1022 lines
37 KiB
Rust
1022 lines
37 KiB
Rust
//! Trait Resolution. See the [rustc dev guide] for more information on how this works.
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//!
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//! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/resolution.html
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pub mod query;
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pub mod select;
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pub mod solve;
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pub mod specialization_graph;
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mod structural_impls;
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pub mod util;
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use crate::infer::canonical::Canonical;
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use crate::mir::ConstraintCategory;
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use crate::ty::abstract_const::NotConstEvaluatable;
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use crate::ty::GenericArgsRef;
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use crate::ty::{self, AdtKind, Ty};
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use rustc_data_structures::sync::Lrc;
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use rustc_errors::{Applicability, Diagnostic};
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use rustc_hir as hir;
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use rustc_hir::def_id::DefId;
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use rustc_span::def_id::{LocalDefId, CRATE_DEF_ID};
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use rustc_span::symbol::Symbol;
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use rustc_span::{Span, DUMMY_SP};
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use smallvec::SmallVec;
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use std::borrow::Cow;
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use std::hash::{Hash, Hasher};
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pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache};
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pub use self::ObligationCauseCode::*;
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/// Depending on the stage of compilation, we want projection to be
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/// more or less conservative.
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#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable, Encodable, Decodable)]
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pub enum Reveal {
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/// At type-checking time, we refuse to project any associated
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/// type that is marked `default`. Non-`default` ("final") types
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/// are always projected. This is necessary in general for
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/// soundness of specialization. However, we *could* allow
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/// projections in fully-monomorphic cases. We choose not to,
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/// because we prefer for `default type` to force the type
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/// definition to be treated abstractly by any consumers of the
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/// impl. Concretely, that means that the following example will
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/// fail to compile:
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///
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/// ```compile_fail,E0308
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/// #![feature(specialization)]
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/// trait Assoc {
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/// type Output;
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/// }
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///
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/// impl<T> Assoc for T {
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/// default type Output = bool;
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/// }
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///
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/// fn main() {
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/// let x: <() as Assoc>::Output = true;
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/// }
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/// ```
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///
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/// We also do not reveal the hidden type of opaque types during
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/// type-checking.
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UserFacing,
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/// At codegen time, all monomorphic projections will succeed.
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/// Also, `impl Trait` is normalized to the concrete type,
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/// which has to be already collected by type-checking.
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///
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/// NOTE: as `impl Trait`'s concrete type should *never*
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/// be observable directly by the user, `Reveal::All`
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/// should not be used by checks which may expose
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/// type equality or type contents to the user.
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/// There are some exceptions, e.g., around auto traits and
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/// transmute-checking, which expose some details, but
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/// not the whole concrete type of the `impl Trait`.
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All,
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}
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/// The reason why we incurred this obligation; used for error reporting.
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///
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/// Non-misc `ObligationCauseCode`s are stored on the heap. This gives the
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/// best trade-off between keeping the type small (which makes copies cheaper)
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/// while not doing too many heap allocations.
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///
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/// We do not want to intern this as there are a lot of obligation causes which
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/// only live for a short period of time.
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#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
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#[derive(TypeVisitable, TypeFoldable)]
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pub struct ObligationCause<'tcx> {
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pub span: Span,
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/// The ID of the fn body that triggered this obligation. This is
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/// used for region obligations to determine the precise
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/// environment in which the region obligation should be evaluated
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/// (in particular, closures can add new assumptions). See the
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/// field `region_obligations` of the `FulfillmentContext` for more
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/// information.
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pub body_id: LocalDefId,
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code: InternedObligationCauseCode<'tcx>,
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}
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// This custom hash function speeds up hashing for `Obligation` deduplication
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// greatly by skipping the `code` field, which can be large and complex. That
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// shouldn't affect hash quality much since there are several other fields in
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// `Obligation` which should be unique enough, especially the predicate itself
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// which is hashed as an interned pointer. See #90996.
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impl Hash for ObligationCause<'_> {
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fn hash<H: Hasher>(&self, state: &mut H) {
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self.body_id.hash(state);
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self.span.hash(state);
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}
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}
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impl<'tcx> ObligationCause<'tcx> {
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#[inline]
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pub fn new(
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span: Span,
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body_id: LocalDefId,
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code: ObligationCauseCode<'tcx>,
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) -> ObligationCause<'tcx> {
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ObligationCause { span, body_id, code: code.into() }
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}
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pub fn misc(span: Span, body_id: LocalDefId) -> ObligationCause<'tcx> {
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ObligationCause::new(span, body_id, MiscObligation)
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}
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#[inline(always)]
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pub fn dummy() -> ObligationCause<'tcx> {
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ObligationCause::dummy_with_span(DUMMY_SP)
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}
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#[inline(always)]
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pub fn dummy_with_span(span: Span) -> ObligationCause<'tcx> {
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ObligationCause { span, body_id: CRATE_DEF_ID, code: Default::default() }
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}
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pub fn span(&self) -> Span {
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match *self.code() {
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ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
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arm_span,
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..
