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//! Miscellaneous type-system utilities that are too small to deserve their own modules.
use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use crate::query::Providers;
use crate::ty::layout::IntegerExt;
use crate::ty::{
self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
TypeVisitableExt,
};
use crate::ty::{GenericArgKind, GenericArgsRef};
use rustc_apfloat::Float as _;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_data_structures::stable_hasher::{Hash128, HashStable, StableHasher};
use rustc_errors::ErrorGuaranteed;
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind, Res};
use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
use rustc_index::bit_set::GrowableBitSet;
use rustc_macros::HashStable;
use rustc_session::Limit;
use rustc_span::sym;
use rustc_target::abi::{Integer, IntegerType, Size};
use rustc_target::spec::abi::Abi;
use smallvec::SmallVec;
use std::{fmt, iter};
#[derive(Copy, Clone, Debug)]
pub struct Discr<'tcx> {
/// Bit representation of the discriminant (e.g., `-128i8` is `0xFF_u128`).
pub val: u128,
pub ty: Ty<'tcx>,
}
/// Used as an input to [`TyCtxt::uses_unique_generic_params`].
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum CheckRegions {
No,
/// Only permit early bound regions. This is useful for Adts which
/// can never have late bound regions.
OnlyEarlyBound,
/// Permit both late bound and early bound regions. Use this for functions,
/// which frequently have late bound regions.
Bound,
}
#[derive(Copy, Clone, Debug)]
pub enum NotUniqueParam<'tcx> {
DuplicateParam(ty::GenericArg<'tcx>),
NotParam(ty::GenericArg<'tcx>),
}
impl<'tcx> fmt::Display for Discr<'tcx> {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self.ty.kind() {
ty::Int(ity) => {
let size = ty::tls::with(|tcx| Integer::from_int_ty(&tcx, ity).size());
let x = self.val;
// sign extend the raw representation to be an i128
let x = size.sign_extend(x) as i128;
write!(fmt, "{x}")
}
_ => write!(fmt, "{}", self.val),
}
}
}
impl<'tcx> Discr<'tcx> {
/// Adds `1` to the value and wraps around if the maximum for the type is reached.
pub fn wrap_incr(self, tcx: TyCtxt<'tcx>) -> Self {
self.checked_add(tcx, 1).0
}
pub fn checked_add(self, tcx: TyCtxt<'tcx>, n: u128) -> (Self, bool) {
let (size, signed) = self.ty.int_size_and_signed(tcx);
let (val, oflo) = if signed {
let min = size.signed_int_min();
let max = size.signed_int_max();
let val = size.sign_extend(self.val) as i128;
assert!(n < (i128::MAX as u128));
let n = n as i128;
let oflo = val > max - n;
let val = if oflo { min + (n - (max - val) - 1) } else { val + n };
// zero the upper bits
let val = val as u128;
let val = size.truncate(val);
(val, oflo)
} else {
let max = size.unsigned_int_max();
let val = self.val;
let oflo = val > max - n;
let val = if oflo { n - (max - val) - 1 } else { val + n };
(val, oflo)
};
(Self { val, ty: self.ty }, oflo)
}
}
pub trait IntTypeExt {
fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>>;
fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx>;
}
impl IntTypeExt for IntegerType {
fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
match self {
IntegerType::Pointer(true) => tcx.types.isize,
IntegerType::Pointer(false) => tcx.types.usize,
IntegerType::Fixed(i, s) => i.to_ty(tcx, *s),
}
}
fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx> {
Discr { val: 0, ty: self.to_ty(tcx) }
}
fn disr_incr<'tcx>(&self, tcx: TyCtxt<'tcx>, val: Option<Discr<'tcx>>) -> Option<Discr<'tcx>> {
if let Some(val) = val {
assert_eq!(self.to_ty(tcx), val.ty);
let (new, oflo) = val.checked_add(tcx, 1);
if oflo { None } else { Some(new) }
} else {
Some(self.initial_discriminant(tcx))
}
}
}
impl<'tcx> TyCtxt<'tcx> {
/// Creates a hash of the type `Ty` which will be the same no matter what crate
/// context it's calculated within. This is used by the `type_id` intrinsic.
pub fn type_id_hash(self, ty: Ty<'tcx>) -> Hash128 {
// We want the type_id be independent of the types free regions, so we
// erase them. The erase_regions() call will also anonymize bound
// regions, which is desirable too.
let ty = self.erase_regions(ty);
self.with_stable_hashing_context(|mut hcx| {
let mut hasher = StableHasher::new();
hcx.while_hashing_spans(false, |hcx| ty.hash_stable(hcx, &mut hasher));
hasher.finish()
})
}
pub fn res_generics_def_id(self, res: Res) -> Option<DefId> {
match res {
Res::Def(DefKind::Ctor(CtorOf::Variant, _), def_id) => {
Some(self.parent(self.parent(def_id)))
}
Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Struct, _), def_id) => {
Some(self.parent(def_id))
}
// Other `DefKind`s don't have generics and would ICE when calling
// `generics_of`.
Res::Def(
DefKind::Struct
| DefKind::Union
| DefKind::Enum
| DefKind::Trait
| DefKind::OpaqueTy
| DefKind::TyAlias
| DefKind::ForeignTy
| DefKind::TraitAlias
| DefKind::AssocTy
| DefKind::Fn
| DefKind::AssocFn
| DefKind::AssocConst
| DefKind::Impl { .. },
def_id,
) => Some(def_id),
Res::Err => None,
_ => None,
}
}
/// Attempts to returns the deeply last field of nested structures, but
/// does not apply any normalization in its search. Returns the same type
/// if input `ty` is not a structure at all.
pub fn struct_tail_without_normalization(self, ty: Ty<'tcx>) -> Ty<'tcx> {
let tcx = self;
tcx.struct_tail_with_normalize(ty, |ty| ty, || {})
}
/// Returns the deeply last field of nested structures, or the same type if
/// not a structure at all. Corresponds to the only possible unsized field,
/// and its type can be used to determine unsizing strategy.
