArg::Type(ty) => Some(ty),
342 check_ty(cx, ty, is_local);
345 QPath::Resolved(None, ref p) => {
346 for ty in p.segments.iter().flat_map(|seg| {
349 .map_or_else(|| [].iter(), |params| params.args.iter())
350 .filter_map(|arg| match arg {
351 GenericArg::Type(ty) => Some(ty),
355 check_ty(cx, ty, is_local);
358 QPath::TypeRelative(ref ty, ref seg) => {
359 check_ty(cx, ty, is_local);
360 if let Some(ref params) = seg.args {
361 for ty in params.args.iter().filter_map(|arg| match arg {
362 GenericArg::Type(ty) => Some(ty),
365 check_ty(cx, ty, is_local);
371 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
373 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
374 check_ty(cx, ty, is_local)
376 TyKind::Tup(ref tys) => {
378 check_ty(cx, ty, is_local);
385 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
386 match mut_ty.ty.node {
387 TyKind::Path(ref qpath) => {
388 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
389 let def = cx.tables.qpath_def(qpath, hir_id);
391 if let Some(def_id) = opt_def_id(def);
392 if Some(def_id) == cx.tcx.lang_items().owned_box();
393 if let QPath::Resolved(None, ref path) = *qpath;
394 if let [ref bx] = *path.segments;
395 if let Some(ref params) = bx.args;
396 if !params.parenthesized;
397 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
398 GenericArg::Type(ty) => Some(ty),
402 if is_any_trait(inner) {
403 // Ignore `Box<Any>` types, see #1884 for details.
407 let ltopt = if lt.is_elided() {
410 format!("{} ", lt.name.ident().as_str())
412 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
417 let mut applicability = Applicability::MachineApplicable;
422 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
428 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
430 Applicability::Unspecified,
432 return; // don't recurse into the type
435 check_ty(cx, &mut_ty.ty, is_local);
437 _ => check_ty(cx, &mut_ty.ty, is_local),
441 // Returns true if given type is `Any` trait.
442 fn is_any_trait(t: &hir::Ty) -> bool {
444 if let TyKind::TraitObject(ref traits, _) = t.node;
445 if traits.len() >= 1;
446 // Only Send/Sync can be used as additional traits, so it is enough to
447 // check only the first trait.
448 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
459 /// **What it does:** Checks for binding a unit value.
461 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
462 /// binding one is kind of pointless.
464 /// **Known problems:** None.
472 declare_clippy_lint! {
475 "creating a let binding to a value of unit type, which usually can't be used afterwards"
478 impl LintPass for LetPass {
479 fn get_lints(&self) -> LintArray {
480 lint_array!(LET_UNIT_VALUE)
483 fn name(&self) -> &'static str {
488 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
489 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
490 if let StmtKind::Local(ref local) = stmt.node {
491 if is_unit(cx.tables.pat_ty(&local.pat)) {
492 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
495 if higher::is_from_for_desugar(local) {
503 "this let-binding has unit value. Consider omitting `let {} =`",
504 snippet(cx, local.pat.span, "..")
512 /// **What it does:** Checks for comparisons to unit.
514 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
515 /// clumsily written constant. Mostly this happens when someone accidentally
516 /// adds semicolons at the end of the operands.
518 /// **Known problems:** None.
538 declare_clippy_lint! {
541 "comparing unit values"
546 impl LintPass for UnitCmp {
547 fn get_lints(&self) -> LintArray {
548 lint_array!(UNIT_CMP)
551 fn name(&self) -> &'static str {
556 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
557 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
558 if in_macro(expr.span) {
561 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
563 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
564 let result = match op {
565 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
573 "{}-comparison of unit values detected. This will always be {}",
583 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
584 /// unit literal (`()`).
586 /// **Why is this bad?** This is likely the result of an accidental semicolon.
588 /// **Known problems:** None.
597 declare_clippy_lint! {
600 "passing unit to a function"
605 impl LintPass for UnitArg {
606 fn get_lints(&self) -> LintArray {
607 lint_array!(UNIT_ARG)
610 fn name(&self) -> &'static str {
615 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
616 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
617 if in_macro(expr.span) {
621 // apparently stuff in the desugaring of `?` can trigger this
622 // so check for that here
623 // only the calls to `Try::from_error` is marked as desugared,
624 // so we need to check both the current Expr and its parent.
