1 #![allow(rustc::default_hash_types)]
4 use std::cmp::Ordering;
5 use std::collections::BTreeMap;
7 use if_chain::if_chain;
9 use rustc::hir::intravisit::{walk_body, walk_expr, walk_ty, FnKind, NestedVisitorMap, Visitor};
11 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
12 use rustc::ty::layout::LayoutOf;
13 use rustc::ty::{self, InferTy, Ty, TyCtxt, TypeckTables};
14 use rustc::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
15 use rustc_errors::Applicability;
16 use rustc_target::spec::abi::Abi;
17 use rustc_typeck::hir_ty_to_ty;
18 use syntax::ast::{FloatTy, IntTy, LitIntType, LitKind, UintTy};
19 use syntax::errors::DiagnosticBuilder;
20 use syntax::source_map::Span;
21 use syntax::symbol::{sym, Symbol};
23 use crate::consts::{constant, Constant};
24 use crate::utils::paths;
26 clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
27 match_path, multispan_sugg, same_tys, sext, snippet, snippet_opt, snippet_with_applicability,
28 snippet_with_macro_callsite, span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then, unsext,
31 declare_clippy_lint! {
32 /// **What it does:** Checks for use of `Box<Vec<_>>` anywhere in the code.
34 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
35 /// the heap. So if you `Box` it, you just add another level of indirection
36 /// without any benefit whatsoever.
38 /// **Known problems:** None.
43 /// values: Box<Vec<Foo>>,
56 "usage of `Box<Vec<T>>`, vector elements are already on the heap"
59 declare_clippy_lint! {
60 /// **What it does:** Checks for use of `Vec<Box<T>>` where T: Sized anywhere in the code.
62 /// **Why is this bad?** `Vec` already keeps its contents in a separate area on
63 /// the heap. So if you `Box` its contents, you just add another level of indirection.
65 /// **Known problems:** Vec<Box<T: Sized>> makes sense if T is a large type (see #3530,
71 /// values: Vec<Box<i32>>,
84 "usage of `Vec<Box<T>>` where T: Sized, vector elements are already on the heap"
87 declare_clippy_lint! {
88 /// **What it does:** Checks for use of `Option<Option<_>>` in function signatures and type
91 /// **Why is this bad?** `Option<_>` represents an optional value. `Option<Option<_>>`
92 /// represents an optional optional value which is logically the same thing as an optional
93 /// value but has an unneeded extra level of wrapping.
95 /// **Known problems:** None.
99 /// fn x() -> Option<Option<u32>> {
105 "usage of `Option<Option<T>>`"
108 declare_clippy_lint! {
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 /// # use std::collections::LinkedList;
137 /// let x: LinkedList<usize> = LinkedList::new();
141 "usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque"
144 declare_clippy_lint! {
145 /// **What it does:** Checks for use of `&Box<T>` anywhere in the code.
147 /// **Why is this bad?** Any `&Box<T>` can also be a `&T`, which is more
150 /// **Known problems:** None.
154 /// fn foo(bar: &Box<T>) { ... }
160 /// fn foo(bar: &T) { ... }
164 "a borrow of a boxed type"
167 declare_lint_pass!(Types => [BOX_VEC, VEC_BOX, OPTION_OPTION, LINKEDLIST, BORROWED_BOX]);
169 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Types {
170 fn check_fn(&mut self, cx: &LateContext<'_, '_>, _: FnKind<'_>, decl: &FnDecl, _: &Body, _: Span, id: HirId) {
171 // Skip trait implementations; see issue #605.
172 if let Some(hir::Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
173 if let ItemKind::Impl(_, _, _, _, Some(..), _, _) = item.node {
178 check_fn_decl(cx, decl);
181 fn check_struct_field(&mut self, cx: &LateContext<'_, '_>, field: &hir::StructField) {
182 check_ty(cx, &field.ty, false);
185 fn check_trait_item(&mut self, cx: &LateContext<'_, '_>, item: &TraitItem) {
187 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => check_ty(cx, ty, false),
188 TraitItemKind::Method(ref sig, _) => check_fn_decl(cx, &sig.decl),
193 fn check_local(&mut self, cx: &LateContext<'_, '_>, local: &Local) {
194 if let Some(ref ty) = local.ty {
195 check_ty(cx, ty, true);
200 fn check_fn_decl(cx: &LateContext<'_, '_>, decl: &FnDecl) {
201 for input in &decl.inputs {
202 check_ty(cx, input, false);
205 if let FunctionRetTy::Return(ref ty) = decl.output {
206 check_ty(cx, ty, false);
210 /// Checks if `qpath` has last segment with type parameter matching `path`
211 fn match_type_parameter(cx: &LateContext<'_, '_>, qpath: &QPath, path: &[&str]) -> bool {
212 let last = last_path_segment(qpath);
214 if let Some(ref params) = last.args;
215 if !params.parenthesized;
216 if let Some(ty) = params.args.iter().find_map(|arg| match arg {
217 GenericArg::Type(ty) => Some(ty),
220 if let TyKind::Path(ref qpath) = ty.node;
221 if let Some(did) = cx.tables.qpath_res(qpath, ty.hir_id).opt_def_id();
222 if match_def_path(cx, did, path);
230 /// Recursively check for `TypePass` lints in the given type. Stop at the first
233 /// The parameter `is_local` distinguishes the context of the type; types from
234 /// local bindings should only be checked for the `BORROWED_BOX` lint.
