1 #![allow(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_lint_pass, declare_tool_lint, impl_lint_pass};
15 use rustc_errors::Applicability;
16 use rustc_target::spec::abi::Abi;
17 use rustc_typeck::hir_ty_to_ty;
18 use syntax::ast::{FloatTy, IntTy, UintTy};
19 use syntax::errors::DiagnosticBuilder;
20 use syntax::source_map::Span;
21 use syntax::symbol::sym;
23 use crate::consts::{constant, Constant};
24 use crate::utils::paths;
26 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro_or_desugar, 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,
31 declare_clippy_lint! {
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>>,
56 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
59 declare_clippy_lint! {
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>>,
84 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
87 declare_clippy_lint! {
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>> {
105 "usage of `Option<Option<T>>`"
108 declare_clippy_lint! {
109 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
110 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
112 /// **Why is this bad?** Gankro says:
114 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
115 /// pointers and indirection.
116 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
118 /// > "only" amortized for push/pop, should be faster in the general case for
119 /// almost every possible
120 /// > workload, and isn't even amortized at all if you can predict the capacity
123 /// > `LinkedList`s are only really good if you're doing a lot of merging or
124 /// splitting of lists.
125 /// > This is because they can just mangle some pointers instead of actually
126 /// copying the data. Even
127 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
128 /// can still be better
129 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
131 /// **Known problems:** False positives – the instances where using a
132 /// `LinkedList` makes sense are few and far between, but they can still happen.
136 /// let x = LinkedList::new();
140 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
143 declare_clippy_lint! {
144 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
146 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
149 /// **Known problems:** None.
153 /// fn foo(bar: &Box<T>) { ... }
159 /// fn foo(bar: &T) { ... }
163 "a borrow of a boxed type"
166 declare_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX]);
168 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Types {
169 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
170 // Skip trait implementations; see issue #605.
171 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find_by_hir_id(cx.tcx.hir().get_parent_item(id)) {
172 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
177 check_fn_decl(cx, decl);
180 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
181 check_ty(cx, &field.ty, false);
184 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
186 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
187 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
192 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
193 if let Some(ref ty) = local.ty {
194 check_ty(cx, ty, true);
199 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
200 for input in &decl.inputs {
201 check_ty(cx, input, false);
204 if let FunctionRetTy::Return(ref ty) = decl.output {
205 check_ty(cx, ty, false);
209 /// Checks if `qpath` has last segment with type parameter matching `path`
210 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
211 let last = last_path_segment(qpath);
213 if let Some(ref params) = last.args;
214 if !params.parenthesized;
215 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
216 GenericArg::Type(ty) => Some(ty),
219 if let TyKind::Path(ref qpath) = ty.node;
220 if let Some(did) = cx.tables.qpath_res(qpath, ty.hir_id).opt_def_id();
221 if match_def_path(cx, did, path);
229 /// Recursively check for `TypePass` lints in the given type. Stop at the first
232 /// The parameter `is_local` distinguishes the context of the type; types from
233 /// local bindings should only be checked for the `BORROWED_BOX` lint.
234 #[allow(clippy::too_many_lines)]
235 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
236 if in_macro_or_desugar(hir_ty.span) {
240 TyKind::Path(ref qpath) if !is_local => {
241 let hir_id = hir_ty.hir_id;
242 let res = cx.tables.qpath_res(qpath, hir_id);
243 if let Some(def_id) = res.opt_def_id() {
244 if Some(def_id) == cx.tcx.lang_items().owned_box() {
245 if match_type_parameter(cx, qpath, &paths::VEC) {
250 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
251 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
253 return; // don't recurse into the type
255 } else if match_def_path(cx, def_id, &paths::VEC) {
257 // Get the _ part of Vec<_>
258 if let Some(ref last) = last_path_segment(qpath).args;
259 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
260 GenericArg::Type(ty) => Some(ty),
263 // ty is now _ at this point
264 if let TyKind::Path(ref ty_qpath) = ty.node;
265 let res = cx.tables.qpath_res(ty_qpath, ty.hir_id);
266 if let Some(def_id) = res.opt_def_id();
267 if Some(def_id) == cx.tcx.lang_items().owned_box();
268 // At this point, we know ty is Box<T>, now get T
269 if let Some(ref last) = last_path_segment(ty_qpath).args;
270 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
271 GenericArg::Type(ty) => Some(ty),
275 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
