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::reexport::*;
14 use crate::rustc::hir;
15 use crate::rustc::hir::*;
16 use crate::rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
17 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass, in_external_macro, LintContext};
18 use crate::rustc::{declare_tool_lint, lint_array};
19 use if_chain::if_chain;
20 use crate::rustc::ty::{self, Ty, TyCtxt, TypeckTables};
21 use crate::rustc::ty::layout::LayoutOf;
22 use crate::rustc_typeck::hir_ty_to_ty;
23 use std::cmp::Ordering;
24 use std::collections::BTreeMap;
26 use crate::syntax::ast::{FloatTy, IntTy, UintTy};
27 use crate::syntax::source_map::Span;
28 use crate::syntax::errors::DiagnosticBuilder;
29 use crate::rustc_target::spec::abi::Abi;
30 use crate::utils::{comparisons, differing_macro_contexts, higher, in_constant, in_macro, last_path_segment, match_def_path, match_path,
31 match_type, multispan_sugg, opt_def_id, same_tys, snippet, snippet_opt, span_help_and_lint, span_lint,
32 span_lint_and_sugg, span_lint_and_then, clip, unsext, sext, int_bits};
33 use crate::utils::paths;
34 use crate::consts::{constant, Constant};
36 /// Handles all the linting of funky types
37 #[allow(missing_copy_implementations)]
40 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
42 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
43 /// the heap. So if you `Box` it, you just add another level of indirection
44 /// without any benefit whatsoever.
46 /// **Known problems:** None.
51 /// values: Box<Vec<Foo>>,
62 declare_clippy_lint! {
65 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
68 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
71 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
72 /// represents an optional optional value which is logically the same thing as an optional
73 /// value but has an unneeded extra level of wrapping.
75 /// **Known problems:** None.
79 /// fn x() -> Option<Option<u32>> {
82 declare_clippy_lint! {
85 "usage of `Option<Option<T>>`"
88 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
89 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
91 /// **Why is this bad?** Gankro says:
93 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
94 /// pointers and indirection.
95 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
97 /// > "only" amortized for push/pop, should be faster in the general case for
98 /// almost every possible
99 /// > workload, and isn't even amortized at all if you can predict the capacity
102 /// > `LinkedList`s are only really good if you're doing a lot of merging or
103 /// splitting of lists.
104 /// > This is because they can just mangle some pointers instead of actually
105 /// copying the data. Even
106 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
107 /// can still be better
108 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
110 /// **Known problems:** False positives – the instances where using a
111 /// `LinkedList` makes sense are few and far between, but they can still happen.
115 /// let x = LinkedList::new();
117 declare_clippy_lint! {
120 "usage of LinkedList, usually a vector is faster, or a more specialized data \
121 structure like a VecDeque"
124 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
126 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
129 /// **Known problems:** None.
133 /// fn foo(bar: &Box<T>) { ... }
139 /// fn foo(bar: &T) { ... }
141 declare_clippy_lint! {
144 "a borrow of a boxed type"
147 impl LintPass for TypePass {
148 fn get_lints(&self) -> LintArray {
149 lint_array!(BOX_VEC, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
153 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
154 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
155 // skip trait implementations, see #605
156 if let Some(hir::Node::Item(item)) = cx.tcx.hir.find(cx.tcx.hir.get_parent(id)) {
157 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
162 check_fn_decl(cx, decl);
165 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
166 check_ty(cx, &field.ty, false);
169 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
171 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
172 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
177 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
178 if let Some(ref ty) = local.ty {
179 check_ty(cx, ty, true);
184 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
185 for input in &decl.inputs {
186 check_ty(cx, input, false);
189 if let FunctionRetTy::Return(ref ty) = decl.output {
190 check_ty(cx, ty, false);
194 /// Check if `qpath` has last segment with type parameter matching `path`
195 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
196 let last = last_path_segment(qpath);
198 if let Some(ref params) = last.args;
199 if !params.parenthesized;
200 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
201 GenericArg::Type(ty) => Some(ty),
202 GenericArg::Lifetime(_) => None,
204 if let TyKind::Path(ref qpath) = ty.node;
205 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir.node_to_hir_id(ty.id)));
206 if match_def_path(cx.tcx, did, path);
214 /// Recursively check for `TypePass` lints in the given type. Stop at the first
217 /// The parameter `is_local` distinguishes the context of the type; types from
218 /// local bindings should only be checked for the `BORROWED_BOX` lint.
