1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 #![allow(clippy::default_hash_types)]
13 use crate::consts::{constant, Constant};
14 use crate::reexport::*;
15 use crate::rustc::hir;
16 use crate::rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
17 use crate::rustc::hir::*;
18 use crate::rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
19 use crate::rustc::ty::layout::LayoutOf;
20 use crate::rustc::ty::{self, Ty, TyCtxt, TypeckTables};
21 use crate::rustc::{declare_tool_lint, lint_array};
22 use crate::rustc_errors::Applicability;
23 use crate::rustc_target::spec::abi::Abi;
24 use crate::rustc_typeck::hir_ty_to_ty;
25 use crate::syntax::ast::{FloatTy, IntTy, UintTy};
26 use crate::syntax::errors::DiagnosticBuilder;
27 use crate::syntax::source_map::Span;
28 use crate::utils::paths;
30 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
31 match_def_path, match_path, match_type, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
32 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
34 use if_chain::if_chain;
36 use std::cmp::Ordering;
37 use std::collections::BTreeMap;
39 /// Handles all the linting of funky types
42 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
44 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
45 /// the heap. So if you `Box` it, you just add another level of indirection
46 /// without any benefit whatsoever.
48 /// **Known problems:** None.
53 /// values: Box<Vec<Foo>>,
64 declare_clippy_lint! {
67 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
70 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
73 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
74 /// represents an optional optional value which is logically the same thing as an optional
75 /// value but has an unneeded extra level of wrapping.
77 /// **Known problems:** None.
81 /// fn x() -> Option<Option<u32>> {
84 declare_clippy_lint! {
87 "usage of `Option<Option<T>>`"
90 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
91 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
93 /// **Why is this bad?** Gankro says:
95 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
96 /// pointers and indirection.
97 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
99 /// > "only" amortized for push/pop, should be faster in the general case for
100 /// almost every possible
101 /// > workload, and isn't even amortized at all if you can predict the capacity
104 /// > `LinkedList`s are only really good if you're doing a lot of merging or
105 /// splitting of lists.
106 /// > This is because they can just mangle some pointers instead of actually
107 /// copying the data. Even
108 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
109 /// can still be better
110 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
112 /// **Known problems:** False positives – the instances where using a
113 /// `LinkedList` makes sense are few and far between, but they can still happen.
117 /// let x = LinkedList::new();
119 declare_clippy_lint! {
122 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
125 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
127 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
130 /// **Known problems:** None.
134 /// fn foo(bar: &Box<T>) { ... }
140 /// fn foo(bar: &T) { ... }
142 declare_clippy_lint! {
145 "a borrow of a boxed type"
148 impl LintPass for TypePass {
149 fn get_lints(&self) -> LintArray {
150 lint_array!(BOX_VEC, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
154 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
155 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
156 // skip trait implementations, see #605
157 if let Some(hir::Node::Item(item)) = cx.tcx.hir.find(cx.tcx.hir.get_parent(id)) {
158 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
163 check_fn_decl(cx, decl);
166 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
167 check_ty(cx, &field.ty, false);
170 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
172 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
173 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
178 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
179 if let Some(ref ty) = local.ty {
180 check_ty(cx, ty, true);
185 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
186 for input in &decl.inputs {
187 check_ty(cx, input, false);
190 if let FunctionRetTy::Return(ref ty) = decl.output {
191 check_ty(cx, ty, false);
195 /// Check if `qpath` has last segment with type parameter matching `path`
196 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
197 let last = last_path_segment(qpath);
199 if let Some(ref params) = last.args;
200 if !params.parenthesized;
201 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
202 GenericArg::Type(ty) => Some(ty),
203 GenericArg::Lifetime(_) => None,
205 if let TyKind::Path(ref qpath) = ty.node;
206 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir.node_to_hir_id(ty.id)));
207 if match_def_path(cx.tcx, did, path);
215 /// Recursively check for `TypePass` lints in the given type. Stop at the first
218 /// The parameter `is_local` distinguishes the context of the type; types from
219 /// local bindings should only be checked for the `BORROWED_BOX` lint.
