1 #![allow(clippy::default_hash_types)]
3 use crate::consts::{constant, Constant};
4 use crate::utils::paths;
6 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
7 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
8 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
11 use if_chain::if_chain;
13 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
15 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
16 use rustc::ty::layout::LayoutOf;
17 use rustc::ty::{self, Ty, TyCtxt, TypeckTables};
18 use rustc::{declare_tool_lint, lint_array};
19 use rustc_errors::Applicability;
20 use rustc_target::spec::abi::Abi;
21 use rustc_typeck::hir_ty_to_ty;
23 use std::cmp::Ordering;
24 use std::collections::BTreeMap;
25 use syntax::ast::{FloatTy, IntTy, UintTy};
26 use syntax::errors::DiagnosticBuilder;
27 use syntax::source_map::Span;
29 /// Handles all the linting of funky types
32 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
34 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
35 /// the heap. So if you `Box` it, you just add another level of indirection
36 /// without any benefit whatsoever.
38 /// **Known problems:** None.
43 /// values: Box<Vec<Foo>>,
54 declare_clippy_lint! {
57 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
60 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
62 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
63 /// the heap. So if you `Box` its contents, you just add another level of indirection.
65 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
71 /// values: Vec<Box<i32>>,
82 declare_clippy_lint! {
85 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
88 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
91 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
92 /// represents an optional optional value which is logically the same thing as an optional
93 /// value but has an unneeded extra level of wrapping.
95 /// **Known problems:** None.
99 /// fn x() -> Option<Option<u32>> {
102 declare_clippy_lint! {
105 "usage of `Option<Option<T>>`"
108 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
109 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
111 /// **Why is this bad?** Gankro says:
113 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
114 /// pointers and indirection.
115 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
117 /// > "only" amortized for push/pop, should be faster in the general case for
118 /// almost every possible
119 /// > workload, and isn't even amortized at all if you can predict the capacity
122 /// > `LinkedList`s are only really good if you're doing a lot of merging or
123 /// splitting of lists.
124 /// > This is because they can just mangle some pointers instead of actually
125 /// copying the data. Even
126 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
127 /// can still be better
128 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
130 /// **Known problems:** False positives – the instances where using a
131 /// `LinkedList` makes sense are few and far between, but they can still happen.
135 /// let x = LinkedList::new();
137 declare_clippy_lint! {
140 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
143 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
145 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
148 /// **Known problems:** None.
152 /// fn foo(bar: &Box<T>) { ... }
158 /// fn foo(bar: &T) { ... }
160 declare_clippy_lint! {
163 "a borrow of a boxed type"
166 impl LintPass for TypePass {
167 fn get_lints(&self) -> LintArray {
168 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
171 fn name(&self) -> &'static str {
176 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
177 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
178 // skip trait implementations, see #605
179 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find_by_hir_id(cx.tcx.hir().get_parent_item(id)) {
180 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
185 check_fn_decl(cx, decl);
188 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
189 check_ty(cx, &field.ty, false);
192 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
194 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
195 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
200 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
201 if let Some(ref ty) = local.ty {
202 check_ty(cx, ty, true);
207 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
208 for input in &decl.inputs {
209 check_ty(cx, input, false);
212 if let FunctionRetTy::Return(ref ty) = decl.output {
213 check_ty(cx, ty, false);
217 /// Check if `qpath` has last segment with type parameter matching `path`
218 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
219 let last = last_path_segment(qpath);
221 if let Some(ref params) = last.args;
222 if !params.parenthesized;
223 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
224 GenericArg::Type(ty) => Some(ty),
227 if let TyKind::Path(ref qpath) = ty.node;
228 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
229 if match_def_path(cx.tcx, did, path);
237 /// Recursively check for `TypePass` lints in the given type. Stop at the first
240 /// The parameter `is_local` distinguishes the context of the type; types from
241 /// local bindings should only be checked for the `BORROWED_BOX` lint.