219 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
220 if in_macro(ast_ty.span) {
224 TyKind::Path(ref qpath) if !is_local => {
225 let hir_id = cx.tcx.hir.node_to_hir_id(ast_ty.id);
226 let def = cx.tables.qpath_def(qpath, hir_id);
227 if let Some(def_id) = opt_def_id(def) {
228 if Some(def_id) == cx.tcx.lang_items().owned_box() {
229 if match_type_parameter(cx, qpath, &paths::VEC) {
234 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
235 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
237 return; // don't recurse into the type
239 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
240 if match_type_parameter(cx, qpath, &paths::OPTION) {
245 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
246 enum if you need to distinguish all 3 cases",
248 return; // don't recurse into the type
250 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
255 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
256 "a VecDeque might work",
258 return; // don't recurse into the type
262 QPath::Resolved(Some(ref ty), ref p) => {
263 check_ty(cx, ty, is_local);
264 for ty in p.segments.iter().flat_map(|seg| {
267 .map_or_else(|| [].iter(), |params| params.args.iter())
268 .filter_map(|arg| match arg {
269 GenericArg::Type(ty) => Some(ty),
270 GenericArg::Lifetime(_) => None,
273 check_ty(cx, ty, is_local);
276 QPath::Resolved(None, ref p) => for ty in p.segments.iter().flat_map(|seg| {
279 .map_or_else(|| [].iter(), |params| params.args.iter())
280 .filter_map(|arg| match arg {
281 GenericArg::Type(ty) => Some(ty),
282 GenericArg::Lifetime(_) => None,
285 check_ty(cx, ty, is_local);
287 QPath::TypeRelative(ref ty, ref seg) => {
288 check_ty(cx, ty, is_local);
289 if let Some(ref params) = seg.args {
290 for ty in params.args.iter().filter_map(|arg| match arg {
291 GenericArg::Type(ty) => Some(ty),
292 GenericArg::Lifetime(_) => None,
294 check_ty(cx, ty, is_local);
300 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
302 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => check_ty(cx, ty, is_local),
303 TyKind::Tup(ref tys) => for ty in tys {
304 check_ty(cx, ty, is_local);
310 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
311 match mut_ty.ty.node {
312 TyKind::Path(ref qpath) => {
313 let hir_id = cx.tcx.hir.node_to_hir_id(mut_ty.ty.id);
314 let def = cx.tables.qpath_def(qpath, hir_id);
316 if let Some(def_id) = opt_def_id(def);
317 if Some(def_id) == cx.tcx.lang_items().owned_box();
318 if let QPath::Resolved(None, ref path) = *qpath;
319 if let [ref bx] = *path.segments;
320 if let Some(ref params) = bx.args;
321 if !params.parenthesized;
322 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
323 GenericArg::Type(ty) => Some(ty),
324 GenericArg::Lifetime(_) => None,
327 if is_any_trait(inner) {
328 // Ignore `Box<Any>` types, see #1884 for details.
332 let ltopt = if lt.is_elided() {
335 format!("{} ", lt.name.ident().name.as_str())
337 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
342 span_lint_and_sugg(cx,
345 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
347 format!("&{}{}{}", ltopt, mutopt, &snippet(cx, inner.span, ".."))
349 return; // don't recurse into the type
352 check_ty(cx, &mut_ty.ty, is_local);
354 _ => check_ty(cx, &mut_ty.ty, is_local),
358 // Returns true if given type is `Any` trait.
359 fn is_any_trait(t: &hir::Ty) -> bool {
361 if let TyKind::TraitObject(ref traits, _) = t.node;
362 if traits.len() >= 1;
363 // Only Send/Sync can be used as additional traits, so it is enough to
364 // check only the first trait.
365 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
374 #[allow(missing_copy_implementations)]
377 /// **What it does:** Checks for binding a unit value.
379 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
380 /// binding one is kind of pointless.
382 /// **Known problems:** None.
388 declare_clippy_lint! {
391 "creating a let binding to a value of unit type, which usually can't be used afterwards"
394 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
395 if let DeclKind::Local(ref local) = decl.node {
396 if is_unit(cx.tables.pat_ty(&local.pat)) {
397 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
400 if higher::is_from_for_desugar(decl) {
408 "this let-binding has unit value. Consider omitting `let {} =`",
409 snippet(cx, local.pat.span, "..")
416 impl LintPass for LetPass {
417 fn get_lints(&self) -> LintArray {
418 lint_array!(LET_UNIT_VALUE)
422 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
423 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
424 check_let_unit(cx, decl)
428 /// **What it does:** Checks for comparisons to unit.
430 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
431 /// clumsily written constant. Mostly this happens when someone accidentally
432 /// adds semicolons at the end of the operands.
434 /// **Known problems:** None.
438 /// if { foo(); } == { bar(); } { baz(); }
442 /// { foo(); bar(); baz(); }
444 declare_clippy_lint! {
447 "comparing unit values"
450 #[allow(missing_copy_implementations)]
453 impl LintPass for UnitCmp {
454 fn get_lints(&self) -> LintArray {
455 lint_array!(UNIT_CMP)
459 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
460 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
461 if in_macro(expr.span) {
464 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
466 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
467 let result = match op {
468 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
476 "{}-comparison of unit values detected. This will always be {}",
486 /// **What it does:** Checks for passing a unit value as an argument to a function without using a unit literal (`()`).
488 /// **Why is this bad?** This is likely the result of an accidental semicolon.
