1 #![allow(clippy::default_hash_types)]
4 use std::cmp::Ordering;
5 use std::collections::BTreeMap;
7 use if_chain::if_chain;
9 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
11 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
12 use rustc::ty::layout::LayoutOf;
13 use rustc::ty::{self, InferTy, Ty, TyCtxt, TypeckTables};
14 use rustc::{declare_tool_lint, lint_array};
15 use rustc::ty::print::Printer;
16 use rustc_errors::Applicability;
17 use rustc_target::spec::abi::Abi;
18 use rustc_typeck::hir_ty_to_ty;
19 use syntax::ast::{FloatTy, IntTy, UintTy};
20 use syntax::errors::DiagnosticBuilder;
21 use syntax::source_map::Span;
23 use crate::consts::{constant, Constant};
24 use crate::utils::paths;
26 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
27 match_def_path, match_path, multispan_sugg, same_tys, sext, snippet, snippet_opt, snippet_with_applicability,
28 span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext, AbsolutePathBuffer,
31 /// Handles all the linting of funky types
34 declare_clippy_lint! {
35 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
37 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
38 /// the heap. So if you `Box` it, you just add another level of indirection
39 /// without any benefit whatsoever.
41 /// **Known problems:** None.
46 /// values: Box<Vec<Foo>>,
59 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
62 declare_clippy_lint! {
63 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
65 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
66 /// the heap. So if you `Box` its contents, you just add another level of indirection.
68 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
74 /// values: Vec<Box<i32>>,
87 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
90 declare_clippy_lint! {
91 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
94 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
95 /// represents an optional optional value which is logically the same thing as an optional
96 /// value but has an unneeded extra level of wrapping.
98 /// **Known problems:** None.
102 /// fn x() -> Option<Option<u32>> {
108 "usage of `Option<Option<T>>`"
111 declare_clippy_lint! {
112 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
113 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
115 /// **Why is this bad?** Gankro says:
117 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
118 /// pointers and indirection.
119 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
121 /// > "only" amortized for push/pop, should be faster in the general case for
122 /// almost every possible
123 /// > workload, and isn't even amortized at all if you can predict the capacity
126 /// > `LinkedList`s are only really good if you're doing a lot of merging or
127 /// splitting of lists.
128 /// > This is because they can just mangle some pointers instead of actually
129 /// copying the data. Even
130 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
131 /// can still be better
132 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
134 /// **Known problems:** False positives – the instances where using a
135 /// `LinkedList` makes sense are few and far between, but they can still happen.
139 /// let x = LinkedList::new();
143 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
146 declare_clippy_lint! {
147 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
149 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
152 /// **Known problems:** None.
156 /// fn foo(bar: &Box<T>) { ... }
162 /// fn foo(bar: &T) { ... }
166 "a borrow of a boxed type"
169 impl LintPass for TypePass {
170 fn get_lints(&self) -> LintArray {
171 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
174 fn name(&self) -> &'static str {
179 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
180 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
181 // Skip trait implementations; see issue #605.
182 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find_by_hir_id(cx.tcx.hir().get_parent_item(id)) {
183 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
188 check_fn_decl(cx, decl);
191 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
192 check_ty(cx, &field.ty, false);
195 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
197 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
198 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
203 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
204 if let Some(ref ty) = local.ty {
205 check_ty(cx, ty, true);
210 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
211 for input in &decl.inputs {
212 check_ty(cx, input, false);
215 if let FunctionRetTy::Return(ref ty) = decl.output {
216 check_ty(cx, ty, false);
220 /// Checks if `qpath` has last segment with type parameter matching `path`
221 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
222 let last = last_path_segment(qpath);
224 if let Some(ref params) = last.args;
225 if !params.parenthesized;
226 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
227 GenericArg::Type(ty) => Some(ty),
230 if let TyKind::Path(ref qpath) = ty.node;
231 if let Some(did) = cx.tables.qpath_def(qpath, ty.hir_id).opt_def_id();
232 if match_def_path(cx.tcx, did, path);
240 /// Recursively check for `TypePass` lints in the given type. Stop at the first
243 /// The parameter `is_local` distinguishes the context of the type; types from
244 /// local bindings should only be checked for the `BORROWED_BOX` lint.
