1 #![allow(clippy::default_hash_types)]
3 use crate::consts::{constant, Constant};
4 use crate::reexport::*;
5 use crate::utils::paths;
7 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
8 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
9 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
12 use if_chain::if_chain;
14 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
16 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
17 use rustc::ty::layout::LayoutOf;
18 use rustc::ty::{self, Ty, TyCtxt, TypeckTables};
19 use rustc::{declare_tool_lint, lint_array};
20 use rustc_errors::Applicability;
21 use rustc_target::spec::abi::Abi;
22 use rustc_typeck::hir_ty_to_ty;
24 use std::cmp::Ordering;
25 use std::collections::BTreeMap;
26 use syntax::ast::{FloatTy, IntTy, UintTy};
27 use syntax::errors::DiagnosticBuilder;
28 use syntax::source_map::Span;
30 /// Handles all the linting of funky types
33 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
35 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
36 /// the heap. So if you `Box` it, you just add another level of indirection
37 /// without any benefit whatsoever.
39 /// **Known problems:** None.
44 /// values: Box<Vec<Foo>>,
55 declare_clippy_lint! {
58 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
61 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
63 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
64 /// the heap. So if you `Box` its contents, you just add another level of indirection.
66 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
72 /// values: Vec<Box<i32>>,
83 declare_clippy_lint! {
86 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
89 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
92 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
93 /// represents an optional optional value which is logically the same thing as an optional
94 /// value but has an unneeded extra level of wrapping.
96 /// **Known problems:** None.
100 /// fn x() -> Option<Option<u32>> {
103 declare_clippy_lint! {
106 "usage of `Option<Option<T>>`"
109 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
110 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
112 /// **Why is this bad?** Gankro says:
114 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
115 /// pointers and indirection.
116 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
118 /// > "only" amortized for push/pop, should be faster in the general case for
119 /// almost every possible
120 /// > workload, and isn't even amortized at all if you can predict the capacity
123 /// > `LinkedList`s are only really good if you're doing a lot of merging or
124 /// splitting of lists.
125 /// > This is because they can just mangle some pointers instead of actually
126 /// copying the data. Even
127 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
128 /// can still be better
129 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
131 /// **Known problems:** False positives – the instances where using a
132 /// `LinkedList` makes sense are few and far between, but they can still happen.
136 /// let x = LinkedList::new();
138 declare_clippy_lint! {
141 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
144 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
146 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
149 /// **Known problems:** None.
153 /// fn foo(bar: &Box<T>) { ... }
159 /// fn foo(bar: &T) { ... }
161 declare_clippy_lint! {
164 "a borrow of a boxed type"
167 impl LintPass for TypePass {
168 fn get_lints(&self) -> LintArray {
169 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
172 fn name(&self) -> &'static str {
177 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
178 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
179 // skip trait implementations, see #605
180 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(id)) {
181 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
186 check_fn_decl(cx, decl);
189 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
190 check_ty(cx, &field.ty, false);
193 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
195 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
196 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
201 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
202 if let Some(ref ty) = local.ty {
203 check_ty(cx, ty, true);
208 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
209 for input in &decl.inputs {
210 check_ty(cx, input, false);
213 if let FunctionRetTy::Return(ref ty) = decl.output {
214 check_ty(cx, ty, false);
218 /// Check if `qpath` has last segment with type parameter matching `path`
219 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
220 let last = last_path_segment(qpath);
222 if let Some(ref params) = last.args;
223 if !params.parenthesized;
224 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
225 GenericArg::Type(ty) => Some(ty),
226 GenericArg::Lifetime(_) => None,
228 if let TyKind::Path(ref qpath) = ty.node;
229 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
230 if match_def_path(cx.tcx, did, path);
238 /// Recursively check for `TypePass` lints in the given type. Stop at the first
241 /// The parameter `is_local` distinguishes the context of the type; types from
242 /// local bindings should only be checked for the `BORROWED_BOX` lint.
