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::utils::paths;
17 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
18 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
19 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
22 use if_chain::if_chain;
24 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
26 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
27 use rustc::ty::layout::LayoutOf;
28 use rustc::ty::{self, Ty, TyCtxt, TypeckTables};
29 use rustc::{declare_tool_lint, lint_array};
30 use rustc_errors::Applicability;
31 use rustc_target::spec::abi::Abi;
32 use rustc_typeck::hir_ty_to_ty;
34 use std::cmp::Ordering;
35 use std::collections::BTreeMap;
36 use syntax::ast::{FloatTy, IntTy, UintTy};
37 use syntax::errors::DiagnosticBuilder;
38 use syntax::source_map::Span;
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,
82 /// values: Vec<Box<i32>>,
93 declare_clippy_lint! {
96 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
99 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
102 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
103 /// represents an optional optional value which is logically the same thing as an optional
104 /// value but has an unneeded extra level of wrapping.
106 /// **Known problems:** None.
110 /// fn x() -> Option<Option<u32>> {
113 declare_clippy_lint! {
116 "usage of `Option<Option<T>>`"
119 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
120 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
122 /// **Why is this bad?** Gankro says:
124 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
125 /// pointers and indirection.
126 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
128 /// > "only" amortized for push/pop, should be faster in the general case for
129 /// almost every possible
130 /// > workload, and isn't even amortized at all if you can predict the capacity
133 /// > `LinkedList`s are only really good if you're doing a lot of merging or
134 /// splitting of lists.
135 /// > This is because they can just mangle some pointers instead of actually
136 /// copying the data. Even
137 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
138 /// can still be better
139 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
141 /// **Known problems:** False positives – the instances where using a
142 /// `LinkedList` makes sense are few and far between, but they can still happen.
146 /// let x = LinkedList::new();
148 declare_clippy_lint! {
151 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
154 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
156 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
159 /// **Known problems:** None.
163 /// fn foo(bar: &Box<T>) { ... }
169 /// fn foo(bar: &T) { ... }
171 declare_clippy_lint! {
174 "a borrow of a boxed type"
177 impl LintPass for TypePass {
178 fn get_lints(&self) -> LintArray {
179 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
183 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
184 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
185 // skip trait implementations, see #605
186 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(id)) {
187 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
192 check_fn_decl(cx, decl);
195 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
196 check_ty(cx, &field.ty, false);
199 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
201 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
202 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
207 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
208 if let Some(ref ty) = local.ty {
209 check_ty(cx, ty, true);
214 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
215 for input in &decl.inputs {
216 check_ty(cx, input, false);
219 if let FunctionRetTy::Return(ref ty) = decl.output {
220 check_ty(cx, ty, false);
224 /// Check if `qpath` has last segment with type parameter matching `path`
225 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
226 let last = last_path_segment(qpath);
228 if let Some(ref params) = last.args;
229 if !params.parenthesized;
230 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
231 GenericArg::Type(ty) => Some(ty),
232 GenericArg::Lifetime(_) => None,
234 if let TyKind::Path(ref qpath) = ty.node;
235 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
236 if match_def_path(cx.tcx, did, path);
244 /// Recursively check for `TypePass` lints in the given type. Stop at the first
247 /// The parameter `is_local` distinguishes the context of the type; types from
248 /// local bindings should only be checked for the `BORROWED_BOX` lint.
249 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
250 if in_macro(ast_ty.span) {
254 TyKind::Path(ref qpath) if !is_local => {
255 let hir_id = cx.tcx.hir().node_to_hir_id(ast_ty.id);
256 let def = cx.tables.qpath_def(qpath, hir_id);
257 if let Some(def_id) = opt_def_id(def) {
258 if Some(def_id) == cx.tcx.lang_items().owned_box() {
259 if match_type_parameter(cx, qpath, &paths::VEC) {
264 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
265 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
267 return; // don't recurse into the type
269 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
271 // Get the _ part of Vec<_>
272 if let Some(ref last) = last_path_segment(qpath).args;
273 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
274 GenericArg::Type(ty) => Some(ty),
275 GenericArg::Lifetime(_) => None,
277 // ty is now _ at this point
278 if let TyKind::Path(ref ty_qpath) = ty.node;
279 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
280 if let Some(def_id) = opt_def_id(def);
281 if Some(def_id) == cx.tcx.lang_items().owned_box();
282 // At this point, we know ty is Box<T>, now get T
