1 #![allow(rustc::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, impl_lint_pass};
15 use rustc_errors::Applicability;
16 use rustc_session::declare_tool_lint;
17 use rustc_target::spec::abi::Abi;
18 use rustc_typeck::hir_ty_to_ty;
19 use syntax::ast::{FloatTy, IntTy, LitFloatType, LitIntType, LitKind, UintTy};
20 use syntax::errors::DiagnosticBuilder;
21 use syntax::source_map::Span;
22 use syntax::symbol::{sym, Symbol};
23 use syntax_pos::hygiene::{ExpnKind, MacroKind};
25 use crate::consts::{constant, Constant};
26 use crate::utils::paths;
28 clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
29 match_path, method_chain_args, multispan_sugg, qpath_res, same_tys, sext, snippet, snippet_opt,
30 snippet_with_applicability, snippet_with_macro_callsite, span_help_and_lint, span_lint, span_lint_and_sugg,
31 span_lint_and_then, unsext,
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 /// # use std::collections::LinkedList;
140 /// let x: LinkedList<usize> = LinkedList::new();
144 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
147 declare_clippy_lint! {
148 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
150 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
153 /// **Known problems:** None.
157 /// fn foo(bar: &Box<T>) { ... }
163 /// fn foo(bar: &T) { ... }
167 "a borrow of a boxed type"
170 declare_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX]);
172 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Types {
173 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
174 // Skip trait implementations; see issue #605.
175 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
176 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.kind {
181 check_fn_decl(cx, decl);
184 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
185 check_ty(cx, &field.ty, false);
188 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
190 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
191 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
196 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
197 if let Some(ref ty) = local.ty {
198 check_ty(cx, ty, true);
203 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
204 for input in &decl.inputs {
205 check_ty(cx, input, false);
208 if let FunctionRetTy::Return(ref ty) = decl.output {
209 check_ty(cx, ty, false);
213 /// Checks if `qpath` has last segment with type parameter matching `path`
214 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
215 let last = last_path_segment(qpath);
217 if let Some(ref params) = last.args;
218 if !params.parenthesized;
219 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
220 GenericArg::Type(ty) => Some(ty),
223 if let TyKind::Path(ref qpath) = ty.kind;
224 if let Some(did) = qpath_res(cx, qpath, ty.hir_id).opt_def_id();
225 if match_def_path(cx, did, path);
233 /// Recursively check for `TypePass` lints in the given type. Stop at the first
236 /// The parameter `is_local` distinguishes the context of the type; types from
237 /// local bindings should only be checked for the `BORROWED_BOX` lint.
238 #[allow(clippy::too_many_lines)]
239 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
240 if hir_ty.span.from_expansion() {
244 TyKind::Path(ref qpath) if !is_local => {
245 let hir_id = hir_ty.hir_id;
246 let res = qpath_res(cx, qpath, hir_id);
247 if let Some(def_id) = res.opt_def_id() {
248 if Some(def_id) == cx.tcx.lang_items().owned_box() {
249 if match_type_parameter(cx, qpath, &paths::VEC) {
254 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
255 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
257 return; // don't recurse into the type
259 } else if cx.tcx.is_diagnostic_item(Symbol::intern("vec_type"), def_id) {
261 // Get the _ part of Vec<_>
262 if let Some(ref last) = last_path_segment(qpath).args;
263 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
264 GenericArg::Type(ty) => Some(ty),
267 // ty is now _ at this point
268 if let TyKind::Path(ref ty_qpath) = ty.kind;
269 let res = qpath_res(cx, ty_qpath, ty.hir_id);
270 if let Some(def_id) = res.opt_def_id();
271 if Some(def_id) == cx.tcx.lang_items().owned_box();
272 // At this point, we know ty is Box<T>, now get T
273 if let Some(ref last) = last_path_segment(ty_qpath).args;
274 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
275 GenericArg::Type(ty) => Some(ty),
279 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
280 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
285 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
287 format!("Vec<{}>", ty_ty),
288 Applicability::MachineApplicable,
290 return; // don't recurse into the type
294 } else if match_def_path(cx, def_id, &paths::OPTION) {
295 if match_type_parameter(cx, qpath, &paths::OPTION) {
300 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
301 enum if you need to distinguish all 3 cases",
303 return; // don't recurse into the type
305 } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
310 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
311 "a VecDeque might work",
313 return; // don't recurse into the type
317 QPath::Resolved(Some(ref ty), ref p) => {
318 check_ty(cx, ty, is_local);
319 for ty in p.segments.iter().flat_map(|seg| {
322 .map_or_else(|| [].iter(), |params| params.args.iter())
323 .filter_map(|arg| match arg {
324 GenericArg::Type(ty) => Some(ty),
328 check_ty(cx, ty, is_local);
331 QPath::Resolved(None, ref p) => {
332 for ty in p.segments.iter().flat_map(|seg| {
335 .map_or_else(|| [].iter(), |params| params.args.iter())
336 .filter_map(|arg| match arg {
337 GenericArg::Type(ty) => Some(ty),
341 check_ty(cx, ty, is_local);
344 QPath::TypeRelative(ref ty, ref seg) => {
345 check_ty(cx, ty, is_local);
346 if let Some(ref params) = seg.args {
347 for ty in params.args.iter().filter_map(|arg| match arg {
348 GenericArg::Type(ty) => Some(ty),
351 check_ty(cx, ty, is_local);
357 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
359 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
360 check_ty(cx, ty, is_local)
362 TyKind::Tup(ref tys) => {
364 check_ty(cx, ty, is_local);
371 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
372 match mut_ty.ty.kind {
373 TyKind::Path(ref qpath) => {
374 let hir_id = mut_ty.ty.hir_id;
375 let def = qpath_res(cx, qpath, hir_id);
377 if let Some(def_id) = def.opt_def_id();
378 if Some(def_id) == cx.tcx.lang_items().owned_box();
379 if let QPath::Resolved(None, ref path) = *qpath;
380 if let [ref bx] = *path.segments;
381 if let Some(ref params) = bx.args;
382 if !params.parenthesized;
383 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
384 GenericArg::Type(ty) => Some(ty),
388 if is_any_trait(inner) {
389 // Ignore `Box<Any>` types; see issue #1884 for details.