220 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
221 if in_macro(ast_ty.span) {
225 TyKind::Path(ref qpath) if !is_local => {
226 let hir_id = cx.tcx.hir.node_to_hir_id(ast_ty.id);
227 let def = cx.tables.qpath_def(qpath, hir_id);
228 if let Some(def_id) = opt_def_id(def) {
229 if Some(def_id) == cx.tcx.lang_items().owned_box() {
230 if match_type_parameter(cx, qpath, &paths::VEC) {
235 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
236 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
238 return; // don't recurse into the type
240 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
241 if match_type_parameter(cx, qpath, &paths::OPTION) {
246 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
247 enum if you need to distinguish all 3 cases",
249 return; // don't recurse into the type
251 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
256 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
257 "a VecDeque might work",
259 return; // don't recurse into the type
263 QPath::Resolved(Some(ref ty), ref p) => {
264 check_ty(cx, ty, is_local);
265 for ty in p.segments.iter().flat_map(|seg| {
268 .map_or_else(|| [].iter(), |params| params.args.iter())
269 .filter_map(|arg| match arg {
270 GenericArg::Type(ty) => Some(ty),
271 GenericArg::Lifetime(_) => None,
274 check_ty(cx, ty, is_local);
277 QPath::Resolved(None, ref p) => {
278 for ty in p.segments.iter().flat_map(|seg| {
281 .map_or_else(|| [].iter(), |params| params.args.iter())
282 .filter_map(|arg| match arg {
283 GenericArg::Type(ty) => Some(ty),
284 GenericArg::Lifetime(_) => None,
287 check_ty(cx, ty, is_local);
290 QPath::TypeRelative(ref ty, ref seg) => {
291 check_ty(cx, ty, is_local);
292 if let Some(ref params) = seg.args {
293 for ty in params.args.iter().filter_map(|arg| match arg {
294 GenericArg::Type(ty) => Some(ty),
295 GenericArg::Lifetime(_) => None,
297 check_ty(cx, ty, is_local);
303 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
305 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
306 check_ty(cx, ty, is_local)
308 TyKind::Tup(ref tys) => {
310 check_ty(cx, ty, is_local);
317 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
318 match mut_ty.ty.node {
319 TyKind::Path(ref qpath) => {
320 let hir_id = cx.tcx.hir.node_to_hir_id(mut_ty.ty.id);
321 let def = cx.tables.qpath_def(qpath, hir_id);
323 if let Some(def_id) = opt_def_id(def);
324 if Some(def_id) == cx.tcx.lang_items().owned_box();
325 if let QPath::Resolved(None, ref path) = *qpath;
326 if let [ref bx] = *path.segments;
327 if let Some(ref params) = bx.args;
328 if !params.parenthesized;
329 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
330 GenericArg::Type(ty) => Some(ty),
331 GenericArg::Lifetime(_) => None,
334 if is_any_trait(inner) {
335 // Ignore `Box<Any>` types, see #1884 for details.
339 let ltopt = if lt.is_elided() {
342 format!("{} ", lt.name.ident().as_str())
344 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
349 let mut applicability = Applicability::MachineApplicable;
354 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
360 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
362 Applicability::Unspecified,
364 return; // don't recurse into the type
367 check_ty(cx, &mut_ty.ty, is_local);
369 _ => check_ty(cx, &mut_ty.ty, is_local),
373 // Returns true if given type is `Any` trait.
374 fn is_any_trait(t: &hir::Ty) -> bool {
376 if let TyKind::TraitObject(ref traits, _) = t.node;
377 if traits.len() >= 1;
378 // Only Send/Sync can be used as additional traits, so it is enough to
379 // check only the first trait.
380 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
391 /// **What it does:** Checks for binding a unit value.
393 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
394 /// binding one is kind of pointless.
396 /// **Known problems:** None.
404 declare_clippy_lint! {
407 "creating a let binding to a value of unit type, which usually can't be used afterwards"
410 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
411 if let DeclKind::Local(ref local) = decl.node {
412 if is_unit(cx.tables.pat_ty(&local.pat)) {
413 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
416 if higher::is_from_for_desugar(decl) {
424 "this let-binding has unit value. Consider omitting `let {} =`",
425 snippet(cx, local.pat.span, "..")
432 impl LintPass for LetPass {
433 fn get_lints(&self) -> LintArray {
434 lint_array!(LET_UNIT_VALUE)
438 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
439 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
440 check_let_unit(cx, decl)
444 /// **What it does:** Checks for comparisons to unit.
446 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
447 /// clumsily written constant. Mostly this happens when someone accidentally
448 /// adds semicolons at the end of the operands.
450 /// **Known problems:** None.
470 declare_clippy_lint! {
473 "comparing unit values"
478 impl LintPass for UnitCmp {
479 fn get_lints(&self) -> LintArray {
480 lint_array!(UNIT_CMP)
484 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
485 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
486 if in_macro(expr.span) {
489 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
491 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
492 let result = match op {
493 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
501 "{}-comparison of unit values detected. This will always be {}",
511 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
512 /// unit literal (`()`).
514 /// **Why is this bad?** This is likely the result of an accidental semicolon.
516 /// **Known problems:** None.