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}) => arm_span,
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_ => self.span,
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}
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}
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#[inline]
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pub fn code(&self) -> &ObligationCauseCode<'tcx> {
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&self.code
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}
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pub fn map_code(
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&mut self,
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f: impl FnOnce(InternedObligationCauseCode<'tcx>) -> ObligationCauseCode<'tcx>,
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) {
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self.code = f(std::mem::take(&mut self.code)).into();
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}
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pub fn derived_cause(
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mut self,
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parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
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variant: impl FnOnce(DerivedObligationCause<'tcx>) -> ObligationCauseCode<'tcx>,
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) -> ObligationCause<'tcx> {
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/*!
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* Creates a cause for obligations that are derived from
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* `obligation` by a recursive search (e.g., for a builtin
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* bound, or eventually a `auto trait Foo`). If `obligation`
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* is itself a derived obligation, this is just a clone, but
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* otherwise we create a "derived obligation" cause so as to
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* keep track of the original root obligation for error
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* reporting.
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*/
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// NOTE(flaper87): As of now, it keeps track of the whole error
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// chain. Ideally, we should have a way to configure this either
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// by using -Z verbose-internals or just a CLI argument.
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self.code =
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variant(DerivedObligationCause { parent_trait_pred, parent_code: self.code }).into();
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self
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}
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pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> {
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match self.code() {
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MatchImpl(cause, _) => cause.to_constraint_category(),
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AscribeUserTypeProvePredicate(predicate_span) => {
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ConstraintCategory::Predicate(*predicate_span)
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}
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_ => ConstraintCategory::BoringNoLocation,
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}
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}
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}
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#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
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#[derive(TypeVisitable, TypeFoldable)]
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pub struct UnifyReceiverContext<'tcx> {
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pub assoc_item: ty::AssocItem,
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pub param_env: ty::ParamEnv<'tcx>,
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pub args: GenericArgsRef<'tcx>,
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}
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#[derive(Clone, PartialEq, Eq, Default, HashStable)]
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#[derive(TypeVisitable, TypeFoldable, TyEncodable, TyDecodable)]
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pub struct InternedObligationCauseCode<'tcx> {
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/// `None` for `ObligationCauseCode::MiscObligation` (a common case, occurs ~60% of
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/// the time). `Some` otherwise.
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code: Option<Lrc<ObligationCauseCode<'tcx>>>,
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}
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impl<'tcx> std::fmt::Debug for InternedObligationCauseCode<'tcx> {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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let cause: &ObligationCauseCode<'_> = self;
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cause.fmt(f)
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}
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}
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impl<'tcx> ObligationCauseCode<'tcx> {
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#[inline(always)]
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fn into(self) -> InternedObligationCauseCode<'tcx> {
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InternedObligationCauseCode {
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code: if let ObligationCauseCode::MiscObligation = self {
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None
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} else {
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Some(Lrc::new(self))
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},
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}
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}
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}
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impl<'tcx> std::ops::Deref for InternedObligationCauseCode<'tcx> {
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type Target = ObligationCauseCode<'tcx>;
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fn deref(&self) -> &Self::Target {
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self.code.as_deref().unwrap_or(&ObligationCauseCode::MiscObligation)
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}
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}
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#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
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#[derive(TypeVisitable, TypeFoldable)]
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pub enum ObligationCauseCode<'tcx> {
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/// Not well classified or should be obvious from the span.
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MiscObligation,
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/// A slice or array is WF only if `T: Sized`.
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SliceOrArrayElem,
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/// A tuple is WF only if its middle elements are `Sized`.
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TupleElem,
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/// Must satisfy all of the where-clause predicates of the
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/// given item.
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ItemObligation(DefId),
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/// Like `ItemObligation`, but carries the span of the
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/// predicate when it can be identified.
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BindingObligation(DefId, Span),
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/// Like `ItemObligation`, but carries the `HirId` of the
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/// expression that caused the obligation, and the `usize`
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/// indicates exactly which predicate it is in the list of
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/// instantiated predicates.
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ExprItemObligation(DefId, rustc_hir::HirId, usize),
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/// Combines `ExprItemObligation` and `BindingObligation`.
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ExprBindingObligation(DefId, Span, rustc_hir::HirId, usize),
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/// A type like `&'a T` is WF only if `T: 'a`.
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ReferenceOutlivesReferent(Ty<'tcx>),
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/// A type like `Box<Foo<'a> + 'b>` is WF only if `'b: 'a`.
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ObjectTypeBound(Ty<'tcx>, ty::Region<'tcx>),
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/// Obligation incurred due to a coercion.
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Coercion {
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source: Ty<'tcx>,
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target: Ty<'tcx>,
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},
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/// Various cases where expressions must be `Sized` / `Copy` / etc.
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/// `L = X` implies that `L` is `Sized`.
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AssignmentLhsSized,
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/// `(x1, .., xn)` must be `Sized`.
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TupleInitializerSized,
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/// `S { ... }` must be `Sized`.
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StructInitializerSized,
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/// Type of each variable must be `Sized`.
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VariableType(hir::HirId),
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/// Argument type must be `Sized`.