243 #[allow(clippy::too_many_lines)]
244 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
245 if in_macro(hir_ty.span) {
249 TyKind::Path(ref qpath) if !is_local => {
250 let hir_id = cx.tcx.hir().node_to_hir_id(hir_ty.id);
251 let def = cx.tables.qpath_def(qpath, hir_id);
252 if let Some(def_id) = opt_def_id(def) {
253 if Some(def_id) == cx.tcx.lang_items().owned_box() {
254 if match_type_parameter(cx, qpath, &paths::VEC) {
259 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
260 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
262 return; // don't recurse into the type
264 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
266 // Get the _ part of Vec<_>
267 if let Some(ref last) = last_path_segment(qpath).args;
268 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
269 GenericArg::Type(ty) => Some(ty),
270 GenericArg::Lifetime(_) => None,
272 // ty is now _ at this point
273 if let TyKind::Path(ref ty_qpath) = ty.node;
274 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
275 if let Some(def_id) = opt_def_id(def);
276 if Some(def_id) == cx.tcx.lang_items().owned_box();
277 // At this point, we know ty is Box<T>, now get T
278 if let Some(ref last) = last_path_segment(ty_qpath).args;
279 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
280 GenericArg::Type(ty) => Some(ty),
281 GenericArg::Lifetime(_) => None,
284 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
285 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
290 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
292 format!("Vec<{}>", ty_ty),
293 Applicability::MachineApplicable,
295 return; // don't recurse into the type
299 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
300 if match_type_parameter(cx, qpath, &paths::OPTION) {
305 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
306 enum if you need to distinguish all 3 cases",
308 return; // don't recurse into the type
310 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
315 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
316 "a VecDeque might work",
318 return; // don't recurse into the type
322 QPath::Resolved(Some(ref ty), ref p) => {
323 check_ty(cx, ty, is_local);
324 for ty in p.segments.iter().flat_map(|seg| {
327 .map_or_else(|| [].iter(), |params| params.args.iter())
328 .filter_map(|arg| match arg {
329 GenericArg::Type(ty) => Some(ty),
330 GenericArg::Lifetime(_) => None,
333 check_ty(cx, ty, is_local);
336 QPath::Resolved(None, ref p) => {
337 for ty in p.segments.iter().flat_map(|seg| {
340 .map_or_else(|| [].iter(), |params| params.args.iter())
341 .filter_map(|arg| match arg {
342 GenericArg::Type(ty) => Some(ty),
343 GenericArg::Lifetime(_) => None,
346 check_ty(cx, ty, is_local);
349 QPath::TypeRelative(ref ty, ref seg) => {
350 check_ty(cx, ty, is_local);
351 if let Some(ref params) = seg.args {
352 for ty in params.args.iter().filter_map(|arg| match arg {
353 GenericArg::Type(ty) => Some(ty),
354 GenericArg::Lifetime(_) => None,
356 check_ty(cx, ty, is_local);
362 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
364 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
365 check_ty(cx, ty, is_local)
367 TyKind::Tup(ref tys) => {
369 check_ty(cx, ty, is_local);
376 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
377 match mut_ty.ty.node {
378 TyKind::Path(ref qpath) => {
379 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
380 let def = cx.tables.qpath_def(qpath, hir_id);
382 if let Some(def_id) = opt_def_id(def);
383 if Some(def_id) == cx.tcx.lang_items().owned_box();
384 if let QPath::Resolved(None, ref path) = *qpath;
385 if let [ref bx] = *path.segments;
386 if let Some(ref params) = bx.args;
387 if !params.parenthesized;
388 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
389 GenericArg::Type(ty) => Some(ty),
390 GenericArg::Lifetime(_) => None,
393 if is_any_trait(inner) {
394 // Ignore `Box<Any>` types, see #1884 for details.
398 let ltopt = if lt.is_elided() {
401 format!("{} ", lt.name.ident().as_str())
403 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
408 let mut applicability = Applicability::MachineApplicable;
413 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
419 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
421 Applicability::Unspecified,
423 return; // don't recurse into the type
426 check_ty(cx, &mut_ty.ty, is_local);
428 _ => check_ty(cx, &mut_ty.ty, is_local),
432 // Returns true if given type is `Any` trait.
433 fn is_any_trait(t: &hir::Ty) -> bool {
435 if let TyKind::TraitObject(ref traits, _) = t.node;
436 if traits.len() >= 1;
437 // Only Send/Sync can be used as additional traits, so it is enough to
438 // check only the first trait.
439 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
450 /// **What it does:** Checks for binding a unit value.
452 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
453 /// binding one is kind of pointless.
455 /// **Known problems:** None.
463 declare_clippy_lint! {
466 "creating a let binding to a value of unit type, which usually can't be used afterwards"
469 impl LintPass for LetPass {
470 fn get_lints(&self) -> LintArray {
471 lint_array!(LET_UNIT_VALUE)
474 fn name(&self) -> &'static str {
479 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
480 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
481 if let StmtKind::Local(ref local) = stmt.node {
482 if is_unit(cx.tables.pat_ty(&local.pat)) {
483 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
486 if higher::is_from_for_desugar(local) {
494 "this let-binding has unit value. Consider omitting `let {} =`",
495 snippet(cx, local.pat.span, "..")
503 /// **What it does:** Checks for comparisons to unit.
505 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
506 /// clumsily written constant. Mostly this happens when someone accidentally
507 /// adds semicolons at the end of the operands.
509 /// **Known problems:** None.
529 declare_clippy_lint! {
532 "comparing unit values"
537 impl LintPass for UnitCmp {
538 fn get_lints(&self) -> LintArray {
539 lint_array!(UNIT_CMP)
542 fn name(&self) -> &'static str {
547 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
548 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
549 if in_macro(expr.span) {
552 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
554 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
555 let result = match op {
556 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
564 "{}-comparison of unit values detected. This will always be {}",
574 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
575 /// unit literal (`()`).
577 /// **Why is this bad?** This is likely the result of an accidental semicolon.
579 /// **Known problems:** None.
