1001 lines
37 KiB
Rust
1001 lines
37 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Trait Resolution. See [rustc guide] for more info on how this works.
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//!
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//! [rustc guide]: https://rust-lang-nursery.github.io/rustc-guide/trait-resolution.html
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pub use self::SelectionError::*;
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pub use self::FulfillmentErrorCode::*;
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pub use self::Vtable::*;
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pub use self::ObligationCauseCode::*;
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use hir;
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use hir::def_id::DefId;
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use infer::outlives::env::OutlivesEnvironment;
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use middle::region;
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use middle::const_val::ConstEvalErr;
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use ty::subst::Substs;
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use ty::{self, AdtKind, Slice, Ty, TyCtxt, GenericParamDefKind, TypeFoldable, ToPredicate};
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use ty::error::{ExpectedFound, TypeError};
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use infer::{InferCtxt};
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use rustc_data_structures::sync::Lrc;
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use std::rc::Rc;
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use syntax::ast;
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use syntax_pos::{Span, DUMMY_SP};
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pub use self::coherence::{orphan_check, overlapping_impls, OrphanCheckErr, OverlapResult};
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pub use self::fulfill::{FulfillmentContext, PendingPredicateObligation};
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pub use self::project::MismatchedProjectionTypes;
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pub use self::project::{normalize, normalize_projection_type, poly_project_and_unify_type};
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pub use self::project::{ProjectionCache, ProjectionCacheSnapshot, Reveal, Normalized};
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pub use self::object_safety::ObjectSafetyViolation;
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pub use self::object_safety::MethodViolationCode;
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pub use self::on_unimplemented::{OnUnimplementedDirective, OnUnimplementedNote};
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pub use self::select::{EvaluationCache, SelectionContext, SelectionCache};
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pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError};
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pub use self::specialize::{OverlapError, specialization_graph, translate_substs};
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pub use self::specialize::{SpecializesCache, find_associated_item};
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pub use self::engine::TraitEngine;
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pub use self::util::elaborate_predicates;
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pub use self::util::supertraits;
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pub use self::util::Supertraits;
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pub use self::util::supertrait_def_ids;
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pub use self::util::SupertraitDefIds;
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pub use self::util::transitive_bounds;
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#[allow(dead_code)]
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pub mod auto_trait;
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mod coherence;
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pub mod error_reporting;
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mod engine;
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mod fulfill;
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mod project;
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mod object_safety;
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mod on_unimplemented;
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mod select;
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mod specialize;
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mod structural_impls;
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pub mod codegen;
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mod util;
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pub mod query;
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// Whether to enable bug compatibility with issue #43355
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub enum IntercrateMode {
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Issue43355,
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Fixed
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}
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// The mode that trait queries run in
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#[derive(Copy, Clone, PartialEq, Eq, Debug)]
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pub enum TraitQueryMode {
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// Standard/un-canonicalized queries get accurate
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// spans etc. passed in and hence can do reasonable
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// error reporting on their own.
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Standard,
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// Canonicalized queries get dummy spans and hence
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// must generally propagate errors to
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// pre-canonicalization callsites.
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Canonical,
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}
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/// An `Obligation` represents some trait reference (e.g. `int:Eq`) for
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/// which the vtable must be found. The process of finding a vtable is
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/// called "resolving" the `Obligation`. This process consists of
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/// either identifying an `impl` (e.g., `impl Eq for int`) that
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/// provides the required vtable, or else finding a bound that is in
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/// scope. The eventual result is usually a `Selection` (defined below).
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#[derive(Clone, PartialEq, Eq, Hash)]
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pub struct Obligation<'tcx, T> {
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/// Why do we have to prove this thing?
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pub cause: ObligationCause<'tcx>,
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/// In which environment should we prove this thing?
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pub param_env: ty::ParamEnv<'tcx>,
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/// What are we trying to prove?
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pub predicate: T,
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/// If we started proving this as a result of trying to prove
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/// something else, track the total depth to ensure termination.
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/// If this goes over a certain threshold, we abort compilation --
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/// in such cases, we can not say whether or not the predicate
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/// holds for certain. Stupid halting problem. Such a drag.
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pub recursion_depth: usize,
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}
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pub type PredicateObligation<'tcx> = Obligation<'tcx, ty::Predicate<'tcx>>;
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pub type TraitObligation<'tcx> = Obligation<'tcx, ty::PolyTraitPredicate<'tcx>>;
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/// Why did we incur this obligation? Used for error reporting.
