Auto merge of #53580 - nikomatsakis:nll-issue-53568, r=pnkfelix

fix NLL ICEs

Custom type-ops reuse some of the query machinery -- but while query results are canonicalized after they are constructed, custom type ops are not, and hence we have to resolve the type variables to avoid an ICE here.

Also, use the type-op machinery for implied outlives bounds.

Fixes #53568
Fixes #52992
Fixes #53680

src/test/ui/issue-52992.rs

@@ -0,0 +1,37 @@
+// 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.
+
+// Regression test for an NLL-related ICE (#52992) -- computing
+// implied bounds was causing outlives relations that were not
+// properly handled.
+//
+// compile-pass
+
+#![feature(nll)]
+
+fn main() {}
+
+fn fail<'a>() -> Struct<'a, Generic<()>> {
+    Struct(&Generic(()))
+}
+
+struct Struct<'a, T>(&'a T) where
+    T: Trait + 'a,
+    T::AT: 'a; // only fails with this bound
+
+struct Generic<T>(T);
+
+trait Trait {
+    type AT;
+}
+
+impl<T> Trait for Generic<T> {
+    type AT = T; // only fails with a generic AT
+}

src/test/ui/issue-53568.rs

@@ -0,0 +1,61 @@
+// 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.
+
+// Regression test for an NLL-related ICE (#53568) -- we failed to
+// resolve inference variables in "custom type-ops".
+//
+// compile-pass
+
+#![feature(nll)]
+#![allow(dead_code)]
+
+trait Future {
+    type Item;
+}
+
+impl<F, T> Future for F
+where F: Fn() -> T
+{
+    type Item = T;
+}
+
+trait Connect {}
+
+struct Connector<H> {
+    handler: H,
+}
+
+impl<H, T> Connect for Connector<H>
+where
+    T: 'static,
+    H: Future<Item = T>
+{
+}
+
+struct Client<C> {
+    connector: C,
+}
+
+fn build<C>(_connector: C) -> Client<C> {
+    unimplemented!()
+}
+
+fn client<H>(handler: H) -> Client<impl Connect>
+where H: Fn() + Copy
+{
+    let connector = Connector {
+        handler,
+    };
+    let client = build(connector);
+    client
+}
+
+fn main() { }
+