588 declare_clippy_lint! {
591 "passing unit to a function"
596 impl LintPass for UnitArg {
597 fn get_lints(&self) -> LintArray {
598 lint_array!(UNIT_ARG)
601 fn name(&self) -> &'static str {
606 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
607 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
608 if in_macro(expr.span) {
612 // apparently stuff in the desugaring of `?` can trigger this
613 // so check for that here
614 // only the calls to `Try::from_error` is marked as desugared,
615 // so we need to check both the current Expr and its parent.
616 if is_questionmark_desugar_marked_call(expr) {
620 let map = &cx.tcx.hir();
621 let opt_parent_node = map.find(map.get_parent_node(expr.id));
622 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
623 if is_questionmark_desugar_marked_call(parent_expr);
630 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
632 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
633 if let ExprKind::Match(.., match_source) = &arg.node {
634 if *match_source == MatchSource::TryDesugar {
643 "passing a unit value to a function",
644 "if you intended to pass a unit value, use a unit literal instead",
646 Applicability::MachineApplicable,
656 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
657 use syntax_pos::hygiene::CompilerDesugaringKind;
658 if let ExprKind::Call(ref callee, _) = expr.node {
659 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
665 fn is_unit(ty: Ty<'_>) -> bool {
667 ty::Tuple(slice) if slice.is_empty() => true,
672 fn is_unit_literal(expr: &Expr) -> bool {
674 ExprKind::Tup(ref slice) if slice.is_empty() => true,
681 /// **What it does:** Checks for casts from any numerical to a float type where
682 /// the receiving type cannot store all values from the original type without
683 /// rounding errors. This possible rounding is to be expected, so this lint is
684 /// `Allow` by default.
686 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
687 /// or any 64-bit integer to `f64`.
689 /// **Why is this bad?** It's not bad at all. But in some applications it can be
690 /// helpful to know where precision loss can take place. This lint can help find
691 /// those places in the code.
693 /// **Known problems:** None.
697 /// let x = u64::MAX;
700 declare_clippy_lint! {
701 pub CAST_PRECISION_LOSS,
703 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
706 /// **What it does:** Checks for casts from a signed to an unsigned numerical
707 /// type. In this case, negative values wrap around to large positive values,
708 /// which can be quite surprising in practice. However, as the cast works as
709 /// defined, this lint is `Allow` by default.
711 /// **Why is this bad?** Possibly surprising results. You can activate this lint
712 /// as a one-time check to see where numerical wrapping can arise.
714 /// **Known problems:** None.
719 /// y as u128 // will return 18446744073709551615
721 declare_clippy_lint! {
724 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
727 /// **What it does:** Checks for on casts between numerical types that may
728 /// truncate large values. This is expected behavior, so the cast is `Allow` by
731 /// **Why is this bad?** In some problem domains, it is good practice to avoid
732 /// truncation. This lint can be activated to help assess where additional
733 /// checks could be beneficial.
735 /// **Known problems:** None.
739 /// fn as_u8(x: u64) -> u8 {
743 declare_clippy_lint! {
744 pub CAST_POSSIBLE_TRUNCATION,
746 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
749 /// **What it does:** Checks for casts from an unsigned type to a signed type of
750 /// the same size. Performing such a cast is a 'no-op' for the compiler,
751 /// i.e. nothing is changed at the bit level, and the binary representation of
752 /// the value is reinterpreted. This can cause wrapping if the value is too big
753 /// for the target signed type. However, the cast works as defined, so this lint
754 /// is `Allow` by default.
756 /// **Why is this bad?** While such a cast is not bad in itself, the results can
757 /// be surprising when this is not the intended behavior, as demonstrated by the
760 /// **Known problems:** None.
764 /// u32::MAX as i32 // will yield a value of `-1`
766 declare_clippy_lint! {
767 pub CAST_POSSIBLE_WRAP,
769 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
772 /// **What it does:** Checks for on casts between numerical types that may
773 /// be replaced by safe conversion functions.
775 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
776 /// conversions, including silently lossy conversions. Conversion functions such
777 /// as `i32::from` will only perform lossless conversions. Using the conversion
778 /// functions prevents conversions from turning into silent lossy conversions if
779 /// the types of the input expressions ever change, and make it easier for
780 /// people reading the code to know that the conversion is lossless.
782 /// **Known problems:** None.
786 /// fn as_u64(x: u8) -> u64 {
791 /// Using `::from` would look like this:
794 /// fn as_u64(x: u8) -> u64 {
798 declare_clippy_lint! {
801 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
804 /// **What it does:** Checks for casts to the same type.
806 /// **Why is this bad?** It's just unnecessary.
808 /// **Known problems:** None.
812 /// let _ = 2i32 as i32
814 declare_clippy_lint! {
815 pub UNNECESSARY_CAST,
817 "cast to the same type, e.g. `x as i32` where `x: i32`"
820 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
821 /// more-strictly-aligned pointer
823 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
826 /// **Known problems:** None.
