1 #![allow(clippy::default_hash_types)]
3 use crate::consts::{constant, Constant};
4 use crate::reexport::*;
5 use crate::utils::paths;
7 clip, comparisons, differing_macro_contexts, higher, in_constant, in_macro, int_bits, last_path_segment,
8 match_def_path, match_path, multispan_sugg, opt_def_id, same_tys, sext, snippet, snippet_opt,
9 snippet_with_applicability, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
12 use if_chain::if_chain;
14 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
16 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
17 use rustc::ty::layout::LayoutOf;
18 use rustc::ty::{self, Ty, TyCtxt, TypeckTables};
19 use rustc::{declare_tool_lint, lint_array};
20 use rustc_errors::Applicability;
21 use rustc_target::spec::abi::Abi;
22 use rustc_typeck::hir_ty_to_ty;
24 use std::cmp::Ordering;
25 use std::collections::BTreeMap;
26 use syntax::ast::{FloatTy, IntTy, UintTy};
27 use syntax::errors::DiagnosticBuilder;
28 use syntax::source_map::Span;
30 /// Handles all the linting of funky types
33 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
35 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
36 /// the heap. So if you `Box` it, you just add another level of indirection
37 /// without any benefit whatsoever.
39 /// **Known problems:** None.
44 /// values: Box<Vec<Foo>>,
55 declare_clippy_lint! {
58 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
61 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
63 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
64 /// the heap. So if you `Box` its contents, you just add another level of indirection.
66 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
72 /// values: Vec<Box<i32>>,
83 declare_clippy_lint! {
86 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
89 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
92 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
93 /// represents an optional optional value which is logically the same thing as an optional
94 /// value but has an unneeded extra level of wrapping.
96 /// **Known problems:** None.
100 /// fn x() -> Option<Option<u32>> {
103 declare_clippy_lint! {
106 "usage of `Option<Option<T>>`"
109 /// **What it does:** Checks for usage of any `LinkedList`, suggesting to use a
110 /// `Vec` or a `VecDeque` (formerly called `RingBuf`).
112 /// **Why is this bad?** Gankro says:
114 /// > The TL;DR of `LinkedList` is that it's built on a massive amount of
115 /// pointers and indirection.
116 /// > It wastes memory, it has terrible cache locality, and is all-around slow.
118 /// > "only" amortized for push/pop, should be faster in the general case for
119 /// almost every possible
120 /// > workload, and isn't even amortized at all if you can predict the capacity
123 /// > `LinkedList`s are only really good if you're doing a lot of merging or
124 /// splitting of lists.
125 /// > This is because they can just mangle some pointers instead of actually
126 /// copying the data. Even
127 /// > if you're doing a lot of insertion in the middle of the list, `RingBuf`
128 /// can still be better
129 /// > because of how expensive it is to seek to the middle of a `LinkedList`.
131 /// **Known problems:** False positives – the instances where using a
132 /// `LinkedList` makes sense are few and far between, but they can still happen.
136 /// let x = LinkedList::new();
138 declare_clippy_lint! {
141 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
144 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
146 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
149 /// **Known problems:** None.
153 /// fn foo(bar: &Box<T>) { ... }
159 /// fn foo(bar: &T) { ... }
161 declare_clippy_lint! {
164 "a borrow of a boxed type"
167 impl LintPass for TypePass {
168 fn get_lints(&self) -> LintArray {
169 lint_array!(BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX)
172 fn name(&self) -> &'static str {
177 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypePass {
178 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: NodeId) {
179 // skip trait implementations, see #605
180 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent(id)) {
181 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
186 check_fn_decl(cx, decl);
189 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &StructField) {
190 check_ty(cx, &field.ty, false);
193 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
195 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
196 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
201 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
202 if let Some(ref ty) = local.ty {
203 check_ty(cx, ty, true);
208 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
209 for input in &decl.inputs {
210 check_ty(cx, input, false);
213 if let FunctionRetTy::Return(ref ty) = decl.output {
214 check_ty(cx, ty, false);
218 /// Check if `qpath` has last segment with type parameter matching `path`
219 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
220 let last = last_path_segment(qpath);
222 if let Some(ref params) = last.args;
223 if !params.parenthesized;
224 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
225 GenericArg::Type(ty) => Some(ty),
226 GenericArg::Lifetime(_) => None,
228 if let TyKind::Path(ref qpath) = ty.node;
229 if let Some(did) = opt_def_id(cx.tables.qpath_def(qpath, cx.tcx.hir().node_to_hir_id(ty.id)));
230 if match_def_path(cx.tcx, did, path);
238 /// Recursively check for `TypePass` lints in the given type. Stop at the first
241 /// The parameter `is_local` distinguishes the context of the type; types from
242 /// local bindings should only be checked for the `BORROWED_BOX` lint.