393 let ltopt = if lt.is_elided() {
396 format!("{} ", lt.name.ident().as_str())
398 let mutopt = if mut_ty.mutbl == Mutability::Mut {
403 let mut applicability = Applicability::MachineApplicable;
408 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
414 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
416 Applicability::Unspecified,
418 return; // don't recurse into the type
421 check_ty(cx, &mut_ty.ty, is_local);
423 _ => check_ty(cx, &mut_ty.ty, is_local),
427 // Returns true if given type is `Any` trait.
428 fn is_any_trait(t: &hir::Ty) -> bool {
430 if let TyKind::TraitObject(ref traits, _) = t.kind;
431 if traits.len() >= 1;
432 // Only Send/Sync can be used as additional traits, so it is enough to
433 // check only the first trait.
434 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
443 declare_clippy_lint! {
444 /// **What it does:** Checks for binding a unit value.
446 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
447 /// binding one is kind of pointless.
449 /// **Known problems:** None.
459 "creating a let binding to a value of unit type, which usually can't be used afterwards"
462 declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
464 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnitValue {
465 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
466 if let StmtKind::Local(ref local) = stmt.kind {
467 if is_unit(cx.tables.pat_ty(&local.pat)) {
468 if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
471 if higher::is_from_for_desugar(local) {
474 span_lint_and_then(cx, LET_UNIT_VALUE, stmt.span, "this let-binding has unit value", |db| {
475 if let Some(expr) = &local.init {
476 let snip = snippet_with_macro_callsite(cx, expr.span, "()");
479 "omit the `let` binding",
480 format!("{};", snip),
481 Applicability::MachineApplicable, // snippet
490 declare_clippy_lint! {
491 /// **What it does:** Checks for comparisons to unit. This includes all binary
492 /// comparisons (like `==` and `<`) and asserts.
494 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
495 /// clumsily written constant. Mostly this happens when someone accidentally
496 /// adds semicolons at the end of the operands.
498 /// **Known problems:** None.
529 /// assert_eq!({ foo(); }, { bar(); });
531 /// will always succeed
534 "comparing unit values"
537 declare_lint_pass!(UnitCmp => [UNIT_CMP]);
539 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
540 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
541 if expr.span.from_expansion() {
542 if let Some(callee) = expr.span.source_callee() {
543 if let ExpnKind::Macro(MacroKind::Bang, symbol) = callee.kind {
544 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
546 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
547 let result = match &*symbol.as_str() {
548 "assert_eq" | "debug_assert_eq" => "succeed",
549 "assert_ne" | "debug_assert_ne" => "fail",
557 "`{}` of unit values detected. This will always {}",
568 if let ExprKind::Binary(ref cmp, ref left, _) = expr.kind {
570 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
571 let result = match op {
572 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
580 "{}-comparison of unit values detected. This will always be {}",
590 declare_clippy_lint! {
591 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
592 /// unit literal (`()`).
594 /// **Why is this bad?** This is likely the result of an accidental semicolon.
596 /// **Known problems:** None.
607 "passing unit to a function"
610 declare_lint_pass!(UnitArg => [UNIT_ARG]);
612 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
613 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
614 if expr.span.from_expansion() {
618 // apparently stuff in the desugaring of `?` can trigger this
619 // so check for that here
620 // only the calls to `Try::from_error` is marked as desugared,
621 // so we need to check both the current Expr and its parent.
622 if is_questionmark_desugar_marked_call(expr) {
626 let map = &cx.tcx.hir();
627 let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
628 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
629 if is_questionmark_desugar_marked_call(parent_expr);
636 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
638 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
639 if let ExprKind::Match(.., match_source) = &arg.kind {
640 if *match_source == MatchSource::TryDesugar {
649 "passing a unit value to a function",
650 "if you intended to pass a unit value, use a unit literal instead",
652 Applicability::MachineApplicable,
662 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
663 use syntax_pos::hygiene::DesugaringKind;
664 if let ExprKind::Call(ref callee, _) = expr.kind {
665 callee.span.is_desugaring(DesugaringKind::QuestionMark)
671 fn is_unit(ty: Ty<'_>) -> bool {
673 ty::Tuple(slice) if slice.is_empty() => true,
678 fn is_unit_literal(expr: &Expr) -> bool {
680 ExprKind::Tup(ref slice) if slice.is_empty() => true,
685 declare_clippy_lint! {
686 /// **What it does:** Checks for casts from any numerical to a float type where
687 /// the receiving type cannot store all values from the original type without
688 /// rounding errors. This possible rounding is to be expected, so this lint is
689 /// `Allow` by default.