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#[derive(Clone, Debug, PartialEq, Eq, Hash)]
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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: ast::NodeId,
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pub code: ObligationCauseCode<'tcx>
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}
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impl<'tcx> ObligationCause<'tcx> {
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pub fn span<'a, 'gcx>(&self, tcx: &TyCtxt<'a, 'gcx, 'tcx>) -> Span {
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match self.code {
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ObligationCauseCode::CompareImplMethodObligation { .. } |
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ObligationCauseCode::MainFunctionType |
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ObligationCauseCode::StartFunctionType => {
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tcx.sess.codemap().def_span(self.span)
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}
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_ => self.span,
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}
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}
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}
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#[derive(Clone, Debug, PartialEq, Eq, Hash)]
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pub enum ObligationCauseCode<'tcx> {
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/// Not well classified or should be obvious from 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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/// This is the trait reference from the given projection
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ProjectionWf(ty::ProjectionTy<'tcx>),
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/// In an impl of trait X for type Y, type Y must
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/// also implement all supertraits of X.
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ItemObligation(DefId),
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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 an object cast.
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ObjectCastObligation(/* Object type */ Ty<'tcx>),
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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(ast::NodeId),
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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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/// [T,..n] --> T must be Copy
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RepeatVec,
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/// Types of fields (other than the last) in a struct must be sized.
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FieldSized(AdtKind),
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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(DerivedObligationCause<'tcx>),
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/// error derived when matching traits/impls; see ObligationCause for more details
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CompareImplMethodObligation {
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item_name: ast::Name,
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impl_item_def_id: DefId,
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trait_item_def_id: DefId,
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},
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/// Checking that this expression can be assigned where it needs to be
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// FIXME(eddyb) #11161 is the original Expr required?
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ExprAssignable,
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/// Computing common supertype in the arms of a match expression
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MatchExpressionArm { arm_span: Span,
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source: hir::MatchSource },
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/// Computing common supertype in an if expression
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IfExpression,
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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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/// intrinsic has wrong type
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IntrinsicType,
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/// method receiver
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MethodReceiver,
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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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ReturnType(ast::NodeId),
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/// Block implicit return
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BlockTailExpression(ast::NodeId),
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/// #[feature(trivial_bounds)] is not enabled
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TrivialBound,
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}
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#[derive(Clone, Debug, PartialEq, Eq, Hash)]
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pub struct DerivedObligationCause<'tcx> {
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/// The trait reference of the parent obligation that led to the
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/// current obligation. Note that only trait obligations lead to
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/// derived obligations, so we just store the trait reference here
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/// directly.
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parent_trait_ref: ty::PolyTraitRef<'tcx>,
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/// The parent trait had this cause
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parent_code: Rc<ObligationCauseCode<'tcx>>
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}
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pub type Obligations<'tcx, O> = Vec<Obligation<'tcx, O>>;
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pub type PredicateObligations<'tcx> = Vec<PredicateObligation<'tcx>>;
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pub type TraitObligations<'tcx> = Vec<TraitObligation<'tcx>>;
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/// The following types:
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/// * `WhereClauseAtom`
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/// * `DomainGoal`
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/// * `Goal`
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/// * `Clause`
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/// are used for representing the trait system in the form of
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/// logic programming clauses. They are part of the interface
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/// for the chalk SLG solver.
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#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
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pub enum WhereClauseAtom<'tcx> {
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Implemented(ty::TraitPredicate<'tcx>),
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ProjectionEq(ty::ProjectionPredicate<'tcx>),
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}
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#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
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pub enum DomainGoal<'tcx> {
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Holds(WhereClauseAtom<'tcx>),
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WellFormed(WhereClauseAtom<'tcx>),
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FromEnv(WhereClauseAtom<'tcx>),
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WellFormedTy(Ty<'tcx>),
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Normalize(ty::ProjectionPredicate<'tcx>),
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FromEnvTy(Ty<'tcx>),
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RegionOutlives(ty::RegionOutlivesPredicate<'tcx>),
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TypeOutlives(ty::TypeOutlivesPredicate<'tcx>),
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}
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pub type PolyDomainGoal<'tcx> = ty::Binder<DomainGoal<'tcx>>;
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
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pub enum QuantifierKind {
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Universal,
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Existential,
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}
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
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pub enum Goal<'tcx> {
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Implies(Clauses<'tcx>, &'tcx Goal<'tcx>),
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And(&'tcx Goal<'tcx>, &'tcx Goal<'tcx>),
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Not(&'tcx Goal<'tcx>),
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DomainGoal(DomainGoal<'tcx>),
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Quantified(QuantifierKind, ty::Binder<&'tcx Goal<'tcx>>),
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CannotProve,
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}
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pub type Goals<'tcx> = &'tcx Slice<Goal<'tcx>>;
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impl<'tcx> Goal<'tcx> {
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pub fn from_poly_domain_goal<'a>(
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domain_goal: PolyDomainGoal<'tcx>,
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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) -> Goal<'tcx> {
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match domain_goal.no_late_bound_regions() {
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Some(p) => p.into(),
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None => Goal::Quantified(
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QuantifierKind::Universal,
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domain_goal.map_bound(|p| tcx.mk_goal(Goal::from(p)))
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),
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}
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}
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}
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impl<'tcx> From<DomainGoal<'tcx>> for Goal<'tcx> {
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fn from(domain_goal: DomainGoal<'tcx>) -> Self {
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Goal::DomainGoal(domain_goal)
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}
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}
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/// This matches the definition from Page 7 of "A Proof Procedure for the Logic of Hereditary
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/// Harrop Formulas".