490 /// **Known problems:** None.
499 declare_clippy_lint! {
502 "passing unit to a function"
507 impl LintPass for UnitArg {
508 fn get_lints(&self) -> LintArray {
509 lint_array!(UNIT_ARG)
513 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
514 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
515 if in_macro(expr.span) {
519 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
521 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
522 let map = &cx.tcx.hir;
523 // apparently stuff in the desugaring of `?` can trigger this
524 // so check for that here
525 // only the calls to `Try::from_error` is marked as desugared,
526 // so we need to check both the current Expr and its parent.
527 if !is_questionmark_desugar_marked_call(expr) {
529 let opt_parent_node = map.find(map.get_parent_node(expr.id));
530 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
531 if is_questionmark_desugar_marked_call(parent_expr);
534 // `expr` and `parent_expr` where _both_ not from
535 // desugaring `?`, so lint
540 "passing a unit value to a function",
541 "if you intended to pass a unit value, use a unit literal instead",
555 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
556 use crate::syntax_pos::hygiene::CompilerDesugaringKind;
557 if let ExprKind::Call(ref callee, _) = expr.node {
558 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
564 fn is_unit(ty: Ty<'_>) -> bool {
566 ty::Tuple(slice) if slice.is_empty() => true,
571 fn is_unit_literal(expr: &Expr) -> bool {
573 ExprKind::Tup(ref slice) if slice.is_empty() => true,
580 /// **What it does:** Checks for casts from any numerical to a float type where
581 /// the receiving type cannot store all values from the original type without
582 /// rounding errors. This possible rounding is to be expected, so this lint is
583 /// `Allow` by default.
585 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
586 /// or any 64-bit integer to `f64`.
588 /// **Why is this bad?** It's not bad at all. But in some applications it can be
589 /// helpful to know where precision loss can take place. This lint can help find
590 /// those places in the code.
592 /// **Known problems:** None.
596 /// let x = u64::MAX; x as f64
598 declare_clippy_lint! {
599 pub CAST_PRECISION_LOSS,
601 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
604 /// **What it does:** Checks for casts from a signed to an unsigned numerical
605 /// type. In this case, negative values wrap around to large positive values,
606 /// which can be quite surprising in practice. However, as the cast works as
607 /// defined, this lint is `Allow` by default.
609 /// **Why is this bad?** Possibly surprising results. You can activate this lint
610 /// as a one-time check to see where numerical wrapping can arise.
612 /// **Known problems:** None.
617 /// y as u128 // will return 18446744073709551615
619 declare_clippy_lint! {
622 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
625 /// **What it does:** Checks for on casts between numerical types that may
626 /// truncate large values. This is expected behavior, so the cast is `Allow` by
629 /// **Why is this bad?** In some problem domains, it is good practice to avoid
630 /// truncation. This lint can be activated to help assess where additional
631 /// checks could be beneficial.
633 /// **Known problems:** None.
637 /// fn as_u8(x: u64) -> u8 { x as u8 }
639 declare_clippy_lint! {
640 pub CAST_POSSIBLE_TRUNCATION,
642 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, \
643 or `x as i32` where `x: f32`"
646 /// **What it does:** Checks for casts from an unsigned type to a signed type of
647 /// the same size. Performing such a cast is a 'no-op' for the compiler,
648 /// i.e. nothing is changed at the bit level, and the binary representation of
649 /// the value is reinterpreted. This can cause wrapping if the value is too big
650 /// for the target signed type. However, the cast works as defined, so this lint
651 /// is `Allow` by default.
653 /// **Why is this bad?** While such a cast is not bad in itself, the results can
654 /// be surprising when this is not the intended behavior, as demonstrated by the
657 /// **Known problems:** None.
661 /// u32::MAX as i32 // will yield a value of `-1`
663 declare_clippy_lint! {
664 pub CAST_POSSIBLE_WRAP,
666 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` \
670 /// **What it does:** Checks for on casts between numerical types that may
671 /// be replaced by safe conversion functions.
673 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
674 /// conversions, including silently lossy conversions. Conversion functions such
675 /// as `i32::from` will only perform lossless conversions. Using the conversion
676 /// functions prevents conversions from turning into silent lossy conversions if
677 /// the types of the input expressions ever change, and make it easier for
678 /// people reading the code to know that the conversion is lossless.
680 /// **Known problems:** None.
684 /// fn as_u64(x: u8) -> u64 { x as u64 }
687 /// Using `::from` would look like this:
690 /// fn as_u64(x: u8) -> u64 { u64::from(x) }
692 declare_clippy_lint! {
695 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
698 /// **What it does:** Checks for casts to the same type.
700 /// **Why is this bad?** It's just unnecessary.
702 /// **Known problems:** None.
706 /// let _ = 2i32 as i32
708 declare_clippy_lint! {
709 pub UNNECESSARY_CAST,
711 "cast to the same type, e.g. `x as i32` where `x: i32`"
714 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
715 /// more-strictly-aligned pointer
717 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
720 /// **Known problems:** None.
