1 #![allow(clippy::default_hash_types)]
3 use crate::reexport::*;
5 use crate::rustc::hir::*;
6 use crate::rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
7 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass, in_external_macro, LintContext};
8 use crate::rustc::{declare_tool_lint, lint_array};
9 use if_chain::if_chain;
10 use crate::rustc::ty::{self, Ty, TyCtxt, TypeckTables};
11 use crate::rustc::ty::layout::LayoutOf;
12 use crate::rustc_typeck::hir_ty_to_ty;
13 use std::cmp::Ordering;
14 use std::collections::BTreeMap;
16 use crate::syntax::ast::{FloatTy, IntTy, UintTy};
17 use crate::syntax::source_map::Span;
18 use crate::syntax::errors::DiagnosticBuilder;
19 use crate::utils::{comparisons, differing_macro_contexts, higher, in_constant, in_macro, last_path_segment, match_def_path, match_path,
20 match_type, multispan_sugg, opt_def_id, same_tys, snippet, snippet_opt, span_help_and_lint, span_lint,
21 span_lint_and_sugg, span_lint_and_then, clip, unsext, sext, int_bits};
22 use crate::utils::paths;
23 use crate::consts::{constant, Constant};
25 /// Handles all the linting of funky types
26 #[allow(missing_copy_implementations)]
29 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
31 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
32 /// the heap. So if you `Box` it, you just add another level of indirection
33 /// without any benefit whatsoever.
35 /// **Known problems:** None.
40 /// values: Box<Vec<Foo>>,
51 declare_clippy_lint! {
54 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
57 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
60 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
61 /// represents an optional optional value which is logically the same thing as an optional
62 /// value but has an unneeded extra level of wrapping.
64 /// **Known problems:** None.
68 /// fn x() -> Option<Option<u32>> {
71 declare_clippy_lint! {
74 "usage of `Option<Option<T>>`"
77 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
78 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
80 /// **Why is this bad?** Gankro says:
82 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
83 /// pointers and indirection.
84 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
86 /// > "only" amortized for push/pop, should be faster in the general case for
87 /// almost every possible
88 /// > workload, and isn't even amortized at all if you can predict the capacity
91 /// > `LinkedList`s are only really good if you're doing a lot of merging or
92 /// splitting of lists.
93 /// > This is because they can just mangle some pointers instead of actually
94 /// copying the data. Even
95 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
96 /// can still be better
97 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
99 /// **Known problems:** False positives – the instances where using a
100 /// `LinkedList` makes sense are few and far between, but they can still happen.
104 /// let x = LinkedList::new();
106 declare_clippy_lint! {
109 "usage of LinkedList, usually a vector is faster, or a more specialized data \
110 structure like a VecDeque"
113 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
115 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
118 /// **Known problems:** None.
122 /// fn foo(bar: &Box<T>) { ... }
128 /// fn foo(bar: &T) { ... }
130 declare_clippy_lint! {
133 "a borrow of a boxed type"
136 impl LintPass for TypePass {
137 fn get_lints(&self) -> LintArray {
138 lint_array!(BOX_VEC, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
142 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
143 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
144 // skip trait implementations, see #605
145 if let Some(hir::Node::Item(item)) = cx.tcx.hir.find(cx.tcx.hir.get_parent(id)) {
146 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
151 check_fn_decl(cx, decl);
154 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
155 check_ty(cx, &field.ty, false);
158 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
160 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
161 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
166 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
167 if let Some(ref ty) = local.ty {
168 check_ty(cx, ty, true);
173 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
174 for input in &decl.inputs {
175 check_ty(cx, input, false);
178 if let FunctionRetTy::Return(ref ty) = decl.output {
179 check_ty(cx, ty, false);
183 /// Check if `qpath` has last segment with type parameter matching `path`
184 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
185 let last = last_path_segment(qpath);
187 if let Some(ref params) = last.args;
188 if !params.parenthesized;
189 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
190 GenericArg::Type(ty) => Some(ty),
191 GenericArg::Lifetime(_) => None,
193 if let TyKind::Path(ref qpath) = ty.node;
194 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir.node_to_hir_id(ty.id)));
195 if match_def_path(cx.tcx, did, path);
203 /// Recursively check for `TypePass` lints in the given type. Stop at the first
206 /// The parameter `is_local` distinguishes the context of the type; types from
207 /// local bindings should only be checked for the `BORROWED_BOX` lint.