245 #[allow(clippy::too_many_lines)]
246 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
247 if in_macro(hir_ty.span) {
251 TyKind::Path(ref qpath) if !is_local => {
252 let hir_id = hir_ty.hir_id;
253 let def = cx.tables.qpath_def(qpath, hir_id);
254 if let Some(def_id) = def.opt_def_id() {
255 if Some(def_id) == cx.tcx.lang_items().owned_box() {
256 if match_type_parameter(cx, qpath, &paths::VEC) {
261 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
262 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
264 return; // don't recurse into the type
266 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
268 // Get the _ part of Vec<_>
269 if let Some(ref last) = last_path_segment(qpath).args;
270 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
271 GenericArg::Type(ty) => Some(ty),
274 // ty is now _ at this point
275 if let TyKind::Path(ref ty_qpath) = ty.node;
276 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
277 if let Some(def_id) = def.opt_def_id();
278 if Some(def_id) == cx.tcx.lang_items().owned_box();
279 // At this point, we know ty is Box<T>, now get T
280 if let Some(ref last) = last_path_segment(ty_qpath).args;
281 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
282 GenericArg::Type(ty) => Some(ty),
286 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
287 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
292 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
294 format!("Vec<{}>", ty_ty),
295 Applicability::MachineApplicable,
297 return; // don't recurse into the type
301 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
302 if match_type_parameter(cx, qpath, &paths::OPTION) {
307 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
308 enum if you need to distinguish all 3 cases",
310 return; // don't recurse into the type
312 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
317 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
318 "a VecDeque might work",
320 return; // don't recurse into the type
324 QPath::Resolved(Some(ref ty), ref p) => {
325 check_ty(cx, ty, is_local);
326 for ty in p.segments.iter().flat_map(|seg| {
329 .map_or_else(|| [].iter(), |params| params.args.iter())
330 .filter_map(|arg| match arg {
331 GenericArg::Type(ty) => Some(ty),
335 check_ty(cx, ty, is_local);
338 QPath::Resolved(None, ref p) => {
339 for ty in p.segments.iter().flat_map(|seg| {
342 .map_or_else(|| [].iter(), |params| params.args.iter())
343 .filter_map(|arg| match arg {
344 GenericArg::Type(ty) => Some(ty),
348 check_ty(cx, ty, is_local);
351 QPath::TypeRelative(ref ty, ref seg) => {
352 check_ty(cx, ty, is_local);
353 if let Some(ref params) = seg.args {
354 for ty in params.args.iter().filter_map(|arg| match arg {
355 GenericArg::Type(ty) => Some(ty),
358 check_ty(cx, ty, is_local);
364 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
366 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
367 check_ty(cx, ty, is_local)
369 TyKind::Tup(ref tys) => {
371 check_ty(cx, ty, is_local);
378 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
379 match mut_ty.ty.node {
380 TyKind::Path(ref qpath) => {
381 let hir_id = mut_ty.ty.hir_id;
382 let def = cx.tables.qpath_def(qpath, hir_id);
384 if let Some(def_id) = def.opt_def_id();
385 if Some(def_id) == cx.tcx.lang_items().owned_box();
386 if let QPath::Resolved(None, ref path) = *qpath;
387 if let [ref bx] = *path.segments;
388 if let Some(ref params) = bx.args;
389 if !params.parenthesized;
390 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
391 GenericArg::Type(ty) => Some(ty),
395 if is_any_trait(inner) {
396 // Ignore `Box<Any>` types; see issue #1884 for details.
400 let ltopt = if lt.is_elided() {
403 format!("{} ", lt.name.ident().as_str())
405 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
410 let mut applicability = Applicability::MachineApplicable;
415 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
421 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
423 Applicability::Unspecified,
425 return; // don't recurse into the type
428 check_ty(cx, &mut_ty.ty, is_local);
430 _ => check_ty(cx, &mut_ty.ty, is_local),
434 // Returns true if given type is `Any` trait.
435 fn is_any_trait(t: &hir::Ty) -> bool {
437 if let TyKind::TraitObject(ref traits, _) = t.node;
438 if traits.len() >= 1;
439 // Only Send/Sync can be used as additional traits, so it is enough to
440 // check only the first trait.
441 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
452 declare_clippy_lint! {
453 /// **What it does:** Checks for binding a unit value.
455 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
456 /// binding one is kind of pointless.
458 /// **Known problems:** None.
468 "creating a let binding to a value of unit type, which usually can't be used afterwards"
471 impl LintPass for LetPass {
472 fn get_lints(&self) -> LintArray {
473 lint_array!(LET_UNIT_VALUE)
476 fn name(&self) -> &'static str {
481 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
482 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
483 if let StmtKind::Local(ref local) = stmt.node {
484 if is_unit(cx.tables.pat_ty(&local.pat)) {
485 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
488 if higher::is_from_for_desugar(local) {
496 "this let-binding has unit value. Consider omitting `let {} =`",
497 snippet(cx, local.pat.span, "..")
505 declare_clippy_lint! {
506 /// **What it does:** Checks for comparisons to unit.
508 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
509 /// clumsily written constant. Mostly this happens when someone accidentally
510 /// adds semicolons at the end of the operands.
512 /// **Known problems:** None.
540 "comparing unit values"
545 impl LintPass for UnitCmp {
546 fn get_lints(&self) -> LintArray {
547 lint_array!(UNIT_CMP)
550 fn name(&self) -> &'static str {
555 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
556 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
557 if in_macro(expr.span) {
560 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
562 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
563 let result = match op {
564 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
572 "{}-comparison of unit values detected. This will always be {}",
582 declare_clippy_lint! {
583 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
584 /// unit literal (`()`).
586 /// **Why is this bad?** This is likely the result of an accidental semicolon.
588 /// **Known problems:** None.
599 "passing unit to a function"
604 impl LintPass for UnitArg {
605 fn get_lints(&self) -> LintArray {
606 lint_array!(UNIT_ARG)
609 fn name(&self) -> &'static str {
614 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
615 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
616 if in_macro(expr.span) {
620 // apparently stuff in the desugaring of `?` can trigger this
621 // so check for that here
622 // only the calls to `Try::from_error` is marked as desugared,
623 // so we need to check both the current Expr and its parent.