691 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
692 /// or any 64-bit integer to `f64`.
694 /// **Why is this bad?** It's not bad at all. But in some applications it can be
695 /// helpful to know where precision loss can take place. This lint can help find
696 /// those places in the code.
698 /// **Known problems:** None.
702 /// let x = std::u64::MAX;
705 pub CAST_PRECISION_LOSS,
707 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
710 declare_clippy_lint! {
711 /// **What it does:** Checks for casts from a signed to an unsigned numerical
712 /// type. In this case, negative values wrap around to large positive values,
713 /// which can be quite surprising in practice. However, as the cast works as
714 /// defined, this lint is `Allow` by default.
716 /// **Why is this bad?** Possibly surprising results. You can activate this lint
717 /// as a one-time check to see where numerical wrapping can arise.
719 /// **Known problems:** None.
724 /// y as u128; // will return 18446744073709551615
728 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
731 declare_clippy_lint! {
732 /// **What it does:** Checks for casts between numerical types that may
733 /// truncate large values. This is expected behavior, so the cast is `Allow` by
736 /// **Why is this bad?** In some problem domains, it is good practice to avoid
737 /// truncation. This lint can be activated to help assess where additional
738 /// checks could be beneficial.
740 /// **Known problems:** None.
744 /// fn as_u8(x: u64) -> u8 {
748 pub CAST_POSSIBLE_TRUNCATION,
750 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
753 declare_clippy_lint! {
754 /// **What it does:** Checks for casts from an unsigned type to a signed type of
755 /// the same size. Performing such a cast is a 'no-op' for the compiler,
756 /// i.e., nothing is changed at the bit level, and the binary representation of
757 /// the value is reinterpreted. This can cause wrapping if the value is too big
758 /// for the target signed type. However, the cast works as defined, so this lint
759 /// is `Allow` by default.
761 /// **Why is this bad?** While such a cast is not bad in itself, the results can
762 /// be surprising when this is not the intended behavior, as demonstrated by the
765 /// **Known problems:** None.
769 /// std::u32::MAX as i32; // will yield a value of `-1`
771 pub CAST_POSSIBLE_WRAP,
773 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
776 declare_clippy_lint! {
777 /// **What it does:** Checks for casts between numerical types that may
778 /// be replaced by safe conversion functions.
780 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
781 /// conversions, including silently lossy conversions. Conversion functions such
782 /// as `i32::from` will only perform lossless conversions. Using the conversion
783 /// functions prevents conversions from turning into silent lossy conversions if
784 /// the types of the input expressions ever change, and make it easier for
785 /// people reading the code to know that the conversion is lossless.
787 /// **Known problems:** None.
791 /// fn as_u64(x: u8) -> u64 {
796 /// Using `::from` would look like this:
799 /// fn as_u64(x: u8) -> u64 {
805 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
808 declare_clippy_lint! {
809 /// **What it does:** Checks for casts to the same type.
811 /// **Why is this bad?** It's just unnecessary.
813 /// **Known problems:** None.
817 /// let _ = 2i32 as i32;
819 pub UNNECESSARY_CAST,
821 "cast to the same type, e.g., `x as i32` where `x: i32`"
824 declare_clippy_lint! {
825 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
826 /// more-strictly-aligned pointer
828 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
831 /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
832 /// on the resulting pointer is fine.
836 /// let _ = (&1u8 as *const u8) as *const u16;
837 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
839 pub CAST_PTR_ALIGNMENT,
841 "cast from a pointer to a more-strictly-aligned pointer"
844 declare_clippy_lint! {
845 /// **What it does:** Checks for casts of function pointers to something other than usize
847 /// **Why is this bad?**
848 /// Casting a function pointer to anything other than usize/isize is not portable across
849 /// architectures, because you end up losing bits if the target type is too small or end up with a
850 /// bunch of extra bits that waste space and add more instructions to the final binary than
851 /// strictly necessary for the problem
853 /// Casting to isize also doesn't make sense since there are no signed addresses.
859 /// fn fun() -> i32 { 1 }
860 /// let a = fun as i64;
863 /// fn fun2() -> i32 { 1 }
864 /// let a = fun2 as usize;
866 pub FN_TO_NUMERIC_CAST,
868 "casting a function pointer to a numeric type other than usize"
871 declare_clippy_lint! {
872 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
875 /// **Why is this bad?**
876 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
877 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
878 /// a comment) to perform the truncation.
884 /// fn fn1() -> i16 {
887 /// let _ = fn1 as i32;
889 /// // Better: Cast to usize first, then comment with the reason for the truncation
890 /// fn fn2() -> i16 {
893 /// let fn_ptr = fn2 as usize;
894 /// let fn_ptr_truncated = fn_ptr as i32;
896 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
898 "casting a function pointer to a numeric type not wide enough to store the address"
901 /// Returns the size in bits of an integral type.
