1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 #![allow(clippy::default_hash_types)]
13 use crate::consts::{constant, Constant};
14 use crate::reexport::*;
15 use crate::rustc::hir;
16 use crate::rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
17 use crate::rustc::hir::*;
18 use crate::rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
19 use crate::rustc::ty::layout::LayoutOf;
20 use crate::rustc::ty::{self, Ty, TyCtxt, TypeckTables};
21 use crate::rustc::{declare_tool_lint, lint_array};
22 use crate::rustc_errors::Applicability;
23 use crate::rustc_target::spec::abi::Abi;
24 use crate::rustc_typeck::hir_ty_to_ty;
25 use crate::syntax::ast::{FloatTy, IntTy, UintTy};
26 use crate::syntax::errors::DiagnosticBuilder;
27 use crate::syntax::source_map::{DUMMY_SP, Span};
28 use crate::utils::paths;
30 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
31 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
32 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
35 use if_chain::if_chain;
37 use std::cmp::Ordering;
38 use std::collections::BTreeMap;
40 /// Handles all the linting of funky types
43 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
45 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
46 /// the heap. So if you `Box` it, you just add another level of indirection
47 /// without any benefit whatsoever.
49 /// **Known problems:** None.
54 /// values: Box<Vec<Foo>>,
65 declare_clippy_lint! {
68 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
71 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
73 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
74 /// the heap. So if you `Box` its contents, you just add another level of indirection.
76 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530, 1st comment).
81 /// values: Vec<Box<i32>>,
92 declare_clippy_lint! {
95 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
98 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
101 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
102 /// represents an optional optional value which is logically the same thing as an optional
103 /// value but has an unneeded extra level of wrapping.
105 /// **Known problems:** None.
109 /// fn x() -> Option<Option<u32>> {
112 declare_clippy_lint! {
115 "usage of `Option<Option<T>>`"
118 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
119 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
121 /// **Why is this bad?** Gankro says:
123 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
124 /// pointers and indirection.
125 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
127 /// > "only" amortized for push/pop, should be faster in the general case for
128 /// almost every possible
129 /// > workload, and isn't even amortized at all if you can predict the capacity
132 /// > `LinkedList`s are only really good if you're doing a lot of merging or
133 /// splitting of lists.
134 /// > This is because they can just mangle some pointers instead of actually
135 /// copying the data. Even
136 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
137 /// can still be better
138 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
140 /// **Known problems:** False positives – the instances where using a
141 /// `LinkedList` makes sense are few and far between, but they can still happen.
145 /// let x = LinkedList::new();
147 declare_clippy_lint! {
150 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
153 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
155 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
158 /// **Known problems:** None.
162 /// fn foo(bar: &Box<T>) { ... }
168 /// fn foo(bar: &T) { ... }
170 declare_clippy_lint! {
173 "a borrow of a boxed type"
176 impl LintPass for TypePass {
177 fn get_lints(&self) -> LintArray {
178 lint_array!(BOX_VEC, VEC_BOX_SIZED, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
182 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
183 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
184 // skip trait implementations, see #605
185 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(id)) {
186 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
191 check_fn_decl(cx, decl);
194 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
195 check_ty(cx, &field.ty, false);
198 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
200 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
201 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
206 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
207 if let Some(ref ty) = local.ty {
208 check_ty(cx, ty, true);
213 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
214 for input in &decl.inputs {
215 check_ty(cx, input, false);
218 if let FunctionRetTy::Return(ref ty) = decl.output {
219 check_ty(cx, ty, false);
223 /// Check if `qpath` has last segment with type parameter matching `path`
224 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
225 let last = last_path_segment(qpath);
227 if let Some(ref params) = last.args;
228 if !params.parenthesized;
229 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
230 GenericArg::Type(ty) => Some(ty),
231 GenericArg::Lifetime(_) => None,
233 if let TyKind::Path(ref qpath) = ty.node;
234 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
235 if match_def_path(cx.tcx, did, path);
243 /// Recursively check for `TypePass` lints in the given type. Stop at the first
246 /// The parameter `is_local` distinguishes the context of the type; types from
247 /// local bindings should only be checked for the `BORROWED_BOX` lint.