283 if let Some(ref last) = last_path_segment(ty_qpath).args;
284 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
285 GenericArg::Type(ty) => Some(ty),
286 GenericArg::Lifetime(_) => None,
288 if let TyKind::Path(ref ty_qpath) = ty.node;
289 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
290 if let Some(def_id) = opt_def_id(def);
291 let boxed_type = cx.tcx.type_of(def_id);
292 if boxed_type.is_sized(cx.tcx.at(ty.span), cx.param_env);
298 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
300 format!("Vec<{}>", boxed_type),
301 Applicability::MaybeIncorrect,
303 return; // don't recurse into the type
306 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
307 if match_type_parameter(cx, qpath, &paths::OPTION) {
312 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
313 enum if you need to distinguish all 3 cases",
315 return; // don't recurse into the type
317 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
322 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
323 "a VecDeque might work",
325 return; // don't recurse into the type
329 QPath::Resolved(Some(ref ty), ref p) => {
330 check_ty(cx, ty, is_local);
331 for ty in p.segments.iter().flat_map(|seg| {
334 .map_or_else(|| [].iter(), |params| params.args.iter())
335 .filter_map(|arg| match arg {
336 GenericArg::Type(ty) => Some(ty),
337 GenericArg::Lifetime(_) => None,
340 check_ty(cx, ty, is_local);
343 QPath::Resolved(None, ref p) => {
344 for ty in p.segments.iter().flat_map(|seg| {
347 .map_or_else(|| [].iter(), |params| params.args.iter())
348 .filter_map(|arg| match arg {
349 GenericArg::Type(ty) => Some(ty),
350 GenericArg::Lifetime(_) => None,
353 check_ty(cx, ty, is_local);
356 QPath::TypeRelative(ref ty, ref seg) => {
357 check_ty(cx, ty, is_local);
358 if let Some(ref params) = seg.args {
359 for ty in params.args.iter().filter_map(|arg| match arg {
360 GenericArg::Type(ty) => Some(ty),
361 GenericArg::Lifetime(_) => None,
363 check_ty(cx, ty, is_local);
369 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
371 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
372 check_ty(cx, ty, is_local)
374 TyKind::Tup(ref tys) => {
376 check_ty(cx, ty, is_local);
383 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
384 match mut_ty.ty.node {
385 TyKind::Path(ref qpath) => {
386 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
387 let def = cx.tables.qpath_def(qpath, hir_id);
389 if let Some(def_id) = opt_def_id(def);
390 if Some(def_id) == cx.tcx.lang_items().owned_box();
391 if let QPath::Resolved(None, ref path) = *qpath;
392 if let [ref bx] = *path.segments;
393 if let Some(ref params) = bx.args;
394 if !params.parenthesized;
395 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
396 GenericArg::Type(ty) => Some(ty),
397 GenericArg::Lifetime(_) => None,
400 if is_any_trait(inner) {
401 // Ignore `Box<Any>` types, see #1884 for details.
405 let ltopt = if lt.is_elided() {
408 format!("{} ", lt.name.ident().as_str())
410 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
415 let mut applicability = Applicability::MachineApplicable;
420 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
426 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
428 Applicability::Unspecified,
430 return; // don't recurse into the type
433 check_ty(cx, &mut_ty.ty, is_local);
435 _ => check_ty(cx, &mut_ty.ty, is_local),
439 // Returns true if given type is `Any` trait.
440 fn is_any_trait(t: &hir::Ty) -> bool {
442 if let TyKind::TraitObject(ref traits, _) = t.node;
443 if traits.len() >= 1;
444 // Only Send/Sync can be used as additional traits, so it is enough to
445 // check only the first trait.
446 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
457 /// **What it does:** Checks for binding a unit value.
459 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
460 /// binding one is kind of pointless.
462 /// **Known problems:** None.
470 declare_clippy_lint! {
473 "creating a let binding to a value of unit type, which usually can't be used afterwards"
476 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
477 if let DeclKind::Local(ref local) = decl.node {
478 if is_unit(cx.tables.pat_ty(&local.pat)) {
479 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
482 if higher::is_from_for_desugar(decl) {
490 "this let-binding has unit value. Consider omitting `let {} =`",
491 snippet(cx, local.pat.span, "..")
498 impl LintPass for LetPass {
499 fn get_lints(&self) -> LintArray {
500 lint_array!(LET_UNIT_VALUE)
504 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
505 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
506 check_let_unit(cx, decl)
510 /// **What it does:** Checks for comparisons to unit.
512 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
513 /// clumsily written constant. Mostly this happens when someone accidentally
514 /// adds semicolons at the end of the operands.
516 /// **Known problems:** None.
536 declare_clippy_lint! {
539 "comparing unit values"
544 impl LintPass for UnitCmp {
545 fn get_lints(&self) -> LintArray {
546 lint_array!(UNIT_CMP)
550 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
551 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
552 if in_macro(expr.span) {
555 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
557 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
558 let result = match op {
559 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
567 "{}-comparison of unit values detected. This will always be {}",
577 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
578 /// unit literal (`()`).
580 /// **Why is this bad?** This is likely the result of an accidental semicolon.
582 /// **Known problems:** None.