902 /// Will return 0 if the type is not an int or uint variant
903 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
905 ty::Int(i) => match i {
906 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
913 ty::Uint(i) => match i {
914 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
925 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
927 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
932 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
933 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
934 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
935 let arch_dependent_str = "on targets with 64-bit wide pointers ";
936 let from_nbits_str = if arch_dependent {
938 } else if is_isize_or_usize(cast_from) {
939 "32 or 64".to_owned()
941 int_ty_to_nbits(cast_from, cx.tcx).to_string()
948 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
949 is only {4} bits wide)",
951 if cast_to_f64 { "f64" } else { "f32" },
952 if arch_dependent { arch_dependent_str } else { "" },
959 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
960 if let ExprKind::Binary(_, _, _) = op.kind {
961 if snip.starts_with('(') && snip.ends_with(')') {
968 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
969 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
970 if in_constant(cx, expr.hir_id) {
973 // The suggestion is to use a function call, so if the original expression
974 // has parens on the outside, they are no longer needed.
975 let mut applicability = Applicability::MachineApplicable;
976 let opt = snippet_opt(cx, op.span);
977 let sugg = if let Some(ref snip) = opt {
978 if should_strip_parens(op, snip) {
979 &snip[1..snip.len() - 1]
984 applicability = Applicability::HasPlaceholders;
993 "casting {} to {} may become silently lossy if you later change the type",
997 format!("{}::from({})", cast_to, sugg),
1008 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1009 if !cast_from.is_signed() || cast_to.is_signed() {
1013 // don't lint for positive constants
1014 let const_val = constant(cx, &cx.tables, op);
1016 if let Some((const_val, _)) = const_val;
1017 if let Constant::Int(n) = const_val;
1018 if let ty::Int(ity) = cast_from.kind;
1019 if sext(cx.tcx, n, ity) >= 0;
1025 // don't lint for the result of methods that always return non-negative values
1026 if let ExprKind::MethodCall(ref path, _, _) = op.kind {
1027 let mut method_name = path.ident.name.as_str();
1028 let whitelisted_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"];
1031 if method_name == "unwrap";
1032 if let Some(arglist) = method_chain_args(op, &["unwrap"]);
1033 if let ExprKind::MethodCall(ref inner_path, _, _) = &arglist[0][0].kind;
1035 method_name = inner_path.ident.name.as_str();
1039 if whitelisted_methods.iter().any(|&name| method_name == name) {
1048 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1052 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1053 let arch_64_suffix = " on targets with 64-bit wide pointers";
1054 let arch_32_suffix = " on targets with 32-bit wide pointers";
1055 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1056 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1057 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1058 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1059 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1060 (true, true) | (false, false) => (
1061 to_nbits < from_nbits,
1063 to_nbits == from_nbits && cast_unsigned_to_signed,
1073 to_nbits <= 32 && cast_unsigned_to_signed,
1079 cast_unsigned_to_signed,
1080 if from_nbits == 64 {
1087 if span_truncation {
1090 CAST_POSSIBLE_TRUNCATION,
1093 "casting {} to {} may truncate the value{}",
1096 match suffix_truncation {
1097 ArchSuffix::_32 => arch_32_suffix,
1098 ArchSuffix::_64 => arch_64_suffix,
1099 ArchSuffix::None => "",
1110 "casting {} to {} may wrap around the value{}",
1114 ArchSuffix::_32 => arch_32_suffix,
1115 ArchSuffix::_64 => arch_64_suffix,
1116 ArchSuffix::None => "",
1123 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1124 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1125 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1126 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1127 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1129 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1133 declare_lint_pass!(Casts => [
1134 CAST_PRECISION_LOSS,
1136 CAST_POSSIBLE_TRUNCATION,
1142 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1145 // Check if the given type is either `core::ffi::c_void` or
1146 // one of the platform specific `libc::<platform>::c_void` of libc.
1147 fn is_c_void(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1148 if let ty::Adt(adt, _) = ty.kind {
1149 let names = cx.get_def_path(adt.did);
1151 if names.is_empty() {
1154 if names[0] == sym!(libc) || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
1161 /// Returns the mantissa bits wide of a fp type.
