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, AdtDef, 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 /// Walks into `ty` and returns `true` if any inner type is any instance of the given abstract data
48 pub fn contains_adt(ty: Ty<'_>, adt: &AdtDef) -> bool {
49 ty.walk().any(|inner| match inner.unpack() {
50 GenericArgKind::Type(inner_ty) => inner_ty.ty_adt_def() == Some(adt),
51 GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
55 /// Returns true if ty has `iter` or `iter_mut` methods
56 pub fn has_iter_method(cx: &LateContext<'_>, probably_ref_ty: Ty<'_>) -> Option<Symbol> {
57 // FIXME: instead of this hard-coded list, we should check if `<adt>::iter`
58 // exists and has the desired signature. Unfortunately FnCtxt is not exported
59 // so we can't use its `lookup_method` method.
60 let into_iter_collections: &[Symbol] = &[
76 let ty_to_check = match probably_ref_ty.kind() {
77 ty::Ref(_, ty_to_check, _) => ty_to_check,
81 let def_id = match ty_to_check.kind() {
82 ty::Array(..) => return Some(sym::array),
83 ty::Slice(..) => return Some(sym::slice),
84 ty::Adt(adt, _) => adt.did,
88 for &name in into_iter_collections {
89 if cx.tcx.is_diagnostic_item(name, def_id) {
90 return Some(cx.tcx.item_name(def_id));
96 /// Checks whether a type implements a trait.
97 /// See also `get_trait_def_id`.
98 pub fn implements_trait<'tcx>(
99 cx: &LateContext<'tcx>,
102 ty_params: &[GenericArg<'tcx>],
104 // Do not check on infer_types to avoid panic in evaluate_obligation.
105 if ty.has_infer_types() {
108 let ty = cx.tcx.erase_regions(ty);
109 if ty.has_escaping_bound_vars() {
112 let ty_params = cx.tcx.mk_substs(ty_params.iter());
113 cx.tcx.type_implements_trait((trait_id, ty, ty_params, cx.param_env))
116 /// Checks whether this type implements `Drop`.
117 pub fn has_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
118 match ty.ty_adt_def() {
119 Some(def) => def.has_dtor(cx.tcx),
124 // Returns whether the type has #[must_use] attribute
125 pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
127 ty::Adt(ref adt, _) => must_use_attr(&cx.tcx.get_attrs(adt.did)).is_some(),
128 ty::Foreign(ref did) => must_use_attr(&cx.tcx.get_attrs(*did)).is_some(),
130 | ty::Array(ref ty, _)
131 | ty::RawPtr(ty::TypeAndMut { ref ty, .. })
132 | ty::Ref(_, ref ty, _) => {
133 // for the Array case we don't need to care for the len == 0 case
134 // because we don't want to lint functions returning empty arrays
135 is_must_use_ty(cx, *ty)
137 ty::Tuple(ref substs) => substs.types().any(|ty| is_must_use_ty(cx, ty)),
138 ty::Opaque(ref def_id, _) => {
139 for (predicate, _) in cx.tcx.explicit_item_bounds(*def_id) {
140 if let ty::PredicateKind::Trait(trait_predicate, _) = predicate.kind().skip_binder() {
141 if must_use_attr(&cx.tcx.get_attrs(trait_predicate.trait_ref.def_id)).is_some() {
148 ty::Dynamic(binder, _) => {
149 for predicate in binder.iter() {
150 if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate.skip_binder() {
151 if must_use_attr(&cx.tcx.get_attrs(trait_ref.def_id)).is_some() {
162 // FIXME: Per https://doc.rust-lang.org/nightly/nightly-rustc/rustc_trait_selection/infer/at/struct.At.html#method.normalize
163 // this function can be removed once the `normalizie` method does not panic when normalization does
165 /// Checks if `Ty` is normalizable. This function is useful
166 /// to avoid crashes on `layout_of`.