624 if is_questionmark_desugar_marked_call(expr) {
628 let map = &cx.tcx.hir();
629 let opt_parent_node = map.find_by_hir_id(map.get_parent_node_by_hir_id(expr.hir_id));
630 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
631 if is_questionmark_desugar_marked_call(parent_expr);
638 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
640 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
641 if let ExprKind::Match(.., match_source) = &arg.node {
642 if *match_source == MatchSource::TryDesugar {
651 "passing a unit value to a function",
652 "if you intended to pass a unit value, use a unit literal instead",
654 Applicability::MachineApplicable,
664 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
665 use syntax_pos::hygiene::CompilerDesugaringKind;
666 if let ExprKind::Call(ref callee, _) = expr.node {
667 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
673 fn is_unit(ty: Ty<'_>) -> bool {
675 ty::Tuple(slice) if slice.is_empty() => true,
680 fn is_unit_literal(expr: &Expr) -> bool {
682 ExprKind::Tup(ref slice) if slice.is_empty() => true,
689 declare_clippy_lint! {
690 /// **What it does:** Checks for casts from any numerical to a float type where
691 /// the receiving type cannot store all values from the original type without
692 /// rounding errors. This possible rounding is to be expected, so this lint is
693 /// `Allow` by default.
695 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
696 /// or any 64-bit integer to `f64`.
698 /// **Why is this bad?** It's not bad at all. But in some applications it can be
699 /// helpful to know where precision loss can take place. This lint can help find
700 /// those places in the code.
702 /// **Known problems:** None.
706 /// let x = u64::MAX;
709 pub CAST_PRECISION_LOSS,
711 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
714 declare_clippy_lint! {
715 /// **What it does:** Checks for casts from a signed to an unsigned numerical
716 /// type. In this case, negative values wrap around to large positive values,
717 /// which can be quite surprising in practice. However, as the cast works as
718 /// defined, this lint is `Allow` by default.
720 /// **Why is this bad?** Possibly surprising results. You can activate this lint
721 /// as a one-time check to see where numerical wrapping can arise.
723 /// **Known problems:** None.
728 /// y as u128 // will return 18446744073709551615
732 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
735 declare_clippy_lint! {
736 /// **What it does:** Checks for on casts between numerical types that may
737 /// truncate large values. This is expected behavior, so the cast is `Allow` by
740 /// **Why is this bad?** In some problem domains, it is good practice to avoid
741 /// truncation. This lint can be activated to help assess where additional
742 /// checks could be beneficial.
744 /// **Known problems:** None.
748 /// fn as_u8(x: u64) -> u8 {
752 pub CAST_POSSIBLE_TRUNCATION,
754 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
757 declare_clippy_lint! {
758 /// **What it does:** Checks for casts from an unsigned type to a signed type of
759 /// the same size. Performing such a cast is a 'no-op' for the compiler,
760 /// i.e., nothing is changed at the bit level, and the binary representation of
761 /// the value is reinterpreted. This can cause wrapping if the value is too big
762 /// for the target signed type. However, the cast works as defined, so this lint
763 /// is `Allow` by default.
765 /// **Why is this bad?** While such a cast is not bad in itself, the results can
766 /// be surprising when this is not the intended behavior, as demonstrated by the
769 /// **Known problems:** None.
773 /// u32::MAX as i32 // will yield a value of `-1`
775 pub CAST_POSSIBLE_WRAP,
777 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
780 declare_clippy_lint! {
781 /// **What it does:** Checks for on casts between numerical types that may
782 /// be replaced by safe conversion functions.
784 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
785 /// conversions, including silently lossy conversions. Conversion functions such
786 /// as `i32::from` will only perform lossless conversions. Using the conversion
787 /// functions prevents conversions from turning into silent lossy conversions if
788 /// the types of the input expressions ever change, and make it easier for
789 /// people reading the code to know that the conversion is lossless.
791 /// **Known problems:** None.
795 /// fn as_u64(x: u8) -> u64 {
800 /// Using `::from` would look like this:
803 /// fn as_u64(x: u8) -> u64 {
809 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
812 declare_clippy_lint! {
813 /// **What it does:** Checks for casts to the same type.
815 /// **Why is this bad?** It's just unnecessary.
817 /// **Known problems:** None.
821 /// let _ = 2i32 as i32
823 pub UNNECESSARY_CAST,
825 "cast to the same type, e.g., `x as i32` where `x: i32`"
828 declare_clippy_lint! {
829 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
830 /// more-strictly-aligned pointer
832 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
835 /// **Known problems:** None.
839 /// let _ = (&1u8 as *const u8) as *const u16;
840 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
842 pub CAST_PTR_ALIGNMENT,
844 "cast from a pointer to a more-strictly-aligned pointer"
847 declare_clippy_lint! {
848 /// **What it does:** Checks for casts of function pointers to something other than usize
850 /// **Why is this bad?**
851 /// Casting a function pointer to anything other than usize/isize is not portable across
852 /// architectures, because you end up losing bits if the target type is too small or end up with a
853 /// bunch of extra bits that waste space and add more instructions to the final binary than
854 /// strictly necessary for the problem
856 /// Casting to isize also doesn't make sense since there are no signed addresses.
