1 #![allow(clippy::default_hash_types)]
4 use std::cmp::Ordering;
5 use std::collections::BTreeMap;
7 use if_chain::if_chain;
9 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
11 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
12 use rustc::ty::layout::LayoutOf;
13 use rustc::ty::{self, InferTy, Ty, TyCtxt, TypeckTables};
14 use rustc::{declare_tool_lint, lint_array};
15 use rustc_errors::Applicability;
16 use rustc_target::spec::abi::Abi;
17 use rustc_typeck::hir_ty_to_ty;
18 use syntax::ast::{FloatTy, IntTy, UintTy};
19 use syntax::errors::DiagnosticBuilder;
20 use syntax::source_map::Span;
22 use crate::consts::{constant, Constant};
23 use crate::utils::paths;
25 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
26 match_def_path, match_path, multispan_sugg, same_tys, sext, snippet, snippet_opt, snippet_with_applicability,
27 span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext, AbsolutePathBuffer,
30 /// Handles all the linting of funky types
33 declare_clippy_lint! {
34 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
36 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
37 /// the heap. So if you `Box` it, you just add another level of indirection
38 /// without any benefit whatsoever.
40 /// **Known problems:** None.
45 /// values: Box<Vec<Foo>>,
58 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
61 declare_clippy_lint! {
62 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
64 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
65 /// the heap. So if you `Box` its contents, you just add another level of indirection.
67 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
73 /// values: Vec<Box<i32>>,
86 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
89 declare_clippy_lint! {
90 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
93 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
94 /// represents an optional optional value which is logically the same thing as an optional
95 /// value but has an unneeded extra level of wrapping.
97 /// **Known problems:** None.
101 /// fn x() -> Option<Option<u32>> {
107 "usage of `Option<Option<T>>`"
110 declare_clippy_lint! {
111 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
112 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
114 /// **Why is this bad?** Gankro says:
116 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
117 /// pointers and indirection.
118 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
120 /// > "only" amortized for push/pop, should be faster in the general case for
121 /// almost every possible
122 /// > workload, and isn't even amortized at all if you can predict the capacity
125 /// > `LinkedList`s are only really good if you're doing a lot of merging or
126 /// splitting of lists.
127 /// > This is because they can just mangle some pointers instead of actually
128 /// copying the data. Even
129 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
130 /// can still be better
131 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
133 /// **Known problems:** False positives – the instances where using a
134 /// `LinkedList` makes sense are few and far between, but they can still happen.
138 /// let x = LinkedList::new();
142 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
145 declare_clippy_lint! {
146 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
148 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
151 /// **Known problems:** None.
155 /// fn foo(bar: &Box<T>) { ... }
161 /// fn foo(bar: &T) { ... }
165 "a borrow of a boxed type"
168 impl LintPass for TypePass {
169 fn get_lints(&self) -> LintArray {
170 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
173 fn name(&self) -> &'static str {
178 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
179 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
180 // Skip trait implementations; see issue #605.
181 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find_by_hir_id(cx.tcx.hir().get_parent_item(id)) {
182 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
187 check_fn_decl(cx, decl);
190 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
191 check_ty(cx, &field.ty, false);
194 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
196 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
197 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
202 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
203 if let Some(ref ty) = local.ty {
204 check_ty(cx, ty, true);
209 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
210 for input in &decl.inputs {
211 check_ty(cx, input, false);
214 if let FunctionRetTy::Return(ref ty) = decl.output {
215 check_ty(cx, ty, false);
219 /// Checks if `qpath` has last segment with type parameter matching `path`
220 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
221 let last = last_path_segment(qpath);
223 if let Some(ref params) = last.args;
224 if !params.parenthesized;
225 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
226 GenericArg::Type(ty) => Some(ty),
229 if let TyKind::Path(ref qpath) = ty.node;
230 if let Some(did) = cx.tables.qpath_def(qpath, ty.hir_id).opt_def_id();
231 if match_def_path(cx.tcx, did, path);
239 /// Recursively check for `TypePass` lints in the given type. Stop at the first
242 /// The parameter `is_local` distinguishes the context of the type; types from
243 /// local bindings should only be checked for the `BORROWED_BOX` lint.