242 #[allow(clippy::too_many_lines)]
243 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
244 if in_macro(hir_ty.span) {
248 TyKind::Path(ref qpath) if !is_local => {
249 let hir_id = cx.tcx.hir().node_to_hir_id(hir_ty.id);
250 let def = cx.tables.qpath_def(qpath, hir_id);
251 if let Some(def_id) = opt_def_id(def) {
252 if Some(def_id) == cx.tcx.lang_items().owned_box() {
253 if match_type_parameter(cx, qpath, &paths::VEC) {
258 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
259 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
261 return; // don't recurse into the type
263 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
265 // Get the _ part of Vec<_>
266 if let Some(ref last) = last_path_segment(qpath).args;
267 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
268 GenericArg::Type(ty) => Some(ty),
271 // ty is now _ at this point
272 if let TyKind::Path(ref ty_qpath) = ty.node;
273 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
274 if let Some(def_id) = opt_def_id(def);
275 if Some(def_id) == cx.tcx.lang_items().owned_box();
276 // At this point, we know ty is Box<T>, now get T
277 if let Some(ref last) = last_path_segment(ty_qpath).args;
278 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
279 GenericArg::Type(ty) => Some(ty),
283 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
284 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
289 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
291 format!("Vec<{}>", ty_ty),
292 Applicability::MachineApplicable,
294 return; // don't recurse into the type
298 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
299 if match_type_parameter(cx, qpath, &paths::OPTION) {
304 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
305 enum if you need to distinguish all 3 cases",
307 return; // don't recurse into the type
309 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
314 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
315 "a VecDeque might work",
317 return; // don't recurse into the type
321 QPath::Resolved(Some(ref ty), ref p) => {
322 check_ty(cx, ty, is_local);
323 for ty in p.segments.iter().flat_map(|seg| {
326 .map_or_else(|| [].iter(), |params| params.args.iter())
327 .filter_map(|arg| match arg {
328 GenericArg::Type(ty) => Some(ty),
332 check_ty(cx, ty, is_local);
335 QPath::Resolved(None, ref p) => {
336 for ty in p.segments.iter().flat_map(|seg| {
339 .map_or_else(|| [].iter(), |params| params.args.iter())
340 .filter_map(|arg| match arg {
341 GenericArg::Type(ty) => Some(ty),
345 check_ty(cx, ty, is_local);
348 QPath::TypeRelative(ref ty, ref seg) => {
349 check_ty(cx, ty, is_local);
350 if let Some(ref params) = seg.args {
351 for ty in params.args.iter().filter_map(|arg| match arg {
352 GenericArg::Type(ty) => Some(ty),
355 check_ty(cx, ty, is_local);
361 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
363 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
364 check_ty(cx, ty, is_local)
366 TyKind::Tup(ref tys) => {
368 check_ty(cx, ty, is_local);
375 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
376 match mut_ty.ty.node {
377 TyKind::Path(ref qpath) => {
378 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
379 let def = cx.tables.qpath_def(qpath, hir_id);
381 if let Some(def_id) = opt_def_id(def);
382 if Some(def_id) == cx.tcx.lang_items().owned_box();
383 if let QPath::Resolved(None, ref path) = *qpath;
384 if let [ref bx] = *path.segments;
385 if let Some(ref params) = bx.args;
386 if !params.parenthesized;
387 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
388 GenericArg::Type(ty) => Some(ty),
392 if is_any_trait(inner) {
393 // Ignore `Box<Any>` types, see #1884 for details.
397 let ltopt = if lt.is_elided() {
400 format!("{} ", lt.name.ident().as_str())
402 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
407 let mut applicability = Applicability::MachineApplicable;
412 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
418 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
420 Applicability::Unspecified,
422 return; // don't recurse into the type
425 check_ty(cx, &mut_ty.ty, is_local);
427 _ => check_ty(cx, &mut_ty.ty, is_local),
431 // Returns true if given type is `Any` trait.
432 fn is_any_trait(t: &hir::Ty) -> bool {
434 if let TyKind::TraitObject(ref traits, _) = t.node;
435 if traits.len() >= 1;
436 // Only Send/Sync can be used as additional traits, so it is enough to
437 // check only the first trait.
438 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
449 /// **What it does:** Checks for binding a unit value.
451 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
452 /// binding one is kind of pointless.
454 /// **Known problems:** None.
462 declare_clippy_lint! {
465 "creating a let binding to a value of unit type, which usually can't be used afterwards"
468 impl LintPass for LetPass {
469 fn get_lints(&self) -> LintArray {
470 lint_array!(LET_UNIT_VALUE)
473 fn name(&self) -> &'static str {
478 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
479 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
480 if let StmtKind::Local(ref local) = stmt.node {
481 if is_unit(cx.tables.pat_ty(&local.pat)) {
482 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
485 if higher::is_from_for_desugar(local) {
493 "this let-binding has unit value. Consider omitting `let {} =`",
494 snippet(cx, local.pat.span, "..")
502 /// **What it does:** Checks for comparisons to unit.
504 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
505 /// clumsily written constant. Mostly this happens when someone accidentally
506 /// adds semicolons at the end of the operands.
508 /// **Known problems:** None.
528 declare_clippy_lint! {
531 "comparing unit values"
536 impl LintPass for UnitCmp {
537 fn get_lints(&self) -> LintArray {
538 lint_array!(UNIT_CMP)
541 fn name(&self) -> &'static str {
546 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
547 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
548 if in_macro(expr.span) {
551 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
553 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
554 let result = match op {
555 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
563 "{}-comparison of unit values detected. This will always be {}",
573 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
574 /// unit literal (`()`).
576 /// **Why is this bad?** This is likely the result of an accidental semicolon.
578 /// **Known problems:** None.
587 declare_clippy_lint! {
590 "passing unit to a function"
595 impl LintPass for UnitArg {
596 fn get_lints(&self) -> LintArray {
597 lint_array!(UNIT_ARG)
600 fn name(&self) -> &'static str {
605 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
606 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
607 if in_macro(expr.span) {
611 // apparently stuff in the desugaring of `?` can trigger this
612 // so check for that here
613 // only the calls to `Try::from_error` is marked as desugared,
614 // so we need to check both the current Expr and its parent.