///
/// Should only be called if `ty` has no inference variables and does not
/// need its lifetimes preserved (e.g. as part of codegen); otherwise
/// normalization attempt may cause compiler bugs.
pub fn struct_tail_erasing_lifetimes(
self,
ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> Ty<'tcx> {
let tcx = self;
tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty), || {})
}
/// Returns the deeply last field of nested structures, or the same type if
/// not a structure at all. Corresponds to the only possible unsized field,
/// and its type can be used to determine unsizing strategy.
///
/// This is parameterized over the normalization strategy (i.e. how to
/// handle `<T as Trait>::Assoc` and `impl Trait`); pass the identity
/// function to indicate no normalization should take place.
///
/// See also `struct_tail_erasing_lifetimes`, which is suitable for use
/// during codegen.
pub fn struct_tail_with_normalize(
self,
mut ty: Ty<'tcx>,
mut normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
// This is currently used to allow us to walk a ValTree
// in lockstep with the type in order to get the ValTree branch that
// corresponds to an unsized field.
mut f: impl FnMut() -> (),
) -> Ty<'tcx> {
let recursion_limit = self.recursion_limit();
for iteration in 0.. {
if !recursion_limit.value_within_limit(iteration) {
let suggested_limit = match recursion_limit {
Limit(0) => Limit(2),
limit => limit * 2,
};
let reported =
self.sess.emit_err(crate::error::RecursionLimitReached { ty, suggested_limit });
return Ty::new_error(self, reported);
}
match *ty.kind() {
ty::Adt(def, args) => {
if !def.is_struct() {
break;
}
match def.non_enum_variant().tail_opt() {
Some(field) => {
f();
ty = field.ty(self, args);
}
None => break,
}
}
ty::Tuple(tys) if let Some((&last_ty, _)) = tys.split_last() => {
f();
ty = last_ty;
}
ty::Tuple(_) => break,
ty::Alias(..) => {
let normalized = normalize(ty);
if ty == normalized {
return ty;
} else {
ty = normalized;
}
}
_ => {
break;
}
}
}
ty
}
/// Same as applying `struct_tail` on `source` and `target`, but only
/// keeps going as long as the two types are instances of the same
/// structure definitions.
/// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
/// whereas struct_tail produces `T`, and `Trait`, respectively.
///
/// Should only be called if the types have no inference variables and do
/// not need their lifetimes preserved (e.g., as part of codegen); otherwise,
/// normalization attempt may cause compiler bugs.
pub fn struct_lockstep_tails_erasing_lifetimes(
self,
source: Ty<'tcx>,
target: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> (Ty<'tcx>, Ty<'tcx>) {
let tcx = self;
tcx.struct_lockstep_tails_with_normalize(source, target, |ty| {
tcx.normalize_erasing_regions(param_env, ty)
})
}
/// Same as applying `struct_tail` on `source` and `target`, but only
/// keeps going as long as the two types are instances of the same
/// structure definitions.
/// For `(Foo<Foo<T>>, Foo<dyn Trait>)`, the result will be `(Foo<T>, Trait)`,
/// whereas struct_tail produces `T`, and `Trait`, respectively.
///
/// See also `struct_lockstep_tails_erasing_lifetimes`, which is suitable for use
/// during codegen.
pub fn struct_lockstep_tails_with_normalize(
self,
source: Ty<'tcx>,
target: Ty<'tcx>,
normalize: impl Fn(Ty<'tcx>) -> Ty<'tcx>,
) -> (Ty<'tcx>, Ty<'tcx>) {
let (mut a, mut b) = (source, target);
loop {
match (&a.kind(), &b.kind()) {
(&ty::Adt(a_def, a_args), &ty::Adt(b_def, b_args))
if a_def == b_def && a_def.is_struct() =>
{
if let Some(f) = a_def.non_enum_variant().tail_opt() {
a = f.ty(self, a_args);
b = f.ty(self, b_args);
} else {
break;
}
}
(&ty::Tuple(a_tys), &ty::Tuple(b_tys)) if a_tys.len() == b_tys.len() => {
if let Some(&a_last) = a_tys.last() {
a = a_last;
b = *b_tys.last().unwrap();
} else {
break;
}
}
(ty::Alias(..), _) | (_, ty::Alias(..)) => {
// If either side is a projection, attempt to
// progress via normalization. (Should be safe to
// apply to both sides as normalization is
// idempotent.)
let a_norm = normalize(a);
let b_norm = normalize(b);
if a == a_norm && b == b_norm {
break;
} else {
a = a_norm;
b = b_norm;
}
}
_ => break,
}
}
(a, b)
}
/// Calculate the destructor of a given type.
pub fn calculate_dtor(
self,
adt_did: DefId,
validate: impl Fn(Self, DefId) -> Result<(), ErrorGuaranteed>,
) -> Option<ty::Destructor> {
let drop_trait = self.lang_items().drop_trait()?;
self.ensure().coherent_trait(drop_trait);
let ty = self.type_of(adt_did).instantiate_identity();
let mut dtor_candidate = None;
self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
if validate(self, impl_did).is_err() {
// Already `ErrorGuaranteed`, no need to delay a span bug here.
return;
}
let Some(item_id) = self.associated_item_def_ids(impl_did).first() else {
self.sess
.delay_span_bug(self.def_span(impl_did), "Drop impl without drop function");
return;
};
if let Some((old_item_id, _)) = dtor_candidate {
self.sess
.struct_span_err(self.def_span(item_id), "multiple drop impls found")
.span_note(self.def_span(old_item_id), "other impl here")
.delay_as_bug();
}
dtor_candidate = Some((*item_id, self.constness(impl_did)));
});
let (did, constness) = dtor_candidate?;
Some(ty::Destructor { did, constness })
}
/// Returns the set of types that are required to be alive in
/// order to run the destructor of `def` (see RFCs 769 and
/// 1238).
///
/// Note that this returns only the constraints for the
/// destructor of `def` itself. For the destructors of the
/// contents, you need `adt_dtorck_constraint`.
pub fn destructor_constraints(self, def: ty::AdtDef<'tcx>) -> Vec<ty::GenericArg<'tcx>> {
let dtor = match def.destructor(self) {
None => {
debug!("destructor_constraints({:?}) - no dtor", def.did());
return vec![];
}
Some(dtor) => dtor.did,
};
let impl_def_id = self.parent(dtor);
let impl_generics = self.generics_of(impl_def_id);
// We have a destructor - all the parameters that are not
// pure_wrt_drop (i.e, don't have a #[may_dangle] attribute)
// must be live.