830 /// let _ = (&1u8 as *const u8) as *const u16;
831 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
833 declare_clippy_lint! {
834 pub CAST_PTR_ALIGNMENT,
836 "cast from a pointer to a more-strictly-aligned pointer"
839 /// **What it does:** Checks for casts of function pointers to something other than usize
841 /// **Why is this bad?**
842 /// Casting a function pointer to anything other than usize/isize is not portable across
843 /// architectures, because you end up losing bits if the target type is too small or end up with a
844 /// bunch of extra bits that waste space and add more instructions to the final binary than
845 /// strictly necessary for the problem
847 /// Casting to isize also doesn't make sense since there are no signed addresses.
853 /// fn fun() -> i32 {}
854 /// let a = fun as i64;
857 /// fn fun2() -> i32 {}
858 /// let a = fun2 as usize;
860 declare_clippy_lint! {
861 pub FN_TO_NUMERIC_CAST,
863 "casting a function pointer to a numeric type other than usize"
866 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
869 /// **Why is this bad?**
870 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
871 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
872 /// a comment) to perform the truncation.
878 /// fn fn1() -> i16 {
881 /// let _ = fn1 as i32;
883 /// // Better: Cast to usize first, then comment with the reason for the truncation
884 /// fn fn2() -> i16 {
887 /// let fn_ptr = fn2 as usize;
888 /// let fn_ptr_truncated = fn_ptr as i32;
890 declare_clippy_lint! {
891 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
893 "casting a function pointer to a numeric type not wide enough to store the address"
896 /// Returns the size in bits of an integral type.
897 /// Will return 0 if the type is not an int or uint variant
898 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
900 ty::Int(i) => match i {
901 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
908 ty::Uint(i) => match i {
909 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
920 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
922 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
927 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
928 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
929 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
930 let arch_dependent_str = "on targets with 64-bit wide pointers ";
931 let from_nbits_str = if arch_dependent {
933 } else if is_isize_or_usize(cast_from) {
934 "32 or 64".to_owned()
936 int_ty_to_nbits(cast_from, cx.tcx).to_string()
943 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
944 is only {4} bits wide)",
946 if cast_to_f64 { "f64" } else { "f32" },
947 if arch_dependent { arch_dependent_str } else { "" },
954 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
955 if let ExprKind::Binary(_, _, _) = op.node {
956 if snip.starts_with('(') && snip.ends_with(')') {
963 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
964 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
965 if in_constant(cx, expr.id) {
968 // The suggestion is to use a function call, so if the original expression
969 // has parens on the outside, they are no longer needed.
970 let mut applicability = Applicability::MachineApplicable;
971 let opt = snippet_opt(cx, op.span);
972 let sugg = if let Some(ref snip) = opt {
973 if should_strip_parens(op, snip) {
974 &snip[1..snip.len() - 1]
979 applicability = Applicability::HasPlaceholders;
988 "casting {} to {} may become silently lossy if types change",
992 format!("{}::from({})", cast_to, sugg),
1003 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1004 if !cast_from.is_signed() || cast_to.is_signed() {
1008 // don't lint for positive constants
1009 let const_val = constant(cx, &cx.tables, op);
1011 if let Some((const_val, _)) = const_val;
1012 if let Constant::Int(n) = const_val;
1013 if let ty::Int(ity) = cast_from.sty;
1014 if sext(cx.tcx, n, ity) >= 0;
1024 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1028 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1029 let arch_64_suffix = " on targets with 64-bit wide pointers";
1030 let arch_32_suffix = " on targets with 32-bit wide pointers";
1031 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1032 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1033 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1034 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1035 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1036 (true, true) | (false, false) => (
1037 to_nbits < from_nbits,
1039 to_nbits == from_nbits && cast_unsigned_to_signed,
1049 to_nbits <= 32 && cast_unsigned_to_signed,
1055 cast_unsigned_to_signed,
1056 if from_nbits == 64 {
1063 if span_truncation {
1066 CAST_POSSIBLE_TRUNCATION,
1069 "casting {} to {} may truncate the value{}",
1072 match suffix_truncation {
1073 ArchSuffix::_32 => arch_32_suffix,
1074 ArchSuffix::_64 => arch_64_suffix,
1075 ArchSuffix::None => "",
1086 "casting {} to {} may wrap around the value{}",
1090 ArchSuffix::_32 => arch_32_suffix,
1091 ArchSuffix::_64 => arch_64_suffix,
1092 ArchSuffix::None => "",
1099 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1100 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1101 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1102 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1103 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1105 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1109 impl LintPass for CastPass {
1110 fn get_lints(&self) -> LintArray {
1112 CAST_PRECISION_LOSS,
1114 CAST_POSSIBLE_TRUNCATION,
1120 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1124 fn name(&self) -> &'static str {
1129 // Check if the given type is either `core::ffi::c_void` or
1130 // one of the platform specific `libc::<platform>::c_void` of libc.