591 declare_clippy_lint! {
594 "passing unit to a function"
599 impl LintPass for UnitArg {
600 fn get_lints(&self) -> LintArray {
601 lint_array!(UNIT_ARG)
605 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
606 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
607 if in_macro(expr.span) {
611 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
613 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
614 let map = &cx.tcx.hir();
615 // apparently stuff in the desugaring of `?` can trigger this
616 // so check for that here
617 // only the calls to `Try::from_error` is marked as desugared,
618 // so we need to check both the current Expr and its parent.
619 if !is_questionmark_desugar_marked_call(expr) {
621 let opt_parent_node = map.find(map.get_parent_node(expr.id));
622 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
623 if is_questionmark_desugar_marked_call(parent_expr);
626 // `expr` and `parent_expr` where _both_ not from
627 // desugaring `?`, so lint
632 "passing a unit value to a function",
633 "if you intended to pass a unit value, use a unit literal instead",
635 Applicability::MachineApplicable,
648 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
649 use syntax_pos::hygiene::CompilerDesugaringKind;
650 if let ExprKind::Call(ref callee, _) = expr.node {
651 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
657 fn is_unit(ty: Ty<'_>) -> bool {
659 ty::Tuple(slice) if slice.is_empty() => true,
664 fn is_unit_literal(expr: &Expr) -> bool {
666 ExprKind::Tup(ref slice) if slice.is_empty() => true,
673 /// **What it does:** Checks for casts from any numerical to a float type where
674 /// the receiving type cannot store all values from the original type without
675 /// rounding errors. This possible rounding is to be expected, so this lint is
676 /// `Allow` by default.
678 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
679 /// or any 64-bit integer to `f64`.
681 /// **Why is this bad?** It's not bad at all. But in some applications it can be
682 /// helpful to know where precision loss can take place. This lint can help find
683 /// those places in the code.
685 /// **Known problems:** None.
689 /// let x = u64::MAX;
692 declare_clippy_lint! {
693 pub CAST_PRECISION_LOSS,
695 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
698 /// **What it does:** Checks for casts from a signed to an unsigned numerical
699 /// type. In this case, negative values wrap around to large positive values,
700 /// which can be quite surprising in practice. However, as the cast works as
701 /// defined, this lint is `Allow` by default.
703 /// **Why is this bad?** Possibly surprising results. You can activate this lint
704 /// as a one-time check to see where numerical wrapping can arise.
706 /// **Known problems:** None.
711 /// y as u128 // will return 18446744073709551615
713 declare_clippy_lint! {
716 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
719 /// **What it does:** Checks for on casts between numerical types that may
720 /// truncate large values. This is expected behavior, so the cast is `Allow` by
723 /// **Why is this bad?** In some problem domains, it is good practice to avoid
724 /// truncation. This lint can be activated to help assess where additional
725 /// checks could be beneficial.
727 /// **Known problems:** None.
731 /// fn as_u8(x: u64) -> u8 {
735 declare_clippy_lint! {
736 pub CAST_POSSIBLE_TRUNCATION,
738 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
741 /// **What it does:** Checks for casts from an unsigned type to a signed type of
742 /// the same size. Performing such a cast is a 'no-op' for the compiler,
743 /// i.e. nothing is changed at the bit level, and the binary representation of
744 /// the value is reinterpreted. This can cause wrapping if the value is too big
745 /// for the target signed type. However, the cast works as defined, so this lint
746 /// is `Allow` by default.
748 /// **Why is this bad?** While such a cast is not bad in itself, the results can
749 /// be surprising when this is not the intended behavior, as demonstrated by the
752 /// **Known problems:** None.
756 /// u32::MAX as i32 // will yield a value of `-1`
758 declare_clippy_lint! {
759 pub CAST_POSSIBLE_WRAP,
761 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
764 /// **What it does:** Checks for on casts between numerical types that may
765 /// be replaced by safe conversion functions.
767 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
768 /// conversions, including silently lossy conversions. Conversion functions such
769 /// as `i32::from` will only perform lossless conversions. Using the conversion
770 /// functions prevents conversions from turning into silent lossy conversions if
771 /// the types of the input expressions ever change, and make it easier for
772 /// people reading the code to know that the conversion is lossless.
774 /// **Known problems:** None.
778 /// fn as_u64(x: u8) -> u64 {
783 /// Using `::from` would look like this:
786 /// fn as_u64(x: u8) -> u64 {
790 declare_clippy_lint! {
793 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
796 /// **What it does:** Checks for casts to the same type.
798 /// **Why is this bad?** It's just unnecessary.
800 /// **Known problems:** None.
804 /// let _ = 2i32 as i32
806 declare_clippy_lint! {
807 pub UNNECESSARY_CAST,
809 "cast to the same type, e.g. `x as i32` where `x: i32`"
812 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
813 /// more-strictly-aligned pointer
815 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
818 /// **Known problems:** None.