244 #[allow(clippy::too_many_lines)]
245 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
246 if in_macro(hir_ty.span) {
250 TyKind::Path(ref qpath) if !is_local => {
251 let hir_id = hir_ty.hir_id;
252 let def = cx.tables.qpath_def(qpath, hir_id);
253 if let Some(def_id) = def.opt_def_id() {
254 if Some(def_id) == cx.tcx.lang_items().owned_box() {
255 if match_type_parameter(cx, qpath, &paths::VEC) {
260 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
261 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
263 return; // don't recurse into the type
265 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
267 // Get the _ part of Vec<_>
268 if let Some(ref last) = last_path_segment(qpath).args;
269 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
270 GenericArg::Type(ty) => Some(ty),
273 // ty is now _ at this point
274 if let TyKind::Path(ref ty_qpath) = ty.node;
275 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
276 if let Some(def_id) = def.opt_def_id();
277 if Some(def_id) == cx.tcx.lang_items().owned_box();
278 // At this point, we know ty is Box<T>, now get T
279 if let Some(ref last) = last_path_segment(ty_qpath).args;
280 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
281 GenericArg::Type(ty) => Some(ty),
285 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
286 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
291 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
293 format!("Vec<{}>", ty_ty),
294 Applicability::MachineApplicable,
296 return; // don't recurse into the type
300 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
301 if match_type_parameter(cx, qpath, &paths::OPTION) {
306 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
307 enum if you need to distinguish all 3 cases",
309 return; // don't recurse into the type
311 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
316 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
317 "a VecDeque might work",
319 return; // don't recurse into the type
323 QPath::Resolved(Some(ref ty), ref p) => {
324 check_ty(cx, ty, is_local);
325 for ty in p.segments.iter().flat_map(|seg| {
328 .map_or_else(|| [].iter(), |params| params.args.iter())
329 .filter_map(|arg| match arg {
330 GenericArg::Type(ty) => Some(ty),
334 check_ty(cx, ty, is_local);
337 QPath::Resolved(None, ref p) => {
338 for ty in p.segments.iter().flat_map(|seg| {
341 .map_or_else(|| [].iter(), |params| params.args.iter())
342 .filter_map(|arg| match arg {
343 GenericArg::Type(ty) => Some(ty),
347 check_ty(cx, ty, is_local);
350 QPath::TypeRelative(ref ty, ref seg) => {
351 check_ty(cx, ty, is_local);
352 if let Some(ref params) = seg.args {
353 for ty in params.args.iter().filter_map(|arg| match arg {
354 GenericArg::Type(ty) => Some(ty),
357 check_ty(cx, ty, is_local);
363 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
365 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
366 check_ty(cx, ty, is_local)
368 TyKind::Tup(ref tys) => {
370 check_ty(cx, ty, is_local);
377 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
378 match mut_ty.ty.node {
379 TyKind::Path(ref qpath) => {
380 let hir_id = mut_ty.ty.hir_id;
381 let def = cx.tables.qpath_def(qpath, hir_id);
383 if let Some(def_id) = def.opt_def_id();
384 if Some(def_id) == cx.tcx.lang_items().owned_box();
385 if let QPath::Resolved(None, ref path) = *qpath;
386 if let [ref bx] = *path.segments;
387 if let Some(ref params) = bx.args;
388 if !params.parenthesized;
389 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
390 GenericArg::Type(ty) => Some(ty),
394 if is_any_trait(inner) {
395 // Ignore `Box<Any>` types; see issue #1884 for details.
399 let ltopt = if lt.is_elided() {
402 format!("{} ", lt.name.ident().as_str())
404 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
409 let mut applicability = Applicability::MachineApplicable;
414 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
420 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
422 Applicability::Unspecified,
424 return; // don't recurse into the type
427 check_ty(cx, &mut_ty.ty, is_local);
429 _ => check_ty(cx, &mut_ty.ty, is_local),
433 // Returns true if given type is `Any` trait.
434 fn is_any_trait(t: &hir::Ty) -> bool {
436 if let TyKind::TraitObject(ref traits, _) = t.node;
437 if traits.len() >= 1;
438 // Only Send/Sync can be used as additional traits, so it is enough to
439 // check only the first trait.
440 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
451 declare_clippy_lint! {
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.
467 "creating a let binding to a value of unit type, which usually can't be used afterwards"
470 impl LintPass for LetPass {
471 fn get_lints(&self) -> LintArray {
472 lint_array!(LET_UNIT_VALUE)
475 fn name(&self) -> &'static str {
480 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
481 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
482 if let StmtKind::Local(ref local) = stmt.node {
483 if is_unit(cx.tables.pat_ty(&local.pat)) {
484 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
487 if higher::is_from_for_desugar(local) {
495 "this let-binding has unit value. Consider omitting `let {} =`",
496 snippet(cx, local.pat.span, "..")
504 declare_clippy_lint! {
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.
539 "comparing unit values"
544 impl LintPass for UnitCmp {
545 fn get_lints(&self) -> LintArray {
546 lint_array!(UNIT_CMP)
549 fn name(&self) -> &'static str {
554 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
555 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
556 if in_macro(expr.span) {
559 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
561 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
562 let result = match op {
563 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
571 "{}-comparison of unit values detected. This will always be {}",
581 declare_clippy_lint! {
582 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
583 /// unit literal (`()`).
585 /// **Why is this bad?** This is likely the result of an accidental semicolon.
587 /// **Known problems:** None.
598 "passing unit to a function"
603 impl LintPass for UnitArg {
604 fn get_lints(&self) -> LintArray {
605 lint_array!(UNIT_ARG)
608 fn name(&self) -> &'static str {
613 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
614 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
615 if in_macro(expr.span) {
619 // apparently stuff in the desugaring of `?` can trigger this
620 // so check for that here
621 // only the calls to `Try::from_error` is marked as desugared,
622 // so we need to check both the current Expr and its parent.