235 #[allow(clippy::too_many_lines)]
236 fn check_ty(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool) {
237 if hir_ty.span.from_expansion() {
241 TyKind::Path(ref qpath) if !is_local => {
242 let hir_id = hir_ty.hir_id;
243 let res = cx.tables.qpath_res(qpath, hir_id);
244 if let Some(def_id) = res.opt_def_id() {
245 if Some(def_id) == cx.tcx.lang_items().owned_box() {
246 if match_type_parameter(cx, qpath, &paths::VEC) {
251 "you seem to be trying to use `Box<Vec<T>>`. Consider using just `Vec<T>`",
252 "`Vec<T>` is already on the heap, `Box<Vec<T>>` makes an extra allocation.",
254 return; // don't recurse into the type
256 } else if cx.tcx.is_diagnostic_item(Symbol::intern("vec_type"), def_id) {
258 // Get the _ part of Vec<_>
259 if let Some(ref last) = last_path_segment(qpath).args;
260 if let Some(ty) = last.args.iter().find_map(|arg| match arg {
261 GenericArg::Type(ty) => Some(ty),
264 // ty is now _ at this point
265 if let TyKind::Path(ref ty_qpath) = ty.node;
266 let res = cx.tables.qpath_res(ty_qpath, ty.hir_id);
267 if let Some(def_id) = res.opt_def_id();
268 if Some(def_id) == cx.tcx.lang_items().owned_box();
269 // At this point, we know ty is Box<T>, now get T
270 if let Some(ref last) = last_path_segment(ty_qpath).args;
271 if let Some(boxed_ty) = last.args.iter().find_map(|arg| match arg {
272 GenericArg::Type(ty) => Some(ty),
276 let ty_ty = hir_ty_to_ty(cx.tcx, boxed_ty);
277 if ty_ty.is_sized(cx.tcx.at(ty.span), cx.param_env) {
282 "`Vec<T>` is already on the heap, the boxing is unnecessary.",
284 format!("Vec<{}>", ty_ty),
285 Applicability::MachineApplicable,
287 return; // don't recurse into the type
291 } else if match_def_path(cx, def_id, &paths::OPTION) {
292 if match_type_parameter(cx, qpath, &paths::OPTION) {
297 "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
298 enum if you need to distinguish all 3 cases",
300 return; // don't recurse into the type
302 } else if match_def_path(cx, def_id, &paths::LINKED_LIST) {
307 "I see you're using a LinkedList! Perhaps you meant some other data structure?",
308 "a VecDeque might work",
310 return; // don't recurse into the type
314 QPath::Resolved(Some(ref ty), ref p) => {
315 check_ty(cx, ty, is_local);
316 for ty in p.segments.iter().flat_map(|seg| {
319 .map_or_else(|| [].iter(), |params| params.args.iter())
320 .filter_map(|arg| match arg {
321 GenericArg::Type(ty) => Some(ty),
325 check_ty(cx, ty, is_local);
328 QPath::Resolved(None, ref p) => {
329 for ty in p.segments.iter().flat_map(|seg| {
332 .map_or_else(|| [].iter(), |params| params.args.iter())
333 .filter_map(|arg| match arg {
334 GenericArg::Type(ty) => Some(ty),
338 check_ty(cx, ty, is_local);
341 QPath::TypeRelative(ref ty, ref seg) => {
342 check_ty(cx, ty, is_local);
343 if let Some(ref params) = seg.args {
344 for ty in params.args.iter().filter_map(|arg| match arg {
345 GenericArg::Type(ty) => Some(ty),
348 check_ty(cx, ty, is_local);
354 TyKind::Rptr(ref lt, ref mut_ty) => check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),
356 TyKind::Slice(ref ty) | TyKind::Array(ref ty, _) | TyKind::Ptr(MutTy { ref ty, .. }) => {
357 check_ty(cx, ty, is_local)
359 TyKind::Tup(ref tys) => {
361 check_ty(cx, ty, is_local);
368 fn check_ty_rptr(cx: &LateContext<'_, '_>, hir_ty: &hir::Ty, is_local: bool, lt: &Lifetime, mut_ty: &MutTy) {
369 match mut_ty.ty.node {
370 TyKind::Path(ref qpath) => {
371 let hir_id = mut_ty.ty.hir_id;
372 let def = cx.tables.qpath_res(qpath, hir_id);
374 if let Some(def_id) = def.opt_def_id();
375 if Some(def_id) == cx.tcx.lang_items().owned_box();
376 if let QPath::Resolved(None, ref path) = *qpath;
377 if let [ref bx] = *path.segments;
378 if let Some(ref params) = bx.args;
379 if !params.parenthesized;
380 if let Some(inner) = params.args.iter().find_map(|arg| match arg {
381 GenericArg::Type(ty) => Some(ty),
385 if is_any_trait(inner) {
386 // Ignore `Box<Any>` types; see issue #1884 for details.
390 let ltopt = if lt.is_elided() {
393 format!("{} ", lt.name.ident().as_str())
395 let mutopt = if mut_ty.mutbl == Mutability::MutMutable {
400 let mut applicability = Applicability::MachineApplicable;
405 "you seem to be trying to use `&Box<T>`. Consider using just `&T`",
411 &snippet_with_applicability(cx, inner.span, "..", &mut applicability)
413 Applicability::Unspecified,
415 return; // don't recurse into the type
418 check_ty(cx, &mut_ty.ty, is_local);
420 _ => check_ty(cx, &mut_ty.ty, is_local),
424 // Returns true if given type is `Any` trait.
425 fn is_any_trait(t: &hir::Ty) -> bool {
427 if let TyKind::TraitObject(ref traits, _) = t.node;
428 if traits.len() >= 1;
429 // Only Send/Sync can be used as additional traits, so it is enough to
430 // check only the first trait.
431 if match_path(&traits[0].trait_ref.path, &paths::ANY_TRAIT);
440 declare_clippy_lint! {
441 /// **What it does:** Checks for binding a unit value.
443 /// **Why is this bad?** A unit value cannot usefully be used anywhere. So
444 /// binding one is kind of pointless.
446 /// **Known problems:** None.
456 "creating a let binding to a value of unit type, which usually can't be used afterwards"
459 declare_lint_pass!(LetUnitValue => [LET_UNIT_VALUE]);
461 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LetUnitValue {
462 fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) {
463 if let StmtKind::Local(ref local) = stmt.node {
464 if is_unit(cx.tables.pat_ty(&local.pat)) {
465 if in_external_macro(cx.sess(), stmt.span) || local.pat.span.from_expansion() {
468 if higher::is_from_for_desugar(local) {
471 span_lint_and_then(cx, LET_UNIT_VALUE, stmt.span, "this let-binding has unit value", |db| {
472 if let Some(expr) = &local.init {
473 let snip = snippet_with_macro_callsite(cx, expr.span, "()");
476 "omit the `let` binding",
477 format!("{};", snip),
478 Applicability::MachineApplicable, // snippet
487 declare_clippy_lint! {
488 /// **What it does:** Checks for comparisons to unit.
490 /// **Why is this bad?** Unit is always equal to itself, and thus is just a
491 /// clumsily written constant. Mostly this happens when someone accidentally
492 /// adds semicolons at the end of the operands.
494 /// **Known problems:** None.
522 "comparing unit values"
525 declare_lint_pass!(UnitCmp => [UNIT_CMP]);
527 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitCmp {
528 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
529 if expr.span.from_expansion() {
532 if let ExprKind::Binary(ref cmp, ref left, _) = expr.node {
534 if op.is_comparison() && is_unit(cx.tables.expr_ty(left)) {
535 let result = match op {
536 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
544 "{}-comparison of unit values detected. This will always be {}",
554 declare_clippy_lint! {
555 /// **What it does:** Checks for passing a unit value as an argument to a function without using a
556 /// unit literal (`()`).
558 /// **Why is this bad?** This is likely the result of an accidental semicolon.
560 /// **Known problems:** None.
571 "passing unit to a function"
574 declare_lint_pass!(UnitArg => [UNIT_ARG]);
576 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnitArg {
577 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
578 if expr.span.from_expansion() {
582 // apparently stuff in the desugaring of `?` can trigger this
583 // so check for that here
584 // only the calls to `Try::from_error` is marked as desugared,
585 // so we need to check both the current Expr and its parent.
