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Auto merge of #56838 - Aaron1011:fix/rustdoc-infer-unify, r=nikomatsakis
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Call poly_project_and_unify_type on types that contain inference types

Commit f57247c (Ensure that Rusdoc discovers all necessary auto
trait bounds) added a check to ensure that we only attempt to unify a
projection predicatre with inference variables. However, the check it
added was too strict - instead of checking that a type *contains* an
inference variable (e.g. '&_', 'MyType<_>'), it required the type to
*be* an inference variable (i.e. only '_' would match).

This commit relaxes the check to use 'ty.has_infer_types', ensuring that
we perform unification wherever possible.

Fixes #56822
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bors committed Dec 27, 2018
2 parents d174173 + a375410 commit f2b9217
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Showing 2 changed files with 36 additions and 2 deletions.
4 changes: 2 additions & 2 deletions src/librustc/traits/auto_trait.rs
Original file line number Diff line number Diff line change
Expand Up @@ -732,9 +732,9 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
}

// We can only call poly_project_and_unify_type when our predicate's
// Ty is an inference variable - otherwise, there won't be anything to
// Ty contains an inference variable - otherwise, there won't be anything to
// unify
if p.ty().skip_binder().is_ty_infer() {
if p.ty().skip_binder().has_infer_types() {
debug!("Projecting and unifying projection predicate {:?}",
predicate);
match poly_project_and_unify_type(select, &obligation.with(p.clone())) {
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34 changes: 34 additions & 0 deletions src/test/rustdoc/issue-56822.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

struct Wrapper<T>(T);

trait MyTrait {
type Output;
}

impl<'a, I, T: 'a> MyTrait for Wrapper<I>
where I: MyTrait<Output=&'a T>
{
type Output = T;
}

struct Inner<'a, T>(&'a T);

impl<'a, T> MyTrait for Inner<'a, T> {
type Output = &'a T;
}

// @has issue_56822/struct.Parser.html
// @has - '//*[@id="synthetic-implementations-list"]/*[@class="impl"]//*/code' "impl<'a> Send for \
// Parser<'a>"
pub struct Parser<'a> {
field: <Wrapper<Inner<'a, u8>> as MyTrait>::Output
}

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