625 if is_questionmark_desugar_marked_call(expr) {
629 let map = &cx.tcx.hir();
630 let opt_parent_node = map.find(map.get_parent_node(expr.id));
631 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
632 if is_questionmark_desugar_marked_call(parent_expr);
639 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
641 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
642 if let ExprKind::Match(.., match_source) = &arg.node {
643 if *match_source == MatchSource::TryDesugar {
652 "passing a unit value to a function",
653 "if you intended to pass a unit value, use a unit literal instead",
655 Applicability::MachineApplicable,
665 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
666 use syntax_pos::hygiene::CompilerDesugaringKind;
667 if let ExprKind::Call(ref callee, _) = expr.node {
668 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
674 fn is_unit(ty: Ty<'_>) -> bool {
676 ty::Tuple(slice) if slice.is_empty() => true,
681 fn is_unit_literal(expr: &Expr) -> bool {
683 ExprKind::Tup(ref slice) if slice.is_empty() => true,
690 /// **What it does:** Checks for casts from any numerical to a float type where
691 /// the receiving type cannot store all values from the original type without
692 /// rounding errors. This possible rounding is to be expected, so this lint is
693 /// `Allow` by default.
695 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
696 /// or any 64-bit integer to `f64`.
698 /// **Why is this bad?** It's not bad at all. But in some applications it can be
699 /// helpful to know where precision loss can take place. This lint can help find
700 /// those places in the code.
702 /// **Known problems:** None.
706 /// let x = u64::MAX;
709 declare_clippy_lint! {
710 pub CAST_PRECISION_LOSS,
712 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
715 /// **What it does:** Checks for casts from a signed to an unsigned numerical
716 /// type. In this case, negative values wrap around to large positive values,
717 /// which can be quite surprising in practice. However, as the cast works as
718 /// defined, this lint is `Allow` by default.
720 /// **Why is this bad?** Possibly surprising results. You can activate this lint
721 /// as a one-time check to see where numerical wrapping can arise.
723 /// **Known problems:** None.
728 /// y as u128 // will return 18446744073709551615
730 declare_clippy_lint! {
733 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
736 /// **What it does:** Checks for on casts between numerical types that may
737 /// truncate large values. This is expected behavior, so the cast is `Allow` by
740 /// **Why is this bad?** In some problem domains, it is good practice to avoid
741 /// truncation. This lint can be activated to help assess where additional
742 /// checks could be beneficial.
744 /// **Known problems:** None.
748 /// fn as_u8(x: u64) -> u8 {
752 declare_clippy_lint! {
753 pub CAST_POSSIBLE_TRUNCATION,
755 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
758 /// **What it does:** Checks for casts from an unsigned type to a signed type of
759 /// the same size. Performing such a cast is a 'no-op' for the compiler,
760 /// i.e. nothing is changed at the bit level, and the binary representation of
761 /// the value is reinterpreted. This can cause wrapping if the value is too big
762 /// for the target signed type. However, the cast works as defined, so this lint
763 /// is `Allow` by default.
765 /// **Why is this bad?** While such a cast is not bad in itself, the results can
766 /// be surprising when this is not the intended behavior, as demonstrated by the
769 /// **Known problems:** None.
773 /// u32::MAX as i32 // will yield a value of `-1`
775 declare_clippy_lint! {
776 pub CAST_POSSIBLE_WRAP,
778 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
781 /// **What it does:** Checks for on casts between numerical types that may
782 /// be replaced by safe conversion functions.
784 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
785 /// conversions, including silently lossy conversions. Conversion functions such
786 /// as `i32::from` will only perform lossless conversions. Using the conversion
787 /// functions prevents conversions from turning into silent lossy conversions if
788 /// the types of the input expressions ever change, and make it easier for
789 /// people reading the code to know that the conversion is lossless.
791 /// **Known problems:** None.
795 /// fn as_u64(x: u8) -> u64 {
800 /// Using `::from` would look like this:
803 /// fn as_u64(x: u8) -> u64 {
807 declare_clippy_lint! {
810 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
813 /// **What it does:** Checks for casts to the same type.
815 /// **Why is this bad?** It's just unnecessary.
817 /// **Known problems:** None.