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SizedArgumentType(Option<hir::HirId>),
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/// Return type must be `Sized`.
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SizedReturnType,
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/// Yield type must be `Sized`.
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SizedYieldType,
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/// Inline asm operand type must be `Sized`.
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InlineAsmSized,
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/// Captured closure type must be `Sized`.
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SizedClosureCapture(LocalDefId),
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/// Types live across coroutine yields must be `Sized`.
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SizedCoroutineInterior(LocalDefId),
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/// `[expr; N]` requires `type_of(expr): Copy`.
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RepeatElementCopy {
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/// If element is a `const fn` or const ctor we display a help message suggesting
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/// to move it to a new `const` item while saying that `T` doesn't implement `Copy`.
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is_constable: IsConstable,
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elt_type: Ty<'tcx>,
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elt_span: Span,
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/// Span of the statement/item in which the repeat expression occurs. We can use this to
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/// place a `const` declaration before it
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elt_stmt_span: Span,
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},
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/// Types of fields (other than the last, except for packed structs) in a struct must be sized.
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FieldSized {
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adt_kind: AdtKind,
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span: Span,
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last: bool,
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},
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/// Constant expressions must be sized.
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ConstSized,
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/// `static` items must have `Sync` type.
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SharedStatic,
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BuiltinDerivedObligation(DerivedObligationCause<'tcx>),
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ImplDerivedObligation(Box<ImplDerivedObligationCause<'tcx>>),
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DerivedObligation(DerivedObligationCause<'tcx>),
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FunctionArgumentObligation {
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/// The node of the relevant argument in the function call.
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arg_hir_id: hir::HirId,
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/// The node of the function call.
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call_hir_id: hir::HirId,
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/// The obligation introduced by this argument.
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parent_code: InternedObligationCauseCode<'tcx>,
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},
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/// Error derived when checking an impl item is compatible with
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/// its corresponding trait item's definition
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CompareImplItemObligation {
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impl_item_def_id: LocalDefId,
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trait_item_def_id: DefId,
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kind: ty::AssocKind,
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},
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/// Checking that the bounds of a trait's associated type hold for a given impl
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CheckAssociatedTypeBounds {
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impl_item_def_id: LocalDefId,
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trait_item_def_id: DefId,
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},
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/// Checking that this expression can be assigned to its target.
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ExprAssignable,
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/// Computing common supertype in the arms of a match expression
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MatchExpressionArm(Box<MatchExpressionArmCause<'tcx>>),
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/// Type error arising from type checking a pattern against an expected type.
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Pattern {
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/// The span of the scrutinee or type expression which caused the `root_ty` type.
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span: Option<Span>,
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/// The root expected type induced by a scrutinee or type expression.
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root_ty: Ty<'tcx>,
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/// Whether the `Span` came from an expression or a type expression.
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origin_expr: bool,
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},
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/// Computing common supertype in an if expression
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IfExpression(Box<IfExpressionCause<'tcx>>),
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/// Computing common supertype of an if expression with no else counter-part
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IfExpressionWithNoElse,
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/// `main` has wrong type
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MainFunctionType,
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/// `start` has wrong type
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StartFunctionType,
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/// language function has wrong type
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LangFunctionType(Symbol),
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/// Intrinsic has wrong type
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IntrinsicType,
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/// A let else block does not diverge
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LetElse,
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/// Method receiver
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MethodReceiver,
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UnifyReceiver(Box<UnifyReceiverContext<'tcx>>),
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/// `return` with no expression
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ReturnNoExpression,
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/// `return` with an expression
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ReturnValue(hir::HirId),
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/// Opaque return type of this function
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OpaqueReturnType(Option<(Ty<'tcx>, Span)>),
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/// Block implicit return
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BlockTailExpression(hir::HirId, hir::MatchSource),
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/// #[feature(trivial_bounds)] is not enabled
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TrivialBound,
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AwaitableExpr(hir::HirId),
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ForLoopIterator,
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QuestionMark,
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/// Well-formed checking. If a `WellFormedLoc` is provided,
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/// then it will be used to perform HIR-based wf checking
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/// after an error occurs, in order to generate a more precise error span.
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/// This is purely for diagnostic purposes - it is always
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/// correct to use `MiscObligation` instead, or to specify
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/// `WellFormed(None)`
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WellFormed(Option<WellFormedLoc>),
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/// From `match_impl`. The cause for us having to match an impl, and the DefId we are matching against.
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MatchImpl(ObligationCause<'tcx>, DefId),
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BinOp {
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lhs_hir_id: hir::HirId,
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rhs_hir_id: Option<hir::HirId>,
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rhs_span: Option<Span>,
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rhs_is_lit: bool,
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output_ty: Option<Ty<'tcx>>,
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},
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AscribeUserTypeProvePredicate(Span),
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RustCall,
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/// Obligations to prove that a `std::ops::Drop` impl is not stronger than
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/// the ADT it's being implemented for.
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DropImpl,
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/// Requirement for a `const N: Ty` to implement `Ty: ConstParamTy`
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ConstParam(Ty<'tcx>),
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/// Obligations emitted during the normalization of a weak type alias.
