1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 #![allow(clippy::default_hash_types)]
13 use crate::consts::{constant, Constant};
14 use crate::reexport::*;
15 use crate::rustc::hir;
16 use crate::rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
17 use crate::rustc::hir::*;
18 use crate::rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
19 use crate::rustc::ty::layout::LayoutOf;
20 use crate::rustc::ty::{self, Ty, TyCtxt, TypeckTables};
21 use crate::rustc::{declare_tool_lint, lint_array};
22 use crate::rustc_errors::Applicability;
23 use crate::rustc_target::spec::abi::Abi;
24 use crate::rustc_typeck::hir_ty_to_ty;
25 use crate::syntax::ast::{FloatTy, IntTy, UintTy};
26 use crate::syntax::errors::DiagnosticBuilder;
27 use crate::syntax::source_map::Span;
28 use crate::utils::paths;
30 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
31 match_def_path, match_path, 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 `Option<Option<_>>` in function signatures and type
74 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
75 /// represents an optional optional value which is logically the same thing as an optional
76 /// value but has an unneeded extra level of wrapping.
78 /// **Known problems:** None.
82 /// fn x() -> Option<Option<u32>> {
85 declare_clippy_lint! {
88 "usage of `Option<Option<T>>`"
91 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
92 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
94 /// **Why is this bad?** Gankro says:
96 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
97 /// pointers and indirection.
98 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
100 /// > "only" amortized for push/pop, should be faster in the general case for
101 /// almost every possible
102 /// > workload, and isn't even amortized at all if you can predict the capacity
105 /// > `LinkedList`s are only really good if you're doing a lot of merging or
106 /// splitting of lists.
107 /// > This is because they can just mangle some pointers instead of actually
108 /// copying the data. Even
109 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
110 /// can still be better
111 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
113 /// **Known problems:** False positives – the instances where using a
114 /// `LinkedList` makes sense are few and far between, but they can still happen.
118 /// let x = LinkedList::new();
120 declare_clippy_lint! {
123 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
126 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
128 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
131 /// **Known problems:** None.
135 /// fn foo(bar: &Box<T>) { ... }
141 /// fn foo(bar: &T) { ... }
143 declare_clippy_lint! {
146 "a borrow of a boxed type"
149 impl LintPass for TypePass {
150 fn get_lints(&self) -> LintArray {
151 lint_array!(BOX_VEC, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
155 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
156 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
157 // skip trait implementations, see #605
158 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(id)) {
159 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
164 check_fn_decl(cx, decl);
167 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
168 check_ty(cx, &field.ty, false);
171 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
173 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
174 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
179 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
180 if let Some(ref ty) = local.ty {
181 check_ty(cx, ty, true);
186 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
187 for input in &decl.inputs {
188 check_ty(cx, input, false);
191 if let FunctionRetTy::Return(ref ty) = decl.output {
192 check_ty(cx, ty, false);
196 /// Check if `qpath` has last segment with type parameter matching `path`
197 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
198 let last = last_path_segment(qpath);
200 if let Some(ref params) = last.args;
201 if !params.parenthesized;
202 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
203 GenericArg::Type(ty) => Some(ty),
204 GenericArg::Lifetime(_) => None,
206 if let TyKind::Path(ref qpath) = ty.node;
207 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
208 if match_def_path(cx.tcx, did, path);
216 /// Recursively check for `TypePass` lints in the given type. Stop at the first
219 /// The parameter `is_local` distinguishes the context of the type; types from
220 /// local bindings should only be checked for the `BORROWED_BOX` lint.