276 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
281 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
283 format!("Vec<{}>", ty_ty),
284 Applicability::MachineApplicable,
286 return; // don't recurse into the type
290 } else if match_def_path(cx, def_id, &paths::OPTION) {
291 if match_type_parameter(cx, qpath, &paths::OPTION) {
296 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
297 enum if you need to distinguish all 3 cases",
299 return; // don't recurse into the type
301 } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
306 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
307 "a VecDeque might work",
309 return; // don't recurse into the type
313 QPath::Resolved(Some(ref ty), ref p) => {
314 check_ty(cx, ty, is_local);
315 for ty in p.segments.iter().flat_map(|seg| {
318 .map_or_else(|| [].iter(), |params| params.args.iter())
319 .filter_map(|arg| match arg {
320 GenericArg::Type(ty) => Some(ty),
324 check_ty(cx, ty, is_local);
327 QPath::Resolved(None, ref p) => {
328 for ty in p.segments.iter().flat_map(|seg| {
331 .map_or_else(|| [].iter(), |params| params.args.iter())
332 .filter_map(|arg| match arg {
333 GenericArg::Type(ty) => Some(ty),
337 check_ty(cx, ty, is_local);
340 QPath::TypeRelative(ref ty, ref seg) => {
341 check_ty(cx, ty, is_local);
342 if let Some(ref params) = seg.args {
343 for ty in params.args.iter().filter_map(|arg| match arg {
344 GenericArg::Type(ty) => Some(ty),
347 check_ty(cx, ty, is_local);
353 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
355 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
356 check_ty(cx, ty, is_local)
358 TyKind::Tup(ref tys) => {
360 check_ty(cx, ty, is_local);
367 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
368 match mut_ty.ty.node {
369 TyKind::Path(ref qpath) => {
370 let hir_id = mut_ty.ty.hir_id;
371 let def = cx.tables.qpath_res(qpath, hir_id);
373 if let Some(def_id) = def.opt_def_id();
374 if Some(def_id) == cx.tcx.lang_items().owned_box();
375 if let QPath::Resolved(None, ref path) = *qpath;
376 if let [ref bx] = *path.segments;
377 if let Some(ref params) = bx.args;
378 if !params.parenthesized;
379 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
380 GenericArg::Type(ty) => Some(ty),
384 if is_any_trait(inner) {
385 // Ignore `Box<Any>` types; see issue #1884 for details.
389 let ltopt = if lt.is_elided() {
392 format!("{} ", lt.name.ident().as_str())
394 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
399 let mut applicability = Applicability::MachineApplicable;
404 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
410 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
412 Applicability::Unspecified,
414 return; // don't recurse into the type
417 check_ty(cx, &mut_ty.ty, is_local);
419 _ => check_ty(cx, &mut_ty.ty, is_local),
423 // Returns true if given type is `Any` trait.
424 fn is_any_trait(t: &hir::Ty) -> bool {
426 if let TyKind::TraitObject(ref traits, _) = t.node;
427 if traits.len() >= 1;
428 // Only Send/Sync can be used as additional traits, so it is enough to
429 // check only the first trait.
430 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
439 declare_clippy_lint! {
440 /// **What it does:** Checks for binding a unit value.
442 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
443 /// binding one is kind of pointless.
445 /// **Known problems:** None.
455 "creating a let binding to a value of unit type, which usually can't be used afterwards"
458 declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
460 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnitValue {
461 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
462 if let StmtKind::Local(ref local) = stmt.node {
463 if is_unit(cx.tables.pat_ty(&local.pat)) {
464 if in_external_macro(cx.sess(), stmt.span) || in_macro_or_desugar(local.pat.span) {
467 if higher::is_from_for_desugar(local) {
475 "this let-binding has unit value. Consider omitting `let {} =`",
476 snippet(cx, local.pat.span, "..")
484 declare_clippy_lint! {
485 /// **What it does:** Checks for comparisons to unit.
487 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
488 /// clumsily written constant. Mostly this happens when someone accidentally
489 /// adds semicolons at the end of the operands.
491 /// **Known problems:** None.
519 "comparing unit values"
522 declare_lint_pass!(UnitCmp => [UNIT_CMP]);
524 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
525 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
526 if in_macro_or_desugar(expr.span) {
529 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
531 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
532 let result = match op {
533 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
541 "{}-comparison of unit values detected. This will always be {}",
551 declare_clippy_lint! {
552 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
553 /// unit literal (`()`).
555 /// **Why is this bad?** This is likely the result of an accidental semicolon.
557 /// **Known problems:** None.
568 "passing unit to a function"
571 declare_lint_pass!(UnitArg => [UNIT_ARG]);
573 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
574 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
575 if in_macro_or_desugar(expr.span) {
579 // apparently stuff in the desugaring of `?` can trigger this
580 // so check for that here
581 // only the calls to `Try::from_error` is marked as desugared,
582 // so we need to check both the current Expr and its parent.