208 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
209 if in_macro(ast_ty.span) {
213 TyKind::Path(ref qpath) if !is_local => {
214 let hir_id = cx.tcx.hir.node_to_hir_id(ast_ty.id);
215 let def = cx.tables.qpath_def(qpath, hir_id);
216 if let Some(def_id) = opt_def_id(def) {
217 if Some(def_id) == cx.tcx.lang_items().owned_box() {
218 if match_type_parameter(cx, qpath, &paths::VEC) {
223 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
224 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
226 return; // don't recurse into the type
228 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
229 if match_type_parameter(cx, qpath, &paths::OPTION) {
234 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
235 enum if you need to distinguish all 3 cases",
237 return; // don't recurse into the type
239 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
244 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
245 "a VecDeque might work",
247 return; // don't recurse into the type
251 QPath::Resolved(Some(ref ty), ref p) => {
252 check_ty(cx, ty, is_local);
253 for ty in p.segments.iter().flat_map(|seg| {
256 .map_or_else(|| [].iter(), |params| params.args.iter())
257 .filter_map(|arg| match arg {
258 GenericArg::Type(ty) => Some(ty),
259 GenericArg::Lifetime(_) => None,
262 check_ty(cx, ty, is_local);
265 QPath::Resolved(None, ref p) => for ty in p.segments.iter().flat_map(|seg| {
268 .map_or_else(|| [].iter(), |params| params.args.iter())
269 .filter_map(|arg| match arg {
270 GenericArg::Type(ty) => Some(ty),
271 GenericArg::Lifetime(_) => None,
274 check_ty(cx, ty, is_local);
276 QPath::TypeRelative(ref ty, ref seg) => {
277 check_ty(cx, ty, is_local);
278 if let Some(ref params) = seg.args {
279 for ty in params.args.iter().filter_map(|arg| match arg {
280 GenericArg::Type(ty) => Some(ty),
281 GenericArg::Lifetime(_) => None,
283 check_ty(cx, ty, is_local);
289 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
291 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => check_ty(cx, ty, is_local),
292 TyKind::Tup(ref tys) => for ty in tys {
293 check_ty(cx, ty, is_local);
299 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
300 match mut_ty.ty.node {
301 TyKind::Path(ref qpath) => {
302 let hir_id = cx.tcx.hir.node_to_hir_id(mut_ty.ty.id);
303 let def = cx.tables.qpath_def(qpath, hir_id);
305 if let Some(def_id) = opt_def_id(def);
306 if Some(def_id) == cx.tcx.lang_items().owned_box();
307 if let QPath::Resolved(None, ref path) = *qpath;
308 if let [ref bx] = *path.segments;
309 if let Some(ref params) = bx.args;
310 if !params.parenthesized;
311 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
312 GenericArg::Type(ty) => Some(ty),
313 GenericArg::Lifetime(_) => None,
316 if is_any_trait(inner) {
317 // Ignore `Box<Any>` types, see #1884 for details.
321 let ltopt = if lt.is_elided() {
324 format!("{} ", lt.name.ident().name.as_str())
326 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
331 span_lint_and_sugg(cx,
334 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
336 format!("&{}{}{}", ltopt, mutopt, &snippet(cx, inner.span, ".."))
338 return; // don't recurse into the type
341 check_ty(cx, &mut_ty.ty, is_local);
343 _ => check_ty(cx, &mut_ty.ty, is_local),
347 // Returns true if given type is `Any` trait.
348 fn is_any_trait(t: &hir::Ty) -> bool {
350 if let TyKind::TraitObject(ref traits, _) = t.node;
351 if traits.len() >= 1;
352 // Only Send/Sync can be used as additional traits, so it is enough to
353 // check only the first trait.
354 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
363 #[allow(missing_copy_implementations)]
366 /// **What it does:** Checks for binding a unit value.
368 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
369 /// binding one is kind of pointless.
371 /// **Known problems:** None.
377 declare_clippy_lint! {
380 "creating a let binding to a value of unit type, which usually can't be used afterwards"
383 fn check_let_unit(cx: &LateContext<'_, '_>, decl: &Decl) {
384 if let DeclKind::Local(ref local) = decl.node {
385 if is_unit(cx.tables.pat_ty(&local.pat)) {
386 if in_external_macro(cx.sess(), decl.span) || in_macro(local.pat.span) {
389 if higher::is_from_for_desugar(decl) {
397 "this let-binding has unit value. Consider omitting `let {} =`",
398 snippet(cx, local.pat.span, "..")
405 impl LintPass for LetPass {
406 fn get_lints(&self) -> LintArray {
407 lint_array!(LET_UNIT_VALUE)
411 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
412 fn check_decl(&mut self, cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl) {
413 check_let_unit(cx, decl)
417 /// **What it does:** Checks for comparisons to unit.
419 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
420 /// clumsily written constant. Mostly this happens when someone accidentally
421 /// adds semicolons at the end of the operands.
423 /// **Known problems:** None.
427 /// if { foo(); } == { bar(); } { baz(); }
431 /// { foo(); bar(); baz(); }
433 declare_clippy_lint! {
436 "comparing unit values"
439 #[allow(missing_copy_implementations)]
442 impl LintPass for UnitCmp {
443 fn get_lints(&self) -> LintArray {
444 lint_array!(UNIT_CMP)
448 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
449 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
450 if in_macro(expr.span) {
453 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
455 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
456 let result = match op {
457 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
465 "{}-comparison of unit values detected. This will always be {}",
475 /// **What it does:** Checks for passing a unit value as an argument to a function without using a unit literal (`()`).