221 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
222 if in_macro(ast_ty.span) {
226 TyKind::Path(ref qpath) if !is_local => {
227 let hir_id = cx.tcx.hir().node_to_hir_id(ast_ty.id);
228 let def = cx.tables.qpath_def(qpath, hir_id);
229 if let Some(def_id) = opt_def_id(def) {
230 if Some(def_id) == cx.tcx.lang_items().owned_box() {
231 if match_type_parameter(cx, qpath, &paths::VEC) {
236 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
237 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
239 return; // don't recurse into the type
241 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
242 if match_type_parameter(cx, qpath, &paths::OPTION) {
247 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
248 enum if you need to distinguish all 3 cases",
250 return; // don't recurse into the type
252 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
257 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
258 "a VecDeque might work",
260 return; // don't recurse into the type
264 QPath::Resolved(Some(ref ty), ref p) => {
265 check_ty(cx, ty, is_local);
266 for ty in p.segments.iter().flat_map(|seg| {
269 .map_or_else(|| [].iter(), |params| params.args.iter())
270 .filter_map(|arg| match arg {
271 GenericArg::Type(ty) => Some(ty),
272 GenericArg::Lifetime(_) => None,
275 check_ty(cx, ty, is_local);
278 QPath::Resolved(None, ref p) => {
279 for ty in p.segments.iter().flat_map(|seg| {
282 .map_or_else(|| [].iter(), |params| params.args.iter())
283 .filter_map(|arg| match arg {
284 GenericArg::Type(ty) => Some(ty),
285 GenericArg::Lifetime(_) => None,
288 check_ty(cx, ty, is_local);
291 QPath::TypeRelative(ref ty, ref seg) => {
292 check_ty(cx, ty, is_local);
293 if let Some(ref params) = seg.args {
294 for ty in params.args.iter().filter_map(|arg| match arg {
295 GenericArg::Type(ty) => Some(ty),
296 GenericArg::Lifetime(_) => None,
298 check_ty(cx, ty, is_local);
304 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
306 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
307 check_ty(cx, ty, is_local)
309 TyKind::Tup(ref tys) => {
311 check_ty(cx, ty, is_local);
318 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
319 match mut_ty.ty.node {
320 TyKind::Path(ref qpath) => {
321 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
322 let def = cx.tables.qpath_def(qpath, hir_id);
324 if let Some(def_id) = opt_def_id(def);
325 if Some(def_id) == cx.tcx.lang_items().owned_box();
326 if let QPath::Resolved(None, ref path) = *qpath;
327 if let [ref bx] = *path.segments;
328 if let Some(ref params) = bx.args;
329 if !params.parenthesized;
330 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
331 GenericArg::Type(ty) => Some(ty),
332 GenericArg::Lifetime(_) => None,
335 if is_any_trait(inner) {
336 // Ignore `Box<Any>` types, see #1884 for details.
340 let ltopt = if lt.is_elided() {
343 format!("{} ", lt.name.ident().as_str())
345 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
350 let mut applicability = Applicability::MachineApplicable;
355 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
361 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
363 Applicability::Unspecified,
365 return; // don't recurse into the type
368 check_ty(cx, &mut_ty.ty, is_local);
370 _ => check_ty(cx, &mut_ty.ty, is_local),
374 // Returns true if given type is `Any` trait.
375 fn is_any_trait(t: &hir::Ty) -> bool {
377 if let TyKind::TraitObject(ref traits, _) = t.node;
378 if traits.len() >= 1;
379 // Only Send/Sync can be used as additional traits, so it is enough to
380 // check only the first trait.
381 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
392 /// **What it does:** Checks for binding a unit value.
394 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
395 /// binding one is kind of pointless.
397 /// **Known problems:** None.
405 declare_clippy_lint! {
408 "creating a let binding to a value of unit type, which usually can't be used afterwards"
411 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
412 if let DeclKind::Local(ref local) = decl.node {
413 if is_unit(cx.tables.pat_ty(&local.pat)) {
414 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
417 if higher::is_from_for_desugar(decl) {
425 "this let-binding has unit value. Consider omitting `let {} =`",
426 snippet(cx, local.pat.span, "..")
433 impl LintPass for LetPass {
434 fn get_lints(&self) -> LintArray {
435 lint_array!(LET_UNIT_VALUE)
439 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
440 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
441 check_let_unit(cx, decl)
445 /// **What it does:** Checks for comparisons to unit.
447 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
448 /// clumsily written constant. Mostly this happens when someone accidentally
449 /// adds semicolons at the end of the operands.
451 /// **Known problems:** None.
471 declare_clippy_lint! {
474 "comparing unit values"
479 impl LintPass for UnitCmp {
480 fn get_lints(&self) -> LintArray {
481 lint_array!(UNIT_CMP)
485 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
486 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
487 if in_macro(expr.span) {
490 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
492 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
493 let result = match op {
494 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
502 "{}-comparison of unit values detected. This will always be {}",
512 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
513 /// unit literal (`()`).
515 /// **Why is this bad?** This is likely the result of an accidental semicolon.
517 /// **Known problems:** None.
526 declare_clippy_lint! {
529 "passing unit to a function"
534 impl LintPass for UnitArg {
535 fn get_lints(&self) -> LintArray {
536 lint_array!(UNIT_ARG)
540 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
541 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
542 if in_macro(expr.span) {
546 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
548 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
549 let map = &cx.tcx.hir();
550 // apparently stuff in the desugaring of `?` can trigger this
551 // so check for that here
552 // only the calls to `Try::from_error` is marked as desugared,
553 // so we need to check both the current Expr and its parent.