822 /// let _ = (&1u8 as *const u8) as *const u16;
823 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
825 declare_clippy_lint! {
826 pub CAST_PTR_ALIGNMENT,
828 "cast from a pointer to a more-strictly-aligned pointer"
831 /// **What it does:** Checks for casts of function pointers to something other than usize
833 /// **Why is this bad?**
834 /// Casting a function pointer to anything other than usize/isize is not portable across
835 /// architectures, because you end up losing bits if the target type is too small or end up with a
836 /// bunch of extra bits that waste space and add more instructions to the final binary than
837 /// strictly necessary for the problem
839 /// Casting to isize also doesn't make sense since there are no signed addresses.
845 /// fn fun() -> i32 {}
846 /// let a = fun as i64;
849 /// fn fun2() -> i32 {}
850 /// let a = fun2 as usize;
852 declare_clippy_lint! {
853 pub FN_TO_NUMERIC_CAST,
855 "casting a function pointer to a numeric type other than usize"
858 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
861 /// **Why is this bad?**
862 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
863 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
864 /// a comment) to perform the truncation.
870 /// fn fn1() -> i16 {
873 /// let _ = fn1 as i32;
875 /// // Better: Cast to usize first, then comment with the reason for the truncation
876 /// fn fn2() -> i16 {
879 /// let fn_ptr = fn2 as usize;
880 /// let fn_ptr_truncated = fn_ptr as i32;
882 declare_clippy_lint! {
883 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
885 "casting a function pointer to a numeric type not wide enough to store the address"
888 /// Returns the size in bits of an integral type.
889 /// Will return 0 if the type is not an int or uint variant
890 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
892 ty::Int(i) => match i {
893 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
900 ty::Uint(i) => match i {
901 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
912 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
914 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
919 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
920 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
921 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
922 let arch_dependent_str = "on targets with 64-bit wide pointers ";
923 let from_nbits_str = if arch_dependent {
925 } else if is_isize_or_usize(cast_from) {
926 "32 or 64".to_owned()
928 int_ty_to_nbits(cast_from, cx.tcx).to_string()
935 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
936 is only {4} bits wide)",
938 if cast_to_f64 { "f64" } else { "f32" },
939 if arch_dependent { arch_dependent_str } else { "" },
946 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
947 if let ExprKind::Binary(_, _, _) = op.node {
948 if snip.starts_with('(') && snip.ends_with(')') {
955 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
956 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
957 if in_constant(cx, expr.id) {
960 // The suggestion is to use a function call, so if the original expression
961 // has parens on the outside, they are no longer needed.
962 let mut applicability = Applicability::MachineApplicable;
963 let opt = snippet_opt(cx, op.span);
964 let sugg = if let Some(ref snip) = opt {
965 if should_strip_parens(op, snip) {
966 &snip[1..snip.len() - 1]
971 applicability = Applicability::HasPlaceholders;
980 "casting {} to {} may become silently lossy if types change",
984 format!("{}::from({})", cast_to, sugg),
995 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
996 let arch_64_suffix = " on targets with 64-bit wide pointers";
997 let arch_32_suffix = " on targets with 32-bit wide pointers";
998 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
999 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1000 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1001 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1002 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1003 (true, true) | (false, false) => (
1004 to_nbits < from_nbits,
1006 to_nbits == from_nbits && cast_unsigned_to_signed,
1016 to_nbits <= 32 && cast_unsigned_to_signed,
1022 cast_unsigned_to_signed,
1023 if from_nbits == 64 {
1030 if span_truncation {
1033 CAST_POSSIBLE_TRUNCATION,
1036 "casting {} to {} may truncate the value{}",
1039 match suffix_truncation {
1040 ArchSuffix::_32 => arch_32_suffix,
1041 ArchSuffix::_64 => arch_64_suffix,
1042 ArchSuffix::None => "",
1053 "casting {} to {} may wrap around the value{}",
1057 ArchSuffix::_32 => arch_32_suffix,
1058 ArchSuffix::_64 => arch_64_suffix,
1059 ArchSuffix::None => "",
1066 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1067 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1068 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1069 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1070 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1072 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1076 impl LintPass for CastPass {
1077 fn get_lints(&self) -> LintArray {
1079 CAST_PRECISION_LOSS,
1081 CAST_POSSIBLE_TRUNCATION,
1087 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1092 // Check if the given type is either `core::ffi::c_void` or
1093 // one of the platform specific `libc::<platform>::c_void` of libc.