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
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pub enum Clause<'tcx> {
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Implies(ProgramClause<'tcx>),
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ForAll(ty::Binder<ProgramClause<'tcx>>),
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}
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/// Multiple clauses.
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pub type Clauses<'tcx> = &'tcx Slice<Clause<'tcx>>;
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/// A "program clause" has the form `D :- G1, ..., Gn`. It is saying
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/// that the domain goal `D` is true if `G1...Gn` are provable. This
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/// is equivalent to the implication `G1..Gn => D`; we usually write
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/// it with the reverse implication operator `:-` to emphasize the way
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/// that programs are actually solved (via backchaining, which starts
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/// with the goal to solve and proceeds from there).
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#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
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pub struct ProgramClause<'tcx> {
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/// This goal will be considered true...
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pub goal: DomainGoal<'tcx>,
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/// ...if we can prove these hypotheses (there may be no hypotheses at all):
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pub hypotheses: Goals<'tcx>,
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}
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pub type Selection<'tcx> = Vtable<'tcx, PredicateObligation<'tcx>>;
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#[derive(Clone,Debug)]
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pub enum SelectionError<'tcx> {
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Unimplemented,
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OutputTypeParameterMismatch(ty::PolyTraitRef<'tcx>,
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ty::PolyTraitRef<'tcx>,
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ty::error::TypeError<'tcx>),
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TraitNotObjectSafe(DefId),
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ConstEvalFailure(ConstEvalErr<'tcx>),
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Overflow,
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}
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pub struct FulfillmentError<'tcx> {
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pub obligation: PredicateObligation<'tcx>,
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pub code: FulfillmentErrorCode<'tcx>
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}
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#[derive(Clone)]
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pub enum FulfillmentErrorCode<'tcx> {
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CodeSelectionError(SelectionError<'tcx>),
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CodeProjectionError(MismatchedProjectionTypes<'tcx>),
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CodeSubtypeError(ExpectedFound<Ty<'tcx>>,
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TypeError<'tcx>), // always comes from a SubtypePredicate
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CodeAmbiguity,
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}
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/// When performing resolution, it is typically the case that there
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/// can be one of three outcomes:
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///
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/// - `Ok(Some(r))`: success occurred with result `r`
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/// - `Ok(None)`: could not definitely determine anything, usually due
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/// to inconclusive type inference.
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/// - `Err(e)`: error `e` occurred
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pub type SelectionResult<'tcx, T> = Result<Option<T>, SelectionError<'tcx>>;
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/// Given the successful resolution of an obligation, the `Vtable`
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/// indicates where the vtable comes from. Note that while we call this
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/// a "vtable", it does not necessarily indicate dynamic dispatch at
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/// runtime. `Vtable` instances just tell the compiler where to find
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/// methods, but in generic code those methods are typically statically
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/// dispatched -- only when an object is constructed is a `Vtable`
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/// instance reified into an actual vtable.
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///
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/// For example, the vtable may be tied to a specific impl (case A),
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/// or it may be relative to some bound that is in scope (case B).
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///
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///
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/// ```
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/// impl<T:Clone> Clone<T> for Option<T> { ... } // Impl_1
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/// impl<T:Clone> Clone<T> for Box<T> { ... } // Impl_2
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/// impl Clone for int { ... } // Impl_3
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///
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/// fn foo<T:Clone>(concrete: Option<Box<int>>,
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/// param: T,
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/// mixed: Option<T>) {
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///
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/// // Case A: Vtable points at a specific impl. Only possible when
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/// // type is concretely known. If the impl itself has bounded
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/// // type parameters, Vtable will carry resolutions for those as well:
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/// concrete.clone(); // Vtable(Impl_1, [Vtable(Impl_2, [Vtable(Impl_3)])])
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///
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/// // Case B: Vtable must be provided by caller. This applies when
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/// // type is a type parameter.
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/// param.clone(); // VtableParam
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///
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/// // Case C: A mix of cases A and B.
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/// mixed.clone(); // Vtable(Impl_1, [VtableParam])
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/// }
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/// ```
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///
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/// ### The type parameter `N`
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///
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/// See explanation on `VtableImplData`.
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#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
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pub enum Vtable<'tcx, N> {
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/// Vtable identifying a particular impl.
