Rollup merge of #5663 - matthiaskrgr:crash_test_3969, r=Manishearth

add testcase that no longer ICEs

Fixes #3969

changelog: none

tests/ui/crashes/ice-3969.rs

@@ -0,0 +1,51 @@
+// https://github.com/rust-lang/rust-clippy/issues/3969
+// used to crash: error: internal compiler error:
+// src/librustc_traits/normalize_erasing_regions.rs:43: could not fully normalize `<i32 as
+// std::iter::Iterator>::Item test from rustc ./ui/trivial-bounds/trivial-bounds-inconsistent.rs
+
+// Check that tautalogically false bounds are accepted, and are used
+// in type inference.
+#![feature(trivial_bounds)]
+#![allow(unused)]
+
+trait A {}
+
+impl A for i32 {}
+
+struct Dst<X: ?Sized> {
+    x: X,
+}
+
+struct TwoStrs(str, str)
+where
+    str: Sized;
+
+fn unsized_local()
+where
+    for<'a> Dst<A + 'a>: Sized,
+{
+    let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
+}
+
+fn return_str() -> str
+where
+    str: Sized,
+{
+    *"Sized".to_string().into_boxed_str()
+}
+
+fn use_op(s: String) -> String
+where
+    String: ::std::ops::Neg<Output = String>,
+{
+    -s
+}
+
+fn use_for()
+where
+    i32: Iterator,
+{
+    for _ in 2i32 {}
+}
+
+fn main() {}

tests/ui/crashes/ice-3969.stderr

@@ -0,0 +1,22 @@
+error: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/ice-3969.rs:25:17
+   |
+LL |     for<'a> Dst<A + 'a>: Sized,
+   |                 ^^^^^^ help: use `dyn`: `dyn A + 'a`
+   |
+   = note: `-D bare-trait-objects` implied by `-D warnings`
+
+error: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/ice-3969.rs:27:16
+   |
+LL |     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
+   |                ^ help: use `dyn`: `dyn A`
+
+error: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/ice-3969.rs:27:57
+   |
+LL |     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
+   |                                                         ^ help: use `dyn`: `dyn A`
+
+error: aborting due to 3 previous errors
+