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
39 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
41 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
42 /// the heap. So if you `Box` it, you just add another level of indirection
43 /// without any benefit whatsoever.
45 /// **Known problems:** None.
50 /// values: Box<Vec<Foo>>,
61 declare_clippy_lint! {
64 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
67 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
70 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
71 /// represents an optional optional value which is logically the same thing as an optional
72 /// value but has an unneeded extra level of wrapping.
74 /// **Known problems:** None.
78 /// fn x() -> Option<Option<u32>> {
81 declare_clippy_lint! {
84 "usage of `Option<Option<T>>`"
87 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
88 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
90 /// **Why is this bad?** Gankro says:
92 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
93 /// pointers and indirection.
94 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
96 /// > "only" amortized for push/pop, should be faster in the general case for
97 /// almost every possible
98 /// > workload, and isn't even amortized at all if you can predict the capacity
101 /// > `LinkedList`s are only really good if you're doing a lot of merging or
102 /// splitting of lists.
103 /// > This is because they can just mangle some pointers instead of actually
104 /// copying the data. Even
105 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
106 /// can still be better
107 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
109 /// **Known problems:** False positives – the instances where using a
110 /// `LinkedList` makes sense are few and far between, but they can still happen.
114 /// let x = LinkedList::new();
116 declare_clippy_lint! {
119 "usage of LinkedList, usually a vector is faster, or a more specialized data \
120 structure like a VecDeque"
123 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
125 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
128 /// **Known problems:** None.
132 /// fn foo(bar: &Box<T>) { ... }
138 /// fn foo(bar: &T) { ... }
140 declare_clippy_lint! {
143 "a borrow of a boxed type"
146 impl LintPass for TypePass {
147 fn get_lints(&self) -> LintArray {
148 lint_array!(BOX_VEC, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
152 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
153 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
154 // skip trait implementations, see #605
155 if let Some(hir::Node::Item(item)) = cx.tcx.hir.find(cx.tcx.hir.get_parent(id)) {
156 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
161 check_fn_decl(cx, decl);
164 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
165 check_ty(cx, &field.ty, false);
168 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
170 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
171 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
176 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
177 if let Some(ref ty) = local.ty {
178 check_ty(cx, ty, true);
183 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
184 for input in &decl.inputs {
185 check_ty(cx, input, false);
188 if let FunctionRetTy::Return(ref ty) = decl.output {
189 check_ty(cx, ty, false);
193 /// Check if `qpath` has last segment with type parameter matching `path`
194 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
195 let last = last_path_segment(qpath);
197 if let Some(ref params) = last.args;
198 if !params.parenthesized;
199 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
200 GenericArg::Type(ty) => Some(ty),
201 GenericArg::Lifetime(_) => None,
203 if let TyKind::Path(ref qpath) = ty.node;
204 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir.node_to_hir_id(ty.id)));
205 if match_def_path(cx.tcx, did, path);
213 /// Recursively check for `TypePass` lints in the given type. Stop at the first
216 /// The parameter `is_local` distinguishes the context of the type; types from
217 /// local bindings should only be checked for the `BORROWED_BOX` lint.
218 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
219 if in_macro(ast_ty.span) {
223 TyKind::Path(ref qpath) if !is_local => {
224 let hir_id = cx.tcx.hir.node_to_hir_id(ast_ty.id);
225 let def = cx.tables.qpath_def(qpath, hir_id);
226 if let Some(def_id) = opt_def_id(def) {
227 if Some(def_id) == cx.tcx.lang_items().owned_box() {
228 if match_type_parameter(cx, qpath, &paths::VEC) {
233 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
234 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
236 return; // don't recurse into the type
238 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
239 if match_type_parameter(cx, qpath, &paths::OPTION) {
244 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
245 enum if you need to distinguish all 3 cases",
247 return; // don't recurse into the type
249 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
254 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
255 "a VecDeque might work",
257 return; // don't recurse into the type
261 QPath::Resolved(Some(ref ty), ref p) => {
262 check_ty(cx, ty, is_local);
263 for ty in p.segments.iter().flat_map(|seg| {
266 .map_or_else(|| [].iter(), |params| params.args.iter())
267 .filter_map(|arg| match arg {
268 GenericArg::Type(ty) => Some(ty),
269 GenericArg::Lifetime(_) => None,
272 check_ty(cx, ty, is_local);
275 QPath::Resolved(None, ref p) => for ty in p.segments.iter().flat_map(|seg| {
278 .map_or_else(|| [].iter(), |params| params.args.iter())
279 .filter_map(|arg| match arg {
280 GenericArg::Type(ty) => Some(ty),
281 GenericArg::Lifetime(_) => None,
284 check_ty(cx, ty, is_local);
286 QPath::TypeRelative(ref ty, ref seg) => {
287 check_ty(cx, ty, is_local);
288 if let Some(ref params) = seg.args {
289 for ty in params.args.iter().filter_map(|arg| match arg {
290 GenericArg::Type(ty) => Some(ty),
291 GenericArg::Lifetime(_) => None,
293 check_ty(cx, ty, is_local);
299 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
301 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => check_ty(cx, ty, is_local),
302 TyKind::Tup(ref tys) => for ty in tys {
303 check_ty(cx, ty, is_local);
309 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
310 match mut_ty.ty.node {
311 TyKind::Path(ref qpath) => {
312 let hir_id = cx.tcx.hir.node_to_hir_id(mut_ty.ty.id);
313 let def = cx.tables.qpath_def(qpath, hir_id);
315 if let Some(def_id) = opt_def_id(def);
316 if Some(def_id) == cx.tcx.lang_items().owned_box();
317 if let QPath::Resolved(None, ref path) = *qpath;
318 if let [ref bx] = *path.segments;
319 if let Some(ref params) = bx.args;
320 if !params.parenthesized;
321 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
322 GenericArg::Type(ty) => Some(ty),
323 GenericArg::Lifetime(_) => None,
326 if is_any_trait(inner) {
327 // Ignore `Box<Any>` types, see #1884 for details.