623 if is_questionmark_desugar_marked_call(expr) {
627 let map = &cx.tcx.hir();
628 let opt_parent_node = map.find_by_hir_id(map.get_parent_node_by_hir_id(expr.hir_id));
629 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
630 if is_questionmark_desugar_marked_call(parent_expr);
637 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
639 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
640 if let ExprKind::Match(.., match_source) = &arg.node {
641 if *match_source == MatchSource::TryDesugar {
650 "passing a unit value to a function",
651 "if you intended to pass a unit value, use a unit literal instead",
653 Applicability::MachineApplicable,
663 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
664 use syntax_pos::hygiene::CompilerDesugaringKind;
665 if let ExprKind::Call(ref callee, _) = expr.node {
666 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
672 fn is_unit(ty: Ty<'_>) -> bool {
674 ty::Tuple(slice) if slice.is_empty() => true,
679 fn is_unit_literal(expr: &Expr) -> bool {
681 ExprKind::Tup(ref slice) if slice.is_empty() => true,
688 declare_clippy_lint! {
689 /// **What it does:** Checks for casts from any numerical to a float type where
690 /// the receiving type cannot store all values from the original type without
691 /// rounding errors. This possible rounding is to be expected, so this lint is
692 /// `Allow` by default.
694 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
695 /// or any 64-bit integer to `f64`.
697 /// **Why is this bad?** It's not bad at all. But in some applications it can be
698 /// helpful to know where precision loss can take place. This lint can help find
699 /// those places in the code.
701 /// **Known problems:** None.
705 /// let x = u64::MAX;
708 pub CAST_PRECISION_LOSS,
710 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
713 declare_clippy_lint! {
714 /// **What it does:** Checks for casts from a signed to an unsigned numerical
715 /// type. In this case, negative values wrap around to large positive values,
716 /// which can be quite surprising in practice. However, as the cast works as
717 /// defined, this lint is `Allow` by default.
719 /// **Why is this bad?** Possibly surprising results. You can activate this lint
720 /// as a one-time check to see where numerical wrapping can arise.
722 /// **Known problems:** None.
727 /// y as u128 // will return 18446744073709551615
731 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
734 declare_clippy_lint! {
735 /// **What it does:** Checks for on casts between numerical types that may
736 /// truncate large values. This is expected behavior, so the cast is `Allow` by
739 /// **Why is this bad?** In some problem domains, it is good practice to avoid
740 /// truncation. This lint can be activated to help assess where additional
741 /// checks could be beneficial.
743 /// **Known problems:** None.
747 /// fn as_u8(x: u64) -> u8 {
751 pub CAST_POSSIBLE_TRUNCATION,
753 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
756 declare_clippy_lint! {
757 /// **What it does:** Checks for casts from an unsigned type to a signed type of
758 /// the same size. Performing such a cast is a 'no-op' for the compiler,
759 /// i.e., nothing is changed at the bit level, and the binary representation of
760 /// the value is reinterpreted. This can cause wrapping if the value is too big
761 /// for the target signed type. However, the cast works as defined, so this lint
762 /// is `Allow` by default.
764 /// **Why is this bad?** While such a cast is not bad in itself, the results can
765 /// be surprising when this is not the intended behavior, as demonstrated by the
768 /// **Known problems:** None.
772 /// u32::MAX as i32 // will yield a value of `-1`
774 pub CAST_POSSIBLE_WRAP,
776 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
779 declare_clippy_lint! {
780 /// **What it does:** Checks for on casts between numerical types that may
781 /// be replaced by safe conversion functions.
783 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
784 /// conversions, including silently lossy conversions. Conversion functions such
785 /// as `i32::from` will only perform lossless conversions. Using the conversion
786 /// functions prevents conversions from turning into silent lossy conversions if
787 /// the types of the input expressions ever change, and make it easier for
788 /// people reading the code to know that the conversion is lossless.
790 /// **Known problems:** None.
794 /// fn as_u64(x: u8) -> u64 {
799 /// Using `::from` would look like this:
802 /// fn as_u64(x: u8) -> u64 {
808 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
811 declare_clippy_lint! {
812 /// **What it does:** Checks for casts to the same type.
814 /// **Why is this bad?** It's just unnecessary.
816 /// **Known problems:** None.
820 /// let _ = 2i32 as i32
822 pub UNNECESSARY_CAST,
824 "cast to the same type, e.g., `x as i32` where `x: i32`"
827 declare_clippy_lint! {
828 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
829 /// more-strictly-aligned pointer
831 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
834 /// **Known problems:** None.
838 /// let _ = (&1u8 as *const u8) as *const u16;
839 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
841 pub CAST_PTR_ALIGNMENT,
843 "cast from a pointer to a more-strictly-aligned pointer"
846 declare_clippy_lint! {
847 /// **What it does:** Checks for casts of function pointers to something other than usize
849 /// **Why is this bad?**
850 /// Casting a function pointer to anything other than usize/isize is not portable across
851 /// architectures, because you end up losing bits if the target type is too small or end up with a
852 /// bunch of extra bits that waste space and add more instructions to the final binary than
853 /// strictly necessary for the problem
855 /// Casting to isize also doesn't make sense since there are no signed addresses.