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VtableImpl(VtableImplData<'tcx, N>),
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/// Vtable for auto trait implementations
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/// This carries the information and nested obligations with regards
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/// to an auto implementation for a trait `Trait`. The nested obligations
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/// ensure the trait implementation holds for all the constituent types.
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VtableAutoImpl(VtableAutoImplData<N>),
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/// Successful resolution to an obligation provided by the caller
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/// for some type parameter. The `Vec<N>` represents the
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/// obligations incurred from normalizing the where-clause (if
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/// any).
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VtableParam(Vec<N>),
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/// Virtual calls through an object
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VtableObject(VtableObjectData<'tcx, N>),
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/// Successful resolution for a builtin trait.
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VtableBuiltin(VtableBuiltinData<N>),
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/// Vtable automatically generated for a closure. The def ID is the ID
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/// of the closure expression. This is a `VtableImpl` in spirit, but the
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/// impl is generated by the compiler and does not appear in the source.
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VtableClosure(VtableClosureData<'tcx, N>),
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/// Same as above, but for a fn pointer type with the given signature.
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VtableFnPointer(VtableFnPointerData<'tcx, N>),
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/// Vtable automatically generated for a generator
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VtableGenerator(VtableGeneratorData<'tcx, N>),
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}
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/// Identifies a particular impl in the source, along with a set of
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/// substitutions from the impl's type/lifetime parameters. The
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/// `nested` vector corresponds to the nested obligations attached to
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/// the impl's type parameters.
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///
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/// 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, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableImplData<'tcx, N> {
|
|
pub impl_def_id: DefId,
|
|
pub substs: &'tcx Substs<'tcx>,
|
|
pub nested: Vec<N>
|
|
}
|
|
|
|
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableGeneratorData<'tcx, N> {
|
|
pub generator_def_id: DefId,
|
|
pub substs: ty::GeneratorSubsts<'tcx>,
|
|
/// Nested obligations. This can be non-empty if the generator
|
|
/// signature contains associated types.
|
|
pub nested: Vec<N>
|
|
}
|
|
|
|
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableClosureData<'tcx, N> {
|
|
pub closure_def_id: DefId,
|
|
pub substs: ty::ClosureSubsts<'tcx>,
|
|
/// Nested obligations. This can be non-empty if the closure
|
|
/// signature contains associated types.
|
|
pub nested: Vec<N>
|
|
}
|
|
|
|
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableAutoImplData<N> {
|
|
pub trait_def_id: DefId,
|
|
pub nested: Vec<N>
|
|
}
|
|
|
|
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableBuiltinData<N> {
|
|
pub nested: Vec<N>
|
|
}
|
|
|
|
/// A vtable for some object-safe trait `Foo` automatically derived
|
|
/// for the object type `Foo`.
|
|
#[derive(PartialEq, Eq, Clone, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableObjectData<'tcx, N> {
|
|
/// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
|
|
pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
|
|
|
|
/// The vtable is formed by concatenating together the method lists of
|
|
/// the base object trait and all supertraits; this is the start of
|
|
/// `upcast_trait_ref`'s methods in that vtable.
|
|
pub vtable_base: usize,
|
|
|
|
pub nested: Vec<N>,
|
|
}
|
|
|
|
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
|
|
pub struct VtableFnPointerData<'tcx, N> {
|
|
pub fn_ty: Ty<'tcx>,
|
|
pub nested: Vec<N>
|
|
}
|
|
|
|
/// Creates predicate obligations from the generic bounds.
|
|
pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
generic_bounds: &ty::InstantiatedPredicates<'tcx>)
|
|
-> PredicateObligations<'tcx>
|
|
{
|
|
util::predicates_for_generics(cause, 0, param_env, generic_bounds)
|
|
}
|
|
|
|
/// Determines whether the type `ty` is known to meet `bound` and
|
|
/// returns true if so. Returns false if `ty` either does not meet
|
|
/// `bound` or is not known to meet bound (note that this is
|
|
/// conservative towards *no impl*, which is the opposite of the
|
|
/// `evaluate` methods).
|
|
pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
ty: Ty<'tcx>,
|
|
def_id: DefId,
|
|
span: Span)
|
|
-> bool
|
|
{
|
|
debug!("type_known_to_meet_bound(ty={:?}, bound={:?})",
|
|
ty,
|
|
infcx.tcx.item_path_str(def_id));
|
|
|
|
let trait_ref = ty::TraitRef {
|
|
def_id,
|
|
substs: infcx.tcx.mk_substs_trait(ty, &[]),
|
|
};
|
|
let obligation = Obligation {
|
|
param_env,
|
|
cause: ObligationCause::misc(span, ast::DUMMY_NODE_ID),
|
|
recursion_depth: 0,
|
|
predicate: trait_ref.to_predicate(),
|
|
};
|
|
|
|
let result = infcx.predicate_must_hold(&obligation);
|
|
debug!("type_known_to_meet_ty={:?} bound={} => {:?}",
|
|
ty, infcx.tcx.item_path_str(def_id), result);
|
|
|
|
if result && (ty.has_infer_types() || ty.has_closure_types()) {
|
|
// Because of inference "guessing", selection can sometimes claim
|
|
// to succeed while the success requires a guess. To ensure
|
|
// this function's result remains infallible, we must confirm
|
|
// that guess. While imperfect, I believe this is sound.