586 if is_questionmark_desugar_marked_call(expr) {
590 let map = &cx.tcx.hir();
591 let opt_parent_node = map.find(map.get_parent_node(expr.hir_id));
592 if let Some(hir::Node::Expr(parent_expr)) = opt_parent_node;
593 if is_questionmark_desugar_marked_call(parent_expr);
600 ExprKind::Call(_, ref args) | ExprKind::MethodCall(_, _, ref args) => {
602 if is_unit(cx.tables.expr_ty(arg)) && !is_unit_literal(arg) {
603 if let ExprKind::Match(.., match_source) = &arg.node {
604 if *match_source == MatchSource::TryDesugar {
613 "passing a unit value to a function",
614 "if you intended to pass a unit value, use a unit literal instead",
616 Applicability::MachineApplicable,
626 fn is_questionmark_desugar_marked_call(expr: &Expr) -> bool {
627 use syntax_pos::hygiene::DesugaringKind;
628 if let ExprKind::Call(ref callee, _) = expr.node {
629 callee.span.is_desugaring(DesugaringKind::QuestionMark)
635 fn is_unit(ty: Ty<'_>) -> bool {
637 ty::Tuple(slice) if slice.is_empty() => true,
642 fn is_unit_literal(expr: &Expr) -> bool {
644 ExprKind::Tup(ref slice) if slice.is_empty() => true,
649 declare_clippy_lint! {
650 /// **What it does:** Checks for casts from any numerical to a float type where
651 /// the receiving type cannot store all values from the original type without
652 /// rounding errors. This possible rounding is to be expected, so this lint is
653 /// `Allow` by default.
655 /// Basically, this warns on casting any integer with 32 or more bits to `f32`
656 /// or any 64-bit integer to `f64`.
658 /// **Why is this bad?** It's not bad at all. But in some applications it can be
659 /// helpful to know where precision loss can take place. This lint can help find
660 /// those places in the code.
662 /// **Known problems:** None.
666 /// let x = std::u64::MAX;
669 pub CAST_PRECISION_LOSS,
671 "casts that cause loss of precision, e.g., `x as f32` where `x: u64`"
674 declare_clippy_lint! {
675 /// **What it does:** Checks for casts from a signed to an unsigned numerical
676 /// type. In this case, negative values wrap around to large positive values,
677 /// which can be quite surprising in practice. However, as the cast works as
678 /// defined, this lint is `Allow` by default.
680 /// **Why is this bad?** Possibly surprising results. You can activate this lint
681 /// as a one-time check to see where numerical wrapping can arise.
683 /// **Known problems:** None.
688 /// y as u128; // will return 18446744073709551615
692 "casts from signed types to unsigned types, e.g., `x as u32` where `x: i32`"
695 declare_clippy_lint! {
696 /// **What it does:** Checks for casts between numerical types that may
697 /// truncate large values. This is expected behavior, so the cast is `Allow` by
700 /// **Why is this bad?** In some problem domains, it is good practice to avoid
701 /// truncation. This lint can be activated to help assess where additional
702 /// checks could be beneficial.
704 /// **Known problems:** None.
708 /// fn as_u8(x: u64) -> u8 {
712 pub CAST_POSSIBLE_TRUNCATION,
714 "casts that may cause truncation of the value, e.g., `x as u8` where `x: u32`, or `x as i32` where `x: f32`"
717 declare_clippy_lint! {
718 /// **What it does:** Checks for casts from an unsigned type to a signed type of
719 /// the same size. Performing such a cast is a 'no-op' for the compiler,
720 /// i.e., nothing is changed at the bit level, and the binary representation of
721 /// the value is reinterpreted. This can cause wrapping if the value is too big
722 /// for the target signed type. However, the cast works as defined, so this lint
723 /// is `Allow` by default.
725 /// **Why is this bad?** While such a cast is not bad in itself, the results can
726 /// be surprising when this is not the intended behavior, as demonstrated by the
729 /// **Known problems:** None.
733 /// std::u32::MAX as i32; // will yield a value of `-1`
735 pub CAST_POSSIBLE_WRAP,
737 "casts that may cause wrapping around the value, e.g., `x as i32` where `x: u32` and `x > i32::MAX`"
740 declare_clippy_lint! {
741 /// **What it does:** Checks for casts between numerical types that may
742 /// be replaced by safe conversion functions.
744 /// **Why is this bad?** Rust's `as` keyword will perform many kinds of
745 /// conversions, including silently lossy conversions. Conversion functions such
746 /// as `i32::from` will only perform lossless conversions. Using the conversion
747 /// functions prevents conversions from turning into silent lossy conversions if
748 /// the types of the input expressions ever change, and make it easier for
749 /// people reading the code to know that the conversion is lossless.
751 /// **Known problems:** None.
755 /// fn as_u64(x: u8) -> u64 {
760 /// Using `::from` would look like this:
763 /// fn as_u64(x: u8) -> u64 {
769 "casts using `as` that are known to be lossless, e.g., `x as u64` where `x: u8`"
772 declare_clippy_lint! {
773 /// **What it does:** Checks for casts to the same type.
775 /// **Why is this bad?** It's just unnecessary.
777 /// **Known problems:** None.
781 /// let _ = 2i32 as i32;
783 pub UNNECESSARY_CAST,
785 "cast to the same type, e.g., `x as i32` where `x: i32`"
788 declare_clippy_lint! {
789 /// **What it does:** Checks for casts from a less-strictly-aligned pointer to a
790 /// more-strictly-aligned pointer
792 /// **Why is this bad?** Dereferencing the resulting pointer may be undefined
795 /// **Known problems:** Using `std::ptr::read_unaligned` and `std::ptr::write_unaligned` or similar
796 /// on the resulting pointer is fine.
800 /// let _ = (&1u8 as *const u8) as *const u16;
801 /// let _ = (&mut 1u8 as *mut u8) as *mut u16;
803 pub CAST_PTR_ALIGNMENT,
805 "cast from a pointer to a more-strictly-aligned pointer"
808 declare_clippy_lint! {
809 /// **What it does:** Checks for casts of function pointers to something other than usize
811 /// **Why is this bad?**
812 /// Casting a function pointer to anything other than usize/isize is not portable across
813 /// architectures, because you end up losing bits if the target type is too small or end up with a
814 /// bunch of extra bits that waste space and add more instructions to the final binary than
815 /// strictly necessary for the problem
817 /// Casting to isize also doesn't make sense since there are no signed addresses.
823 /// fn fun() -> i32 { 1 }
824 /// let a = fun as i64;
827 /// fn fun2() -> i32 { 1 }
828 /// let a = fun2 as usize;
830 pub FN_TO_NUMERIC_CAST,
832 "casting a function pointer to a numeric type other than usize"
835 declare_clippy_lint! {
836 /// **What it does:** Checks for casts of a function pointer to a numeric type not wide enough to
839 /// **Why is this bad?**
840 /// Such a cast discards some bits of the function's address. If this is intended, it would be more
841 /// clearly expressed by casting to usize first, then casting the usize to the intended type (with
842 /// a comment) to perform the truncation.
848 /// fn fn1() -> i16 {
851 /// let _ = fn1 as i32;
853 /// // Better: Cast to usize first, then comment with the reason for the truncation
854 /// fn fn2() -> i16 {
857 /// let fn_ptr = fn2 as usize;
858 /// let fn_ptr_truncated = fn_ptr as i32;
860 pub FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
862 "casting a function pointer to a numeric type not wide enough to store the address"
865 /// Returns the size in bits of an integral type.