583 if is_questionmark_desugar_marked_call(expr) {
587 let map = &cx.tcx.hir();
588 let opt_parent_node = map.find_by_hir_id(map.get_parent_node_by_hir_id(expr.hir_id));
589 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
590 if is_questionmark_desugar_marked_call(parent_expr);
597 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
599 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
600 if let ExprKind::Match(.., match_source) = &arg.node {
601 if *match_source == MatchSource::TryDesugar {
610 "passing a unit value to a function",
611 "if you intended to pass a unit value, use a unit literal instead",
613 Applicability::MachineApplicable,
623 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
624 use syntax_pos::hygiene::CompilerDesugaringKind;
625 if let ExprKind::Call(ref callee, _) = expr.node {
626 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
632 fn is_unit(ty: Ty<'_>) -> bool {
634 ty::Tuple(slice) if slice.is_empty() => true,
639 fn is_unit_literal(expr: &Expr) -> bool {
641 ExprKind::Tup(ref slice) if slice.is_empty() => true,
646 declare_clippy_lint! {
647 /// **What it does:** Checks for casts from any numerical to a float type where
648 /// the receiving type cannot store all values from the original type without
649 /// rounding errors. This possible rounding is to be expected, so this lint is
650 /// `Allow` by default.
652 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
653 /// or any 64-bit integer to `f64`.
655 /// **Why is this bad?** It's not bad at all. But in some applications it can be
656 /// helpful to know where precision loss can take place. This lint can help find
657 /// those places in the code.
659 /// **Known problems:** None.
663 /// let x = u64::MAX;
666 pub CAST_PRECISION_LOSS,
668 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
671 declare_clippy_lint! {
672 /// **What it does:** Checks for casts from a signed to an unsigned numerical
673 /// type. In this case, negative values wrap around to large positive values,
674 /// which can be quite surprising in practice. However, as the cast works as
675 /// defined, this lint is `Allow` by default.
677 /// **Why is this bad?** Possibly surprising results. You can activate this lint
678 /// as a one-time check to see where numerical wrapping can arise.
680 /// **Known problems:** None.
685 /// y as u128 // will return 18446744073709551615
689 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
692 declare_clippy_lint! {
693 /// **What it does:** Checks for on casts between numerical types that may
694 /// truncate large values. This is expected behavior, so the cast is `Allow` by
697 /// **Why is this bad?** In some problem domains, it is good practice to avoid
698 /// truncation. This lint can be activated to help assess where additional
699 /// checks could be beneficial.
701 /// **Known problems:** None.
705 /// fn as_u8(x: u64) -> u8 {
709 pub CAST_POSSIBLE_TRUNCATION,
711 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
714 declare_clippy_lint! {
715 /// **What it does:** Checks for casts from an unsigned type to a signed type of
716 /// the same size. Performing such a cast is a 'no-op' for the compiler,
717 /// i.e., nothing is changed at the bit level, and the binary representation of
718 /// the value is reinterpreted. This can cause wrapping if the value is too big
719 /// for the target signed type. However, the cast works as defined, so this lint
720 /// is `Allow` by default.
722 /// **Why is this bad?** While such a cast is not bad in itself, the results can
723 /// be surprising when this is not the intended behavior, as demonstrated by the
726 /// **Known problems:** None.
730 /// u32::MAX as i32 // will yield a value of `-1`
732 pub CAST_POSSIBLE_WRAP,
734 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
737 declare_clippy_lint! {
738 /// **What it does:** Checks for on casts between numerical types that may
739 /// be replaced by safe conversion functions.
741 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
742 /// conversions, including silently lossy conversions. Conversion functions such
743 /// as `i32::from` will only perform lossless conversions. Using the conversion
744 /// functions prevents conversions from turning into silent lossy conversions if
745 /// the types of the input expressions ever change, and make it easier for
746 /// people reading the code to know that the conversion is lossless.
748 /// **Known problems:** None.
752 /// fn as_u64(x: u8) -> u64 {
757 /// Using `::from` would look like this:
760 /// fn as_u64(x: u8) -> u64 {
766 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
769 declare_clippy_lint! {
770 /// **What it does:** Checks for casts to the same type.
772 /// **Why is this bad?** It's just unnecessary.
774 /// **Known problems:** None.
778 /// let _ = 2i32 as i32
780 pub UNNECESSARY_CAST,
782 "cast to the same type, e.g., `x as i32` where `x: i32`"
785 declare_clippy_lint! {
786 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
787 /// more-strictly-aligned pointer
789 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
792 /// **Known problems:** None.
796 /// let _ = (&1u8 as *const u8) as *const u16;
797 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
799 pub CAST_PTR_ALIGNMENT,
801 "cast from a pointer to a more-strictly-aligned pointer"
804 declare_clippy_lint! {
805 /// **What it does:** Checks for casts of function pointers to something other than usize
807 /// **Why is this bad?**
808 /// Casting a function pointer to anything other than usize/isize is not portable across
809 /// architectures, because you end up losing bits if the target type is too small or end up with a
810 /// bunch of extra bits that waste space and add more instructions to the final binary than
811 /// strictly necessary for the problem
813 /// Casting to isize also doesn't make sense since there are no signed addresses.