331 let ltopt = if lt.is_elided() {
334 format!("{} ", lt.name.ident().name.as_str())
336 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
341 span_lint_and_sugg(cx,
344 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
346 format!("&{}{}{}", ltopt, mutopt, &snippet(cx, inner.span, ".."))
348 return; // don't recurse into the type
351 check_ty(cx, &mut_ty.ty, is_local);
353 _ => check_ty(cx, &mut_ty.ty, is_local),
357 // Returns true if given type is `Any` trait.
358 fn is_any_trait(t: &hir::Ty) -> bool {
360 if let TyKind::TraitObject(ref traits, _) = t.node;
361 if traits.len() >= 1;
362 // Only Send/Sync can be used as additional traits, so it is enough to
363 // check only the first trait.
364 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
375 /// **What it does:** Checks for binding a unit value.
377 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
378 /// binding one is kind of pointless.
380 /// **Known problems:** None.
386 declare_clippy_lint! {
389 "creating a let binding to a value of unit type, which usually can't be used afterwards"
392 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
393 if let DeclKind::Local(ref local) = decl.node {
394 if is_unit(cx.tables.pat_ty(&local.pat)) {
395 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
398 if higher::is_from_for_desugar(decl) {
406 "this let-binding has unit value. Consider omitting `let {} =`",
407 snippet(cx, local.pat.span, "..")
414 impl LintPass for LetPass {
415 fn get_lints(&self) -> LintArray {
416 lint_array!(LET_UNIT_VALUE)
420 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
421 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
422 check_let_unit(cx, decl)
426 /// **What it does:** Checks for comparisons to unit.
428 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
429 /// clumsily written constant. Mostly this happens when someone accidentally
430 /// adds semicolons at the end of the operands.
432 /// **Known problems:** None.
436 /// if { foo(); } == { bar(); } { baz(); }
440 /// { foo(); bar(); baz(); }
442 declare_clippy_lint! {
445 "comparing unit values"
450 impl LintPass for UnitCmp {
451 fn get_lints(&self) -> LintArray {
452 lint_array!(UNIT_CMP)
456 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
457 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
458 if in_macro(expr.span) {
461 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
463 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
464 let result = match op {
465 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
473 "{}-comparison of unit values detected. This will always be {}",
483 /// **What it does:** Checks for passing a unit value as an argument to a function without using a unit literal (`()`).
485 /// **Why is this bad?** This is likely the result of an accidental semicolon.
487 /// **Known problems:** None.
496 declare_clippy_lint! {
499 "passing unit to a function"
504 impl LintPass for UnitArg {
505 fn get_lints(&self) -> LintArray {
506 lint_array!(UNIT_ARG)
510 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
511 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
512 if in_macro(expr.span) {
516 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
518 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
519 let map = &cx.tcx.hir;
520 // apparently stuff in the desugaring of `?` can trigger this
521 // so check for that here
522 // only the calls to `Try::from_error` is marked as desugared,
523 // so we need to check both the current Expr and its parent.