525 declare_clippy_lint! {
528 "passing unit to a function"
533 impl LintPass for UnitArg {
534 fn get_lints(&self) -> LintArray {
535 lint_array!(UNIT_ARG)
539 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
540 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
541 if in_macro(expr.span) {
545 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
547 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
548 let map = &cx.tcx.hir;
549 // apparently stuff in the desugaring of `?` can trigger this
550 // so check for that here
551 // only the calls to `Try::from_error` is marked as desugared,
552 // so we need to check both the current Expr and its parent.
553 if !is_questionmark_desugar_marked_call(expr) {
555 let opt_parent_node = map.find(map.get_parent_node(expr.id));
556 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
557 if is_questionmark_desugar_marked_call(parent_expr);
560 // `expr` and `parent_expr` where _both_ not from
561 // desugaring `?`, so lint
566 "passing a unit value to a function",
567 "if you intended to pass a unit value, use a unit literal instead",
569 Applicability::MachineApplicable,
582 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
583 use crate::syntax_pos::hygiene::CompilerDesugaringKind;
584 if let ExprKind::Call(ref callee, _) = expr.node {
585 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
591 fn is_unit(ty: Ty<'_>) -> bool {
593 ty::Tuple(slice) if slice.is_empty() => true,
598 fn is_unit_literal(expr: &Expr) -> bool {
600 ExprKind::Tup(ref slice) if slice.is_empty() => true,
607 /// **What it does:** Checks for casts from any numerical to a float type where
608 /// the receiving type cannot store all values from the original type without
609 /// rounding errors. This possible rounding is to be expected, so this lint is
610 /// `Allow` by default.
612 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
613 /// or any 64-bit integer to `f64`.
615 /// **Why is this bad?** It's not bad at all. But in some applications it can be
616 /// helpful to know where precision loss can take place. This lint can help find
617 /// those places in the code.
619 /// **Known problems:** None.
623 /// let x = u64::MAX;
626 declare_clippy_lint! {
627 pub CAST_PRECISION_LOSS,
629 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
632 /// **What it does:** Checks for casts from a signed to an unsigned numerical
633 /// type. In this case, negative values wrap around to large positive values,
634 /// which can be quite surprising in practice. However, as the cast works as
635 /// defined, this lint is `Allow` by default.
637 /// **Why is this bad?** Possibly surprising results. You can activate this lint
638 /// as a one-time check to see where numerical wrapping can arise.
640 /// **Known problems:** None.
645 /// y as u128 // will return 18446744073709551615
647 declare_clippy_lint! {
650 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
653 /// **What it does:** Checks for on casts between numerical types that may
654 /// truncate large values. This is expected behavior, so the cast is `Allow` by
657 /// **Why is this bad?** In some problem domains, it is good practice to avoid
658 /// truncation. This lint can be activated to help assess where additional
659 /// checks could be beneficial.
661 /// **Known problems:** None.
665 /// fn as_u8(x: u64) -> u8 {
669 declare_clippy_lint! {
670 pub CAST_POSSIBLE_TRUNCATION,
672 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
675 /// **What it does:** Checks for casts from an unsigned type to a signed type of
676 /// the same size. Performing such a cast is a 'no-op' for the compiler,
677 /// i.e. nothing is changed at the bit level, and the binary representation of
678 /// the value is reinterpreted. This can cause wrapping if the value is too big
679 /// for the target signed type. However, the cast works as defined, so this lint
680 /// is `Allow` by default.
682 /// **Why is this bad?** While such a cast is not bad in itself, the results can
683 /// be surprising when this is not the intended behavior, as demonstrated by the
686 /// **Known problems:** None.
690 /// u32::MAX as i32 // will yield a value of `-1`
692 declare_clippy_lint! {
693 pub CAST_POSSIBLE_WRAP,
695 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
698 /// **What it does:** Checks for on casts between numerical types that may
699 /// be replaced by safe conversion functions.
701 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
702 /// conversions, including silently lossy conversions. Conversion functions such
703 /// as `i32::from` will only perform lossless conversions. Using the conversion
704 /// functions prevents conversions from turning into silent lossy conversions if
705 /// the types of the input expressions ever change, and make it easier for
706 /// people reading the code to know that the conversion is lossless.
708 /// **Known problems:** None.
712 /// fn as_u64(x: u8) -> u64 {
717 /// Using `::from` would look like this:
720 /// fn as_u64(x: u8) -> u64 {
724 declare_clippy_lint! {
727 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
730 /// **What it does:** Checks for casts to the same type.
732 /// **Why is this bad?** It's just unnecessary.
734 /// **Known problems:** None.
738 /// let _ = 2i32 as i32
740 declare_clippy_lint! {
741 pub UNNECESSARY_CAST,
743 "cast to the same type, e.g. `x as i32` where `x: i32`"
746 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
747 /// more-strictly-aligned pointer
749 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
752 /// **Known problems:** None.