554 if !is_questionmark_desugar_marked_call(expr) {
556 let opt_parent_node = map.find(map.get_parent_node(expr.id));
557 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
558 if is_questionmark_desugar_marked_call(parent_expr);
561 // `expr` and `parent_expr` where _both_ not from
562 // desugaring `?`, so lint
567 "passing a unit value to a function",
568 "if you intended to pass a unit value, use a unit literal instead",
570 Applicability::MachineApplicable,
583 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
584 use crate::syntax_pos::hygiene::CompilerDesugaringKind;
585 if let ExprKind::Call(ref callee, _) = expr.node {
586 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
592 fn is_unit(ty: Ty<'_>) -> bool {
594 ty::Tuple(slice) if slice.is_empty() => true,
599 fn is_unit_literal(expr: &Expr) -> bool {
601 ExprKind::Tup(ref slice) if slice.is_empty() => true,
608 /// **What it does:** Checks for casts from any numerical to a float type where
609 /// the receiving type cannot store all values from the original type without
610 /// rounding errors. This possible rounding is to be expected, so this lint is
611 /// `Allow` by default.
613 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
614 /// or any 64-bit integer to `f64`.
616 /// **Why is this bad?** It's not bad at all. But in some applications it can be
617 /// helpful to know where precision loss can take place. This lint can help find
618 /// those places in the code.
620 /// **Known problems:** None.
624 /// let x = u64::MAX;
627 declare_clippy_lint! {
628 pub CAST_PRECISION_LOSS,
630 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
633 /// **What it does:** Checks for casts from a signed to an unsigned numerical
634 /// type. In this case, negative values wrap around to large positive values,
635 /// which can be quite surprising in practice. However, as the cast works as
636 /// defined, this lint is `Allow` by default.
638 /// **Why is this bad?** Possibly surprising results. You can activate this lint
639 /// as a one-time check to see where numerical wrapping can arise.
641 /// **Known problems:** None.
646 /// y as u128 // will return 18446744073709551615
648 declare_clippy_lint! {
651 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
654 /// **What it does:** Checks for on casts between numerical types that may
655 /// truncate large values. This is expected behavior, so the cast is `Allow` by
658 /// **Why is this bad?** In some problem domains, it is good practice to avoid
659 /// truncation. This lint can be activated to help assess where additional
660 /// checks could be beneficial.
662 /// **Known problems:** None.
666 /// fn as_u8(x: u64) -> u8 {
670 declare_clippy_lint! {
671 pub CAST_POSSIBLE_TRUNCATION,
673 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
676 /// **What it does:** Checks for casts from an unsigned type to a signed type of
677 /// the same size. Performing such a cast is a 'no-op' for the compiler,
678 /// i.e. nothing is changed at the bit level, and the binary representation of
679 /// the value is reinterpreted. This can cause wrapping if the value is too big
680 /// for the target signed type. However, the cast works as defined, so this lint
681 /// is `Allow` by default.
683 /// **Why is this bad?** While such a cast is not bad in itself, the results can
684 /// be surprising when this is not the intended behavior, as demonstrated by the
687 /// **Known problems:** None.
691 /// u32::MAX as i32 // will yield a value of `-1`
693 declare_clippy_lint! {
694 pub CAST_POSSIBLE_WRAP,
696 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
699 /// **What it does:** Checks for on casts between numerical types that may
700 /// be replaced by safe conversion functions.
702 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
703 /// conversions, including silently lossy conversions. Conversion functions such
704 /// as `i32::from` will only perform lossless conversions. Using the conversion
705 /// functions prevents conversions from turning into silent lossy conversions if
706 /// the types of the input expressions ever change, and make it easier for
707 /// people reading the code to know that the conversion is lossless.
709 /// **Known problems:** None.
713 /// fn as_u64(x: u8) -> u64 {
718 /// Using `::from` would look like this:
721 /// fn as_u64(x: u8) -> u64 {
725 declare_clippy_lint! {
728 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
731 /// **What it does:** Checks for casts to the same type.
733 /// **Why is this bad?** It's just unnecessary.
735 /// **Known problems:** None.
739 /// let _ = 2i32 as i32
741 declare_clippy_lint! {
742 pub UNNECESSARY_CAST,
744 "cast to the same type, e.g. `x as i32` where `x: i32`"
747 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
748 /// more-strictly-aligned pointer
750 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
753 /// **Known problems:** None.
757 /// let _ = (&1u8 as *const u8) as *const u16;
758 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
760 declare_clippy_lint! {
761 pub CAST_PTR_ALIGNMENT,
763 "cast from a pointer to a more-strictly-aligned pointer"
766 /// **What it does:** Checks for casts of function pointers to something other than usize
768 /// **Why is this bad?**
769 /// Casting a function pointer to anything other than usize/isize is not portable across
770 /// architectures, because you end up losing bits if the target type is too small or end up with a
771 /// bunch of extra bits that waste space and add more instructions to the final binary than
772 /// strictly necessary for the problem
774 /// Casting to isize also doesn't make sense since there are no signed addresses.