524 if !is_questionmark_desugar_marked_call(expr) {
526 let opt_parent_node = map.find(map.get_parent_node(expr.id));
527 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
528 if is_questionmark_desugar_marked_call(parent_expr);
531 // `expr` and `parent_expr` where _both_ not from
532 // desugaring `?`, so lint
537 "passing a unit value to a function",
538 "if you intended to pass a unit value, use a unit literal instead",
552 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
553 use crate::syntax_pos::hygiene::CompilerDesugaringKind;
554 if let ExprKind::Call(ref callee, _) = expr.node {
555 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
561 fn is_unit(ty: Ty<'_>) -> bool {
563 ty::Tuple(slice) if slice.is_empty() => true,
568 fn is_unit_literal(expr: &Expr) -> bool {
570 ExprKind::Tup(ref slice) if slice.is_empty() => true,
577 /// **What it does:** Checks for casts from any numerical to a float type where
578 /// the receiving type cannot store all values from the original type without
579 /// rounding errors. This possible rounding is to be expected, so this lint is
580 /// `Allow` by default.
582 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
583 /// or any 64-bit integer to `f64`.
585 /// **Why is this bad?** It's not bad at all. But in some applications it can be
586 /// helpful to know where precision loss can take place. This lint can help find
587 /// those places in the code.
589 /// **Known problems:** None.
593 /// let x = u64::MAX; x as f64
595 declare_clippy_lint! {
596 pub CAST_PRECISION_LOSS,
598 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
601 /// **What it does:** Checks for casts from a signed to an unsigned numerical
602 /// type. In this case, negative values wrap around to large positive values,
603 /// which can be quite surprising in practice. However, as the cast works as
604 /// defined, this lint is `Allow` by default.
606 /// **Why is this bad?** Possibly surprising results. You can activate this lint
607 /// as a one-time check to see where numerical wrapping can arise.
609 /// **Known problems:** None.
614 /// y as u128 // will return 18446744073709551615
616 declare_clippy_lint! {
619 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
622 /// **What it does:** Checks for on casts between numerical types that may
623 /// truncate large values. This is expected behavior, so the cast is `Allow` by
626 /// **Why is this bad?** In some problem domains, it is good practice to avoid
627 /// truncation. This lint can be activated to help assess where additional
628 /// checks could be beneficial.
630 /// **Known problems:** None.
634 /// fn as_u8(x: u64) -> u8 { x as u8 }
636 declare_clippy_lint! {
637 pub CAST_POSSIBLE_TRUNCATION,
639 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, \
640 or `x as i32` where `x: f32`"
643 /// **What it does:** Checks for casts from an unsigned type to a signed type of
644 /// the same size. Performing such a cast is a 'no-op' for the compiler,
645 /// i.e. nothing is changed at the bit level, and the binary representation of
646 /// the value is reinterpreted. This can cause wrapping if the value is too big
647 /// for the target signed type. However, the cast works as defined, so this lint
648 /// is `Allow` by default.
650 /// **Why is this bad?** While such a cast is not bad in itself, the results can
651 /// be surprising when this is not the intended behavior, as demonstrated by the
654 /// **Known problems:** None.
658 /// u32::MAX as i32 // will yield a value of `-1`
660 declare_clippy_lint! {
661 pub CAST_POSSIBLE_WRAP,
663 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` \
667 /// **What it does:** Checks for on casts between numerical types that may
668 /// be replaced by safe conversion functions.
670 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
671 /// conversions, including silently lossy conversions. Conversion functions such
672 /// as `i32::from` will only perform lossless conversions. Using the conversion
673 /// functions prevents conversions from turning into silent lossy conversions if
674 /// the types of the input expressions ever change, and make it easier for
675 /// people reading the code to know that the conversion is lossless.
677 /// **Known problems:** None.
681 /// fn as_u64(x: u8) -> u64 { x as u64 }
684 /// Using `::from` would look like this:
687 /// fn as_u64(x: u8) -> u64 { u64::from(x) }
689 declare_clippy_lint! {
692 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
695 /// **What it does:** Checks for casts to the same type.
697 /// **Why is this bad?** It's just unnecessary.
699 /// **Known problems:** None.
703 /// let _ = 2i32 as i32
705 declare_clippy_lint! {
706 pub UNNECESSARY_CAST,
708 "cast to the same type, e.g. `x as i32` where `x: i32`"
711 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
712 /// more-strictly-aligned pointer
714 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
717 /// **Known problems:** None.
721 /// let _ = (&1u8 as *const u8) as *const u16;
722 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
724 declare_clippy_lint! {
725 pub CAST_PTR_ALIGNMENT,
727 "cast from a pointer to a more-strictly-aligned pointer"
730 /// **What it does:** Checks for casts of function pointers to something other than usize
732 /// **Why is this bad?**
733 /// Casting a function pointer to anything other than usize/isize is not portable across
734 /// architectures, because you end up losing bits if the target type is too small or end up with a
735 /// bunch of extra bits that waste space and add more instructions to the final binary than
736 /// strictly necessary for the problem
738 /// Casting to isize also doesn't make sense since there are no signed addresses.