1094 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1095 if let ty::Adt(adt, _) = ty.sty {
1096 let mut apb = AbsolutePathBuffer { names: vec![] };
1097 tcx.push_item_path(&mut apb, adt.did, false);
1099 if apb.names.is_empty() {
1102 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1109 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1110 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1111 if let ExprKind::Cast(ref ex, _) = expr.node {
1112 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1113 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1114 if let ExprKind::Lit(ref lit) = ex.node {
1115 use syntax::ast::{LitIntType, LitKind};
1117 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1119 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1125 "casting to the same type is unnecessary (`{}` -> `{}`)",
1133 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1134 match (cast_from.is_integral(), cast_to.is_integral()) {
1136 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1137 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1142 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1143 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1145 if from_nbits < to_nbits {
1146 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1152 CAST_POSSIBLE_TRUNCATION,
1154 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1156 if !cast_to.is_signed() {
1161 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1166 if cast_from.is_signed() && !cast_to.is_signed() {
1171 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1174 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1175 check_lossless(cx, expr, ex, cast_from, cast_to);
1178 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1181 CAST_POSSIBLE_TRUNCATION,
1183 "casting f64 to f32 may truncate the value",
1186 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1187 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1194 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1195 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1196 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1197 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1198 if from_align < to_align;
1199 // with c_void, we inherently need to trust the user
1200 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1206 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1214 fn lint_fn_to_numeric_cast(
1215 cx: &LateContext<'_, '_>,
1221 // We only want to check casts to `ty::Uint` or `ty::Int`
1223 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1226 match cast_from.sty {
1227 ty::FnDef(..) | ty::FnPtr(_) => {
1228 let mut applicability = Applicability::MachineApplicable;
1229 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1231 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1232 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1235 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1238 "casting function pointer `{}` to `{}`, which truncates the value",
1239 from_snippet, cast_to
1242 format!("{} as usize", from_snippet),
1245 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1250 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1252 format!("{} as usize", from_snippet),
1261 /// **What it does:** Checks for types used in structs, parameters and `let`
1262 /// declarations above a certain complexity threshold.
1264 /// **Why is this bad?** Too complex types make the code less readable. Consider
1265 /// using a `type` definition to simplify them.
1267 /// **Known problems:** None.
1272 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1275 declare_clippy_lint! {
1276 pub TYPE_COMPLEXITY,
1278 "usage of very complex types that might be better factored into `type` definitions"
1281 pub struct TypeComplexityPass {
1285 impl TypeComplexityPass {
1286 pub fn new(threshold: u64) -> Self {
1291 impl LintPass for TypeComplexityPass {
1292 fn get_lints(&self) -> LintArray {
1293 lint_array!(TYPE_COMPLEXITY)
1297 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1300 cx: &LateContext<'a, 'tcx>,
1307 self.check_fndecl(cx, decl);
1310 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1311 // enum variants are also struct fields now
1312 self.check_type(cx, &field.ty);
1315 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1317 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1318 // functions, enums, structs, impls and traits are covered
1323 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1325 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1326 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1327 // methods with default impl are covered by check_fn
1332 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1334 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1335 // methods are covered by check_fn
1340 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1341 if let Some(ref ty) = local.ty {
1342 self.check_type(cx, ty);
1347 impl<'a, 'tcx> TypeComplexityPass {
1348 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1349 for arg in &decl.inputs {
1350 self.check_type(cx, arg);
1352 if let Return(ref ty) = decl.output {
1353 self.check_type(cx, ty);
1357 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1358 if in_macro(ty.span) {
1362 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1363 visitor.visit_ty(ty);
1367 if score > self.threshold {
1372 "very complex type used. Consider factoring parts into `type` definitions",
1378 /// Walks a type and assigns a complexity score to it.
1379 struct TypeComplexityVisitor {
1380 /// total complexity score of the type
1382 /// current nesting level
1386 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1387 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1388 let (add_score, sub_nest) = match ty.node {
1389 // _, &x and *x have only small overhead; don't mess with nesting level
1390 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1392 // the "normal" components of a type: named types, arrays/tuples
1393 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1395 // function types bring a lot of overhead
1396 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1398 TyKind::TraitObject(ref param_bounds, _) => {
1399 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1400 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1401 GenericParamKind::Lifetime { .. } => true,
1405 if has_lifetime_parameters {
1406 // complex trait bounds like A<'a, 'b>
1409 // simple trait bounds like A + B
1416 self.score += add_score;
1417 self.nest += sub_nest;
1419 self.nest -= sub_nest;
1421 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1422 NestedVisitorMap::None
1426 /// **What it does:** Checks for expressions where a character literal is cast
1427 /// to `u8` and suggests using a byte literal instead.
1429 /// **Why is this bad?** In general, casting values to smaller types is
1430 /// error-prone and should be avoided where possible. In the particular case of
1431 /// converting a character literal to u8, it is easy to avoid by just using a
1432 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1433 /// than `'a' as u8`.
1435 /// **Known problems:** None.