780 /// fn fun() -> i32 {}
781 /// let a = fun as i64;
784 /// fn fun2() -> i32 {}
785 /// let a = fun2 as usize;
787 declare_clippy_lint! {
788 pub FN_TO_NUMERIC_CAST,
790 "casting a function pointer to a numeric type other than usize"
793 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
796 /// **Why is this bad?**
797 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
798 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
799 /// a comment) to perform the truncation.
805 /// fn fn1() -> i16 {
808 /// let _ = fn1 as i32;
810 /// // Better: Cast to usize first, then comment with the reason for the truncation
811 /// fn fn2() -> i16 {
814 /// let fn_ptr = fn2 as usize;
815 /// let fn_ptr_truncated = fn_ptr as i32;
817 declare_clippy_lint! {
818 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
820 "casting a function pointer to a numeric type not wide enough to store the address"
823 /// Returns the size in bits of an integral type.
824 /// Will return 0 if the type is not an int or uint variant
825 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
827 ty::Int(i) => match i {
828 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
835 ty::Uint(i) => match i {
836 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
847 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
849 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
854 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
855 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
856 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
857 let arch_dependent_str = "on targets with 64-bit wide pointers ";
858 let from_nbits_str = if arch_dependent {
860 } else if is_isize_or_usize(cast_from) {
861 "32 or 64".to_owned()
863 int_ty_to_nbits(cast_from, cx.tcx).to_string()
870 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
871 is only {4} bits wide)",
873 if cast_to_f64 { "f64" } else { "f32" },
874 if arch_dependent { arch_dependent_str } else { "" },
881 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
882 if let ExprKind::Binary(_, _, _) = op.node {
883 if snip.starts_with('(') && snip.ends_with(')') {
890 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
891 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
892 if in_constant(cx, expr.id) {
895 // The suggestion is to use a function call, so if the original expression
896 // has parens on the outside, they are no longer needed.
897 let mut applicability = Applicability::MachineApplicable;
898 let opt = snippet_opt(cx, op.span);
899 let sugg = if let Some(ref snip) = opt {
900 if should_strip_parens(op, snip) {
901 &snip[1..snip.len() - 1]
906 applicability = Applicability::HasPlaceholders;
915 "casting {} to {} may become silently lossy if types change",
919 format!("{}::from({})", cast_to, sugg),
930 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
931 let arch_64_suffix = " on targets with 64-bit wide pointers";
932 let arch_32_suffix = " on targets with 32-bit wide pointers";
933 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
934 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
935 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
936 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
937 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
938 (true, true) | (false, false) => (
939 to_nbits < from_nbits,
941 to_nbits == from_nbits && cast_unsigned_to_signed,
951 to_nbits <= 32 && cast_unsigned_to_signed,
957 cast_unsigned_to_signed,
958 if from_nbits == 64 {
968 CAST_POSSIBLE_TRUNCATION,
971 "casting {} to {} may truncate the value{}",
974 match suffix_truncation {
975 ArchSuffix::_32 => arch_32_suffix,
976 ArchSuffix::_64 => arch_64_suffix,
977 ArchSuffix::None => "",
988 "casting {} to {} may wrap around the value{}",
992 ArchSuffix::_32 => arch_32_suffix,
993 ArchSuffix::_64 => arch_64_suffix,
994 ArchSuffix::None => "",
1001 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1002 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1003 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1004 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1005 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1007 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1011 impl LintPass for CastPass {
1012 fn get_lints(&self) -> LintArray {
1014 CAST_PRECISION_LOSS,
1016 CAST_POSSIBLE_TRUNCATION,
1022 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1027 // Check if the given type is either `core::ffi::c_void` or
1028 // one of the platform specific `libc::<platform>::c_void` of libc.