615 if is_questionmark_desugar_marked_call(expr) {
619 let map = &cx.tcx.hir();
620 let opt_parent_node = map.find(map.get_parent_node(expr.id));
621 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
622 if is_questionmark_desugar_marked_call(parent_expr);
629 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
631 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
632 if let ExprKind::Match(.., match_source) = &arg.node {
633 if *match_source == MatchSource::TryDesugar {
642 "passing a unit value to a function",
643 "if you intended to pass a unit value, use a unit literal instead",
645 Applicability::MachineApplicable,
655 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
656 use syntax_pos::hygiene::CompilerDesugaringKind;
657 if let ExprKind::Call(ref callee, _) = expr.node {
658 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
664 fn is_unit(ty: Ty<'_>) -> bool {
666 ty::Tuple(slice) if slice.is_empty() => true,
671 fn is_unit_literal(expr: &Expr) -> bool {
673 ExprKind::Tup(ref slice) if slice.is_empty() => true,
680 /// **What it does:** Checks for casts from any numerical to a float type where
681 /// the receiving type cannot store all values from the original type without
682 /// rounding errors. This possible rounding is to be expected, so this lint is
683 /// `Allow` by default.
685 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
686 /// or any 64-bit integer to `f64`.
688 /// **Why is this bad?** It's not bad at all. But in some applications it can be
689 /// helpful to know where precision loss can take place. This lint can help find
690 /// those places in the code.
692 /// **Known problems:** None.
696 /// let x = u64::MAX;
699 declare_clippy_lint! {
700 pub CAST_PRECISION_LOSS,
702 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
705 /// **What it does:** Checks for casts from a signed to an unsigned numerical
706 /// type. In this case, negative values wrap around to large positive values,
707 /// which can be quite surprising in practice. However, as the cast works as
708 /// defined, this lint is `Allow` by default.
710 /// **Why is this bad?** Possibly surprising results. You can activate this lint
711 /// as a one-time check to see where numerical wrapping can arise.
713 /// **Known problems:** None.
718 /// y as u128 // will return 18446744073709551615
720 declare_clippy_lint! {
723 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
726 /// **What it does:** Checks for on casts between numerical types that may
727 /// truncate large values. This is expected behavior, so the cast is `Allow` by
730 /// **Why is this bad?** In some problem domains, it is good practice to avoid
731 /// truncation. This lint can be activated to help assess where additional
732 /// checks could be beneficial.
734 /// **Known problems:** None.
738 /// fn as_u8(x: u64) -> u8 {
742 declare_clippy_lint! {
743 pub CAST_POSSIBLE_TRUNCATION,
745 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
748 /// **What it does:** Checks for casts from an unsigned type to a signed type of
749 /// the same size. Performing such a cast is a 'no-op' for the compiler,
750 /// i.e. nothing is changed at the bit level, and the binary representation of
751 /// the value is reinterpreted. This can cause wrapping if the value is too big
752 /// for the target signed type. However, the cast works as defined, so this lint
753 /// is `Allow` by default.
755 /// **Why is this bad?** While such a cast is not bad in itself, the results can
756 /// be surprising when this is not the intended behavior, as demonstrated by the
759 /// **Known problems:** None.
763 /// u32::MAX as i32 // will yield a value of `-1`
765 declare_clippy_lint! {
766 pub CAST_POSSIBLE_WRAP,
768 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
771 /// **What it does:** Checks for on casts between numerical types that may
772 /// be replaced by safe conversion functions.
774 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
775 /// conversions, including silently lossy conversions. Conversion functions such
776 /// as `i32::from` will only perform lossless conversions. Using the conversion
777 /// functions prevents conversions from turning into silent lossy conversions if
778 /// the types of the input expressions ever change, and make it easier for
779 /// people reading the code to know that the conversion is lossless.
781 /// **Known problems:** None.
785 /// fn as_u64(x: u8) -> u64 {
790 /// Using `::from` would look like this:
793 /// fn as_u64(x: u8) -> u64 {
797 declare_clippy_lint! {
800 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
803 /// **What it does:** Checks for casts to the same type.
805 /// **Why is this bad?** It's just unnecessary.
807 /// **Known problems:** None.
811 /// let _ = 2i32 as i32
813 declare_clippy_lint! {
814 pub UNNECESSARY_CAST,
816 "cast to the same type, e.g. `x as i32` where `x: i32`"
819 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
820 /// more-strictly-aligned pointer
822 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
825 /// **Known problems:** None.
829 /// let _ = (&1u8 as *const u8) as *const u16;
830 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
832 declare_clippy_lint! {
833 pub CAST_PTR_ALIGNMENT,
835 "cast from a pointer to a more-strictly-aligned pointer"
838 /// **What it does:** Checks for casts of function pointers to something other than usize
840 /// **Why is this bad?**
841 /// Casting a function pointer to anything other than usize/isize is not portable across
842 /// architectures, because you end up losing bits if the target type is too small or end up with a
843 /// bunch of extra bits that waste space and add more instructions to the final binary than
844 /// strictly necessary for the problem
846 /// Casting to isize also doesn't make sense since there are no signed addresses.