477 /// **Why is this bad?** This is likely the result of an accidental semicolon.
479 /// **Known problems:** None.
488 declare_clippy_lint! {
491 "passing unit to a function"
496 impl LintPass for UnitArg {
497 fn get_lints(&self) -> LintArray {
498 lint_array!(UNIT_ARG)
502 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
503 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
504 if in_macro(expr.span) {
508 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
510 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
511 let map = &cx.tcx.hir;
512 // apparently stuff in the desugaring of `?` can trigger this
513 // so check for that here
514 // only the calls to `Try::from_error` is marked as desugared,
515 // so we need to check both the current Expr and its parent.
516 if !is_questionmark_desugar_marked_call(expr) {
518 let opt_parent_node = map.find(map.get_parent_node(expr.id));
519 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
520 if is_questionmark_desugar_marked_call(parent_expr);
523 // `expr` and `parent_expr` where _both_ not from
524 // desugaring `?`, so lint
529 "passing a unit value to a function",
530 "if you intended to pass a unit value, use a unit literal instead",
544 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
545 use crate::syntax_pos::hygiene::CompilerDesugaringKind;
546 if let ExprKind::Call(ref callee, _) = expr.node {
547 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
553 fn is_unit(ty: Ty<'_>) -> bool {
555 ty::Tuple(slice) if slice.is_empty() => true,
560 fn is_unit_literal(expr: &Expr) -> bool {
562 ExprKind::Tup(ref slice) if slice.is_empty() => true,
569 /// **What it does:** Checks for casts from any numerical to a float type where
570 /// the receiving type cannot store all values from the original type without
571 /// rounding errors. This possible rounding is to be expected, so this lint is
572 /// `Allow` by default.
574 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
575 /// or any 64-bit integer to `f64`.
577 /// **Why is this bad?** It's not bad at all. But in some applications it can be
578 /// helpful to know where precision loss can take place. This lint can help find
579 /// those places in the code.
581 /// **Known problems:** None.
585 /// let x = u64::MAX; x as f64
587 declare_clippy_lint! {
588 pub CAST_PRECISION_LOSS,
590 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
593 /// **What it does:** Checks for casts from a signed to an unsigned numerical
594 /// type. In this case, negative values wrap around to large positive values,
595 /// which can be quite surprising in practice. However, as the cast works as
596 /// defined, this lint is `Allow` by default.
598 /// **Why is this bad?** Possibly surprising results. You can activate this lint
599 /// as a one-time check to see where numerical wrapping can arise.
601 /// **Known problems:** None.
606 /// y as u128 // will return 18446744073709551615
608 declare_clippy_lint! {
611 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
614 /// **What it does:** Checks for on casts between numerical types that may
615 /// truncate large values. This is expected behavior, so the cast is `Allow` by
618 /// **Why is this bad?** In some problem domains, it is good practice to avoid
619 /// truncation. This lint can be activated to help assess where additional
620 /// checks could be beneficial.
622 /// **Known problems:** None.
626 /// fn as_u8(x: u64) -> u8 { x as u8 }
628 declare_clippy_lint! {
629 pub CAST_POSSIBLE_TRUNCATION,
631 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, \
632 or `x as i32` where `x: f32`"
635 /// **What it does:** Checks for casts from an unsigned type to a signed type of
636 /// the same size. Performing such a cast is a 'no-op' for the compiler,
637 /// i.e. nothing is changed at the bit level, and the binary representation of
638 /// the value is reinterpreted. This can cause wrapping if the value is too big
639 /// for the target signed type. However, the cast works as defined, so this lint
640 /// is `Allow` by default.
642 /// **Why is this bad?** While such a cast is not bad in itself, the results can
643 /// be surprising when this is not the intended behavior, as demonstrated by the
646 /// **Known problems:** None.
650 /// u32::MAX as i32 // will yield a value of `-1`
652 declare_clippy_lint! {
653 pub CAST_POSSIBLE_WRAP,
655 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` \
659 /// **What it does:** Checks for on casts between numerical types that may
660 /// be replaced by safe conversion functions.
662 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
663 /// conversions, including silently lossy conversions. Conversion functions such
664 /// as `i32::from` will only perform lossless conversions. Using the conversion
665 /// functions prevents conversions from turning into silent lossy conversions if
666 /// the types of the input expressions ever change, and make it easier for
667 /// people reading the code to know that the conversion is lossless.
669 /// **Known problems:** None.
673 /// fn as_u64(x: u8) -> u64 { x as u64 }
676 /// Using `::from` would look like this:
679 /// fn as_u64(x: u8) -> u64 { u64::from(x) }
681 declare_clippy_lint! {
684 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
687 /// **What it does:** Checks for casts to the same type.
689 /// **Why is this bad?** It's just unnecessary.
691 /// **Known problems:** None.
695 /// let _ = 2i32 as i32
697 declare_clippy_lint! {
698 pub UNNECESSARY_CAST,
700 "cast to the same type, e.g. `x as i32` where `x: i32`"
703 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
704 /// more-strictly-aligned pointer
706 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
709 /// **Known problems:** None.