1131 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1132 if let ty::Adt(adt, _) = ty.sty {
1133 let mut apb = AbsolutePathBuffer { names: vec![] };
1134 tcx.push_item_path(&mut apb, adt.did, false);
1136 if apb.names.is_empty() {
1139 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1146 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1147 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1148 if let ExprKind::Cast(ref ex, _) = expr.node {
1149 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1150 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1151 if let ExprKind::Lit(ref lit) = ex.node {
1152 use syntax::ast::{LitIntType, LitKind};
1154 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1156 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1162 "casting to the same type is unnecessary (`{}` -> `{}`)",
1170 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1171 match (cast_from.is_integral(), cast_to.is_integral()) {
1173 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1174 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1179 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1180 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1182 if from_nbits < to_nbits {
1183 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1189 CAST_POSSIBLE_TRUNCATION,
1191 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1193 if !cast_to.is_signed() {
1198 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1203 check_loss_of_sign(cx, expr, ex, cast_from, cast_to);
1204 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1205 check_lossless(cx, expr, ex, cast_from, cast_to);
1208 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1211 CAST_POSSIBLE_TRUNCATION,
1213 "casting f64 to f32 may truncate the value",
1216 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1217 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1224 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1225 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1226 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1227 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1228 if from_align < to_align;
1229 // with c_void, we inherently need to trust the user
1230 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1236 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1244 fn lint_fn_to_numeric_cast(
1245 cx: &LateContext<'_, '_>,
1251 // We only want to check casts to `ty::Uint` or `ty::Int`
1253 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1256 match cast_from.sty {
1257 ty::FnDef(..) | ty::FnPtr(_) => {
1258 let mut applicability = Applicability::MachineApplicable;
1259 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1261 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1262 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1265 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1268 "casting function pointer `{}` to `{}`, which truncates the value",
1269 from_snippet, cast_to
1272 format!("{} as usize", from_snippet),
1275 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1280 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1282 format!("{} as usize", from_snippet),
1291 /// **What it does:** Checks for types used in structs, parameters and `let`
1292 /// declarations above a certain complexity threshold.
1294 /// **Why is this bad?** Too complex types make the code less readable. Consider
1295 /// using a `type` definition to simplify them.
1297 /// **Known problems:** None.
1302 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1305 declare_clippy_lint! {
1306 pub TYPE_COMPLEXITY,
1308 "usage of very complex types that might be better factored into `type` definitions"
1311 pub struct TypeComplexityPass {
1315 impl TypeComplexityPass {
1316 pub fn new(threshold: u64) -> Self {
1321 impl LintPass for TypeComplexityPass {
1322 fn get_lints(&self) -> LintArray {
1323 lint_array!(TYPE_COMPLEXITY)
1326 fn name(&self) -> &'static str {
1327 "TypeComplexityPass"
1331 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1334 cx: &LateContext<'a, 'tcx>,
1341 self.check_fndecl(cx, decl);
1344 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1345 // enum variants are also struct fields now
1346 self.check_type(cx, &field.ty);
1349 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1351 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1352 // functions, enums, structs, impls and traits are covered
1357 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1359 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1360 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1361 // methods with default impl are covered by check_fn
1366 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1368 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1369 // methods are covered by check_fn
1374 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1375 if let Some(ref ty) = local.ty {
1376 self.check_type(cx, ty);
1381 impl<'a, 'tcx> TypeComplexityPass {
1382 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1383 for arg in &decl.inputs {
1384 self.check_type(cx, arg);
1386 if let Return(ref ty) = decl.output {
1387 self.check_type(cx, ty);
1391 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1392 if in_macro(ty.span) {
1396 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1397 visitor.visit_ty(ty);
1401 if score > self.threshold {
1406 "very complex type used. Consider factoring parts into `type` definitions",
1412 /// Walks a type and assigns a complexity score to it.
1413 struct TypeComplexityVisitor {
1414 /// total complexity score of the type
1416 /// current nesting level
1420 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1421 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1422 let (add_score, sub_nest) = match ty.node {
1423 // _, &x and *x have only small overhead; don't mess with nesting level
1424 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1426 // the "normal" components of a type: named types, arrays/tuples
1427 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1429 // function types bring a lot of overhead
1430 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1432 TyKind::TraitObject(ref param_bounds, _) => {
1433 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1434 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1435 GenericParamKind::Lifetime { .. } => true,
1439 if has_lifetime_parameters {
1440 // complex trait bounds like A<'a, 'b>
1443 // simple trait bounds like A + B
1450 self.score += add_score;
1451 self.nest += sub_nest;
1453 self.nest -= sub_nest;
1455 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1456 NestedVisitorMap::None
1460 /// **What it does:** Checks for expressions where a character literal is cast
1461 /// to `u8` and suggests using a byte literal instead.
1463 /// **Why is this bad?** In general, casting values to smaller types is
1464 /// error-prone and should be avoided where possible. In the particular case of
1465 /// converting a character literal to u8, it is easy to avoid by just using a
1466 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1467 /// than `'a' as u8`.
1469 /// **Known problems:** None.
