Add fatal overflow test

src/test/ui/typeck/hang-in-overflow.rs

@@ -0,0 +1,18 @@
+// normalize-stderr-test "the requirement `.*`" -> "the requirement `...`"
+// normalize-stderr-test "required for `.*` to implement `.*`" -> "required for `...` to implement `...`"
+
+// Currently this fatally aborts instead of hanging.
+// Make sure at least that this doesn't turn into a hang.
+
+fn f() {
+    foo::<_>();
+    //~^ ERROR overflow evaluating the requirement
+}
+
+fn foo<B>()
+where
+    Vec<[[[B; 1]; 1]; 1]>: PartialEq<B>,
+{
+}
+
+fn main() {}

src/test/ui/typeck/hang-in-overflow.stderr

@@ -0,0 +1,22 @@
+error[E0275]: overflow evaluating the requirement `...`
+  --> $DIR/hang-in-overflow.rs:8:5
+   |
+LL |     foo::<_>();
+   |     ^^^^^^^^
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`hang_in_overflow`)
+   = note: required for `...` to implement `...`
+   = note: 127 redundant requirements hidden
+   = note: required for `...` to implement `...`
+note: required by a bound in `foo`
+  --> $DIR/hang-in-overflow.rs:14:28
+   |
+LL | fn foo<B>()
+   |    --- required by a bound in this
+LL | where
+LL |     Vec<[[[B; 1]; 1]; 1]>: PartialEq<B>,
+   |                            ^^^^^^^^^^^^ required by this bound in `foo`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0275`.