713 /// let _ = (&1u8 as *const u8) as *const u16;
714 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
716 declare_clippy_lint! {
717 pub CAST_PTR_ALIGNMENT,
719 "cast from a pointer to a more-strictly-aligned pointer"
722 /// **What it does:** Checks for casts of function pointers to something other than usize
724 /// **Why is this bad?**
725 /// Casting a function pointer to anything other than usize/isize is not portable across
726 /// architectures, because you end up losing bits if the target type is too small or end up with a
727 /// bunch of extra bits that waste space and add more instructions to the final binary than
728 /// strictly necessary for the problem
730 /// Casting to isize also doesn't make sense since there are no signed addresses.
736 /// fn fun() -> i32 {}
737 /// let a = fun as i64;
740 /// fn fun2() -> i32 {}
741 /// let a = fun2 as usize;
743 declare_clippy_lint! {
744 pub FN_TO_NUMERIC_CAST,
746 "casting a function pointer to a numeric type other than usize"
749 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
752 /// **Why is this bad?**
753 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
754 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
755 /// a comment) to perform the truncation.
761 /// fn fn1() -> i16 { 1 };
762 /// let _ = fn1 as i32;
764 /// // Better: Cast to usize first, then comment with the reason for the truncation
765 /// fn fn2() -> i16 { 1 };
766 /// let fn_ptr = fn2 as usize;
767 /// let fn_ptr_truncated = fn_ptr as i32;
769 declare_clippy_lint! {
770 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
772 "casting a function pointer to a numeric type not wide enough to store the address"
775 /// Returns the size in bits of an integral type.
776 /// Will return 0 if the type is not an int or uint variant
777 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
779 ty::Int(i) => match i {
780 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
787 ty::Uint(i) => match i {
788 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
799 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
801 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
806 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
807 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
808 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
809 let arch_dependent_str = "on targets with 64-bit wide pointers ";
810 let from_nbits_str = if arch_dependent {
812 } else if is_isize_or_usize(cast_from) {
813 "32 or 64".to_owned()
815 int_ty_to_nbits(cast_from, cx.tcx).to_string()
822 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
823 is only {4} bits wide)",
825 if cast_to_f64 { "f64" } else { "f32" },
837 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
838 if let ExprKind::Binary(_, _, _) = op.node {
839 if snip.starts_with('(') && snip.ends_with(')') {
846 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
847 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
848 if in_constant(cx, expr.id) { return }
849 // The suggestion is to use a function call, so if the original expression
850 // has parens on the outside, they are no longer needed.
851 let opt = snippet_opt(cx, op.span);
852 let sugg = if let Some(ref snip) = opt {
853 if should_strip_parens(op, snip) {
854 &snip[1..snip.len() - 1]
866 &format!("casting {} to {} may become silently lossy if types change", cast_from, cast_to),
868 format!("{}::from({})", cast_to, sugg),
878 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
879 let arch_64_suffix = " on targets with 64-bit wide pointers";
880 let arch_32_suffix = " on targets with 32-bit wide pointers";
881 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
882 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
883 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
884 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
885 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
886 (true, true) | (false, false) => (
887 to_nbits < from_nbits,
889 to_nbits == from_nbits && cast_unsigned_to_signed,
899 to_nbits <= 32 && cast_unsigned_to_signed,
905 cast_unsigned_to_signed,
906 if from_nbits == 64 {
916 CAST_POSSIBLE_TRUNCATION,
919 "casting {} to {} may truncate the value{}",
922 match suffix_truncation {
923 ArchSuffix::_32 => arch_32_suffix,
924 ArchSuffix::_64 => arch_64_suffix,
925 ArchSuffix::None => "",
936 "casting {} to {} may wrap around the value{}",
940 ArchSuffix::_32 => arch_32_suffix,
941 ArchSuffix::_64 => arch_64_suffix,
942 ArchSuffix::None => "",
949 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
950 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
951 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
952 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
953 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
955 span_lossless_lint(cx, expr, op, cast_from, cast_to);
959 impl LintPass for CastPass {
960 fn get_lints(&self) -> LintArray {
964 CAST_POSSIBLE_TRUNCATION,
974 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
975 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
976 if let ExprKind::Cast(ref ex, _) = expr.node {
977 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
978 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
979 if let ExprKind::Lit(ref lit) = ex.node {
980 use crate::syntax::ast::{LitIntType, LitKind};
982 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
983 _ => if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
988 &format!("casting to the same type is unnecessary (`{}` -> `{}`)", cast_from, cast_to),
993 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
994 match (cast_from.is_integral(), cast_to.is_integral()) {
996 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
997 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1002 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1003 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1005 if from_nbits < to_nbits {
1006 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1012 CAST_POSSIBLE_TRUNCATION,
1014 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1016 if !cast_to.is_signed() {
1021 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1026 if cast_from.is_signed() && !cast_to.is_signed() {
1031 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1034 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1035 check_lossless(cx, expr, ex, cast_from, cast_to);
1038 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty)
1042 CAST_POSSIBLE_TRUNCATION,
1044 "casting f64 to f32 may truncate the value",
1047 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty)
1049 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1056 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1057 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1058 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi());
1059 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi());
1060 if from_align < to_align;
1061 // with c_void, we inherently need to trust the user
1063 match_type(cx, from_ptr_ty.ty, &paths::C_VOID)
1064 || match_type(cx, from_ptr_ty.ty, &paths::C_VOID_LIBC)
1071 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1079 fn lint_fn_to_numeric_cast(cx: &LateContext<'_, '_>, expr: &Expr, cast_expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1080 match cast_from.sty {
1081 ty::FnDef(..) | ty::FnPtr(_) => {
1082 let from_snippet = snippet(cx, cast_expr.span, "x");
1084 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1085 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1088 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1090 &format!("casting function pointer `{}` to `{}`, which truncates the value", from_snippet, cast_to),
1092 format!("{} as usize", from_snippet)
1095 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1100 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1102 format!("{} as usize", from_snippet)
1110 /// **What it does:** Checks for types used in structs, parameters and `let`
1111 /// declarations above a certain complexity threshold.