// We need to return the list of parameters from the ADTs
// generics/args that correspond to impure parameters on the
// impl's generics. This is a bit ugly, but conceptually simple:
//
// Suppose our ADT looks like the following
//
// struct S<X, Y, Z>(X, Y, Z);
//
// and the impl is
//
// impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
//
// We want to return the parameters (X, Y). For that, we match
// up the item-args <X, Y, Z> with the args on the impl ADT,
// <P1, P2, P0>, and then look up which of the impl args refer to
// parameters marked as pure.
let impl_args = match *self.type_of(impl_def_id).instantiate_identity().kind() {
ty::Adt(def_, args) if def_ == def => args,
_ => bug!(),
};
let item_args = match *self.type_of(def.did()).instantiate_identity().kind() {
ty::Adt(def_, args) if def_ == def => args,
_ => bug!(),
};
let result = iter::zip(item_args, impl_args)
.filter(|&(_, k)| {
match k.unpack() {
GenericArgKind::Lifetime(region) => match region.kind() {
ty::ReEarlyBound(ref ebr) => {
!impl_generics.region_param(ebr, self).pure_wrt_drop
}
// Error: not a region param
_ => false,
},
GenericArgKind::Type(ty) => match ty.kind() {
ty::Param(ref pt) => !impl_generics.type_param(pt, self).pure_wrt_drop,
// Error: not a type param
_ => false,
},
GenericArgKind::Const(ct) => match ct.kind() {
ty::ConstKind::Param(ref pc) => {
!impl_generics.const_param(pc, self).pure_wrt_drop
}
// Error: not a const param
_ => false,
},
}
})
.map(|(item_param, _)| item_param)
.collect();
debug!("destructor_constraint({:?}) = {:?}", def.did(), result);
result
}
/// Checks whether each generic argument is simply a unique generic parameter.
pub fn uses_unique_generic_params(
self,
args: GenericArgsRef<'tcx>,
ignore_regions: CheckRegions,
) -> Result<(), NotUniqueParam<'tcx>> {
let mut seen = GrowableBitSet::default();
let mut seen_late = FxHashSet::default();
for arg in args {
match arg.unpack() {
GenericArgKind::Lifetime(lt) => match (ignore_regions, lt.kind()) {
(CheckRegions::Bound, ty::ReLateBound(di, reg)) => {
if !seen_late.insert((di, reg)) {
return Err(NotUniqueParam::DuplicateParam(lt.into()));
}
}
(CheckRegions::OnlyEarlyBound | CheckRegions::Bound, ty::ReEarlyBound(p)) => {
if !seen.insert(p.index) {
return Err(NotUniqueParam::DuplicateParam(lt.into()));
}
}
(CheckRegions::OnlyEarlyBound | CheckRegions::Bound, _) => {
return Err(NotUniqueParam::NotParam(lt.into()));
}
(CheckRegions::No, _) => {}
},
GenericArgKind::Type(t) => match t.kind() {
ty::Param(p) => {
if !seen.insert(p.index) {
return Err(NotUniqueParam::DuplicateParam(t.into()));
}
}
_ => return Err(NotUniqueParam::NotParam(t.into())),
},
GenericArgKind::Const(c) => match c.kind() {
ty::ConstKind::Param(p) => {
if !seen.insert(p.index) {
return Err(NotUniqueParam::DuplicateParam(c.into()));
}
}
_ => return Err(NotUniqueParam::NotParam(c.into())),
},
}
}
Ok(())
}
/// Checks whether each generic argument is simply a unique generic placeholder.
///
/// This is used in the new solver, which canonicalizes params to placeholders
/// for better caching.
pub fn uses_unique_placeholders_ignoring_regions(
self,
args: GenericArgsRef<'tcx>,
) -> Result<(), NotUniqueParam<'tcx>> {
let mut seen = GrowableBitSet::default();
for arg in args {
match arg.unpack() {
// Ignore regions, since we can't resolve those in a canonicalized
// query in the trait solver.
GenericArgKind::Lifetime(_) => {}
GenericArgKind::Type(t) => match t.kind() {
ty::Placeholder(p) => {
if !seen.insert(p.bound.var) {
return Err(NotUniqueParam::DuplicateParam(t.into()));
}
}
_ => return Err(NotUniqueParam::NotParam(t.into())),
},
GenericArgKind::Const(c) => match c.kind() {
ty::ConstKind::Placeholder(p) => {
if !seen.insert(p.bound) {
return Err(NotUniqueParam::DuplicateParam(c.into()));
}
}
_ => return Err(NotUniqueParam::NotParam(c.into())),
},
}
}
Ok(())
}
/// Returns `true` if `def_id` refers to a closure (e.g., `|x| x * 2`). Note
/// that closures have a `DefId`, but the closure *expression* also
/// has a `HirId` that is located within the context where the
/// closure appears (and, sadly, a corresponding `NodeId`, since
/// those are not yet phased out). The parent of the closure's
/// `DefId` will also be the context where it appears.
pub fn is_closure(self, def_id: DefId) -> bool {
matches!(self.def_kind(def_id), DefKind::Closure | DefKind::Generator)
}
/// Returns `true` if `def_id` refers to a definition that does not have its own
/// type-checking context, i.e. closure, generator or inline const.
pub fn is_typeck_child(self, def_id: DefId) -> bool {
matches!(
self.def_kind(def_id),
DefKind::Closure | DefKind::Generator | DefKind::InlineConst
)
}
/// Returns `true` if `def_id` refers to a trait (i.e., `trait Foo { ... }`).
pub fn is_trait(self, def_id: DefId) -> bool {
self.def_kind(def_id) == DefKind::Trait
}
/// Returns `true` if `def_id` refers to a trait alias (i.e., `trait Foo = ...;`),
/// and `false` otherwise.
pub fn is_trait_alias(self, def_id: DefId) -> bool {
self.def_kind(def_id) == DefKind::TraitAlias
}
/// Returns `true` if this `DefId` refers to the implicit constructor for
/// a tuple struct like `struct Foo(u32)`, and `false` otherwise.
pub fn is_constructor(self, def_id: DefId) -> bool {
matches!(self.def_kind(def_id), DefKind::Ctor(..))