866 /// Will return 0 if the type is not an int or uint variant
867 fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
869 ty::Int(i) => match i {
870 IntTy::Isize => tcx.data_layout.pointer_size.bits(),
877 ty::Uint(i) => match i {
878 UintTy::Usize => tcx.data_layout.pointer_size.bits(),
889 fn is_isize_or_usize(typ: Ty<'_>) -> bool {
891 ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => true,
896 fn span_precision_loss_lint(cx: &LateContext<'_, '_>, expr: &Expr, cast_from: Ty<'_>, cast_to_f64: bool) {
897 let mantissa_nbits = if cast_to_f64 { 52 } else { 23 };
898 let arch_dependent = is_isize_or_usize(cast_from) && cast_to_f64;
899 let arch_dependent_str = "on targets with 64-bit wide pointers ";
900 let from_nbits_str = if arch_dependent {
902 } else if is_isize_or_usize(cast_from) {
903 "32 or 64".to_owned()
905 int_ty_to_nbits(cast_from, cx.tcx).to_string()
912 "casting {0} to {1} causes a loss of precision {2}({0} is {3} bits wide, but {1}'s mantissa \
913 is only {4} bits wide)",
915 if cast_to_f64 { "f64" } else { "f32" },
916 if arch_dependent { arch_dependent_str } else { "" },
923 fn should_strip_parens(op: &Expr, snip: &str) -> bool {
924 if let ExprKind::Binary(_, _, _) = op.node {
925 if snip.starts_with('(') && snip.ends_with(')') {
932 fn span_lossless_lint(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
933 // Do not suggest using From in consts/statics until it is valid to do so (see #2267).
934 if in_constant(cx, expr.hir_id) {
937 // The suggestion is to use a function call, so if the original expression
938 // has parens on the outside, they are no longer needed.
939 let mut applicability = Applicability::MachineApplicable;
940 let opt = snippet_opt(cx, op.span);
941 let sugg = if let Some(ref snip) = opt {
942 if should_strip_parens(op, snip) {
943 &snip[1..snip.len() - 1]
948 applicability = Applicability::HasPlaceholders;
957 "casting {} to {} may become silently lossy if you later change the type",
961 format!("{}::from({})", cast_to, sugg),
972 fn check_loss_of_sign(cx: &LateContext<'_, '_>, expr: &Expr, op: &Expr, cast_from: Ty<'_>, cast_to: Ty<'_>) {
973 if !cast_from.is_signed() || cast_to.is_signed() {
977 // don't lint for positive constants
978 let const_val = constant(cx, &cx.tables, op);
980 if let Some((const_val, _)) = const_val;
981 if let Constant::Int(n) = const_val;
982 if let ty::Int(ity) = cast_from.sty;
983 if sext(cx.tcx, n, ity) >= 0;
993 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
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 declare_lint_pass!(Casts => [
1079 CAST_PRECISION_LOSS,
1081 CAST_POSSIBLE_TRUNCATION,
1087 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1090 // Check if the given type is either `core::ffi::c_void` or
1091 // one of the platform specific `libc::<platform>::c_void` of libc.
1092 fn is_c_void(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
1093 if let ty::Adt(adt, _) = ty.sty {
1094 let names = cx.get_def_path(adt.did);
1096 if names.is_empty() {
1099 if names[0] == sym!(libc) || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
1106 /// Returns the mantissa bits wide of a fp type.
1107 /// Will return 0 if the type is not a fp
1108 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
1110 ty::Float(FloatTy::F32) => 23,
1111 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
1116 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
1117 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1118 if expr.span.from_expansion() {
1121 if let ExprKind::Cast(ref ex, _) = expr.node {
1122 let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
1123 lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
1124 if let ExprKind::Lit(ref lit) = ex.node {
1125 if let LitKind::Int(n, _) = lit.node {
1126 if cast_to.is_floating_point() {
1127 let from_nbits = 128 - n.leading_zeros();
1128 let to_nbits = fp_ty_mantissa_nbits(cast_to);
1129 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
1134 &format!("casting integer literal to {} is unnecessary", cast_to),
1136 format!("{}_{}", n, cast_to),
1137 Applicability::MachineApplicable,
1144 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::FloatUnsuffixed(_) => {},
1146 if cast_from.sty == cast_to.sty && !in_external_macro(cx.sess(), expr.span) {
1152 "casting to the same type is unnecessary (`{}` -> `{}`)",
1160 if cast_from.is_numeric() && cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
1161 lint_numeric_casts(cx, expr, ex, cast_from, cast_to);
1164 lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
1169 fn lint_numeric_casts<'tcx>(
1170 cx: &LateContext<'_, 'tcx>,
1173 cast_from: Ty<'tcx>,
1176 match (cast_from.is_integral(), cast_to.is_integral()) {
1178 let from_nbits = int_ty_to_nbits(cast_from, cx.tcx);
1179 let to_nbits = if let ty::Float(FloatTy::F32) = cast_to.sty {
1184 if is_isize_or_usize(cast_from) || from_nbits >= to_nbits {
1185 span_precision_loss_lint(cx, expr, cast_from, to_nbits == 64);
1187 if from_nbits < to_nbits {
1188 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1194 CAST_POSSIBLE_TRUNCATION,
1196 &format!("casting {} to {} may truncate the value", cast_from, cast_to),
1198 if !cast_to.is_signed() {
1203 &format!("casting {} to {} may lose the sign of the value", cast_from, cast_to),
1208 check_loss_of_sign(cx, expr, cast_expr, cast_from, cast_to);
1209 check_truncation_and_wrapping(cx, expr, cast_from, cast_to);
1210 check_lossless(cx, expr, cast_expr, cast_from, cast_to);
1213 if let (&ty::Float(FloatTy::F64), &ty::Float(FloatTy::F32)) = (&cast_from.sty, &cast_to.sty) {
1216 CAST_POSSIBLE_TRUNCATION,
1218 "casting f64 to f32 may truncate the value",
1221 if let (&ty::Float(FloatTy::F32), &ty::Float(FloatTy::F64)) = (&cast_from.sty, &cast_to.sty) {
1222 span_lossless_lint(cx, expr, cast_expr, cast_from, cast_to);
1228 fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
1230 if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
1231 if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
1232 if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
1233 if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
1234 if from_layout.align.abi < to_layout.align.abi;
1235 // with c_void, we inherently need to trust the user
1236 if !is_c_void(cx, from_ptr_ty.ty);
1237 // when casting from a ZST, we don't know enough to properly lint
1238 if !from_layout.is_zst();
1245 "casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
1248 from_layout.align.abi.bytes(),
1249 to_layout.align.abi.bytes(),
1256 fn lint_fn_to_numeric_cast(
1257 cx: &LateContext<'_, '_>,
1263 // We only want to check casts to `ty::Uint` or `ty::Int`
1265 ty::Uint(_) | ty::Int(..) => { /* continue on */ },
1268 match cast_from.sty {
1269 ty::FnDef(..) | ty::FnPtr(_) => {
1270 let mut applicability = Applicability::MaybeIncorrect;
1271 let from_snippet = snippet_with_applicability(cx, cast_expr.span, "x", &mut applicability);
1273 let to_nbits = int_ty_to_nbits(cast_to, cx.tcx);
1274 if to_nbits < cx.tcx.data_layout.pointer_size.bits() {
1277 FN_TO_NUMERIC_CAST_WITH_TRUNCATION,
1280 "casting function pointer `{}` to `{}`, which truncates the value",
1281 from_snippet, cast_to
1284 format!("{} as usize", from_snippet),
1287 } else if cast_to.sty != ty::Uint(UintTy::Usize) {
1292 &format!("casting function pointer `{}` to `{}`", from_snippet, cast_to),
1294 format!("{} as usize", from_snippet),
1303 declare_clippy_lint! {
1304 /// **What it does:** Checks for types used in structs, parameters and `let`
1305 /// declarations above a certain complexity threshold.