1113 /// **Why is this bad?** Too complex types make the code less readable. Consider
1114 /// using a `type` definition to simplify them.
1116 /// **Known problems:** None.
1120 /// struct Foo { inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>> }
1122 declare_clippy_lint! {
1123 pub TYPE_COMPLEXITY,
1125 "usage of very complex types that might be better factored into `type` definitions"
1128 #[allow(missing_copy_implementations)]
1129 pub struct TypeComplexityPass {
1133 impl TypeComplexityPass {
1134 pub fn new(threshold: u64) -> Self {
1141 impl LintPass for TypeComplexityPass {
1142 fn get_lints(&self) -> LintArray {
1143 lint_array!(TYPE_COMPLEXITY)
1147 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1150 cx: &LateContext<'a, 'tcx>,
1157 self.check_fndecl(cx, decl);
1160 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1161 // enum variants are also struct fields now
1162 self.check_type(cx, &field.ty);
1165 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1167 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1168 // functions, enums, structs, impls and traits are covered
1173 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1175 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1176 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1177 // methods with default impl are covered by check_fn
1182 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1184 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1185 // methods are covered by check_fn
1190 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1191 if let Some(ref ty) = local.ty {
1192 self.check_type(cx, ty);
1197 impl<'a, 'tcx> TypeComplexityPass {
1198 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1199 for arg in &decl.inputs {
1200 self.check_type(cx, arg);
1202 if let Return(ref ty) = decl.output {
1203 self.check_type(cx, ty);
1207 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1208 if in_macro(ty.span) {
1212 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1213 visitor.visit_ty(ty);
1217 if score > self.threshold {
1222 "very complex type used. Consider factoring parts into `type` definitions",
1228 /// Walks a type and assigns a complexity score to it.
1229 struct TypeComplexityVisitor {
1230 /// total complexity score of the type
1232 /// current nesting level
1236 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1237 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1238 let (add_score, sub_nest) = match ty.node {
1239 // _, &x and *x have only small overhead; don't mess with nesting level
1240 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1242 // the "normal" components of a type: named types, arrays/tuples
1243 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1245 // function types bring a lot of overhead
1246 TyKind::BareFn(..) => (50 * self.nest, 1),
1248 TyKind::TraitObject(ref param_bounds, _) => {
1249 let has_lifetime_parameters = param_bounds
1251 .any(|bound| bound.bound_generic_params.iter().any(|gen| match gen.kind {
1252 GenericParamKind::Lifetime { .. } => true,
1255 if has_lifetime_parameters {
1256 // complex trait bounds like A<'a, 'b>
1259 // simple trait bounds like A + B
1266 self.score += add_score;
1267 self.nest += sub_nest;
1269 self.nest -= sub_nest;
1271 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1272 NestedVisitorMap::None
1276 /// **What it does:** Checks for expressions where a character literal is cast
1277 /// to `u8` and suggests using a byte literal instead.
1279 /// **Why is this bad?** In general, casting values to smaller types is
1280 /// error-prone and should be avoided where possible. In the particular case of
1281 /// converting a character literal to u8, it is easy to avoid by just using a
1282 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1283 /// than `'a' as u8`.
1285 /// **Known problems:** None.