852 /// fn fun() -> i32 {}
853 /// let a = fun as i64;
856 /// fn fun2() -> i32 {}
857 /// let a = fun2 as usize;
859 declare_clippy_lint! {
860 pub FN_TO_NUMERIC_CAST,
862 "casting a function pointer to a numeric type other than usize"
865 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
868 /// **Why is this bad?**
869 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
870 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
871 /// a comment) to perform the truncation.
877 /// fn fn1() -> i16 {
880 /// let _ = fn1 as i32;
882 /// // Better: Cast to usize first, then comment with the reason for the truncation
883 /// fn fn2() -> i16 {
886 /// let fn_ptr = fn2 as usize;
887 /// let fn_ptr_truncated = fn_ptr as i32;
889 declare_clippy_lint! {
890 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
892 "casting a function pointer to a numeric type not wide enough to store the address"
895 /// Returns the size in bits of an integral type.
896 /// Will return 0 if the type is not an int or uint variant
897 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
899 ty::Int(i) => match i {
900 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
907 ty::Uint(i) => match i {
908 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
919 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
921 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
926 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
927 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
928 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
929 let arch_dependent_str = "on targets with 64-bit wide pointers ";
930 let from_nbits_str = if arch_dependent {
932 } else if is_isize_or_usize(cast_from) {
933 "32 or 64".to_owned()
935 int_ty_to_nbits(cast_from, cx.tcx).to_string()
942 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
943 is only {4} bits wide)",
945 if cast_to_f64 { "f64" } else { "f32" },
946 if arch_dependent { arch_dependent_str } else { "" },
953 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
954 if let ExprKind::Binary(_, _, _) = op.node {
955 if snip.starts_with('(') && snip.ends_with(')') {
962 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
963 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
964 if in_constant(cx, expr.id) {
967 // The suggestion is to use a function call, so if the original expression
968 // has parens on the outside, they are no longer needed.
969 let mut applicability = Applicability::MachineApplicable;
970 let opt = snippet_opt(cx, op.span);
971 let sugg = if let Some(ref snip) = opt {
972 if should_strip_parens(op, snip) {
973 &snip[1..snip.len() - 1]
978 applicability = Applicability::HasPlaceholders;
987 "casting {} to {} may become silently lossy if types change",
991 format!("{}::from({})", cast_to, sugg),
1002 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1003 if !cast_from.is_signed() || cast_to.is_signed() {
1007 // don't lint for positive constants
1008 let const_val = constant(cx, &cx.tables, op);
1010 if let Some((const_val, _)) = const_val;
1011 if let Constant::Int(n) = const_val;
1012 if let ty::Int(ity) = cast_from.sty;
1013 if sext(cx.tcx, n, ity) >= 0;
1023 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1027 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1028 let arch_64_suffix = " on targets with 64-bit wide pointers";
1029 let arch_32_suffix = " on targets with 32-bit wide pointers";
1030 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1031 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1032 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1033 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1034 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1035 (true, true) | (false, false) => (
1036 to_nbits < from_nbits,
1038 to_nbits == from_nbits && cast_unsigned_to_signed,
1048 to_nbits <= 32 && cast_unsigned_to_signed,
1054 cast_unsigned_to_signed,
1055 if from_nbits == 64 {
1062 if span_truncation {
1065 CAST_POSSIBLE_TRUNCATION,
1068 "casting {} to {} may truncate the value{}",
1071 match suffix_truncation {
1072 ArchSuffix::_32 => arch_32_suffix,
1073 ArchSuffix::_64 => arch_64_suffix,
1074 ArchSuffix::None => "",
1085 "casting {} to {} may wrap around the value{}",
1089 ArchSuffix::_32 => arch_32_suffix,
1090 ArchSuffix::_64 => arch_64_suffix,
1091 ArchSuffix::None => "",
1098 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1099 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1100 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1101 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1102 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1104 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1108 impl LintPass for CastPass {
1109 fn get_lints(&self) -> LintArray {
1111 CAST_PRECISION_LOSS,
1113 CAST_POSSIBLE_TRUNCATION,
1119 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1123 fn name(&self) -> &'static str {
1128 // Check if the given type is either `core::ffi::c_void` or
1129 // one of the platform specific `libc::<platform>::c_void` of libc.
