diff --git a/compiler/rustc_trait_selection/src/solve/assembly.rs b/compiler/rustc_trait_selection/src/solve/assembly.rs
index d23b550621e17..61319a3ed7c19 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly.rs
@@ -1,6 +1,8 @@
//! Code shared by trait and projection goals for candidate assembly.
use super::infcx_ext::InferCtxtExt;
+#[cfg(doc)]
+use super::trait_goals::structural_traits::*;
use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, QueryResult};
use rustc_hir::def_id::DefId;
use rustc_infer::traits::query::NoSolution;
@@ -98,52 +100,75 @@ pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy + Eq {
assumption: ty::Predicate<'tcx>,
) -> QueryResult<'tcx>;
+ // A type implements an `auto trait` if its components do as well. These components
+ // are given by built-in rules from [`instantiate_constituent_tys_for_auto_trait`].
fn consider_auto_trait_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A trait alias holds if the RHS traits and `where` clauses hold.
fn consider_trait_alias_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A type is `Copy` or `Clone` if its components are `Sized`. These components
+ // are given by built-in rules from [`instantiate_constituent_tys_for_sized_trait`].
fn consider_builtin_sized_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A type is `Copy` or `Clone` if its components are `Copy` or `Clone`. These
+ // components are given by built-in rules from [`instantiate_constituent_tys_for_copy_clone_trait`].
fn consider_builtin_copy_clone_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A type is `PointerSized` if we can compute its layout, and that layout
+ // matches the layout of `usize`.
fn consider_builtin_pointer_sized_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A callable type (a closure, fn def, or fn ptr) is known to implement the `Fn<A>`
+ // family of traits where `A` is given by the signature of the type.
fn consider_builtin_fn_trait_candidates(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
kind: ty::ClosureKind,
) -> QueryResult<'tcx>;
+ // `Tuple` is implemented if the `Self` type is a tuple.
fn consider_builtin_tuple_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // `Pointee` is always implemented.
+ //
+ // See the projection implementation for the `Metadata` types for all of
+ // the built-in types. For structs, the metadata type is given by the struct
+ // tail.
fn consider_builtin_pointee_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A generator (that comes from an `async` desugaring) is known to implement
+ // `Future<Output = O>`, where `O` is given by the generator's return type
+ // that was computed during type-checking.
fn consider_builtin_future_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
+ // A generator (that doesn't come from an `async` desugaring) is known to
+ // implement `Generator<R, Yield = Y, Return = O>`, given the resume, yield,
+ // and return types of the generator computed during type-checking.
fn consider_builtin_generator_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index f44648c95d742..cc7bb94537673 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -337,15 +337,13 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
// That won't actually reflect in the query response, so it seems moot.
self.make_canonical_response(Certainty::AMBIGUOUS)
} else {
- self.infcx.probe(|_| {
- let InferOk { value: (), obligations } = self
- .infcx
- .at(&ObligationCause::dummy(), goal.param_env)
- .sub(goal.predicate.a, goal.predicate.b)?;
- self.evaluate_all_and_make_canonical_response(
- obligations.into_iter().map(|pred| pred.into()).collect(),
- )
- })
+ let InferOk { value: (), obligations } = self
+ .infcx
+ .at(&ObligationCause::dummy(), goal.param_env)
+ .sub(goal.predicate.a, goal.predicate.b)?;
+ self.evaluate_all_and_make_canonical_response(
+ obligations.into_iter().map(|pred| pred.into()).collect(),
+ )
}
}
@@ -378,22 +376,22 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
&mut self,
goal: Goal<'tcx, ty::GenericArg<'tcx>>,
) -> QueryResult<'tcx> {
- self.infcx.probe(|_| {
- match crate::traits::wf::unnormalized_obligations(
- self.infcx,
- goal.param_env,
- goal.predicate,
- ) {
- Some(obligations) => self.evaluate_all_and_make_canonical_response(
- obligations.into_iter().map(|o| o.into()).collect(),
- ),
- None => self.make_canonical_response(Certainty::AMBIGUOUS),
- }
- })
+ match crate::traits::wf::unnormalized_obligations(
+ self.infcx,
+ goal.param_env,
+ goal.predicate,
+ ) {
+ Some(obligations) => self.evaluate_all_and_make_canonical_response(
+ obligations.into_iter().map(|o| o.into()).collect(),
+ ),
+ None => self.make_canonical_response(Certainty::AMBIGUOUS),
+ }
}
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
+ // Recursively evaluates a list of goals to completion, returning the certainty
+ // of all of the goals.
fn evaluate_all(
&mut self,
mut goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
@@ -430,6 +428,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
})
}
+ // Recursively evaluates a list of goals to completion, making a query response.
+ //
+ // This is just a convenient way of calling [`EvalCtxt::evaluate_all`],
+ // then [`EvalCtxt::make_canonical_response`].
fn evaluate_all_and_make_canonical_response(
&mut self,
goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs
index b583705ac4369..9da464f283ef3 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs
@@ -296,7 +296,9 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
goal: Goal<'tcx, Self>,
assumption: ty::Predicate<'tcx>,
) -> QueryResult<'tcx> {
- if let Some(poly_projection_pred) = assumption.to_opt_poly_projection_pred() {
+ if let Some(poly_projection_pred) = assumption.to_opt_poly_projection_pred()
+ && poly_projection_pred.projection_def_id() == goal.predicate.def_id()
+ {
ecx.infcx.probe(|_| {
let assumption_projection_pred =
ecx.infcx.instantiate_bound_vars_with_infer(poly_projection_pred);
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index d74857dc4b480..45b6a5f4ec578 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -65,7 +65,9 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
goal: Goal<'tcx, Self>,
assumption: ty::Predicate<'tcx>,
) -> QueryResult<'tcx> {
- if let Some(poly_trait_pred) = assumption.to_opt_poly_trait_pred() {
+ if let Some(poly_trait_pred) = assumption.to_opt_poly_trait_pred()
+ && poly_trait_pred.def_id() == goal.predicate.def_id()
+ {
// FIXME: Constness and polarity
ecx.infcx.probe(|_| {
let assumption_trait_pred =