1476 /// A better version, using the byte literal:
1481 declare_clippy_lint! {
1484 "casting a character literal to u8"
1487 pub struct CharLitAsU8;
1489 impl LintPass for CharLitAsU8 {
1490 fn get_lints(&self) -> LintArray {
1491 lint_array!(CHAR_LIT_AS_U8)
1494 fn name(&self) -> &'static str {
1499 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1500 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1501 use syntax::ast::{LitKind, UintTy};
1503 if let ExprKind::Cast(ref e, _) = expr.node {
1504 if let ExprKind::Lit(ref l) = e.node {
1505 if let LitKind::Char(_) = l.node {
1506 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1507 let msg = "casting character literal to u8. `char`s \
1508 are 4 bytes wide in rust, so casting to u8 \
1511 "Consider using a byte literal instead:\nb{}",
1512 snippet(cx, e.span, "'x'")
1514 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1522 /// **What it does:** Checks for comparisons where one side of the relation is
1523 /// either the minimum or maximum value for its type and warns if it involves a
1524 /// case that is always true or always false. Only integer and boolean types are
1527 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1528 /// that is is possible for `x` to be less than the minimum. Expressions like
1529 /// `max < x` are probably mistakes.
1531 /// **Known problems:** For `usize` the size of the current compile target will
1532 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1533 /// a comparison to detect target pointer width will trigger this lint. One can
1534 /// use `mem::sizeof` and compare its value or conditional compilation
1536 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1541 /// 100 > std::i32::MAX
1543 declare_clippy_lint! {
1544 pub ABSURD_EXTREME_COMPARISONS,
1546 "a comparison with a maximum or minimum value that is always true or false"
1549 pub struct AbsurdExtremeComparisons;
1551 impl LintPass for AbsurdExtremeComparisons {
1552 fn get_lints(&self) -> LintArray {
1553 lint_array!(ABSURD_EXTREME_COMPARISONS)
1556 fn name(&self) -> &'static str {
1557 "AbsurdExtremeComparisons"
1566 struct ExtremeExpr<'a> {
1571 enum AbsurdComparisonResult {
1574 InequalityImpossible,
1577 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1578 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1579 let precast_ty = cx.tables.expr_ty(cast_exp);
1580 let cast_ty = cx.tables.expr_ty(expr);
1582 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1588 fn detect_absurd_comparison<'a, 'tcx>(
1589 cx: &LateContext<'a, 'tcx>,
1593 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1594 use crate::types::AbsurdComparisonResult::*;
1595 use crate::types::ExtremeType::*;
1596 use crate::utils::comparisons::*;
1598 // absurd comparison only makes sense on primitive types
1599 // primitive types don't implement comparison operators with each other
1600 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1604 // comparisons between fix sized types and target sized types are considered unanalyzable
1605 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1609 let normalized = normalize_comparison(op, lhs, rhs);
1610 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1616 let lx = detect_extreme_expr(cx, normalized_lhs);
1617 let rx = detect_extreme_expr(cx, normalized_rhs);
1622 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1623 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1629 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1630 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1631 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1632 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1636 Rel::Ne | Rel::Eq => return None,
1640 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1641 use crate::types::ExtremeType::*;
1643 let ty = cx.tables.expr_ty(expr);
1645 let cv = constant(cx, cx.tables, expr)?.0;
1647 let which = match (&ty.sty, cv) {
1648 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1649 (&ty::Int(ity), Constant::Int(i))
1650 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1655 (&ty::Bool, Constant::Bool(true)) => Maximum,
1656 (&ty::Int(ity), Constant::Int(i))
1657 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1661 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1665 Some(ExtremeExpr { which, expr })
1668 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1669 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1670 use crate::types::AbsurdComparisonResult::*;
1671 use crate::types::ExtremeType::*;
1673 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1674 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1675 if !in_macro(expr.span) {
1676 let msg = "this comparison involving the minimum or maximum element for this \
1677 type contains a case that is always true or always false";
1679 let conclusion = match result {
1680 AlwaysFalse => "this comparison is always false".to_owned(),
1681 AlwaysTrue => "this comparison is always true".to_owned(),
1682 InequalityImpossible => format!(
1683 "the case where the two sides are not equal never occurs, consider using {} == {} \
1685 snippet(cx, lhs.span, "lhs"),
1686 snippet(cx, rhs.span, "rhs")
1691 "because {} is the {} value for this type, {}",
1692 snippet(cx, culprit.expr.span, "x"),
1693 match culprit.which {
1694 Minimum => "minimum",
1695 Maximum => "maximum",
1700 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1707 /// **What it does:** Checks for comparisons where the relation is always either
1708 /// true or false, but where one side has been upcast so that the comparison is
1709 /// necessary. Only integer types are checked.