724 /// let _ = (&1u8 as *const u8) as *const u16;
725 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
727 declare_clippy_lint! {
728 pub CAST_PTR_ALIGNMENT,
730 "cast from a pointer to a more-strictly-aligned pointer"
733 /// **What it does:** Checks for casts of function pointers to something other than usize
735 /// **Why is this bad?**
736 /// Casting a function pointer to anything other than usize/isize is not portable across
737 /// architectures, because you end up losing bits if the target type is too small or end up with a
738 /// bunch of extra bits that waste space and add more instructions to the final binary than
739 /// strictly necessary for the problem
741 /// Casting to isize also doesn't make sense since there are no signed addresses.
747 /// fn fun() -> i32 {}
748 /// let a = fun as i64;
751 /// fn fun2() -> i32 {}
752 /// let a = fun2 as usize;
754 declare_clippy_lint! {
755 pub FN_TO_NUMERIC_CAST,
757 "casting a function pointer to a numeric type other than usize"
760 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
763 /// **Why is this bad?**
764 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
765 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
766 /// a comment) to perform the truncation.
772 /// fn fn1() -> i16 { 1 };
773 /// let _ = fn1 as i32;
775 /// // Better: Cast to usize first, then comment with the reason for the truncation
776 /// fn fn2() -> i16 { 1 };
777 /// let fn_ptr = fn2 as usize;
778 /// let fn_ptr_truncated = fn_ptr as i32;
780 declare_clippy_lint! {
781 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
783 "casting a function pointer to a numeric type not wide enough to store the address"
786 /// Returns the size in bits of an integral type.
787 /// Will return 0 if the type is not an int or uint variant
788 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
790 ty::Int(i) => match i {
791 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
798 ty::Uint(i) => match i {
799 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
810 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
812 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
817 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
818 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
819 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
820 let arch_dependent_str = "on targets with 64-bit wide pointers ";
821 let from_nbits_str = if arch_dependent {
823 } else if is_isize_or_usize(cast_from) {
824 "32 or 64".to_owned()
826 int_ty_to_nbits(cast_from, cx.tcx).to_string()
833 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
834 is only {4} bits wide)",
836 if cast_to_f64 { "f64" } else { "f32" },
848 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
849 if let ExprKind::Binary(_, _, _) = op.node {
850 if snip.starts_with('(') && snip.ends_with(')') {
857 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
858 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
859 if in_constant(cx, expr.id) { return }
860 // The suggestion is to use a function call, so if the original expression
861 // has parens on the outside, they are no longer needed.
862 let opt = snippet_opt(cx, op.span);
863 let sugg = if let Some(ref snip) = opt {
864 if should_strip_parens(op, snip) {
865 &snip[1..snip.len() - 1]
877 &format!("casting {} to {} may become silently lossy if types change", cast_from, cast_to),
879 format!("{}::from({})", cast_to, sugg),
889 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
890 let arch_64_suffix = " on targets with 64-bit wide pointers";
891 let arch_32_suffix = " on targets with 32-bit wide pointers";
892 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
893 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
894 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
895 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
896 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
897 (true, true) | (false, false) => (
898 to_nbits < from_nbits,
900 to_nbits == from_nbits && cast_unsigned_to_signed,
910 to_nbits <= 32 && cast_unsigned_to_signed,
916 cast_unsigned_to_signed,
917 if from_nbits == 64 {
927 CAST_POSSIBLE_TRUNCATION,
930 "casting {} to {} may truncate the value{}",
933 match suffix_truncation {
934 ArchSuffix::_32 => arch_32_suffix,
935 ArchSuffix::_64 => arch_64_suffix,
936 ArchSuffix::None => "",
947 "casting {} to {} may wrap around the value{}",
951 ArchSuffix::_32 => arch_32_suffix,
952 ArchSuffix::_64 => arch_64_suffix,
953 ArchSuffix::None => "",
960 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
961 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
962 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
963 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
964 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
966 span_lossless_lint(cx, expr, op, cast_from, cast_to);
970 impl LintPass for CastPass {
971 fn get_lints(&self) -> LintArray {
975 CAST_POSSIBLE_TRUNCATION,
985 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
986 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
987 if let ExprKind::Cast(ref ex, _) = expr.node {
988 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
989 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
990 if let ExprKind::Lit(ref lit) = ex.node {
991 use crate::syntax::ast::{LitIntType, LitKind};
993 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
994 _ => if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
999 &format!("casting to the same type is unnecessary (`{}` -> `{}`)", cast_from, cast_to),
1004 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1005 match (cast_from.is_integral(), cast_to.is_integral()) {
1007 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1008 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1013 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1014 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1016 if from_nbits < to_nbits {
1017 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1023 CAST_POSSIBLE_TRUNCATION,
1025 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1027 if !cast_to.is_signed() {
1032 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1037 if cast_from.is_signed() && !cast_to.is_signed() {
1042 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1045 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1046 check_lossless(cx, expr, ex, cast_from, cast_to);
1049 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty)
1053 CAST_POSSIBLE_TRUNCATION,
1055 "casting f64 to f32 may truncate the value",
1058 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty)
1060 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1067 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1068 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1069 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi());
1070 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi());
1071 if from_align < to_align;
1072 // with c_void, we inherently need to trust the user
1074 match_type(cx, from_ptr_ty.ty, &paths::C_VOID)
1075 || match_type(cx, from_ptr_ty.ty, &paths::C_VOID_LIBC)
1082 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1090 fn lint_fn_to_numeric_cast(cx: &LateContext<'_, '_>, expr: &Expr, cast_expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1091 // We only want to check casts to `ty::Uint` or `ty::Int`
1093 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1096 match cast_from.sty {
1097 ty::FnDef(..) | ty::FnPtr(_) => {
1098 let from_snippet = snippet(cx, cast_expr.span, "x");
1100 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1101 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1104 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1106 &format!("casting function pointer `{}` to `{}`, which truncates the value", from_snippet, cast_to),
1108 format!("{} as usize", from_snippet)
1111 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1116 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1118 format!("{} as usize", from_snippet)
1126 /// **What it does:** Checks for types used in structs, parameters and `let`
1127 /// declarations above a certain complexity threshold.