862 /// fn fun() -> i32 { 1 }
863 /// let a = fun as i64;
866 /// fn fun2() -> i32 { 1 }
867 /// let a = fun2 as usize;
869 pub FN_TO_NUMERIC_CAST,
871 "casting a function pointer to a numeric type other than usize"
874 declare_clippy_lint! {
875 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
878 /// **Why is this bad?**
879 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
880 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
881 /// a comment) to perform the truncation.
887 /// fn fn1() -> i16 {
890 /// let _ = fn1 as i32;
892 /// // Better: Cast to usize first, then comment with the reason for the truncation
893 /// fn fn2() -> i16 {
896 /// let fn_ptr = fn2 as usize;
897 /// let fn_ptr_truncated = fn_ptr as i32;
899 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
901 "casting a function pointer to a numeric type not wide enough to store the address"
904 /// Returns the size in bits of an integral type.
905 /// Will return 0 if the type is not an int or uint variant
906 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
908 ty::Int(i) => match i {
909 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
916 ty::Uint(i) => match i {
917 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
928 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
930 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
935 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
936 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
937 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
938 let arch_dependent_str = "on targets with 64-bit wide pointers ";
939 let from_nbits_str = if arch_dependent {
941 } else if is_isize_or_usize(cast_from) {
942 "32 or 64".to_owned()
944 int_ty_to_nbits(cast_from, cx.tcx).to_string()
951 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
952 is only {4} bits wide)",
954 if cast_to_f64 { "f64" } else { "f32" },
955 if arch_dependent { arch_dependent_str } else { "" },
962 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
963 if let ExprKind::Binary(_, _, _) = op.node {
964 if snip.starts_with('(') && snip.ends_with(')') {
971 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
972 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
973 if in_constant(cx, expr.hir_id) {
976 // The suggestion is to use a function call, so if the original expression
977 // has parens on the outside, they are no longer needed.
978 let mut applicability = Applicability::MachineApplicable;
979 let opt = snippet_opt(cx, op.span);
980 let sugg = if let Some(ref snip) = opt {
981 if should_strip_parens(op, snip) {
982 &snip[1..snip.len() - 1]
987 applicability = Applicability::HasPlaceholders;
996 "casting {} to {} may become silently lossy if types change",
1000 format!("{}::from({})", cast_to, sugg),
1011 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1012 if !cast_from.is_signed() || cast_to.is_signed() {
1016 // don't lint for positive constants
1017 let const_val = constant(cx, &cx.tables, op);
1019 if let Some((const_val, _)) = const_val;
1020 if let Constant::Int(n) = const_val;
1021 if let ty::Int(ity) = cast_from.sty;
1022 if sext(cx.tcx, n, ity) >= 0;
1032 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1036 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1037 let arch_64_suffix = " on targets with 64-bit wide pointers";
1038 let arch_32_suffix = " on targets with 32-bit wide pointers";
1039 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1040 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1041 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1042 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1043 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1044 (true, true) | (false, false) => (
1045 to_nbits < from_nbits,
1047 to_nbits == from_nbits && cast_unsigned_to_signed,
1057 to_nbits <= 32 && cast_unsigned_to_signed,
1063 cast_unsigned_to_signed,
1064 if from_nbits == 64 {
1071 if span_truncation {
1074 CAST_POSSIBLE_TRUNCATION,
1077 "casting {} to {} may truncate the value{}",
1080 match suffix_truncation {
1081 ArchSuffix::_32 => arch_32_suffix,
1082 ArchSuffix::_64 => arch_64_suffix,
1083 ArchSuffix::None => "",
1094 "casting {} to {} may wrap around the value{}",
1098 ArchSuffix::_32 => arch_32_suffix,
1099 ArchSuffix::_64 => arch_64_suffix,
1100 ArchSuffix::None => "",
1107 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1108 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1109 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1110 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1111 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1113 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1117 impl LintPass for CastPass {
1118 fn get_lints(&self) -> LintArray {
1120 CAST_PRECISION_LOSS,
1122 CAST_POSSIBLE_TRUNCATION,
1128 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1132 fn name(&self) -> &'static str {
1137 // Check if the given type is either `core::ffi::c_void` or
1138 // one of the platform specific `libc::<platform>::c_void` of libc.
1139 fn is_c_void<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'_>) -> bool {
1140 if let ty::Adt(adt, _) = ty.sty {
1141 let names = AbsolutePathBuffer { tcx }.print_def_path(adt.did, &[]).unwrap();
1143 if names.is_empty() {
1146 if names[0] == "libc" || names[0] == "core" && *names.last().unwrap() == "c_void" {
1153 /// Returns the mantissa bits wide of a fp type.