1292 /// A better version, using the byte literal:
1297 declare_clippy_lint! {
1300 "casting a character literal to u8"
1303 pub struct CharLitAsU8;
1305 impl LintPass for CharLitAsU8 {
1306 fn get_lints(&self) -> LintArray {
1307 lint_array!(CHAR_LIT_AS_U8)
1311 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1312 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1313 use crate::syntax::ast::{LitKind, UintTy};
1315 if let ExprKind::Cast(ref e, _) = expr.node {
1316 if let ExprKind::Lit(ref l) = e.node {
1317 if let LitKind::Char(_) = l.node {
1318 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1319 let msg = "casting character literal to u8. `char`s \
1320 are 4 bytes wide in rust, so casting to u8 \
1322 let help = format!("Consider using a byte literal instead:\nb{}", snippet(cx, e.span, "'x'"));
1323 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1331 /// **What it does:** Checks for comparisons where one side of the relation is
1332 /// either the minimum or maximum value for its type and warns if it involves a
1333 /// case that is always true or always false. Only integer and boolean types are
1336 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1337 /// that is is possible for `x` to be less than the minimum. Expressions like
1338 /// `max < x` are probably mistakes.
1340 /// **Known problems:** For `usize` the size of the current compile target will
1341 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1342 /// a comparison to detect target pointer width will trigger this lint. One can
1343 /// use `mem::sizeof` and compare its value or conditional compilation
1345 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1350 /// 100 > std::i32::MAX
1352 declare_clippy_lint! {
1353 pub ABSURD_EXTREME_COMPARISONS,
1355 "a comparison with a maximum or minimum value that is always true or false"
1358 pub struct AbsurdExtremeComparisons;
1360 impl LintPass for AbsurdExtremeComparisons {
1361 fn get_lints(&self) -> LintArray {
1362 lint_array!(ABSURD_EXTREME_COMPARISONS)
1371 struct ExtremeExpr<'a> {
1376 enum AbsurdComparisonResult {
1379 InequalityImpossible,
1383 fn is_cast_between_fixed_and_target<'a, 'tcx>(
1384 cx: &LateContext<'a, 'tcx>,
1388 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1389 let precast_ty = cx.tables.expr_ty(cast_exp);
1390 let cast_ty = cx.tables.expr_ty(expr);
1392 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty)
1398 fn detect_absurd_comparison<'a, 'tcx>(
1399 cx: &LateContext<'a, 'tcx>,
1403 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1404 use crate::types::ExtremeType::*;
1405 use crate::types::AbsurdComparisonResult::*;
1406 use crate::utils::comparisons::*;
1408 // absurd comparison only makes sense on primitive types
1409 // primitive types don't implement comparison operators with each other
1410 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1414 // comparisons between fix sized types and target sized types are considered unanalyzable
1415 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1419 let normalized = normalize_comparison(op, lhs, rhs);
1420 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1426 let lx = detect_extreme_expr(cx, normalized_lhs);
1427 let rx = detect_extreme_expr(cx, normalized_rhs);
1432 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1433 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1439 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1440 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1441 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1442 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1446 Rel::Ne | Rel::Eq => return None,
1450 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1451 use crate::types::ExtremeType::*;
1453 let ty = cx.tables.expr_ty(expr);
1455 let cv = constant(cx, cx.tables, expr)?.0;
1457 let which = match (&ty.sty, cv) {
1458 (&ty::Bool, Constant::Bool(false)) |
1459 (&ty::Uint(_), Constant::Int(0)) => Minimum,
1460 (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) => Minimum,
1462 (&ty::Bool, Constant::Bool(true)) => Maximum,
1463 (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) => Maximum,
1464 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1474 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1475 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1476 use crate::types::ExtremeType::*;
1477 use crate::types::AbsurdComparisonResult::*;
1479 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1480 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1481 if !in_macro(expr.span) {
1482 let msg = "this comparison involving the minimum or maximum element for this \
1483 type contains a case that is always true or always false";
1485 let conclusion = match result {
1486 AlwaysFalse => "this comparison is always false".to_owned(),
1487 AlwaysTrue => "this comparison is always true".to_owned(),
1488 InequalityImpossible => format!(
1489 "the case where the two sides are not equal never occurs, consider using {} == {} \
1491 snippet(cx, lhs.span, "lhs"),
1492 snippet(cx, rhs.span, "rhs")
1497 "because {} is the {} value for this type, {}",
1498 snippet(cx, culprit.expr.span, "x"),
1499 match culprit.which {
1500 Minimum => "minimum",
1501 Maximum => "maximum",
1506 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1513 /// **What it does:** Checks for comparisons where the relation is always either
1514 /// true or false, but where one side has been upcast so that the comparison is
1515 /// necessary. Only integer types are checked.