1162 /// Will return 0 if the type is not a fp
1163 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1165 ty::Float(FloatTy::F32) => 23,
1166 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1171 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
1172 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1173 if expr.span.from_expansion() {
1176 if let ExprKind::Cast(ref ex, _) = expr.kind {
1177 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1178 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1179 if let ExprKind::Lit(ref lit) = ex.kind {
1180 if let LitKind::Int(n, _) = lit.node {
1181 if cast_to.is_floating_point() {
1182 let from_nbits = 128 - n.leading_zeros();
1183 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1184 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1189 &format!("casting integer literal to {} is unnecessary", cast_to),
1191 format!("{}_{}", n, cast_to),
1192 Applicability::MachineApplicable,
1199 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
1201 if cast_from.kind == cast_to.kind && !in_external_macro(cx.sess(), expr.span) {
1207 "casting to the same type is unnecessary (`{}` -> `{}`)",
1215 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1216 lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
1219 lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
1224 fn lint_numeric_casts<'tcx>(
1225 cx: &LateContext<'_, 'tcx>,
1228 cast_from: Ty<'tcx>,
1231 match (cast_from.is_integral(), cast_to.is_integral()) {
1233 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1234 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.kind {
1239 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1240 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1242 if from_nbits < to_nbits {
1243 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1249 CAST_POSSIBLE_TRUNCATION,
1251 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1253 if !cast_to.is_signed() {
1258 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1263 check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
1264 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1265 check_lossless(cx, expr, cast_expr, cast_from, cast_to);
1268 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.kind, &cast_to.kind) {
1271 CAST_POSSIBLE_TRUNCATION,
1273 "casting f64 to f32 may truncate the value",
1276 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.kind, &cast_to.kind) {
1277 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1283 fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
1285 if let ty::RawPtr(from_ptr_ty) = &cast_from.kind;
1286 if let ty::RawPtr(to_ptr_ty) = &cast_to.kind;
1287 if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
1288 if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
1289 if from_layout.align.abi < to_layout.align.abi;
1290 // with c_void, we inherently need to trust the user
1291 if !is_c_void(cx, from_ptr_ty.ty);
1292 // when casting from a ZST, we don't know enough to properly lint
1293 if !from_layout.is_zst();
1300 "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
1303 from_layout.align.abi.bytes(),
1304 to_layout.align.abi.bytes(),
1311 fn lint_fn_to_numeric_cast(
1312 cx: &LateContext<'_, '_>,
1318 // We only want to check casts to `ty::Uint` or `ty::Int`
1319 match cast_to.kind {
1320 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1323 match cast_from.kind {
1324 ty::FnDef(..) | ty::FnPtr(_) => {
1325 let mut applicability = Applicability::MaybeIncorrect;
1326 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1328 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1329 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1332 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1335 "casting function pointer `{}` to `{}`, which truncates the value",
1336 from_snippet, cast_to
1339 format!("{} as usize", from_snippet),
1342 } else if cast_to.kind != ty::Uint(UintTy::Usize) {
1347 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1349 format!("{} as usize", from_snippet),
1358 declare_clippy_lint! {
1359 /// **What it does:** Checks for types used in structs, parameters and `let`
1360 /// declarations above a certain complexity threshold.
1362 /// **Why is this bad?** Too complex types make the code less readable. Consider
1363 /// using a `type` definition to simplify them.
1365 /// **Known problems:** None.
1369 /// # use std::rc::Rc;
1371 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1374 pub TYPE_COMPLEXITY,
1376 "usage of very complex types that might be better factored into `type` definitions"
1379 pub struct TypeComplexity {
1383 impl TypeComplexity {
1385 pub fn new(threshold: u64) -> Self {
1390 impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
1392 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexity {
1395 cx: &LateContext<'a, 'tcx>,
1402 self.check_fndecl(cx, decl);
1405 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1406 // enum variants are also struct fields now
1407 self.check_type(cx, &field.ty);
1410 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1412 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1413 // functions, enums, structs, impls and traits are covered
1418 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1420 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1421 TraitItemKind::Method(FnSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1422 // methods with default impl are covered by check_fn
1427 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1429 ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
1430 // methods are covered by check_fn
1435 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1436 if let Some(ref ty) = local.ty {
1437 self.check_type(cx, ty);
1442 impl<'a, 'tcx> TypeComplexity {
1443 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1444 for arg in &decl.inputs {
1445 self.check_type(cx, arg);
1447 if let Return(ref ty) = decl.output {
1448 self.check_type(cx, ty);
1452 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1453 if ty.span.from_expansion() {
1457 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1458 visitor.visit_ty(ty);
1462 if score > self.threshold {
1467 "very complex type used. Consider factoring parts into `type` definitions",
1473 /// Walks a type and assigns a complexity score to it.
1474 struct TypeComplexityVisitor {
1475 /// total complexity score of the type
1477 /// current nesting level
1481 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1482 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1483 let (add_score, sub_nest) = match ty.kind {
1484 // _, &x and *x have only small overhead; don't mess with nesting level
1485 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1487 // the "normal" components of a type: named types, arrays/tuples
1488 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1490 // function types bring a lot of overhead
1491 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1493 TyKind::TraitObject(ref param_bounds, _) => {
1494 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1495 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1496 GenericParamKind::Lifetime { .. } => true,
1500 if has_lifetime_parameters {
1501 // complex trait bounds like A<'a, 'b>
1504 // simple trait bounds like A + B
1511 self.score += add_score;
1512 self.nest += sub_nest;
1514 self.nest -= sub_nest;
1516 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1517 NestedVisitorMap::None
1521 declare_clippy_lint! {
1522 /// **What it does:** Checks for expressions where a character literal is cast
1523 /// to `u8` and suggests using a byte literal instead.
1525 /// **Why is this bad?** In general, casting values to smaller types is
1526 /// error-prone and should be avoided where possible. In the particular case of
1527 /// converting a character literal to u8, it is easy to avoid by just using a
1528 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1529 /// than `'a' as u8`.
1531 /// **Known problems:** None.