1029 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1030 if let ty::Adt(adt, _) = ty.sty {
1031 let mut apb = AbsolutePathBuffer { names: vec![] };
1032 tcx.push_item_path(&mut apb, adt.did, false);
1034 if apb.names.is_empty() { return false }
1035 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1042 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1043 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1044 if let ExprKind::Cast(ref ex, _) = expr.node {
1045 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1046 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1047 if let ExprKind::Lit(ref lit) = ex.node {
1048 use crate::syntax::ast::{LitIntType, LitKind};
1050 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1052 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1058 "casting to the same type is unnecessary (`{}` -> `{}`)",
1066 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1067 match (cast_from.is_integral(), cast_to.is_integral()) {
1069 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1070 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1075 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1076 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1078 if from_nbits < to_nbits {
1079 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1085 CAST_POSSIBLE_TRUNCATION,
1087 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1089 if !cast_to.is_signed() {
1094 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1099 if cast_from.is_signed() && !cast_to.is_signed() {
1104 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1107 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1108 check_lossless(cx, expr, ex, cast_from, cast_to);
1111 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1114 CAST_POSSIBLE_TRUNCATION,
1116 "casting f64 to f32 may truncate the value",
1119 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1120 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1127 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1128 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1129 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1130 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1131 if from_align < to_align;
1132 // with c_void, we inherently need to trust the user
1133 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1139 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1147 fn lint_fn_to_numeric_cast(
1148 cx: &LateContext<'_, '_>,
1154 // We only want to check casts to `ty::Uint` or `ty::Int`
1156 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1159 match cast_from.sty {
1160 ty::FnDef(..) | ty::FnPtr(_) => {
1161 let mut applicability = Applicability::MachineApplicable;
1162 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1164 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1165 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1168 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1171 "casting function pointer `{}` to `{}`, which truncates the value",
1172 from_snippet, cast_to
1175 format!("{} as usize", from_snippet),
1178 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1183 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1185 format!("{} as usize", from_snippet),
1194 /// **What it does:** Checks for types used in structs, parameters and `let`
1195 /// declarations above a certain complexity threshold.
1197 /// **Why is this bad?** Too complex types make the code less readable. Consider
1198 /// using a `type` definition to simplify them.
1200 /// **Known problems:** None.
1205 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1208 declare_clippy_lint! {
1209 pub TYPE_COMPLEXITY,
1211 "usage of very complex types that might be better factored into `type` definitions"
1214 pub struct TypeComplexityPass {
1218 impl TypeComplexityPass {
1219 pub fn new(threshold: u64) -> Self {
1224 impl LintPass for TypeComplexityPass {
1225 fn get_lints(&self) -> LintArray {
1226 lint_array!(TYPE_COMPLEXITY)
1230 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1233 cx: &LateContext<'a, 'tcx>,
1240 self.check_fndecl(cx, decl);
1243 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1244 // enum variants are also struct fields now
1245 self.check_type(cx, &field.ty);
1248 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1250 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1251 // functions, enums, structs, impls and traits are covered
1256 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1258 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1259 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1260 // methods with default impl are covered by check_fn
1265 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1267 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1268 // methods are covered by check_fn
1273 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1274 if let Some(ref ty) = local.ty {
1275 self.check_type(cx, ty);
1280 impl<'a, 'tcx> TypeComplexityPass {
1281 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1282 for arg in &decl.inputs {
1283 self.check_type(cx, arg);
1285 if let Return(ref ty) = decl.output {
1286 self.check_type(cx, ty);
1290 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1291 if in_macro(ty.span) {
1295 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1296 visitor.visit_ty(ty);
1300 if score > self.threshold {
1305 "very complex type used. Consider factoring parts into `type` definitions",
1311 /// Walks a type and assigns a complexity score to it.
1312 struct TypeComplexityVisitor {
1313 /// total complexity score of the type
1315 /// current nesting level
1319 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1320 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1321 let (add_score, sub_nest) = match ty.node {
1322 // _, &x and *x have only small overhead; don't mess with nesting level
1323 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1325 // the "normal" components of a type: named types, arrays/tuples
1326 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1328 // function types bring a lot of overhead
1329 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1331 TyKind::TraitObject(ref param_bounds, _) => {
1332 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1333 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1334 GenericParamKind::Lifetime { .. } => true,
1338 if has_lifetime_parameters {
1339 // complex trait bounds like A<'a, 'b>
1342 // simple trait bounds like A + B
1349 self.score += add_score;
1350 self.nest += sub_nest;
1352 self.nest -= sub_nest;
1354 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1355 NestedVisitorMap::None
1359 /// **What it does:** Checks for expressions where a character literal is cast
1360 /// to `u8` and suggests using a byte literal instead.
1362 /// **Why is this bad?** In general, casting values to smaller types is
1363 /// error-prone and should be avoided where possible. In the particular case of
1364 /// converting a character literal to u8, it is easy to avoid by just using a
1365 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1366 /// than `'a' as u8`.
1368 /// **Known problems:** None.
