Add a test and several known bugs

tests/ui/associated-inherent-types/bugs/ice-substitution.rs

@@ -0,0 +1,23 @@
+// known-bug: unknown
+// failure-status: 101
+// normalize-stderr-test "note: .*\n\n" -> ""
+// normalize-stderr-test "thread 'rustc' panicked.*\n" -> ""
+// rustc-env:RUST_BACKTRACE=0
+
+// FIXME: I presume a type variable that couldn't be solved by `resolve_vars_if_possible`
+//        escapes the InferCtxt snapshot.
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+struct Cont<T>(T);
+
+impl<T: Copy> Cont<T> {
+    type Out = Vec<T>;
+}
+
+pub fn weird<T: Copy>(x: T) {
+    let _: Cont<_>::Out = vec![true];
+}
+
+fn main() {}

tests/ui/associated-inherent-types/bugs/ice-substitution.stderr

@@ -0,0 +1,6 @@
+error: the compiler unexpectedly panicked. this is a bug.
+
+query stack during panic:
+#0 [typeck] type-checking `weird`
+#1 [typeck_item_bodies] type-checking all item bodies
+end of query stack

tests/ui/associated-inherent-types/bugs/inference-fail.rs

@@ -0,0 +1,15 @@
+// known-bug: unknown
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+struct S<T>(T);
+
+impl S<()> {
+    type P = i128;
+}
+
+fn main() {
+    // We fail to infer `_ == ()` here.
+    let _: S<_>::P;
+}

tests/ui/associated-inherent-types/bugs/inference-fail.stderr

@@ -0,0 +1,9 @@
+error[E0282]: type annotations needed
+  --> $DIR/inference-fail.rs:14:14
+   |
+LL |     let _: S<_>::P;
+   |              ^ cannot infer type
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.

tests/ui/associated-inherent-types/bugs/lack-of-regionck.rs

@@ -0,0 +1,19 @@
+// known-bug: unknown
+// check-pass
+
+// We currently don't region-check inherent associated type projections at all.
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features, dead_code)]
+
+struct S<T>(T);
+
+impl S<&'static ()> {
+    type T = ();
+}
+
+fn usr<'a>() {
+    let _: S::<&'a ()>::T; // this should *fail* but it doesn't!
+}
+
+fn main() {}

tests/ui/associated-inherent-types/not-found-self-type-differs-shadowing-trait-item.rs

@@ -0,0 +1,31 @@
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+// Check that it's okay to report “[inherent] associated type […] not found” for inherent associated
+// type candidates that are not applicable (due to unsuitable Self type) even if there exists a
+// “shadowed” associated type from a trait with the same name since its use would be ambiguous
+// anyway if the IAT didn't exist.
+// FIXME(inherent_associated_types): Figure out which error would be more helpful here.
+
+// revisions: shadowed uncovered
+
+struct S<T>(T);
+
+trait Tr {
+    type Pr;
+}
+
+impl<T> Tr for S<T> {
+    type Pr = ();
+}
+
+#[cfg(shadowed)]
+impl S<()> {
+    type Pr = i32;
+}
+
+fn main() {
+    let _: S::<bool>::Pr = ();
+    //[shadowed]~^ ERROR associated type `Pr` not found
+    //[uncovered]~^^ ERROR ambiguous associated type
+}

tests/ui/associated-inherent-types/not-found-self-type-differs-shadowing-trait-item.shadowed.stderr

@@ -0,0 +1,15 @@
+error[E0220]: associated type `Pr` not found for `S<bool>` in the current scope
+  --> $DIR/not-found-self-type-differs-shadowing-trait-item.rs:28:23
+   |
+LL | struct S<T>(T);
+   | ----------- associated item `Pr` not found for this struct
+...
+LL |     let _: S::<bool>::Pr = ();
+   |                       ^^ associated item not found in `S<bool>`
+   |
+   = note: the associated type was found for
+           - `S<()>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0220`.

tests/ui/associated-inherent-types/not-found-self-type-differs-shadowing-trait-item.uncovered.stderr

@@ -0,0 +1,9 @@
+error[E0223]: ambiguous associated type
+  --> $DIR/not-found-self-type-differs-shadowing-trait-item.rs:28:12
+   |
+LL |     let _: S::<bool>::Pr = ();
+   |            ^^^^^^^^^^^^^ help: use the fully-qualified path: `<S<bool> as Tr>::Pr`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0223`.