}
/// Given the `DefId`, returns the `DefId` of the innermost item that
/// has its own type-checking context or "inference environment".
///
/// For example, a closure has its own `DefId`, but it is type-checked
/// with the containing item. Similarly, an inline const block has its
/// own `DefId` but it is type-checked together with the containing item.
///
/// Therefore, when we fetch the
/// `typeck` the closure, for example, we really wind up
/// fetching the `typeck` the enclosing fn item.
pub fn typeck_root_def_id(self, def_id: DefId) -> DefId {
let mut def_id = def_id;
while self.is_typeck_child(def_id) {
def_id = self.parent(def_id);
}
def_id
}
/// Given the `DefId` and args a closure, creates the type of
/// `self` argument that the closure expects. For example, for a
/// `Fn` closure, this would return a reference type `&T` where
/// `T = closure_ty`.
///
/// Returns `None` if this closure's kind has not yet been inferred.
/// This should only be possible during type checking.
///
/// Note that the return value is a late-bound region and hence
/// wrapped in a binder.
pub fn closure_env_ty(
self,
closure_def_id: DefId,
closure_args: GenericArgsRef<'tcx>,
env_region: ty::Region<'tcx>,
) -> Option<Ty<'tcx>> {
let closure_ty = Ty::new_closure(self, closure_def_id, closure_args);
let closure_kind_ty = closure_args.as_closure().kind_ty();
let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
let env_ty = match closure_kind {
ty::ClosureKind::Fn => Ty::new_imm_ref(self, env_region, closure_ty),
ty::ClosureKind::FnMut => Ty::new_mut_ref(self, env_region, closure_ty),
ty::ClosureKind::FnOnce => closure_ty,
};
Some(env_ty)
}
/// Returns `true` if the node pointed to by `def_id` is a `static` item.
#[inline]
pub fn is_static(self, def_id: DefId) -> bool {
matches!(self.def_kind(def_id), DefKind::Static(_))
}
#[inline]
pub fn static_mutability(self, def_id: DefId) -> Option<hir::Mutability> {
if let DefKind::Static(mt) = self.def_kind(def_id) { Some(mt) } else { None }
}
/// Returns `true` if this is a `static` item with the `#[thread_local]` attribute.
pub fn is_thread_local_static(self, def_id: DefId) -> bool {
self.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
}
/// Returns `true` if the node pointed to by `def_id` is a mutable `static` item.
#[inline]
pub fn is_mutable_static(self, def_id: DefId) -> bool {
self.static_mutability(def_id) == Some(hir::Mutability::Mut)
}
/// Returns `true` if the item pointed to by `def_id` is a thread local which needs a
/// thread local shim generated.
#[inline]
pub fn needs_thread_local_shim(self, def_id: DefId) -> bool {
!self.sess.target.dll_tls_export
&& self.is_thread_local_static(def_id)
&& !self.is_foreign_item(def_id)
}
/// Returns the type a reference to the thread local takes in MIR.
pub fn thread_local_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
let static_ty = self.type_of(def_id).instantiate_identity();
if self.is_mutable_static(def_id) {
Ty::new_mut_ptr(self, static_ty)
} else if self.is_foreign_item(def_id) {
Ty::new_imm_ptr(self, static_ty)
} else {
// FIXME: These things don't *really* have 'static lifetime.
Ty::new_imm_ref(self, self.lifetimes.re_static, static_ty)
}
}
/// Get the type of the pointer to the static that we use in MIR.
pub fn static_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
// Make sure that any constants in the static's type are evaluated.
let static_ty = self.normalize_erasing_regions(
ty::ParamEnv::empty(),
self.type_of(def_id).instantiate_identity(),
);
// Make sure that accesses to unsafe statics end up using raw pointers.
// For thread-locals, this needs to be kept in sync with `Rvalue::ty`.
if self.is_mutable_static(def_id) {
Ty::new_mut_ptr(self, static_ty)
} else if self.is_foreign_item(def_id) {
Ty::new_imm_ptr(self, static_ty)
} else {
Ty::new_imm_ref(self, self.lifetimes.re_erased, static_ty)
}
}
/// Return the set of types that should be taken into account when checking
/// trait bounds on a generator's internal state.
pub fn generator_hidden_types(
self,
def_id: DefId,
) -> impl Iterator<Item = ty::EarlyBinder<Ty<'tcx>>> {
let generator_layout = self.mir_generator_witnesses(def_id);
generator_layout
.as_ref()
.map_or_else(|| [].iter(), |l| l.field_tys.iter())
.filter(|decl| !decl.ignore_for_traits)
.map(|decl| ty::EarlyBinder::bind(decl.ty))
}
/// Normalizes all opaque types in the given value, replacing them
/// with their underlying types.
pub fn expand_opaque_types(self, val: Ty<'tcx>) -> Ty<'tcx> {
let mut visitor = OpaqueTypeExpander {
seen_opaque_tys: FxHashSet::default(),
expanded_cache: FxHashMap::default(),
primary_def_id: None,
found_recursion: false,
found_any_recursion: false,
check_recursion: false,
expand_generators: false,
tcx: self,
};
val.fold_with(&mut visitor)
}
/// Expands the given impl trait type, stopping if the type is recursive.
