Add regression test for issue #17283

Author: bkoropoff

src/test/compile-fail/issue-17283.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 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.
+
+// Test that the parser does not attempt to parse struct literals
+// within assignments in if expressions.
+
+struct Foo {
+    foo: uint
+}
+
+fn main() {
+    let x = 1u;
+    let y: Foo;
+
+    // `x { ... }` should not be interpreted as a struct literal here
+    if x = x {
+        //~^ ERROR mismatched types: expected `bool`, found `()` (expected bool, found ())
+        println!("{}", x);
+    }
+    // Explicit parentheses on the left should match behavior of above
+    if (x = x) {
+        //~^ ERROR mismatched types: expected `bool`, found `()` (expected bool, found ())
+        println!("{}", x);
+    }
+    // The struct literal interpretation is fine with explicit parentheses on the right
+    if y = (Foo { foo: x }) {
+        //~^ ERROR mismatched types: expected `bool`, found `()` (expected bool, found ())
+        println!("{}", x);
+    }
+}