819 /// fn fun() -> i32 { 1 }
820 /// let a = fun as i64;
823 /// fn fun2() -> i32 { 1 }
824 /// let a = fun2 as usize;
826 pub FN_TO_NUMERIC_CAST,
828 "casting a function pointer to a numeric type other than usize"
831 declare_clippy_lint! {
832 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
835 /// **Why is this bad?**
836 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
837 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
838 /// a comment) to perform the truncation.
844 /// fn fn1() -> i16 {
847 /// let _ = fn1 as i32;
849 /// // Better: Cast to usize first, then comment with the reason for the truncation
850 /// fn fn2() -> i16 {
853 /// let fn_ptr = fn2 as usize;
854 /// let fn_ptr_truncated = fn_ptr as i32;
856 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
858 "casting a function pointer to a numeric type not wide enough to store the address"
861 /// Returns the size in bits of an integral type.
862 /// Will return 0 if the type is not an int or uint variant
863 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
865 ty::Int(i) => match i {
866 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
873 ty::Uint(i) => match i {
874 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
885 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
887 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
892 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
893 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
894 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
895 let arch_dependent_str = "on targets with 64-bit wide pointers ";
896 let from_nbits_str = if arch_dependent {
898 } else if is_isize_or_usize(cast_from) {
899 "32 or 64".to_owned()
901 int_ty_to_nbits(cast_from, cx.tcx).to_string()
908 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
909 is only {4} bits wide)",
911 if cast_to_f64 { "f64" } else { "f32" },
912 if arch_dependent { arch_dependent_str } else { "" },
919 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
920 if let ExprKind::Binary(_, _, _) = op.node {
921 if snip.starts_with('(') && snip.ends_with(')') {
928 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
929 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
930 if in_constant(cx, expr.hir_id) {
933 // The suggestion is to use a function call, so if the original expression
934 // has parens on the outside, they are no longer needed.
935 let mut applicability = Applicability::MachineApplicable;
936 let opt = snippet_opt(cx, op.span);
937 let sugg = if let Some(ref snip) = opt {
938 if should_strip_parens(op, snip) {
939 &snip[1..snip.len() - 1]
944 applicability = Applicability::HasPlaceholders;
953 "casting {} to {} may become silently lossy if you later change the type",
957 format!("{}::from({})", cast_to, sugg),
968 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
969 if !cast_from.is_signed() || cast_to.is_signed() {
973 // don't lint for positive constants
974 let const_val = constant(cx, &cx.tables, op);
976 if let Some((const_val, _)) = const_val;
977 if let Constant::Int(n) = const_val;
978 if let ty::Int(ity) = cast_from.sty;
979 if sext(cx.tcx, n, ity) >= 0;
989 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
993 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
994 let arch_64_suffix = " on targets with 64-bit wide pointers";
995 let arch_32_suffix = " on targets with 32-bit wide pointers";
996 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
997 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
998 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
999 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1000 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1001 (true, true) | (false, false) => (
1002 to_nbits < from_nbits,
1004 to_nbits == from_nbits && cast_unsigned_to_signed,
1014 to_nbits <= 32 && cast_unsigned_to_signed,
1020 cast_unsigned_to_signed,
1021 if from_nbits == 64 {
1028 if span_truncation {
1031 CAST_POSSIBLE_TRUNCATION,
1034 "casting {} to {} may truncate the value{}",
1037 match suffix_truncation {
1038 ArchSuffix::_32 => arch_32_suffix,
1039 ArchSuffix::_64 => arch_64_suffix,
1040 ArchSuffix::None => "",
1051 "casting {} to {} may wrap around the value{}",
1055 ArchSuffix::_32 => arch_32_suffix,
1056 ArchSuffix::_64 => arch_64_suffix,
1057 ArchSuffix::None => "",
1064 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1065 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1066 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1067 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1068 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1070 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1074 declare_lint_pass!(Casts => [
1075 CAST_PRECISION_LOSS,
1077 CAST_POSSIBLE_TRUNCATION,
1083 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1086 // Check if the given type is either `core::ffi::c_void` or
1087 // one of the platform specific `libc::<platform>::c_void` of libc.
1088 fn is_c_void(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1089 if let ty::Adt(adt, _) = ty.sty {
1090 let names = cx.get_def_path(adt.did);
1092 if names.is_empty() {
1095 if names[0] == sym!(libc) || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
1102 /// Returns the mantissa bits wide of a fp type.