1154 /// Will return 0 if the type is not a fp
1155 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1157 ty::Float(FloatTy::F32) => 23,
1158 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1163 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1164 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1165 if let ExprKind::Cast(ref ex, _) = expr.node {
1166 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1167 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1168 if let ExprKind::Lit(ref lit) = ex.node {
1169 use syntax::ast::{LitIntType, LitKind};
1170 if let LitKind::Int(n, _) = lit.node {
1171 if cast_to.is_fp() {
1172 let from_nbits = 128 - n.leading_zeros();
1173 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1174 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1179 &format!("casting integer literal to {} is unnecessary", cast_to),
1181 format!("{}_{}", n, cast_to),
1182 Applicability::MachineApplicable,
1189 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1191 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1197 "casting to the same type is unnecessary (`{}` -> `{}`)",
1205 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1206 match (cast_from.is_integral(), cast_to.is_integral()) {
1208 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1209 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1214 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1215 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1217 if from_nbits < to_nbits {
1218 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1224 CAST_POSSIBLE_TRUNCATION,
1226 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1228 if !cast_to.is_signed() {
1233 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1238 check_loss_of_sign(cx, expr, ex, cast_from, cast_to);
1239 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1240 check_lossless(cx, expr, ex, cast_from, cast_to);
1243 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1246 CAST_POSSIBLE_TRUNCATION,
1248 "casting f64 to f32 may truncate the value",
1251 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1252 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1259 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1260 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1261 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1262 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1263 if from_align < to_align;
1264 // with c_void, we inherently need to trust the user
1265 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1271 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1279 fn lint_fn_to_numeric_cast(
1280 cx: &LateContext<'_, '_>,
1286 // We only want to check casts to `ty::Uint` or `ty::Int`
1288 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1291 match cast_from.sty {
1292 ty::FnDef(..) | ty::FnPtr(_) => {
1293 let mut applicability = Applicability::MachineApplicable;
1294 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1296 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1297 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1300 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1303 "casting function pointer `{}` to `{}`, which truncates the value",
1304 from_snippet, cast_to
1307 format!("{} as usize", from_snippet),
1310 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1315 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1317 format!("{} as usize", from_snippet),
1326 declare_clippy_lint! {
1327 /// **What it does:** Checks for types used in structs, parameters and `let`
1328 /// declarations above a certain complexity threshold.
1330 /// **Why is this bad?** Too complex types make the code less readable. Consider
1331 /// using a `type` definition to simplify them.
1333 /// **Known problems:** None.
1338 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1341 pub TYPE_COMPLEXITY,
1343 "usage of very complex types that might be better factored into `type` definitions"
1346 pub struct TypeComplexityPass {
1350 impl TypeComplexityPass {
1351 pub fn new(threshold: u64) -> Self {
1356 impl LintPass for TypeComplexityPass {
1357 fn get_lints(&self) -> LintArray {
1358 lint_array!(TYPE_COMPLEXITY)
1361 fn name(&self) -> &'static str {
1362 "TypeComplexityPass"
1366 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1369 cx: &LateContext<'a, 'tcx>,
1376 self.check_fndecl(cx, decl);
1379 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1380 // enum variants are also struct fields now
1381 self.check_type(cx, &field.ty);
1384 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1386 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1387 // functions, enums, structs, impls and traits are covered
1392 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1394 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1395 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1396 // methods with default impl are covered by check_fn
1401 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1403 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1404 // methods are covered by check_fn
1409 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1410 if let Some(ref ty) = local.ty {
1411 self.check_type(cx, ty);
1416 impl<'a, 'tcx> TypeComplexityPass {
1417 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1418 for arg in &decl.inputs {
1419 self.check_type(cx, arg);
1421 if let Return(ref ty) = decl.output {
1422 self.check_type(cx, ty);
1426 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1427 if in_macro(ty.span) {
1431 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1432 visitor.visit_ty(ty);
1436 if score > self.threshold {
1441 "very complex type used. Consider factoring parts into `type` definitions",
1447 /// Walks a type and assigns a complexity score to it.
1448 struct TypeComplexityVisitor {
1449 /// total complexity score of the type
1451 /// current nesting level
1455 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1456 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1457 let (add_score, sub_nest) = match ty.node {
1458 // _, &x and *x have only small overhead; don't mess with nesting level
1459 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1461 // the "normal" components of a type: named types, arrays/tuples
1462 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1464 // function types bring a lot of overhead
1465 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1467 TyKind::TraitObject(ref param_bounds, _) => {
1468 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1469 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1470 GenericParamKind::Lifetime { .. } => true,
1474 if has_lifetime_parameters {
1475 // complex trait bounds like A<'a, 'b>
1478 // simple trait bounds like A + B
1485 self.score += add_score;
1486 self.nest += sub_nest;
1488 self.nest -= sub_nest;
1490 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1491 NestedVisitorMap::None
1495 declare_clippy_lint! {
1496 /// **What it does:** Checks for expressions where a character literal is cast
1497 /// to `u8` and suggests using a byte literal instead.
1499 /// **Why is this bad?** In general, casting values to smaller types is
1500 /// error-prone and should be avoided where possible. In the particular case of
1501 /// converting a character literal to u8, it is easy to avoid by just using a
1502 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1503 /// than `'a' as u8`.
1505 /// **Known problems:** None.