243 fn check_ty(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool) {
244 if in_macro(ast_ty.span) {
248 TyKind::Path(ref qpath) if !is_local => {
249 let hir_id = cx.tcx.hir().node_to_hir_id(ast_ty.id);
250 let def = cx.tables.qpath_def(qpath, hir_id);
251 if let Some(def_id) = opt_def_id(def) {
252 if Some(def_id) == cx.tcx.lang_items().owned_box() {
253 if match_type_parameter(cx, qpath, &paths::VEC) {
258 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
259 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
261 return; // don't recurse into the type
263 } else if match_def_path(cx.tcx, def_id, &paths::VEC) {
265 // Get the _ part of Vec<_>
266 if let Some(ref last) = last_path_segment(qpath).args;
267 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
268 GenericArg::Type(ty) => Some(ty),
269 GenericArg::Lifetime(_) => None,
271 // ty is now _ at this point
272 if let TyKind::Path(ref ty_qpath) = ty.node;
273 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
274 if let Some(def_id) = opt_def_id(def);
275 if Some(def_id) == cx.tcx.lang_items().owned_box();
276 // At this point, we know ty is Box<T>, now get T
277 if let Some(ref last) = last_path_segment(ty_qpath).args;
278 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
279 GenericArg::Type(ty) => Some(ty),
280 GenericArg::Lifetime(_) => None,
282 if let TyKind::Path(ref ty_qpath) = ty.node;
283 let def = cx.tables.qpath_def(ty_qpath, ty.hir_id);
284 if let Some(def_id) = opt_def_id(def);
285 let boxed_type = cx.tcx.type_of(def_id);
286 if boxed_type.is_sized(cx.tcx.at(ty.span), cx.param_env);
292 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
294 format!("Vec<{}>", boxed_type),
295 Applicability::MaybeIncorrect,
297 return; // don't recurse into the type
300 } else if match_def_path(cx.tcx, def_id, &paths::OPTION) {
301 if match_type_parameter(cx, qpath, &paths::OPTION) {
306 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
307 enum if you need to distinguish all 3 cases",
309 return; // don't recurse into the type
311 } else if match_def_path(cx.tcx, def_id, &paths::LINKED_LIST) {
316 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
317 "a VecDeque might work",
319 return; // don't recurse into the type
323 QPath::Resolved(Some(ref ty), ref p) => {
324 check_ty(cx, ty, is_local);
325 for ty in p.segments.iter().flat_map(|seg| {
328 .map_or_else(|| [].iter(), |params| params.args.iter())
329 .filter_map(|arg| match arg {
330 GenericArg::Type(ty) => Some(ty),
331 GenericArg::Lifetime(_) => None,
334 check_ty(cx, ty, is_local);
337 QPath::Resolved(None, ref p) => {
338 for ty in p.segments.iter().flat_map(|seg| {
341 .map_or_else(|| [].iter(), |params| params.args.iter())
342 .filter_map(|arg| match arg {
343 GenericArg::Type(ty) => Some(ty),
344 GenericArg::Lifetime(_) => None,
347 check_ty(cx, ty, is_local);
350 QPath::TypeRelative(ref ty, ref seg) => {
351 check_ty(cx, ty, is_local);
352 if let Some(ref params) = seg.args {
353 for ty in params.args.iter().filter_map(|arg| match arg {
354 GenericArg::Type(ty) => Some(ty),
355 GenericArg::Lifetime(_) => None,
357 check_ty(cx, ty, is_local);
363 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, ast_ty, is_local, lt, mut_ty),
365 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
366 check_ty(cx, ty, is_local)
368 TyKind::Tup(ref tys) => {
370 check_ty(cx, ty, is_local);
377 fn check_ty_rptr(cx: &LateContext<'_, '_>, ast_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
378 match mut_ty.ty.node {
379 TyKind::Path(ref qpath) => {
380 let hir_id = cx.tcx.hir().node_to_hir_id(mut_ty.ty.id);
381 let def = cx.tables.qpath_def(qpath, hir_id);
383 if let Some(def_id) = opt_def_id(def);
384 if Some(def_id) == cx.tcx.lang_items().owned_box();
385 if let QPath::Resolved(None, ref path) = *qpath;
386 if let [ref bx] = *path.segments;
387 if let Some(ref params) = bx.args;
388 if !params.parenthesized;
389 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
390 GenericArg::Type(ty) => Some(ty),
391 GenericArg::Lifetime(_) => None,
394 if is_any_trait(inner) {
395 // Ignore `Box<Any>` types, see #1884 for details.
399 let ltopt = if lt.is_elided() {
402 format!("{} ", lt.name.ident().as_str())
404 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
409 let mut applicability = Applicability::MachineApplicable;
414 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
420 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
422 Applicability::Unspecified,
424 return; // don't recurse into the type
427 check_ty(cx, &mut_ty.ty, is_local);
429 _ => check_ty(cx, &mut_ty.ty, is_local),
433 // Returns true if given type is `Any` trait.
434 fn is_any_trait(t: &hir::Ty) -> bool {
436 if let TyKind::TraitObject(ref traits, _) = t.node;
437 if traits.len() >= 1;
438 // Only Send/Sync can be used as additional traits, so it is enough to
439 // check only the first trait.
440 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
451 /// **What it does:** Checks for binding a unit value.
453 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
454 /// binding one is kind of pointless.
456 /// **Known problems:** None.
464 declare_clippy_lint! {
467 "creating a let binding to a value of unit type, which usually can't be used afterwards"
470 impl LintPass for LetPass {
471 fn get_lints(&self) -> LintArray {
472 lint_array!(LET_UNIT_VALUE)
475 fn name(&self) -> &'static str {
480 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetPass {
481 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
482 if let StmtKind::Local(ref local) = stmt.node {
483 if is_unit(cx.tables.pat_ty(&local.pat)) {
484 if in_external_macro(cx.sess(), stmt.span) || in_macro(local.pat.span) {
487 if higher::is_from_for_desugar(local) {
495 "this let-binding has unit value. Consider omitting `let {} =`",
496 snippet(cx, local.pat.span, "..")
504 /// **What it does:** Checks for comparisons to unit.
506 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
507 /// clumsily written constant. Mostly this happens when someone accidentally
508 /// adds semicolons at the end of the operands.
510 /// **Known problems:** None.
