1 //! Util methods for [`rustc_middle::ty`]
3 #![allow(clippy::module_name_repetitions)]
5 use std::collections::HashMap;
7 use rustc_ast::ast::Mutability;
9 use rustc_hir::def_id::DefId;
10 use rustc_hir::{TyKind, Unsafety};
11 use rustc_infer::infer::TyCtxtInferExt;
12 use rustc_lint::LateContext;
13 use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
14 use rustc_middle::ty::{self, IntTy, Ty, TypeFoldable, UintTy};
16 use rustc_span::symbol::Symbol;
17 use rustc_span::DUMMY_SP;
18 use rustc_trait_selection::traits::query::normalize::AtExt;
20 use crate::{match_def_path, must_use_attr};
22 pub fn is_copy<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
23 ty.is_copy_modulo_regions(cx.tcx.at(DUMMY_SP), cx.param_env)
26 /// Checks whether a type can be partially moved.
27 pub fn can_partially_move_ty(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
28 if has_drop(cx, ty) || is_copy(cx, ty) {
32 ty::Param(_) => false,
33 ty::Adt(def, subs) => def.all_fields().any(|f| !is_copy(cx, f.ty(cx.tcx, subs))),
38 /// Walks into `ty` and returns `true` if any inner type is the same as `other_ty`
39 pub fn contains_ty(ty: Ty<'_>, other_ty: Ty<'_>) -> bool {
40 ty.walk().any(|inner| match inner.unpack() {
41 GenericArgKind::Type(inner_ty) => ty::TyS::same_type(other_ty, inner_ty),
42 GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
46 /// Returns true if ty has `iter` or `iter_mut` methods
47 pub fn has_iter_method(cx: &LateContext<'_>, probably_ref_ty: Ty<'_>) -> Option<Symbol> {
48 // FIXME: instead of this hard-coded list, we should check if `<adt>::iter`
49 // exists and has the desired signature. Unfortunately FnCtxt is not exported
50 // so we can't use its `lookup_method` method.
51 let into_iter_collections: &[Symbol] = &[
67 let ty_to_check = match probably_ref_ty.kind() {
68 ty::Ref(_, ty_to_check, _) => ty_to_check,
72 let def_id = match ty_to_check.kind() {
73 ty::Array(..) => return Some(sym::array),
74 ty::Slice(..) => return Some(sym::slice),
75 ty::Adt(adt, _) => adt.did,
79 for &name in into_iter_collections {
80 if cx.tcx.is_diagnostic_item(name, def_id) {
81 return Some(cx.tcx.item_name(def_id));
87 /// Checks whether a type implements a trait.
88 /// See also `get_trait_def_id`.
89 pub fn implements_trait<'tcx>(
90 cx: &LateContext<'tcx>,
93 ty_params: &[GenericArg<'tcx>],
95 // Do not check on infer_types to avoid panic in evaluate_obligation.
96 if ty.has_infer_types() {
99 let ty = cx.tcx.erase_regions(ty);
100 if ty.has_escaping_bound_vars() {
103 let ty_params = cx.tcx.mk_substs(ty_params.iter());
104 cx.tcx.type_implements_trait((trait_id, ty, ty_params, cx.param_env))
107 /// Checks whether this type implements `Drop`.
108 pub fn has_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
109 match ty.ty_adt_def() {
110 Some(def) => def.has_dtor(cx.tcx),
115 // Returns whether the type has #[must_use] attribute
116 pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
118 ty::Adt(ref adt, _) => must_use_attr(&cx.tcx.get_attrs(adt.did)).is_some(),
119 ty::Foreign(ref did) => must_use_attr(&cx.tcx.get_attrs(*did)).is_some(),
121 | ty::Array(ref ty, _)
122 | ty::RawPtr(ty::TypeAndMut { ref ty, .. })
123 | ty::Ref(_, ref ty, _) => {
124 // for the Array case we don't need to care for the len == 0 case
125 // because we don't want to lint functions returning empty arrays
126 is_must_use_ty(cx, *ty)
128 ty::Tuple(ref substs) => substs.types().any(|ty| is_must_use_ty(cx, ty)),
129 ty::Opaque(ref def_id, _) => {
130 for (predicate, _) in cx.tcx.explicit_item_bounds(*def_id) {
131 if let ty::PredicateKind::Trait(trait_predicate, _) = predicate.kind().skip_binder() {
132 if must_use_attr(&cx.tcx.get_attrs(trait_predicate.trait_ref.def_id)).is_some() {
139 ty::Dynamic(binder, _) => {
140 for predicate in binder.iter() {
141 if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate.skip_binder() {
142 if must_use_attr(&cx.tcx.get_attrs(trait_ref.def_id)).is_some() {
153 // FIXME: Per https://doc.rust-lang.org/nightly/nightly-rustc/rustc_trait_selection/infer/at/struct.At.html#method.normalize
154 // this function can be removed once the `normalizie` method does not panic when normalization does
156 /// Checks if `Ty` is normalizable. This function is useful
157 /// to avoid crashes on `layout_of`.