1538 /// A better version, using the byte literal:
1545 "casting a character literal to u8 truncates"
1548 declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
1550 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1551 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1553 if !expr.span.from_expansion();
1554 if let ExprKind::Cast(e, _) = &expr.kind;
1555 if let ExprKind::Lit(l) = &e.kind;
1556 if let LitKind::Char(c) = l.node;
1557 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).kind;
1559 let mut applicability = Applicability::MachineApplicable;
1560 let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
1566 "casting a character literal to `u8` truncates",
1568 db.note("`char` is four bytes wide, but `u8` is a single byte");
1573 "use a byte literal instead",
1574 format!("b{}", snippet),
1584 declare_clippy_lint! {
1585 /// **What it does:** Checks for comparisons where one side of the relation is
1586 /// either the minimum or maximum value for its type and warns if it involves a
1587 /// case that is always true or always false. Only integer and boolean types are
1590 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1591 /// that it is possible for `x` to be less than the minimum. Expressions like
1592 /// `max < x` are probably mistakes.
1594 /// **Known problems:** For `usize` the size of the current compile target will
1595 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1596 /// a comparison to detect target pointer width will trigger this lint. One can
1597 /// use `mem::sizeof` and compare its value or conditional compilation
1599 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1604 /// let vec: Vec<isize> = vec![];
1605 /// if vec.len() <= 0 {}
1606 /// if 100 > std::i32::MAX {}
1608 pub ABSURD_EXTREME_COMPARISONS,
1610 "a comparison with a maximum or minimum value that is always true or false"
1613 declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
1620 struct ExtremeExpr<'a> {
1625 enum AbsurdComparisonResult {
1628 InequalityImpossible,
1631 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1632 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1633 let precast_ty = cx.tables.expr_ty(cast_exp);
1634 let cast_ty = cx.tables.expr_ty(expr);
1636 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1642 fn detect_absurd_comparison<'a, 'tcx>(
1643 cx: &LateContext<'a, 'tcx>,
1647 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1648 use crate::types::AbsurdComparisonResult::*;
1649 use crate::types::ExtremeType::*;
1650 use crate::utils::comparisons::*;
1652 // absurd comparison only makes sense on primitive types
1653 // primitive types don't implement comparison operators with each other
1654 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1658 // comparisons between fix sized types and target sized types are considered unanalyzable
1659 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1663 let normalized = normalize_comparison(op, lhs, rhs);
1664 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1670 let lx = detect_extreme_expr(cx, normalized_lhs);
1671 let rx = detect_extreme_expr(cx, normalized_rhs);
1676 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1677 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1683 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1684 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1685 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1686 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1690 Rel::Ne | Rel::Eq => return None,
1694 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1695 use crate::types::ExtremeType::*;
1697 let ty = cx.tables.expr_ty(expr);
1699 let cv = constant(cx, cx.tables, expr)?.0;
1701 let which = match (&ty.kind, cv) {
1702 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1703 (&ty::Int(ity), Constant::Int(i))
1704 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1709 (&ty::Bool, Constant::Bool(true)) => Maximum,
1710 (&ty::Int(ity), Constant::Int(i))
1711 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1715 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1719 Some(ExtremeExpr { which, expr })
1722 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1723 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1724 use crate::types::AbsurdComparisonResult::*;
1725 use crate::types::ExtremeType::*;
1727 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
1728 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1729 if !expr.span.from_expansion() {
1730 let msg = "this comparison involving the minimum or maximum element for this \
1731 type contains a case that is always true or always false";
1733 let conclusion = match result {
1734 AlwaysFalse => "this comparison is always false".to_owned(),
1735 AlwaysTrue => "this comparison is always true".to_owned(),
1736 InequalityImpossible => format!(
1737 "the case where the two sides are not equal never occurs, consider using {} == {} \
1739 snippet(cx, lhs.span, "lhs"),
1740 snippet(cx, rhs.span, "rhs")
1745 "because {} is the {} value for this type, {}",
1746 snippet(cx, culprit.expr.span, "x"),
1747 match culprit.which {
1748 Minimum => "minimum",
1749 Maximum => "maximum",
1754 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1761 declare_clippy_lint! {
1762 /// **What it does:** Checks for comparisons where the relation is always either
1763 /// true or false, but where one side has been upcast so that the comparison is
1764 /// necessary. Only integer types are checked.