821 /// let _ = 2i32 as i32
823 declare_clippy_lint! {
824 pub UNNECESSARY_CAST,
826 "cast to the same type, e.g. `x as i32` where `x: i32`"
829 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
830 /// more-strictly-aligned pointer
832 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
835 /// **Known problems:** None.
839 /// let _ = (&1u8 as *const u8) as *const u16;
840 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
842 declare_clippy_lint! {
843 pub CAST_PTR_ALIGNMENT,
845 "cast from a pointer to a more-strictly-aligned pointer"
848 /// **What it does:** Checks for casts of function pointers to something other than usize
850 /// **Why is this bad?**
851 /// Casting a function pointer to anything other than usize/isize is not portable across
852 /// architectures, because you end up losing bits if the target type is too small or end up with a
853 /// bunch of extra bits that waste space and add more instructions to the final binary than
854 /// strictly necessary for the problem
856 /// Casting to isize also doesn't make sense since there are no signed addresses.
862 /// fn fun() -> i32 {}
863 /// let a = fun as i64;
866 /// fn fun2() -> i32 {}
867 /// let a = fun2 as usize;
869 declare_clippy_lint! {
870 pub FN_TO_NUMERIC_CAST,
872 "casting a function pointer to a numeric type other than usize"
875 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
878 /// **Why is this bad?**
879 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
880 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
881 /// a comment) to perform the truncation.
887 /// fn fn1() -> i16 {
890 /// let _ = fn1 as i32;
892 /// // Better: Cast to usize first, then comment with the reason for the truncation
893 /// fn fn2() -> i16 {
896 /// let fn_ptr = fn2 as usize;
897 /// let fn_ptr_truncated = fn_ptr as i32;
899 declare_clippy_lint! {
900 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
902 "casting a function pointer to a numeric type not wide enough to store the address"
905 /// Returns the size in bits of an integral type.
906 /// Will return 0 if the type is not an int or uint variant
907 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
909 ty::Int(i) => match i {
910 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
917 ty::Uint(i) => match i {
918 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
929 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
931 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
936 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
937 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
938 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
939 let arch_dependent_str = "on targets with 64-bit wide pointers ";
940 let from_nbits_str = if arch_dependent {
942 } else if is_isize_or_usize(cast_from) {
943 "32 or 64".to_owned()
945 int_ty_to_nbits(cast_from, cx.tcx).to_string()
952 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
953 is only {4} bits wide)",
955 if cast_to_f64 { "f64" } else { "f32" },
956 if arch_dependent { arch_dependent_str } else { "" },
963 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
964 if let ExprKind::Binary(_, _, _) = op.node {
965 if snip.starts_with('(') && snip.ends_with(')') {
972 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
973 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
974 if in_constant(cx, expr.id) {
977 // The suggestion is to use a function call, so if the original expression
978 // has parens on the outside, they are no longer needed.
979 let mut applicability = Applicability::MachineApplicable;
980 let opt = snippet_opt(cx, op.span);
981 let sugg = if let Some(ref snip) = opt {
982 if should_strip_parens(op, snip) {
983 &snip[1..snip.len() - 1]
988 applicability = Applicability::HasPlaceholders;
997 "casting {} to {} may become silently lossy if types change",
1001 format!("{}::from({})", cast_to, sugg),
1012 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1013 if !cast_from.is_signed() || cast_to.is_signed() {
1017 // don't lint for positive constants
1018 let const_val = constant(cx, &cx.tables, op);
1020 if let Some((const_val, _)) = const_val;
1021 if let Constant::Int(n) = const_val;
1022 if let ty::Int(ity) = cast_from.sty;
1023 if sext(cx.tcx, n, ity) >= 0;
1033 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1037 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1038 let arch_64_suffix = " on targets with 64-bit wide pointers";
1039 let arch_32_suffix = " on targets with 32-bit wide pointers";
1040 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1041 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1042 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1043 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1044 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1045 (true, true) | (false, false) => (
1046 to_nbits < from_nbits,
1048 to_nbits == from_nbits && cast_unsigned_to_signed,
1058 to_nbits <= 32 && cast_unsigned_to_signed,
1064 cast_unsigned_to_signed,
1065 if from_nbits == 64 {
1072 if span_truncation {
1075 CAST_POSSIBLE_TRUNCATION,
1078 "casting {} to {} may truncate the value{}",
1081 match suffix_truncation {
1082 ArchSuffix::_32 => arch_32_suffix,
1083 ArchSuffix::_64 => arch_64_suffix,
1084 ArchSuffix::None => "",
1095 "casting {} to {} may wrap around the value{}",
1099 ArchSuffix::_32 => arch_32_suffix,
1100 ArchSuffix::_64 => arch_64_suffix,
1101 ArchSuffix::None => "",
1108 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1109 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1110 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1111 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1112 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1114 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1118 impl LintPass for CastPass {
1119 fn get_lints(&self) -> LintArray {
1121 CAST_PRECISION_LOSS,
1123 CAST_POSSIBLE_TRUNCATION,
1129 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1133 fn name(&self) -> &'static str {
1138 // Check if the given type is either `core::ffi::c_void` or
1139 // one of the platform specific `libc::<platform>::c_void` of libc.