1129 /// **Why is this bad?** Too complex types make the code less readable. Consider
1130 /// using a `type` definition to simplify them.
1132 /// **Known problems:** None.
1136 /// struct Foo { inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>> }
1138 declare_clippy_lint! {
1139 pub TYPE_COMPLEXITY,
1141 "usage of very complex types that might be better factored into `type` definitions"
1144 #[allow(missing_copy_implementations)]
1145 pub struct TypeComplexityPass {
1149 impl TypeComplexityPass {
1150 pub fn new(threshold: u64) -> Self {
1157 impl LintPass for TypeComplexityPass {
1158 fn get_lints(&self) -> LintArray {
1159 lint_array!(TYPE_COMPLEXITY)
1163 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1166 cx: &LateContext<'a, 'tcx>,
1173 self.check_fndecl(cx, decl);
1176 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1177 // enum variants are also struct fields now
1178 self.check_type(cx, &field.ty);
1181 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1183 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1184 // functions, enums, structs, impls and traits are covered
1189 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1191 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1192 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1193 // methods with default impl are covered by check_fn
1198 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1200 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1201 // methods are covered by check_fn
1206 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1207 if let Some(ref ty) = local.ty {
1208 self.check_type(cx, ty);
1213 impl<'a, 'tcx> TypeComplexityPass {
1214 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1215 for arg in &decl.inputs {
1216 self.check_type(cx, arg);
1218 if let Return(ref ty) = decl.output {
1219 self.check_type(cx, ty);
1223 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1224 if in_macro(ty.span) {
1228 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1229 visitor.visit_ty(ty);
1233 if score > self.threshold {
1238 "very complex type used. Consider factoring parts into `type` definitions",
1244 /// Walks a type and assigns a complexity score to it.
1245 struct TypeComplexityVisitor {
1246 /// total complexity score of the type
1248 /// current nesting level
1252 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1253 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1254 let (add_score, sub_nest) = match ty.node {
1255 // _, &x and *x have only small overhead; don't mess with nesting level
1256 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1258 // the "normal" components of a type: named types, arrays/tuples
1259 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1261 // function types bring a lot of overhead
1262 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1264 TyKind::TraitObject(ref param_bounds, _) => {
1265 let has_lifetime_parameters = param_bounds
1267 .any(|bound| bound.bound_generic_params.iter().any(|gen| match gen.kind {
1268 GenericParamKind::Lifetime { .. } => true,
1271 if has_lifetime_parameters {
1272 // complex trait bounds like A<'a, 'b>
1275 // simple trait bounds like A + B
1282 self.score += add_score;
1283 self.nest += sub_nest;
1285 self.nest -= sub_nest;
1287 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1288 NestedVisitorMap::None
1292 /// **What it does:** Checks for expressions where a character literal is cast
1293 /// to `u8` and suggests using a byte literal instead.
1295 /// **Why is this bad?** In general, casting values to smaller types is
1296 /// error-prone and should be avoided where possible. In the particular case of
1297 /// converting a character literal to u8, it is easy to avoid by just using a
1298 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1299 /// than `'a' as u8`.
1301 /// **Known problems:** None.