744 /// fn fun() -> i32 {}
745 /// let a = fun as i64;
748 /// fn fun2() -> i32 {}
749 /// let a = fun2 as usize;
751 declare_clippy_lint! {
752 pub FN_TO_NUMERIC_CAST,
754 "casting a function pointer to a numeric type other than usize"
757 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
760 /// **Why is this bad?**
761 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
762 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
763 /// a comment) to perform the truncation.
769 /// fn fn1() -> i16 { 1 };
770 /// let _ = fn1 as i32;
772 /// // Better: Cast to usize first, then comment with the reason for the truncation
773 /// fn fn2() -> i16 { 1 };
774 /// let fn_ptr = fn2 as usize;
775 /// let fn_ptr_truncated = fn_ptr as i32;
777 declare_clippy_lint! {
778 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
780 "casting a function pointer to a numeric type not wide enough to store the address"
783 /// Returns the size in bits of an integral type.
784 /// Will return 0 if the type is not an int or uint variant
785 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
787 ty::Int(i) => match i {
788 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
795 ty::Uint(i) => match i {
796 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
807 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
809 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
814 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
815 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
816 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
817 let arch_dependent_str = "on targets with 64-bit wide pointers ";
818 let from_nbits_str = if arch_dependent {
820 } else if is_isize_or_usize(cast_from) {
821 "32 or 64".to_owned()
823 int_ty_to_nbits(cast_from, cx.tcx).to_string()
830 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
831 is only {4} bits wide)",
833 if cast_to_f64 { "f64" } else { "f32" },
845 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
846 if let ExprKind::Binary(_, _, _) = op.node {
847 if snip.starts_with('(') && snip.ends_with(')') {
854 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
855 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
856 if in_constant(cx, expr.id) { return }
857 // The suggestion is to use a function call, so if the original expression
858 // has parens on the outside, they are no longer needed.
859 let opt = snippet_opt(cx, op.span);
860 let sugg = if let Some(ref snip) = opt {
861 if should_strip_parens(op, snip) {
862 &snip[1..snip.len() - 1]
874 &format!("casting {} to {} may become silently lossy if types change", cast_from, cast_to),
876 format!("{}::from({})", cast_to, sugg),
886 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
887 let arch_64_suffix = " on targets with 64-bit wide pointers";
888 let arch_32_suffix = " on targets with 32-bit wide pointers";
889 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
890 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
891 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
892 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
893 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
894 (true, true) | (false, false) => (
895 to_nbits < from_nbits,
897 to_nbits == from_nbits && cast_unsigned_to_signed,
907 to_nbits <= 32 && cast_unsigned_to_signed,
913 cast_unsigned_to_signed,
914 if from_nbits == 64 {
924 CAST_POSSIBLE_TRUNCATION,
927 "casting {} to {} may truncate the value{}",
930 match suffix_truncation {
931 ArchSuffix::_32 => arch_32_suffix,
932 ArchSuffix::_64 => arch_64_suffix,
933 ArchSuffix::None => "",
944 "casting {} to {} may wrap around the value{}",
948 ArchSuffix::_32 => arch_32_suffix,
949 ArchSuffix::_64 => arch_64_suffix,
950 ArchSuffix::None => "",
957 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
958 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
959 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
960 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
961 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
963 span_lossless_lint(cx, expr, op, cast_from, cast_to);
967 impl LintPass for CastPass {
968 fn get_lints(&self) -> LintArray {
972 CAST_POSSIBLE_TRUNCATION,
978 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
983 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
984 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
985 if let ExprKind::Cast(ref ex, _) = expr.node {
986 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
987 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
988 if let ExprKind::Lit(ref lit) = ex.node {
989 use crate::syntax::ast::{LitIntType, LitKind};
991 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
992 _ => if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
997 &format!("casting to the same type is unnecessary (`{}` -> `{}`)", cast_from, cast_to),
1002 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1003 match (cast_from.is_integral(), cast_to.is_integral()) {
1005 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1006 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1011 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1012 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1014 if from_nbits < to_nbits {
1015 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1021 CAST_POSSIBLE_TRUNCATION,
1023 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1025 if !cast_to.is_signed() {
1030 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1035 if cast_from.is_signed() && !cast_to.is_signed() {
1040 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1043 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1044 check_lossless(cx, expr, ex, cast_from, cast_to);
1047 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty)
1051 CAST_POSSIBLE_TRUNCATION,
1053 "casting f64 to f32 may truncate the value",
1056 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty)
1058 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1065 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1066 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1067 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi());
1068 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi());
1069 if from_align < to_align;
1070 // with c_void, we inherently need to trust the user
1072 match_type(cx, from_ptr_ty.ty, &paths::C_VOID)
1073 || match_type(cx, from_ptr_ty.ty, &paths::C_VOID_LIBC)
1080 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1088 fn lint_fn_to_numeric_cast(cx: &LateContext<'_, '_>, expr: &Expr, cast_expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1089 // We only want to check casts to `ty::Uint` or `ty::Int`
1091 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1094 match cast_from.sty {
1095 ty::FnDef(..) | ty::FnPtr(_) => {
1096 let from_snippet = snippet(cx, cast_expr.span, "x");
1098 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1099 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1102 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1104 &format!("casting function pointer `{}` to `{}`, which truncates the value", from_snippet, cast_to),
1106 format!("{} as usize", from_snippet)
1109 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1114 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1116 format!("{} as usize", from_snippet)
1124 /// **What it does:** Checks for types used in structs, parameters and `let`
1125 /// declarations above a certain complexity threshold.