756 /// let _ = (&1u8 as *const u8) as *const u16;
757 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
759 declare_clippy_lint! {
760 pub CAST_PTR_ALIGNMENT,
762 "cast from a pointer to a more-strictly-aligned pointer"
765 /// **What it does:** Checks for casts of function pointers to something other than usize
767 /// **Why is this bad?**
768 /// Casting a function pointer to anything other than usize/isize is not portable across
769 /// architectures, because you end up losing bits if the target type is too small or end up with a
770 /// bunch of extra bits that waste space and add more instructions to the final binary than
771 /// strictly necessary for the problem
773 /// Casting to isize also doesn't make sense since there are no signed addresses.
779 /// fn fun() -> i32 {}
780 /// let a = fun as i64;
783 /// fn fun2() -> i32 {}
784 /// let a = fun2 as usize;
786 declare_clippy_lint! {
787 pub FN_TO_NUMERIC_CAST,
789 "casting a function pointer to a numeric type other than usize"
792 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
795 /// **Why is this bad?**
796 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
797 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
798 /// a comment) to perform the truncation.
804 /// fn fn1() -> i16 {
807 /// let _ = fn1 as i32;
809 /// // Better: Cast to usize first, then comment with the reason for the truncation
810 /// fn fn2() -> i16 {
813 /// let fn_ptr = fn2 as usize;
814 /// let fn_ptr_truncated = fn_ptr as i32;
816 declare_clippy_lint! {
817 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
819 "casting a function pointer to a numeric type not wide enough to store the address"
822 /// Returns the size in bits of an integral type.
823 /// Will return 0 if the type is not an int or uint variant
824 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
826 ty::Int(i) => match i {
827 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
834 ty::Uint(i) => match i {
835 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
846 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
848 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
853 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
854 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
855 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
856 let arch_dependent_str = "on targets with 64-bit wide pointers ";
857 let from_nbits_str = if arch_dependent {
859 } else if is_isize_or_usize(cast_from) {
860 "32 or 64".to_owned()
862 int_ty_to_nbits(cast_from, cx.tcx).to_string()
869 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
870 is only {4} bits wide)",
872 if cast_to_f64 { "f64" } else { "f32" },
873 if arch_dependent { arch_dependent_str } else { "" },
880 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
881 if let ExprKind::Binary(_, _, _) = op.node {
882 if snip.starts_with('(') && snip.ends_with(')') {
889 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
890 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
891 if in_constant(cx, expr.id) {
894 // The suggestion is to use a function call, so if the original expression
895 // has parens on the outside, they are no longer needed.
896 let mut applicability = Applicability::MachineApplicable;
897 let opt = snippet_opt(cx, op.span);
898 let sugg = if let Some(ref snip) = opt {
899 if should_strip_parens(op, snip) {
900 &snip[1..snip.len() - 1]
905 applicability = Applicability::HasPlaceholders;
914 "casting {} to {} may become silently lossy if types change",
918 format!("{}::from({})", cast_to, sugg),
929 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
930 let arch_64_suffix = " on targets with 64-bit wide pointers";
931 let arch_32_suffix = " on targets with 32-bit wide pointers";
932 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
933 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
934 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
935 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
936 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
937 (true, true) | (false, false) => (
938 to_nbits < from_nbits,
940 to_nbits == from_nbits && cast_unsigned_to_signed,
950 to_nbits <= 32 && cast_unsigned_to_signed,
956 cast_unsigned_to_signed,
957 if from_nbits == 64 {
967 CAST_POSSIBLE_TRUNCATION,
970 "casting {} to {} may truncate the value{}",
973 match suffix_truncation {
974 ArchSuffix::_32 => arch_32_suffix,
975 ArchSuffix::_64 => arch_64_suffix,
976 ArchSuffix::None => "",
987 "casting {} to {} may wrap around the value{}",
991 ArchSuffix::_32 => arch_32_suffix,
992 ArchSuffix::_64 => arch_64_suffix,
993 ArchSuffix::None => "",
1000 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1001 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1002 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1003 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1004 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1006 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1010 impl LintPass for CastPass {
1011 fn get_lints(&self) -> LintArray {
1013 CAST_PRECISION_LOSS,
1015 CAST_POSSIBLE_TRUNCATION,
1021 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1026 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1027 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1028 if let ExprKind::Cast(ref ex, _) = expr.node {
1029 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1030 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1031 if let ExprKind::Lit(ref lit) = ex.node {
1032 use crate::syntax::ast::{LitIntType, LitKind};
1034 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1036 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1042 "casting to the same type is unnecessary (`{}` -> `{}`)",
1050 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1051 match (cast_from.is_integral(), cast_to.is_integral()) {
1053 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1054 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1059 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1060 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1062 if from_nbits < to_nbits {
1063 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1069 CAST_POSSIBLE_TRUNCATION,
1071 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1073 if !cast_to.is_signed() {
1078 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1083 if cast_from.is_signed() && !cast_to.is_signed() {
1088 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1091 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1092 check_lossless(cx, expr, ex, cast_from, cast_to);
1095 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1098 CAST_POSSIBLE_TRUNCATION,
1100 "casting f64 to f32 may truncate the value",
1103 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1104 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1111 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1112 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1113 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1114 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1115 if from_align < to_align;
1116 // with c_void, we inherently need to trust the user
1118 match_type(cx, from_ptr_ty.ty, &paths::C_VOID)
1119 || match_type(cx, from_ptr_ty.ty, &paths::C_VOID_LIBC)
1126 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1134 fn lint_fn_to_numeric_cast(
1135 cx: &LateContext<'_, '_>,
1141 // We only want to check casts to `ty::Uint` or `ty::Int`
1143 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1146 match cast_from.sty {
1147 ty::FnDef(..) | ty::FnPtr(_) => {
1148 let mut applicability = Applicability::MachineApplicable;
1149 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1151 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1152 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1155 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1158 "casting function pointer `{}` to `{}`, which truncates the value",
1159 from_snippet, cast_to
1162 format!("{} as usize", from_snippet),
1165 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1170 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1172 format!("{} as usize", from_snippet),
1181 /// **What it does:** Checks for types used in structs, parameters and `let`
1182 /// declarations above a certain complexity threshold.