530 declare_clippy_lint! {
533 "comparing unit values"
538 impl LintPass for UnitCmp {
539 fn get_lints(&self) -> LintArray {
540 lint_array!(UNIT_CMP)
543 fn name(&self) -> &'static str {
548 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
549 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
550 if in_macro(expr.span) {
553 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
555 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
556 let result = match op {
557 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
565 "{}-comparison of unit values detected. This will always be {}",
575 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
576 /// unit literal (`()`).
578 /// **Why is this bad?** This is likely the result of an accidental semicolon.
580 /// **Known problems:** None.
589 declare_clippy_lint! {
592 "passing unit to a function"
597 impl LintPass for UnitArg {
598 fn get_lints(&self) -> LintArray {
599 lint_array!(UNIT_ARG)
602 fn name(&self) -> &'static str {
607 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
608 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
609 if in_macro(expr.span) {
613 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
615 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
616 let map = &cx.tcx.hir();
617 // apparently stuff in the desugaring of `?` can trigger this
618 // so check for that here
619 // only the calls to `Try::from_error` is marked as desugared,
620 // so we need to check both the current Expr and its parent.
621 if !is_questionmark_desugar_marked_call(expr) {
623 let opt_parent_node = map.find(map.get_parent_node(expr.id));
624 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
625 if is_questionmark_desugar_marked_call(parent_expr);
628 // `expr` and `parent_expr` where _both_ not from
629 // desugaring `?`, so lint
634 "passing a unit value to a function",
635 "if you intended to pass a unit value, use a unit literal instead",
637 Applicability::MachineApplicable,
650 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
651 use syntax_pos::hygiene::CompilerDesugaringKind;
652 if let ExprKind::Call(ref callee, _) = expr.node {
653 callee.span.is_compiler_desugaring(CompilerDesugaringKind::QuestionMark)
659 fn is_unit(ty: Ty<'_>) -> bool {
661 ty::Tuple(slice) if slice.is_empty() => true,
666 fn is_unit_literal(expr: &Expr) -> bool {
668 ExprKind::Tup(ref slice) if slice.is_empty() => true,
675 /// **What it does:** Checks for casts from any numerical to a float type where
676 /// the receiving type cannot store all values from the original type without
677 /// rounding errors. This possible rounding is to be expected, so this lint is
678 /// `Allow` by default.
680 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
681 /// or any 64-bit integer to `f64`.
683 /// **Why is this bad?** It's not bad at all. But in some applications it can be
684 /// helpful to know where precision loss can take place. This lint can help find
685 /// those places in the code.
687 /// **Known problems:** None.
691 /// let x = u64::MAX;
694 declare_clippy_lint! {
695 pub CAST_PRECISION_LOSS,
697 "casts that cause loss of precision, e.g. `x as f32` where `x: u64`"
700 /// **What it does:** Checks for casts from a signed to an unsigned numerical
701 /// type. In this case, negative values wrap around to large positive values,
702 /// which can be quite surprising in practice. However, as the cast works as
703 /// defined, this lint is `Allow` by default.
705 /// **Why is this bad?** Possibly surprising results. You can activate this lint
706 /// as a one-time check to see where numerical wrapping can arise.
708 /// **Known problems:** None.
713 /// y as u128 // will return 18446744073709551615
715 declare_clippy_lint! {
718 "casts from signed types to unsigned types, e.g. `x as u32` where `x: i32`"
721 /// **What it does:** Checks for on casts between numerical types that may
722 /// truncate large values. This is expected behavior, so the cast is `Allow` by
725 /// **Why is this bad?** In some problem domains, it is good practice to avoid
726 /// truncation. This lint can be activated to help assess where additional
727 /// checks could be beneficial.
729 /// **Known problems:** None.
733 /// fn as_u8(x: u64) -> u8 {
737 declare_clippy_lint! {
738 pub CAST_POSSIBLE_TRUNCATION,
740 "casts that may cause truncation of the value, e.g. `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
743 /// **What it does:** Checks for casts from an unsigned type to a signed type of
744 /// the same size. Performing such a cast is a 'no-op' for the compiler,
745 /// i.e. nothing is changed at the bit level, and the binary representation of
746 /// the value is reinterpreted. This can cause wrapping if the value is too big
747 /// for the target signed type. However, the cast works as defined, so this lint
748 /// is `Allow` by default.
750 /// **Why is this bad?** While such a cast is not bad in itself, the results can
751 /// be surprising when this is not the intended behavior, as demonstrated by the
754 /// **Known problems:** None.
758 /// u32::MAX as i32 // will yield a value of `-1`
760 declare_clippy_lint! {
761 pub CAST_POSSIBLE_WRAP,
763 "casts that may cause wrapping around the value, e.g. `x as i32` where `x: u32` and `x > i32::MAX`"
766 /// **What it does:** Checks for on casts between numerical types that may
767 /// be replaced by safe conversion functions.
769 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
770 /// conversions, including silently lossy conversions. Conversion functions such
771 /// as `i32::from` will only perform lossless conversions. Using the conversion
772 /// functions prevents conversions from turning into silent lossy conversions if
773 /// the types of the input expressions ever change, and make it easier for
774 /// people reading the code to know that the conversion is lossless.
776 /// **Known problems:** None.
780 /// fn as_u64(x: u8) -> u64 {
785 /// Using `::from` would look like this:
788 /// fn as_u64(x: u8) -> u64 {
792 declare_clippy_lint! {
795 "casts using `as` that are known to be lossless, e.g. `x as u64` where `x: u8`"
798 /// **What it does:** Checks for casts to the same type.
800 /// **Why is this bad?** It's just unnecessary.