1307 /// **Why is this bad?** Too complex types make the code less readable. Consider
1308 /// using a `type` definition to simplify them.
1310 /// **Known problems:** None.
1314 /// # use std::rc::Rc;
1316 /// inner: Rc<Vec<Vec<Box<(u32, u32, u32, u32)>>>>,
1319 pub TYPE_COMPLEXITY,
1321 "usage of very complex types that might be better factored into `type` definitions"
1324 pub struct TypeComplexity {
1328 impl TypeComplexity {
1329 pub fn new(threshold: u64) -> Self {
1334 impl_lint_pass!(TypeComplexity => [TYPE_COMPLEXITY]);
1336 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeComplexity {
1339 cx: &LateContext<'a, 'tcx>,
1346 self.check_fndecl(cx, decl);
1349 fn check_struct_field(&mut self, cx: &LateContext<'a, 'tcx>, field: &'tcx hir::StructField) {
1350 // enum variants are also struct fields now
1351 self.check_type(cx, &field.ty);
1354 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1356 ItemKind::Static(ref ty, _, _) | ItemKind::Const(ref ty, _) => self.check_type(cx, ty),
1357 // functions, enums, structs, impls and traits are covered
1362 fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
1364 TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => self.check_type(cx, ty),
1365 TraitItemKind::Method(MethodSig { ref decl, .. }, TraitMethod::Required(_)) => self.check_fndecl(cx, decl),
1366 // methods with default impl are covered by check_fn
1371 fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) {
1373 ImplItemKind::Const(ref ty, _) | ImplItemKind::TyAlias(ref ty) => self.check_type(cx, ty),
1374 // methods are covered by check_fn
1379 fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
1380 if let Some(ref ty) = local.ty {
1381 self.check_type(cx, ty);
1386 impl<'a, 'tcx> TypeComplexity {
1387 fn check_fndecl(&self, cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl) {
1388 for arg in &decl.inputs {
1389 self.check_type(cx, arg);
1391 if let Return(ref ty) = decl.output {
1392 self.check_type(cx, ty);
1396 fn check_type(&self, cx: &LateContext<'_, '_>, ty: &hir::Ty) {
1397 if ty.span.from_expansion() {
1401 let mut visitor = TypeComplexityVisitor { score: 0, nest: 1 };
1402 visitor.visit_ty(ty);
1406 if score > self.threshold {
1411 "very complex type used. Consider factoring parts into `type` definitions",
1417 /// Walks a type and assigns a complexity score to it.
1418 struct TypeComplexityVisitor {
1419 /// total complexity score of the type
1421 /// current nesting level
1425 impl<'tcx> Visitor<'tcx> for TypeComplexityVisitor {
1426 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
1427 let (add_score, sub_nest) = match ty.node {
1428 // _, &x and *x have only small overhead; don't mess with nesting level
1429 TyKind::Infer | TyKind::Ptr(..) | TyKind::Rptr(..) => (1, 0),
1431 // the "normal" components of a type: named types, arrays/tuples
1432 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Tup(..) | TyKind::Array(..) => (10 * self.nest, 1),
1434 // function types bring a lot of overhead
1435 TyKind::BareFn(ref bare) if bare.abi == Abi::Rust => (50 * self.nest, 1),
1437 TyKind::TraitObject(ref param_bounds, _) => {
1438 let has_lifetime_parameters = param_bounds.iter().any(|bound| {
1439 bound.bound_generic_params.iter().any(|gen| match gen.kind {
1440 GenericParamKind::Lifetime { .. } => true,
1444 if has_lifetime_parameters {
1445 // complex trait bounds like A<'a, 'b>
1448 // simple trait bounds like A + B
1455 self.score += add_score;
1456 self.nest += sub_nest;
1458 self.nest -= sub_nest;
1460 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1461 NestedVisitorMap::None
1465 declare_clippy_lint! {
1466 /// **What it does:** Checks for expressions where a character literal is cast
1467 /// to `u8` and suggests using a byte literal instead.
1469 /// **Why is this bad?** In general, casting values to smaller types is
1470 /// error-prone and should be avoided where possible. In the particular case of
1471 /// converting a character literal to u8, it is easy to avoid by just using a
1472 /// byte literal instead. As an added bonus, `b'a'` is even slightly shorter
1473 /// than `'a' as u8`.
1475 /// **Known problems:** None.
1482 /// A better version, using the byte literal:
1489 "casting a character literal to u8 truncates"
1492 declare_lint_pass!(CharLitAsU8 => [CHAR_LIT_AS_U8]);
1494 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CharLitAsU8 {
1495 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1497 if !expr.span.from_expansion();
1498 if let ExprKind::Cast(e, _) = &expr.node;
1499 if let ExprKind::Lit(l) = &e.node;
1500 if let LitKind::Char(c) = l.node;
1501 if ty::Uint(UintTy::U8) == cx.tables.expr_ty(expr).sty;
1503 let mut applicability = Applicability::MachineApplicable;
1504 let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability);
1510 "casting a character literal to `u8` truncates",
1512 db.note("`char` is four bytes wide, but `u8` is a single byte");
1517 "use a byte literal instead",
1518 format!("b{}", snippet),
1528 declare_clippy_lint! {
1529 /// **What it does:** Checks for comparisons where one side of the relation is
1530 /// either the minimum or maximum value for its type and warns if it involves a
1531 /// case that is always true or always false. Only integer and boolean types are
1534 /// **Why is this bad?** An expression like `min <= x` may misleadingly imply
1535 /// that it is possible for `x` to be less than the minimum. Expressions like
1536 /// `max < x` are probably mistakes.
1538 /// **Known problems:** For `usize` the size of the current compile target will
1539 /// be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
1540 /// a comparison to detect target pointer width will trigger this lint. One can
1541 /// use `mem::sizeof` and compare its value or conditional compilation
1543 /// like `#[cfg(target_pointer_width = "64")] ..` instead.