248 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
249 if in_macro(ast_ty.span) {
253 TyKind::Path(ref qpath) if !is_local => {
254 let hir_id = cx.tcx.hir().node_to_hir_id(ast_ty.id);
255 let def = cx.tables.qpath_def(qpath, hir_id);
256 if let Some(def_id) = opt_def_id(def) {
257 if Some(def_id) == cx.tcx.lang_items().owned_box() {
258 if match_type_parameter(cx, qpath, &paths::VEC) {
263 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
264 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
266 return; // don't recurse into the type
268 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
270 // Get the _ part of Vec<_>
271 if let Some(ref last) = last_path_segment(qpath).args;
272 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
273 GenericArg::Type(ty) => Some(ty),
274 GenericArg::Lifetime(_) => None,
276 // ty is now _ at this point
277 if let TyKind::Path(ref ty_qpath) = ty.node;
278 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
279 if let Some(def_id) = opt_def_id(def);
280 if Some(def_id) == cx.tcx.lang_items().owned_box();
281 // At this point, we know ty is Box<T>, now get T
282 if let Some(ref last) = last_path_segment(ty_qpath).args;
283 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
284 GenericArg::Type(ty) => Some(ty),
285 GenericArg::Lifetime(_) => None,
287 if let TyKind::Path(ref ty_qpath) = ty.node;
288 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
289 if let Some(def_id) = opt_def_id(def);
290 let boxed_type = cx.tcx.type_of(def_id);
291 if boxed_type.is_sized(cx.tcx.at(DUMMY_SP), cx.param_env);
297 "you seem to be trying to use `Vec<Box<T>>`, but T is Sized. `Vec<T>` is already on the heap, `Vec<Box<T>>` makes an extra allocation.",
299 format!("Vec<{}>", boxed_type),
300 Applicability::MachineApplicable
304 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
305 if match_type_parameter(cx, qpath, &paths::OPTION) {
310 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
311 enum if you need to distinguish all 3 cases",
313 return; // don't recurse into the type
315 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
320 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
321 "a VecDeque might work",
323 return; // don't recurse into the type
327 QPath::Resolved(Some(ref ty), ref p) => {
328 check_ty(cx, ty, is_local);
329 for ty in p.segments.iter().flat_map(|seg| {
332 .map_or_else(|| [].iter(), |params| params.args.iter())
333 .filter_map(|arg| match arg {
334 GenericArg::Type(ty) => Some(ty),
335 GenericArg::Lifetime(_) => None,
338 check_ty(cx, ty, is_local);
341 QPath::Resolved(None, ref p) => {
342 for ty in p.segments.iter().flat_map(|seg| {
345 .map_or_else(|| [].iter(), |params| params.args.iter())
346 .filter_map(|arg| match arg {
347 GenericArg::Type(ty) => Some(ty),
348 GenericArg::Lifetime(_) => None,
351 check_ty(cx, ty, is_local);
354 QPath::TypeRelative(ref ty, ref seg) => {
355 check_ty(cx, ty, is_local);
356 if let Some(ref params) = seg.args {
357 for ty in params.args.iter().filter_map(|arg| match arg {
358 GenericArg::Type(ty) => Some(ty),
359 GenericArg::Lifetime(_) => None,
361 check_ty(cx, ty, is_local);
367 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
369 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
370 check_ty(cx, ty, is_local)
372 TyKind::Tup(ref tys) => {
374 check_ty(cx, ty, is_local);
381 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
382 match mut_ty.ty.node {
383 TyKind::Path(ref qpath) => {
384 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
385 let def = cx.tables.qpath_def(qpath, hir_id);
387 if let Some(def_id) = opt_def_id(def);
388 if Some(def_id) == cx.tcx.lang_items().owned_box();
389 if let QPath::Resolved(None, ref path) = *qpath;
390 if let [ref bx] = *path.segments;
391 if let Some(ref params) = bx.args;
392 if !params.parenthesized;
393 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
394 GenericArg::Type(ty) => Some(ty),
395 GenericArg::Lifetime(_) => None,
398 if is_any_trait(inner) {
399 // Ignore `Box<Any>` types, see #1884 for details.
403 let ltopt = if lt.is_elided() {
406 format!("{} ", lt.name.ident().as_str())
408 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
413 let mut applicability = Applicability::MachineApplicable;
418 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
424 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
426 Applicability::Unspecified,
428 return; // don't recurse into the type
431 check_ty(cx, &mut_ty.ty, is_local);
433 _ => check_ty(cx, &mut_ty.ty, is_local),
437 // Returns true if given type is `Any` trait.
438 fn is_any_trait(t: &hir::Ty) -> bool {
440 if let TyKind::TraitObject(ref traits, _) = t.node;
441 if traits.len() >= 1;
442 // Only Send/Sync can be used as additional traits, so it is enough to
443 // check only the first trait.
444 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
455 /// **What it does:** Checks for binding a unit value.
457 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
458 /// binding one is kind of pointless.
460 /// **Known problems:** None.
468 declare_clippy_lint! {
471 "creating a let binding to a value of unit type, which usually can't be used afterwards"
474 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
475 if let DeclKind::Local(ref local) = decl.node {
476 if is_unit(cx.tables.pat_ty(&local.pat)) {
477 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
480 if higher::is_from_for_desugar(decl) {
488 "this let-binding has unit value. Consider omitting `let {} =`",
489 snippet(cx, local.pat.span, "..")
496 impl LintPass for LetPass {
497 fn get_lints(&self) -> LintArray {
498 lint_array!(LET_UNIT_VALUE)
502 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
503 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
504 check_let_unit(cx, decl)
508 /// **What it does:** Checks for comparisons to unit.