1375 /// A better version, using the byte literal:
1380 declare_clippy_lint! {
1383 "casting a character literal to u8"
1386 pub struct CharLitAsU8;
1388 impl LintPass for CharLitAsU8 {
1389 fn get_lints(&self) -> LintArray {
1390 lint_array!(CHAR_LIT_AS_U8)
1394 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1395 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1396 use crate::syntax::ast::{LitKind, UintTy};
1398 if let ExprKind::Cast(ref e, _) = expr.node {
1399 if let ExprKind::Lit(ref l) = e.node {
1400 if let LitKind::Char(_) = l.node {
1401 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1402 let msg = "casting character literal to u8. `char`s \
1403 are 4 bytes wide in rust, so casting to u8 \
1406 "Consider using a byte literal instead:\nb{}",
1407 snippet(cx, e.span, "'x'")
1409 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1417 /// **What it does:** Checks for comparisons where one side of the relation is
1418 /// either the minimum or maximum value for its type and warns if it involves a
1419 /// case that is always true or always false. Only integer and boolean types are
1422 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1423 /// that is is possible for `x` to be less than the minimum. Expressions like
1424 /// `max < x` are probably mistakes.
1426 /// **Known problems:** For `usize` the size of the current compile target will
1427 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1428 /// a comparison to detect target pointer width will trigger this lint. One can
1429 /// use `mem::sizeof` and compare its value or conditional compilation
1431 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1436 /// 100 > std::i32::MAX
1438 declare_clippy_lint! {
1439 pub ABSURD_EXTREME_COMPARISONS,
1441 "a comparison with a maximum or minimum value that is always true or false"
1444 pub struct AbsurdExtremeComparisons;
1446 impl LintPass for AbsurdExtremeComparisons {
1447 fn get_lints(&self) -> LintArray {
1448 lint_array!(ABSURD_EXTREME_COMPARISONS)
1457 struct ExtremeExpr<'a> {
1462 enum AbsurdComparisonResult {
1465 InequalityImpossible,
1468 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1469 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1470 let precast_ty = cx.tables.expr_ty(cast_exp);
1471 let cast_ty = cx.tables.expr_ty(expr);
1473 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1479 fn detect_absurd_comparison<'a, 'tcx>(
1480 cx: &LateContext<'a, 'tcx>,
1484 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1485 use crate::types::AbsurdComparisonResult::*;
1486 use crate::types::ExtremeType::*;
1487 use crate::utils::comparisons::*;
1489 // absurd comparison only makes sense on primitive types
1490 // primitive types don't implement comparison operators with each other
1491 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1495 // comparisons between fix sized types and target sized types are considered unanalyzable
1496 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1500 let normalized = normalize_comparison(op, lhs, rhs);
1501 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1507 let lx = detect_extreme_expr(cx, normalized_lhs);
1508 let rx = detect_extreme_expr(cx, normalized_rhs);
1513 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1514 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1520 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1521 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1522 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1523 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1527 Rel::Ne | Rel::Eq => return None,
1531 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1532 use crate::types::ExtremeType::*;
1534 let ty = cx.tables.expr_ty(expr);
1536 let cv = constant(cx, cx.tables, expr)?.0;
1538 let which = match (&ty.sty, cv) {
1539 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1540 (&ty::Int(ity), Constant::Int(i))
1541 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1546 (&ty::Bool, Constant::Bool(true)) => Maximum,
1547 (&ty::Int(ity), Constant::Int(i))
1548 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1552 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1556 Some(ExtremeExpr { which, expr })
1559 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1560 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1561 use crate::types::AbsurdComparisonResult::*;
1562 use crate::types::ExtremeType::*;
1564 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1565 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1566 if !in_macro(expr.span) {
1567 let msg = "this comparison involving the minimum or maximum element for this \
1568 type contains a case that is always true or always false";
1570 let conclusion = match result {
1571 AlwaysFalse => "this comparison is always false".to_owned(),
1572 AlwaysTrue => "this comparison is always true".to_owned(),
1573 InequalityImpossible => format!(
1574 "the case where the two sides are not equal never occurs, consider using {} == {} \
1576 snippet(cx, lhs.span, "lhs"),
1577 snippet(cx, rhs.span, "rhs")
1582 "because {} is the {} value for this type, {}",
1583 snippet(cx, culprit.expr.span, "x"),
1584 match culprit.which {
1585 Minimum => "minimum",
1586 Maximum => "maximum",
1591 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1598 /// **What it does:** Checks for comparisons where the relation is always either
1599 /// true or false, but where one side has been upcast so that the comparison is
1600 /// necessary. Only integer types are checked.