1711 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1712 /// will mistakenly imply that it is possible for `x` to be outside the range of
1715 /// **Known problems:**
1716 /// https://github.com/rust-lang/rust-clippy/issues/886
1720 /// let x : u8 = ...; (x as u32) > 300
1722 declare_clippy_lint! {
1723 pub INVALID_UPCAST_COMPARISONS,
1725 "a comparison involving an upcast which is always true or false"
1728 pub struct InvalidUpcastComparisons;
1730 impl LintPass for InvalidUpcastComparisons {
1731 fn get_lints(&self) -> LintArray {
1732 lint_array!(INVALID_UPCAST_COMPARISONS)
1735 fn name(&self) -> &'static str {
1736 "InvalidUpcastComparisons"
1740 #[derive(Copy, Clone, Debug, Eq)]
1747 #[allow(clippy::cast_sign_loss)]
1748 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1751 } else if u > (i128::max_value() as u128) {
1759 impl PartialEq for FullInt {
1760 fn eq(&self, other: &Self) -> bool {
1761 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1765 impl PartialOrd for FullInt {
1766 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1767 Some(match (self, other) {
1768 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1769 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1770 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1771 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1775 impl Ord for FullInt {
1776 fn cmp(&self, other: &Self) -> Ordering {
1777 self.partial_cmp(other)
1778 .expect("partial_cmp for FullInt can never return None")
1782 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1784 use syntax::ast::{IntTy, UintTy};
1786 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1787 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1788 let cast_ty = cx.tables.expr_ty(expr);
1789 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1790 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1793 match pre_cast_ty.sty {
1794 ty::Int(int_ty) => Some(match int_ty {
1796 FullInt::S(i128::from(i8::min_value())),
1797 FullInt::S(i128::from(i8::max_value())),
1800 FullInt::S(i128::from(i16::min_value())),
1801 FullInt::S(i128::from(i16::max_value())),
1804 FullInt::S(i128::from(i32::min_value())),
1805 FullInt::S(i128::from(i32::max_value())),
1808 FullInt::S(i128::from(i64::min_value())),
1809 FullInt::S(i128::from(i64::max_value())),
1811 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1813 FullInt::S(isize::min_value() as i128),
1814 FullInt::S(isize::max_value() as i128),
1817 ty::Uint(uint_ty) => Some(match uint_ty {
1819 FullInt::U(u128::from(u8::min_value())),
1820 FullInt::U(u128::from(u8::max_value())),
1823 FullInt::U(u128::from(u16::min_value())),
1824 FullInt::U(u128::from(u16::max_value())),
1827 FullInt::U(u128::from(u32::min_value())),
1828 FullInt::U(u128::from(u32::max_value())),
1831 FullInt::U(u128::from(u64::min_value())),
1832 FullInt::U(u128::from(u64::max_value())),
1834 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1836 FullInt::U(usize::min_value() as u128),
1837 FullInt::U(usize::max_value() as u128),
1847 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1848 let val = constant(cx, cx.tables, expr)?.0;
1849 if let Constant::Int(const_int) = val {
1850 match cx.tables.expr_ty(expr).sty {
1851 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1852 ty::Uint(_) => Some(FullInt::U(const_int)),
1860 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1861 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1864 INVALID_UPCAST_COMPARISONS,
1867 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1868 snippet(cx, cast_val.span, "the expression"),
1869 if always { "true" } else { "false" },
1875 fn upcast_comparison_bounds_err<'a, 'tcx>(
1876 cx: &LateContext<'a, 'tcx>,
1878 rel: comparisons::Rel,
1879 lhs_bounds: Option<(FullInt, FullInt)>,
1884 use crate::utils::comparisons::*;
1886 if let Some((lb, ub)) = lhs_bounds {
1887 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1888 if rel == Rel::Eq || rel == Rel::Ne {
1889 if norm_rhs_val < lb || norm_rhs_val > ub {
1890 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1892 } else if match rel {
1907 Rel::Eq | Rel::Ne => unreachable!(),
1909 err_upcast_comparison(cx, span, lhs, true)
1910 } else if match rel {
1925 Rel::Eq | Rel::Ne => unreachable!(),
1927 err_upcast_comparison(cx, span, lhs, false)
1933 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1934 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1935 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1936 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1937 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1943 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1944 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1946 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1947 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1952 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1953 /// over different hashers and implicitly defaulting to the default hashing
1954 /// algorithm (SipHash).
1956 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1959 /// **Known problems:** Suggestions for replacing constructors can contain
1960 /// false-positives. Also applying suggestions can require modification of other
1961 /// pieces of code, possibly including external crates.