1140 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1141 if let ty::Adt(adt, _) = ty.sty {
1142 let mut apb = AbsolutePathBuffer { names: vec![] };
1143 tcx.push_item_path(&mut apb, adt.did, false);
1145 if apb.names.is_empty() {
1148 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1155 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1156 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1157 if let ExprKind::Cast(ref ex, _) = expr.node {
1158 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1159 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1160 if let ExprKind::Lit(ref lit) = ex.node {
1161 use syntax::ast::{LitIntType, LitKind};
1163 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1165 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1171 "casting to the same type is unnecessary (`{}` -> `{}`)",
1179 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1180 match (cast_from.is_integral(), cast_to.is_integral()) {
1182 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1183 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1188 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1189 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1191 if from_nbits < to_nbits {
1192 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1198 CAST_POSSIBLE_TRUNCATION,
1200 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1202 if !cast_to.is_signed() {
1207 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1212 check_loss_of_sign(cx, expr, ex, cast_from, cast_to);
1213 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1214 check_lossless(cx, expr, ex, cast_from, cast_to);
1217 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1220 CAST_POSSIBLE_TRUNCATION,
1222 "casting f64 to f32 may truncate the value",
1225 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1226 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1233 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1234 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1235 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1236 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1237 if from_align < to_align;
1238 // with c_void, we inherently need to trust the user
1239 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1245 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1253 fn lint_fn_to_numeric_cast(
1254 cx: &LateContext<'_, '_>,
1260 // We only want to check casts to `ty::Uint` or `ty::Int`
1262 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1265 match cast_from.sty {
1266 ty::FnDef(..) | ty::FnPtr(_) => {
1267 let mut applicability = Applicability::MachineApplicable;
1268 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1270 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1271 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1274 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1277 "casting function pointer `{}` to `{}`, which truncates the value",
1278 from_snippet, cast_to
1281 format!("{} as usize", from_snippet),
1284 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1289 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1291 format!("{} as usize", from_snippet),
1300 /// **What it does:** Checks for types used in structs, parameters and `let`
1301 /// declarations above a certain complexity threshold.
1303 /// **Why is this bad?** Too complex types make the code less readable. Consider
1304 /// using a `type` definition to simplify them.
1306 /// **Known problems:** None.
1311 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1314 declare_clippy_lint! {
1315 pub TYPE_COMPLEXITY,
1317 "usage of very complex types that might be better factored into `type` definitions"
1320 pub struct TypeComplexityPass {
1324 impl TypeComplexityPass {
1325 pub fn new(threshold: u64) -> Self {
1330 impl LintPass for TypeComplexityPass {
1331 fn get_lints(&self) -> LintArray {
1332 lint_array!(TYPE_COMPLEXITY)
1335 fn name(&self) -> &'static str {
1336 "TypeComplexityPass"
1340 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1343 cx: &LateContext<'a, 'tcx>,
1350 self.check_fndecl(cx, decl);
1353 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1354 // enum variants are also struct fields now
1355 self.check_type(cx, &field.ty);
1358 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1360 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1361 // functions, enums, structs, impls and traits are covered
1366 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1368 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1369 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1370 // methods with default impl are covered by check_fn
1375 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1377 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1378 // methods are covered by check_fn
1383 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1384 if let Some(ref ty) = local.ty {
1385 self.check_type(cx, ty);
1390 impl<'a, 'tcx> TypeComplexityPass {
1391 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1392 for arg in &decl.inputs {
1393 self.check_type(cx, arg);
1395 if let Return(ref ty) = decl.output {
1396 self.check_type(cx, ty);
1400 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1401 if in_macro(ty.span) {
1405 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1406 visitor.visit_ty(ty);
1410 if score > self.threshold {
1415 "very complex type used. Consider factoring parts into `type` definitions",
1421 /// Walks a type and assigns a complexity score to it.