802 /// **Known problems:** None.
806 /// let _ = 2i32 as i32
808 declare_clippy_lint! {
809 pub UNNECESSARY_CAST,
811 "cast to the same type, e.g. `x as i32` where `x: i32`"
814 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
815 /// more-strictly-aligned pointer
817 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
820 /// **Known problems:** None.
824 /// let _ = (&1u8 as *const u8) as *const u16;
825 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
827 declare_clippy_lint! {
828 pub CAST_PTR_ALIGNMENT,
830 "cast from a pointer to a more-strictly-aligned pointer"
833 /// **What it does:** Checks for casts of function pointers to something other than usize
835 /// **Why is this bad?**
836 /// Casting a function pointer to anything other than usize/isize is not portable across
837 /// architectures, because you end up losing bits if the target type is too small or end up with a
838 /// bunch of extra bits that waste space and add more instructions to the final binary than
839 /// strictly necessary for the problem
841 /// Casting to isize also doesn't make sense since there are no signed addresses.
847 /// fn fun() -> i32 {}
848 /// let a = fun as i64;
851 /// fn fun2() -> i32 {}
852 /// let a = fun2 as usize;
854 declare_clippy_lint! {
855 pub FN_TO_NUMERIC_CAST,
857 "casting a function pointer to a numeric type other than usize"
860 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
863 /// **Why is this bad?**
864 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
865 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
866 /// a comment) to perform the truncation.
872 /// fn fn1() -> i16 {
875 /// let _ = fn1 as i32;
877 /// // Better: Cast to usize first, then comment with the reason for the truncation
878 /// fn fn2() -> i16 {
881 /// let fn_ptr = fn2 as usize;
882 /// let fn_ptr_truncated = fn_ptr as i32;
884 declare_clippy_lint! {
885 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
887 "casting a function pointer to a numeric type not wide enough to store the address"
890 /// Returns the size in bits of an integral type.
891 /// Will return 0 if the type is not an int or uint variant
892 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_, '_, '_>) -> u64 {
894 ty::Int(i) => match i {
895 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
902 ty::Uint(i) => match i {
903 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
914 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
916 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
921 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
922 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
923 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
924 let arch_dependent_str = "on targets with 64-bit wide pointers ";
925 let from_nbits_str = if arch_dependent {
927 } else if is_isize_or_usize(cast_from) {
928 "32 or 64".to_owned()
930 int_ty_to_nbits(cast_from, cx.tcx).to_string()
937 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
938 is only {4} bits wide)",
940 if cast_to_f64 { "f64" } else { "f32" },
941 if arch_dependent { arch_dependent_str } else { "" },
948 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
949 if let ExprKind::Binary(_, _, _) = op.node {
950 if snip.starts_with('(') && snip.ends_with(')') {
957 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
958 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
959 if in_constant(cx, expr.id) {
962 // The suggestion is to use a function call, so if the original expression
963 // has parens on the outside, they are no longer needed.
964 let mut applicability = Applicability::MachineApplicable;
965 let opt = snippet_opt(cx, op.span);
966 let sugg = if let Some(ref snip) = opt {
967 if should_strip_parens(op, snip) {
968 &snip[1..snip.len() - 1]
973 applicability = Applicability::HasPlaceholders;
982 "casting {} to {} may become silently lossy if types change",
986 format!("{}::from({})", cast_to, sugg),
997 fn check_truncation_and_wrapping(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
998 let arch_64_suffix = " on targets with 64-bit wide pointers";
999 let arch_32_suffix = " on targets with 32-bit wide pointers";
1000 let cast_unsigned_to_signed = !cast_from.is_signed() && cast_to.is_signed();
1001 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1002 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1003 let (span_truncation, suffix_truncation, span_wrap, suffix_wrap) =
1004 match (is_isize_or_usize(cast_from), is_isize_or_usize(cast_to)) {
1005 (true, true) | (false, false) => (
1006 to_nbits < from_nbits,
1008 to_nbits == from_nbits && cast_unsigned_to_signed,
1018 to_nbits <= 32 && cast_unsigned_to_signed,
1024 cast_unsigned_to_signed,
1025 if from_nbits == 64 {
1032 if span_truncation {
1035 CAST_POSSIBLE_TRUNCATION,
1038 "casting {} to {} may truncate the value{}",
1041 match suffix_truncation {
1042 ArchSuffix::_32 => arch_32_suffix,
1043 ArchSuffix::_64 => arch_64_suffix,
1044 ArchSuffix::None => "",
1055 "casting {} to {} may wrap around the value{}",
1059 ArchSuffix::_32 => arch_32_suffix,
1060 ArchSuffix::_64 => arch_64_suffix,
1061 ArchSuffix::None => "",
1068 fn check_lossless(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
1069 let cast_signed_to_unsigned = cast_from.is_signed() && !cast_to.is_signed();
1070 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1071 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1072 if !is_isize_or_usize(cast_from) && !is_isize_or_usize(cast_to) && from_nbits < to_nbits && !cast_signed_to_unsigned
1074 span_lossless_lint(cx, expr, op, cast_from, cast_to);
1078 impl LintPass for CastPass {
1079 fn get_lints(&self) -> LintArray {
1081 CAST_PRECISION_LOSS,
1083 CAST_POSSIBLE_TRUNCATION,
1089 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1093 fn name(&self) -> &'static str {
1098 // Check if the given type is either `core::ffi::c_void` or
1099 // one of the platform specific `libc::<platform>::c_void` of libc.