1127 /// **Why is this bad?** Too complex types make the code less readable. Consider
1128 /// using a `type` definition to simplify them.
1130 /// **Known problems:** None.
1134 /// struct Foo { inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>> }
1136 declare_clippy_lint! {
1137 pub TYPE_COMPLEXITY,
1139 "usage of very complex types that might be better factored into `type` definitions"
1142 pub struct TypeComplexityPass {
1146 impl TypeComplexityPass {
1147 pub fn new(threshold: u64) -> Self {
1154 impl LintPass for TypeComplexityPass {
1155 fn get_lints(&self) -> LintArray {
1156 lint_array!(TYPE_COMPLEXITY)
1160 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1163 cx: &LateContext<'a, 'tcx>,
1170 self.check_fndecl(cx, decl);
1173 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1174 // enum variants are also struct fields now
1175 self.check_type(cx, &field.ty);
1178 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1180 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1181 // functions, enums, structs, impls and traits are covered
1186 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1188 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1189 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1190 // methods with default impl are covered by check_fn
1195 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1197 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1198 // methods are covered by check_fn
1203 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1204 if let Some(ref ty) = local.ty {
1205 self.check_type(cx, ty);
1210 impl<'a, 'tcx> TypeComplexityPass {
1211 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1212 for arg in &decl.inputs {
1213 self.check_type(cx, arg);
1215 if let Return(ref ty) = decl.output {
1216 self.check_type(cx, ty);
1220 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1221 if in_macro(ty.span) {
1225 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1226 visitor.visit_ty(ty);
1230 if score > self.threshold {
1235 "very complex type used. Consider factoring parts into `type` definitions",
1241 /// Walks a type and assigns a complexity score to it.
1242 struct TypeComplexityVisitor {
1243 /// total complexity score of the type
1245 /// current nesting level
1249 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1250 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1251 let (add_score, sub_nest) = match ty.node {
1252 // _, &x and *x have only small overhead; don't mess with nesting level
1253 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1255 // the "normal" components of a type: named types, arrays/tuples
1256 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1258 // function types bring a lot of overhead
1259 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1261 TyKind::TraitObject(ref param_bounds, _) => {
1262 let has_lifetime_parameters = param_bounds
1264 .any(|bound| bound.bound_generic_params.iter().any(|gen| match gen.kind {
1265 GenericParamKind::Lifetime { .. } => true,
1268 if has_lifetime_parameters {
1269 // complex trait bounds like A<'a, 'b>
1272 // simple trait bounds like A + B
1279 self.score += add_score;
1280 self.nest += sub_nest;
1282 self.nest -= sub_nest;
1284 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1285 NestedVisitorMap::None
1289 /// **What it does:** Checks for expressions where a character literal is cast
1290 /// to `u8` and suggests using a byte literal instead.
1292 /// **Why is this bad?** In general, casting values to smaller types is
1293 /// error-prone and should be avoided where possible. In the particular case of
1294 /// converting a character literal to u8, it is easy to avoid by just using a
1295 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1296 /// than `'a' as u8`.
1298 /// **Known problems:** None.
1305 /// A better version, using the byte literal:
1310 declare_clippy_lint! {
1313 "casting a character literal to u8"
1316 pub struct CharLitAsU8;
1318 impl LintPass for CharLitAsU8 {
1319 fn get_lints(&self) -> LintArray {
1320 lint_array!(CHAR_LIT_AS_U8)
1324 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1325 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1326 use crate::syntax::ast::{LitKind, UintTy};
1328 if let ExprKind::Cast(ref e, _) = expr.node {
1329 if let ExprKind::Lit(ref l) = e.node {
1330 if let LitKind::Char(_) = l.node {
1331 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1332 let msg = "casting character literal to u8. `char`s \
1333 are 4 bytes wide in rust, so casting to u8 \
1335 let help = format!("Consider using a byte literal instead:\nb{}", snippet(cx, e.span, "'x'"));
1336 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1344 /// **What it does:** Checks for comparisons where one side of the relation is
1345 /// either the minimum or maximum value for its type and warns if it involves a
1346 /// case that is always true or always false. Only integer and boolean types are
1349 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1350 /// that is is possible for `x` to be less than the minimum. Expressions like
1351 /// `max < x` are probably mistakes.