1422 struct TypeComplexityVisitor {
1423 /// total complexity score of the type
1425 /// current nesting level
1429 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1430 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1431 let (add_score, sub_nest) = match ty.node {
1432 // _, &x and *x have only small overhead; don't mess with nesting level
1433 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1435 // the "normal" components of a type: named types, arrays/tuples
1436 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1438 // function types bring a lot of overhead
1439 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1441 TyKind::TraitObject(ref param_bounds, _) => {
1442 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1443 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1444 GenericParamKind::Lifetime { .. } => true,
1448 if has_lifetime_parameters {
1449 // complex trait bounds like A<'a, 'b>
1452 // simple trait bounds like A + B
1459 self.score += add_score;
1460 self.nest += sub_nest;
1462 self.nest -= sub_nest;
1464 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1465 NestedVisitorMap::None
1469 /// **What it does:** Checks for expressions where a character literal is cast
1470 /// to `u8` and suggests using a byte literal instead.
1472 /// **Why is this bad?** In general, casting values to smaller types is
1473 /// error-prone and should be avoided where possible. In the particular case of
1474 /// converting a character literal to u8, it is easy to avoid by just using a
1475 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1476 /// than `'a' as u8`.
1478 /// **Known problems:** None.
1485 /// A better version, using the byte literal:
1490 declare_clippy_lint! {
1493 "casting a character literal to u8"
1496 pub struct CharLitAsU8;
1498 impl LintPass for CharLitAsU8 {
1499 fn get_lints(&self) -> LintArray {
1500 lint_array!(CHAR_LIT_AS_U8)
1503 fn name(&self) -> &'static str {
1508 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1509 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1510 use syntax::ast::{LitKind, UintTy};
1512 if let ExprKind::Cast(ref e, _) = expr.node {
1513 if let ExprKind::Lit(ref l) = e.node {
1514 if let LitKind::Char(_) = l.node {
1515 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1516 let msg = "casting character literal to u8. `char`s \
1517 are 4 bytes wide in rust, so casting to u8 \
1520 "Consider using a byte literal instead:\nb{}",
1521 snippet(cx, e.span, "'x'")
1523 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1531 /// **What it does:** Checks for comparisons where one side of the relation is
1532 /// either the minimum or maximum value for its type and warns if it involves a
1533 /// case that is always true or always false. Only integer and boolean types are
1536 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1537 /// that is is possible for `x` to be less than the minimum. Expressions like
1538 /// `max < x` are probably mistakes.
1540 /// **Known problems:** For `usize` the size of the current compile target will
1541 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1542 /// a comparison to detect target pointer width will trigger this lint. One can
1543 /// use `mem::sizeof` and compare its value or conditional compilation
1545 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1550 /// 100 > std::i32::MAX
1552 declare_clippy_lint! {
1553 pub ABSURD_EXTREME_COMPARISONS,
1555 "a comparison with a maximum or minimum value that is always true or false"
1558 pub struct AbsurdExtremeComparisons;
1560 impl LintPass for AbsurdExtremeComparisons {
1561 fn get_lints(&self) -> LintArray {
1562 lint_array!(ABSURD_EXTREME_COMPARISONS)
1565 fn name(&self) -> &'static str {
1566 "AbsurdExtremeComparisons"
1575 struct ExtremeExpr<'a> {
1580 enum AbsurdComparisonResult {
1583 InequalityImpossible,
1586 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1587 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1588 let precast_ty = cx.tables.expr_ty(cast_exp);
1589 let cast_ty = cx.tables.expr_ty(expr);
1591 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1597 fn detect_absurd_comparison<'a, 'tcx>(
1598 cx: &LateContext<'a, 'tcx>,
1602 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1603 use crate::types::AbsurdComparisonResult::*;
1604 use crate::types::ExtremeType::*;
1605 use crate::utils::comparisons::*;
1607 // absurd comparison only makes sense on primitive types
1608 // primitive types don't implement comparison operators with each other
1609 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1613 // comparisons between fix sized types and target sized types are considered unanalyzable
1614 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1618 let normalized = normalize_comparison(op, lhs, rhs);
1619 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1625 let lx = detect_extreme_expr(cx, normalized_lhs);
1626 let rx = detect_extreme_expr(cx, normalized_rhs);
1631 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1632 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1638 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1639 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1640 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1641 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1645 Rel::Ne | Rel::Eq => return None,