|
|
|
|
// The handling of regions in this area of the code is terrible,
|
|
// see issue #29149. We should be able to improve on this with
|
|
// NLL.
|
|
let mut fulfill_cx = FulfillmentContext::new_ignoring_regions();
|
|
|
|
// We can use a dummy node-id here because we won't pay any mind
|
|
// to region obligations that arise (there shouldn't really be any
|
|
// anyhow).
|
|
let cause = ObligationCause::misc(span, ast::DUMMY_NODE_ID);
|
|
|
|
fulfill_cx.register_bound(infcx, param_env, ty, def_id, cause);
|
|
|
|
// Note: we only assume something is `Copy` if we can
|
|
// *definitively* show that it implements `Copy`. Otherwise,
|
|
// assume it is move; linear is always ok.
|
|
match fulfill_cx.select_all_or_error(infcx) {
|
|
Ok(()) => {
|
|
debug!("type_known_to_meet_bound: ty={:?} bound={} success",
|
|
ty,
|
|
infcx.tcx.item_path_str(def_id));
|
|
true
|
|
}
|
|
Err(e) => {
|
|
debug!("type_known_to_meet_bound: ty={:?} bound={} errors={:?}",
|
|
ty,
|
|
infcx.tcx.item_path_str(def_id),
|
|
e);
|
|
false
|
|
}
|
|
}
|
|
} else {
|
|
result
|
|
}
|
|
}
|
|
|
|
// FIXME: this is gonna need to be removed ...
|
|
/// Normalizes the parameter environment, reporting errors if they occur.
|
|
pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
region_context: DefId,
|
|
unnormalized_env: ty::ParamEnv<'tcx>,
|
|
cause: ObligationCause<'tcx>)
|
|
-> ty::ParamEnv<'tcx>
|
|
{
|
|
// I'm not wild about reporting errors here; I'd prefer to
|
|
// have the errors get reported at a defined place (e.g.,
|
|
// during typeck). Instead I have all parameter
|
|
// environments, in effect, going through this function
|
|
// and hence potentially reporting errors. This ensurse of
|
|
// course that we never forget to normalize (the
|
|
// alternative seemed like it would involve a lot of
|
|
// manual invocations of this fn -- and then we'd have to
|
|
// deal with the errors at each of those sites).
|
|
//
|
|
// In any case, in practice, typeck constructs all the
|
|
// parameter environments once for every fn as it goes,
|
|
// and errors will get reported then; so after typeck we
|
|
// can be sure that no errors should occur.
|
|
|
|
let span = cause.span;
|
|
|
|
debug!("normalize_param_env_or_error(unnormalized_env={:?})",
|
|
unnormalized_env);
|
|
|
|
let predicates: Vec<_> =
|
|
util::elaborate_predicates(tcx, unnormalized_env.caller_bounds.to_vec())
|
|
.collect();
|
|
|
|
debug!("normalize_param_env_or_error: elaborated-predicates={:?}",
|
|
predicates);
|
|
|
|
let elaborated_env = ty::ParamEnv::new(tcx.intern_predicates(&predicates),
|
|
unnormalized_env.reveal);
|
|
|
|
tcx.infer_ctxt().enter(|infcx| {
|
|
// FIXME. We should really... do something with these region
|
|
// obligations. But this call just continues the older
|
|
// behavior (i.e., doesn't cause any new bugs), and it would
|
|
// take some further refactoring to actually solve them. In
|
|
// particular, we would have to handle implied bounds
|
|
// properly, and that code is currently largely confined to
|
|
// regionck (though I made some efforts to extract it
|
|
// out). -nmatsakis
|
|
//
|
|
// @arielby: In any case, these obligations are checked
|
|
// by wfcheck anyway, so I'm not sure we have to check
|
|
// them here too, and we will remove this function when
|
|
// we move over to lazy normalization *anyway*.