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TypeAlias(InternedObligationCauseCode<'tcx>, Span, DefId),
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}
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/// Whether a value can be extracted into a const.
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/// Used for diagnostics around array repeat expressions.
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#[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
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pub enum IsConstable {
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No,
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/// Call to a const fn
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Fn,
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/// Use of a const ctor
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Ctor,
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}
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crate::TrivialTypeTraversalAndLiftImpls! {
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IsConstable,
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}
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/// The 'location' at which we try to perform HIR-based wf checking.
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/// This information is used to obtain an `hir::Ty`, which
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/// we can walk in order to obtain precise spans for any
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/// 'nested' types (e.g. `Foo` in `Option<Foo>`).
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#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, Encodable, Decodable)]
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#[derive(TypeVisitable, TypeFoldable)]
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pub enum WellFormedLoc {
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/// Use the type of the provided definition.
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Ty(LocalDefId),
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/// Use the type of the parameter of the provided function.
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/// We cannot use `hir::Param`, since the function may
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/// not have a body (e.g. a trait method definition)
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Param {
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/// The function to lookup the parameter in
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function: LocalDefId,
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/// The index of the parameter to use.
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/// Parameters are indexed from 0, with the return type
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/// being the last 'parameter'
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param_idx: u16,
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},
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}
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#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
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#[derive(TypeVisitable, TypeFoldable)]
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pub struct ImplDerivedObligationCause<'tcx> {
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pub derived: DerivedObligationCause<'tcx>,
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/// The `DefId` of the `impl` that gave rise to the `derived` obligation.
|
|
/// If the `derived` obligation arose from a trait alias, which conceptually has a synthetic impl,
|
|
/// then this will be the `DefId` of that trait alias. Care should therefore be taken to handle
|
|
/// that exceptional case where appropriate.
|
|
pub impl_or_alias_def_id: DefId,
|
|
/// The index of the derived predicate in the parent impl's predicates.
|
|
pub impl_def_predicate_index: Option<usize>,
|
|
pub span: Span,
|
|
}
|
|
|
|
impl<'tcx> ObligationCauseCode<'tcx> {
|
|
/// Returns the base obligation, ignoring derived obligations.
|
|
pub fn peel_derives(&self) -> &Self {
|
|
let mut base_cause = self;
|
|
while let Some((parent_code, _)) = base_cause.parent() {
|
|
base_cause = parent_code;
|
|
}
|
|
base_cause
|
|
}
|
|
|
|
/// Returns the base obligation and the base trait predicate, if any, ignoring
|
|
/// derived obligations.
|
|
pub fn peel_derives_with_predicate(&self) -> (&Self, Option<ty::PolyTraitPredicate<'tcx>>) {
|
|
let mut base_cause = self;
|
|
let mut base_trait_pred = None;
|
|
while let Some((parent_code, parent_pred)) = base_cause.parent() {
|
|
base_cause = parent_code;
|
|
if let Some(parent_pred) = parent_pred {
|
|
base_trait_pred = Some(parent_pred);
|
|
}
|
|
}
|
|
|
|
(base_cause, base_trait_pred)
|
|
}
|
|
|
|
pub fn parent(&self) -> Option<(&Self, Option<ty::PolyTraitPredicate<'tcx>>)> {
|
|
match self {
|
|
FunctionArgumentObligation { parent_code, .. } => Some((parent_code, None)),
|
|
BuiltinDerivedObligation(derived)
|
|
| DerivedObligation(derived)
|
|
| ImplDerivedObligation(box ImplDerivedObligationCause { derived, .. }) => {
|
|
Some((&derived.parent_code, Some(derived.parent_trait_pred)))
|
|
}
|
|
_ => None,
|
|
}
|
|
}
|
|
|
|
pub fn peel_match_impls(&self) -> &Self {
|
|
match self {
|
|
MatchImpl(cause, _) => cause.code(),
|
|
_ => self,
|
|
}
|
|
}
|
|
}
|
|
|
|
// `ObligationCauseCode` is used a lot. Make sure it doesn't unintentionally get bigger.
|
|
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
|
|
static_assert_size!(ObligationCauseCode<'_>, 48);
|
|
|
|
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
|
|
pub enum StatementAsExpression {
|
|
CorrectType,
|
|
NeedsBoxing,
|
|
}
|
|
|
|
#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
|
|
#[derive(TypeVisitable, TypeFoldable)]
|
|
pub struct MatchExpressionArmCause<'tcx> {
|
|
pub arm_block_id: Option<hir::HirId>,
|
|
pub arm_ty: Ty<'tcx>,
|
|
pub arm_span: Span,
|
|
pub prior_arm_block_id: Option<hir::HirId>,
|
|
pub prior_arm_ty: Ty<'tcx>,
|
|
pub prior_arm_span: Span,
|
|
pub scrut_span: Span,
|
|
pub scrut_hir_id: hir::HirId,
|
|
pub source: hir::MatchSource,
|
|
pub prior_arms: Vec<Span>,
|
|
pub opt_suggest_box_span: Option<Span>,
|
|
}
|
|
|
|
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
|
|
#[derive(TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
|
|
pub struct IfExpressionCause<'tcx> {
|
|
pub then_id: hir::HirId,
|
|
pub else_id: hir::HirId,
|
|
pub then_ty: Ty<'tcx>,
|
|
pub else_ty: Ty<'tcx>,
|
|
pub outer_span: Option<Span>,
|
|
pub opt_suggest_box_span: Option<Span>,
|
|
}
|
|
|
|
#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
|
|
#[derive(TypeVisitable, TypeFoldable)]
|
|
pub struct DerivedObligationCause<'tcx> {
|
|
/// The trait predicate of the parent obligation that led to the
|
|
/// current obligation. Note that only trait obligations lead to
|
|
/// derived obligations, so we just store the trait predicate here
|
|
/// directly.