1100 fn is_c_void(tcx: TyCtxt<'_, '_, '_>, ty: Ty<'_>) -> bool {
1101 if let ty::Adt(adt, _) = ty.sty {
1102 let mut apb = AbsolutePathBuffer { names: vec![] };
1103 tcx.push_item_path(&mut apb, adt.did, false);
1105 if apb.names.is_empty() {
1108 if apb.names[0] == "libc" || apb.names[0] == "core" && *apb.names.last().unwrap() == "c_void" {
1115 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
1116 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1117 if let ExprKind::Cast(ref ex, _) = expr.node {
1118 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1119 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1120 if let ExprKind::Lit(ref lit) = ex.node {
1121 use syntax::ast::{LitIntType, LitKind};
1123 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1125 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1131 "casting to the same type is unnecessary (`{}` -> `{}`)",
1139 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1140 match (cast_from.is_integral(), cast_to.is_integral()) {
1142 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1143 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1148 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1149 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1151 if from_nbits < to_nbits {
1152 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1158 CAST_POSSIBLE_TRUNCATION,
1160 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1162 if !cast_to.is_signed() {
1167 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1172 if cast_from.is_signed() && !cast_to.is_signed() {
1177 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1180 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1181 check_lossless(cx, expr, ex, cast_from, cast_to);
1184 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1187 CAST_POSSIBLE_TRUNCATION,
1189 "casting f64 to f32 may truncate the value",
1192 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1193 span_lossless_lint(cx, expr, ex, cast_from, cast_to);
1200 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1201 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1202 if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
1203 if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
1204 if from_align < to_align;
1205 // with c_void, we inherently need to trust the user
1206 if !is_c_void(cx.tcx, from_ptr_ty.ty);
1212 &format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
1220 fn lint_fn_to_numeric_cast(
1221 cx: &LateContext<'_, '_>,
1227 // We only want to check casts to `ty::Uint` or `ty::Int`
1229 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1232 match cast_from.sty {
1233 ty::FnDef(..) | ty::FnPtr(_) => {
1234 let mut applicability = Applicability::MachineApplicable;
1235 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1237 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1238 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1241 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1244 "casting function pointer `{}` to `{}`, which truncates the value",
1245 from_snippet, cast_to
1248 format!("{} as usize", from_snippet),
1251 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1256 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1258 format!("{} as usize", from_snippet),
1267 /// **What it does:** Checks for types used in structs, parameters and `let`
1268 /// declarations above a certain complexity threshold.
1270 /// **Why is this bad?** Too complex types make the code less readable. Consider
1271 /// using a `type` definition to simplify them.
1273 /// **Known problems:** None.
1278 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1281 declare_clippy_lint! {
1282 pub TYPE_COMPLEXITY,
1284 "usage of very complex types that might be better factored into `type` definitions"
1287 pub struct TypeComplexityPass {
1291 impl TypeComplexityPass {
1292 pub fn new(threshold: u64) -> Self {
1297 impl LintPass for TypeComplexityPass {
1298 fn get_lints(&self) -> LintArray {
1299 lint_array!(TYPE_COMPLEXITY)
1302 fn name(&self) -> &'static str {
1303 "TypeComplexityPass"
1307 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexityPass {
1310 cx: &LateContext<'a, 'tcx>,
1317 self.check_fndecl(cx, decl);
1320 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx StructField) {
1321 // enum variants are also struct fields now
1322 self.check_type(cx, &field.ty);
1325 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1327 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1328 // functions, enums, structs, impls and traits are covered
1333 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1335 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1336 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1337 // methods with default impl are covered by check_fn
1342 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1344 ImplItemKind::Const(ref ty, _) | ImplItemKind::Type(ref ty) => self.check_type(cx, ty),
1345 // methods are covered by check_fn
1350 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1351 if let Some(ref ty) = local.ty {
1352 self.check_type(cx, ty);
1357 impl<'a, 'tcx> TypeComplexityPass {
1358 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1359 for arg in &decl.inputs {
1360 self.check_type(cx, arg);
1362 if let Return(ref ty) = decl.output {
1363 self.check_type(cx, ty);
1367 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1368 if in_macro(ty.span) {
1372 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1373 visitor.visit_ty(ty);
1377 if score > self.threshold {
1382 "very complex type used. Consider factoring parts into `type` definitions",
1388 /// Walks a type and assigns a complexity score to it.
1389 struct TypeComplexityVisitor {
1390 /// total complexity score of the type
1392 /// current nesting level
1396 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1397 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1398 let (add_score, sub_nest) = match ty.node {
1399 // _, &x and *x have only small overhead; don't mess with nesting level
1400 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1402 // the "normal" components of a type: named types, arrays/tuples
1403 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1405 // function types bring a lot of overhead
1406 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1408 TyKind::TraitObject(ref param_bounds, _) => {
1409 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1410 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1411 GenericParamKind::Lifetime { .. } => true,
1415 if has_lifetime_parameters {
1416 // complex trait bounds like A<'a, 'b>
1419 // simple trait bounds like A + B
1426 self.score += add_score;
1427 self.nest += sub_nest;
1429 self.nest -= sub_nest;
1431 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1432 NestedVisitorMap::None
1436 /// **What it does:** Checks for expressions where a character literal is cast
1437 /// to `u8` and suggests using a byte literal instead.
1439 /// **Why is this bad?** In general, casting values to smaller types is
1440 /// error-prone and should be avoided where possible. In the particular case of
1441 /// converting a character literal to u8, it is easy to avoid by just using a
1442 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1443 /// than `'a' as u8`.
1445 /// **Known problems:** None.