510 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
511 /// clumsily written constant. Mostly this happens when someone accidentally
512 /// adds semicolons at the end of the operands.
514 /// **Known problems:** None.
534 declare_clippy_lint! {
537 "comparing unit values"
542 impl LintPass for UnitCmp {
543 fn get_lints(&self) -> LintArray {
544 lint_array!(UNIT_CMP)
548 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
549 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
550 if in_macro(expr.span) {
553 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
555 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
556 let result = match op {
557 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
565 "{}-comparison of unit values detected. This will always be {}",
575 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
576 /// unit literal (`()`).
578 /// **Why is this bad?** This is likely the result of an accidental semicolon.
580 /// **Known problems:** None.
589 declare_clippy_lint! {
592 "passing unit to a function"
597 impl LintPass for UnitArg {
598 fn get_lints(&self) -> LintArray {
599 lint_array!(UNIT_ARG)
603 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
604 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
605 if in_macro(expr.span) {
609 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
611 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
612 let map = &cx.tcx.hir();
613 // apparently stuff in the desugaring of `?` can trigger this
614 // so check for that here
615 // only the calls to `Try::from_error` is marked as desugared,
616 // so we need to check both the current Expr and its parent.
617 if !is_questionmark_desugar_marked_call(expr) {
619 let opt_parent_node = map.find(map.get_parent_node(expr.id));
620 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
621 if is_questionmark_desugar_marked_call(parent_expr);
624 // `expr` and `parent_expr` where _both_ not from
625 // desugaring `?`, so lint
630 "passing a unit value to a function",
631 "if you intended to pass a unit value, use a unit literal instead",
633 Applicability::MachineApplicable,
646 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
647 use crate::syntax_pos::hygiene::CompilerDesugaringKind;
648 if let ExprKind::Call(ref callee, _) = expr.node {
649 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
655 fn is_unit(ty: Ty<'_>) -> bool {
657 ty::Tuple(slice) if slice.is_empty() => true,
662 fn is_unit_literal(expr: &Expr) -> bool {
664 ExprKind::Tup(ref slice) if slice.is_empty() => true,
671 /// **What it does:** Checks for casts from any numerical to a float type where
672 /// the receiving type cannot store all values from the original type without
673 /// rounding errors. This possible rounding is to be expected, so this lint is
674 /// `Allow` by default.
676 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
677 /// or any 64-bit integer to `f64`.
679 /// **Why is this bad?** It's not bad at all. But in some applications it can be
680 /// helpful to know where precision loss can take place. This lint can help find
681 /// those places in the code.
683 /// **Known problems:** None.
687 /// let x = u64::MAX;
690 declare_clippy_lint! {
691 pub CAST_PRECISION_LOSS,
693 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
696 /// **What it does:** Checks for casts from a signed to an unsigned numerical
697 /// type. In this case, negative values wrap around to large positive values,
698 /// which can be quite surprising in practice. However, as the cast works as
699 /// defined, this lint is `Allow` by default.
701 /// **Why is this bad?** Possibly surprising results. You can activate this lint
702 /// as a one-time check to see where numerical wrapping can arise.
704 /// **Known problems:** None.
709 /// y as u128 // will return 18446744073709551615
711 declare_clippy_lint! {
714 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
717 /// **What it does:** Checks for on casts between numerical types that may
718 /// truncate large values. This is expected behavior, so the cast is `Allow` by
721 /// **Why is this bad?** In some problem domains, it is good practice to avoid
722 /// truncation. This lint can be activated to help assess where additional
723 /// checks could be beneficial.
725 /// **Known problems:** None.
729 /// fn as_u8(x: u64) -> u8 {
733 declare_clippy_lint! {
734 pub CAST_POSSIBLE_TRUNCATION,
736 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
739 /// **What it does:** Checks for casts from an unsigned type to a signed type of
740 /// the same size. Performing such a cast is a 'no-op' for the compiler,
741 /// i.e. nothing is changed at the bit level, and the binary representation of
742 /// the value is reinterpreted. This can cause wrapping if the value is too big
743 /// for the target signed type. However, the cast works as defined, so this lint
744 /// is `Allow` by default.
746 /// **Why is this bad?** While such a cast is not bad in itself, the results can
747 /// be surprising when this is not the intended behavior, as demonstrated by the
750 /// **Known problems:** None.
754 /// u32::MAX as i32 // will yield a value of `-1`
756 declare_clippy_lint! {
757 pub CAST_POSSIBLE_WRAP,
759 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
762 /// **What it does:** Checks for on casts between numerical types that may
763 /// be replaced by safe conversion functions.
765 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
766 /// conversions, including silently lossy conversions. Conversion functions such
767 /// as `i32::from` will only perform lossless conversions. Using the conversion
768 /// functions prevents conversions from turning into silent lossy conversions if
769 /// the types of the input expressions ever change, and make it easier for
770 /// people reading the code to know that the conversion is lossless.
772 /// **Known problems:** None.