861 /// fn fun() -> i32 { 1 }
862 /// let a = fun as i64;
865 /// fn fun2() -> i32 { 1 }
866 /// let a = fun2 as usize;
868 pub FN_TO_NUMERIC_CAST,
870 "casting a function pointer to a numeric type other than usize"
873 declare_clippy_lint! {
874 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
877 /// **Why is this bad?**
878 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
879 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
880 /// a comment) to perform the truncation.
886 /// fn fn1() -> i16 {
889 /// let _ = fn1 as i32;
891 /// // Better: Cast to usize first, then comment with the reason for the truncation
892 /// fn fn2() -> i16 {
895 /// let fn_ptr = fn2 as usize;
896 /// let fn_ptr_truncated = fn_ptr as i32;
898 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
900 "casting a function pointer to a numeric type not wide enough to store the address"
903 /// Returns the size in bits of an integral type.
904 /// Will return 0 if the type is not an int or uint variant
905 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
907 ty::Int(i) => match i {
908 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
915 ty::Uint(i) => match i {
916 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
927 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
929 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
934 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
935 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
936 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
937 let arch_dependent_str = "on targets with 64-bit wide pointers ";
938 let from_nbits_str = if arch_dependent {
940 } else if is_isize_or_usize(cast_from) {
941 "32 or 64".to_owned()
943 int_ty_to_nbits(cast_from, cx.tcx).to_string()
950 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
951 is only {4} bits wide)",
953 if cast_to_f64 { "f64" } else { "f32" },
954 if arch_dependent { arch_dependent_str } else { "" },
961 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
962 if let ExprKind::Binary(_, _, _) = op.node {
963 if snip.starts_with('(') && snip.ends_with(')') {
970 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
971 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
972 if in_constant(cx, expr.hir_id) {
975 // The suggestion is to use a function call, so if the original expression
976 // has parens on the outside, they are no longer needed.
977 let mut applicability = Applicability::MachineApplicable;
978 let opt = snippet_opt(cx, op.span);
979 let sugg = if let Some(ref snip) = opt {
980 if should_strip_parens(op, snip) {
981 &snip[1..snip.len() - 1]
986 applicability = Applicability::HasPlaceholders;
995 "casting {} to {} may become silently lossy if types change",
999 format!("{}::from({})", cast_to, sugg),
1010 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1011 if !cast_from.is_signed() || cast_to.is_signed() {
1015 // don't lint for positive constants
1016 let const_val = constant(cx, &cx.tables, op);
1018 if let Some((const_val, _)) = const_val;
1019 if let Constant::Int(n) = const_val;
1020 if let ty::Int(ity) = cast_from.sty;
1021 if sext(cx.tcx, n, ity) >= 0;
1031 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1035 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1036 let arch_64_suffix = " on targets with 64-bit wide pointers";
1037 let arch_32_suffix = " on targets with 32-bit wide pointers";
1038 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1039 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1040 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1041 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1042 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1043 (true, true) | (false, false) => (
1044 to_nbits < from_nbits,
1046 to_nbits == from_nbits && cast_unsigned_to_signed,
1056 to_nbits <= 32 && cast_unsigned_to_signed,
1062 cast_unsigned_to_signed,
1063 if from_nbits == 64 {
1070 if span_truncation {
1073 CAST_POSSIBLE_TRUNCATION,
1076 "casting {} to {} may truncate the value{}",
1079 match suffix_truncation {
1080 ArchSuffix::_32 => arch_32_suffix,
1081 ArchSuffix::_64 => arch_64_suffix,
1082 ArchSuffix::None => "",
1093 "casting {} to {} may wrap around the value{}",
1097 ArchSuffix::_32 => arch_32_suffix,
1098 ArchSuffix::_64 => arch_64_suffix,
1099 ArchSuffix::None => "",
1106 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1107 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1108 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1109 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1110 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1112 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1116 impl LintPass for CastPass {
1117 fn get_lints(&self) -> LintArray {
1119 CAST_PRECISION_LOSS,
1121 CAST_POSSIBLE_TRUNCATION,
1127 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1131 fn name(&self) -> &'static str {
1136 // Check if the given type is either `core::ffi::c_void` or
1137 // one of the platform specific `libc::<platform>::c_void` of libc.
1138 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1139 if let ty::Adt(adt, _) = ty.sty {
1140 let mut apb = AbsolutePathBuffer { names: vec![] };
1141 tcx.push_item_path(&mut apb, adt.did, false);
1143 if apb.names.is_empty() {
1146 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1153 /// Returns the mantissa bits wide of a fp type.