1103 /// Will return 0 if the type is not a fp
1104 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1106 ty::Float(FloatTy::F32) => 23,
1107 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1112 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
1113 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1114 if in_macro_or_desugar(expr.span) {
1117 if let ExprKind::Cast(ref ex, _) = expr.node {
1118 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1119 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1120 if let ExprKind::Lit(ref lit) = ex.node {
1121 use syntax::ast::{LitIntType, LitKind};
1122 if let LitKind::Int(n, _) = lit.node {
1123 if cast_to.is_floating_point() {
1124 let from_nbits = 128 - n.leading_zeros();
1125 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1126 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1131 &format!("casting integer literal to {} is unnecessary", cast_to),
1133 format!("{}_{}", n, cast_to),
1134 Applicability::MachineApplicable,
1141 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1143 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1149 "casting to the same type is unnecessary (`{}` -> `{}`)",
1157 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1158 match (cast_from.is_integral(), cast_to.is_integral()) {
1160 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1161 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1166 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1167 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1169 if from_nbits < to_nbits {
1170 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1176 CAST_POSSIBLE_TRUNCATION,
1178 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1180 if !cast_to.is_signed() {
1185 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1190 check_loss_of_sign(cx, expr, ex, cast_from, cast_to);
1191 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1192 check_lossless(cx, expr, ex, cast_from, cast_to);
1195 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1198 CAST_POSSIBLE_TRUNCATION,
1200 "casting f64 to f32 may truncate the value",
1203 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1204 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1211 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1212 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1213 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1214 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1215 if from_align < to_align;
1216 // with c_void, we inherently need to trust the user
1217 if !is_c_void(cx, from_ptr_ty.ty);
1223 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1231 fn lint_fn_to_numeric_cast(
1232 cx: &LateContext<'_, '_>,
1238 // We only want to check casts to `ty::Uint` or `ty::Int`
1240 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1243 match cast_from.sty {
1244 ty::FnDef(..) | ty::FnPtr(_) => {
1245 let mut applicability = Applicability::MachineApplicable;
1246 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1248 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1249 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1252 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1255 "casting function pointer `{}` to `{}`, which truncates the value",
1256 from_snippet, cast_to
1259 format!("{} as usize", from_snippet),
1262 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1267 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1269 format!("{} as usize", from_snippet),
1278 declare_clippy_lint! {
1279 /// **What it does:** Checks for types used in structs, parameters and `let`
1280 /// declarations above a certain complexity threshold.
1282 /// **Why is this bad?** Too complex types make the code less readable. Consider
1283 /// using a `type` definition to simplify them.
1285 /// **Known problems:** None.
1290 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1293 pub TYPE_COMPLEXITY,
1295 "usage of very complex types that might be better factored into `type` definitions"
1298 pub struct TypeComplexity {
1302 impl TypeComplexity {
1303 pub fn new(threshold: u64) -> Self {
1308 impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
1310 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexity {
1313 cx: &LateContext<'a, 'tcx>,
1320 self.check_fndecl(cx, decl);
1323 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1324 // enum variants are also struct fields now
1325 self.check_type(cx, &field.ty);
1328 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1330 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1331 // functions, enums, structs, impls and traits are covered
1336 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1338 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1339 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1340 // methods with default impl are covered by check_fn
1345 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1347 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1348 // methods are covered by check_fn
1353 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1354 if let Some(ref ty) = local.ty {
1355 self.check_type(cx, ty);
1360 impl<'a, 'tcx> TypeComplexity {
1361 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1362 for arg in &decl.inputs {
1363 self.check_type(cx, arg);
1365 if let Return(ref ty) = decl.output {
1366 self.check_type(cx, ty);
1370 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1371 if in_macro_or_desugar(ty.span) {
1375 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1376 visitor.visit_ty(ty);
1380 if score > self.threshold {
1385 "very complex type used. Consider factoring parts into `type` definitions",
1391 /// Walks a type and assigns a complexity score to it.
1392 struct TypeComplexityVisitor {
1393 /// total complexity score of the type
1395 /// current nesting level
1399 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1400 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1401 let (add_score, sub_nest) = match ty.node {
1402 // _, &x and *x have only small overhead; don't mess with nesting level
1403 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1405 // the "normal" components of a type: named types, arrays/tuples
1406 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1408 // function types bring a lot of overhead
1409 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1411 TyKind::TraitObject(ref param_bounds, _) => {
1412 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1413 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1414 GenericParamKind::Lifetime { .. } => true,
1418 if has_lifetime_parameters {
1419 // complex trait bounds like A<'a, 'b>
1422 // simple trait bounds like A + B
1429 self.score += add_score;
1430 self.nest += sub_nest;
1432 self.nest -= sub_nest;
1434 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1435 NestedVisitorMap::None
1439 declare_clippy_lint! {
1440 /// **What it does:** Checks for expressions where a character literal is cast
1441 /// to `u8` and suggests using a byte literal instead.
1443 /// **Why is this bad?** In general, casting values to smaller types is
1444 /// error-prone and should be avoided where possible. In the particular case of
1445 /// converting a character literal to u8, it is easy to avoid by just using a
1446 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1447 /// than `'a' as u8`.
1449 /// **Known problems:** None.