776 /// fn as_u64(x: u8) -> u64 {
781 /// Using `::from` would look like this:
784 /// fn as_u64(x: u8) -> u64 {
788 declare_clippy_lint! {
791 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
794 /// **What it does:** Checks for casts to the same type.
796 /// **Why is this bad?** It's just unnecessary.
798 /// **Known problems:** None.
802 /// let _ = 2i32 as i32
804 declare_clippy_lint! {
805 pub UNNECESSARY_CAST,
807 "cast to the same type, e.g. `x as i32` where `x: i32`"
810 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
811 /// more-strictly-aligned pointer
813 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
816 /// **Known problems:** None.
820 /// let _ = (&1u8 as *const u8) as *const u16;
821 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
823 declare_clippy_lint! {
824 pub CAST_PTR_ALIGNMENT,
826 "cast from a pointer to a more-strictly-aligned pointer"
829 /// **What it does:** Checks for casts of function pointers to something other than usize
831 /// **Why is this bad?**
832 /// Casting a function pointer to anything other than usize/isize is not portable across
833 /// architectures, because you end up losing bits if the target type is too small or end up with a
834 /// bunch of extra bits that waste space and add more instructions to the final binary than
835 /// strictly necessary for the problem
837 /// Casting to isize also doesn't make sense since there are no signed addresses.
843 /// fn fun() -> i32 {}
844 /// let a = fun as i64;
847 /// fn fun2() -> i32 {}
848 /// let a = fun2 as usize;
850 declare_clippy_lint! {
851 pub FN_TO_NUMERIC_CAST,
853 "casting a function pointer to a numeric type other than usize"
856 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
859 /// **Why is this bad?**
860 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
861 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
862 /// a comment) to perform the truncation.
868 /// fn fn1() -> i16 {
871 /// let _ = fn1 as i32;
873 /// // Better: Cast to usize first, then comment with the reason for the truncation
874 /// fn fn2() -> i16 {
877 /// let fn_ptr = fn2 as usize;
878 /// let fn_ptr_truncated = fn_ptr as i32;
880 declare_clippy_lint! {
881 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
883 "casting a function pointer to a numeric type not wide enough to store the address"
886 /// Returns the size in bits of an integral type.
887 /// Will return 0 if the type is not an int or uint variant
888 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
890 ty::Int(i) => match i {
891 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
898 ty::Uint(i) => match i {
899 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
910 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
912 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
917 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
918 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
919 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
920 let arch_dependent_str = "on targets with 64-bit wide pointers ";
921 let from_nbits_str = if arch_dependent {
923 } else if is_isize_or_usize(cast_from) {
924 "32 or 64".to_owned()
926 int_ty_to_nbits(cast_from, cx.tcx).to_string()
933 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
934 is only {4} bits wide)",
936 if cast_to_f64 { "f64" } else { "f32" },
937 if arch_dependent { arch_dependent_str } else { "" },
944 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
945 if let ExprKind::Binary(_, _, _) = op.node {
946 if snip.starts_with('(') && snip.ends_with(')') {
953 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
954 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
955 if in_constant(cx, expr.id) {
958 // The suggestion is to use a function call, so if the original expression
959 // has parens on the outside, they are no longer needed.
960 let mut applicability = Applicability::MachineApplicable;
961 let opt = snippet_opt(cx, op.span);
962 let sugg = if let Some(ref snip) = opt {
963 if should_strip_parens(op, snip) {
964 &snip[1..snip.len() - 1]
969 applicability = Applicability::HasPlaceholders;
978 "casting {} to {} may become silently lossy if types change",
982 format!("{}::from({})", cast_to, sugg),
993 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
994 let arch_64_suffix = " on targets with 64-bit wide pointers";
995 let arch_32_suffix = " on targets with 32-bit wide pointers";
996 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
997 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
998 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
999 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1000 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1001 (true, true) | (false, false) => (
1002 to_nbits < from_nbits,
1004 to_nbits == from_nbits && cast_unsigned_to_signed,
1014 to_nbits <= 32 && cast_unsigned_to_signed,
1020 cast_unsigned_to_signed,
1021 if from_nbits == 64 {
1028 if span_truncation {
1031 CAST_POSSIBLE_TRUNCATION,
1034 "casting {} to {} may truncate the value{}",
1037 match suffix_truncation {
1038 ArchSuffix::_32 => arch_32_suffix,
1039 ArchSuffix::_64 => arch_64_suffix,
1040 ArchSuffix::None => "",
1051 "casting {} to {} may wrap around the value{}",
1055 ArchSuffix::_32 => arch_32_suffix,
1056 ArchSuffix::_64 => arch_64_suffix,
1057 ArchSuffix::None => "",
1064 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1065 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1066 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1067 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1068 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1070 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1074 impl LintPass for CastPass {
1075 fn get_lints(&self) -> LintArray {
1077 CAST_PRECISION_LOSS,
1079 CAST_POSSIBLE_TRUNCATION,
1085 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1090 // Check if the given type is either `core::ffi::c_void` or
1091 // one of the platform specific `libc::<platform>::c_void` of libc.