1308 /// A better version, using the byte literal:
1313 declare_clippy_lint! {
1316 "casting a character literal to u8"
1319 pub struct CharLitAsU8;
1321 impl LintPass for CharLitAsU8 {
1322 fn get_lints(&self) -> LintArray {
1323 lint_array!(CHAR_LIT_AS_U8)
1327 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1328 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1329 use crate::syntax::ast::{LitKind, UintTy};
1331 if let ExprKind::Cast(ref e, _) = expr.node {
1332 if let ExprKind::Lit(ref l) = e.node {
1333 if let LitKind::Char(_) = l.node {
1334 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1335 let msg = "casting character literal to u8. `char`s \
1336 are 4 bytes wide in rust, so casting to u8 \
1338 let help = format!("Consider using a byte literal instead:\nb{}", snippet(cx, e.span, "'x'"));
1339 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1347 /// **What it does:** Checks for comparisons where one side of the relation is
1348 /// either the minimum or maximum value for its type and warns if it involves a
1349 /// case that is always true or always false. Only integer and boolean types are
1352 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1353 /// that is is possible for `x` to be less than the minimum. Expressions like
1354 /// `max < x` are probably mistakes.
1356 /// **Known problems:** For `usize` the size of the current compile target will
1357 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1358 /// a comparison to detect target pointer width will trigger this lint. One can
1359 /// use `mem::sizeof` and compare its value or conditional compilation
1361 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1366 /// 100 > std::i32::MAX
1368 declare_clippy_lint! {
1369 pub ABSURD_EXTREME_COMPARISONS,
1371 "a comparison with a maximum or minimum value that is always true or false"
1374 pub struct AbsurdExtremeComparisons;
1376 impl LintPass for AbsurdExtremeComparisons {
1377 fn get_lints(&self) -> LintArray {
1378 lint_array!(ABSURD_EXTREME_COMPARISONS)
1387 struct ExtremeExpr<'a> {
1392 enum AbsurdComparisonResult {
1395 InequalityImpossible,
1399 fn is_cast_between_fixed_and_target<'a, 'tcx>(
1400 cx: &LateContext<'a, 'tcx>,
1404 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1405 let precast_ty = cx.tables.expr_ty(cast_exp);
1406 let cast_ty = cx.tables.expr_ty(expr);
1408 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty)
1414 fn detect_absurd_comparison<'a, 'tcx>(
1415 cx: &LateContext<'a, 'tcx>,
1419 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1420 use crate::types::ExtremeType::*;
1421 use crate::types::AbsurdComparisonResult::*;
1422 use crate::utils::comparisons::*;
1424 // absurd comparison only makes sense on primitive types
1425 // primitive types don't implement comparison operators with each other
1426 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1430 // comparisons between fix sized types and target sized types are considered unanalyzable
1431 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1435 let normalized = normalize_comparison(op, lhs, rhs);
1436 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1442 let lx = detect_extreme_expr(cx, normalized_lhs);
1443 let rx = detect_extreme_expr(cx, normalized_rhs);
1448 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1449 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1455 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1456 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1457 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1458 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1462 Rel::Ne | Rel::Eq => return None,
1466 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1467 use crate::types::ExtremeType::*;
1469 let ty = cx.tables.expr_ty(expr);
1471 let cv = constant(cx, cx.tables, expr)?.0;
1473 let which = match (&ty.sty, cv) {
1474 (&ty::Bool, Constant::Bool(false)) |
1475 (&ty::Uint(_), Constant::Int(0)) => Minimum,
1476 (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) => Minimum,
1478 (&ty::Bool, Constant::Bool(true)) => Maximum,
1479 (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) => Maximum,
1480 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1490 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1491 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1492 use crate::types::ExtremeType::*;
1493 use crate::types::AbsurdComparisonResult::*;
1495 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1496 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1497 if !in_macro(expr.span) {
1498 let msg = "this comparison involving the minimum or maximum element for this \
1499 type contains a case that is always true or always false";
1501 let conclusion = match result {
1502 AlwaysFalse => "this comparison is always false".to_owned(),
1503 AlwaysTrue => "this comparison is always true".to_owned(),
1504 InequalityImpossible => format!(
1505 "the case where the two sides are not equal never occurs, consider using {} == {} \
1507 snippet(cx, lhs.span, "lhs"),
1508 snippet(cx, rhs.span, "rhs")
1513 "because {} is the {} value for this type, {}",
1514 snippet(cx, culprit.expr.span, "x"),
1515 match culprit.which {
1516 Minimum => "minimum",
1517 Maximum => "maximum",
1522 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1529 /// **What it does:** Checks for comparisons where the relation is always either
1530 /// true or false, but where one side has been upcast so that the comparison is
1531 /// necessary. Only integer types are checked.