#[instrument(skip(self), level = "debug", ret)]
pub fn try_expand_impl_trait_type(
self,
def_id: DefId,
args: GenericArgsRef<'tcx>,
) -> Result<Ty<'tcx>, Ty<'tcx>> {
let mut visitor = OpaqueTypeExpander {
seen_opaque_tys: FxHashSet::default(),
expanded_cache: FxHashMap::default(),
primary_def_id: Some(def_id),
found_recursion: false,
found_any_recursion: false,
check_recursion: true,
expand_generators: true,
tcx: self,
};
let expanded_type = visitor.expand_opaque_ty(def_id, args).unwrap();
if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
}
/// Query and get an English description for the item's kind.
pub fn def_descr(self, def_id: DefId) -> &'static str {
self.def_kind_descr(self.def_kind(def_id), def_id)
}
/// Get an English description for the item's kind.
pub fn def_kind_descr(self, def_kind: DefKind, def_id: DefId) -> &'static str {
match def_kind {
DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "method",
DefKind::Generator => match self.generator_kind(def_id).unwrap() {
rustc_hir::GeneratorKind::Async(..) => "async closure",
rustc_hir::GeneratorKind::Gen => "generator",
},
_ => def_kind.descr(def_id),
}
}
/// Gets an English article for the [`TyCtxt::def_descr`].
pub fn def_descr_article(self, def_id: DefId) -> &'static str {
self.def_kind_descr_article(self.def_kind(def_id), def_id)
}
/// Gets an English article for the [`TyCtxt::def_kind_descr`].
pub fn def_kind_descr_article(self, def_kind: DefKind, def_id: DefId) -> &'static str {
match def_kind {
DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "a",
DefKind::Generator => match self.generator_kind(def_id).unwrap() {
rustc_hir::GeneratorKind::Async(..) => "an",
rustc_hir::GeneratorKind::Gen => "a",
},
_ => def_kind.article(),
}
}
/// Return `true` if the supplied `CrateNum` is "user-visible," meaning either a [public]
/// dependency, or a [direct] private dependency. This is used to decide whether the crate can
/// be shown in `impl` suggestions.
///
/// [public]: TyCtxt::is_private_dep
/// [direct]: rustc_session::cstore::ExternCrate::is_direct
pub fn is_user_visible_dep(self, key: CrateNum) -> bool {
// | Private | Direct | Visible | |
// |---------|--------|---------|--------------------|
// | Yes | Yes | Yes | !true || true |
// | No | Yes | Yes | !false || true |
// | Yes | No | No | !true || false |
// | No | No | Yes | !false || false |
!self.is_private_dep(key)
// If `extern_crate` is `None`, then the crate was injected (e.g., by the allocator).
// Treat that kind of crate as "indirect", since it's an implementation detail of
// the language.
|| self.extern_crate(key.as_def_id()).map_or(false, |e| e.is_direct())
}
}
struct OpaqueTypeExpander<'tcx> {
// Contains the DefIds of the opaque types that are currently being
// expanded. When we expand an opaque type we insert the DefId of
// that type, and when we finish expanding that type we remove the
// its DefId.
seen_opaque_tys: FxHashSet<DefId>,
// Cache of all expansions we've seen so far. This is a critical
// optimization for some large types produced by async fn trees.
expanded_cache: FxHashMap<(DefId, GenericArgsRef<'tcx>), Ty<'tcx>>,
primary_def_id: Option<DefId>,
found_recursion: bool,
found_any_recursion: bool,
expand_generators: bool,
/// Whether or not to check for recursive opaque types.
/// This is `true` when we're explicitly checking for opaque type
/// recursion, and 'false' otherwise to avoid unnecessary work.
check_recursion: bool,
tcx: TyCtxt<'tcx>,
}
impl<'tcx> OpaqueTypeExpander<'tcx> {
fn expand_opaque_ty(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> Option<Ty<'tcx>> {
if self.found_any_recursion {
return None;
}
let args = args.fold_with(self);
if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
let expanded_ty = match self.expanded_cache.get(&(def_id, args)) {
Some(expanded_ty) => *expanded_ty,
None => {
let generic_ty = self.tcx.type_of(def_id);
let concrete_ty = generic_ty.instantiate(self.tcx, args);
let expanded_ty = self.fold_ty(concrete_ty);
self.expanded_cache.insert((def_id, args), expanded_ty);
expanded_ty
}
};
if self.check_recursion {
self.seen_opaque_tys.remove(&def_id);
}
Some(expanded_ty)
} else {
// If another opaque type that we contain is recursive, then it
// will report the error, so we don't have to.
self.found_any_recursion = true;
self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
None
}
}
fn expand_generator(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> Option<Ty<'tcx>> {
if self.found_any_recursion {
return None;
}
let args = args.fold_with(self);
if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
let expanded_ty = match self.expanded_cache.get(&(def_id, args)) {
Some(expanded_ty) => *expanded_ty,
None => {
for bty in self.tcx.generator_hidden_types(def_id) {
let hidden_ty = bty.instantiate(self.tcx, args);
self.fold_ty(hidden_ty);
}
let expanded_ty = Ty::new_generator_witness(self.tcx, def_id, args);
self.expanded_cache.insert((def_id, args), expanded_ty);
expanded_ty
}
};
if self.check_recursion {
self.seen_opaque_tys.remove(&def_id);
}
Some(expanded_ty)
} else {
// If another opaque type that we contain is recursive, then it
// will report the error, so we don't have to.
self.found_any_recursion = true;
self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
None
}
}
}
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
let mut t = if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) = *t.kind() {
self.expand_opaque_ty(def_id, args).unwrap_or(t)
} else if t.has_opaque_types() || t.has_generators() {
t.super_fold_with(self)
} else {
t
};
if self.expand_generators {
if let ty::GeneratorWitness(def_id, args) = *t.kind() {
t = self.expand_generator(def_id, args).unwrap_or(t);
}
}
t
}
fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
if let ty::PredicateKind::Clause(clause) = p.kind().skip_binder()
&& let ty::ClauseKind::Projection(projection_pred) = clause
{
p.kind()
.rebind(ty::ProjectionPredicate {
projection_ty: projection_pred.projection_ty.fold_with(self),
// Don't fold the term on the RHS of the projection predicate.