1092 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1093 if let ty::Adt(adt, _) = ty.sty {
1094 let mut apb = AbsolutePathBuffer { names: vec![] };
1095 tcx.push_item_path(&mut apb, adt.did, false);
1097 if apb.names.is_empty() {
1100 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1107 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1108 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1109 if let ExprKind::Cast(ref ex, _) = expr.node {
1110 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1111 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1112 if let ExprKind::Lit(ref lit) = ex.node {
1113 use crate::syntax::ast::{LitIntType, LitKind};
1115 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1117 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1123 "casting to the same type is unnecessary (`{}` -> `{}`)",
1131 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1132 match (cast_from.is_integral(), cast_to.is_integral()) {
1134 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1135 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1140 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1141 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1143 if from_nbits < to_nbits {
1144 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1150 CAST_POSSIBLE_TRUNCATION,
1152 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1154 if !cast_to.is_signed() {
1159 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1164 if cast_from.is_signed() && !cast_to.is_signed() {
1169 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1172 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1173 check_lossless(cx, expr, ex, cast_from, cast_to);
1176 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1179 CAST_POSSIBLE_TRUNCATION,
1181 "casting f64 to f32 may truncate the value",
1184 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1185 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1192 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1193 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1194 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1195 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1196 if from_align < to_align;
1197 // with c_void, we inherently need to trust the user
1198 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1204 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1212 fn lint_fn_to_numeric_cast(
1213 cx: &LateContext<'_, '_>,
1219 // We only want to check casts to `ty::Uint` or `ty::Int`
1221 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1224 match cast_from.sty {
1225 ty::FnDef(..) | ty::FnPtr(_) => {
1226 let mut applicability = Applicability::MachineApplicable;
1227 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1229 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1230 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1233 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1236 "casting function pointer `{}` to `{}`, which truncates the value",
1237 from_snippet, cast_to
1240 format!("{} as usize", from_snippet),
1243 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1248 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1250 format!("{} as usize", from_snippet),
1259 /// **What it does:** Checks for types used in structs, parameters and `let`
1260 /// declarations above a certain complexity threshold.
1262 /// **Why is this bad?** Too complex types make the code less readable. Consider
1263 /// using a `type` definition to simplify them.
1265 /// **Known problems:** None.
1270 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1273 declare_clippy_lint! {
1274 pub TYPE_COMPLEXITY,
1276 "usage of very complex types that might be better factored into `type` definitions"
1279 pub struct TypeComplexityPass {
1283 impl TypeComplexityPass {
1284 pub fn new(threshold: u64) -> Self {
1289 impl LintPass for TypeComplexityPass {
1290 fn get_lints(&self) -> LintArray {
1291 lint_array!(TYPE_COMPLEXITY)
1295 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1298 cx: &LateContext<'a, 'tcx>,
1305 self.check_fndecl(cx, decl);
1308 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1309 // enum variants are also struct fields now
1310 self.check_type(cx, &field.ty);
1313 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1315 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1316 // functions, enums, structs, impls and traits are covered
1321 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1323 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1324 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1325 // methods with default impl are covered by check_fn
1330 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1332 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1333 // methods are covered by check_fn
1338 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1339 if let Some(ref ty) = local.ty {
1340 self.check_type(cx, ty);
1345 impl<'a, 'tcx> TypeComplexityPass {
1346 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1347 for arg in &decl.inputs {
1348 self.check_type(cx, arg);
1350 if let Return(ref ty) = decl.output {
1351 self.check_type(cx, ty);
1355 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1356 if in_macro(ty.span) {
1360 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1361 visitor.visit_ty(ty);
1365 if score > self.threshold {
1370 "very complex type used. Consider factoring parts into `type` definitions",
1376 /// Walks a type and assigns a complexity score to it.
1377 struct TypeComplexityVisitor {
1378 /// total complexity score of the type
1380 /// current nesting level
1384 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1385 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1386 let (add_score, sub_nest) = match ty.node {
1387 // _, &x and *x have only small overhead; don't mess with nesting level
1388 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1390 // the "normal" components of a type: named types, arrays/tuples
1391 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1393 // function types bring a lot of overhead
1394 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1396 TyKind::TraitObject(ref param_bounds, _) => {
1397 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1398 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1399 GenericParamKind::Lifetime { .. } => true,
1403 if has_lifetime_parameters {
1404 // complex trait bounds like A<'a, 'b>
1407 // simple trait bounds like A + B
1414 self.score += add_score;
1415 self.nest += sub_nest;
1417 self.nest -= sub_nest;
1419 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1420 NestedVisitorMap::None
1424 /// **What it does:** Checks for expressions where a character literal is cast
1425 /// to `u8` and suggests using a byte literal instead.