1512 /// A better version, using the byte literal:
1519 "casting a character literal to u8"
1522 pub struct CharLitAsU8;
1524 impl LintPass for CharLitAsU8 {
1525 fn get_lints(&self) -> LintArray {
1526 lint_array!(CHAR_LIT_AS_U8)
1529 fn name(&self) -> &'static str {
1534 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1535 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1536 use syntax::ast::{LitKind, UintTy};
1538 if let ExprKind::Cast(ref e, _) = expr.node {
1539 if let ExprKind::Lit(ref l) = e.node {
1540 if let LitKind::Char(_) = l.node {
1541 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1542 let msg = "casting character literal to u8. `char`s \
1543 are 4 bytes wide in rust, so casting to u8 \
1546 "Consider using a byte literal instead:\nb{}",
1547 snippet(cx, e.span, "'x'")
1549 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1557 declare_clippy_lint! {
1558 /// **What it does:** Checks for comparisons where one side of the relation is
1559 /// either the minimum or maximum value for its type and warns if it involves a
1560 /// case that is always true or always false. Only integer and boolean types are
1563 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1564 /// that is is possible for `x` to be less than the minimum. Expressions like
1565 /// `max < x` are probably mistakes.
1567 /// **Known problems:** For `usize` the size of the current compile target will
1568 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1569 /// a comparison to detect target pointer width will trigger this lint. One can
1570 /// use `mem::sizeof` and compare its value or conditional compilation
1572 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1577 /// let vec: Vec<isize> = vec![];
1578 /// if vec.len() <= 0 {}
1579 /// if 100 > std::i32::MAX {}
1581 pub ABSURD_EXTREME_COMPARISONS,
1583 "a comparison with a maximum or minimum value that is always true or false"
1586 pub struct AbsurdExtremeComparisons;
1588 impl LintPass for AbsurdExtremeComparisons {
1589 fn get_lints(&self) -> LintArray {
1590 lint_array!(ABSURD_EXTREME_COMPARISONS)
1593 fn name(&self) -> &'static str {
1594 "AbsurdExtremeComparisons"
1603 struct ExtremeExpr<'a> {
1608 enum AbsurdComparisonResult {
1611 InequalityImpossible,
1614 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1615 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1616 let precast_ty = cx.tables.expr_ty(cast_exp);
1617 let cast_ty = cx.tables.expr_ty(expr);
1619 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1625 fn detect_absurd_comparison<'a, 'tcx>(
1626 cx: &LateContext<'a, 'tcx>,
1630 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1631 use crate::types::AbsurdComparisonResult::*;
1632 use crate::types::ExtremeType::*;
1633 use crate::utils::comparisons::*;
1635 // absurd comparison only makes sense on primitive types
1636 // primitive types don't implement comparison operators with each other
1637 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1641 // comparisons between fix sized types and target sized types are considered unanalyzable
1642 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1646 let normalized = normalize_comparison(op, lhs, rhs);
1647 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1653 let lx = detect_extreme_expr(cx, normalized_lhs);
1654 let rx = detect_extreme_expr(cx, normalized_rhs);
1659 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1660 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1666 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1667 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1668 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1669 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1673 Rel::Ne | Rel::Eq => return None,
1677 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1678 use crate::types::ExtremeType::*;
1680 let ty = cx.tables.expr_ty(expr);
1682 let cv = constant(cx, cx.tables, expr)?.0;
1684 let which = match (&ty.sty, cv) {
1685 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1686 (&ty::Int(ity), Constant::Int(i))
1687 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1692 (&ty::Bool, Constant::Bool(true)) => Maximum,
1693 (&ty::Int(ity), Constant::Int(i))
1694 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1698 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1702 Some(ExtremeExpr { which, expr })
1705 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1706 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1707 use crate::types::AbsurdComparisonResult::*;
1708 use crate::types::ExtremeType::*;
1710 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1711 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1712 if !in_macro(expr.span) {
1713 let msg = "this comparison involving the minimum or maximum element for this \
1714 type contains a case that is always true or always false";
1716 let conclusion = match result {
1717 AlwaysFalse => "this comparison is always false".to_owned(),
1718 AlwaysTrue => "this comparison is always true".to_owned(),
1719 InequalityImpossible => format!(
1720 "the case where the two sides are not equal never occurs, consider using {} == {} \
1722 snippet(cx, lhs.span, "lhs"),
1723 snippet(cx, rhs.span, "rhs")
1728 "because {} is the {} value for this type, {}",
1729 snippet(cx, culprit.expr.span, "x"),
1730 match culprit.which {
1731 Minimum => "minimum",
1732 Maximum => "maximum",
1737 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1744 declare_clippy_lint! {
1745 /// **What it does:** Checks for comparisons where the relation is always either
1746 /// true or false, but where one side has been upcast so that the comparison is
1747 /// necessary. Only integer types are checked.