1353 /// **Known problems:** For `usize` the size of the current compile target will
1354 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1355 /// a comparison to detect target pointer width will trigger this lint. One can
1356 /// use `mem::sizeof` and compare its value or conditional compilation
1358 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1363 /// 100 > std::i32::MAX
1365 declare_clippy_lint! {
1366 pub ABSURD_EXTREME_COMPARISONS,
1368 "a comparison with a maximum or minimum value that is always true or false"
1371 pub struct AbsurdExtremeComparisons;
1373 impl LintPass for AbsurdExtremeComparisons {
1374 fn get_lints(&self) -> LintArray {
1375 lint_array!(ABSURD_EXTREME_COMPARISONS)
1384 struct ExtremeExpr<'a> {
1389 enum AbsurdComparisonResult {
1392 InequalityImpossible,
1396 fn is_cast_between_fixed_and_target<'a, 'tcx>(
1397 cx: &LateContext<'a, 'tcx>,
1401 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1402 let precast_ty = cx.tables.expr_ty(cast_exp);
1403 let cast_ty = cx.tables.expr_ty(expr);
1405 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty)
1411 fn detect_absurd_comparison<'a, 'tcx>(
1412 cx: &LateContext<'a, 'tcx>,
1416 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1417 use crate::types::ExtremeType::*;
1418 use crate::types::AbsurdComparisonResult::*;
1419 use crate::utils::comparisons::*;
1421 // absurd comparison only makes sense on primitive types
1422 // primitive types don't implement comparison operators with each other
1423 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1427 // comparisons between fix sized types and target sized types are considered unanalyzable
1428 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1432 let normalized = normalize_comparison(op, lhs, rhs);
1433 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1439 let lx = detect_extreme_expr(cx, normalized_lhs);
1440 let rx = detect_extreme_expr(cx, normalized_rhs);
1445 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1446 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1452 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1453 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1454 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1455 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1459 Rel::Ne | Rel::Eq => return None,
1463 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1464 use crate::types::ExtremeType::*;
1466 let ty = cx.tables.expr_ty(expr);
1468 let cv = constant(cx, cx.tables, expr)?.0;
1470 let which = match (&ty.sty, cv) {
1471 (&ty::Bool, Constant::Bool(false)) |
1472 (&ty::Uint(_), Constant::Int(0)) => Minimum,
1473 (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) => Minimum,
1475 (&ty::Bool, Constant::Bool(true)) => Maximum,
1476 (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) => Maximum,
1477 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1487 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1488 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1489 use crate::types::ExtremeType::*;
1490 use crate::types::AbsurdComparisonResult::*;
1492 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1493 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1494 if !in_macro(expr.span) {
1495 let msg = "this comparison involving the minimum or maximum element for this \
1496 type contains a case that is always true or always false";
1498 let conclusion = match result {
1499 AlwaysFalse => "this comparison is always false".to_owned(),
1500 AlwaysTrue => "this comparison is always true".to_owned(),
1501 InequalityImpossible => format!(
1502 "the case where the two sides are not equal never occurs, consider using {} == {} \
1504 snippet(cx, lhs.span, "lhs"),
1505 snippet(cx, rhs.span, "rhs")
1510 "because {} is the {} value for this type, {}",
1511 snippet(cx, culprit.expr.span, "x"),
1512 match culprit.which {
1513 Minimum => "minimum",
1514 Maximum => "maximum",
1519 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1526 /// **What it does:** Checks for comparisons where the relation is always either
1527 /// true or false, but where one side has been upcast so that the comparison is
1528 /// necessary. Only integer types are checked.