1184 /// **Why is this bad?** Too complex types make the code less readable. Consider
1185 /// using a `type` definition to simplify them.
1187 /// **Known problems:** None.
1192 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1195 declare_clippy_lint! {
1196 pub TYPE_COMPLEXITY,
1198 "usage of very complex types that might be better factored into `type` definitions"
1201 pub struct TypeComplexityPass {
1205 impl TypeComplexityPass {
1206 pub fn new(threshold: u64) -> Self {
1211 impl LintPass for TypeComplexityPass {
1212 fn get_lints(&self) -> LintArray {
1213 lint_array!(TYPE_COMPLEXITY)
1217 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1220 cx: &LateContext<'a, 'tcx>,
1227 self.check_fndecl(cx, decl);
1230 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1231 // enum variants are also struct fields now
1232 self.check_type(cx, &field.ty);
1235 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1237 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1238 // functions, enums, structs, impls and traits are covered
1243 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1245 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1246 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1247 // methods with default impl are covered by check_fn
1252 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1254 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1255 // methods are covered by check_fn
1260 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1261 if let Some(ref ty) = local.ty {
1262 self.check_type(cx, ty);
1267 impl<'a, 'tcx> TypeComplexityPass {
1268 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1269 for arg in &decl.inputs {
1270 self.check_type(cx, arg);
1272 if let Return(ref ty) = decl.output {
1273 self.check_type(cx, ty);
1277 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1278 if in_macro(ty.span) {
1282 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1283 visitor.visit_ty(ty);
1287 if score > self.threshold {
1292 "very complex type used. Consider factoring parts into `type` definitions",
1298 /// Walks a type and assigns a complexity score to it.
1299 struct TypeComplexityVisitor {
1300 /// total complexity score of the type
1302 /// current nesting level
1306 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1307 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1308 let (add_score, sub_nest) = match ty.node {
1309 // _, &x and *x have only small overhead; don't mess with nesting level
1310 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1312 // the "normal" components of a type: named types, arrays/tuples
1313 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1315 // function types bring a lot of overhead
1316 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1318 TyKind::TraitObject(ref param_bounds, _) => {
1319 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1320 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1321 GenericParamKind::Lifetime { .. } => true,
1325 if has_lifetime_parameters {
1326 // complex trait bounds like A<'a, 'b>
1329 // simple trait bounds like A + B
1336 self.score += add_score;
1337 self.nest += sub_nest;
1339 self.nest -= sub_nest;
1341 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1342 NestedVisitorMap::None
1346 /// **What it does:** Checks for expressions where a character literal is cast
1347 /// to `u8` and suggests using a byte literal instead.
1349 /// **Why is this bad?** In general, casting values to smaller types is
1350 /// error-prone and should be avoided where possible. In the particular case of
1351 /// converting a character literal to u8, it is easy to avoid by just using a
1352 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1353 /// than `'a' as u8`.
1355 /// **Known problems:** None.