1130 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1131 if let ty::Adt(adt, _) = ty.sty {
1132 let mut apb = AbsolutePathBuffer { names: vec![] };
1133 tcx.push_item_path(&mut apb, adt.did, false);
1135 if apb.names.is_empty() {
1138 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1145 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1146 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1147 if let ExprKind::Cast(ref ex, _) = expr.node {
1148 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1149 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1150 if let ExprKind::Lit(ref lit) = ex.node {
1151 use syntax::ast::{LitIntType, LitKind};
1153 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1155 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1161 "casting to the same type is unnecessary (`{}` -> `{}`)",
1169 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1170 match (cast_from.is_integral(), cast_to.is_integral()) {
1172 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1173 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1178 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1179 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1181 if from_nbits < to_nbits {
1182 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1188 CAST_POSSIBLE_TRUNCATION,
1190 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1192 if !cast_to.is_signed() {
1197 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1202 check_loss_of_sign(cx, expr, ex, cast_from, cast_to);
1203 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1204 check_lossless(cx, expr, ex, cast_from, cast_to);
1207 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1210 CAST_POSSIBLE_TRUNCATION,
1212 "casting f64 to f32 may truncate the value",
1215 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1216 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1223 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1224 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1225 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1226 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1227 if from_align < to_align;
1228 // with c_void, we inherently need to trust the user
1229 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1235 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1243 fn lint_fn_to_numeric_cast(
1244 cx: &LateContext<'_, '_>,
1250 // We only want to check casts to `ty::Uint` or `ty::Int`
1252 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1255 match cast_from.sty {
1256 ty::FnDef(..) | ty::FnPtr(_) => {
1257 let mut applicability = Applicability::MachineApplicable;
1258 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1260 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1261 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1264 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1267 "casting function pointer `{}` to `{}`, which truncates the value",
1268 from_snippet, cast_to
1271 format!("{} as usize", from_snippet),
1274 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1279 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1281 format!("{} as usize", from_snippet),
1290 /// **What it does:** Checks for types used in structs, parameters and `let`
1291 /// declarations above a certain complexity threshold.
1293 /// **Why is this bad?** Too complex types make the code less readable. Consider
1294 /// using a `type` definition to simplify them.
1296 /// **Known problems:** None.
1301 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1304 declare_clippy_lint! {
1305 pub TYPE_COMPLEXITY,
1307 "usage of very complex types that might be better factored into `type` definitions"
1310 pub struct TypeComplexityPass {
1314 impl TypeComplexityPass {
1315 pub fn new(threshold: u64) -> Self {
1320 impl LintPass for TypeComplexityPass {
1321 fn get_lints(&self) -> LintArray {
1322 lint_array!(TYPE_COMPLEXITY)
1325 fn name(&self) -> &'static str {
1326 "TypeComplexityPass"
1330 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1333 cx: &LateContext<'a, 'tcx>,
1340 self.check_fndecl(cx, decl);
1343 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1344 // enum variants are also struct fields now
1345 self.check_type(cx, &field.ty);
1348 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1350 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1351 // functions, enums, structs, impls and traits are covered
1356 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1358 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1359 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1360 // methods with default impl are covered by check_fn
1365 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1367 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1368 // methods are covered by check_fn
1373 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1374 if let Some(ref ty) = local.ty {
1375 self.check_type(cx, ty);
1380 impl<'a, 'tcx> TypeComplexityPass {
1381 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1382 for arg in &decl.inputs {
1383 self.check_type(cx, arg);
1385 if let Return(ref ty) = decl.output {
1386 self.check_type(cx, ty);
1390 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1391 if in_macro(ty.span) {
1395 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1396 visitor.visit_ty(ty);
1400 if score > self.threshold {
1405 "very complex type used. Consider factoring parts into `type` definitions",
1411 /// Walks a type and assigns a complexity score to it.
1412 struct TypeComplexityVisitor {
1413 /// total complexity score of the type
1415 /// current nesting level
1419 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1420 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1421 let (add_score, sub_nest) = match ty.node {
1422 // _, &x and *x have only small overhead; don't mess with nesting level
1423 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1425 // the "normal" components of a type: named types, arrays/tuples
1426 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1428 // function types bring a lot of overhead
1429 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1431 TyKind::TraitObject(ref param_bounds, _) => {
1432 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1433 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1434 GenericParamKind::Lifetime { .. } => true,
1438 if has_lifetime_parameters {
1439 // complex trait bounds like A<'a, 'b>
1442 // simple trait bounds like A + B
1449 self.score += add_score;
1450 self.nest += sub_nest;
1452 self.nest -= sub_nest;
1454 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1455 NestedVisitorMap::None
1459 /// **What it does:** Checks for expressions where a character literal is cast
1460 /// to `u8` and suggests using a byte literal instead.
1462 /// **Why is this bad?** In general, casting values to smaller types is
1463 /// error-prone and should be avoided where possible. In the particular case of
1464 /// converting a character literal to u8, it is easy to avoid by just using a
1465 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1466 /// than `'a' as u8`.
1468 /// **Known problems:** None.