|
|
let fulfill_cx = FulfillmentContext::new_ignoring_regions();
|
|
|
|
let predicates = match fully_normalize(
|
|
&infcx,
|
|
fulfill_cx,
|
|
cause,
|
|
elaborated_env,
|
|
// You would really want to pass infcx.param_env.caller_bounds here,
|
|
// but that is an interned slice, and fully_normalize takes &T and returns T, so
|
|
// without further refactoring, a slice can't be used. Luckily, we still have the
|
|
// predicate vector from which we created the ParamEnv in infcx, so we
|
|
// can pass that instead. It's roundabout and a bit brittle, but this code path
|
|
// ought to be refactored anyway, and until then it saves us from having to copy.
|
|
&predicates,
|
|
) {
|
|
Ok(predicates) => predicates,
|
|
Err(errors) => {
|
|
infcx.report_fulfillment_errors(&errors, None, false);
|
|
// An unnormalized env is better than nothing.
|
|
return elaborated_env;
|
|
}
|
|
};
|
|
|
|
debug!("normalize_param_env_or_error: normalized predicates={:?}",
|
|
predicates);
|
|
|
|
let region_scope_tree = region::ScopeTree::default();
|
|
|
|
// We can use the `elaborated_env` here; the region code only
|
|
// cares about declarations like `'a: 'b`.
|
|
let outlives_env = OutlivesEnvironment::new(elaborated_env);
|
|
|
|
infcx.resolve_regions_and_report_errors(region_context, ®ion_scope_tree, &outlives_env);
|
|
|
|
let predicates = match infcx.fully_resolve(&predicates) {
|
|
Ok(predicates) => predicates,
|
|
Err(fixup_err) => {
|
|
// If we encounter a fixup error, it means that some type
|
|
// variable wound up unconstrained. I actually don't know
|
|
// if this can happen, and I certainly don't expect it to
|
|
// happen often, but if it did happen it probably
|
|
// represents a legitimate failure due to some kind of
|
|
// unconstrained variable, and it seems better not to ICE,
|
|
// all things considered.
|
|
tcx.sess.span_err(span, &fixup_err.to_string());
|
|
// An unnormalized env is better than nothing.
|
|
return elaborated_env;
|
|
}
|
|
};
|
|
|
|
let predicates = match tcx.lift_to_global(&predicates) {
|
|
Some(predicates) => predicates,
|
|
None => return elaborated_env,
|
|
};
|
|
|
|
debug!("normalize_param_env_or_error: resolved predicates={:?}",
|
|
predicates);
|
|
|
|
ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal)
|
|
})
|
|
}
|
|
|
|
pub fn fully_normalize<'a, 'gcx, 'tcx, T>(
|
|
infcx: &InferCtxt<'a, 'gcx, 'tcx>,
|
|
mut fulfill_cx: FulfillmentContext<'tcx>,
|
|
cause: ObligationCause<'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
value: &T)
|
|
-> Result<T, Vec<FulfillmentError<'tcx>>>
|
|
where T : TypeFoldable<'tcx>
|
|
{
|
|
debug!("fully_normalize_with_fulfillcx(value={:?})", value);
|
|
let selcx = &mut SelectionContext::new(infcx);
|
|
let Normalized { value: normalized_value, obligations } =
|
|
project::normalize(selcx, param_env, cause, value);
|
|
debug!("fully_normalize: normalized_value={:?} obligations={:?}",
|
|
normalized_value,
|
|
obligations);
|
|
for obligation in obligations {
|
|
fulfill_cx.register_predicate_obligation(selcx.infcx(), obligation);
|
|
}
|
|
|
|
debug!("fully_normalize: select_all_or_error start");
|
|
fulfill_cx.select_all_or_error(infcx)?;
|
|
debug!("fully_normalize: select_all_or_error complete");
|
|
let resolved_value = infcx.resolve_type_vars_if_possible(&normalized_value);
|
|
debug!("fully_normalize: resolved_value={:?}", resolved_value);
|
|
Ok(resolved_value)
|
|
}
|
|
|
|
/// Normalizes the predicates and checks whether they hold in an empty
|
|
/// environment. If this returns false, then either normalize
|
|
/// encountered an error or one of the predicates did not hold. Used
|
|
/// when creating vtables to check for unsatisfiable methods.