1530 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1531 /// will mistakenly imply that it is possible for `x` to be outside the range of
1534 /// **Known problems:**
1535 /// https://github.com/rust-lang-nursery/rust-clippy/issues/886
1539 /// let x : u8 = ...; (x as u32) > 300
1541 declare_clippy_lint! {
1542 pub INVALID_UPCAST_COMPARISONS,
1544 "a comparison involving an upcast which is always true or false"
1547 pub struct InvalidUpcastComparisons;
1549 impl LintPass for InvalidUpcastComparisons {
1550 fn get_lints(&self) -> LintArray {
1551 lint_array!(INVALID_UPCAST_COMPARISONS)
1555 #[derive(Copy, Clone, Debug, Eq)]
1562 #[allow(clippy::cast_sign_loss)]
1563 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1566 } else if u > (i128::max_value() as u128) {
1574 impl PartialEq for FullInt {
1575 fn eq(&self, other: &Self) -> bool {
1576 self.partial_cmp(other)
1577 .expect("partial_cmp only returns Some(_)") == Ordering::Equal
1581 impl PartialOrd for FullInt {
1582 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1583 Some(match (self, other) {
1584 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1585 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1586 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1587 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1591 impl Ord for FullInt {
1592 fn cmp(&self, other: &Self) -> Ordering {
1593 self.partial_cmp(other)
1594 .expect("partial_cmp for FullInt can never return None")
1599 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1600 use crate::syntax::ast::{IntTy, UintTy};
1603 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1604 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1605 let cast_ty = cx.tables.expr_ty(expr);
1606 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1607 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1610 match pre_cast_ty.sty {
1611 ty::Int(int_ty) => Some(match int_ty {
1612 IntTy::I8 => (FullInt::S(i128::from(i8::min_value())), FullInt::S(i128::from(i8::max_value()))),
1614 FullInt::S(i128::from(i16::min_value())),
1615 FullInt::S(i128::from(i16::max_value())),
1618 FullInt::S(i128::from(i32::min_value())),
1619 FullInt::S(i128::from(i32::max_value())),
1622 FullInt::S(i128::from(i64::min_value())),
1623 FullInt::S(i128::from(i64::max_value())),
1625 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1626 IntTy::Isize => (FullInt::S(isize::min_value() as i128), FullInt::S(isize::max_value() as i128)),
1628 ty::Uint(uint_ty) => Some(match uint_ty {
1629 UintTy::U8 => (FullInt::U(u128::from(u8::min_value())), FullInt::U(u128::from(u8::max_value()))),
1631 FullInt::U(u128::from(u16::min_value())),
1632 FullInt::U(u128::from(u16::max_value())),
1635 FullInt::U(u128::from(u32::min_value())),
1636 FullInt::U(u128::from(u32::max_value())),
1639 FullInt::U(u128::from(u64::min_value())),
1640 FullInt::U(u128::from(u64::max_value())),
1642 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1643 UintTy::Usize => (FullInt::U(usize::min_value() as u128), FullInt::U(usize::max_value() as u128)),
1652 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1653 let val = constant(cx, cx.tables, expr)?.0;
1654 if let Constant::Int(const_int) = val {
1655 match cx.tables.expr_ty(expr).sty {
1656 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1657 ty::Uint(_) => Some(FullInt::U(const_int)),
1665 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1666 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1669 INVALID_UPCAST_COMPARISONS,
1672 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1673 snippet(cx, cast_val.span, "the expression"),
1674 if always { "true" } else { "false" },
1680 fn upcast_comparison_bounds_err<'a, 'tcx>(
1681 cx: &LateContext<'a, 'tcx>,
1683 rel: comparisons::Rel,
1684 lhs_bounds: Option<(FullInt, FullInt)>,
1689 use crate::utils::comparisons::*;
1691 if let Some((lb, ub)) = lhs_bounds {
1692 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1693 if rel == Rel::Eq || rel == Rel::Ne {
1694 if norm_rhs_val < lb || norm_rhs_val > ub {
1695 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1697 } else if match rel {
1698 Rel::Lt => if invert {
1703 Rel::Le => if invert {
1708 Rel::Eq | Rel::Ne => unreachable!(),
1710 err_upcast_comparison(cx, span, lhs, true)
1711 } else if match rel {
1712 Rel::Lt => if invert {
1717 Rel::Le => if invert {
1722 Rel::Eq | Rel::Ne => unreachable!(),
1724 err_upcast_comparison(cx, span, lhs, false)
1730 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1731 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1732 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1733 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1734 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1740 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1741 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1743 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1744 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1749 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1750 /// over different hashers and implicitly defaulting to the default hashing
1751 /// algorithm (SipHash).
1753 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1756 /// **Known problems:** Suggestions for replacing constructors can contain
1757 /// false-positives. Also applying suggestions can require modification of other
1758 /// pieces of code, possibly including external crates.