1427 /// **Why is this bad?** In general, casting values to smaller types is
1428 /// error-prone and should be avoided where possible. In the particular case of
1429 /// converting a character literal to u8, it is easy to avoid by just using a
1430 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1431 /// than `'a' as u8`.
1433 /// **Known problems:** None.
1440 /// A better version, using the byte literal:
1445 declare_clippy_lint! {
1448 "casting a character literal to u8"
1451 pub struct CharLitAsU8;
1453 impl LintPass for CharLitAsU8 {
1454 fn get_lints(&self) -> LintArray {
1455 lint_array!(CHAR_LIT_AS_U8)
1459 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1460 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1461 use crate::syntax::ast::{LitKind, UintTy};
1463 if let ExprKind::Cast(ref e, _) = expr.node {
1464 if let ExprKind::Lit(ref l) = e.node {
1465 if let LitKind::Char(_) = l.node {
1466 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1467 let msg = "casting character literal to u8. `char`s \
1468 are 4 bytes wide in rust, so casting to u8 \
1471 "Consider using a byte literal instead:\nb{}",
1472 snippet(cx, e.span, "'x'")
1474 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1482 /// **What it does:** Checks for comparisons where one side of the relation is
1483 /// either the minimum or maximum value for its type and warns if it involves a
1484 /// case that is always true or always false. Only integer and boolean types are
1487 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1488 /// that is is possible for `x` to be less than the minimum. Expressions like
1489 /// `max < x` are probably mistakes.
1491 /// **Known problems:** For `usize` the size of the current compile target will
1492 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1493 /// a comparison to detect target pointer width will trigger this lint. One can
1494 /// use `mem::sizeof` and compare its value or conditional compilation
1496 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1501 /// 100 > std::i32::MAX
1503 declare_clippy_lint! {
1504 pub ABSURD_EXTREME_COMPARISONS,
1506 "a comparison with a maximum or minimum value that is always true or false"
1509 pub struct AbsurdExtremeComparisons;
1511 impl LintPass for AbsurdExtremeComparisons {
1512 fn get_lints(&self) -> LintArray {
1513 lint_array!(ABSURD_EXTREME_COMPARISONS)
1522 struct ExtremeExpr<'a> {
1527 enum AbsurdComparisonResult {
1530 InequalityImpossible,
1533 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1534 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1535 let precast_ty = cx.tables.expr_ty(cast_exp);
1536 let cast_ty = cx.tables.expr_ty(expr);
1538 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1544 fn detect_absurd_comparison<'a, 'tcx>(
1545 cx: &LateContext<'a, 'tcx>,
1549 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1550 use crate::types::AbsurdComparisonResult::*;
1551 use crate::types::ExtremeType::*;
1552 use crate::utils::comparisons::*;
1554 // absurd comparison only makes sense on primitive types
1555 // primitive types don't implement comparison operators with each other
1556 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1560 // comparisons between fix sized types and target sized types are considered unanalyzable
1561 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1565 let normalized = normalize_comparison(op, lhs, rhs);
1566 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1572 let lx = detect_extreme_expr(cx, normalized_lhs);
1573 let rx = detect_extreme_expr(cx, normalized_rhs);
1578 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1579 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1585 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1586 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1587 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1588 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1592 Rel::Ne | Rel::Eq => return None,
1596 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1597 use crate::types::ExtremeType::*;
1599 let ty = cx.tables.expr_ty(expr);
1601 let cv = constant(cx, cx.tables, expr)?.0;
1603 let which = match (&ty.sty, cv) {
1604 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1605 (&ty::Int(ity), Constant::Int(i))
1606 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1611 (&ty::Bool, Constant::Bool(true)) => Maximum,
1612 (&ty::Int(ity), Constant::Int(i))
1613 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1617 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1621 Some(ExtremeExpr { which, expr })
1624 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1625 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1626 use crate::types::AbsurdComparisonResult::*;
1627 use crate::types::ExtremeType::*;
1629 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1630 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1631 if !in_macro(expr.span) {
1632 let msg = "this comparison involving the minimum or maximum element for this \
1633 type contains a case that is always true or always false";
1635 let conclusion = match result {
1636 AlwaysFalse => "this comparison is always false".to_owned(),
1637 AlwaysTrue => "this comparison is always true".to_owned(),
1638 InequalityImpossible => format!(
1639 "the case where the two sides are not equal never occurs, consider using {} == {} \
1641 snippet(cx, lhs.span, "lhs"),
1642 snippet(cx, rhs.span, "rhs")
1647 "because {} is the {} value for this type, {}",
1648 snippet(cx, culprit.expr.span, "x"),
1649 match culprit.which {
1650 Minimum => "minimum",
1651 Maximum => "maximum",
1656 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1663 /// **What it does:** Checks for comparisons where the relation is always either
1664 /// true or false, but where one side has been upcast so that the comparison is
1665 /// necessary. Only integer types are checked.