1475 /// A better version, using the byte literal:
1480 declare_clippy_lint! {
1483 "casting a character literal to u8"
1486 pub struct CharLitAsU8;
1488 impl LintPass for CharLitAsU8 {
1489 fn get_lints(&self) -> LintArray {
1490 lint_array!(CHAR_LIT_AS_U8)
1493 fn name(&self) -> &'static str {
1498 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1499 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1500 use syntax::ast::{LitKind, UintTy};
1502 if let ExprKind::Cast(ref e, _) = expr.node {
1503 if let ExprKind::Lit(ref l) = e.node {
1504 if let LitKind::Char(_) = l.node {
1505 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1506 let msg = "casting character literal to u8. `char`s \
1507 are 4 bytes wide in rust, so casting to u8 \
1510 "Consider using a byte literal instead:\nb{}",
1511 snippet(cx, e.span, "'x'")
1513 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1521 /// **What it does:** Checks for comparisons where one side of the relation is
1522 /// either the minimum or maximum value for its type and warns if it involves a
1523 /// case that is always true or always false. Only integer and boolean types are
1526 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1527 /// that is is possible for `x` to be less than the minimum. Expressions like
1528 /// `max < x` are probably mistakes.
1530 /// **Known problems:** For `usize` the size of the current compile target will
1531 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1532 /// a comparison to detect target pointer width will trigger this lint. One can
1533 /// use `mem::sizeof` and compare its value or conditional compilation
1535 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1540 /// 100 > std::i32::MAX
1542 declare_clippy_lint! {
1543 pub ABSURD_EXTREME_COMPARISONS,
1545 "a comparison with a maximum or minimum value that is always true or false"
1548 pub struct AbsurdExtremeComparisons;
1550 impl LintPass for AbsurdExtremeComparisons {
1551 fn get_lints(&self) -> LintArray {
1552 lint_array!(ABSURD_EXTREME_COMPARISONS)
1555 fn name(&self) -> &'static str {
1556 "AbsurdExtremeComparisons"
1565 struct ExtremeExpr<'a> {
1570 enum AbsurdComparisonResult {
1573 InequalityImpossible,
1576 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1577 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1578 let precast_ty = cx.tables.expr_ty(cast_exp);
1579 let cast_ty = cx.tables.expr_ty(expr);
1581 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1587 fn detect_absurd_comparison<'a, 'tcx>(
1588 cx: &LateContext<'a, 'tcx>,
1592 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1593 use crate::types::AbsurdComparisonResult::*;
1594 use crate::types::ExtremeType::*;
1595 use crate::utils::comparisons::*;
1597 // absurd comparison only makes sense on primitive types
1598 // primitive types don't implement comparison operators with each other
1599 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1603 // comparisons between fix sized types and target sized types are considered unanalyzable
1604 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1608 let normalized = normalize_comparison(op, lhs, rhs);
1609 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1615 let lx = detect_extreme_expr(cx, normalized_lhs);
1616 let rx = detect_extreme_expr(cx, normalized_rhs);
1621 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1622 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1628 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1629 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1630 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1631 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1635 Rel::Ne | Rel::Eq => return None,
1639 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1640 use crate::types::ExtremeType::*;
1642 let ty = cx.tables.expr_ty(expr);
1644 let cv = constant(cx, cx.tables, expr)?.0;
1646 let which = match (&ty.sty, cv) {
1647 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1648 (&ty::Int(ity), Constant::Int(i))
1649 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1654 (&ty::Bool, Constant::Bool(true)) => Maximum,
1655 (&ty::Int(ity), Constant::Int(i))
1656 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1660 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1664 Some(ExtremeExpr { which, expr })
1667 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1668 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1669 use crate::types::AbsurdComparisonResult::*;
1670 use crate::types::ExtremeType::*;
1672 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1673 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1674 if !in_macro(expr.span) {
1675 let msg = "this comparison involving the minimum or maximum element for this \
1676 type contains a case that is always true or always false";
1678 let conclusion = match result {
1679 AlwaysFalse => "this comparison is always false".to_owned(),
1680 AlwaysTrue => "this comparison is always true".to_owned(),
1681 InequalityImpossible => format!(
1682 "the case where the two sides are not equal never occurs, consider using {} == {} \
1684 snippet(cx, lhs.span, "lhs"),
1685 snippet(cx, rhs.span, "rhs")
1690 "because {} is the {} value for this type, {}",
1691 snippet(cx, culprit.expr.span, "x"),
1692 match culprit.which {
1693 Minimum => "minimum",
1694 Maximum => "maximum",
1699 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1706 /// **What it does:** Checks for comparisons where the relation is always either
1707 /// true or false, but where one side has been upcast so that the comparison is
1708 /// necessary. Only integer types are checked.