|
|
pub parent_trait_pred: ty::PolyTraitPredicate<'tcx>,
|
|
|
|
/// The parent trait had this cause.
|
|
pub parent_code: InternedObligationCauseCode<'tcx>,
|
|
}
|
|
|
|
#[derive(Clone, Debug, TypeVisitable)]
|
|
pub enum SelectionError<'tcx> {
|
|
/// The trait is not implemented.
|
|
Unimplemented,
|
|
/// After a closure impl has selected, its "outputs" were evaluated
|
|
/// (which for closures includes the "input" type params) and they
|
|
/// didn't resolve. See `confirm_poly_trait_refs` for more.
|
|
SignatureMismatch(Box<SignatureMismatchData<'tcx>>),
|
|
/// The trait pointed by `DefId` is not object safe.
|
|
TraitNotObjectSafe(DefId),
|
|
/// A given constant couldn't be evaluated.
|
|
NotConstEvaluatable(NotConstEvaluatable),
|
|
/// Exceeded the recursion depth during type projection.
|
|
Overflow(OverflowError),
|
|
/// Signaling that an error has already been emitted, to avoid
|
|
/// multiple errors being shown.
|
|
ErrorReporting,
|
|
/// Computing an opaque type's hidden type caused an error (e.g. a cycle error).
|
|
/// We can thus not know whether the hidden type implements an auto trait, so
|
|
/// we should not presume anything about it.
|
|
OpaqueTypeAutoTraitLeakageUnknown(DefId),
|
|
}
|
|
|
|
#[derive(Clone, Debug, TypeVisitable)]
|
|
pub struct SignatureMismatchData<'tcx> {
|
|
pub found_trait_ref: ty::PolyTraitRef<'tcx>,
|
|
pub expected_trait_ref: ty::PolyTraitRef<'tcx>,
|
|
pub terr: ty::error::TypeError<'tcx>,
|
|
}
|
|
|
|
/// When performing resolution, it is typically the case that there
|
|
/// can be one of three outcomes:
|
|
///
|
|
/// - `Ok(Some(r))`: success occurred with result `r`
|
|
/// - `Ok(None)`: could not definitely determine anything, usually due
|
|
/// to inconclusive type inference.
|
|
/// - `Err(e)`: error `e` occurred
|
|
pub type SelectionResult<'tcx, T> = Result<Option<T>, SelectionError<'tcx>>;
|
|
|
|
/// Given the successful resolution of an obligation, the `ImplSource`
|
|
/// indicates where the impl comes from.
|
|
///
|
|
/// For example, the obligation may be satisfied by a specific impl (case A),
|
|
/// or it may be relative to some bound that is in scope (case B).
|
|
///
|
|
/// ```ignore (illustrative)
|
|
/// impl<T:Clone> Clone<T> for Option<T> { ... } // Impl_1
|
|
/// impl<T:Clone> Clone<T> for Box<T> { ... } // Impl_2
|
|
/// impl Clone for i32 { ... } // Impl_3
|
|
///
|
|
/// fn foo<T: Clone>(concrete: Option<Box<i32>>, param: T, mixed: Option<T>) {
|
|
/// // Case A: ImplSource points at a specific impl. Only possible when
|
|
/// // type is concretely known. If the impl itself has bounded
|
|
/// // type parameters, ImplSource will carry resolutions for those as well:
|
|
/// concrete.clone(); // ImplSource(Impl_1, [ImplSource(Impl_2, [ImplSource(Impl_3)])])
|
|
///
|
|
/// // Case B: ImplSource must be provided by caller. This applies when
|
|
/// // type is a type parameter.
|
|
/// param.clone(); // ImplSource::Param
|
|
///
|
|
/// // Case C: A mix of cases A and B.
|
|
/// mixed.clone(); // ImplSource(Impl_1, [ImplSource::Param])
|
|
/// }
|
|
/// ```
|
|
///
|
|
/// ### The type parameter `N`
|
|
///
|
|
/// See explanation on `ImplSourceUserDefinedData`.
|
|
#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
|
|
#[derive(TypeFoldable, TypeVisitable)]
|
|
pub enum ImplSource<'tcx, N> {
|
|
/// ImplSource identifying a particular impl.