1766 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1767 /// will mistakenly imply that it is possible for `x` to be outside the range of
1770 /// **Known problems:**
1771 /// https://github.com/rust-lang/rust-clippy/issues/886
1776 /// (x as u32) > 300;
1778 pub INVALID_UPCAST_COMPARISONS,
1780 "a comparison involving an upcast which is always true or false"
1783 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
1785 #[derive(Copy, Clone, Debug, Eq)]
1792 #[allow(clippy::cast_sign_loss)]
1794 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1797 } else if u > (i128::max_value() as u128) {
1805 impl PartialEq for FullInt {
1807 fn eq(&self, other: &Self) -> bool {
1808 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1812 impl PartialOrd for FullInt {
1814 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1815 Some(match (self, other) {
1816 (&Self::S(s), &Self::S(o)) => s.cmp(&o),
1817 (&Self::U(s), &Self::U(o)) => s.cmp(&o),
1818 (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
1819 (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
1823 impl Ord for FullInt {
1825 fn cmp(&self, other: &Self) -> Ordering {
1826 self.partial_cmp(other)
1827 .expect("partial_cmp for FullInt can never return None")
1831 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1834 if let ExprKind::Cast(ref cast_exp, _) = expr.kind {
1835 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1836 let cast_ty = cx.tables.expr_ty(expr);
1837 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1838 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1841 match pre_cast_ty.kind {
1842 ty::Int(int_ty) => Some(match int_ty {
1844 FullInt::S(i128::from(i8::min_value())),
1845 FullInt::S(i128::from(i8::max_value())),
1848 FullInt::S(i128::from(i16::min_value())),
1849 FullInt::S(i128::from(i16::max_value())),
1852 FullInt::S(i128::from(i32::min_value())),
1853 FullInt::S(i128::from(i32::max_value())),
1856 FullInt::S(i128::from(i64::min_value())),
1857 FullInt::S(i128::from(i64::max_value())),
1859 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1861 FullInt::S(isize::min_value() as i128),
1862 FullInt::S(isize::max_value() as i128),
1865 ty::Uint(uint_ty) => Some(match uint_ty {
1867 FullInt::U(u128::from(u8::min_value())),
1868 FullInt::U(u128::from(u8::max_value())),
1871 FullInt::U(u128::from(u16::min_value())),
1872 FullInt::U(u128::from(u16::max_value())),
1875 FullInt::U(u128::from(u32::min_value())),
1876 FullInt::U(u128::from(u32::max_value())),
1879 FullInt::U(u128::from(u64::min_value())),
1880 FullInt::U(u128::from(u64::max_value())),
1882 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1884 FullInt::U(usize::min_value() as u128),
1885 FullInt::U(usize::max_value() as u128),
1895 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1896 let val = constant(cx, cx.tables, expr)?.0;
1897 if let Constant::Int(const_int) = val {
1898 match cx.tables.expr_ty(expr).kind {
1899 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1900 ty::Uint(_) => Some(FullInt::U(const_int)),
1908 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1909 if let ExprKind::Cast(ref cast_val, _) = expr.kind {
1912 INVALID_UPCAST_COMPARISONS,
1915 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1916 snippet(cx, cast_val.span, "the expression"),
1917 if always { "true" } else { "false" },
1923 fn upcast_comparison_bounds_err<'a, 'tcx>(
1924 cx: &LateContext<'a, 'tcx>,
1926 rel: comparisons::Rel,
1927 lhs_bounds: Option<(FullInt, FullInt)>,
1932 use crate::utils::comparisons::*;
1934 if let Some((lb, ub)) = lhs_bounds {
1935 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1936 if rel == Rel::Eq || rel == Rel::Ne {
1937 if norm_rhs_val < lb || norm_rhs_val > ub {
1938 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1940 } else if match rel {
1955 Rel::Eq | Rel::Ne => unreachable!(),
1957 err_upcast_comparison(cx, span, lhs, true)
1958 } else if match rel {
1973 Rel::Eq | Rel::Ne => unreachable!(),
1975 err_upcast_comparison(cx, span, lhs, false)
1981 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1982 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1983 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.kind {
1984 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1985 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1991 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1992 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1994 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1995 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
2000 declare_clippy_lint! {
2001 /// **What it does:** Checks for public `impl` or `fn` missing generalization
2002 /// over different hashers and implicitly defaulting to the default hashing
2003 /// algorithm (`SipHash`).
2005 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
2008 /// **Known problems:** Suggestions for replacing constructors can contain
2009 /// false-positives. Also applying suggestions can require modification of other
2010 /// pieces of code, possibly including external crates.
2014 /// # use std::collections::HashMap;
2015 /// # use std::hash::{Hash, BuildHasher};
2016 /// # trait Serialize {};
2017 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
2019 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
2021 /// could be rewritten as
2023 /// # use std::collections::HashMap;
2024 /// # use std::hash::{Hash, BuildHasher};
2025 /// # trait Serialize {};
2026 /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
2028 /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
2030 pub IMPLICIT_HASHER,
2032 "missing generalization over different hashers"
2035 declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
2037 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
2038 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
2039 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
2040 use syntax_pos::BytePos;
2042 fn suggestion<'a, 'tcx>(
2043 cx: &LateContext<'a, 'tcx>,
2044 db: &mut DiagnosticBuilder<'_>,
2045 generics_span: Span,
2046 generics_suggestion_span: Span,
2047 target: &ImplicitHasherType<'_>,
2048 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
2050 let generics_snip = snippet(cx, generics_span, "");
2052 let generics_snip = if generics_snip.is_empty() {
2055 &generics_snip[1..generics_snip.len() - 1]
2060 "consider adding a type parameter".to_string(),
2063 generics_suggestion_span,
2065 "<{}{}S: ::std::hash::BuildHasher{}>",
2067 if generics_snip.is_empty() { "" } else { ", " },
2068 if vis.suggestions.is_empty() {
2071 // request users to add `Default` bound so that generic constructors can be used
2078 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2083 if !vis.suggestions.is_empty() {
2084 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2088 if !cx.access_levels.is_exported(item.hir_id) {
2093 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2094 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2097 for target in &vis.found {
2098 if differing_macro_contexts(item.span, target.span()) {
2102 let generics_suggestion_span = generics.span.substitute_dummy({
2103 let pos = snippet_opt(cx, item.span.until(target.span()))
2104 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2105 if let Some(pos) = pos {
2106 Span::new(pos, pos, item.span.data().ctxt)
2112 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2113 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2114 ctr_vis.visit_impl_item(item);
2122 "impl for `{}` should be generalized over different hashers",
2126 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2131 ItemKind::Fn(ref sig, ref generics, body_id) => {
2132 let body = cx.tcx.hir().body(body_id);
2134 for ty in &sig.decl.inputs {
2135 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2138 for target in &vis.found {
2139 if in_external_macro(cx.sess(), generics.span) {
2142 let generics_suggestion_span = generics.span.substitute_dummy({
2143 let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
2145 let i = snip.find("fn")?;
2146 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2148 .expect("failed to create span for type parameters");
2149 Span::new(pos, pos, item.span.data().ctxt)
2152 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2153 ctr_vis.visit_body(body);
2160 "parameter of type `{}` should be generalized over different hashers",
2164 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2175 enum ImplicitHasherType<'tcx> {
2176 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2177 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2180 impl<'tcx> ImplicitHasherType<'tcx> {
2181 /// Checks that `ty` is a target type without a `BuildHasher`.