1442 /// A better version, using the byte literal:
1447 declare_clippy_lint! {
1450 "casting a character literal to u8"
1453 pub struct CharLitAsU8;
1455 impl LintPass for CharLitAsU8 {
1456 fn get_lints(&self) -> LintArray {
1457 lint_array!(CHAR_LIT_AS_U8)
1461 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1462 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1463 use syntax::ast::{LitKind, UintTy};
1465 if let ExprKind::Cast(ref e, _) = expr.node {
1466 if let ExprKind::Lit(ref l) = e.node {
1467 if let LitKind::Char(_) = l.node {
1468 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1469 let msg = "casting character literal to u8. `char`s \
1470 are 4 bytes wide in rust, so casting to u8 \
1473 "Consider using a byte literal instead:\nb{}",
1474 snippet(cx, e.span, "'x'")
1476 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1484 /// **What it does:** Checks for comparisons where one side of the relation is
1485 /// either the minimum or maximum value for its type and warns if it involves a
1486 /// case that is always true or always false. Only integer and boolean types are
1489 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1490 /// that is is possible for `x` to be less than the minimum. Expressions like
1491 /// `max < x` are probably mistakes.
1493 /// **Known problems:** For `usize` the size of the current compile target will
1494 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1495 /// a comparison to detect target pointer width will trigger this lint. One can
1496 /// use `mem::sizeof` and compare its value or conditional compilation
1498 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1503 /// 100 > std::i32::MAX
1505 declare_clippy_lint! {
1506 pub ABSURD_EXTREME_COMPARISONS,
1508 "a comparison with a maximum or minimum value that is always true or false"
1511 pub struct AbsurdExtremeComparisons;
1513 impl LintPass for AbsurdExtremeComparisons {
1514 fn get_lints(&self) -> LintArray {
1515 lint_array!(ABSURD_EXTREME_COMPARISONS)
1524 struct ExtremeExpr<'a> {
1529 enum AbsurdComparisonResult {
1532 InequalityImpossible,
1535 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1536 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1537 let precast_ty = cx.tables.expr_ty(cast_exp);
1538 let cast_ty = cx.tables.expr_ty(expr);
1540 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1546 fn detect_absurd_comparison<'a, 'tcx>(
1547 cx: &LateContext<'a, 'tcx>,
1551 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1552 use crate::types::AbsurdComparisonResult::*;
1553 use crate::types::ExtremeType::*;
1554 use crate::utils::comparisons::*;
1556 // absurd comparison only makes sense on primitive types
1557 // primitive types don't implement comparison operators with each other
1558 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1562 // comparisons between fix sized types and target sized types are considered unanalyzable
1563 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1567 let normalized = normalize_comparison(op, lhs, rhs);
1568 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1574 let lx = detect_extreme_expr(cx, normalized_lhs);
1575 let rx = detect_extreme_expr(cx, normalized_rhs);
1580 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1581 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1587 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1588 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1589 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1590 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1594 Rel::Ne | Rel::Eq => return None,
1598 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1599 use crate::types::ExtremeType::*;
1601 let ty = cx.tables.expr_ty(expr);
1603 let cv = constant(cx, cx.tables, expr)?.0;
1605 let which = match (&ty.sty, cv) {
1606 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1607 (&ty::Int(ity), Constant::Int(i))
1608 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1613 (&ty::Bool, Constant::Bool(true)) => Maximum,
1614 (&ty::Int(ity), Constant::Int(i))
1615 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1619 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1623 Some(ExtremeExpr { which, expr })
1626 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1627 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1628 use crate::types::AbsurdComparisonResult::*;
1629 use crate::types::ExtremeType::*;
1631 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1632 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1633 if !in_macro(expr.span) {
1634 let msg = "this comparison involving the minimum or maximum element for this \
1635 type contains a case that is always true or always false";
1637 let conclusion = match result {
1638 AlwaysFalse => "this comparison is always false".to_owned(),
1639 AlwaysTrue => "this comparison is always true".to_owned(),
1640 InequalityImpossible => format!(
1641 "the case where the two sides are not equal never occurs, consider using {} == {} \
1643 snippet(cx, lhs.span, "lhs"),
1644 snippet(cx, rhs.span, "rhs")
1649 "because {} is the {} value for this type, {}",
1650 snippet(cx, culprit.expr.span, "x"),
1651 match culprit.which {
1652 Minimum => "minimum",
1653 Maximum => "maximum",
1658 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1665 /// **What it does:** Checks for comparisons where the relation is always either
1666 /// true or false, but where one side has been upcast so that the comparison is
1667 /// necessary. Only integer types are checked.