1456 /// A better version, using the byte literal:
1463 "casting a character literal to u8"
1466 declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
1468 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1469 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1470 use syntax::ast::LitKind;
1472 if let ExprKind::Cast(ref e, _) = expr.node {
1473 if let ExprKind::Lit(ref l) = e.node {
1474 if let LitKind::Char(_) = l.node {
1475 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro_or_desugar(expr.span) {
1476 let msg = "casting character literal to u8. `char`s \
1477 are 4 bytes wide in rust, so casting to u8 \
1480 "Consider using a byte literal instead:\nb{}",
1481 snippet(cx, e.span, "'x'")
1483 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1491 declare_clippy_lint! {
1492 /// **What it does:** Checks for comparisons where one side of the relation is
1493 /// either the minimum or maximum value for its type and warns if it involves a
1494 /// case that is always true or always false. Only integer and boolean types are
1497 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1498 /// that is is possible for `x` to be less than the minimum. Expressions like
1499 /// `max < x` are probably mistakes.
1501 /// **Known problems:** For `usize` the size of the current compile target will
1502 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1503 /// a comparison to detect target pointer width will trigger this lint. One can
1504 /// use `mem::sizeof` and compare its value or conditional compilation
1506 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1511 /// let vec: Vec<isize> = vec![];
1512 /// if vec.len() <= 0 {}
1513 /// if 100 > std::i32::MAX {}
1515 pub ABSURD_EXTREME_COMPARISONS,
1517 "a comparison with a maximum or minimum value that is always true or false"
1520 declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
1527 struct ExtremeExpr<'a> {
1532 enum AbsurdComparisonResult {
1535 InequalityImpossible,
1538 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1539 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1540 let precast_ty = cx.tables.expr_ty(cast_exp);
1541 let cast_ty = cx.tables.expr_ty(expr);
1543 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1549 fn detect_absurd_comparison<'a, 'tcx>(
1550 cx: &LateContext<'a, 'tcx>,
1554 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1555 use crate::types::AbsurdComparisonResult::*;
1556 use crate::types::ExtremeType::*;
1557 use crate::utils::comparisons::*;
1559 // absurd comparison only makes sense on primitive types
1560 // primitive types don't implement comparison operators with each other
1561 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1565 // comparisons between fix sized types and target sized types are considered unanalyzable
1566 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1570 let normalized = normalize_comparison(op, lhs, rhs);
1571 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1577 let lx = detect_extreme_expr(cx, normalized_lhs);
1578 let rx = detect_extreme_expr(cx, normalized_rhs);
1583 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1584 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1590 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1591 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1592 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1593 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1597 Rel::Ne | Rel::Eq => return None,
1601 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1602 use crate::types::ExtremeType::*;
1604 let ty = cx.tables.expr_ty(expr);
1606 let cv = constant(cx, cx.tables, expr)?.0;
1608 let which = match (&ty.sty, cv) {
1609 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1610 (&ty::Int(ity), Constant::Int(i))
1611 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1616 (&ty::Bool, Constant::Bool(true)) => Maximum,
1617 (&ty::Int(ity), Constant::Int(i))
1618 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1622 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1626 Some(ExtremeExpr { which, expr })
1629 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1630 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1631 use crate::types::AbsurdComparisonResult::*;
1632 use crate::types::ExtremeType::*;
1634 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1635 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1636 if !in_macro_or_desugar(expr.span) {
1637 let msg = "this comparison involving the minimum or maximum element for this \
1638 type contains a case that is always true or always false";
1640 let conclusion = match result {
1641 AlwaysFalse => "this comparison is always false".to_owned(),
1642 AlwaysTrue => "this comparison is always true".to_owned(),
1643 InequalityImpossible => format!(
1644 "the case where the two sides are not equal never occurs, consider using {} == {} \
1646 snippet(cx, lhs.span, "lhs"),
1647 snippet(cx, rhs.span, "rhs")
1652 "because {} is the {} value for this type, {}",
1653 snippet(cx, culprit.expr.span, "x"),
1654 match culprit.which {
1655 Minimum => "minimum",
1656 Maximum => "maximum",
1661 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1668 declare_clippy_lint! {
1669 /// **What it does:** Checks for comparisons where the relation is always either
1670 /// true or false, but where one side has been upcast so that the comparison is
1671 /// necessary. Only integer types are checked.