158 pub fn is_normalizable<'tcx>(cx: &LateContext<'tcx>, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
159 is_normalizable_helper(cx, param_env, ty, &mut HashMap::new())
162 fn is_normalizable_helper<'tcx>(
163 cx: &LateContext<'tcx>,
164 param_env: ty::ParamEnv<'tcx>,
166 cache: &mut HashMap<Ty<'tcx>, bool>,
168 if let Some(&cached_result) = cache.get(ty) {
169 return cached_result;
171 // prevent recursive loops, false-negative is better than endless loop leading to stack overflow
172 cache.insert(ty, false);
173 let result = cx.tcx.infer_ctxt().enter(|infcx| {
174 let cause = rustc_middle::traits::ObligationCause::dummy();
175 if infcx.at(&cause, param_env).normalize(ty).is_ok() {
177 ty::Adt(def, substs) => def.variants.iter().all(|variant| {
181 .all(|field| is_normalizable_helper(cx, param_env, field.ty(cx.tcx, substs), cache))
183 _ => ty.walk().all(|generic_arg| match generic_arg.unpack() {
184 GenericArgKind::Type(inner_ty) if inner_ty != ty => {
185 is_normalizable_helper(cx, param_env, inner_ty, cache)
187 _ => true, // if inner_ty == ty, we've already checked it
194 cache.insert(ty, result);
198 /// Returns true iff the given type is a primitive (a bool or char, any integer or floating-point
199 /// number type, a str, or an array, slice, or tuple of those types).
200 pub fn is_recursively_primitive_type(ty: Ty<'_>) -> bool {
202 ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str => true,
203 ty::Ref(_, inner, _) if *inner.kind() == ty::Str => true,
204 ty::Array(inner_type, _) | ty::Slice(inner_type) => is_recursively_primitive_type(inner_type),
205 ty::Tuple(inner_types) => inner_types.types().all(is_recursively_primitive_type),
210 /// Checks if the type is equal to a diagnostic item
212 /// If you change the signature, remember to update the internal lint `MatchTypeOnDiagItem`
213 pub fn is_type_diagnostic_item(cx: &LateContext<'_>, ty: Ty<'_>, diag_item: Symbol) -> bool {
215 ty::Adt(adt, _) => cx.tcx.is_diagnostic_item(diag_item, adt.did),
220 /// Checks if the type is equal to a lang item
221 pub fn is_type_lang_item(cx: &LateContext<'_>, ty: Ty<'_>, lang_item: hir::LangItem) -> bool {
223 ty::Adt(adt, _) => cx.tcx.lang_items().require(lang_item).unwrap() == adt.did,
228 /// Return `true` if the passed `typ` is `isize` or `usize`.
229 pub fn is_isize_or_usize(typ: Ty<'_>) -> bool {
230 matches!(typ.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
233 /// Checks if type is struct, enum or union type with the given def path.
235 /// If the type is a diagnostic item, use `is_type_diagnostic_item` instead.
236 /// If you change the signature, remember to update the internal lint `MatchTypeOnDiagItem`
237 pub fn match_type(cx: &LateContext<'_>, ty: Ty<'_>, path: &[&str]) -> bool {
239 ty::Adt(adt, _) => match_def_path(cx, adt.did, path),
244 /// Peels off all references on the type. Returns the underlying type and the number of references
246 pub fn peel_mid_ty_refs(ty: Ty<'_>) -> (Ty<'_>, usize) {
247 fn peel(ty: Ty<'_>, count: usize) -> (Ty<'_>, usize) {
248 if let ty::Ref(_, ty, _) = ty.kind() {
257 /// Peels off all references on the type.Returns the underlying type, the number of references
258 /// removed, and whether the pointer is ultimately mutable or not.
259 pub fn peel_mid_ty_refs_is_mutable(ty: Ty<'_>) -> (Ty<'_>, usize, Mutability) {
260 fn f(ty: Ty<'_>, count: usize, mutability: Mutability) -> (Ty<'_>, usize, Mutability) {
262 ty::Ref(_, ty, Mutability::Mut) => f(ty, count + 1, mutability),
263 ty::Ref(_, ty, Mutability::Not) => f(ty, count + 1, Mutability::Not),
264 _ => (ty, count, mutability),
267 f(ty, 0, Mutability::Mut)
270 /// Returns `true` if the given type is an `unsafe` function.
271 pub fn type_is_unsafe_function<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
273 ty::FnDef(..) | ty::FnPtr(_) => ty.fn_sig(cx.tcx).unsafety() == Unsafety::Unsafe,
278 /// Returns the base type for HIR references and pointers.
279 pub fn walk_ptrs_hir_ty<'tcx>(ty: &'tcx hir::Ty<'tcx>) -> &'tcx hir::Ty<'tcx> {
281 TyKind::Ptr(ref mut_ty) | TyKind::Rptr(_, ref mut_ty) => walk_ptrs_hir_ty(&mut_ty.ty),
286 /// Returns the base type for references and raw pointers, and count reference
288 pub fn walk_ptrs_ty_depth(ty: Ty<'_>) -> (Ty<'_>, usize) {
289 fn inner(ty: Ty<'_>, depth: usize) -> (Ty<'_>, usize) {
291 ty::Ref(_, ty, _) => inner(ty, depth + 1),