1669 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1670 /// will mistakenly imply that it is possible for `x` to be outside the range of
1673 /// **Known problems:**
1674 /// https://github.com/rust-lang/rust-clippy/issues/886
1678 /// let x : u8 = ...; (x as u32) > 300
1680 declare_clippy_lint! {
1681 pub INVALID_UPCAST_COMPARISONS,
1683 "a comparison involving an upcast which is always true or false"
1686 pub struct InvalidUpcastComparisons;
1688 impl LintPass for InvalidUpcastComparisons {
1689 fn get_lints(&self) -> LintArray {
1690 lint_array!(INVALID_UPCAST_COMPARISONS)
1694 #[derive(Copy, Clone, Debug, Eq)]
1701 #[allow(clippy::cast_sign_loss)]
1702 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1705 } else if u > (i128::max_value() as u128) {
1713 impl PartialEq for FullInt {
1714 fn eq(&self, other: &Self) -> bool {
1715 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1719 impl PartialOrd for FullInt {
1720 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1721 Some(match (self, other) {
1722 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1723 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1724 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1725 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1729 impl Ord for FullInt {
1730 fn cmp(&self, other: &Self) -> Ordering {
1731 self.partial_cmp(other)
1732 .expect("partial_cmp for FullInt can never return None")
1736 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1738 use syntax::ast::{IntTy, UintTy};
1740 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1741 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1742 let cast_ty = cx.tables.expr_ty(expr);
1743 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1744 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1747 match pre_cast_ty.sty {
1748 ty::Int(int_ty) => Some(match int_ty {
1750 FullInt::S(i128::from(i8::min_value())),
1751 FullInt::S(i128::from(i8::max_value())),
1754 FullInt::S(i128::from(i16::min_value())),
1755 FullInt::S(i128::from(i16::max_value())),
1758 FullInt::S(i128::from(i32::min_value())),
1759 FullInt::S(i128::from(i32::max_value())),
1762 FullInt::S(i128::from(i64::min_value())),
1763 FullInt::S(i128::from(i64::max_value())),
1765 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1767 FullInt::S(isize::min_value() as i128),
1768 FullInt::S(isize::max_value() as i128),
1771 ty::Uint(uint_ty) => Some(match uint_ty {
1773 FullInt::U(u128::from(u8::min_value())),
1774 FullInt::U(u128::from(u8::max_value())),
1777 FullInt::U(u128::from(u16::min_value())),
1778 FullInt::U(u128::from(u16::max_value())),
1781 FullInt::U(u128::from(u32::min_value())),
1782 FullInt::U(u128::from(u32::max_value())),
1785 FullInt::U(u128::from(u64::min_value())),
1786 FullInt::U(u128::from(u64::max_value())),
1788 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1790 FullInt::U(usize::min_value() as u128),
1791 FullInt::U(usize::max_value() as u128),
1801 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1802 let val = constant(cx, cx.tables, expr)?.0;
1803 if let Constant::Int(const_int) = val {
1804 match cx.tables.expr_ty(expr).sty {
1805 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1806 ty::Uint(_) => Some(FullInt::U(const_int)),
1814 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1815 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1818 INVALID_UPCAST_COMPARISONS,
1821 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1822 snippet(cx, cast_val.span, "the expression"),
1823 if always { "true" } else { "false" },
1829 fn upcast_comparison_bounds_err<'a, 'tcx>(
1830 cx: &LateContext<'a, 'tcx>,
1832 rel: comparisons::Rel,
1833 lhs_bounds: Option<(FullInt, FullInt)>,
1838 use crate::utils::comparisons::*;
1840 if let Some((lb, ub)) = lhs_bounds {
1841 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1842 if rel == Rel::Eq || rel == Rel::Ne {
1843 if norm_rhs_val < lb || norm_rhs_val > ub {
1844 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1846 } else if match rel {
1861 Rel::Eq | Rel::Ne => unreachable!(),
1863 err_upcast_comparison(cx, span, lhs, true)
1864 } else if match rel {
1879 Rel::Eq | Rel::Ne => unreachable!(),
1881 err_upcast_comparison(cx, span, lhs, false)
1887 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1888 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1889 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1890 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1891 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1897 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1898 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1900 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1901 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1906 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1907 /// over different hashers and implicitly defaulting to the default hashing
1908 /// algorithm (SipHash).
1910 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1913 /// **Known problems:** Suggestions for replacing constructors can contain
1914 /// false-positives. Also applying suggestions can require modification of other
1915 /// pieces of code, possibly including external crates.