167 pub fn is_normalizable<'tcx>(cx: &LateContext<'tcx>, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
168 is_normalizable_helper(cx, param_env, ty, &mut HashMap::new())
171 fn is_normalizable_helper<'tcx>(
172 cx: &LateContext<'tcx>,
173 param_env: ty::ParamEnv<'tcx>,
175 cache: &mut HashMap<Ty<'tcx>, bool>,
177 if let Some(&cached_result) = cache.get(ty) {
178 return cached_result;
180 // prevent recursive loops, false-negative is better than endless loop leading to stack overflow
181 cache.insert(ty, false);
182 let result = cx.tcx.infer_ctxt().enter(|infcx| {
183 let cause = rustc_middle::traits::ObligationCause::dummy();
184 if infcx.at(&cause, param_env).normalize(ty).is_ok() {
186 ty::Adt(def, substs) => def.variants.iter().all(|variant| {
190 .all(|field| is_normalizable_helper(cx, param_env, field.ty(cx.tcx, substs), cache))
192 _ => ty.walk().all(|generic_arg| match generic_arg.unpack() {
193 GenericArgKind::Type(inner_ty) if inner_ty != ty => {
194 is_normalizable_helper(cx, param_env, inner_ty, cache)
196 _ => true, // if inner_ty == ty, we've already checked it
203 cache.insert(ty, result);
207 /// Returns true iff the given type is a primitive (a bool or char, any integer or floating-point
208 /// number type, a str, or an array, slice, or tuple of those types).
209 pub fn is_recursively_primitive_type(ty: Ty<'_>) -> bool {
211 ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str => true,
212 ty::Ref(_, inner, _) if *inner.kind() == ty::Str => true,
213 ty::Array(inner_type, _) | ty::Slice(inner_type) => is_recursively_primitive_type(inner_type),
214 ty::Tuple(inner_types) => inner_types.types().all(is_recursively_primitive_type),
219 /// Checks if the type is equal to a diagnostic item
221 /// If you change the signature, remember to update the internal lint `MatchTypeOnDiagItem`
222 pub fn is_type_diagnostic_item(cx: &LateContext<'_>, ty: Ty<'_>, diag_item: Symbol) -> bool {
224 ty::Adt(adt, _) => cx.tcx.is_diagnostic_item(diag_item, adt.did),
229 /// Checks if the type is equal to a lang item
230 pub fn is_type_lang_item(cx: &LateContext<'_>, ty: Ty<'_>, lang_item: hir::LangItem) -> bool {
232 ty::Adt(adt, _) => cx.tcx.lang_items().require(lang_item).unwrap() == adt.did,
237 /// Return `true` if the passed `typ` is `isize` or `usize`.
238 pub fn is_isize_or_usize(typ: Ty<'_>) -> bool {
239 matches!(typ.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
242 /// Checks if type is struct, enum or union type with the given def path.
244 /// If the type is a diagnostic item, use `is_type_diagnostic_item` instead.
245 /// If you change the signature, remember to update the internal lint `MatchTypeOnDiagItem`
246 pub fn match_type(cx: &LateContext<'_>, ty: Ty<'_>, path: &[&str]) -> bool {
248 ty::Adt(adt, _) => match_def_path(cx, adt.did, path),
253 /// Peels off all references on the type. Returns the underlying type and the number of references
255 pub fn peel_mid_ty_refs(ty: Ty<'_>) -> (Ty<'_>, usize) {
256 fn peel(ty: Ty<'_>, count: usize) -> (Ty<'_>, usize) {
257 if let ty::Ref(_, ty, _) = ty.kind() {
266 /// Peels off all references on the type.Returns the underlying type, the number of references
267 /// removed, and whether the pointer is ultimately mutable or not.
268 pub fn peel_mid_ty_refs_is_mutable(ty: Ty<'_>) -> (Ty<'_>, usize, Mutability) {
269 fn f(ty: Ty<'_>, count: usize, mutability: Mutability) -> (Ty<'_>, usize, Mutability) {
271 ty::Ref(_, ty, Mutability::Mut) => f(ty, count + 1, mutability),
272 ty::Ref(_, ty, Mutability::Not) => f(ty, count + 1, Mutability::Not),
273 _ => (ty, count, mutability),
276 f(ty, 0, Mutability::Mut)
279 /// Returns `true` if the given type is an `unsafe` function.
280 pub fn type_is_unsafe_function<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
282 ty::FnDef(..) | ty::FnPtr(_) => ty.fn_sig(cx.tcx).unsafety() == Unsafety::Unsafe,
287 /// Returns the base type for HIR references and pointers.
288 pub fn walk_ptrs_hir_ty<'tcx>(ty: &'tcx hir::Ty<'tcx>) -> &'tcx hir::Ty<'tcx> {
290 TyKind::Ptr(ref mut_ty) | TyKind::Rptr(_, ref mut_ty) => walk_ptrs_hir_ty(&mut_ty.ty),
295 /// Returns the base type for references and raw pointers, and count reference
297 pub fn walk_ptrs_ty_depth(ty: Ty<'_>) -> (Ty<'_>, usize) {
298 fn inner(ty: Ty<'_>, depth: usize) -> (Ty<'_>, usize) {
300 ty::Ref(_, ty, _) => inner(ty, depth + 1),