1749 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1750 /// will mistakenly imply that it is possible for `x` to be outside the range of
1753 /// **Known problems:**
1754 /// https://github.com/rust-lang/rust-clippy/issues/886
1758 /// let x : u8 = ...; (x as u32) > 300
1760 pub INVALID_UPCAST_COMPARISONS,
1762 "a comparison involving an upcast which is always true or false"
1765 pub struct InvalidUpcastComparisons;
1767 impl LintPass for InvalidUpcastComparisons {
1768 fn get_lints(&self) -> LintArray {
1769 lint_array!(INVALID_UPCAST_COMPARISONS)
1772 fn name(&self) -> &'static str {
1773 "InvalidUpcastComparisons"
1777 #[derive(Copy, Clone, Debug, Eq)]
1784 #[allow(clippy::cast_sign_loss)]
1785 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1788 } else if u > (i128::max_value() as u128) {
1796 impl PartialEq for FullInt {
1797 fn eq(&self, other: &Self) -> bool {
1798 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1802 impl PartialOrd for FullInt {
1803 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1804 Some(match (self, other) {
1805 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1806 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1807 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1808 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1812 impl Ord for FullInt {
1813 fn cmp(&self, other: &Self) -> Ordering {
1814 self.partial_cmp(other)
1815 .expect("partial_cmp for FullInt can never return None")
1819 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1821 use syntax::ast::{IntTy, UintTy};
1823 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1824 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1825 let cast_ty = cx.tables.expr_ty(expr);
1826 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1827 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1830 match pre_cast_ty.sty {
1831 ty::Int(int_ty) => Some(match int_ty {
1833 FullInt::S(i128::from(i8::min_value())),
1834 FullInt::S(i128::from(i8::max_value())),
1837 FullInt::S(i128::from(i16::min_value())),
1838 FullInt::S(i128::from(i16::max_value())),
1841 FullInt::S(i128::from(i32::min_value())),
1842 FullInt::S(i128::from(i32::max_value())),
1845 FullInt::S(i128::from(i64::min_value())),
1846 FullInt::S(i128::from(i64::max_value())),
1848 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1850 FullInt::S(isize::min_value() as i128),
1851 FullInt::S(isize::max_value() as i128),
1854 ty::Uint(uint_ty) => Some(match uint_ty {
1856 FullInt::U(u128::from(u8::min_value())),
1857 FullInt::U(u128::from(u8::max_value())),
1860 FullInt::U(u128::from(u16::min_value())),
1861 FullInt::U(u128::from(u16::max_value())),
1864 FullInt::U(u128::from(u32::min_value())),
1865 FullInt::U(u128::from(u32::max_value())),
1868 FullInt::U(u128::from(u64::min_value())),
1869 FullInt::U(u128::from(u64::max_value())),
1871 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1873 FullInt::U(usize::min_value() as u128),
1874 FullInt::U(usize::max_value() as u128),
1884 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1885 let val = constant(cx, cx.tables, expr)?.0;
1886 if let Constant::Int(const_int) = val {
1887 match cx.tables.expr_ty(expr).sty {
1888 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1889 ty::Uint(_) => Some(FullInt::U(const_int)),
1897 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1898 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1901 INVALID_UPCAST_COMPARISONS,
1904 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1905 snippet(cx, cast_val.span, "the expression"),
1906 if always { "true" } else { "false" },
1912 fn upcast_comparison_bounds_err<'a, 'tcx>(
1913 cx: &LateContext<'a, 'tcx>,
1915 rel: comparisons::Rel,
1916 lhs_bounds: Option<(FullInt, FullInt)>,
1921 use crate::utils::comparisons::*;
1923 if let Some((lb, ub)) = lhs_bounds {
1924 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1925 if rel == Rel::Eq || rel == Rel::Ne {
1926 if norm_rhs_val < lb || norm_rhs_val > ub {
1927 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1929 } else if match rel {
1944 Rel::Eq | Rel::Ne => unreachable!(),
1946 err_upcast_comparison(cx, span, lhs, true)
1947 } else if match rel {
1962 Rel::Eq | Rel::Ne => unreachable!(),
1964 err_upcast_comparison(cx, span, lhs, false)
1970 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1971 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1972 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1973 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1974 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1980 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1981 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1983 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1984 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1989 declare_clippy_lint! {
1990 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1991 /// over different hashers and implicitly defaulting to the default hashing
1992 /// algorithm (SipHash).
1994 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1997 /// **Known problems:** Suggestions for replacing constructors can contain
1998 /// false-positives. Also applying suggestions can require modification of other
1999 /// pieces of code, possibly including external crates.