|
|
UserDefined(ImplSourceUserDefinedData<'tcx, N>),
|
|
|
|
/// Successful resolution to an obligation provided by the caller
|
|
/// for some type parameter. The `Vec<N>` represents the
|
|
/// obligations incurred from normalizing the where-clause (if
|
|
/// any).
|
|
Param(Vec<N>),
|
|
|
|
/// Successful resolution for a builtin impl.
|
|
Builtin(BuiltinImplSource, Vec<N>),
|
|
}
|
|
|
|
impl<'tcx, N> ImplSource<'tcx, N> {
|
|
pub fn nested_obligations(self) -> Vec<N> {
|
|
match self {
|
|
ImplSource::UserDefined(i) => i.nested,
|
|
ImplSource::Param(n) | ImplSource::Builtin(_, n) => n,
|
|
}
|
|
}
|
|
|
|
pub fn borrow_nested_obligations(&self) -> &[N] {
|
|
match self {
|
|
ImplSource::UserDefined(i) => &i.nested,
|
|
ImplSource::Param(n) | ImplSource::Builtin(_, n) => n,
|
|
}
|
|
}
|
|
|
|
pub fn borrow_nested_obligations_mut(&mut self) -> &mut [N] {
|
|
match self {
|
|
ImplSource::UserDefined(i) => &mut i.nested,
|
|
ImplSource::Param(n) | ImplSource::Builtin(_, n) => n,
|
|
}
|
|
}
|
|
|
|
pub fn map<M, F>(self, f: F) -> ImplSource<'tcx, M>
|
|
where
|
|
F: FnMut(N) -> M,
|
|
{
|
|
match self {
|
|
ImplSource::UserDefined(i) => ImplSource::UserDefined(ImplSourceUserDefinedData {
|
|
impl_def_id: i.impl_def_id,
|
|
args: i.args,
|
|
nested: i.nested.into_iter().map(f).collect(),
|
|
}),
|
|
ImplSource::Param(n) => ImplSource::Param(n.into_iter().map(f).collect()),
|
|
ImplSource::Builtin(source, n) => {
|
|
ImplSource::Builtin(source, n.into_iter().map(f).collect())
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Identifies a particular impl in the source, along with a set of
|
|
/// substitutions from the impl's type/lifetime parameters. The
|
|
/// `nested` vector corresponds to the nested obligations attached to
|
|
/// the impl's type parameters.
|
|
///
|
|
/// The type parameter `N` indicates the type used for "nested
|
|
/// obligations" that are required by the impl. During type-check, this
|
|
/// is `Obligation`, as one might expect. During codegen, however, this
|
|
/// is `()`, because codegen only requires a shallow resolution of an
|
|
/// impl, and nested obligations are satisfied later.
|
|
#[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
|
|
#[derive(TypeFoldable, TypeVisitable)]
|
|
pub struct ImplSourceUserDefinedData<'tcx, N> {
|
|
pub impl_def_id: DefId,
|
|
pub args: GenericArgsRef<'tcx>,
|
|
pub nested: Vec<N>,
|
|
}
|
|
|
|
#[derive(Copy, Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, Debug)]
|
|
pub enum BuiltinImplSource {
|
|
/// Some builtin impl we don't need to differentiate. This should be used
|
|
/// unless more specific information is necessary.
|
|
Misc,
|
|
/// A builtin impl for trait objects.
|
|
///
|
|
/// The vtable is formed by concatenating together the method lists of
|
|
/// the base object trait and all supertraits, pointers to supertrait vtable will
|
|
/// be provided when necessary; this is the start of `upcast_trait_ref`'s methods
|
|
/// in that vtable.
|
|
Object { vtable_base: usize },
|
|
/// The vtable is formed by concatenating together the method lists of
|
|
/// the base object trait and all supertraits, pointers to supertrait vtable will
|
|
/// be provided when necessary; this is the position of `upcast_trait_ref`'s vtable
|
|
/// within that vtable.
|
|
TraitUpcasting { vtable_vptr_slot: Option<usize> },
|
|
/// Unsizing a tuple like `(A, B, ..., X)` to `(A, B, ..., Y)` if `X` unsizes to `Y`.
|
|
///
|
|
/// This needs to be a separate variant as it is still unstable and we need to emit
|
|
/// a feature error when using it on stable.
|
|
TupleUnsizing,
|
|
}
|
|
|
|
TrivialTypeTraversalImpls! { BuiltinImplSource }
|
|
|
|
#[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
|
|
pub enum ObjectSafetyViolation {
|
|
/// `Self: Sized` declared on the trait.
|
|
SizedSelf(SmallVec<[Span; 1]>),
|
|
|
|
/// Supertrait reference references `Self` an in illegal location
|
|
/// (e.g., `trait Foo : Bar<Self>`).
|
|
SupertraitSelf(SmallVec<[Span; 1]>),
|
|
|
|
// Supertrait has a non-lifetime `for<T>` binder.
|
|
SupertraitNonLifetimeBinder(SmallVec<[Span; 1]>),
|
|
|
|
/// Method has something illegal.