1533 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1534 /// will mistakenly imply that it is possible for `x` to be outside the range of
1537 /// **Known problems:**
1538 /// https://github.com/rust-lang-nursery/rust-clippy/issues/886
1542 /// let x : u8 = ...; (x as u32) > 300
1544 declare_clippy_lint! {
1545 pub INVALID_UPCAST_COMPARISONS,
1547 "a comparison involving an upcast which is always true or false"
1550 pub struct InvalidUpcastComparisons;
1552 impl LintPass for InvalidUpcastComparisons {
1553 fn get_lints(&self) -> LintArray {
1554 lint_array!(INVALID_UPCAST_COMPARISONS)
1558 #[derive(Copy, Clone, Debug, Eq)]
1565 #[allow(clippy::cast_sign_loss)]
1566 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1569 } else if u > (i128::max_value() as u128) {
1577 impl PartialEq for FullInt {
1578 fn eq(&self, other: &Self) -> bool {
1579 self.partial_cmp(other)
1580 .expect("partial_cmp only returns Some(_)") == Ordering::Equal
1584 impl PartialOrd for FullInt {
1585 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1586 Some(match (self, other) {
1587 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1588 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1589 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1590 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1594 impl Ord for FullInt {
1595 fn cmp(&self, other: &Self) -> Ordering {
1596 self.partial_cmp(other)
1597 .expect("partial_cmp for FullInt can never return None")
1602 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1603 use crate::syntax::ast::{IntTy, UintTy};
1606 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1607 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1608 let cast_ty = cx.tables.expr_ty(expr);
1609 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1610 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1613 match pre_cast_ty.sty {
1614 ty::Int(int_ty) => Some(match int_ty {
1615 IntTy::I8 => (FullInt::S(i128::from(i8::min_value())), FullInt::S(i128::from(i8::max_value()))),
1617 FullInt::S(i128::from(i16::min_value())),
1618 FullInt::S(i128::from(i16::max_value())),
1621 FullInt::S(i128::from(i32::min_value())),
1622 FullInt::S(i128::from(i32::max_value())),
1625 FullInt::S(i128::from(i64::min_value())),
1626 FullInt::S(i128::from(i64::max_value())),
1628 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1629 IntTy::Isize => (FullInt::S(isize::min_value() as i128), FullInt::S(isize::max_value() as i128)),
1631 ty::Uint(uint_ty) => Some(match uint_ty {
1632 UintTy::U8 => (FullInt::U(u128::from(u8::min_value())), FullInt::U(u128::from(u8::max_value()))),
1634 FullInt::U(u128::from(u16::min_value())),
1635 FullInt::U(u128::from(u16::max_value())),
1638 FullInt::U(u128::from(u32::min_value())),
1639 FullInt::U(u128::from(u32::max_value())),
1642 FullInt::U(u128::from(u64::min_value())),
1643 FullInt::U(u128::from(u64::max_value())),
1645 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1646 UintTy::Usize => (FullInt::U(usize::min_value() as u128), FullInt::U(usize::max_value() as u128)),
1655 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1656 let val = constant(cx, cx.tables, expr)?.0;
1657 if let Constant::Int(const_int) = val {
1658 match cx.tables.expr_ty(expr).sty {
1659 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1660 ty::Uint(_) => Some(FullInt::U(const_int)),
1668 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1669 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1672 INVALID_UPCAST_COMPARISONS,
1675 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1676 snippet(cx, cast_val.span, "the expression"),
1677 if always { "true" } else { "false" },
1683 fn upcast_comparison_bounds_err<'a, 'tcx>(
1684 cx: &LateContext<'a, 'tcx>,
1686 rel: comparisons::Rel,
1687 lhs_bounds: Option<(FullInt, FullInt)>,
1692 use crate::utils::comparisons::*;
1694 if let Some((lb, ub)) = lhs_bounds {
1695 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1696 if rel == Rel::Eq || rel == Rel::Ne {
1697 if norm_rhs_val < lb || norm_rhs_val > ub {
1698 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1700 } else if match rel {
1701 Rel::Lt => if invert {
1706 Rel::Le => if invert {
1711 Rel::Eq | Rel::Ne => unreachable!(),
1713 err_upcast_comparison(cx, span, lhs, true)
1714 } else if match rel {
1715 Rel::Lt => if invert {
1720 Rel::Le => if invert {
1725 Rel::Eq | Rel::Ne => unreachable!(),
1727 err_upcast_comparison(cx, span, lhs, false)
1733 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1734 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1735 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1736 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1737 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1743 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1744 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1746 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1747 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1752 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1753 /// over different hashers and implicitly defaulting to the default hashing
1754 /// algorithm (SipHash).
1756 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1759 /// **Known problems:** Suggestions for replacing constructors can contain
1760 /// false-positives. Also applying suggestions can require modification of other
1761 /// pieces of code, possibly including external crates.