1965 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1967 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1969 declare_clippy_lint! {
1970 pub IMPLICIT_HASHER,
1972 "missing generalization over different hashers"
1975 pub struct ImplicitHasher;
1977 impl LintPass for ImplicitHasher {
1978 fn get_lints(&self) -> LintArray {
1979 lint_array!(IMPLICIT_HASHER)
1982 fn name(&self) -> &'static str {
1987 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1988 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
1989 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1990 use syntax_pos::BytePos;
1992 fn suggestion<'a, 'tcx>(
1993 cx: &LateContext<'a, 'tcx>,
1994 db: &mut DiagnosticBuilder<'_>,
1995 generics_span: Span,
1996 generics_suggestion_span: Span,
1997 target: &ImplicitHasherType<'_>,
1998 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2000 let generics_snip = snippet(cx, generics_span, "");
2002 let generics_snip = if generics_snip.is_empty() {
2005 &generics_snip[1..generics_snip.len() - 1]
2010 "consider adding a type parameter".to_string(),
2013 generics_suggestion_span,
2015 "<{}{}S: ::std::hash::BuildHasher{}>",
2017 if generics_snip.is_empty() { "" } else { ", " },
2018 if vis.suggestions.is_empty() {
2021 // request users to add `Default` bound so that generic constructors can be used
2028 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2033 if !vis.suggestions.is_empty() {
2034 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2038 if !cx.access_levels.is_exported(item.id) {
2043 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2044 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2047 for target in &vis.found {
2048 if differing_macro_contexts(item.span, target.span()) {
2052 let generics_suggestion_span = generics.span.substitute_dummy({
2053 let pos = snippet_opt(cx, item.span.until(target.span()))
2054 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2055 if let Some(pos) = pos {
2056 Span::new(pos, pos, item.span.data().ctxt)
2062 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2063 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2064 ctr_vis.visit_impl_item(item);
2072 "impl for `{}` should be generalized over different hashers",
2076 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2081 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2082 let body = cx.tcx.hir().body(body_id);
2084 for ty in &decl.inputs {
2085 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2088 for target in &vis.found {
2089 let generics_suggestion_span = generics.span.substitute_dummy({
2090 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2092 let i = snip.find("fn")?;
2093 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2095 .expect("failed to create span for type parameters");
2096 Span::new(pos, pos, item.span.data().ctxt)
2099 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2100 ctr_vis.visit_body(body);
2107 "parameter of type `{}` should be generalized over different hashers",
2111 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2122 enum ImplicitHasherType<'tcx> {
2123 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2124 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2127 impl<'tcx> ImplicitHasherType<'tcx> {
2128 /// Checks that `ty` is a target type without a BuildHasher.
2129 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2130 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2131 let params: Vec<_> = path
2139 .filter_map(|arg| match arg {
2140 GenericArg::Type(ty) => Some(ty),
2141 GenericArg::Lifetime(_) => None,
2144 let params_len = params.len();
2146 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2148 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2149 Some(ImplicitHasherType::HashMap(
2152 snippet(cx, params[0].span, "K"),
2153 snippet(cx, params[1].span, "V"),
2155 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2156 Some(ImplicitHasherType::HashSet(
2159 snippet(cx, params[0].span, "T"),
2169 fn type_name(&self) -> &'static str {
2171 ImplicitHasherType::HashMap(..) => "HashMap",
2172 ImplicitHasherType::HashSet(..) => "HashSet",
2176 fn type_arguments(&self) -> String {
2178 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2179 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2183 fn ty(&self) -> Ty<'tcx> {
2185 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2189 fn span(&self) -> Span {
2191 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2196 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2197 cx: &'a LateContext<'a, 'tcx>,
2198 found: Vec<ImplicitHasherType<'tcx>>,
2201 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2202 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2203 Self { cx, found: vec![] }
2207 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2208 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2209 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2210 self.found.push(target);
2216 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2217 NestedVisitorMap::None
2221 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2222 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2223 cx: &'a LateContext<'a, 'tcx>,
2224 body: &'a TypeckTables<'tcx>,
2225 target: &'b ImplicitHasherType<'tcx>,
2226 suggestions: BTreeMap<Span, String>,
2229 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2230 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2235 suggestions: BTreeMap::new(),
2240 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2241 fn visit_body(&mut self, body: &'tcx Body) {
2242 let prev_body = self.body;
2243 self.body = self.cx.tcx.body_tables(body.id());
2244 walk_body(self, body);
2245 self.body = prev_body;
2248 fn visit_expr(&mut self, e: &'tcx Expr) {
2250 if let ExprKind::Call(ref fun, ref args) = e.node;
2251 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2252 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2254 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2258 if match_path(ty_path, &paths::HASHMAP) {
2259 if method.ident.name == "new" {
2261 .insert(e.span, "HashMap::default()".to_string());
2262 } else if method.ident.name == "with_capacity" {
2263 self.suggestions.insert(
2266 "HashMap::with_capacity_and_hasher({}, Default::default())",
2267 snippet(self.cx, args[0].span, "capacity"),
2271 } else if match_path(ty_path, &paths::HASHSET) {
2272 if method.ident.name == "new" {
2274 .insert(e.span, "HashSet::default()".to_string());
2275 } else if method.ident.name == "with_capacity" {
2276 self.suggestions.insert(
2279 "HashSet::with_capacity_and_hasher({}, Default::default())",
2280 snippet(self.cx, args[0].span, "capacity"),
2291 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2292 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2296 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2298 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2299 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2302 /// **Known problems:** None.
2308 /// *(r as *const _ as *mut _) += 1;
2313 /// Instead consider using interior mutability types.
2316 /// fn x(r: &UnsafeCell<i32>) {
2322 declare_clippy_lint! {
2323 pub CAST_REF_TO_MUT,
2325 "a cast of reference to a mutable pointer"
2328 pub struct RefToMut;
2330 impl LintPass for RefToMut {
2331 fn get_lints(&self) -> LintArray {
2332 lint_array!(CAST_REF_TO_MUT)
2335 fn name(&self) -> &'static str {
2340 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2341 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2343 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2344 if let ExprKind::Cast(e, t) = &e.node;
2345 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2346 if let ExprKind::Cast(e, t) = &e.node;
2347 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2348 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2354 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",