1710 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1711 /// will mistakenly imply that it is possible for `x` to be outside the range of
1714 /// **Known problems:**
1715 /// https://github.com/rust-lang/rust-clippy/issues/886
1719 /// let x : u8 = ...; (x as u32) > 300
1721 declare_clippy_lint! {
1722 pub INVALID_UPCAST_COMPARISONS,
1724 "a comparison involving an upcast which is always true or false"
1727 pub struct InvalidUpcastComparisons;
1729 impl LintPass for InvalidUpcastComparisons {
1730 fn get_lints(&self) -> LintArray {
1731 lint_array!(INVALID_UPCAST_COMPARISONS)
1734 fn name(&self) -> &'static str {
1735 "InvalidUpcastComparisons"
1739 #[derive(Copy, Clone, Debug, Eq)]
1746 #[allow(clippy::cast_sign_loss)]
1747 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1750 } else if u > (i128::max_value() as u128) {
1758 impl PartialEq for FullInt {
1759 fn eq(&self, other: &Self) -> bool {
1760 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1764 impl PartialOrd for FullInt {
1765 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1766 Some(match (self, other) {
1767 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1768 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1769 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1770 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1774 impl Ord for FullInt {
1775 fn cmp(&self, other: &Self) -> Ordering {
1776 self.partial_cmp(other)
1777 .expect("partial_cmp for FullInt can never return None")
1781 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1783 use syntax::ast::{IntTy, UintTy};
1785 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1786 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1787 let cast_ty = cx.tables.expr_ty(expr);
1788 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1789 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1792 match pre_cast_ty.sty {
1793 ty::Int(int_ty) => Some(match int_ty {
1795 FullInt::S(i128::from(i8::min_value())),
1796 FullInt::S(i128::from(i8::max_value())),
1799 FullInt::S(i128::from(i16::min_value())),
1800 FullInt::S(i128::from(i16::max_value())),
1803 FullInt::S(i128::from(i32::min_value())),
1804 FullInt::S(i128::from(i32::max_value())),
1807 FullInt::S(i128::from(i64::min_value())),
1808 FullInt::S(i128::from(i64::max_value())),
1810 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1812 FullInt::S(isize::min_value() as i128),
1813 FullInt::S(isize::max_value() as i128),
1816 ty::Uint(uint_ty) => Some(match uint_ty {
1818 FullInt::U(u128::from(u8::min_value())),
1819 FullInt::U(u128::from(u8::max_value())),
1822 FullInt::U(u128::from(u16::min_value())),
1823 FullInt::U(u128::from(u16::max_value())),
1826 FullInt::U(u128::from(u32::min_value())),
1827 FullInt::U(u128::from(u32::max_value())),
1830 FullInt::U(u128::from(u64::min_value())),
1831 FullInt::U(u128::from(u64::max_value())),
1833 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1835 FullInt::U(usize::min_value() as u128),
1836 FullInt::U(usize::max_value() as u128),
1846 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1847 let val = constant(cx, cx.tables, expr)?.0;
1848 if let Constant::Int(const_int) = val {
1849 match cx.tables.expr_ty(expr).sty {
1850 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1851 ty::Uint(_) => Some(FullInt::U(const_int)),
1859 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1860 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1863 INVALID_UPCAST_COMPARISONS,
1866 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1867 snippet(cx, cast_val.span, "the expression"),
1868 if always { "true" } else { "false" },
1874 fn upcast_comparison_bounds_err<'a, 'tcx>(
1875 cx: &LateContext<'a, 'tcx>,
1877 rel: comparisons::Rel,
1878 lhs_bounds: Option<(FullInt, FullInt)>,
1883 use crate::utils::comparisons::*;
1885 if let Some((lb, ub)) = lhs_bounds {
1886 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1887 if rel == Rel::Eq || rel == Rel::Ne {
1888 if norm_rhs_val < lb || norm_rhs_val > ub {
1889 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1891 } else if match rel {
1906 Rel::Eq | Rel::Ne => unreachable!(),
1908 err_upcast_comparison(cx, span, lhs, true)
1909 } else if match rel {
1924 Rel::Eq | Rel::Ne => unreachable!(),
1926 err_upcast_comparison(cx, span, lhs, false)
1932 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1933 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1934 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1935 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1936 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1942 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1943 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1945 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1946 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1951 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1952 /// over different hashers and implicitly defaulting to the default hashing
1953 /// algorithm (SipHash).
1955 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1958 /// **Known problems:** Suggestions for replacing constructors can contain
1959 /// false-positives. Also applying suggestions can require modification of other
1960 /// pieces of code, possibly including external crates.