1667 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1668 /// will mistakenly imply that it is possible for `x` to be outside the range of
1671 /// **Known problems:**
1672 /// https://github.com/rust-lang/rust-clippy/issues/886
1676 /// let x : u8 = ...; (x as u32) > 300
1678 declare_clippy_lint! {
1679 pub INVALID_UPCAST_COMPARISONS,
1681 "a comparison involving an upcast which is always true or false"
1684 pub struct InvalidUpcastComparisons;
1686 impl LintPass for InvalidUpcastComparisons {
1687 fn get_lints(&self) -> LintArray {
1688 lint_array!(INVALID_UPCAST_COMPARISONS)
1692 #[derive(Copy, Clone, Debug, Eq)]
1699 #[allow(clippy::cast_sign_loss)]
1700 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1703 } else if u > (i128::max_value() as u128) {
1711 impl PartialEq for FullInt {
1712 fn eq(&self, other: &Self) -> bool {
1713 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1717 impl PartialOrd for FullInt {
1718 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1719 Some(match (self, other) {
1720 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1721 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1722 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1723 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1727 impl Ord for FullInt {
1728 fn cmp(&self, other: &Self) -> Ordering {
1729 self.partial_cmp(other)
1730 .expect("partial_cmp for FullInt can never return None")
1734 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1735 use crate::syntax::ast::{IntTy, UintTy};
1738 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1739 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1740 let cast_ty = cx.tables.expr_ty(expr);
1741 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1742 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1745 match pre_cast_ty.sty {
1746 ty::Int(int_ty) => Some(match int_ty {
1748 FullInt::S(i128::from(i8::min_value())),
1749 FullInt::S(i128::from(i8::max_value())),
1752 FullInt::S(i128::from(i16::min_value())),
1753 FullInt::S(i128::from(i16::max_value())),
1756 FullInt::S(i128::from(i32::min_value())),
1757 FullInt::S(i128::from(i32::max_value())),
1760 FullInt::S(i128::from(i64::min_value())),
1761 FullInt::S(i128::from(i64::max_value())),
1763 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1765 FullInt::S(isize::min_value() as i128),
1766 FullInt::S(isize::max_value() as i128),
1769 ty::Uint(uint_ty) => Some(match uint_ty {
1771 FullInt::U(u128::from(u8::min_value())),
1772 FullInt::U(u128::from(u8::max_value())),
1775 FullInt::U(u128::from(u16::min_value())),
1776 FullInt::U(u128::from(u16::max_value())),
1779 FullInt::U(u128::from(u32::min_value())),
1780 FullInt::U(u128::from(u32::max_value())),
1783 FullInt::U(u128::from(u64::min_value())),
1784 FullInt::U(u128::from(u64::max_value())),
1786 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1788 FullInt::U(usize::min_value() as u128),
1789 FullInt::U(usize::max_value() as u128),
1799 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1800 let val = constant(cx, cx.tables, expr)?.0;
1801 if let Constant::Int(const_int) = val {
1802 match cx.tables.expr_ty(expr).sty {
1803 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1804 ty::Uint(_) => Some(FullInt::U(const_int)),
1812 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1813 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1816 INVALID_UPCAST_COMPARISONS,
1819 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1820 snippet(cx, cast_val.span, "the expression"),
1821 if always { "true" } else { "false" },
1827 fn upcast_comparison_bounds_err<'a, 'tcx>(
1828 cx: &LateContext<'a, 'tcx>,
1830 rel: comparisons::Rel,
1831 lhs_bounds: Option<(FullInt, FullInt)>,
1836 use crate::utils::comparisons::*;
1838 if let Some((lb, ub)) = lhs_bounds {
1839 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1840 if rel == Rel::Eq || rel == Rel::Ne {
1841 if norm_rhs_val < lb || norm_rhs_val > ub {
1842 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1844 } else if match rel {
1859 Rel::Eq | Rel::Ne => unreachable!(),
1861 err_upcast_comparison(cx, span, lhs, true)
1862 } else if match rel {
1877 Rel::Eq | Rel::Ne => unreachable!(),
1879 err_upcast_comparison(cx, span, lhs, false)
1885 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1886 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1887 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1888 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1889 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1895 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1896 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1898 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1899 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1904 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1905 /// over different hashers and implicitly defaulting to the default hashing
1906 /// algorithm (SipHash).
1908 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1911 /// **Known problems:** Suggestions for replacing constructors can contain
1912 /// false-positives. Also applying suggestions can require modification of other
1913 /// pieces of code, possibly including external crates.