1154 /// Will return 0 if the type is not a fp
1155 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1157 ty::Float(FloatTy::F32) => 23,
1158 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1163 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1164 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1165 if let ExprKind::Cast(ref ex, _) = expr.node {
1166 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1167 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1168 if let ExprKind::Lit(ref lit) = ex.node {
1169 use syntax::ast::{LitIntType, LitKind};
1170 if let LitKind::Int(n, _) = lit.node {
1171 if cast_to.is_fp() {
1172 let from_nbits = 128 - n.leading_zeros();
1173 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1174 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1179 &format!("casting integer literal to {} is unnecessary", cast_to),
1181 format!("{}_{}", n, cast_to),
1182 Applicability::MachineApplicable,
1189 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1191 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1197 "casting to the same type is unnecessary (`{}` -> `{}`)",
1205 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1206 match (cast_from.is_integral(), cast_to.is_integral()) {
1208 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1209 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1214 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1215 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1217 if from_nbits < to_nbits {
1218 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1224 CAST_POSSIBLE_TRUNCATION,
1226 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1228 if !cast_to.is_signed() {
1233 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1238 check_loss_of_sign(cx, expr, ex, cast_from, cast_to);
1239 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1240 check_lossless(cx, expr, ex, cast_from, cast_to);
1243 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1246 CAST_POSSIBLE_TRUNCATION,
1248 "casting f64 to f32 may truncate the value",
1251 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1252 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1259 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1260 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1261 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1262 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1263 if from_align < to_align;
1264 // with c_void, we inherently need to trust the user
1265 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1271 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1279 fn lint_fn_to_numeric_cast(
1280 cx: &LateContext<'_, '_>,
1286 // We only want to check casts to `ty::Uint` or `ty::Int`
1288 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1291 match cast_from.sty {
1292 ty::FnDef(..) | ty::FnPtr(_) => {
1293 let mut applicability = Applicability::MachineApplicable;
1294 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1296 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1297 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1300 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1303 "casting function pointer `{}` to `{}`, which truncates the value",
1304 from_snippet, cast_to
1307 format!("{} as usize", from_snippet),
1310 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1315 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1317 format!("{} as usize", from_snippet),
1326 declare_clippy_lint! {
1327 /// **What it does:** Checks for types used in structs, parameters and `let`
1328 /// declarations above a certain complexity threshold.
1330 /// **Why is this bad?** Too complex types make the code less readable. Consider
1331 /// using a `type` definition to simplify them.
1333 /// **Known problems:** None.
1338 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1341 pub TYPE_COMPLEXITY,
1343 "usage of very complex types that might be better factored into `type` definitions"
1346 pub struct TypeComplexityPass {
1350 impl TypeComplexityPass {
1351 pub fn new(threshold: u64) -> Self {
1356 impl LintPass for TypeComplexityPass {
1357 fn get_lints(&self) -> LintArray {
1358 lint_array!(TYPE_COMPLEXITY)
1361 fn name(&self) -> &'static str {
1362 "TypeComplexityPass"
1366 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1369 cx: &LateContext<'a, 'tcx>,
1376 self.check_fndecl(cx, decl);
1379 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1380 // enum variants are also struct fields now
1381 self.check_type(cx, &field.ty);
1384 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1386 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1387 // functions, enums, structs, impls and traits are covered
1392 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1394 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1395 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1396 // methods with default impl are covered by check_fn
1401 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1403 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1404 // methods are covered by check_fn
1409 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1410 if let Some(ref ty) = local.ty {
1411 self.check_type(cx, ty);
1416 impl<'a, 'tcx> TypeComplexityPass {
1417 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1418 for arg in &decl.inputs {
1419 self.check_type(cx, arg);
1421 if let Return(ref ty) = decl.output {
1422 self.check_type(cx, ty);
1426 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1427 if in_macro(ty.span) {
1431 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1432 visitor.visit_ty(ty);
1436 if score > self.threshold {
1441 "very complex type used. Consider factoring parts into `type` definitions",
1447 /// Walks a type and assigns a complexity score to it.
1448 struct TypeComplexityVisitor {
1449 /// total complexity score of the type
1451 /// current nesting level
1455 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1456 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1457 let (add_score, sub_nest) = match ty.node {
1458 // _, &x and *x have only small overhead; don't mess with nesting level
1459 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1461 // the "normal" components of a type: named types, arrays/tuples
1462 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1464 // function types bring a lot of overhead
1465 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1467 TyKind::TraitObject(ref param_bounds, _) => {
1468 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1469 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1470 GenericParamKind::Lifetime { .. } => true,
1474 if has_lifetime_parameters {
1475 // complex trait bounds like A<'a, 'b>
1478 // simple trait bounds like A + B
1485 self.score += add_score;
1486 self.nest += sub_nest;
1488 self.nest -= sub_nest;
1490 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1491 NestedVisitorMap::None
1495 declare_clippy_lint! {
1496 /// **What it does:** Checks for expressions where a character literal is cast
1497 /// to `u8` and suggests using a byte literal instead.
1499 /// **Why is this bad?** In general, casting values to smaller types is
1500 /// error-prone and should be avoided where possible. In the particular case of
1501 /// converting a character literal to u8, it is easy to avoid by just using a
1502 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1503 /// than `'a' as u8`.
1505 /// **Known problems:** None.