1548 /// let vec: Vec<isize> = vec![];
1549 /// if vec.len() <= 0 {}
1550 /// if 100 > std::i32::MAX {}
1552 pub ABSURD_EXTREME_COMPARISONS,
1554 "a comparison with a maximum or minimum value that is always true or false"
1557 declare_lint_pass!(AbsurdExtremeComparisons => [ABSURD_EXTREME_COMPARISONS]);
1564 struct ExtremeExpr<'a> {
1569 enum AbsurdComparisonResult {
1572 InequalityImpossible,
1575 fn is_cast_between_fixed_and_target<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> bool {
1576 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1577 let precast_ty = cx.tables.expr_ty(cast_exp);
1578 let cast_ty = cx.tables.expr_ty(expr);
1580 return is_isize_or_usize(precast_ty) != is_isize_or_usize(cast_ty);
1586 fn detect_absurd_comparison<'a, 'tcx>(
1587 cx: &LateContext<'a, 'tcx>,
1591 ) -> Option<(ExtremeExpr<'tcx>, AbsurdComparisonResult)> {
1592 use crate::types::AbsurdComparisonResult::*;
1593 use crate::types::ExtremeType::*;
1594 use crate::utils::comparisons::*;
1596 // absurd comparison only makes sense on primitive types
1597 // primitive types don't implement comparison operators with each other
1598 if cx.tables.expr_ty(lhs) != cx.tables.expr_ty(rhs) {
1602 // comparisons between fix sized types and target sized types are considered unanalyzable
1603 if is_cast_between_fixed_and_target(cx, lhs) || is_cast_between_fixed_and_target(cx, rhs) {
1607 let normalized = normalize_comparison(op, lhs, rhs);
1608 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1614 let lx = detect_extreme_expr(cx, normalized_lhs);
1615 let rx = detect_extreme_expr(cx, normalized_rhs);
1620 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, AlwaysFalse), // max < x
1621 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, AlwaysFalse), // x < min
1627 (Some(l @ ExtremeExpr { which: Minimum, .. }), _) => (l, AlwaysTrue), // min <= x
1628 (Some(l @ ExtremeExpr { which: Maximum, .. }), _) => (l, InequalityImpossible), // max <= x
1629 (_, Some(r @ ExtremeExpr { which: Minimum, .. })) => (r, InequalityImpossible), // x <= min
1630 (_, Some(r @ ExtremeExpr { which: Maximum, .. })) => (r, AlwaysTrue), // x <= max
1634 Rel::Ne | Rel::Eq => return None,
1638 fn detect_extreme_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<ExtremeExpr<'tcx>> {
1639 use crate::types::ExtremeType::*;
1641 let ty = cx.tables.expr_ty(expr);
1643 let cv = constant(cx, cx.tables, expr)?.0;
1645 let which = match (&ty.sty, cv) {
1646 (&ty::Bool, Constant::Bool(false)) | (&ty::Uint(_), Constant::Int(0)) => Minimum,
1647 (&ty::Int(ity), Constant::Int(i))
1648 if i == unsext(cx.tcx, i128::min_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1653 (&ty::Bool, Constant::Bool(true)) => Maximum,
1654 (&ty::Int(ity), Constant::Int(i))
1655 if i == unsext(cx.tcx, i128::max_value() >> (128 - int_bits(cx.tcx, ity)), ity) =>
1659 (&ty::Uint(uty), Constant::Int(i)) if clip(cx.tcx, u128::max_value(), uty) == i => Maximum,
1663 Some(ExtremeExpr { which, expr })
1666 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AbsurdExtremeComparisons {
1667 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1668 use crate::types::AbsurdComparisonResult::*;
1669 use crate::types::ExtremeType::*;
1671 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1672 if let Some((culprit, result)) = detect_absurd_comparison(cx, cmp.node, lhs, rhs) {
1673 if !expr.span.from_expansion() {
1674 let msg = "this comparison involving the minimum or maximum element for this \
1675 type contains a case that is always true or always false";
1677 let conclusion = match result {
1678 AlwaysFalse => "this comparison is always false".to_owned(),
1679 AlwaysTrue => "this comparison is always true".to_owned(),
1680 InequalityImpossible => format!(
1681 "the case where the two sides are not equal never occurs, consider using {} == {} \
1683 snippet(cx, lhs.span, "lhs"),
1684 snippet(cx, rhs.span, "rhs")
1689 "because {} is the {} value for this type, {}",
1690 snippet(cx, culprit.expr.span, "x"),
1691 match culprit.which {
1692 Minimum => "minimum",
1693 Maximum => "maximum",
1698 span_help_and_lint(cx, ABSURD_EXTREME_COMPARISONS, expr.span, msg, &help);
1705 declare_clippy_lint! {
1706 /// **What it does:** Checks for comparisons where the relation is always either
1707 /// true or false, but where one side has been upcast so that the comparison is
1708 /// necessary. Only integer types are checked.
1710 /// **Why is this bad?** An expression like `let x : u8 = ...; (x as u32) > 300`
1711 /// will mistakenly imply that it is possible for `x` to be outside the range of
1714 /// **Known problems:**
1715 /// https://github.com/rust-lang/rust-clippy/issues/886
1720 /// (x as u32) > 300;
1722 pub INVALID_UPCAST_COMPARISONS,
1724 "a comparison involving an upcast which is always true or false"
1727 declare_lint_pass!(InvalidUpcastComparisons => [INVALID_UPCAST_COMPARISONS]);
1729 #[derive(Copy, Clone, Debug, Eq)]
1736 #[allow(clippy::cast_sign_loss)]
1737 fn cmp_s_u(s: i128, u: u128) -> Ordering {
1740 } else if u > (i128::max_value() as u128) {
1748 impl PartialEq for FullInt {
1749 fn eq(&self, other: &Self) -> bool {
1750 self.partial_cmp(other).expect("partial_cmp only returns Some(_)") == Ordering::Equal
1754 impl PartialOrd for FullInt {
1755 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
1756 Some(match (self, other) {
1757 (&Self::S(s), &Self::S(o)) => s.cmp(&o),
1758 (&Self::U(s), &Self::U(o)) => s.cmp(&o),
1759 (&Self::S(s), &Self::U(o)) => Self::cmp_s_u(s, o),
1760 (&Self::U(s), &Self::S(o)) => Self::cmp_s_u(o, s).reverse(),
1764 impl Ord for FullInt {
1765 fn cmp(&self, other: &Self) -> Ordering {
1766 self.partial_cmp(other)
1767 .expect("partial_cmp for FullInt can never return None")
1771 fn numeric_cast_precast_bounds<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(FullInt, FullInt)> {
1774 if let ExprKind::Cast(ref cast_exp, _) = expr.node {
1775 let pre_cast_ty = cx.tables.expr_ty(cast_exp);
1776 let cast_ty = cx.tables.expr_ty(expr);
1777 // if it's a cast from i32 to u32 wrapping will invalidate all these checks
1778 if cx.layout_of(pre_cast_ty).ok().map(|l| l.size) == cx.layout_of(cast_ty).ok().map(|l| l.size) {
1781 match pre_cast_ty.sty {
1782 ty::Int(int_ty) => Some(match int_ty {
1784 FullInt::S(i128::from(i8::min_value())),
1785 FullInt::S(i128::from(i8::max_value())),
1788 FullInt::S(i128::from(i16::min_value())),
1789 FullInt::S(i128::from(i16::max_value())),
1792 FullInt::S(i128::from(i32::min_value())),
1793 FullInt::S(i128::from(i32::max_value())),
1796 FullInt::S(i128::from(i64::min_value())),
1797 FullInt::S(i128::from(i64::max_value())),
1799 IntTy::I128 => (FullInt::S(i128::min_value()), FullInt::S(i128::max_value())),
1801 FullInt::S(isize::min_value() as i128),
1802 FullInt::S(isize::max_value() as i128),
1805 ty::Uint(uint_ty) => Some(match uint_ty {
1807 FullInt::U(u128::from(u8::min_value())),
1808 FullInt::U(u128::from(u8::max_value())),