1649 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1650 use crate::types::ExtremeType::*;
1652 let ty = cx.tables.expr_ty(expr);
1654 let cv = constant(cx, cx.tables, expr)?.0;
1656 let which = match (&ty.sty, cv) {
1657 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1658 (&ty::Int(ity), Constant::Int(i))
1659 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1664 (&ty::Bool, Constant::Bool(true)) => Maximum,
1665 (&ty::Int(ity), Constant::Int(i))
1666 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1670 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1674 Some(ExtremeExpr { which, expr })
1677 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1678 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1679 use crate::types::AbsurdComparisonResult::*;
1680 use crate::types::ExtremeType::*;
1682 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1683 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1684 if !in_macro(expr.span) {
1685 let msg = "this comparison involving the minimum or maximum element for this \
1686 type contains a case that is always true or always false";
1688 let conclusion = match result {
1689 AlwaysFalse => "this comparison is always false".to_owned(),
1690 AlwaysTrue => "this comparison is always true".to_owned(),
1691 InequalityImpossible => format!(
1692 "the case where the two sides are not equal never occurs, consider using {} == {} \
1694 snippet(cx, lhs.span, "lhs"),
1695 snippet(cx, rhs.span, "rhs")
1700 "because {} is the {} value for this type, {}",
1701 snippet(cx, culprit.expr.span, "x"),
1702 match culprit.which {
1703 Minimum => "minimum",
1704 Maximum => "maximum",
1709 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1716 /// **What it does:** Checks for comparisons where the relation is always either
1717 /// true or false, but where one side has been upcast so that the comparison is
1718 /// necessary. Only integer types are checked.
1720 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1721 /// will mistakenly imply that it is possible for `x` to be outside the range of
1724 /// **Known problems:**
1725 /// https://github.com/rust-lang/rust-clippy/issues/886
1729 /// let x : u8 = ...; (x as u32) > 300
1731 declare_clippy_lint! {
1732 pub INVALID_UPCAST_COMPARISONS,
1734 "a comparison involving an upcast which is always true or false"
1737 pub struct InvalidUpcastComparisons;
1739 impl LintPass for InvalidUpcastComparisons {
1740 fn get_lints(&self) -> LintArray {
1741 lint_array!(INVALID_UPCAST_COMPARISONS)
1744 fn name(&self) -> &'static str {
1745 "InvalidUpcastComparisons"
1749 #[derive(Copy, Clone, Debug, Eq)]
1756 #[allow(clippy::cast_sign_loss)]
1757 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1760 } else if u > (i128::max_value() as u128) {
1768 impl PartialEq for FullInt {
1769 fn eq(&self, other: &Self) -> bool {
1770 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1774 impl PartialOrd for FullInt {
1775 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1776 Some(match (self, other) {
1777 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1778 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1779 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1780 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1784 impl Ord for FullInt {
1785 fn cmp(&self, other: &Self) -> Ordering {
1786 self.partial_cmp(other)
1787 .expect("partial_cmp for FullInt can never return None")
1791 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1793 use syntax::ast::{IntTy, UintTy};
1795 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1796 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1797 let cast_ty = cx.tables.expr_ty(expr);
1798 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1799 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1802 match pre_cast_ty.sty {
1803 ty::Int(int_ty) => Some(match int_ty {
1805 FullInt::S(i128::from(i8::min_value())),
1806 FullInt::S(i128::from(i8::max_value())),
1809 FullInt::S(i128::from(i16::min_value())),
1810 FullInt::S(i128::from(i16::max_value())),
1813 FullInt::S(i128::from(i32::min_value())),
1814 FullInt::S(i128::from(i32::max_value())),
1817 FullInt::S(i128::from(i64::min_value())),
1818 FullInt::S(i128::from(i64::max_value())),
1820 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1822 FullInt::S(isize::min_value() as i128),
1823 FullInt::S(isize::max_value() as i128),
1826 ty::Uint(uint_ty) => Some(match uint_ty {
1828 FullInt::U(u128::from(u8::min_value())),
1829 FullInt::U(u128::from(u8::max_value())),
1832 FullInt::U(u128::from(u16::min_value())),
1833 FullInt::U(u128::from(u16::max_value())),
1836 FullInt::U(u128::from(u32::min_value())),
1837 FullInt::U(u128::from(u32::max_value())),
1840 FullInt::U(u128::from(u64::min_value())),
1841 FullInt::U(u128::from(u64::max_value())),
1843 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1845 FullInt::U(usize::min_value() as u128),
1846 FullInt::U(usize::max_value() as u128),
1856 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1857 let val = constant(cx, cx.tables, expr)?.0;
1858 if let Constant::Int(const_int) = val {
1859 match cx.tables.expr_ty(expr).sty {
1860 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1861 ty::Uint(_) => Some(FullInt::U(const_int)),