1512 /// A better version, using the byte literal:
1519 "casting a character literal to u8"
1522 pub struct CharLitAsU8;
1524 impl LintPass for CharLitAsU8 {
1525 fn get_lints(&self) -> LintArray {
1526 lint_array!(CHAR_LIT_AS_U8)
1529 fn name(&self) -> &'static str {
1534 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1535 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1536 use syntax::ast::{LitKind, UintTy};
1538 if let ExprKind::Cast(ref e, _) = expr.node {
1539 if let ExprKind::Lit(ref l) = e.node {
1540 if let LitKind::Char(_) = l.node {
1541 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1542 let msg = "casting character literal to u8. `char`s \
1543 are 4 bytes wide in rust, so casting to u8 \
1546 "Consider using a byte literal instead:\nb{}",
1547 snippet(cx, e.span, "'x'")
1549 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1557 declare_clippy_lint! {
1558 /// **What it does:** Checks for comparisons where one side of the relation is
1559 /// either the minimum or maximum value for its type and warns if it involves a
1560 /// case that is always true or always false. Only integer and boolean types are
1563 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1564 /// that is is possible for `x` to be less than the minimum. Expressions like
1565 /// `max < x` are probably mistakes.
1567 /// **Known problems:** For `usize` the size of the current compile target will
1568 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1569 /// a comparison to detect target pointer width will trigger this lint. One can
1570 /// use `mem::sizeof` and compare its value or conditional compilation
1572 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1577 /// let vec: Vec<isize> = vec![];
1578 /// if vec.len() <= 0 {}
1579 /// if 100 > std::i32::MAX {}
1581 pub ABSURD_EXTREME_COMPARISONS,
1583 "a comparison with a maximum or minimum value that is always true or false"
1586 pub struct AbsurdExtremeComparisons;
1588 impl LintPass for AbsurdExtremeComparisons {
1589 fn get_lints(&self) -> LintArray {
1590 lint_array!(ABSURD_EXTREME_COMPARISONS)
1593 fn name(&self) -> &'static str {
1594 "AbsurdExtremeComparisons"
1603 struct ExtremeExpr<'a> {
1608 enum AbsurdComparisonResult {
1611 InequalityImpossible,
1614 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1615 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1616 let precast_ty = cx.tables.expr_ty(cast_exp);
1617 let cast_ty = cx.tables.expr_ty(expr);
1619 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1625 fn detect_absurd_comparison<'a, 'tcx>(
1626 cx: &LateContext<'a, 'tcx>,
1630 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1631 use crate::types::AbsurdComparisonResult::*;
1632 use crate::types::ExtremeType::*;
1633 use crate::utils::comparisons::*;
1635 // absurd comparison only makes sense on primitive types
1636 // primitive types don't implement comparison operators with each other
1637 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1641 // comparisons between fix sized types and target sized types are considered unanalyzable
1642 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1646 let normalized = normalize_comparison(op, lhs, rhs);
1647 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1653 let lx = detect_extreme_expr(cx, normalized_lhs);
1654 let rx = detect_extreme_expr(cx, normalized_rhs);
1659 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1660 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1666 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1667 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1668 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1669 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1673 Rel::Ne | Rel::Eq => return None,
1677 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1678 use crate::types::ExtremeType::*;
1680 let ty = cx.tables.expr_ty(expr);
1682 let cv = constant(cx, cx.tables, expr)?.0;
1684 let which = match (&ty.sty, cv) {
1685 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1686 (&ty::Int(ity), Constant::Int(i))
1687 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1692 (&ty::Bool, Constant::Bool(true)) => Maximum,
1693 (&ty::Int(ity), Constant::Int(i))
1694 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1698 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1702 Some(ExtremeExpr { which, expr })
1705 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1706 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1707 use crate::types::AbsurdComparisonResult::*;
1708 use crate::types::ExtremeType::*;
1710 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1711 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1712 if !in_macro(expr.span) {
1713 let msg = "this comparison involving the minimum or maximum element for this \
1714 type contains a case that is always true or always false";
1716 let conclusion = match result {
1717 AlwaysFalse => "this comparison is always false".to_owned(),
1718 AlwaysTrue => "this comparison is always true".to_owned(),
1719 InequalityImpossible => format!(
1720 "the case where the two sides are not equal never occurs, consider using {} == {} \
1722 snippet(cx, lhs.span, "lhs"),
1723 snippet(cx, rhs.span, "rhs")
1728 "because {} is the {} value for this type, {}",
1729 snippet(cx, culprit.expr.span, "x"),
1730 match culprit.which {
1731 Minimum => "minimum",
1732 Maximum => "maximum",
1737 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1744 declare_clippy_lint! {
1745 /// **What it does:** Checks for comparisons where the relation is always either
1746 /// true or false, but where one side has been upcast so that the comparison is
1747 /// necessary. Only integer types are checked.