1602 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1603 /// will mistakenly imply that it is possible for `x` to be outside the range of
1606 /// **Known problems:**
1607 /// https://github.com/rust-lang/rust-clippy/issues/886
1611 /// let x : u8 = ...; (x as u32) > 300
1613 declare_clippy_lint! {
1614 pub INVALID_UPCAST_COMPARISONS,
1616 "a comparison involving an upcast which is always true or false"
1619 pub struct InvalidUpcastComparisons;
1621 impl LintPass for InvalidUpcastComparisons {
1622 fn get_lints(&self) -> LintArray {
1623 lint_array!(INVALID_UPCAST_COMPARISONS)
1627 #[derive(Copy, Clone, Debug, Eq)]
1634 #[allow(clippy::cast_sign_loss)]
1635 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1638 } else if u > (i128::max_value() as u128) {
1646 impl PartialEq for FullInt {
1647 fn eq(&self, other: &Self) -> bool {
1648 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1652 impl PartialOrd for FullInt {
1653 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1654 Some(match (self, other) {
1655 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1656 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1657 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1658 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1662 impl Ord for FullInt {
1663 fn cmp(&self, other: &Self) -> Ordering {
1664 self.partial_cmp(other)
1665 .expect("partial_cmp for FullInt can never return None")
1669 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1670 use crate::syntax::ast::{IntTy, UintTy};
1673 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1674 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1675 let cast_ty = cx.tables.expr_ty(expr);
1676 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1677 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1680 match pre_cast_ty.sty {
1681 ty::Int(int_ty) => Some(match int_ty {
1683 FullInt::S(i128::from(i8::min_value())),
1684 FullInt::S(i128::from(i8::max_value())),
1687 FullInt::S(i128::from(i16::min_value())),
1688 FullInt::S(i128::from(i16::max_value())),
1691 FullInt::S(i128::from(i32::min_value())),
1692 FullInt::S(i128::from(i32::max_value())),
1695 FullInt::S(i128::from(i64::min_value())),
1696 FullInt::S(i128::from(i64::max_value())),
1698 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1700 FullInt::S(isize::min_value() as i128),
1701 FullInt::S(isize::max_value() as i128),
1704 ty::Uint(uint_ty) => Some(match uint_ty {
1706 FullInt::U(u128::from(u8::min_value())),
1707 FullInt::U(u128::from(u8::max_value())),
1710 FullInt::U(u128::from(u16::min_value())),
1711 FullInt::U(u128::from(u16::max_value())),
1714 FullInt::U(u128::from(u32::min_value())),
1715 FullInt::U(u128::from(u32::max_value())),
1718 FullInt::U(u128::from(u64::min_value())),
1719 FullInt::U(u128::from(u64::max_value())),
1721 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1723 FullInt::U(usize::min_value() as u128),
1724 FullInt::U(usize::max_value() as u128),
1734 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1735 let val = constant(cx, cx.tables, expr)?.0;
1736 if let Constant::Int(const_int) = val {
1737 match cx.tables.expr_ty(expr).sty {
1738 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1739 ty::Uint(_) => Some(FullInt::U(const_int)),
1747 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1748 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1751 INVALID_UPCAST_COMPARISONS,
1754 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1755 snippet(cx, cast_val.span, "the expression"),
1756 if always { "true" } else { "false" },
1762 fn upcast_comparison_bounds_err<'a, 'tcx>(
1763 cx: &LateContext<'a, 'tcx>,
1765 rel: comparisons::Rel,
1766 lhs_bounds: Option<(FullInt, FullInt)>,
1771 use crate::utils::comparisons::*;
1773 if let Some((lb, ub)) = lhs_bounds {
1774 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1775 if rel == Rel::Eq || rel == Rel::Ne {
1776 if norm_rhs_val < lb || norm_rhs_val > ub {
1777 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1779 } else if match rel {
1794 Rel::Eq | Rel::Ne => unreachable!(),
1796 err_upcast_comparison(cx, span, lhs, true)
1797 } else if match rel {
1812 Rel::Eq | Rel::Ne => unreachable!(),
1814 err_upcast_comparison(cx, span, lhs, false)
1820 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1821 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1822 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1823 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1824 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1830 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1831 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1833 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1834 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1839 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1840 /// over different hashers and implicitly defaulting to the default hashing
1841 /// algorithm (SipHash).
1843 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1846 /// **Known problems:** Suggestions for replacing constructors can contain
1847 /// false-positives. Also applying suggestions can require modification of other
1848 /// pieces of code, possibly including external crates.