1919 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1921 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1923 declare_clippy_lint! {
1924 pub IMPLICIT_HASHER,
1926 "missing generalization over different hashers"
1929 pub struct ImplicitHasher;
1931 impl LintPass for ImplicitHasher {
1932 fn get_lints(&self) -> LintArray {
1933 lint_array!(IMPLICIT_HASHER)
1937 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1938 #[allow(clippy::cast_possible_truncation)]
1939 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1940 use syntax_pos::BytePos;
1942 fn suggestion<'a, 'tcx>(
1943 cx: &LateContext<'a, 'tcx>,
1944 db: &mut DiagnosticBuilder<'_>,
1945 generics_span: Span,
1946 generics_suggestion_span: Span,
1947 target: &ImplicitHasherType<'_>,
1948 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1950 let generics_snip = snippet(cx, generics_span, "");
1952 let generics_snip = if generics_snip.is_empty() {
1955 &generics_snip[1..generics_snip.len() - 1]
1960 "consider adding a type parameter".to_string(),
1963 generics_suggestion_span,
1965 "<{}{}S: ::std::hash::BuildHasher{}>",
1967 if generics_snip.is_empty() { "" } else { ", " },
1968 if vis.suggestions.is_empty() {
1971 // request users to add `Default` bound so that generic constructors can be used
1978 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1983 if !vis.suggestions.is_empty() {
1984 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1988 if !cx.access_levels.is_exported(item.id) {
1993 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1994 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1997 for target in &vis.found {
1998 if differing_macro_contexts(item.span, target.span()) {
2002 let generics_suggestion_span = generics.span.substitute_dummy({
2003 let pos = snippet_opt(cx, item.span.until(target.span()))
2004 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2005 if let Some(pos) = pos {
2006 Span::new(pos, pos, item.span.data().ctxt)
2012 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2013 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2014 ctr_vis.visit_impl_item(item);
2022 "impl for `{}` should be generalized over different hashers",
2026 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2031 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2032 let body = cx.tcx.hir().body(body_id);
2034 for ty in &decl.inputs {
2035 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2038 for target in &vis.found {
2039 let generics_suggestion_span = generics.span.substitute_dummy({
2040 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2042 let i = snip.find("fn")?;
2043 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2045 .expect("failed to create span for type parameters");
2046 Span::new(pos, pos, item.span.data().ctxt)
2049 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2050 ctr_vis.visit_body(body);
2057 "parameter of type `{}` should be generalized over different hashers",
2061 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2072 enum ImplicitHasherType<'tcx> {
2073 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2074 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2077 impl<'tcx> ImplicitHasherType<'tcx> {
2078 /// Checks that `ty` is a target type without a BuildHasher.
2079 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2080 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2081 let params: Vec<_> = path
2089 .filter_map(|arg| match arg {
2090 GenericArg::Type(ty) => Some(ty),
2091 GenericArg::Lifetime(_) => None,
2094 let params_len = params.len();
2096 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2098 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2099 Some(ImplicitHasherType::HashMap(
2102 snippet(cx, params[0].span, "K"),
2103 snippet(cx, params[1].span, "V"),
2105 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2106 Some(ImplicitHasherType::HashSet(
2109 snippet(cx, params[0].span, "T"),
2119 fn type_name(&self) -> &'static str {
2121 ImplicitHasherType::HashMap(..) => "HashMap",
2122 ImplicitHasherType::HashSet(..) => "HashSet",
2126 fn type_arguments(&self) -> String {
2128 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2129 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2133 fn ty(&self) -> Ty<'tcx> {
2135 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2139 fn span(&self) -> Span {
2141 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2146 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2147 cx: &'a LateContext<'a, 'tcx>,
2148 found: Vec<ImplicitHasherType<'tcx>>,
2151 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2152 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2153 Self { cx, found: vec![] }
2157 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2158 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2159 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2160 self.found.push(target);
2166 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2167 NestedVisitorMap::None
2171 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2172 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2173 cx: &'a LateContext<'a, 'tcx>,
2174 body: &'a TypeckTables<'tcx>,
2175 target: &'b ImplicitHasherType<'tcx>,
2176 suggestions: BTreeMap<Span, String>,
2179 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2180 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2185 suggestions: BTreeMap::new(),
2190 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2191 fn visit_body(&mut self, body: &'tcx Body) {
2192 self.body = self.cx.tcx.body_tables(body.id());
2193 walk_body(self, body);
2196 fn visit_expr(&mut self, e: &'tcx Expr) {
2198 if let ExprKind::Call(ref fun, ref args) = e.node;
2199 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2200 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2202 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2206 if match_path(ty_path, &paths::HASHMAP) {
2207 if method.ident.name == "new" {
2209 .insert(e.span, "HashMap::default()".to_string());
2210 } else if method.ident.name == "with_capacity" {
2211 self.suggestions.insert(
2214 "HashMap::with_capacity_and_hasher({}, Default::default())",
2215 snippet(self.cx, args[0].span, "capacity"),
2219 } else if match_path(ty_path, &paths::HASHSET) {
2220 if method.ident.name == "new" {
2222 .insert(e.span, "HashSet::default()".to_string());
2223 } else if method.ident.name == "with_capacity" {
2224 self.suggestions.insert(
2227 "HashSet::with_capacity_and_hasher({}, Default::default())",
2228 snippet(self.cx, args[0].span, "capacity"),
2239 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2240 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())