1749 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1750 /// will mistakenly imply that it is possible for `x` to be outside the range of
1753 /// **Known problems:**
1754 /// https://github.com/rust-lang/rust-clippy/issues/886
1758 /// let x : u8 = ...; (x as u32) > 300
1760 pub INVALID_UPCAST_COMPARISONS,
1762 "a comparison involving an upcast which is always true or false"
1765 pub struct InvalidUpcastComparisons;
1767 impl LintPass for InvalidUpcastComparisons {
1768 fn get_lints(&self) -> LintArray {
1769 lint_array!(INVALID_UPCAST_COMPARISONS)
1772 fn name(&self) -> &'static str {
1773 "InvalidUpcastComparisons"
1777 #[derive(Copy, Clone, Debug, Eq)]
1784 #[allow(clippy::cast_sign_loss)]
1785 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1788 } else if u > (i128::max_value() as u128) {
1796 impl PartialEq for FullInt {
1797 fn eq(&self, other: &Self) -> bool {
1798 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1802 impl PartialOrd for FullInt {
1803 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1804 Some(match (self, other) {
1805 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1806 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1807 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1808 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1812 impl Ord for FullInt {
1813 fn cmp(&self, other: &Self) -> Ordering {
1814 self.partial_cmp(other)
1815 .expect("partial_cmp for FullInt can never return None")
1819 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1821 use syntax::ast::{IntTy, UintTy};
1823 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1824 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1825 let cast_ty = cx.tables.expr_ty(expr);
1826 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1827 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1830 match pre_cast_ty.sty {
1831 ty::Int(int_ty) => Some(match int_ty {
1833 FullInt::S(i128::from(i8::min_value())),
1834 FullInt::S(i128::from(i8::max_value())),
1837 FullInt::S(i128::from(i16::min_value())),
1838 FullInt::S(i128::from(i16::max_value())),
1841 FullInt::S(i128::from(i32::min_value())),
1842 FullInt::S(i128::from(i32::max_value())),
1845 FullInt::S(i128::from(i64::min_value())),
1846 FullInt::S(i128::from(i64::max_value())),
1848 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1850 FullInt::S(isize::min_value() as i128),
1851 FullInt::S(isize::max_value() as i128),
1854 ty::Uint(uint_ty) => Some(match uint_ty {
1856 FullInt::U(u128::from(u8::min_value())),
1857 FullInt::U(u128::from(u8::max_value())),
1860 FullInt::U(u128::from(u16::min_value())),
1861 FullInt::U(u128::from(u16::max_value())),
1864 FullInt::U(u128::from(u32::min_value())),
1865 FullInt::U(u128::from(u32::max_value())),
1868 FullInt::U(u128::from(u64::min_value())),
1869 FullInt::U(u128::from(u64::max_value())),
1871 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1873 FullInt::U(usize::min_value() as u128),
1874 FullInt::U(usize::max_value() as u128),
1884 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1885 let val = constant(cx, cx.tables, expr)?.0;
1886 if let Constant::Int(const_int) = val {
1887 match cx.tables.expr_ty(expr).sty {
1888 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1889 ty::Uint(_) => Some(FullInt::U(const_int)),
1897 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1898 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1901 INVALID_UPCAST_COMPARISONS,
1904 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1905 snippet(cx, cast_val.span, "the expression"),
1906 if always { "true" } else { "false" },
1912 fn upcast_comparison_bounds_err<'a, 'tcx>(
1913 cx: &LateContext<'a, 'tcx>,
1915 rel: comparisons::Rel,
1916 lhs_bounds: Option<(FullInt, FullInt)>,
1921 use crate::utils::comparisons::*;
1923 if let Some((lb, ub)) = lhs_bounds {
1924 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1925 if rel == Rel::Eq || rel == Rel::Ne {
1926 if norm_rhs_val < lb || norm_rhs_val > ub {
1927 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1929 } else if match rel {
1944 Rel::Eq | Rel::Ne => unreachable!(),
1946 err_upcast_comparison(cx, span, lhs, true)
1947 } else if match rel {
1962 Rel::Eq | Rel::Ne => unreachable!(),
1964 err_upcast_comparison(cx, span, lhs, false)
1970 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1971 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1972 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1973 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1974 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1980 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1981 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1983 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1984 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1989 declare_clippy_lint! {
1990 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1991 /// over different hashers and implicitly defaulting to the default hashing
1992 /// algorithm (SipHash).
1994 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1997 /// **Known problems:** Suggestions for replacing constructors can contain
1998 /// false-positives. Also applying suggestions can require modification of other
1999 /// pieces of code, possibly including external crates.