1517 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1518 /// will mistakenly imply that it is possible for `x` to be outside the range of
1521 /// **Known problems:**
1522 /// https://github.com/rust-lang-nursery/rust-clippy/issues/886
1526 /// let x : u8 = ...; (x as u32) > 300
1528 declare_clippy_lint! {
1529 pub INVALID_UPCAST_COMPARISONS,
1531 "a comparison involving an upcast which is always true or false"
1534 pub struct InvalidUpcastComparisons;
1536 impl LintPass for InvalidUpcastComparisons {
1537 fn get_lints(&self) -> LintArray {
1538 lint_array!(INVALID_UPCAST_COMPARISONS)
1542 #[derive(Copy, Clone, Debug, Eq)]
1549 #[allow(clippy::cast_sign_loss)]
1550 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1553 } else if u > (i128::max_value() as u128) {
1561 impl PartialEq for FullInt {
1562 fn eq(&self, other: &Self) -> bool {
1563 self.partial_cmp(other)
1564 .expect("partial_cmp only returns Some(_)") == Ordering::Equal
1568 impl PartialOrd for FullInt {
1569 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1570 Some(match (self, other) {
1571 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1572 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1573 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1574 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1578 impl Ord for FullInt {
1579 fn cmp(&self, other: &Self) -> Ordering {
1580 self.partial_cmp(other)
1581 .expect("partial_cmp for FullInt can never return None")
1586 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1587 use crate::syntax::ast::{IntTy, UintTy};
1590 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1591 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1592 let cast_ty = cx.tables.expr_ty(expr);
1593 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1594 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1597 match pre_cast_ty.sty {
1598 ty::Int(int_ty) => Some(match int_ty {
1599 IntTy::I8 => (FullInt::S(i128::from(i8::min_value())), FullInt::S(i128::from(i8::max_value()))),
1601 FullInt::S(i128::from(i16::min_value())),
1602 FullInt::S(i128::from(i16::max_value())),
1605 FullInt::S(i128::from(i32::min_value())),
1606 FullInt::S(i128::from(i32::max_value())),
1609 FullInt::S(i128::from(i64::min_value())),
1610 FullInt::S(i128::from(i64::max_value())),
1612 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1613 IntTy::Isize => (FullInt::S(isize::min_value() as i128), FullInt::S(isize::max_value() as i128)),
1615 ty::Uint(uint_ty) => Some(match uint_ty {
1616 UintTy::U8 => (FullInt::U(u128::from(u8::min_value())), FullInt::U(u128::from(u8::max_value()))),
1618 FullInt::U(u128::from(u16::min_value())),
1619 FullInt::U(u128::from(u16::max_value())),
1622 FullInt::U(u128::from(u32::min_value())),
1623 FullInt::U(u128::from(u32::max_value())),
1626 FullInt::U(u128::from(u64::min_value())),
1627 FullInt::U(u128::from(u64::max_value())),
1629 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1630 UintTy::Usize => (FullInt::U(usize::min_value() as u128), FullInt::U(usize::max_value() as u128)),
1639 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1640 let val = constant(cx, cx.tables, expr)?.0;
1641 if let Constant::Int(const_int) = val {
1642 match cx.tables.expr_ty(expr).sty {
1643 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1644 ty::Uint(_) => Some(FullInt::U(const_int)),
1652 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1653 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1656 INVALID_UPCAST_COMPARISONS,
1659 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1660 snippet(cx, cast_val.span, "the expression"),
1661 if always { "true" } else { "false" },
1667 fn upcast_comparison_bounds_err<'a, 'tcx>(
1668 cx: &LateContext<'a, 'tcx>,
1670 rel: comparisons::Rel,
1671 lhs_bounds: Option<(FullInt, FullInt)>,
1676 use crate::utils::comparisons::*;
1678 if let Some((lb, ub)) = lhs_bounds {
1679 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1680 if rel == Rel::Eq || rel == Rel::Ne {
1681 if norm_rhs_val < lb || norm_rhs_val > ub {
1682 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1684 } else if match rel {
1685 Rel::Lt => if invert {
1690 Rel::Le => if invert {
1695 Rel::Eq | Rel::Ne => unreachable!(),
1697 err_upcast_comparison(cx, span, lhs, true)
1698 } else if match rel {
1699 Rel::Lt => if invert {
1704 Rel::Le => if invert {
1709 Rel::Eq | Rel::Ne => unreachable!(),
1711 err_upcast_comparison(cx, span, lhs, false)
1717 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1718 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1719 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1720 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1721 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1727 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1728 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1730 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1731 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1736 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1737 /// over different hashers and implicitly defaulting to the default hashing
1738 /// algorithm (SipHash).
1740 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1743 /// **Known problems:** Suggestions for replacing constructors can contain
1744 /// false-positives. Also applying suggestions can require modification of other
1745 /// pieces of code, possibly including external crates.