1811 FullInt::U(u128::from(u16::min_value())),
1812 FullInt::U(u128::from(u16::max_value())),
1815 FullInt::U(u128::from(u32::min_value())),
1816 FullInt::U(u128::from(u32::max_value())),
1819 FullInt::U(u128::from(u64::min_value())),
1820 FullInt::U(u128::from(u64::max_value())),
1822 UintTy::U128 => (FullInt::U(u128::min_value()), FullInt::U(u128::max_value())),
1824 FullInt::U(usize::min_value() as u128),
1825 FullInt::U(usize::max_value() as u128),
1835 fn node_as_const_fullint<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<FullInt> {
1836 let val = constant(cx, cx.tables, expr)?.0;
1837 if let Constant::Int(const_int) = val {
1838 match cx.tables.expr_ty(expr).sty {
1839 ty::Int(ity) => Some(FullInt::S(sext(cx.tcx, const_int, ity))),
1840 ty::Uint(_) => Some(FullInt::U(const_int)),
1848 fn err_upcast_comparison(cx: &LateContext<'_, '_>, span: Span, expr: &Expr, always: bool) {
1849 if let ExprKind::Cast(ref cast_val, _) = expr.node {
1852 INVALID_UPCAST_COMPARISONS,
1855 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
1856 snippet(cx, cast_val.span, "the expression"),
1857 if always { "true" } else { "false" },
1863 fn upcast_comparison_bounds_err<'a, 'tcx>(
1864 cx: &LateContext<'a, 'tcx>,
1866 rel: comparisons::Rel,
1867 lhs_bounds: Option<(FullInt, FullInt)>,
1872 use crate::utils::comparisons::*;
1874 if let Some((lb, ub)) = lhs_bounds {
1875 if let Some(norm_rhs_val) = node_as_const_fullint(cx, rhs) {
1876 if rel == Rel::Eq || rel == Rel::Ne {
1877 if norm_rhs_val < lb || norm_rhs_val > ub {
1878 err_upcast_comparison(cx, span, lhs, rel == Rel::Ne);
1880 } else if match rel {
1895 Rel::Eq | Rel::Ne => unreachable!(),
1897 err_upcast_comparison(cx, span, lhs, true)
1898 } else if match rel {
1913 Rel::Eq | Rel::Ne => unreachable!(),
1915 err_upcast_comparison(cx, span, lhs, false)
1921 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InvalidUpcastComparisons {
1922 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
1923 if let ExprKind::Binary(ref cmp, ref lhs, ref rhs) = expr.node {
1924 let normalized = comparisons::normalize_comparison(cmp.node, lhs, rhs);
1925 let (rel, normalized_lhs, normalized_rhs) = if let Some(val) = normalized {
1931 let lhs_bounds = numeric_cast_precast_bounds(cx, normalized_lhs);
1932 let rhs_bounds = numeric_cast_precast_bounds(cx, normalized_rhs);
1934 upcast_comparison_bounds_err(cx, expr.span, rel, lhs_bounds, normalized_lhs, normalized_rhs, false);
1935 upcast_comparison_bounds_err(cx, expr.span, rel, rhs_bounds, normalized_rhs, normalized_lhs, true);
1940 declare_clippy_lint! {
1941 /// **What it does:** Checks for public `impl` or `fn` missing generalization
1942 /// over different hashers and implicitly defaulting to the default hashing
1943 /// algorithm (SipHash).
1945 /// **Why is this bad?** `HashMap` or `HashSet` with custom hashers cannot be
1948 /// **Known problems:** Suggestions for replacing constructors can contain
1949 /// false-positives. Also applying suggestions can require modification of other
1950 /// pieces of code, possibly including external crates.
1954 /// # use std::collections::HashMap;
1955 /// # use std::hash::{Hash, BuildHasher};
1956 /// # trait Serialize {};
1957 /// impl<K: Hash + Eq, V> Serialize for HashMap<K, V> { }
1959 /// pub fn foo(map: &mut HashMap<i32, i32>) { }
1961 /// could be rewritten as
1963 /// # use std::collections::HashMap;
1964 /// # use std::hash::{Hash, BuildHasher};
1965 /// # trait Serialize {};
1966 /// impl<K: Hash + Eq, V, S: BuildHasher> Serialize for HashMap<K, V, S> { }
1968 /// pub fn foo<S: BuildHasher>(map: &mut HashMap<i32, i32, S>) { }
1970 pub IMPLICIT_HASHER,
1972 "missing generalization over different hashers"
1975 declare_lint_pass!(ImplicitHasher => [IMPLICIT_HASHER]);
1977 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitHasher {
1978 #[allow(clippy::cast_possible_truncation, clippy::too_many_lines)]
1979 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
1980 use syntax_pos::BytePos;
1982 fn suggestion<'a, 'tcx>(
1983 cx: &LateContext<'a, 'tcx>,
1984 db: &mut DiagnosticBuilder<'_>,
1985 generics_span: Span,
1986 generics_suggestion_span: Span,
1987 target: &ImplicitHasherType<'_>,
1988 vis: ImplicitHasherConstructorVisitor<'_, '_, '_>,
1990 let generics_snip = snippet(cx, generics_span, "");
1992 let generics_snip = if generics_snip.is_empty() {
1995 &generics_snip[1..generics_snip.len() - 1]
2000 "consider adding a type parameter".to_string(),
2003 generics_suggestion_span,
2005 "<{}{}S: ::std::hash::BuildHasher{}>",
2007 if generics_snip.is_empty() { "" } else { ", " },
2008 if vis.suggestions.is_empty() {
2011 // request users to add `Default` bound so that generic constructors can be used
2018 format!("{}<{}, S>", target.type_name(), target.type_arguments(),),
2023 if !vis.suggestions.is_empty() {
2024 multispan_sugg(db, "...and use generic constructor".into(), vis.suggestions);
2028 if !cx.access_levels.is_exported(item.hir_id) {
2033 ItemKind::Impl(_, _, _, ref generics, _, ref ty, ref items) => {
2034 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2037 for target in &vis.found {
2038 if differing_macro_contexts(item.span, target.span()) {
2042 let generics_suggestion_span = generics.span.substitute_dummy({
2043 let pos = snippet_opt(cx, item.span.until(target.span()))
2044 .and_then(|snip| Some(item.span.lo() + BytePos(snip.find("impl")? as u32 + 4)));
2045 if let Some(pos) = pos {
2046 Span::new(pos, pos, item.span.data().ctxt)
2052 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2053 for item in items.iter().map(|item| cx.tcx.hir().impl_item(item.id)) {
2054 ctr_vis.visit_impl_item(item);
2062 "impl for `{}` should be generalized over different hashers",
2066 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2071 ItemKind::Fn(ref decl, .., ref generics, body_id) => {
2072 let body = cx.tcx.hir().body(body_id);
2074 for ty in &decl.inputs {
2075 let mut vis = ImplicitHasherTypeVisitor::new(cx);
2078 for target in &vis.found {
2079 if in_external_macro(cx.sess(), generics.span) {
2082 let generics_suggestion_span = generics.span.substitute_dummy({
2083 let pos = snippet_opt(cx, item.span.until(body.params[0].pat.span))
2085 let i = snip.find("fn")?;
2086 Some(item.span.lo() + BytePos((i + (&snip[i..]).find('(')?) as u32))
2088 .expect("failed to create span for type parameters");
2089 Span::new(pos, pos, item.span.data().ctxt)
2092 let mut ctr_vis = ImplicitHasherConstructorVisitor::new(cx, target);
2093 ctr_vis.visit_body(body);
2100 "parameter of type `{}` should be generalized over different hashers",
2104 suggestion(cx, db, generics.span, generics_suggestion_span, target, ctr_vis);
2115 enum ImplicitHasherType<'tcx> {
2116 HashMap(Span, Ty<'tcx>, Cow<'static, str>, Cow<'static, str>),
2117 HashSet(Span, Ty<'tcx>, Cow<'static, str>),
2120 impl<'tcx> ImplicitHasherType<'tcx> {
2121 /// Checks that `ty` is a target type without a BuildHasher.