|
|
fn normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
predicates: Vec<ty::Predicate<'tcx>>)
|
|
-> bool
|
|
{
|
|
debug!("normalize_and_test_predicates(predicates={:?})",
|
|
predicates);
|
|
|
|
let result = tcx.infer_ctxt().enter(|infcx| {
|
|
let param_env = ty::ParamEnv::reveal_all();
|
|
let mut selcx = SelectionContext::new(&infcx);
|
|
let mut fulfill_cx = FulfillmentContext::new();
|
|
let cause = ObligationCause::dummy();
|
|
let Normalized { value: predicates, obligations } =
|
|
normalize(&mut selcx, param_env, cause.clone(), &predicates);
|
|
for obligation in obligations {
|
|
fulfill_cx.register_predicate_obligation(&infcx, obligation);
|
|
}
|
|
for predicate in predicates {
|
|
let obligation = Obligation::new(cause.clone(), param_env, predicate);
|
|
fulfill_cx.register_predicate_obligation(&infcx, obligation);
|
|
}
|
|
|
|
fulfill_cx.select_all_or_error(&infcx).is_ok()
|
|
});
|
|
debug!("normalize_and_test_predicates(predicates={:?}) = {:?}",
|
|
predicates, result);
|
|
result
|
|
}
|
|
|
|
fn substitute_normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
key: (DefId, &'tcx Substs<'tcx>))
|
|
-> bool
|
|
{
|
|
use ty::subst::Subst;
|
|
debug!("substitute_normalize_and_test_predicates(key={:?})",
|
|
key);
|
|
|
|
let predicates = tcx.predicates_of(key.0).predicates.subst(tcx, key.1);
|
|
let result = normalize_and_test_predicates(tcx, predicates);
|
|
|
|
debug!("substitute_normalize_and_test_predicates(key={:?}) = {:?}",
|
|
key, result);
|
|
result
|
|
}
|
|
|
|
/// Given a trait `trait_ref`, iterates the vtable entries
|
|
/// that come from `trait_ref`, including its supertraits.
|
|
#[inline] // FIXME(#35870) Avoid closures being unexported due to impl Trait.
|
|
fn vtable_methods<'a, 'tcx>(
|
|
tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
|
trait_ref: ty::PolyTraitRef<'tcx>)
|
|
-> Lrc<Vec<Option<(DefId, &'tcx Substs<'tcx>)>>>
|
|
{
|
|
debug!("vtable_methods({:?})", trait_ref);
|
|
|
|
Lrc::new(
|
|
supertraits(tcx, trait_ref).flat_map(move |trait_ref| {
|
|
let trait_methods = tcx.associated_items(trait_ref.def_id())
|
|
.filter(|item| item.kind == ty::AssociatedKind::Method);
|
|
|
|
// Now list each method's DefId and Substs (for within its trait).
|
|
// If the method can never be called from this object, produce None.
|
|
trait_methods.map(move |trait_method| {
|
|
debug!("vtable_methods: trait_method={:?}", trait_method);
|
|
let def_id = trait_method.def_id;
|
|
|
|
// Some methods cannot be called on an object; skip those.
|
|
if !tcx.is_vtable_safe_method(trait_ref.def_id(), &trait_method) {
|
|
debug!("vtable_methods: not vtable safe");
|
|
return None;
|
|
}
|
|
|
|
// the method may have some early-bound lifetimes, add
|
|
// regions for those
|
|
let substs = trait_ref.map_bound(|trait_ref| {
|
|
Substs::for_item(tcx, def_id, |param, _| {
|
|
match param.kind {
|
|
GenericParamDefKind::Lifetime => tcx.types.re_erased.into(),
|
|
GenericParamDefKind::Type(_) => {
|
|
trait_ref.substs[param.index as usize]
|
|
}
|
|
}
|
|
})
|
|
});
|
|
|
|
// the trait type may have higher-ranked lifetimes in it;
|
|
// so erase them if they appear, so that we get the type
|
|
// at some particular call site
|
|
let substs = tcx.normalize_erasing_late_bound_regions(
|
|
ty::ParamEnv::reveal_all(),
|
|
&substs
|
|
);
|
|
|
|
// It's possible that the method relies on where clauses that
|
|
// do not hold for this particular set of type parameters.
|
|
// Note that this method could then never be called, so we
|
|
// do not want to try and codegen it, in that case (see #23435).