2003 /// # use std::collections::HashMap;
2004 /// # use std::hash::Hash;
2005 /// # trait Serialize {};
2006 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
2008 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
2010 pub IMPLICIT_HASHER,
2012 "missing generalization over different hashers"
2015 pub struct ImplicitHasher;
2017 impl LintPass for ImplicitHasher {
2018 fn get_lints(&self) -> LintArray {
2019 lint_array!(IMPLICIT_HASHER)
2022 fn name(&self) -> &'static str {
2027 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
2028 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
2029 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
2030 use syntax_pos::BytePos;
2032 fn suggestion<'a, 'tcx>(
2033 cx: &LateContext<'a, 'tcx>,
2034 db: &mut DiagnosticBuilder<'_>,
2035 generics_span: Span,
2036 generics_suggestion_span: Span,
2037 target: &ImplicitHasherType<'_>,
2038 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2040 let generics_snip = snippet(cx, generics_span, "");
2042 let generics_snip = if generics_snip.is_empty() {
2045 &generics_snip[1..generics_snip.len() - 1]
2050 "consider adding a type parameter".to_string(),
2053 generics_suggestion_span,
2055 "<{}{}S: ::std::hash::BuildHasher{}>",
2057 if generics_snip.is_empty() { "" } else { ", " },
2058 if vis.suggestions.is_empty() {
2061 // request users to add `Default` bound so that generic constructors can be used
2068 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2073 if !vis.suggestions.is_empty() {
2074 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2078 if !cx.access_levels.is_exported(cx.tcx.hir().hir_to_node_id(item.hir_id)) {
2083 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2084 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2087 for target in &vis.found {
2088 if differing_macro_contexts(item.span, target.span()) {
2092 let generics_suggestion_span = generics.span.substitute_dummy({
2093 let pos = snippet_opt(cx, item.span.until(target.span()))
2094 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2095 if let Some(pos) = pos {
2096 Span::new(pos, pos, item.span.data().ctxt)
2102 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2103 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2104 ctr_vis.visit_impl_item(item);
2112 "impl for `{}` should be generalized over different hashers",
2116 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2121 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2122 let body = cx.tcx.hir().body(body_id);
2124 for ty in &decl.inputs {
2125 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2128 for target in &vis.found {
2129 let generics_suggestion_span = generics.span.substitute_dummy({
2130 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2132 let i = snip.find("fn")?;
2133 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2135 .expect("failed to create span for type parameters");
2136 Span::new(pos, pos, item.span.data().ctxt)
2139 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2140 ctr_vis.visit_body(body);
2147 "parameter of type `{}` should be generalized over different hashers",
2151 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2162 enum ImplicitHasherType<'tcx> {
2163 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2164 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2167 impl<'tcx> ImplicitHasherType<'tcx> {
2168 /// Checks that `ty` is a target type without a BuildHasher.
2169 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2170 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2171 let params: Vec<_> = path
2179 .filter_map(|arg| match arg {
2180 GenericArg::Type(ty) => Some(ty),
2184 let params_len = params.len();
2186 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2188 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2189 Some(ImplicitHasherType::HashMap(
2192 snippet(cx, params[0].span, "K"),
2193 snippet(cx, params[1].span, "V"),
2195 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2196 Some(ImplicitHasherType::HashSet(
2199 snippet(cx, params[0].span, "T"),
2209 fn type_name(&self) -> &'static str {
2211 ImplicitHasherType::HashMap(..) => "HashMap",
2212 ImplicitHasherType::HashSet(..) => "HashSet",
2216 fn type_arguments(&self) -> String {
2218 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2219 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2223 fn ty(&self) -> Ty<'tcx> {
2225 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2229 fn span(&self) -> Span {
2231 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2236 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2237 cx: &'a LateContext<'a, 'tcx>,
2238 found: Vec<ImplicitHasherType<'tcx>>,
2241 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2242 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2243 Self { cx, found: vec![] }
2247 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2248 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2249 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2250 self.found.push(target);
2256 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2257 NestedVisitorMap::None
2261 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2262 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2263 cx: &'a LateContext<'a, 'tcx>,
2264 body: &'a TypeckTables<'tcx>,
2265 target: &'b ImplicitHasherType<'tcx>,
2266 suggestions: BTreeMap<Span, String>,
2269 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2270 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2275 suggestions: BTreeMap::new(),
2280 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2281 fn visit_body(&mut self, body: &'tcx Body) {
2282 let prev_body = self.body;
2283 self.body = self.cx.tcx.body_tables(body.id());
2284 walk_body(self, body);
2285 self.body = prev_body;
2288 fn visit_expr(&mut self, e: &'tcx Expr) {
2290 if let ExprKind::Call(ref fun, ref args) = e.node;
2291 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2292 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2294 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2298 if match_path(ty_path, &paths::HASHMAP) {
2299 if method.ident.name == "new" {
2301 .insert(e.span, "HashMap::default()".to_string());
2302 } else if method.ident.name == "with_capacity" {
2303 self.suggestions.insert(
2306 "HashMap::with_capacity_and_hasher({}, Default::default())",
2307 snippet(self.cx, args[0].span, "capacity"),
2311 } else if match_path(ty_path, &paths::HASHSET) {
2312 if method.ident.name == "new" {
2314 .insert(e.span, "HashSet::default()".to_string());
2315 } else if method.ident.name == "with_capacity" {
2316 self.suggestions.insert(
2319 "HashSet::with_capacity_and_hasher({}, Default::default())",
2320 snippet(self.cx, args[0].span, "capacity"),
2331 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2332 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2336 declare_clippy_lint! {
2337 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2339 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2340 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2343 /// **Known problems:** None.
2349 /// *(r as *const _ as *mut _) += 1;
2354 /// Instead consider using interior mutability types.
2357 /// use std::cell::UnsafeCell;
2359 /// fn x(r: &UnsafeCell<i32>) {
2365 pub CAST_REF_TO_MUT,
2367 "a cast of reference to a mutable pointer"
2370 pub struct RefToMut;
2372 impl LintPass for RefToMut {
2373 fn get_lints(&self) -> LintArray {
2374 lint_array!(CAST_REF_TO_MUT)
2377 fn name(&self) -> &'static str {
2382 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2383 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2385 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2386 if let ExprKind::Cast(e, t) = &e.node;
2387 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2388 if let ExprKind::Cast(e, t) = &e.node;
2389 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2390 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2396 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",