diff --git a/compiler/rustc_trait_selection/src/solve/assembly.rs b/compiler/rustc_trait_selection/src/solve/assembly.rs index 126ec60b3d68..a9e0c5509a5e 100644 --- a/compiler/rustc_trait_selection/src/solve/assembly.rs +++ b/compiler/rustc_trait_selection/src/solve/assembly.rs @@ -96,10 +96,22 @@ pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy + Eq { impl_def_id: DefId, ) -> QueryResult<'tcx>; + // Consider a predicate we know holds (`assumption`) against a goal we're trying to prove. fn consider_assumption( ecx: &mut EvalCtxt<'_, 'tcx>, goal: Goal<'tcx, Self>, assumption: ty::Predicate<'tcx>, + ) -> QueryResult<'tcx> { + Self::consider_assumption_with_certainty(ecx, goal, assumption, Certainty::Yes) + } + + // Consider a predicate we know holds (`assumption`) against a goal, unifying with + // the `assumption_certainty` if it satisfies the goal. + fn consider_assumption_with_certainty( + ecx: &mut EvalCtxt<'_, 'tcx>, + goal: Goal<'tcx, Self>, + assumption: ty::Predicate<'tcx>, + assumption_certainty: Certainty, ) -> QueryResult<'tcx>; // A type implements an `auto trait` if its components do as well. These components diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs index 883342148f40..adf8a1690c83 100644 --- a/compiler/rustc_trait_selection/src/solve/project_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs @@ -260,10 +260,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { }) } - fn consider_assumption( + fn consider_assumption_with_certainty( ecx: &mut EvalCtxt<'_, 'tcx>, goal: Goal<'tcx, Self>, assumption: ty::Predicate<'tcx>, + assumption_certainty: Certainty, ) -> QueryResult<'tcx> { if let Some(poly_projection_pred) = assumption.to_opt_poly_projection_pred() && poly_projection_pred.projection_def_id() == goal.predicate.def_id() @@ -280,7 +281,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { ecx.eq_term_and_make_canonical_response( goal, - subst_certainty, + subst_certainty.unify_and(assumption_certainty), assumption_projection_pred.term, ) }) @@ -329,22 +330,29 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> { goal: Goal<'tcx, Self>, goal_kind: ty::ClosureKind, ) -> QueryResult<'tcx> { + let tcx = ecx.tcx(); if let Some(tupled_inputs_and_output) = structural_traits::extract_tupled_inputs_and_output_from_callable( - ecx.tcx(), + tcx, goal.predicate.self_ty(), goal_kind, )? { + // A built-in `Fn` trait needs to check that its output is `Sized` + // (FIXME: technically we only need to check this if the type is a fn ptr...) + let output_is_sized_pred = tupled_inputs_and_output + .map_bound(|(_, output)| tcx.at(DUMMY_SP).mk_trait_ref(LangItem::Sized, [output])); + let (_, output_is_sized_certainty) = + ecx.evaluate_goal(goal.with(tcx, output_is_sized_pred))?; + let pred = tupled_inputs_and_output .map_bound(|(inputs, output)| ty::ProjectionPredicate { - projection_ty: ecx - .tcx() + projection_ty: tcx .mk_alias_ty(goal.predicate.def_id(), [goal.predicate.self_ty(), inputs]), term: output.into(), }) - .to_predicate(ecx.tcx()); - Self::consider_assumption(ecx, goal, pred) + .to_predicate(tcx); + Self::consider_assumption_with_certainty(ecx, goal, pred, output_is_sized_certainty) } else { ecx.make_canonical_response(Certainty::AMBIGUOUS) } diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs index d12e5f797fb9..dd47a5ae1507 100644 --- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs @@ -6,6 +6,7 @@ use super::assembly; use super::infcx_ext::InferCtxtExt; use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, QueryResult}; use rustc_hir::def_id::DefId; +use rustc_hir::LangItem; use