// This is because for default trait methods with RPITITs, we
// install a `NormalizesTo(Projection(RPITIT) -> Opaque(RPITIT))`
// predicate, which would trivially cause a cycle when we do
// anything that requires `ParamEnv::with_reveal_all_normalized`.
term: projection_pred.term,
})
.to_predicate(self.tcx)
} else {
p.super_fold_with(self)
}
}
}
impl<'tcx> Ty<'tcx> {
pub fn int_size_and_signed(self, tcx: TyCtxt<'tcx>) -> (Size, bool) {
let (int, signed) = match *self.kind() {
ty::Int(ity) => (Integer::from_int_ty(&tcx, ity), true),
ty::Uint(uty) => (Integer::from_uint_ty(&tcx, uty), false),
_ => bug!("non integer discriminant"),
};
(int.size(), signed)
}
/// Returns the maximum value for the given numeric type (including `char`s)
/// or returns `None` if the type is not numeric.
pub fn numeric_max_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
let val = match self.kind() {
ty::Int(_) | ty::Uint(_) => {
let (size, signed) = self.int_size_and_signed(tcx);
let val =
if signed { size.signed_int_max() as u128 } else { size.unsigned_int_max() };
Some(val)
}
ty::Char => Some(std::char::MAX as u128),
ty::Float(fty) => Some(match fty {
ty::FloatTy::F32 => rustc_apfloat::ieee::Single::INFINITY.to_bits(),
ty::FloatTy::F64 => rustc_apfloat::ieee::Double::INFINITY.to_bits(),
}),
_ => None,
};
val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self)))
}
/// Returns the minimum value for the given numeric type (including `char`s)
/// or returns `None` if the type is not numeric.
pub fn numeric_min_val(self, tcx: TyCtxt<'tcx>) -> Option<ty::Const<'tcx>> {
let val = match self.kind() {
ty::Int(_) | ty::Uint(_) => {
let (size, signed) = self.int_size_and_signed(tcx);
let val = if signed { size.truncate(size.signed_int_min() as u128) } else { 0 };
Some(val)
}
ty::Char => Some(0),
ty::Float(fty) => Some(match fty {
ty::FloatTy::F32 => (-::rustc_apfloat::ieee::Single::INFINITY).to_bits(),
ty::FloatTy::F64 => (-::rustc_apfloat::ieee::Double::INFINITY).to_bits(),
}),
_ => None,
};
val.map(|v| ty::Const::from_bits(tcx, v, ty::ParamEnv::empty().and(self)))
}
/// Checks whether values of this type `T` are *moved* or *copied*
/// when referenced -- this amounts to a check for whether `T:
/// Copy`, but note that we **don't** consider lifetimes when
/// doing this check. This means that we may generate MIR which
/// does copies even when the type actually doesn't satisfy the
/// full requirements for the `Copy` trait (cc #29149) -- this
/// winds up being reported as an error during NLL borrow check.
pub fn is_copy_modulo_regions(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
self.is_trivially_pure_clone_copy() || tcx.is_copy_raw(param_env.and(self))
}
/// Checks whether values of this type `T` have a size known at
/// compile time (i.e., whether `T: Sized`). Lifetimes are ignored
/// for the purposes of this check, so it can be an
/// over-approximation in generic contexts, where one can have
/// strange rules like `<T as Foo<'static>>::Bar: Sized` that
/// actually carry lifetime requirements.
pub fn is_sized(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
self.is_trivially_sized(tcx) || tcx.is_sized_raw(param_env.and(self))
}
/// Checks whether values of this type `T` implement the `Freeze`
/// trait -- frozen types are those that do not contain an
/// `UnsafeCell` anywhere. This is a language concept used to
/// distinguish "true immutability", which is relevant to
/// optimization as well as the rules around static values. Note
/// that the `Freeze` trait is not exposed to end users and is
/// effectively an implementation detail.
pub fn is_freeze(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
self.is_trivially_freeze() || tcx.is_freeze_raw(param_env.and(self))
}
/// Fast path helper for testing if a type is `Freeze`.
///
/// Returning true means the type is known to be `Freeze`. Returning
/// `false` means nothing -- could be `Freeze`, might not be.
fn is_trivially_freeze(self) -> bool {
match self.kind() {
ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Bool
| ty::Char
| ty::Str
| ty::Never
| ty::Ref(..)
| ty::RawPtr(_)
| ty::FnDef(..)
| ty::Error(_)
| ty::FnPtr(_) => true,
ty::Tuple(fields) => fields.iter().all(Self::is_trivially_freeze),
ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_freeze(),
ty::Adt(..)
| ty::Bound(..)
| ty::Closure(..)
| ty::Dynamic(..)
| ty::Foreign(_)
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::Infer(_)
| ty::Alias(..)
| ty::Param(_)
| ty::Placeholder(_) => false,
}
}
/// Checks whether values of this type `T` implement the `Unpin` trait.
pub fn is_unpin(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
self.is_trivially_unpin() || tcx.is_unpin_raw(param_env.and(self))
}
/// Fast path helper for testing if a type is `Unpin`.
///
/// Returning true means the type is known to be `Unpin`. Returning
/// `false` means nothing -- could be `Unpin`, might not be.
fn is_trivially_unpin(self) -> bool {
match self.kind() {
ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Bool
| ty::Char
| ty::Str
| ty::Never
| ty::Ref(..)
| ty::RawPtr(_)
| ty::FnDef(..)
| ty::Error(_)
| ty::FnPtr(_) => true,
ty::Tuple(fields) => fields.iter().all(Self::is_trivially_unpin),
ty::Slice(elem_ty) | ty::Array(elem_ty, _) => elem_ty.is_trivially_unpin(),
ty::Adt(..)
| ty::Bound(..)
| ty::Closure(..)
| ty::Dynamic(..)
| ty::Foreign(_)
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::Infer(_)
| ty::Alias(..)
| ty::Param(_)
| ty::Placeholder(_) => false,
}
}
/// If `ty.needs_drop(...)` returns `true`, then `ty` is definitely
/// non-copy and *might* have a destructor attached; if it returns
/// `false`, then `ty` definitely has no destructor (i.e., no drop glue).
///
/// (Note that this implies that if `ty` has a destructor attached,
/// then `needs_drop` will definitely return `true` for `ty`.)
///
/// Note that this method is used to check eligible types in unions.
#[inline]
pub fn needs_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
// Avoid querying in simple cases.
match needs_drop_components(tcx, self) {
Err(AlwaysRequiresDrop) => true,
Ok(components) => {
let query_ty = match *components {
[] => return false,
// If we've got a single component, call the query with that
// to increase the chance that we hit the query cache.