1869 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1870 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1873 INVALID_UPCAST_COMPARISONS,
1876 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1877 snippet(cx, cast_val.span, "the expression"),
1878 if always { "true" } else { "false" },
1884 fn upcast_comparison_bounds_err<'a, 'tcx>(
1885 cx: &LateContext<'a, 'tcx>,
1887 rel: comparisons::Rel,
1888 lhs_bounds: Option<(FullInt, FullInt)>,
1893 use crate::utils::comparisons::*;
1895 if let Some((lb, ub)) = lhs_bounds {
1896 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1897 if rel == Rel::Eq || rel == Rel::Ne {
1898 if norm_rhs_val < lb || norm_rhs_val > ub {
1899 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1901 } else if match rel {
1916 Rel::Eq | Rel::Ne => unreachable!(),
1918 err_upcast_comparison(cx, span, lhs, true)
1919 } else if match rel {
1934 Rel::Eq | Rel::Ne => unreachable!(),
1936 err_upcast_comparison(cx, span, lhs, false)
1942 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1943 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1944 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1945 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1946 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1952 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1953 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1955 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1956 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1961 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1962 /// over different hashers and implicitly defaulting to the default hashing
1963 /// algorithm (SipHash).
1965 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1968 /// **Known problems:** Suggestions for replacing constructors can contain
1969 /// false-positives. Also applying suggestions can require modification of other
1970 /// pieces of code, possibly including external crates.
1974 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1976 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1978 declare_clippy_lint! {
1979 pub IMPLICIT_HASHER,
1981 "missing generalization over different hashers"
1984 pub struct ImplicitHasher;
1986 impl LintPass for ImplicitHasher {
1987 fn get_lints(&self) -> LintArray {
1988 lint_array!(IMPLICIT_HASHER)
1991 fn name(&self) -> &'static str {
1996 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1997 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
1998 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1999 use syntax_pos::BytePos;
2001 fn suggestion<'a, 'tcx>(
2002 cx: &LateContext<'a, 'tcx>,
2003 db: &mut DiagnosticBuilder<'_>,
2004 generics_span: Span,
2005 generics_suggestion_span: Span,
2006 target: &ImplicitHasherType<'_>,
2007 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2009 let generics_snip = snippet(cx, generics_span, "");
2011 let generics_snip = if generics_snip.is_empty() {
2014 &generics_snip[1..generics_snip.len() - 1]
2019 "consider adding a type parameter".to_string(),
2022 generics_suggestion_span,
2024 "<{}{}S: ::std::hash::BuildHasher{}>",
2026 if generics_snip.is_empty() { "" } else { ", " },
2027 if vis.suggestions.is_empty() {
2030 // request users to add `Default` bound so that generic constructors can be used
2037 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2042 if !vis.suggestions.is_empty() {
2043 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2047 if !cx.access_levels.is_exported(item.id) {
2052 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2053 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2056 for target in &vis.found {
2057 if differing_macro_contexts(item.span, target.span()) {
2061 let generics_suggestion_span = generics.span.substitute_dummy({
2062 let pos = snippet_opt(cx, item.span.until(target.span()))
2063 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2064 if let Some(pos) = pos {
2065 Span::new(pos, pos, item.span.data().ctxt)
2071 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2072 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2073 ctr_vis.visit_impl_item(item);
2081 "impl for `{}` should be generalized over different hashers",
2085 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2090 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2091 let body = cx.tcx.hir().body(body_id);
2093 for ty in &decl.inputs {
2094 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2097 for target in &vis.found {
2098 let generics_suggestion_span = generics.span.substitute_dummy({
2099 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2101 let i = snip.find("fn")?;
2102 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2104 .expect("failed to create span for type parameters");
2105 Span::new(pos, pos, item.span.data().ctxt)
2108 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2109 ctr_vis.visit_body(body);
2116 "parameter of type `{}` should be generalized over different hashers",
2120 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2131 enum ImplicitHasherType<'tcx> {
2132 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2133 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2136 impl<'tcx> ImplicitHasherType<'tcx> {
2137 /// Checks that `ty` is a target type without a BuildHasher.