1452 /// A better version, using the byte literal:
1457 declare_clippy_lint! {
1460 "casting a character literal to u8"
1463 pub struct CharLitAsU8;
1465 impl LintPass for CharLitAsU8 {
1466 fn get_lints(&self) -> LintArray {
1467 lint_array!(CHAR_LIT_AS_U8)
1470 fn name(&self) -> &'static str {
1475 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1476 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1477 use syntax::ast::{LitKind, UintTy};
1479 if let ExprKind::Cast(ref e, _) = expr.node {
1480 if let ExprKind::Lit(ref l) = e.node {
1481 if let LitKind::Char(_) = l.node {
1482 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty && !in_macro(expr.span) {
1483 let msg = "casting character literal to u8. `char`s \
1484 are 4 bytes wide in rust, so casting to u8 \
1487 "Consider using a byte literal instead:\nb{}",
1488 snippet(cx, e.span, "'x'")
1490 span_help_and_lint(cx, CHAR_LIT_AS_U8, expr.span, msg, &help);
1498 /// **What it does:** Checks for comparisons where one side of the relation is
1499 /// either the minimum or maximum value for its type and warns if it involves a
1500 /// case that is always true or always false. Only integer and boolean types are
1503 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1504 /// that is is possible for `x` to be less than the minimum. Expressions like
1505 /// `max < x` are probably mistakes.
1507 /// **Known problems:** For `usize` the size of the current compile target will
1508 /// be assumed (e.g. 64 bits on 64 bit systems). This means code that uses such
1509 /// a comparison to detect target pointer width will trigger this lint. One can
1510 /// use `mem::sizeof` and compare its value or conditional compilation
1512 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1517 /// 100 > std::i32::MAX
1519 declare_clippy_lint! {
1520 pub ABSURD_EXTREME_COMPARISONS,
1522 "a comparison with a maximum or minimum value that is always true or false"
1525 pub struct AbsurdExtremeComparisons;
1527 impl LintPass for AbsurdExtremeComparisons {
1528 fn get_lints(&self) -> LintArray {
1529 lint_array!(ABSURD_EXTREME_COMPARISONS)
1532 fn name(&self) -> &'static str {
1533 "AbsurdExtremeComparisons"
1542 struct ExtremeExpr<'a> {
1547 enum AbsurdComparisonResult {
1550 InequalityImpossible,
1553 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1554 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1555 let precast_ty = cx.tables.expr_ty(cast_exp);
1556 let cast_ty = cx.tables.expr_ty(expr);
1558 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1564 fn detect_absurd_comparison<'a, 'tcx>(
1565 cx: &LateContext<'a, 'tcx>,
1569 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1570 use crate::types::AbsurdComparisonResult::*;
1571 use crate::types::ExtremeType::*;
1572 use crate::utils::comparisons::*;
1574 // absurd comparison only makes sense on primitive types
1575 // primitive types don't implement comparison operators with each other
1576 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1580 // comparisons between fix sized types and target sized types are considered unanalyzable
1581 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1585 let normalized = normalize_comparison(op, lhs, rhs);
1586 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1592 let lx = detect_extreme_expr(cx, normalized_lhs);
1593 let rx = detect_extreme_expr(cx, normalized_rhs);
1598 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1599 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1605 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1606 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1607 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1608 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1612 Rel::Ne | Rel::Eq => return None,
1616 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1617 use crate::types::ExtremeType::*;
1619 let ty = cx.tables.expr_ty(expr);
1621 let cv = constant(cx, cx.tables, expr)?.0;
1623 let which = match (&ty.sty, cv) {
1624 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1625 (&ty::Int(ity), Constant::Int(i))
1626 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1631 (&ty::Bool, Constant::Bool(true)) => Maximum,
1632 (&ty::Int(ity), Constant::Int(i))
1633 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1637 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1641 Some(ExtremeExpr { which, expr })
1644 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1645 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1646 use crate::types::AbsurdComparisonResult::*;
1647 use crate::types::ExtremeType::*;
1649 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1650 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1651 if !in_macro(expr.span) {
1652 let msg = "this comparison involving the minimum or maximum element for this \
1653 type contains a case that is always true or always false";
1655 let conclusion = match result {
1656 AlwaysFalse => "this comparison is always false".to_owned(),
1657 AlwaysTrue => "this comparison is always true".to_owned(),
1658 InequalityImpossible => format!(
1659 "the case where the two sides are not equal never occurs, consider using {} == {} \
1661 snippet(cx, lhs.span, "lhs"),
1662 snippet(cx, rhs.span, "rhs")
1667 "because {} is the {} value for this type, {}",
1668 snippet(cx, culprit.expr.span, "x"),
1669 match culprit.which {
1670 Minimum => "minimum",
1671 Maximum => "maximum",
1676 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1683 /// **What it does:** Checks for comparisons where the relation is always either
1684 /// true or false, but where one side has been upcast so that the comparison is
1685 /// necessary. Only integer types are checked.