1749 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1751 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1753 declare_clippy_lint! {
1754 pub IMPLICIT_HASHER,
1756 "missing generalization over different hashers"
1759 pub struct ImplicitHasher;
1761 impl LintPass for ImplicitHasher {
1762 fn get_lints(&self) -> LintArray {
1763 lint_array!(IMPLICIT_HASHER)
1767 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1768 #[allow(clippy::cast_possible_truncation)]
1769 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1770 use crate::syntax_pos::BytePos;
1772 fn suggestion<'a, 'tcx>(
1773 cx: &LateContext<'a, 'tcx>,
1774 db: &mut DiagnosticBuilder<'_>,
1775 generics_span: Span,
1776 generics_suggestion_span: Span,
1777 target: &ImplicitHasherType<'_>,
1778 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1780 let generics_snip = snippet(cx, generics_span, "");
1782 let generics_snip = if generics_snip.is_empty() {
1785 &generics_snip[1..generics_snip.len() - 1]
1790 "consider adding a type parameter".to_string(),
1793 generics_suggestion_span,
1795 "<{}{}S: ::std::hash::BuildHasher{}>",
1797 if generics_snip.is_empty() { "" } else { ", " },
1798 if vis.suggestions.is_empty() {
1801 // request users to add `Default` bound so that generic constructors can be used
1808 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
1813 if !vis.suggestions.is_empty() {
1814 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
1818 if !cx.access_levels.is_exported(item.id) {
1823 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
1824 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1827 for target in &vis.found {
1828 if differing_macro_contexts(item.span, target.span()) {
1832 let generics_suggestion_span = generics.span.substitute_dummy({
1833 let pos = snippet_opt(cx, item.span.until(target.span()))
1834 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
1835 if let Some(pos) = pos {
1836 Span::new(pos, pos, item.span.data().ctxt)
1842 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1843 for item in items.iter().map(|item| cx.tcx.hir.impl_item(item.id)) {
1844 ctr_vis.visit_impl_item(item);
1851 &format!("impl for `{}` should be generalized over different hashers", target.type_name()),
1853 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1858 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
1859 let body = cx.tcx.hir.body(body_id);
1861 for ty in &decl.inputs {
1862 let mut vis = ImplicitHasherTypeVisitor::new(cx);
1865 for target in &vis.found {
1866 let generics_suggestion_span = generics.span.substitute_dummy({
1867 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
1869 let i = snip.find("fn")?;
1870 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
1872 .expect("failed to create span for type parameters");
1873 Span::new(pos, pos, item.span.data().ctxt)
1876 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
1877 ctr_vis.visit_body(body);
1884 "parameter of type `{}` should be generalized over different hashers",
1888 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
1899 enum ImplicitHasherType<'tcx> {
1900 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
1901 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
1904 impl<'tcx> ImplicitHasherType<'tcx> {
1905 /// Checks that `ty` is a target type without a BuildHasher.
1906 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
1907 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
1908 let params: Vec<_> = path.segments.last().as_ref()?.args.as_ref()?
1909 .args.iter().filter_map(|arg| match arg {
1910 GenericArg::Type(ty) => Some(ty),
1911 GenericArg::Lifetime(_) => None,
1913 let params_len = params.len();
1915 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
1917 if match_path(path, &paths::HASHMAP) && params_len == 2 {
1918 Some(ImplicitHasherType::HashMap(
1921 snippet(cx, params[0].span, "K"),
1922 snippet(cx, params[1].span, "V"),
1924 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
1925 Some(ImplicitHasherType::HashSet(hir_ty.span, ty, snippet(cx, params[0].span, "T")))
1934 fn type_name(&self) -> &'static str {
1936 ImplicitHasherType::HashMap(..) => "HashMap",
1937 ImplicitHasherType::HashSet(..) => "HashSet",
1941 fn type_arguments(&self) -> String {
1943 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
1944 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
1948 fn ty(&self) -> Ty<'tcx> {
1950 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
1954 fn span(&self) -> Span {
1956 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
1961 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
1962 cx: &'a LateContext<'a, 'tcx>,
1963 found: Vec<ImplicitHasherType<'tcx>>,
1966 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
1967 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
1968 Self { cx, found: vec![] }
1972 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
1973 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
1974 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
1975 self.found.push(target);
1981 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1982 NestedVisitorMap::None
1986 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
1987 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
1988 cx: &'a LateContext<'a, 'tcx>,
1989 body: &'a TypeckTables<'tcx>,
1990 target: &'b ImplicitHasherType<'tcx>,
1991 suggestions: BTreeMap<Span, String>,
1994 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
1995 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2000 suggestions: BTreeMap::new(),
2005 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2006 fn visit_body(&mut self, body: &'tcx Body) {
2007 self.body = self.cx.tcx.body_tables(body.id());
2008 walk_body(self, body);
2011 fn visit_expr(&mut self, e: &'tcx Expr) {
2013 if let ExprKind::Call(ref fun, ref args) = e.node;
2014 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2015 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2017 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2021 if match_path(ty_path, &paths::HASHMAP) {
2022 if method.ident.name == "new" {
2024 .insert(e.span, "HashMap::default()".to_string());
2025 } else if method.ident.name == "with_capacity" {
2026 self.suggestions.insert(
2029 "HashMap::with_capacity_and_hasher({}, Default::default())",
2030 snippet(self.cx, args[0].span, "capacity"),
2034 } else if match_path(ty_path, &paths::HASHSET) {
2035 if method.ident.name == "new" {
2037 .insert(e.span, "HashSet::default()".to_string());
2038 } else if method.ident.name == "with_capacity" {
2039 self.suggestions.insert(
2042 "HashSet::with_capacity_and_hasher({}, Default::default())",
2043 snippet(self.cx, args[0].span, "capacity"),
2054 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2055 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)