1852 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1854 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1856 declare_clippy_lint! {
1857 pub IMPLICIT_HASHER,
1859 "missing generalization over different hashers"
1862 pub struct ImplicitHasher;
1864 impl LintPass for ImplicitHasher {
1865 fn get_lints(&self) -> LintArray {
1866 lint_array!(IMPLICIT_HASHER)
1870 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1871 #[allow(clippy::cast_possible_truncation)]
1872 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1873 use crate::syntax_pos::BytePos;
1875 fn suggestion<'a, 'tcx>(
1876 cx: &LateContext<'a, 'tcx>,
1877 db: &mut DiagnosticBuilder<'_>,
1878 generics_span: Span,
1879 generics_suggestion_span: Span,
1880 target: &ImplicitHasherType<'_>,
1881 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1883 let generics_snip = snippet(cx, generics_span, "");
1885 let generics_snip = if generics_snip.is_empty() {
1888 &generics_snip[1..generics_snip.len() - 1]
1893 "consider adding a type parameter".to_string(),
1896 generics_suggestion_span,
1898 "<{}{}S: ::std::hash::BuildHasher{}>",
1900 if generics_snip.is_empty() { "" } else { ", " },
1901 if vis.suggestions.is_empty() {
1904 // request users to add `Default` bound so that generic constructors can be used
1911 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1916 if !vis.suggestions.is_empty() {
1917 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1921 if !cx.access_levels.is_exported(item.id) {
1926 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1927 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1930 for target in &vis.found {
1931 if differing_macro_contexts(item.span, target.span()) {
1935 let generics_suggestion_span = generics.span.substitute_dummy({
1936 let pos = snippet_opt(cx, item.span.until(target.span()))
1937 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
1938 if let Some(pos) = pos {
1939 Span::new(pos, pos, item.span.data().ctxt)
1945 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1946 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
1947 ctr_vis.visit_impl_item(item);
1955 "impl for `{}` should be generalized over different hashers",
1959 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1964 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
1965 let body = cx.tcx.hir().body(body_id);
1967 for ty in &decl.inputs {
1968 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1971 for target in &vis.found {
1972 let generics_suggestion_span = generics.span.substitute_dummy({
1973 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
1975 let i = snip.find("fn")?;
1976 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
1978 .expect("failed to create span for type parameters");
1979 Span::new(pos, pos, item.span.data().ctxt)
1982 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1983 ctr_vis.visit_body(body);
1990 "parameter of type `{}` should be generalized over different hashers",
1994 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2005 enum ImplicitHasherType<'tcx> {
2006 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2007 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2010 impl<'tcx> ImplicitHasherType<'tcx> {
2011 /// Checks that `ty` is a target type without a BuildHasher.
2012 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2013 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2014 let params: Vec<_> = path
2022 .filter_map(|arg| match arg {
2023 GenericArg::Type(ty) => Some(ty),
2024 GenericArg::Lifetime(_) => None,
2027 let params_len = params.len();
2029 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2031 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2032 Some(ImplicitHasherType::HashMap(
2035 snippet(cx, params[0].span, "K"),
2036 snippet(cx, params[1].span, "V"),
2038 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2039 Some(ImplicitHasherType::HashSet(
2042 snippet(cx, params[0].span, "T"),
2052 fn type_name(&self) -> &'static str {
2054 ImplicitHasherType::HashMap(..) => "HashMap",
2055 ImplicitHasherType::HashSet(..) => "HashSet",
2059 fn type_arguments(&self) -> String {
2061 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2062 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2066 fn ty(&self) -> Ty<'tcx> {
2068 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2072 fn span(&self) -> Span {
2074 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2079 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2080 cx: &'a LateContext<'a, 'tcx>,
2081 found: Vec<ImplicitHasherType<'tcx>>,
2084 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2085 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2086 Self { cx, found: vec![] }
2090 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2091 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2092 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2093 self.found.push(target);
2099 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2100 NestedVisitorMap::None
2104 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2105 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2106 cx: &'a LateContext<'a, 'tcx>,
2107 body: &'a TypeckTables<'tcx>,
2108 target: &'b ImplicitHasherType<'tcx>,
2109 suggestions: BTreeMap<Span, String>,
2112 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2113 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2118 suggestions: BTreeMap::new(),
2123 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2124 fn visit_body(&mut self, body: &'tcx Body) {
2125 self.body = self.cx.tcx.body_tables(body.id());
2126 walk_body(self, body);
2129 fn visit_expr(&mut self, e: &'tcx Expr) {
2131 if let ExprKind::Call(ref fun, ref args) = e.node;
2132 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2133 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2135 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2139 if match_path(ty_path, &paths::HASHMAP) {
2140 if method.ident.name == "new" {
2142 .insert(e.span, "HashMap::default()".to_string());
2143 } else if method.ident.name == "with_capacity" {
2144 self.suggestions.insert(
2147 "HashMap::with_capacity_and_hasher({}, Default::default())",
2148 snippet(self.cx, args[0].span, "capacity"),
2152 } else if match_path(ty_path, &paths::HASHSET) {
2153 if method.ident.name == "new" {
2155 .insert(e.span, "HashSet::default()".to_string());
2156 } else if method.ident.name == "with_capacity" {
2157 self.suggestions.insert(
2160 "HashSet::with_capacity_and_hasher({}, Default::default())",
2161 snippet(self.cx, args[0].span, "capacity"),
2172 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2173 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())