1687 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1688 /// will mistakenly imply that it is possible for `x` to be outside the range of
1691 /// **Known problems:**
1692 /// https://github.com/rust-lang/rust-clippy/issues/886
1696 /// let x : u8 = ...; (x as u32) > 300
1698 declare_clippy_lint! {
1699 pub INVALID_UPCAST_COMPARISONS,
1701 "a comparison involving an upcast which is always true or false"
1704 pub struct InvalidUpcastComparisons;
1706 impl LintPass for InvalidUpcastComparisons {
1707 fn get_lints(&self) -> LintArray {
1708 lint_array!(INVALID_UPCAST_COMPARISONS)
1711 fn name(&self) -> &'static str {
1712 "InvalidUpcastComparisons"
1716 #[derive(Copy, Clone, Debug, Eq)]
1723 #[allow(clippy::cast_sign_loss)]
1724 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1727 } else if u > (i128::max_value() as u128) {
1735 impl PartialEq for FullInt {
1736 fn eq(&self, other: &Self) -> bool {
1737 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1741 impl PartialOrd for FullInt {
1742 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1743 Some(match (self, other) {
1744 (&FullInt::S(s), &FullInt::S(o)) => s.cmp(&o),
1745 (&FullInt::U(s), &FullInt::U(o)) => s.cmp(&o),
1746 (&FullInt::S(s), &FullInt::U(o)) => Self::cmp_s_u(s, o),
1747 (&FullInt::U(s), &FullInt::S(o)) => Self::cmp_s_u(o, s).reverse(),
1751 impl Ord for FullInt {
1752 fn cmp(&self, other: &Self) -> Ordering {
1753 self.partial_cmp(other)
1754 .expect("partial_cmp for FullInt can never return None")
1758 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1760 use syntax::ast::{IntTy, UintTy};
1762 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1763 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1764 let cast_ty = cx.tables.expr_ty(expr);
1765 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1766 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1769 match pre_cast_ty.sty {
1770 ty::Int(int_ty) => Some(match int_ty {
1772 FullInt::S(i128::from(i8::min_value())),
1773 FullInt::S(i128::from(i8::max_value())),
1776 FullInt::S(i128::from(i16::min_value())),
1777 FullInt::S(i128::from(i16::max_value())),
1780 FullInt::S(i128::from(i32::min_value())),
1781 FullInt::S(i128::from(i32::max_value())),
1784 FullInt::S(i128::from(i64::min_value())),
1785 FullInt::S(i128::from(i64::max_value())),
1787 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1789 FullInt::S(isize::min_value() as i128),
1790 FullInt::S(isize::max_value() as i128),
1793 ty::Uint(uint_ty) => Some(match uint_ty {
1795 FullInt::U(u128::from(u8::min_value())),
1796 FullInt::U(u128::from(u8::max_value())),
1799 FullInt::U(u128::from(u16::min_value())),
1800 FullInt::U(u128::from(u16::max_value())),
1803 FullInt::U(u128::from(u32::min_value())),
1804 FullInt::U(u128::from(u32::max_value())),
1807 FullInt::U(u128::from(u64::min_value())),
1808 FullInt::U(u128::from(u64::max_value())),
1810 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1812 FullInt::U(usize::min_value() as u128),
1813 FullInt::U(usize::max_value() as u128),
1823 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1824 let val = constant(cx, cx.tables, expr)?.0;
1825 if let Constant::Int(const_int) = val {
1826 match cx.tables.expr_ty(expr).sty {
1827 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1828 ty::Uint(_) => Some(FullInt::U(const_int)),
1836 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1837 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1840 INVALID_UPCAST_COMPARISONS,
1843 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1844 snippet(cx, cast_val.span, "the expression"),
1845 if always { "true" } else { "false" },
1851 fn upcast_comparison_bounds_err<'a, 'tcx>(
1852 cx: &LateContext<'a, 'tcx>,
1854 rel: comparisons::Rel,
1855 lhs_bounds: Option<(FullInt, FullInt)>,
1860 use crate::utils::comparisons::*;
1862 if let Some((lb, ub)) = lhs_bounds {
1863 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1864 if rel == Rel::Eq || rel == Rel::Ne {
1865 if norm_rhs_val < lb || norm_rhs_val > ub {
1866 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1868 } else if match rel {
1883 Rel::Eq | Rel::Ne => unreachable!(),
1885 err_upcast_comparison(cx, span, lhs, true)
1886 } else if match rel {
1901 Rel::Eq | Rel::Ne => unreachable!(),
1903 err_upcast_comparison(cx, span, lhs, false)
1909 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1910 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1911 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1912 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1913 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1919 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1920 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1922 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1923 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1928 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1929 /// over different hashers and implicitly defaulting to the default hashing
1930 /// algorithm (SipHash).
1932 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1935 /// **Known problems:** Suggestions for replacing constructors can contain
1936 /// false-positives. Also applying suggestions can require modification of other
1937 /// pieces of code, possibly including external crates.
