Be a bit more constrained in our early check

Do not require the target type to be fully known,
either. This allows code like `let x: *const () = 0 as _` to work
(see regression test).

1 files changed, 17 insertions, 0 deletions

diff --git a/src/test/run-pass/cast-to-infer-ty.rs b/src/test/run-pass/cast-to-infer-ty.rs
new file mode 100644
index 00000000000..2aa0d9c62fb
--- /dev/null
+++ b/src/test/run-pass/cast-to-infer-ty.rs
@@ -0,0 +1,17 @@
+// Copyright 2012 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.
+
+// Check that we allow a cast to `_` so long as the target type can be
+// inferred elsewhere.
+
+pub fn main() {
+    let i: *const i32 = 0 as _;
+    assert!(i.is_null());
+}