2138 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2139 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2140 let params: Vec<_> = path
2148 .filter_map(|arg| match arg {
2149 GenericArg::Type(ty) => Some(ty),
2153 let params_len = params.len();
2155 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2157 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2158 Some(ImplicitHasherType::HashMap(
2161 snippet(cx, params[0].span, "K"),
2162 snippet(cx, params[1].span, "V"),
2164 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2165 Some(ImplicitHasherType::HashSet(
2168 snippet(cx, params[0].span, "T"),
2178 fn type_name(&self) -> &'static str {
2180 ImplicitHasherType::HashMap(..) => "HashMap",
2181 ImplicitHasherType::HashSet(..) => "HashSet",
2185 fn type_arguments(&self) -> String {
2187 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2188 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2192 fn ty(&self) -> Ty<'tcx> {
2194 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2198 fn span(&self) -> Span {
2200 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2205 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2206 cx: &'a LateContext<'a, 'tcx>,
2207 found: Vec<ImplicitHasherType<'tcx>>,
2210 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2211 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2212 Self { cx, found: vec![] }
2216 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2217 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2218 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2219 self.found.push(target);
2225 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2226 NestedVisitorMap::None
2230 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2231 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2232 cx: &'a LateContext<'a, 'tcx>,
2233 body: &'a TypeckTables<'tcx>,
2234 target: &'b ImplicitHasherType<'tcx>,
2235 suggestions: BTreeMap<Span, String>,
2238 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2239 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2244 suggestions: BTreeMap::new(),
2249 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2250 fn visit_body(&mut self, body: &'tcx Body) {
2251 let prev_body = self.body;
2252 self.body = self.cx.tcx.body_tables(body.id());
2253 walk_body(self, body);
2254 self.body = prev_body;
2257 fn visit_expr(&mut self, e: &'tcx Expr) {
2259 if let ExprKind::Call(ref fun, ref args) = e.node;
2260 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2261 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2263 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2267 if match_path(ty_path, &paths::HASHMAP) {
2268 if method.ident.name == "new" {
2270 .insert(e.span, "HashMap::default()".to_string());
2271 } else if method.ident.name == "with_capacity" {
2272 self.suggestions.insert(
2275 "HashMap::with_capacity_and_hasher({}, Default::default())",
2276 snippet(self.cx, args[0].span, "capacity"),
2280 } else if match_path(ty_path, &paths::HASHSET) {
2281 if method.ident.name == "new" {
2283 .insert(e.span, "HashSet::default()".to_string());
2284 } else if method.ident.name == "with_capacity" {
2285 self.suggestions.insert(
2288 "HashSet::with_capacity_and_hasher({}, Default::default())",
2289 snippet(self.cx, args[0].span, "capacity"),
2300 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2301 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2305 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2307 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2308 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2311 /// **Known problems:** None.
2317 /// *(r as *const _ as *mut _) += 1;
2322 /// Instead consider using interior mutability types.
2325 /// fn x(r: &UnsafeCell<i32>) {
2331 declare_clippy_lint! {
2332 pub CAST_REF_TO_MUT,
2334 "a cast of reference to a mutable pointer"
2337 pub struct RefToMut;
2339 impl LintPass for RefToMut {
2340 fn get_lints(&self) -> LintArray {
2341 lint_array!(CAST_REF_TO_MUT)
2344 fn name(&self) -> &'static str {
2349 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2350 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2352 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2353 if let ExprKind::Cast(e, t) = &e.node;
2354 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2355 if let ExprKind::Cast(e, t) = &e.node;
2356 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2357 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2363 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",