1941 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { ... }
1943 /// pub foo(map: &mut HashMap<i32, i32>) { .. }
1945 declare_clippy_lint! {
1946 pub IMPLICIT_HASHER,
1948 "missing generalization over different hashers"
1951 pub struct ImplicitHasher;
1953 impl LintPass for ImplicitHasher {
1954 fn get_lints(&self) -> LintArray {
1955 lint_array!(IMPLICIT_HASHER)
1958 fn name(&self) -> &'static str {
1963 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1964 #[allow(clippy::cast_possible_truncation)]
1965 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1966 use syntax_pos::BytePos;
1968 fn suggestion<'a, 'tcx>(
1969 cx: &LateContext<'a, 'tcx>,
1970 db: &mut DiagnosticBuilder<'_>,
1971 generics_span: Span,
1972 generics_suggestion_span: Span,
1973 target: &ImplicitHasherType<'_>,
1974 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1976 let generics_snip = snippet(cx, generics_span, "");
1978 let generics_snip = if generics_snip.is_empty() {
1981 &generics_snip[1..generics_snip.len() - 1]
1986 "consider adding a type parameter".to_string(),
1989 generics_suggestion_span,
1991 "<{}{}S: ::std::hash::BuildHasher{}>",
1993 if generics_snip.is_empty() { "" } else { ", " },
1994 if vis.suggestions.is_empty() {
1997 // request users to add `Default` bound so that generic constructors can be used
2004 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2009 if !vis.suggestions.is_empty() {
2010 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2014 if !cx.access_levels.is_exported(item.id) {
2019 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2020 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2023 for target in &vis.found {
2024 if differing_macro_contexts(item.span, target.span()) {
2028 let generics_suggestion_span = generics.span.substitute_dummy({
2029 let pos = snippet_opt(cx, item.span.until(target.span()))
2030 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2031 if let Some(pos) = pos {
2032 Span::new(pos, pos, item.span.data().ctxt)
2038 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2039 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2040 ctr_vis.visit_impl_item(item);
2048 "impl for `{}` should be generalized over different hashers",
2052 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2057 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2058 let body = cx.tcx.hir().body(body_id);
2060 for ty in &decl.inputs {
2061 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2064 for target in &vis.found {
2065 let generics_suggestion_span = generics.span.substitute_dummy({
2066 let pos = snippet_opt(cx, item.span.until(body.arguments[0].pat.span))
2068 let i = snip.find("fn")?;
2069 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2071 .expect("failed to create span for type parameters");
2072 Span::new(pos, pos, item.span.data().ctxt)
2075 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2076 ctr_vis.visit_body(body);
2083 "parameter of type `{}` should be generalized over different hashers",
2087 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2098 enum ImplicitHasherType<'tcx> {
2099 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2100 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2103 impl<'tcx> ImplicitHasherType<'tcx> {
2104 /// Checks that `ty` is a target type without a BuildHasher.
2105 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2106 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2107 let params: Vec<_> = path
2115 .filter_map(|arg| match arg {
2116 GenericArg::Type(ty) => Some(ty),
2117 GenericArg::Lifetime(_) => None,
2120 let params_len = params.len();
2122 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2124 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2125 Some(ImplicitHasherType::HashMap(
2128 snippet(cx, params[0].span, "K"),
2129 snippet(cx, params[1].span, "V"),
2131 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2132 Some(ImplicitHasherType::HashSet(
2135 snippet(cx, params[0].span, "T"),
2145 fn type_name(&self) -> &'static str {
2147 ImplicitHasherType::HashMap(..) => "HashMap",
2148 ImplicitHasherType::HashSet(..) => "HashSet",
2152 fn type_arguments(&self) -> String {
2154 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2155 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2159 fn ty(&self) -> Ty<'tcx> {
2161 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2165 fn span(&self) -> Span {
2167 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2172 struct ImplicitHasherTypeVisitor<'a, 'tcx: 'a> {
2173 cx: &'a LateContext<'a, 'tcx>,
2174 found: Vec<ImplicitHasherType<'tcx>>,
2177 impl<'a, 'tcx: 'a> ImplicitHasherTypeVisitor<'a, 'tcx> {
2178 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2179 Self { cx, found: vec![] }
2183 impl<'a, 'tcx: 'a> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2184 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2185 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2186 self.found.push(target);
2192 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2193 NestedVisitorMap::None
2197 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2198 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx: 'a + 'b> {
2199 cx: &'a LateContext<'a, 'tcx>,
2200 body: &'a TypeckTables<'tcx>,
2201 target: &'b ImplicitHasherType<'tcx>,
2202 suggestions: BTreeMap<Span, String>,
2205 impl<'a, 'b, 'tcx: 'a + 'b> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2206 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2211 suggestions: BTreeMap::new(),
2216 impl<'a, 'b, 'tcx: 'a + 'b> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2217 fn visit_body(&mut self, body: &'tcx Body) {
2218 self.body = self.cx.tcx.body_tables(body.id());
2219 walk_body(self, body);
2222 fn visit_expr(&mut self, e: &'tcx Expr) {
2224 if let ExprKind::Call(ref fun, ref args) = e.node;
2225 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2226 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2228 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2232 if match_path(ty_path, &paths::HASHMAP) {
2233 if method.ident.name == "new" {
2235 .insert(e.span, "HashMap::default()".to_string());
2236 } else if method.ident.name == "with_capacity" {
2237 self.suggestions.insert(
2240 "HashMap::with_capacity_and_hasher({}, Default::default())",
2241 snippet(self.cx, args[0].span, "capacity"),
2245 } else if match_path(ty_path, &paths::HASHSET) {
2246 if method.ident.name == "new" {
2248 .insert(e.span, "HashSet::default()".to_string());
2249 } else if method.ident.name == "with_capacity" {
2250 self.suggestions.insert(
2253 "HashSet::with_capacity_and_hasher({}, Default::default())",
2254 snippet(self.cx, args[0].span, "capacity"),
2265 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2266 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2270 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2272 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2273 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2276 /// **Known problems:** None.
2282 /// *(r as *const _ as *mut _) += 1;
2287 /// Instead consider using interior mutability types.
2290 /// fn x(r: &UnsafeCell<i32>) {
2296 declare_clippy_lint! {
2297 pub CAST_REF_TO_MUT,
2299 "a cast of reference to a mutable pointer"
2302 pub struct RefToMut;
2304 impl LintPass for RefToMut {
2305 fn get_lints(&self) -> LintArray {
2306 lint_array!(CAST_REF_TO_MUT)
2309 fn name(&self) -> &'static str {
2314 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2315 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2317 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2318 if let ExprKind::Cast(e, t) = &e.node;
2319 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2320 if let ExprKind::Cast(e, t) = &e.node;
2321 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2322 if let ty::Ref(..) = cx.tables.node_id_to_type(e.hir_id).sty;
2328 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",