[component_ty] => component_ty,
_ => self,
};
// This doesn't depend on regions, so try to minimize distinct
// query keys used.
// If normalization fails, we just use `query_ty`.
let query_ty =
tcx.try_normalize_erasing_regions(param_env, query_ty).unwrap_or(query_ty);
tcx.needs_drop_raw(param_env.and(query_ty))
}
}
}
/// Checks if `ty` has a significant drop.
///
/// Note that this method can return false even if `ty` has a destructor
/// attached; even if that is the case then the adt has been marked with
/// the attribute `rustc_insignificant_dtor`.
///
/// Note that this method is used to check for change in drop order for
/// 2229 drop reorder migration analysis.
#[inline]
pub fn has_significant_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
// Avoid querying in simple cases.
match needs_drop_components(tcx, self) {
Err(AlwaysRequiresDrop) => true,
Ok(components) => {
let query_ty = match *components {
[] => return false,
// If we've got a single component, call the query with that
// to increase the chance that we hit the query cache.
[component_ty] => component_ty,
_ => self,
};
// FIXME(#86868): We should be canonicalizing, or else moving this to a method of inference
// context, or *something* like that, but for now just avoid passing inference
// variables to queries that can't cope with them. Instead, conservatively
// return "true" (may change drop order).
if query_ty.has_infer() {
return true;
}
// This doesn't depend on regions, so try to minimize distinct
// query keys used.
let erased = tcx.normalize_erasing_regions(param_env, query_ty);
tcx.has_significant_drop_raw(param_env.and(erased))
}
}
}
/// Returns `true` if equality for this type is both reflexive and structural.
///
/// Reflexive equality for a type is indicated by an `Eq` impl for that type.
///
/// Primitive types (`u32`, `str`) have structural equality by definition. For composite data
/// types, equality for the type as a whole is structural when it is the same as equality
/// between all components (fields, array elements, etc.) of that type. For ADTs, structural
/// equality is indicated by an implementation of `PartialStructuralEq` and `StructuralEq` for
/// that type.
///
/// This function is "shallow" because it may return `true` for a composite type whose fields
/// are not `StructuralEq`. For example, `[T; 4]` has structural equality regardless of `T`
/// because equality for arrays is determined by the equality of each array element. If you
/// want to know whether a given call to `PartialEq::eq` will proceed structurally all the way
/// down, you will need to use a type visitor.
#[inline]
pub fn is_structural_eq_shallow(self, tcx: TyCtxt<'tcx>) -> bool {
match self.kind() {
// Look for an impl of both `PartialStructuralEq` and `StructuralEq`.
ty::Adt(..) => tcx.has_structural_eq_impls(self),
// Primitive types that satisfy `Eq`.
ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Str | ty::Never => true,
// Composite types that satisfy `Eq` when all of their fields do.
//
// Because this function is "shallow", we return `true` for these composites regardless
// of the type(s) contained within.
ty::Ref(..) | ty::Array(..) | ty::Slice(_) | ty::Tuple(..) => true,
// Raw pointers use bitwise comparison.
ty::RawPtr(_) | ty::FnPtr(_) => true,
// Floating point numbers are not `Eq`.
ty::Float(_) => false,
// Conservatively return `false` for all others...
// Anonymous function types
ty::FnDef(..) | ty::Closure(..) | ty::Dynamic(..) | ty::Generator(..) => false,
// Generic or inferred types
//
// FIXME(ecstaticmorse): Maybe we should `bug` here? This should probably only be
// called for known, fully-monomorphized types.
ty::Alias(..) | ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) => {
false
}
ty::Foreign(_) | ty::GeneratorWitness(..) | ty::Error(_) => false,
}
}
/// Peel off all reference types in this type until there are none left.
///
/// This method is idempotent, i.e. `ty.peel_refs().peel_refs() == ty.peel_refs()`.
///
/// # Examples
///
/// - `u8` -> `u8`
/// - `&'a mut u8` -> `u8`
/// - `&'a &'b u8` -> `u8`
/// - `&'a *const &'b u8 -> *const &'b u8`
pub fn peel_refs(self) -> Ty<'tcx> {
let mut ty = self;
while let ty::Ref(_, inner_ty, _) = ty.kind() {
ty = *inner_ty;
}
ty
}
#[inline]
pub fn outer_exclusive_binder(self) -> ty::DebruijnIndex {
self.0.outer_exclusive_binder
}
}
pub enum ExplicitSelf<'tcx> {
ByValue,
ByReference(ty::Region<'tcx>, hir::Mutability),
ByRawPointer(hir::Mutability),
ByBox,
Other,
}
impl<'tcx> ExplicitSelf<'tcx> {
/// Categorizes an explicit self declaration like `self: SomeType`
/// into either `self`, `&self`, `&mut self`, `Box<Self>`, or
/// `Other`.
/// This is mainly used to require the arbitrary_self_types feature
/// in the case of `Other`, to improve error messages in the common cases,
/// and to make `Other` non-object-safe.
///
/// Examples:
///
/// ```ignore (illustrative)
/// impl<'a> Foo for &'a T {
/// // Legal declarations:
/// fn method1(self: &&'a T); // ExplicitSelf::ByReference
/// fn method2(self: &'a T); // ExplicitSelf::ByValue
/// fn method3(self: Box<&'a T>); // ExplicitSelf::ByBox
/// fn method4(self: Rc<&'a T>); // ExplicitSelf::Other
///
/// // Invalid cases will be caught by `check_method_receiver`:
/// fn method_err1(self: &'a mut T); // ExplicitSelf::Other
/// fn method_err2(self: &'static T) // ExplicitSelf::ByValue
/// fn method_err3(self: &&T) // ExplicitSelf::ByReference
/// }
/// ```
///
pub fn determine<P>(self_arg_ty: Ty<'tcx>, is_self_ty: P) -> ExplicitSelf<'tcx>
where
P: Fn(Ty<'tcx>) -> bool,
{
use self::ExplicitSelf::*;
match *self_arg_ty.kind() {
_ if is_self_ty(self_arg_ty) => ByValue,
ty::Ref(region, ty, mutbl) if is_self_ty(ty) => ByReference(region, mutbl),
ty::RawPtr(ty::TypeAndMut { ty, mutbl }) if is_self_ty(ty) => ByRawPointer(mutbl),
ty::Adt(def, _) if def.is_box() && is_self_ty(self_arg_ty.boxed_ty()) => ByBox,
_ => Other,
}
}
}
/// Returns a list of types such that the given type needs drop if and only if
/// *any* of the returned types need drop. Returns `Err(AlwaysRequiresDrop)` if
/// this type always needs drop.