2182 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2183 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.kind {
2184 let params: Vec<_> = path
2192 .filter_map(|arg| match arg {
2193 GenericArg::Type(ty) => Some(ty),
2197 let params_len = params.len();
2199 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2201 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2202 Some(ImplicitHasherType::HashMap(
2205 snippet(cx, params[0].span, "K"),
2206 snippet(cx, params[1].span, "V"),
2208 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2209 Some(ImplicitHasherType::HashSet(
2212 snippet(cx, params[0].span, "T"),
2222 fn type_name(&self) -> &'static str {
2224 ImplicitHasherType::HashMap(..) => "HashMap",
2225 ImplicitHasherType::HashSet(..) => "HashSet",
2229 fn type_arguments(&self) -> String {
2231 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2232 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2236 fn ty(&self) -> Ty<'tcx> {
2238 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2242 fn span(&self) -> Span {
2244 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2249 struct ImplicitHasherTypeVisitor<'a, 'tcx> {
2250 cx: &'a LateContext<'a, 'tcx>,
2251 found: Vec<ImplicitHasherType<'tcx>>,
2254 impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
2255 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2256 Self { cx, found: vec![] }
2260 impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2261 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2262 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2263 self.found.push(target);
2269 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2270 NestedVisitorMap::None
2274 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2275 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2276 cx: &'a LateContext<'a, 'tcx>,
2277 body: &'a TypeckTables<'tcx>,
2278 target: &'b ImplicitHasherType<'tcx>,
2279 suggestions: BTreeMap<Span, String>,
2282 impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2283 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2288 suggestions: BTreeMap::new(),
2293 impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2294 fn visit_body(&mut self, body: &'tcx Body) {
2295 let prev_body = self.body;
2296 self.body = self.cx.tcx.body_tables(body.id());
2297 walk_body(self, body);
2298 self.body = prev_body;
2301 fn visit_expr(&mut self, e: &'tcx Expr) {
2303 if let ExprKind::Call(ref fun, ref args) = e.kind;
2304 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.kind;
2305 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.kind;
2307 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2311 if match_path(ty_path, &paths::HASHMAP) {
2312 if method.ident.name == sym!(new) {
2314 .insert(e.span, "HashMap::default()".to_string());
2315 } else if method.ident.name == sym!(with_capacity) {
2316 self.suggestions.insert(
2319 "HashMap::with_capacity_and_hasher({}, Default::default())",
2320 snippet(self.cx, args[0].span, "capacity"),
2324 } else if match_path(ty_path, &paths::HASHSET) {
2325 if method.ident.name == sym!(new) {
2327 .insert(e.span, "HashSet::default()".to_string());
2328 } else if method.ident.name == sym!(with_capacity) {
2329 self.suggestions.insert(
2332 "HashSet::with_capacity_and_hasher({}, Default::default())",
2333 snippet(self.cx, args[0].span, "capacity"),
2344 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2345 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2349 declare_clippy_lint! {
2350 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2352 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2353 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2356 /// **Known problems:** None.
2362 /// *(r as *const _ as *mut _) += 1;
2367 /// Instead consider using interior mutability types.
2370 /// use std::cell::UnsafeCell;
2372 /// fn x(r: &UnsafeCell<i32>) {
2378 pub CAST_REF_TO_MUT,
2380 "a cast of reference to a mutable pointer"
2383 declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
2385 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2386 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2388 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.kind;
2389 if let ExprKind::Cast(e, t) = &e.kind;
2390 if let TyKind::Ptr(MutTy { mutbl: Mutability::Mut, .. }) = t.kind;
2391 if let ExprKind::Cast(e, t) = &e.kind;
2392 if let TyKind::Ptr(MutTy { mutbl: Mutability::Not, .. }) = t.kind;
2393 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).kind;
2399 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",