1362 /// A better version, using the byte literal:
1367 declare_clippy_lint! {
1370 "casting a character literal to u8"
1373 pub struct CharLitAsU8;
1375 impl LintPass for CharLitAsU8 {
1376 fn get_lints(&self) -> LintArray {
1377 lint_array!(CHAR_LIT_AS_U8)
1381 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1382 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1383 use crate::syntax::ast::{LitKind, UintTy};
1385 if let ExprKind::Cast(ref e, _) = expr.node {
1386 if let ExprKind::Lit(ref l) = e.node {
1387 if let LitKind::Char(_) = l.node {
1388 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1389 let msg = "casting character literal to u8. `char`s \
1390 are 4 bytes wide in rust, so casting to u8 \
1393 "Consider using a byte literal instead:\nb{}",
1394 snippet(cx, e.span, "'x'")
1396 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1404 /// **What it does:** Checks for comparisons where one side of the relation is
1405 /// either the minimum or maximum value for its type and warns if it involves a
1406 /// case that is always true or always false. Only integer and boolean types are
1409 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1410 /// that is is possible for `x` to be less than the minimum. Expressions like
1411 /// `max < x` are probably mistakes.
1413 /// **Known problems:** For `usize` the size of the current compile target will
1414 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1415 /// a comparison to detect target pointer width will trigger this lint. One can
1416 /// use `mem::sizeof` and compare its value or conditional compilation
1418 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1423 /// 100 > std::i32::MAX
1425 declare_clippy_lint! {
1426 pub ABSURD_EXTREME_COMPARISONS,
1428 "a comparison with a maximum or minimum value that is always true or false"
1431 pub struct AbsurdExtremeComparisons;
1433 impl LintPass for AbsurdExtremeComparisons {
1434 fn get_lints(&self) -> LintArray {
1435 lint_array!(ABSURD_EXTREME_COMPARISONS)
1444 struct ExtremeExpr<'a> {
1449 enum AbsurdComparisonResult {
1452 InequalityImpossible,
1455 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1456 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1457 let precast_ty = cx.tables.expr_ty(cast_exp);
1458 let cast_ty = cx.tables.expr_ty(expr);
1460 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1466 fn detect_absurd_comparison<'a, 'tcx>(
1467 cx: &LateContext<'a, 'tcx>,
1471 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1472 use crate::types::AbsurdComparisonResult::*;
1473 use crate::types::ExtremeType::*;
1474 use crate::utils::comparisons::*;
1476 // absurd comparison only makes sense on primitive types
1477 // primitive types don't implement comparison operators with each other
1478 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1482 // comparisons between fix sized types and target sized types are considered unanalyzable
1483 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1487 let normalized = normalize_comparison(op, lhs, rhs);
1488 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1494 let lx = detect_extreme_expr(cx, normalized_lhs);
1495 let rx = detect_extreme_expr(cx, normalized_rhs);
1500 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1501 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1507 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1508 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1509 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1510 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1514 Rel::Ne | Rel::Eq => return None,
1518 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1519 use crate::types::ExtremeType::*;
1521 let ty = cx.tables.expr_ty(expr);
1523 let cv = constant(cx, cx.tables, expr)?.0;
1525 let which = match (&ty.sty, cv) {
1526 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1527 (&ty::Int(ity), Constant::Int(i))
1528 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1533 (&ty::Bool, Constant::Bool(true)) => Maximum,
1534 (&ty::Int(ity), Constant::Int(i))
1535 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1539 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1543 Some(ExtremeExpr { which, expr })
1546 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1547 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1548 use crate::types::AbsurdComparisonResult::*;
1549 use crate::types::ExtremeType::*;
1551 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1552 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1553 if !in_macro(expr.span) {
1554 let msg = "this comparison involving the minimum or maximum element for this \
1555 type contains a case that is always true or always false";
1557 let conclusion = match result {
1558 AlwaysFalse => "this comparison is always false".to_owned(),
1559 AlwaysTrue => "this comparison is always true".to_owned(),
1560 InequalityImpossible => format!(
1561 "the case where the two sides are not equal never occurs, consider using {} == {} \
1563 snippet(cx, lhs.span, "lhs"),
1564 snippet(cx, rhs.span, "rhs")
1569 "because {} is the {} value for this type, {}",
1570 snippet(cx, culprit.expr.span, "x"),
1571 match culprit.which {
1572 Minimum => "minimum",
1573 Maximum => "maximum",
1578 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1585 /// **What it does:** Checks for comparisons where the relation is always either
1586 /// true or false, but where one side has been upcast so that the comparison is
1587 /// necessary. Only integer types are checked.