|
|
Method(Symbol, MethodViolationCode, Span),
|
|
|
|
/// Associated const.
|
|
AssocConst(Symbol, Span),
|
|
|
|
/// GAT
|
|
GAT(Symbol, Span),
|
|
}
|
|
|
|
impl ObjectSafetyViolation {
|
|
pub fn error_msg(&self) -> Cow<'static, str> {
|
|
match self {
|
|
ObjectSafetyViolation::SizedSelf(_) => "it requires `Self: Sized`".into(),
|
|
ObjectSafetyViolation::SupertraitSelf(ref spans) => {
|
|
if spans.iter().any(|sp| *sp != DUMMY_SP) {
|
|
"it uses `Self` as a type parameter".into()
|
|
} else {
|
|
"it cannot use `Self` as a type parameter in a supertrait or `where`-clause"
|
|
.into()
|
|
}
|
|
}
|
|
ObjectSafetyViolation::SupertraitNonLifetimeBinder(_) => {
|
|
"where clause cannot reference non-lifetime `for<...>` variables".into()
|
|
}
|
|
ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => {
|
|
format!("associated function `{name}` has no `self` parameter").into()
|
|
}
|
|
ObjectSafetyViolation::Method(
|
|
name,
|
|
MethodViolationCode::ReferencesSelfInput(_),
|
|
DUMMY_SP,
|
|
) => format!("method `{name}` references the `Self` type in its parameters").into(),
|
|
ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfInput(_), _) => {
|
|
format!("method `{name}` references the `Self` type in this parameter").into()
|
|
}
|
|
ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfOutput, _) => {
|
|
format!("method `{name}` references the `Self` type in its return type").into()
|
|
}
|
|
ObjectSafetyViolation::Method(
|
|
name,
|
|
MethodViolationCode::ReferencesImplTraitInTrait(_),
|
|
_,
|
|
) => {
|
|
format!("method `{name}` references an `impl Trait` type in its return type").into()
|
|
}
|
|
ObjectSafetyViolation::Method(name, MethodViolationCode::AsyncFn, _) => {
|
|
format!("method `{name}` is `async`").into()
|
|
}
|
|
ObjectSafetyViolation::Method(
|
|
name,
|
|
MethodViolationCode::WhereClauseReferencesSelf,
|
|
_,
|
|
) => format!("method `{name}` references the `Self` type in its `where` clause").into(),
|
|
ObjectSafetyViolation::Method(name, MethodViolationCode::Generic, _) => {
|
|
format!("method `{name}` has generic type parameters").into()
|
|
}
|
|
ObjectSafetyViolation::Method(
|
|
name,
|
|
MethodViolationCode::UndispatchableReceiver(_),
|
|
_,
|
|
) => format!("method `{name}`'s `self` parameter cannot be dispatched on").into(),
|
|
ObjectSafetyViolation::AssocConst(name, DUMMY_SP) => {
|
|
format!("it contains associated `const` `{name}`").into()
|
|
}
|
|
ObjectSafetyViolation::AssocConst(..) => "it contains this associated `const`".into(),
|
|
ObjectSafetyViolation::GAT(name, _) => {
|
|
format!("it contains the generic associated type `{name}`").into()
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn solution(&self) -> ObjectSafetyViolationSolution {
|
|
match self {
|
|
ObjectSafetyViolation::SizedSelf(_)
|
|
| ObjectSafetyViolation::SupertraitSelf(_)
|
|
| ObjectSafetyViolation::SupertraitNonLifetimeBinder(..) => {
|
|
ObjectSafetyViolationSolution::None
|
|
}
|
|
ObjectSafetyViolation::Method(
|
|
name,
|
|
MethodViolationCode::StaticMethod(Some((add_self_sugg, make_sized_sugg))),
|
|
_,
|
|
) => ObjectSafetyViolationSolution::AddSelfOrMakeSized {
|
|
name: *name,
|
|
add_self_sugg: add_self_sugg.clone(),
|
|
make_sized_sugg: make_sized_sugg.clone(),
|
|
},
|
|
ObjectSafetyViolation::Method(
|
|
name,
|
|
MethodViolationCode::UndispatchableReceiver(Some(span)),
|
|
_,
|
|
) => ObjectSafetyViolationSolution::ChangeToRefSelf(*name, *span),
|
|
ObjectSafetyViolation::AssocConst(name, _)
|
|
| ObjectSafetyViolation::GAT(name, _)
|
|
| ObjectSafetyViolation::Method(name, ..) => {
|
|
ObjectSafetyViolationSolution::MoveToAnotherTrait(*name)
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn spans(&self) -> SmallVec<[Span; 1]> {
|
|
// When `span` comes from a separate crate, it'll be `DUMMY_SP`. Treat it as `None` so
|
|
// diagnostics use a `note` instead of a `span_label`.