1917 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1919 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1921 declare_clippy_lint! {
1922 pub IMPLICIT_HASHER,
1924 "missing generalization over different hashers"
1927 pub struct ImplicitHasher;
1929 impl LintPass for ImplicitHasher {
1930 fn get_lints(&self) -> LintArray {
1931 lint_array!(IMPLICIT_HASHER)
1935 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1936 #[allow(clippy::cast_possible_truncation)]
1937 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1938 use crate::syntax_pos::BytePos;
1940 fn suggestion<'a, 'tcx>(
1941 cx: &LateContext<'a, 'tcx>,
1942 db: &mut DiagnosticBuilder<'_>,
1943 generics_span: Span,
1944 generics_suggestion_span: Span,
1945 target: &ImplicitHasherType<'_>,
1946 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1948 let generics_snip = snippet(cx, generics_span, "");
1950 let generics_snip = if generics_snip.is_empty() {
1953 &generics_snip[1..generics_snip.len() - 1]
1958 "consider adding a type parameter".to_string(),
1961 generics_suggestion_span,
1963 "<{}{}S: ::std::hash::BuildHasher{}>",
1965 if generics_snip.is_empty() { "" } else { ", " },
1966 if vis.suggestions.is_empty() {
1969 // request users to add `Default` bound so that generic constructors can be used
1976 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1981 if !vis.suggestions.is_empty() {
1982 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1986 if !cx.access_levels.is_exported(item.id) {
1991 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1992 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1995 for target in &vis.found {
1996 if differing_macro_contexts(item.span, target.span()) {
2000 let generics_suggestion_span = generics.span.substitute_dummy({
2001 let pos = snippet_opt(cx, item.span.until(target.span()))
2002 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2003 if let Some(pos) = pos {
2004 Span::new(pos, pos, item.span.data().ctxt)
2010 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2011 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2012 ctr_vis.visit_impl_item(item);
2020 "impl for `{}` should be generalized over different hashers",
2024 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2029 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2030 let body = cx.tcx.hir().body(body_id);
2032 for ty in &decl.inputs {
2033 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2036 for target in &vis.found {
2037 let generics_suggestion_span = generics.span.substitute_dummy({
2038 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2040 let i = snip.find("fn")?;
2041 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2043 .expect("failed to create span for type parameters");
2044 Span::new(pos, pos, item.span.data().ctxt)
2047 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2048 ctr_vis.visit_body(body);
2055 "parameter of type `{}` should be generalized over different hashers",
2059 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2070 enum ImplicitHasherType<'tcx> {
2071 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2072 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2075 impl<'tcx> ImplicitHasherType<'tcx> {
2076 /// Checks that `ty` is a target type without a BuildHasher.
2077 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2078 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2079 let params: Vec<_> = path
2087 .filter_map(|arg| match arg {
2088 GenericArg::Type(ty) => Some(ty),
2089 GenericArg::Lifetime(_) => None,
2092 let params_len = params.len();
2094 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2096 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2097 Some(ImplicitHasherType::HashMap(
2100 snippet(cx, params[0].span, "K"),
2101 snippet(cx, params[1].span, "V"),
2103 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2104 Some(ImplicitHasherType::HashSet(
2107 snippet(cx, params[0].span, "T"),
2117 fn type_name(&self) -> &'static str {
2119 ImplicitHasherType::HashMap(..) => "HashMap",
2120 ImplicitHasherType::HashSet(..) => "HashSet",
2124 fn type_arguments(&self) -> String {
2126 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2127 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2131 fn ty(&self) -> Ty<'tcx> {
2133 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2137 fn span(&self) -> Span {
2139 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2144 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2145 cx: &'a LateContext<'a, 'tcx>,
2146 found: Vec<ImplicitHasherType<'tcx>>,
2149 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2150 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2151 Self { cx, found: vec![] }
2155 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2156 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2157 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2158 self.found.push(target);
2164 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2165 NestedVisitorMap::None
2169 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2170 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2171 cx: &'a LateContext<'a, 'tcx>,
2172 body: &'a TypeckTables<'tcx>,
2173 target: &'b ImplicitHasherType<'tcx>,
2174 suggestions: BTreeMap<Span, String>,
2177 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2178 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2183 suggestions: BTreeMap::new(),
2188 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2189 fn visit_body(&mut self, body: &'tcx Body) {
2190 self.body = self.cx.tcx.body_tables(body.id());
2191 walk_body(self, body);
2194 fn visit_expr(&mut self, e: &'tcx Expr) {
2196 if let ExprKind::Call(ref fun, ref args) = e.node;
2197 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2198 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2200 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2204 if match_path(ty_path, &paths::HASHMAP) {
2205 if method.ident.name == "new" {
2207 .insert(e.span, "HashMap::default()".to_string());
2208 } else if method.ident.name == "with_capacity" {
2209 self.suggestions.insert(
2212 "HashMap::with_capacity_and_hasher({}, Default::default())",
2213 snippet(self.cx, args[0].span, "capacity"),
2217 } else if match_path(ty_path, &paths::HASHSET) {
2218 if method.ident.name == "new" {
2220 .insert(e.span, "HashSet::default()".to_string());
2221 } else if method.ident.name == "with_capacity" {
2222 self.suggestions.insert(
2225 "HashSet::with_capacity_and_hasher({}, Default::default())",
2226 snippet(self.cx, args[0].span, "capacity"),
2237 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2238 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())