rustc_infer::infer::InferCtxt; use rustc_infer::traits::query::NoSolution; use rustc_infer::traits::util::supertraits; @@ -61,10 +62,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { }) } - fn consider_assumption( + fn consider_assumption_with_certainty( ecx: &mut EvalCtxt<'_, 'tcx>, goal: Goal<'tcx, Self>, assumption: ty::Predicate<'tcx>, + assumption_certainty: Certainty, ) -> QueryResult<'tcx> { if let Some(poly_trait_pred) = assumption.to_opt_poly_trait_pred() && poly_trait_pred.def_id() == goal.predicate.def_id() @@ -78,7 +80,9 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { goal.predicate.trait_ref, assumption_trait_pred.trait_ref, )?; - ecx.evaluate_all_and_make_canonical_response(nested_goals) + ecx.evaluate_all(nested_goals).and_then(|certainty| { + ecx.make_canonical_response(certainty.unify_and(assumption_certainty)) + }) }) } else { Err(NoSolution) @@ -173,20 +177,27 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { goal: Goal<'tcx, Self>, goal_kind: ty::ClosureKind, ) -> QueryResult<'tcx> { + let tcx = ecx.tcx(); if let Some(tupled_inputs_and_output) = structural_traits::extract_tupled_inputs_and_output_from_callable( - ecx.tcx(), + tcx, goal.predicate.self_ty(), goal_kind, )? { + // A built-in `Fn` trait needs to check that its output is `Sized` + // (FIXME: technically we only need to check this if the type is a fn ptr...) + let output_is_sized_pred = tupled_inputs_and_output + .map_bound(|(_, output)| tcx.at(DUMMY_SP).mk_trait_ref(LangItem::Sized, [output])); + let (_, output_is_sized_certainty) = + ecx.evaluate_goal(goal.with(tcx, output_is_sized_pred))?; + let pred = tupled_inputs_and_output .map_bound(|(inputs, _)| { - ecx.tcx() - .mk_trait_ref(goal.predicate.def_id(), [goal.predicate.self_ty(), inputs]) + tcx.mk_trait_ref(goal.predicate.def_id(), [goal.predicate.self_ty(), inputs]) }) - .to_predicate(ecx.tcx()); - Self::consider_assumption(ecx, goal, pred) + .to_predicate(tcx); + Self::consider_assumption_with_certainty(ecx, goal, pred, output_is_sized_certainty) } else { ecx.make_canonical_response(Certainty::AMBIGUOUS) } diff --git a/tests/ui/traits/new-solver/builtin-fn-must-return-sized.rs b/tests/ui/traits/new-solver/builtin-fn-must-return-sized.rs new file mode 100644 index 000000000000..ba473653ecfe --- /dev/null +++ b/tests/ui/traits/new-solver/builtin-fn-must-return-sized.rs @@ -0,0 +1,17 @@ +// compile-flags: -Ztrait-solver=next + +#![feature(fn_traits)] +#![feature(unboxed_closures)] +#![feature(tuple_trait)] + +use std::ops::Fn; +use std::marker::Tuple; + +fn foo, T: Tuple>(f: Option, t: T) { + let y = (f.unwrap()).call(t); +} + +fn main() { + foo:: str, _>(None, ()); + //~^ expected a `Fn<_>` closure, found `fn() -> str` +} diff --git a/tests/ui/traits/new-solver/builtin-fn-must-return-sized.stderr b/tests/ui/traits/new-solver/builtin-fn-must-return-sized.stderr new file mode 100644 index 000000000000..f7551739b132 --- /dev/null +++ b/tests/ui/traits/new-solver/builtin-fn-must-return-sized.stderr @@ -0,0 +1,18 @@ +error[E0277]: expected a `Fn<_>` closure, found `fn() -> str` + --> $DIR/builtin-fn-must-return-sized.rs:15:27 + | +LL | foo:: str, _>(None, ()); + | --------------------- ^^^^ expected an `Fn<_>` closure, found `fn() -> str` + | | + | required by a bound introduced by this call + | + = help: the trait `Fn<_>` is not implemented for `fn() -> str` +note: required by a bound in `foo` + --> $DIR/builtin-fn-must-return-sized.rs:10:11 + | +LL | fn foo, T: Tuple>(f: Option, t: T) { + | ^^^^^ required by this bound in `foo` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`.