1762 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1764 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1766 declare_clippy_lint! {
1767 pub IMPLICIT_HASHER,
1769 "missing generalization over different hashers"
1772 pub struct ImplicitHasher;
1774 impl LintPass for ImplicitHasher {
1775 fn get_lints(&self) -> LintArray {
1776 lint_array!(IMPLICIT_HASHER)
1780 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1781 #[allow(clippy::cast_possible_truncation)]
1782 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1783 use crate::syntax_pos::BytePos;
1785 fn suggestion<'a, 'tcx>(
1786 cx: &LateContext<'a, 'tcx>,
1787 db: &mut DiagnosticBuilder<'_>,
1788 generics_span: Span,
1789 generics_suggestion_span: Span,
1790 target: &ImplicitHasherType<'_>,
1791 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1793 let generics_snip = snippet(cx, generics_span, "");
1795 let generics_snip = if generics_snip.is_empty() {
1798 &generics_snip[1..generics_snip.len() - 1]
1803 "consider adding a type parameter".to_string(),
1806 generics_suggestion_span,
1808 "<{}{}S: ::std::hash::BuildHasher{}>",
1810 if generics_snip.is_empty() { "" } else { ", " },
1811 if vis.suggestions.is_empty() {
1814 // request users to add `Default` bound so that generic constructors can be used
1821 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1826 if !vis.suggestions.is_empty() {
1827 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1831 if !cx.access_levels.is_exported(item.id) {
1836 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1837 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1840 for target in &vis.found {
1841 if differing_macro_contexts(item.span, target.span()) {
1845 let generics_suggestion_span = generics.span.substitute_dummy({
1846 let pos = snippet_opt(cx, item.span.until(target.span()))
1847 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
1848 if let Some(pos) = pos {
1849 Span::new(pos, pos, item.span.data().ctxt)
1855 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1856 for item in items.iter().map(|item| cx.tcx.hir.impl_item(item.id)) {
1857 ctr_vis.visit_impl_item(item);
1864 &format!("impl for `{}` should be generalized over different hashers", target.type_name()),
1866 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1871 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
1872 let body = cx.tcx.hir.body(body_id);
1874 for ty in &decl.inputs {
1875 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1878 for target in &vis.found {
1879 let generics_suggestion_span = generics.span.substitute_dummy({
1880 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
1882 let i = snip.find("fn")?;
1883 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
1885 .expect("failed to create span for type parameters");
1886 Span::new(pos, pos, item.span.data().ctxt)
1889 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1890 ctr_vis.visit_body(body);
1897 "parameter of type `{}` should be generalized over different hashers",
1901 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1912 enum ImplicitHasherType<'tcx> {
1913 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
1914 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
1917 impl<'tcx> ImplicitHasherType<'tcx> {
1918 /// Checks that `ty` is a target type without a BuildHasher.
1919 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
1920 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
1921 let params: Vec<_> = path.segments.last().as_ref()?.args.as_ref()?
1922 .args.iter().filter_map(|arg| match arg {
1923 GenericArg::Type(ty) => Some(ty),
1924 GenericArg::Lifetime(_) => None,
1926 let params_len = params.len();
1928 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
1930 if match_path(path, &paths::HASHMAP) && params_len == 2 {
1931 Some(ImplicitHasherType::HashMap(
1934 snippet(cx, params[0].span, "K"),
1935 snippet(cx, params[1].span, "V"),
1937 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
1938 Some(ImplicitHasherType::HashSet(hir_ty.span, ty, snippet(cx, params[0].span, "T")))
1947 fn type_name(&self) -> &'static str {
1949 ImplicitHasherType::HashMap(..) => "HashMap",
1950 ImplicitHasherType::HashSet(..) => "HashSet",
1954 fn type_arguments(&self) -> String {
1956 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
1957 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
1961 fn ty(&self) -> Ty<'tcx> {
1963 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
1967 fn span(&self) -> Span {
1969 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
1974 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
1975 cx: &'a LateContext<'a, 'tcx>,
1976 found: Vec<ImplicitHasherType<'tcx>>,
1979 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
1980 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
1981 Self { cx, found: vec![] }
1985 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
1986 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
1987 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
1988 self.found.push(target);
1994 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1995 NestedVisitorMap::None
1999 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2000 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2001 cx: &'a LateContext<'a, 'tcx>,
2002 body: &'a TypeckTables<'tcx>,
2003 target: &'b ImplicitHasherType<'tcx>,
2004 suggestions: BTreeMap<Span, String>,
2007 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2008 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2013 suggestions: BTreeMap::new(),
2018 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2019 fn visit_body(&mut self, body: &'tcx Body) {
2020 self.body = self.cx.tcx.body_tables(body.id());
2021 walk_body(self, body);
2024 fn visit_expr(&mut self, e: &'tcx Expr) {
2026 if let ExprKind::Call(ref fun, ref args) = e.node;
2027 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2028 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2030 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2034 if match_path(ty_path, &paths::HASHMAP) {
2035 if method.ident.name == "new" {
2037 .insert(e.span, "HashMap::default()".to_string());
2038 } else if method.ident.name == "with_capacity" {
2039 self.suggestions.insert(
2042 "HashMap::with_capacity_and_hasher({}, Default::default())",
2043 snippet(self.cx, args[0].span, "capacity"),
2047 } else if match_path(ty_path, &paths::HASHSET) {
2048 if method.ident.name == "new" {
2050 .insert(e.span, "HashSet::default()".to_string());
2051 } else if method.ident.name == "with_capacity" {
2052 self.suggestions.insert(
2055 "HashSet::with_capacity_and_hasher({}, Default::default())",
2056 snippet(self.cx, args[0].span, "capacity"),
2067 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2068 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)