1673 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1674 /// will mistakenly imply that it is possible for `x` to be outside the range of
1677 /// **Known problems:**
1678 /// https://github.com/rust-lang/rust-clippy/issues/886
1682 /// let x : u8 = ...; (x as u32) > 300
1684 pub INVALID_UPCAST_COMPARISONS,
1686 "a comparison involving an upcast which is always true or false"
1689 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
1691 #[derive(Copy, Clone, Debug, Eq)]
1698 #[allow(clippy::cast_sign_loss)]
1699 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1702 } else if u > (i128::max_value() as u128) {
1710 impl PartialEq for FullInt {
1711 fn eq(&self, other: &Self) -> bool {
1712 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1716 impl PartialOrd for FullInt {
1717 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1718 Some(match (self, other) {
1719 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1720 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1721 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1722 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1726 impl Ord for FullInt {
1727 fn cmp(&self, other: &Self) -> Ordering {
1728 self.partial_cmp(other)
1729 .expect("partial_cmp for FullInt can never return None")
1733 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1736 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1737 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1738 let cast_ty = cx.tables.expr_ty(expr);
1739 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1740 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1743 match pre_cast_ty.sty {
1744 ty::Int(int_ty) => Some(match int_ty {
1746 FullInt::S(i128::from(i8::min_value())),
1747 FullInt::S(i128::from(i8::max_value())),
1750 FullInt::S(i128::from(i16::min_value())),
1751 FullInt::S(i128::from(i16::max_value())),
1754 FullInt::S(i128::from(i32::min_value())),
1755 FullInt::S(i128::from(i32::max_value())),
1758 FullInt::S(i128::from(i64::min_value())),
1759 FullInt::S(i128::from(i64::max_value())),
1761 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1763 FullInt::S(isize::min_value() as i128),
1764 FullInt::S(isize::max_value() as i128),
1767 ty::Uint(uint_ty) => Some(match uint_ty {
1769 FullInt::U(u128::from(u8::min_value())),
1770 FullInt::U(u128::from(u8::max_value())),
1773 FullInt::U(u128::from(u16::min_value())),
1774 FullInt::U(u128::from(u16::max_value())),
1777 FullInt::U(u128::from(u32::min_value())),
1778 FullInt::U(u128::from(u32::max_value())),
1781 FullInt::U(u128::from(u64::min_value())),
1782 FullInt::U(u128::from(u64::max_value())),
1784 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1786 FullInt::U(usize::min_value() as u128),
1787 FullInt::U(usize::max_value() as u128),
1797 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1798 let val = constant(cx, cx.tables, expr)?.0;
1799 if let Constant::Int(const_int) = val {
1800 match cx.tables.expr_ty(expr).sty {
1801 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1802 ty::Uint(_) => Some(FullInt::U(const_int)),
1810 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1811 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1814 INVALID_UPCAST_COMPARISONS,
1817 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1818 snippet(cx, cast_val.span, "the expression"),
1819 if always { "true" } else { "false" },
1825 fn upcast_comparison_bounds_err<'a, 'tcx>(
1826 cx: &LateContext<'a, 'tcx>,
1828 rel: comparisons::Rel,
1829 lhs_bounds: Option<(FullInt, FullInt)>,
1834 use crate::utils::comparisons::*;
1836 if let Some((lb, ub)) = lhs_bounds {
1837 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1838 if rel == Rel::Eq || rel == Rel::Ne {
1839 if norm_rhs_val < lb || norm_rhs_val > ub {
1840 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1842 } else if match rel {
1857 Rel::Eq | Rel::Ne => unreachable!(),
1859 err_upcast_comparison(cx, span, lhs, true)
1860 } else if match rel {
1875 Rel::Eq | Rel::Ne => unreachable!(),
1877 err_upcast_comparison(cx, span, lhs, false)
1883 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1884 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1885 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1886 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1887 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1893 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1894 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1896 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1897 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1902 declare_clippy_lint! {
1903 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1904 /// over different hashers and implicitly defaulting to the default hashing
1905 /// algorithm (SipHash).
1907 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1910 /// **Known problems:** Suggestions for replacing constructors can contain
1911 /// false-positives. Also applying suggestions can require modification of other
1912 /// pieces of code, possibly including external crates.