1765 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1767 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1769 declare_clippy_lint! {
1770 pub IMPLICIT_HASHER,
1772 "missing generalization over different hashers"
1775 pub struct ImplicitHasher;
1777 impl LintPass for ImplicitHasher {
1778 fn get_lints(&self) -> LintArray {
1779 lint_array!(IMPLICIT_HASHER)
1783 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1784 #[allow(clippy::cast_possible_truncation)]
1785 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1786 use crate::syntax_pos::BytePos;
1788 fn suggestion<'a, 'tcx>(
1789 cx: &LateContext<'a, 'tcx>,
1790 db: &mut DiagnosticBuilder<'_>,
1791 generics_span: Span,
1792 generics_suggestion_span: Span,
1793 target: &ImplicitHasherType<'_>,
1794 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1796 let generics_snip = snippet(cx, generics_span, "");
1798 let generics_snip = if generics_snip.is_empty() {
1801 &generics_snip[1..generics_snip.len() - 1]
1806 "consider adding a type parameter".to_string(),
1809 generics_suggestion_span,
1811 "<{}{}S: ::std::hash::BuildHasher{}>",
1813 if generics_snip.is_empty() { "" } else { ", " },
1814 if vis.suggestions.is_empty() {
1817 // request users to add `Default` bound so that generic constructors can be used
1824 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1829 if !vis.suggestions.is_empty() {
1830 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1834 if !cx.access_levels.is_exported(item.id) {
1839 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1840 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1843 for target in &vis.found {
1844 if differing_macro_contexts(item.span, target.span()) {
1848 let generics_suggestion_span = generics.span.substitute_dummy({
1849 let pos = snippet_opt(cx, item.span.until(target.span()))
1850 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
1851 if let Some(pos) = pos {
1852 Span::new(pos, pos, item.span.data().ctxt)
1858 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1859 for item in items.iter().map(|item| cx.tcx.hir.impl_item(item.id)) {
1860 ctr_vis.visit_impl_item(item);
1867 &format!("impl for `{}` should be generalized over different hashers", target.type_name()),
1869 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1874 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
1875 let body = cx.tcx.hir.body(body_id);
1877 for ty in &decl.inputs {
1878 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1881 for target in &vis.found {
1882 let generics_suggestion_span = generics.span.substitute_dummy({
1883 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
1885 let i = snip.find("fn")?;
1886 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
1888 .expect("failed to create span for type parameters");
1889 Span::new(pos, pos, item.span.data().ctxt)
1892 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1893 ctr_vis.visit_body(body);
1900 "parameter of type `{}` should be generalized over different hashers",
1904 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1915 enum ImplicitHasherType<'tcx> {
1916 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
1917 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
1920 impl<'tcx> ImplicitHasherType<'tcx> {
1921 /// Checks that `ty` is a target type without a BuildHasher.
1922 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
1923 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
1924 let params: Vec<_> = path.segments.last().as_ref()?.args.as_ref()?
1925 .args.iter().filter_map(|arg| match arg {
1926 GenericArg::Type(ty) => Some(ty),
1927 GenericArg::Lifetime(_) => None,
1929 let params_len = params.len();
1931 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
1933 if match_path(path, &paths::HASHMAP) && params_len == 2 {
1934 Some(ImplicitHasherType::HashMap(
1937 snippet(cx, params[0].span, "K"),
1938 snippet(cx, params[1].span, "V"),
1940 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
1941 Some(ImplicitHasherType::HashSet(hir_ty.span, ty, snippet(cx, params[0].span, "T")))
1950 fn type_name(&self) -> &'static str {
1952 ImplicitHasherType::HashMap(..) => "HashMap",
1953 ImplicitHasherType::HashSet(..) => "HashSet",
1957 fn type_arguments(&self) -> String {
1959 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
1960 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
1964 fn ty(&self) -> Ty<'tcx> {
1966 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
1970 fn span(&self) -> Span {
1972 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
1977 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
1978 cx: &'a LateContext<'a, 'tcx>,
1979 found: Vec<ImplicitHasherType<'tcx>>,
1982 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
1983 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
1984 Self { cx, found: vec![] }
1988 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
1989 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
1990 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
1991 self.found.push(target);
1997 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1998 NestedVisitorMap::None
2002 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2003 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2004 cx: &'a LateContext<'a, 'tcx>,
2005 body: &'a TypeckTables<'tcx>,
2006 target: &'b ImplicitHasherType<'tcx>,
2007 suggestions: BTreeMap<Span, String>,
2010 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2011 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2016 suggestions: BTreeMap::new(),
2021 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2022 fn visit_body(&mut self, body: &'tcx Body) {
2023 self.body = self.cx.tcx.body_tables(body.id());
2024 walk_body(self, body);
2027 fn visit_expr(&mut self, e: &'tcx Expr) {
2029 if let ExprKind::Call(ref fun, ref args) = e.node;
2030 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2031 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2033 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2037 if match_path(ty_path, &paths::HASHMAP) {
2038 if method.ident.name == "new" {
2040 .insert(e.span, "HashMap::default()".to_string());
2041 } else if method.ident.name == "with_capacity" {
2042 self.suggestions.insert(
2045 "HashMap::with_capacity_and_hasher({}, Default::default())",
2046 snippet(self.cx, args[0].span, "capacity"),
2050 } else if match_path(ty_path, &paths::HASHSET) {
2051 if method.ident.name == "new" {
2053 .insert(e.span, "HashSet::default()".to_string());
2054 } else if method.ident.name == "with_capacity" {
2055 self.suggestions.insert(
2058 "HashSet::with_capacity_and_hasher({}, Default::default())",
2059 snippet(self.cx, args[0].span, "capacity"),
2070 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2071 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)