1589 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1590 /// will mistakenly imply that it is possible for `x` to be outside the range of
1593 /// **Known problems:**
1594 /// https://github.com/rust-lang/rust-clippy/issues/886
1598 /// let x : u8 = ...; (x as u32) > 300
1600 declare_clippy_lint! {
1601 pub INVALID_UPCAST_COMPARISONS,
1603 "a comparison involving an upcast which is always true or false"
1606 pub struct InvalidUpcastComparisons;
1608 impl LintPass for InvalidUpcastComparisons {
1609 fn get_lints(&self) -> LintArray {
1610 lint_array!(INVALID_UPCAST_COMPARISONS)
1614 #[derive(Copy, Clone, Debug, Eq)]
1621 #[allow(clippy::cast_sign_loss)]
1622 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1625 } else if u > (i128::max_value() as u128) {
1633 impl PartialEq for FullInt {
1634 fn eq(&self, other: &Self) -> bool {
1635 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1639 impl PartialOrd for FullInt {
1640 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1641 Some(match (self, other) {
1642 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1643 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1644 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1645 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1649 impl Ord for FullInt {
1650 fn cmp(&self, other: &Self) -> Ordering {
1651 self.partial_cmp(other)
1652 .expect("partial_cmp for FullInt can never return None")
1656 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1657 use crate::syntax::ast::{IntTy, UintTy};
1660 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1661 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1662 let cast_ty = cx.tables.expr_ty(expr);
1663 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1664 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1667 match pre_cast_ty.sty {
1668 ty::Int(int_ty) => Some(match int_ty {
1670 FullInt::S(i128::from(i8::min_value())),
1671 FullInt::S(i128::from(i8::max_value())),
1674 FullInt::S(i128::from(i16::min_value())),
1675 FullInt::S(i128::from(i16::max_value())),
1678 FullInt::S(i128::from(i32::min_value())),
1679 FullInt::S(i128::from(i32::max_value())),
1682 FullInt::S(i128::from(i64::min_value())),
1683 FullInt::S(i128::from(i64::max_value())),
1685 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1687 FullInt::S(isize::min_value() as i128),
1688 FullInt::S(isize::max_value() as i128),
1691 ty::Uint(uint_ty) => Some(match uint_ty {
1693 FullInt::U(u128::from(u8::min_value())),
1694 FullInt::U(u128::from(u8::max_value())),
1697 FullInt::U(u128::from(u16::min_value())),
1698 FullInt::U(u128::from(u16::max_value())),
1701 FullInt::U(u128::from(u32::min_value())),
1702 FullInt::U(u128::from(u32::max_value())),
1705 FullInt::U(u128::from(u64::min_value())),
1706 FullInt::U(u128::from(u64::max_value())),
1708 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1710 FullInt::U(usize::min_value() as u128),
1711 FullInt::U(usize::max_value() as u128),
1721 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1722 let val = constant(cx, cx.tables, expr)?.0;
1723 if let Constant::Int(const_int) = val {
1724 match cx.tables.expr_ty(expr).sty {
1725 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1726 ty::Uint(_) => Some(FullInt::U(const_int)),
1734 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1735 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1738 INVALID_UPCAST_COMPARISONS,
1741 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1742 snippet(cx, cast_val.span, "the expression"),
1743 if always { "true" } else { "false" },
1749 fn upcast_comparison_bounds_err<'a, 'tcx>(
1750 cx: &LateContext<'a, 'tcx>,
1752 rel: comparisons::Rel,
1753 lhs_bounds: Option<(FullInt, FullInt)>,
1758 use crate::utils::comparisons::*;
1760 if let Some((lb, ub)) = lhs_bounds {
1761 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1762 if rel == Rel::Eq || rel == Rel::Ne {
1763 if norm_rhs_val < lb || norm_rhs_val > ub {
1764 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1766 } else if match rel {
1781 Rel::Eq | Rel::Ne => unreachable!(),
1783 err_upcast_comparison(cx, span, lhs, true)
1784 } else if match rel {
1799 Rel::Eq | Rel::Ne => unreachable!(),
1801 err_upcast_comparison(cx, span, lhs, false)
1807 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1808 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1809 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1810 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1811 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1817 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1818 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1820 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1821 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1826 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1827 /// over different hashers and implicitly defaulting to the default hashing
1828 /// algorithm (SipHash).
1830 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1833 /// **Known problems:** Suggestions for replacing constructors can contain
1834 /// false-positives. Also applying suggestions can require modification of other
1835 /// pieces of code, possibly including external crates.