2122 fn new<'a>(cx: &LateContext<'a, 'tcx>, hir_ty: &hir::Ty) -> Option<Self> {
2123 if let TyKind::Path(QPath::Resolved(None, ref path)) = hir_ty.node {
2124 let params: Vec<_> = path
2132 .filter_map(|arg| match arg {
2133 GenericArg::Type(ty) => Some(ty),
2137 let params_len = params.len();
2139 let ty = hir_ty_to_ty(cx.tcx, hir_ty);
2141 if match_path(path, &paths::HASHMAP) && params_len == 2 {
2142 Some(ImplicitHasherType::HashMap(
2145 snippet(cx, params[0].span, "K"),
2146 snippet(cx, params[1].span, "V"),
2148 } else if match_path(path, &paths::HASHSET) && params_len == 1 {
2149 Some(ImplicitHasherType::HashSet(
2152 snippet(cx, params[0].span, "T"),
2162 fn type_name(&self) -> &'static str {
2164 ImplicitHasherType::HashMap(..) => "HashMap",
2165 ImplicitHasherType::HashSet(..) => "HashSet",
2169 fn type_arguments(&self) -> String {
2171 ImplicitHasherType::HashMap(.., ref k, ref v) => format!("{}, {}", k, v),
2172 ImplicitHasherType::HashSet(.., ref t) => format!("{}", t),
2176 fn ty(&self) -> Ty<'tcx> {
2178 ImplicitHasherType::HashMap(_, ty, ..) | ImplicitHasherType::HashSet(_, ty, ..) => ty,
2182 fn span(&self) -> Span {
2184 ImplicitHasherType::HashMap(span, ..) | ImplicitHasherType::HashSet(span, ..) => span,
2189 struct ImplicitHasherTypeVisitor<'a, 'tcx> {
2190 cx: &'a LateContext<'a, 'tcx>,
2191 found: Vec<ImplicitHasherType<'tcx>>,
2194 impl<'a, 'tcx> ImplicitHasherTypeVisitor<'a, 'tcx> {
2195 fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
2196 Self { cx, found: vec![] }
2200 impl<'a, 'tcx> Visitor<'tcx> for ImplicitHasherTypeVisitor<'a, 'tcx> {
2201 fn visit_ty(&mut self, t: &'tcx hir::Ty) {
2202 if let Some(target) = ImplicitHasherType::new(self.cx, t) {
2203 self.found.push(target);
2209 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2210 NestedVisitorMap::None
2214 /// Looks for default-hasher-dependent constructors like `HashMap::new`.
2215 struct ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2216 cx: &'a LateContext<'a, 'tcx>,
2217 body: &'a TypeckTables<'tcx>,
2218 target: &'b ImplicitHasherType<'tcx>,
2219 suggestions: BTreeMap<Span, String>,
2222 impl<'a, 'b, 'tcx> ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2223 fn new(cx: &'a LateContext<'a, 'tcx>, target: &'b ImplicitHasherType<'tcx>) -> Self {
2228 suggestions: BTreeMap::new(),
2233 impl<'a, 'b, 'tcx> Visitor<'tcx> for ImplicitHasherConstructorVisitor<'a, 'b, 'tcx> {
2234 fn visit_body(&mut self, body: &'tcx Body) {
2235 let prev_body = self.body;
2236 self.body = self.cx.tcx.body_tables(body.id());
2237 walk_body(self, body);
2238 self.body = prev_body;
2241 fn visit_expr(&mut self, e: &'tcx Expr) {
2243 if let ExprKind::Call(ref fun, ref args) = e.node;
2244 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref method)) = fun.node;
2245 if let TyKind::Path(QPath::Resolved(None, ref ty_path)) = ty.node;
2247 if !same_tys(self.cx, self.target.ty(), self.body.expr_ty(e)) {
2251 if match_path(ty_path, &paths::HASHMAP) {
2252 if method.ident.name == sym!(new) {
2254 .insert(e.span, "HashMap::default()".to_string());
2255 } else if method.ident.name == sym!(with_capacity) {
2256 self.suggestions.insert(
2259 "HashMap::with_capacity_and_hasher({}, Default::default())",
2260 snippet(self.cx, args[0].span, "capacity"),
2264 } else if match_path(ty_path, &paths::HASHSET) {
2265 if method.ident.name == sym!(new) {
2267 .insert(e.span, "HashSet::default()".to_string());
2268 } else if method.ident.name == sym!(with_capacity) {
2269 self.suggestions.insert(
2272 "HashSet::with_capacity_and_hasher({}, Default::default())",
2273 snippet(self.cx, args[0].span, "capacity"),
2284 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
2285 NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
2289 declare_clippy_lint! {
2290 /// **What it does:** Checks for casts of `&T` to `&mut T` anywhere in the code.
2292 /// **Why is this bad?** It’s basically guaranteed to be undefined behaviour.
2293 /// `UnsafeCell` is the only way to obtain aliasable data that is considered
2296 /// **Known problems:** None.
2302 /// *(r as *const _ as *mut _) += 1;
2307 /// Instead consider using interior mutability types.
2310 /// use std::cell::UnsafeCell;
2312 /// fn x(r: &UnsafeCell<i32>) {
2318 pub CAST_REF_TO_MUT,
2320 "a cast of reference to a mutable pointer"
2323 declare_lint_pass!(RefToMut => [CAST_REF_TO_MUT]);
2325 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RefToMut {
2326 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
2328 if let ExprKind::Unary(UnOp::UnDeref, e) = &expr.node;
2329 if let ExprKind::Cast(e, t) = &e.node;
2330 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutMutable, .. }) = t.node;
2331 if let ExprKind::Cast(e, t) = &e.node;
2332 if let TyKind::Ptr(MutTy { mutbl: Mutability::MutImmutable, .. }) = t.node;
2333 if let ty::Ref(..) = cx.tables.node_type(e.hir_id).sty;
2339 "casting &T to &mut T may cause undefined behaviour, consider instead using an UnsafeCell",