1916 /// # use std::collections::HashMap;
1917 /// # use std::hash::Hash;
1918 /// # trait Serialize {};
1919 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
1921 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
1923 pub IMPLICIT_HASHER,
1925 "missing generalization over different hashers"
1928 declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
1930 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1931 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
1932 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1933 use syntax_pos::BytePos;
1935 fn suggestion<'a, 'tcx>(
1936 cx: &LateContext<'a, 'tcx>,
1937 db: &mut DiagnosticBuilder<'_>,
1938 generics_span: Span,
1939 generics_suggestion_span: Span,
1940 target: &ImplicitHasherType<'_>,
1941 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1943 let generics_snip = snippet(cx, generics_span, "");
1945 let generics_snip = if generics_snip.is_empty() {
1948 &generics_snip[1..generics_snip.len() - 1]
1953 "consider adding a type parameter".to_string(),
1956 generics_suggestion_span,
1958 "<{}{}S: ::std::hash::BuildHasher{}>",
1960 if generics_snip.is_empty() { "" } else { ", " },
1961 if vis.suggestions.is_empty() {
1964 // request users to add `Default` bound so that generic constructors can be used
1971 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1976 if !vis.suggestions.is_empty() {
1977 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1981 if !cx.access_levels.is_exported(item.hir_id) {
1986 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1987 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1990 for target in &vis.found {
1991 if differing_macro_contexts(item.span, target.span()) {
1995 let generics_suggestion_span = generics.span.substitute_dummy({
1996 let pos = snippet_opt(cx, item.span.until(target.span()))
1997 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
1998 if let Some(pos) = pos {
1999 Span::new(pos, pos, item.span.data().ctxt)
2005 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2006 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2007 ctr_vis.visit_impl_item(item);
2015 "impl for `{}` should be generalized over different hashers",
2019 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2024 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2025 let body = cx.tcx.hir().body(body_id);
2027 for ty in &decl.inputs {
2028 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2031 for target in &vis.found {
2032 let generics_suggestion_span = generics.span.substitute_dummy({
2033 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2035 let i = snip.find("fn")?;
2036 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2038 .expect("failed to create span for type parameters");
2039 Span::new(pos, pos, item.span.data().ctxt)
2042 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2043 ctr_vis.visit_body(body);
2050 "parameter of type `{}` should be generalized over different hashers",
2054 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2065 enum ImplicitHasherType<'tcx> {
2066 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2067 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2070 impl<'tcx> ImplicitHasherType<'tcx> {
2071 /// Checks that `ty` is a target type without a BuildHasher.
2072 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2073 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2074 let params: Vec<_> = path
2082 .filter_map(|arg| match arg {
2083 GenericArg::Type(ty) => Some(ty),
2087 let params_len = params.len();
2089 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2091 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2092 Some(ImplicitHasherType::HashMap(
2095 snippet(cx, params[0].span, "K"),
2096 snippet(cx, params[1].span, "V"),
2098 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2099 Some(ImplicitHasherType::HashSet(
2102 snippet(cx, params[0].span, "T"),
2112 fn type_name(&self) -> &'static str {
2114 ImplicitHasherType::HashMap(..) => "HashMap",
2115 ImplicitHasherType::HashSet(..) => "HashSet",
2119 fn type_arguments(&self) -> String {
2121 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2122 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2126 fn ty(&self) -> Ty<'tcx> {
2128 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2132 fn span(&self) -> Span {
2134 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2139 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2140 cx: &'a LateContext<'a, 'tcx>,
2141 found: Vec<ImplicitHasherType<'tcx>>,
2144 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2145 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2146 Self { cx, found: vec![] }
2150 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2151 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2152 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2153 self.found.push(target);
2159 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2160 NestedVisitorMap::None
2164 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2165 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2166 cx: &'a LateContext<'a, 'tcx>,
2167 body: &'a TypeckTables<'tcx>,
2168 target: &'b ImplicitHasherType<'tcx>,
2169 suggestions: BTreeMap<Span, String>,
2172 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2173 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2178 suggestions: BTreeMap::new(),
2183 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2184 fn visit_body(&mut self, body: &'tcx Body) {
2185 let prev_body = self.body;
2186 self.body = self.cx.tcx.body_tables(body.id());
2187 walk_body(self, body);
2188 self.body = prev_body;
2191 fn visit_expr(&mut self, e: &'tcx Expr) {
2193 if let ExprKind::Call(ref fun, ref args) = e.node;
2194 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2195 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2197 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2201 if match_path(ty_path, &paths::HASHMAP) {
2202 if method.ident.name == sym!(new) {
2204 .insert(e.span, "HashMap::default()".to_string());
2205 } else if method.ident.name == sym!(with_capacity) {
2206 self.suggestions.insert(
2209 "HashMap::with_capacity_and_hasher({}, Default::default())",
2210 snippet(self.cx, args[0].span, "capacity"),
2214 } else if match_path(ty_path, &paths::HASHSET) {
2215 if method.ident.name == sym!(new) {
2217 .insert(e.span, "HashSet::default()".to_string());
2218 } else if method.ident.name == sym!(with_capacity) {
2219 self.suggestions.insert(
2222 "HashSet::with_capacity_and_hasher({}, Default::default())",
2223 snippet(self.cx, args[0].span, "capacity"),
2234 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2235 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2239 declare_clippy_lint! {
2240 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2242 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2243 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2246 /// **Known problems:** None.
2252 /// *(r as *const _ as *mut _) += 1;
2257 /// Instead consider using interior mutability types.
2260 /// use std::cell::UnsafeCell;
2262 /// fn x(r: &UnsafeCell<i32>) {
2268 pub CAST_REF_TO_MUT,
2270 "a cast of reference to a mutable pointer"
2273 declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
2275 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2276 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2278 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2279 if let ExprKind::Cast(e, t) = &e.node;
2280 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2281 if let ExprKind::Cast(e, t) = &e.node;
2282 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2283 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2289 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",