1964 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1966 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1968 declare_clippy_lint! {
1969 pub IMPLICIT_HASHER,
1971 "missing generalization over different hashers"
1974 pub struct ImplicitHasher;
1976 impl LintPass for ImplicitHasher {
1977 fn get_lints(&self) -> LintArray {
1978 lint_array!(IMPLICIT_HASHER)
1981 fn name(&self) -> &'static str {
1986 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1987 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
1988 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1989 use syntax_pos::BytePos;
1991 fn suggestion<'a, 'tcx>(
1992 cx: &LateContext<'a, 'tcx>,
1993 db: &mut DiagnosticBuilder<'_>,
1994 generics_span: Span,
1995 generics_suggestion_span: Span,
1996 target: &ImplicitHasherType<'_>,
1997 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1999 let generics_snip = snippet(cx, generics_span, "");
2001 let generics_snip = if generics_snip.is_empty() {
2004 &generics_snip[1..generics_snip.len() - 1]
2009 "consider adding a type parameter".to_string(),
2012 generics_suggestion_span,
2014 "<{}{}S: ::std::hash::BuildHasher{}>",
2016 if generics_snip.is_empty() { "" } else { ", " },
2017 if vis.suggestions.is_empty() {
2020 // request users to add `Default` bound so that generic constructors can be used
2027 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2032 if !vis.suggestions.is_empty() {
2033 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2037 if !cx.access_levels.is_exported(item.id) {
2042 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2043 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2046 for target in &vis.found {
2047 if differing_macro_contexts(item.span, target.span()) {
2051 let generics_suggestion_span = generics.span.substitute_dummy({
2052 let pos = snippet_opt(cx, item.span.until(target.span()))
2053 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2054 if let Some(pos) = pos {
2055 Span::new(pos, pos, item.span.data().ctxt)
2061 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2062 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2063 ctr_vis.visit_impl_item(item);
2071 "impl for `{}` should be generalized over different hashers",
2075 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2080 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2081 let body = cx.tcx.hir().body(body_id);
2083 for ty in &decl.inputs {
2084 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2087 for target in &vis.found {
2088 let generics_suggestion_span = generics.span.substitute_dummy({
2089 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2091 let i = snip.find("fn")?;
2092 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2094 .expect("failed to create span for type parameters");
2095 Span::new(pos, pos, item.span.data().ctxt)
2098 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2099 ctr_vis.visit_body(body);
2106 "parameter of type `{}` should be generalized over different hashers",
2110 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2121 enum ImplicitHasherType<'tcx> {
2122 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2123 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2126 impl<'tcx> ImplicitHasherType<'tcx> {
2127 /// Checks that `ty` is a target type without a BuildHasher.
2128 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2129 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2130 let params: Vec<_> = path
2138 .filter_map(|arg| match arg {
2139 GenericArg::Type(ty) => Some(ty),
2143 let params_len = params.len();
2145 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2147 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2148 Some(ImplicitHasherType::HashMap(
2151 snippet(cx, params[0].span, "K"),
2152 snippet(cx, params[1].span, "V"),
2154 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2155 Some(ImplicitHasherType::HashSet(
2158 snippet(cx, params[0].span, "T"),
2168 fn type_name(&self) -> &'static str {
2170 ImplicitHasherType::HashMap(..) => "HashMap",
2171 ImplicitHasherType::HashSet(..) => "HashSet",
2175 fn type_arguments(&self) -> String {
2177 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2178 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2182 fn ty(&self) -> Ty<'tcx> {
2184 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2188 fn span(&self) -> Span {
2190 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2195 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2196 cx: &'a LateContext<'a, 'tcx>,
2197 found: Vec<ImplicitHasherType<'tcx>>,
2200 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2201 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2202 Self { cx, found: vec![] }
2206 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2207 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2208 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2209 self.found.push(target);
2215 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2216 NestedVisitorMap::None
2220 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2221 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2222 cx: &'a LateContext<'a, 'tcx>,
2223 body: &'a TypeckTables<'tcx>,
2224 target: &'b ImplicitHasherType<'tcx>,
2225 suggestions: BTreeMap<Span, String>,
2228 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2229 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2234 suggestions: BTreeMap::new(),
2239 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2240 fn visit_body(&mut self, body: &'tcx Body) {
2241 let prev_body = self.body;
2242 self.body = self.cx.tcx.body_tables(body.id());
2243 walk_body(self, body);
2244 self.body = prev_body;
2247 fn visit_expr(&mut self, e: &'tcx Expr) {
2249 if let ExprKind::Call(ref fun, ref args) = e.node;
2250 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2251 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2253 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2257 if match_path(ty_path, &paths::HASHMAP) {
2258 if method.ident.name == "new" {
2260 .insert(e.span, "HashMap::default()".to_string());
2261 } else if method.ident.name == "with_capacity" {
2262 self.suggestions.insert(
2265 "HashMap::with_capacity_and_hasher({}, Default::default())",
2266 snippet(self.cx, args[0].span, "capacity"),
2270 } else if match_path(ty_path, &paths::HASHSET) {
2271 if method.ident.name == "new" {
2273 .insert(e.span, "HashSet::default()".to_string());
2274 } else if method.ident.name == "with_capacity" {
2275 self.suggestions.insert(
2278 "HashSet::with_capacity_and_hasher({}, Default::default())",
2279 snippet(self.cx, args[0].span, "capacity"),
2290 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2291 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2295 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2297 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2298 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2301 /// **Known problems:** None.
2307 /// *(r as *const _ as *mut _) += 1;
2312 /// Instead consider using interior mutability types.
2315 /// fn x(r: &UnsafeCell<i32>) {
2321 declare_clippy_lint! {
2322 pub CAST_REF_TO_MUT,
2324 "a cast of reference to a mutable pointer"
2327 pub struct RefToMut;
2329 impl LintPass for RefToMut {
2330 fn get_lints(&self) -> LintArray {
2331 lint_array!(CAST_REF_TO_MUT)
2334 fn name(&self) -> &'static str {
2339 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2340 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2342 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2343 if let ExprKind::Cast(e, t) = &e.node;
2344 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2345 if let ExprKind::Cast(e, t) = &e.node;
2346 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2347 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2353 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",