1839 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1841 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1843 declare_clippy_lint! {
1844 pub IMPLICIT_HASHER,
1846 "missing generalization over different hashers"
1849 pub struct ImplicitHasher;
1851 impl LintPass for ImplicitHasher {
1852 fn get_lints(&self) -> LintArray {
1853 lint_array!(IMPLICIT_HASHER)
1857 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1858 #[allow(clippy::cast_possible_truncation)]
1859 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1860 use crate::syntax_pos::BytePos;
1862 fn suggestion<'a, 'tcx>(
1863 cx: &LateContext<'a, 'tcx>,
1864 db: &mut DiagnosticBuilder<'_>,
1865 generics_span: Span,
1866 generics_suggestion_span: Span,
1867 target: &ImplicitHasherType<'_>,
1868 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1870 let generics_snip = snippet(cx, generics_span, "");
1872 let generics_snip = if generics_snip.is_empty() {
1875 &generics_snip[1..generics_snip.len() - 1]
1880 "consider adding a type parameter".to_string(),
1883 generics_suggestion_span,
1885 "<{}{}S: ::std::hash::BuildHasher{}>",
1887 if generics_snip.is_empty() { "" } else { ", " },
1888 if vis.suggestions.is_empty() {
1891 // request users to add `Default` bound so that generic constructors can be used
1898 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1903 if !vis.suggestions.is_empty() {
1904 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1908 if !cx.access_levels.is_exported(item.id) {
1913 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1914 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1917 for target in &vis.found {
1918 if differing_macro_contexts(item.span, target.span()) {
1922 let generics_suggestion_span = generics.span.substitute_dummy({
1923 let pos = snippet_opt(cx, item.span.until(target.span()))
1924 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
1925 if let Some(pos) = pos {
1926 Span::new(pos, pos, item.span.data().ctxt)
1932 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1933 for item in items.iter().map(|item| cx.tcx.hir.impl_item(item.id)) {
1934 ctr_vis.visit_impl_item(item);
1942 "impl for `{}` should be generalized over different hashers",
1946 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1951 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
1952 let body = cx.tcx.hir.body(body_id);
1954 for ty in &decl.inputs {
1955 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1958 for target in &vis.found {
1959 let generics_suggestion_span = generics.span.substitute_dummy({
1960 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
1962 let i = snip.find("fn")?;
1963 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
1965 .expect("failed to create span for type parameters");
1966 Span::new(pos, pos, item.span.data().ctxt)
1969 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1970 ctr_vis.visit_body(body);
1977 "parameter of type `{}` should be generalized over different hashers",
1981 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1992 enum ImplicitHasherType<'tcx> {
1993 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
1994 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
1997 impl<'tcx> ImplicitHasherType<'tcx> {
1998 /// Checks that `ty` is a target type without a BuildHasher.
1999 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2000 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2001 let params: Vec<_> = path
2009 .filter_map(|arg| match arg {
2010 GenericArg::Type(ty) => Some(ty),
2011 GenericArg::Lifetime(_) => None,
2014 let params_len = params.len();
2016 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2018 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2019 Some(ImplicitHasherType::HashMap(
2022 snippet(cx, params[0].span, "K"),
2023 snippet(cx, params[1].span, "V"),
2025 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2026 Some(ImplicitHasherType::HashSet(
2029 snippet(cx, params[0].span, "T"),
2039 fn type_name(&self) -> &'static str {
2041 ImplicitHasherType::HashMap(..) => "HashMap",
2042 ImplicitHasherType::HashSet(..) => "HashSet",
2046 fn type_arguments(&self) -> String {
2048 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2049 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2053 fn ty(&self) -> Ty<'tcx> {
2055 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2059 fn span(&self) -> Span {
2061 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2066 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2067 cx: &'a LateContext<'a, 'tcx>,
2068 found: Vec<ImplicitHasherType<'tcx>>,
2071 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2072 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2073 Self { cx, found: vec![] }
2077 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2078 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2079 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2080 self.found.push(target);
2086 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2087 NestedVisitorMap::None
2091 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2092 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2093 cx: &'a LateContext<'a, 'tcx>,
2094 body: &'a TypeckTables<'tcx>,
2095 target: &'b ImplicitHasherType<'tcx>,
2096 suggestions: BTreeMap<Span, String>,
2099 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2100 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2105 suggestions: BTreeMap::new(),
2110 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2111 fn visit_body(&mut self, body: &'tcx Body) {
2112 self.body = self.cx.tcx.body_tables(body.id());
2113 walk_body(self, body);
2116 fn visit_expr(&mut self, e: &'tcx Expr) {
2118 if let ExprKind::Call(ref fun, ref args) = e.node;
2119 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2120 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2122 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2126 if match_path(ty_path, &paths::HASHMAP) {
2127 if method.ident.name == "new" {
2129 .insert(e.span, "HashMap::default()".to_string());
2130 } else if method.ident.name == "with_capacity" {
2131 self.suggestions.insert(
2134 "HashMap::with_capacity_and_hasher({}, Default::default())",
2135 snippet(self.cx, args[0].span, "capacity"),
2139 } else if match_path(ty_path, &paths::HASHSET) {
2140 if method.ident.name == "new" {
2142 .insert(e.span, "HashSet::default()".to_string());
2143 } else if method.ident.name == "with_capacity" {
2144 self.suggestions.insert(
2147 "HashSet::with_capacity_and_hasher({}, Default::default())",
2148 snippet(self.cx, args[0].span, "capacity"),
2159 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2160 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)