|
|
let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
|
|
if !normalize_and_test_predicates(tcx, predicates.predicates) {
|
|
debug!("vtable_methods: predicates do not hold");
|
|
return None;
|
|
}
|
|
|
|
Some((def_id, substs))
|
|
})
|
|
}).collect()
|
|
)
|
|
}
|
|
|
|
impl<'tcx,O> Obligation<'tcx,O> {
|
|
pub fn new(cause: ObligationCause<'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
predicate: O)
|
|
-> Obligation<'tcx, O>
|
|
{
|
|
Obligation { cause, param_env, recursion_depth: 0, predicate }
|
|
}
|
|
|
|
fn with_depth(cause: ObligationCause<'tcx>,
|
|
recursion_depth: usize,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
predicate: O)
|
|
-> Obligation<'tcx, O>
|
|
{
|
|
Obligation { cause, param_env, recursion_depth, predicate }
|
|
}
|
|
|
|
pub fn misc(span: Span,
|
|
body_id: ast::NodeId,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
trait_ref: O)
|
|
-> Obligation<'tcx, O> {
|
|
Obligation::new(ObligationCause::misc(span, body_id), param_env, trait_ref)
|
|
}
|
|
|
|
pub fn with<P>(&self, value: P) -> Obligation<'tcx,P> {
|
|
Obligation { cause: self.cause.clone(),
|
|
param_env: self.param_env,
|
|
recursion_depth: self.recursion_depth,
|
|
predicate: value }
|
|
}
|
|
}
|
|
|
|
impl<'tcx> ObligationCause<'tcx> {
|
|
pub fn new(span: Span,
|
|
body_id: ast::NodeId,
|
|
code: ObligationCauseCode<'tcx>)
|
|
-> ObligationCause<'tcx> {
|
|
ObligationCause { span: span, body_id: body_id, code: code }
|
|
}
|
|
|
|
pub fn misc(span: Span, body_id: ast::NodeId) -> ObligationCause<'tcx> {
|
|
ObligationCause { span: span, body_id: body_id, code: MiscObligation }
|
|
}
|
|
|
|
pub fn dummy() -> ObligationCause<'tcx> {
|
|
ObligationCause { span: DUMMY_SP, body_id: ast::CRATE_NODE_ID, code: MiscObligation }
|
|
}
|
|
}
|
|
|
|
impl<'tcx, N> Vtable<'tcx, N> {
|
|
pub fn nested_obligations(self) -> Vec<N> {
|
|
match self {
|
|
VtableImpl(i) => i.nested,
|
|
VtableParam(n) => n,
|
|
VtableBuiltin(i) => i.nested,
|
|
VtableAutoImpl(d) => d.nested,
|
|
VtableClosure(c) => c.nested,
|
|
VtableGenerator(c) => c.nested,
|
|
VtableObject(d) => d.nested,
|
|
VtableFnPointer(d) => d.nested,
|
|
}
|
|
}
|
|
|
|
pub fn map<M, F>(self, f: F) -> Vtable<'tcx, M> where F: FnMut(N) -> M {
|
|
match self {
|
|
VtableImpl(i) => VtableImpl(VtableImplData {
|
|
impl_def_id: i.impl_def_id,
|
|
substs: i.substs,
|
|
nested: i.nested.into_iter().map(f).collect(),
|
|
}),
|
|
VtableParam(n) => VtableParam(n.into_iter().map(f).collect()),
|
|
VtableBuiltin(i) => VtableBuiltin(VtableBuiltinData {
|
|
nested: i.nested.into_iter().map(f).collect(),
|
|
}),
|
|
VtableObject(o) => VtableObject(VtableObjectData {
|
|
upcast_trait_ref: o.upcast_trait_ref,
|
|
vtable_base: o.vtable_base,
|
|
nested: o.nested.into_iter().map(f).collect(),
|
|
}),
|
|
VtableAutoImpl(d) => VtableAutoImpl(VtableAutoImplData {
|
|
trait_def_id: d.trait_def_id,
|
|
nested: d.nested.into_iter().map(f).collect(),
|
|
}),
|
|
VtableFnPointer(p) => VtableFnPointer(VtableFnPointerData {
|
|
fn_ty: p.fn_ty,
|
|
nested: p.nested.into_iter().map(f).collect(),
|
|
}),
|
|
VtableGenerator(c) => VtableGenerator(VtableGeneratorData {
|
|
generator_def_id: c.generator_def_id,
|
|
substs: c.substs,
|
|
nested: c.nested.into_iter().map(f).collect(),
|
|
}),
|
|
VtableClosure(c) => VtableClosure(VtableClosureData {
|
|
closure_def_id: c.closure_def_id,
|
|
substs: c.substs,
|
|
nested: c.nested.into_iter().map(f).collect(),
|
|
})
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> FulfillmentError<'tcx> {
|
|
fn new(obligation: PredicateObligation<'tcx>,
|
|
code: FulfillmentErrorCode<'tcx>)
|
|
-> FulfillmentError<'tcx>
|
|
{
|
|
FulfillmentError { obligation: obligation, code: code }
|
|
}
|
|
}
|
|
|
|
impl<'tcx> TraitObligation<'tcx> {
|
|
fn self_ty(&self) -> ty::Binder<Ty<'tcx>> {
|
|
self.predicate.map_bound(|p| p.self_ty())
|
|
}
|
|
}
|
|
|
|
pub fn provide(providers: &mut ty::maps::Providers) {
|
|
*providers = ty::maps::Providers {
|
|
is_object_safe: object_safety::is_object_safe_provider,
|
|
specialization_graph_of: specialize::specialization_graph_provider,
|
|
specializes: specialize::specializes,
|
|
codegen_fulfill_obligation: codegen::codegen_fulfill_obligation,
|
|
vtable_methods,
|
|
substitute_normalize_and_test_predicates,
|
|
..*providers
|
|
};
|
|
}
|