|
|
match self {
|
|
ObjectSafetyViolation::SupertraitSelf(spans)
|
|
| ObjectSafetyViolation::SizedSelf(spans)
|
|
| ObjectSafetyViolation::SupertraitNonLifetimeBinder(spans) => spans.clone(),
|
|
ObjectSafetyViolation::AssocConst(_, span)
|
|
| ObjectSafetyViolation::GAT(_, span)
|
|
| ObjectSafetyViolation::Method(_, _, span)
|
|
if *span != DUMMY_SP =>
|
|
{
|
|
smallvec![*span]
|
|
}
|
|
_ => smallvec![],
|
|
}
|
|
}
|
|
}
|
|
|
|
#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
|
|
pub enum ObjectSafetyViolationSolution {
|
|
None,
|
|
AddSelfOrMakeSized {
|
|
name: Symbol,
|
|
add_self_sugg: (String, Span),
|
|
make_sized_sugg: (String, Span),
|
|
},
|
|
ChangeToRefSelf(Symbol, Span),
|
|
MoveToAnotherTrait(Symbol),
|
|
}
|
|
|
|
impl ObjectSafetyViolationSolution {
|
|
pub fn add_to(self, err: &mut Diagnostic) {
|
|
match self {
|
|
ObjectSafetyViolationSolution::None => {}
|
|
ObjectSafetyViolationSolution::AddSelfOrMakeSized {
|
|
name,
|
|
add_self_sugg,
|
|
make_sized_sugg,
|
|
} => {
|
|
err.span_suggestion(
|
|
add_self_sugg.1,
|
|
format!(
|
|
"consider turning `{name}` into a method by giving it a `&self` argument"
|
|
),
|
|
add_self_sugg.0,
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
err.span_suggestion(
|
|
make_sized_sugg.1,
|
|
format!(
|
|
"alternatively, consider constraining `{name}` so it does not apply to \
|
|
trait objects"
|
|
),
|
|
make_sized_sugg.0,
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
}
|
|
ObjectSafetyViolationSolution::ChangeToRefSelf(name, span) => {
|
|
err.span_suggestion(
|
|
span,
|
|
format!("consider changing method `{name}`'s `self` parameter to be `&self`"),
|
|
"&Self",
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
ObjectSafetyViolationSolution::MoveToAnotherTrait(name) => {
|
|
err.help(format!("consider moving `{name}` to another trait"));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Reasons a method might not be object-safe.
|
|
#[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
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pub enum MethodViolationCode {
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/// e.g., `fn foo()`
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StaticMethod(Option<(/* add &self */ (String, Span), /* add Self: Sized */ (String, Span))>),
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/// e.g., `fn foo(&self, x: Self)`
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ReferencesSelfInput(Option<Span>),
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/// e.g., `fn foo(&self) -> Self`
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ReferencesSelfOutput,
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/// e.g., `fn foo(&self) -> impl Sized`
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ReferencesImplTraitInTrait(Span),
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/// e.g., `async fn foo(&self)`
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AsyncFn,
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/// e.g., `fn foo(&self) where Self: Clone`
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WhereClauseReferencesSelf,
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/// e.g., `fn foo<A>()`
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Generic,
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/// the method's receiver (`self` argument) can't be dispatched on
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UndispatchableReceiver(Option<Span>),
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}
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/// These are the error cases for `codegen_select_candidate`.
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#[derive(Copy, Clone, Debug, Hash, HashStable, Encodable, Decodable)]
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pub enum CodegenObligationError {
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/// Ambiguity can happen when monomorphizing during trans
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/// expands to some humongous type that never occurred
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/// statically -- this humongous type can then overflow,
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/// leading to an ambiguous result. So report this as an
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/// overflow bug, since I believe this is the only case
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/// where ambiguity can result.
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Ambiguity,
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/// This can trigger when we probe for the source of a `'static` lifetime requirement
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/// on a trait object: `impl Foo for dyn Trait {}` has an implicit `'static` bound.
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/// This can also trigger when we have a global bound that is not actually satisfied,
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/// but was included during typeck due to the trivial_bounds feature.
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Unimplemented,
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FulfillmentError,
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}
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/// Defines the treatment of opaque types in a given inference context.
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///
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/// This affects both what opaques are allowed to be defined, but also whether
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/// opaques are replaced with inference vars eagerly in the old solver (e.g.
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/// in projection, and in the signature during function type-checking).
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#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
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pub enum DefiningAnchor {
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/// Define opaques which are in-scope of the `LocalDefId`. Also, eagerly
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/// replace opaque types in `replace_opaque_types_with_inference_vars`.
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Bind(LocalDefId),
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/// In contexts where we don't currently know what opaques are allowed to be
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/// defined, such as (old solver) canonical queries, we will simply allow
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/// opaques to be defined, but "bubble" them up in the canonical response or
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/// otherwise treat them to be handled later.
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///
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/// We do not eagerly replace opaque types in `replace_opaque_types_with_inference_vars`,
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/// which may affect what predicates pass and fail in the old trait solver.
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Bubble,
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/// Do not allow any opaques to be defined. This is used to catch type mismatch
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/// errors when handling opaque types, and also should be used when we would
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/// otherwise reveal opaques (such as [`Reveal::All`] reveal mode).
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Error,
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}
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