2003 /// # use std::collections::HashMap;
2004 /// # use std::hash::Hash;
2005 /// # trait Serialize {};
2006 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
2008 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
2010 pub IMPLICIT_HASHER,
2012 "missing generalization over different hashers"
2015 pub struct ImplicitHasher;
2017 impl LintPass for ImplicitHasher {
2018 fn get_lints(&self) -> LintArray {
2019 lint_array!(IMPLICIT_HASHER)
2022 fn name(&self) -> &'static str {
2027 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
2028 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
2029 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
2030 use syntax_pos::BytePos;
2032 fn suggestion<'a, 'tcx>(
2033 cx: &LateContext<'a, 'tcx>,
2034 db: &mut DiagnosticBuilder<'_>,
2035 generics_span: Span,
2036 generics_suggestion_span: Span,
2037 target: &ImplicitHasherType<'_>,
2038 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2040 let generics_snip = snippet(cx, generics_span, "");
2042 let generics_snip = if generics_snip.is_empty() {
2045 &generics_snip[1..generics_snip.len() - 1]
2050 "consider adding a type parameter".to_string(),
2053 generics_suggestion_span,
2055 "<{}{}S: ::std::hash::BuildHasher{}>",
2057 if generics_snip.is_empty() { "" } else { ", " },
2058 if vis.suggestions.is_empty() {
2061 // request users to add `Default` bound so that generic constructors can be used
2068 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2073 if !vis.suggestions.is_empty() {
2074 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2078 if !cx.access_levels.is_exported(cx.tcx.hir().hir_to_node_id(item.hir_id)) {
2083 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2084 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2087 for target in &vis.found {
2088 if differing_macro_contexts(item.span, target.span()) {
2092 let generics_suggestion_span = generics.span.substitute_dummy({
2093 let pos = snippet_opt(cx, item.span.until(target.span()))
2094 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2095 if let Some(pos) = pos {
2096 Span::new(pos, pos, item.span.data().ctxt)
2102 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2103 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2104 ctr_vis.visit_impl_item(item);
2112 "impl for `{}` should be generalized over different hashers",
2116 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2121 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2122 let body = cx.tcx.hir().body(body_id);
2124 for ty in &decl.inputs {
2125 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2128 for target in &vis.found {
2129 let generics_suggestion_span = generics.span.substitute_dummy({
2130 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2132 let i = snip.find("fn")?;
2133 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2135 .expect("failed to create span for type parameters");
2136 Span::new(pos, pos, item.span.data().ctxt)
2139 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2140 ctr_vis.visit_body(body);
2147 "parameter of type `{}` should be generalized over different hashers",
2151 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2162 enum ImplicitHasherType<'tcx> {
2163 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2164 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2167 impl<'tcx> ImplicitHasherType<'tcx> {
2168 /// Checks that `ty` is a target type without a BuildHasher.
2169 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2170 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2171 let params: Vec<_> = path
2179 .filter_map(|arg| match arg {
2180 GenericArg::Type(ty) => Some(ty),
2184 let params_len = params.len();
2186 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2188 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2189 Some(ImplicitHasherType::HashMap(
2192 snippet(cx, params[0].span, "K"),
2193 snippet(cx, params[1].span, "V"),
2195 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2196 Some(ImplicitHasherType::HashSet(
2199 snippet(cx, params[0].span, "T"),
2209 fn type_name(&self) -> &'static str {
2211 ImplicitHasherType::HashMap(..) => "HashMap",
2212 ImplicitHasherType::HashSet(..) => "HashSet",
2216 fn type_arguments(&self) -> String {
2218 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2219 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2223 fn ty(&self) -> Ty<'tcx> {
2225 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2229 fn span(&self) -> Span {
2231 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2236 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2237 cx: &'a LateContext<'a, 'tcx>,
2238 found: Vec<ImplicitHasherType<'tcx>>,
2241 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2242 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2243 Self { cx, found: vec![] }
2247 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2248 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2249 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2250 self.found.push(target);
2256 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2257 NestedVisitorMap::None
2261 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2262 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2263 cx: &'a LateContext<'a, 'tcx>,
2264 body: &'a TypeckTables<'tcx>,
2265 target: &'b ImplicitHasherType<'tcx>,
2266 suggestions: BTreeMap<Span, String>,
2269 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2270 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2275 suggestions: BTreeMap::new(),
2280 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2281 fn visit_body(&mut self, body: &'tcx Body) {
2282 let prev_body = self.body;
2283 self.body = self.cx.tcx.body_tables(body.id());
2284 walk_body(self, body);
2285 self.body = prev_body;
2288 fn visit_expr(&mut self, e: &'tcx Expr) {
2290 if let ExprKind::Call(ref fun, ref args) = e.node;
2291 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2292 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2294 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2298 if match_path(ty_path, &paths::HASHMAP) {
2299 if method.ident.name == "new" {
2301 .insert(e.span, "HashMap::default()".to_string());
2302 } else if method.ident.name == "with_capacity" {
2303 self.suggestions.insert(
2306 "HashMap::with_capacity_and_hasher({}, Default::default())",
2307 snippet(self.cx, args[0].span, "capacity"),
2311 } else if match_path(ty_path, &paths::HASHSET) {
2312 if method.ident.name == "new" {
2314 .insert(e.span, "HashSet::default()".to_string());
2315 } else if method.ident.name == "with_capacity" {
2316 self.suggestions.insert(
2319 "HashSet::with_capacity_and_hasher({}, Default::default())",
2320 snippet(self.cx, args[0].span, "capacity"),
2331 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2332 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2336 declare_clippy_lint! {
2337 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2339 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2340 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2343 /// **Known problems:** None.
2349 /// *(r as *const _ as *mut _) += 1;
2354 /// Instead consider using interior mutability types.
2357 /// use std::cell::UnsafeCell;
2359 /// fn x(r: &UnsafeCell<i32>) {
2365 pub CAST_REF_TO_MUT,
2367 "a cast of reference to a mutable pointer"
2370 pub struct RefToMut;
2372 impl LintPass for RefToMut {
2373 fn get_lints(&self) -> LintArray {
2374 lint_array!(CAST_REF_TO_MUT)
2377 fn name(&self) -> &'static str {
2382 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2383 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2385 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2386 if let ExprKind::Cast(e, t) = &e.node;
2387 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2388 if let ExprKind::Cast(e, t) = &e.node;
2389 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2390 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2396 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",