pub fn needs_drop_components<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
) -> Result<SmallVec<[Ty<'tcx>; 2]>, AlwaysRequiresDrop> {
match *ty.kind() {
ty::Infer(ty::FreshIntTy(_))
| ty::Infer(ty::FreshFloatTy(_))
| ty::Bool
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Never
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Char
| ty::GeneratorWitness(..)
| ty::RawPtr(_)
| ty::Ref(..)
| ty::Str => Ok(SmallVec::new()),
// Foreign types can never have destructors.
ty::Foreign(..) => Ok(SmallVec::new()),
ty::Dynamic(..) | ty::Error(_) => Err(AlwaysRequiresDrop),
ty::Slice(ty) => needs_drop_components(tcx, ty),
ty::Array(elem_ty, size) => {
match needs_drop_components(tcx, elem_ty) {
Ok(v) if v.is_empty() => Ok(v),
res => match size.try_to_target_usize(tcx) {
// Arrays of size zero don't need drop, even if their element
// type does.
Some(0) => Ok(SmallVec::new()),
Some(_) => res,
// We don't know which of the cases above we are in, so
// return the whole type and let the caller decide what to
// do.
None => Ok(smallvec![ty]),
},
}
}
// If any field needs drop, then the whole tuple does.
ty::Tuple(fields) => fields.iter().try_fold(SmallVec::new(), move |mut acc, elem| {
acc.extend(needs_drop_components(tcx, elem)?);
Ok(acc)
}),
// These require checking for `Copy` bounds or `Adt` destructors.
ty::Adt(..)
| ty::Alias(..)
| ty::Param(_)
| ty::Bound(..)
| ty::Placeholder(..)
| ty::Infer(_)
| ty::Closure(..)
| ty::Generator(..) => Ok(smallvec![ty]),
}
}
pub fn is_trivially_const_drop(ty: Ty<'_>) -> bool {
match *ty.kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Infer(ty::IntVar(_))
| ty::Infer(ty::FloatVar(_))
| ty::Str
| ty::RawPtr(_)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Never
| ty::Foreign(_) => true,
ty::Alias(..)
| ty::Dynamic(..)
| ty::Error(_)
| ty::Bound(..)
| ty::Param(_)
| ty::Placeholder(_)
| ty::Infer(_) => false,
// Not trivial because they have components, and instead of looking inside,
// we'll just perform trait selection.
ty::Closure(..) | ty::Generator(..) | ty::GeneratorWitness(..) | ty::Adt(..) => false,
ty::Array(ty, _) | ty::Slice(ty) => is_trivially_const_drop(ty),
ty::Tuple(tys) => tys.iter().all(|ty| is_trivially_const_drop(ty)),
}
}
/// Does the equivalent of
/// ```ignore (illustrative)
/// let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
/// folder.tcx().intern_*(&v)
/// ```
pub fn fold_list<'tcx, F, T>(
list: &'tcx ty::List<T>,
folder: &mut F,
intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
) -> Result<&'tcx ty::List<T>, F::Error>
where
F: FallibleTypeFolder<TyCtxt<'tcx>>,
T: TypeFoldable<TyCtxt<'tcx>> + PartialEq + Copy,
{
let mut iter = list.iter();
// Look for the first element that changed
match iter.by_ref().enumerate().find_map(|(i, t)| match t.try_fold_with(folder) {
Ok(new_t) if new_t == t => None,
new_t => Some((i, new_t)),
}) {
Some((i, Ok(new_t))) => {
// An element changed, prepare to intern the resulting list
let mut new_list = SmallVec::<[_; 8]>::with_capacity(list.len());
new_list.extend_from_slice(&list[..i]);
new_list.push(new_t);
for t in iter {
new_list.push(t.try_fold_with(folder)?)
}
Ok(intern(folder.interner(), &new_list))
}
Some((_, Err(err))) => {
return Err(err);
}
None => Ok(list),
}
}
#[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
pub struct AlwaysRequiresDrop;
/// Reveals all opaque types in the given value, replacing them
/// with their underlying types.
pub fn reveal_opaque_types_in_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
val: &'tcx ty::List<ty::Clause<'tcx>>,
) -> &'tcx ty::List<ty::Clause<'tcx>> {
let mut visitor = OpaqueTypeExpander {
seen_opaque_tys: FxHashSet::default(),
expanded_cache: FxHashMap::default(),
primary_def_id: None,
found_recursion: false,
found_any_recursion: false,
check_recursion: false,
expand_generators: false,
tcx,
};
val.fold_with(&mut visitor)
}
/// Determines whether an item is annotated with `doc(hidden)`.
fn is_doc_hidden(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
tcx.get_attrs(def_id, sym::doc)
.filter_map(|attr| attr.meta_item_list())
.any(|items| items.iter().any(|item| item.has_name(sym::hidden)))
}
/// Determines whether an item is annotated with `doc(notable_trait)`.
pub fn is_doc_notable_trait(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
tcx.get_attrs(def_id, sym::doc)
.filter_map(|attr| attr.meta_item_list())
.any(|items| items.iter().any(|item| item.has_name(sym::notable_trait)))
}
/// Determines whether an item is an intrinsic by Abi.
pub fn is_intrinsic(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
matches!(tcx.fn_sig(def_id).skip_binder().abi(), Abi::RustIntrinsic | Abi::PlatformIntrinsic)
}
pub fn provide(providers: &mut Providers) {
*providers = Providers {
reveal_opaque_types_in_bounds,
is_doc_hidden,
is_doc_notable_trait,
is_intrinsic,
..*providers
}
}