test: Add test for #1763

Author: brson

src/test/run-fail/issue-1763.rs

@@ -0,0 +1,14 @@
+// Issue #1763 - infer types correctly
+// error-pattern:explicit failure
+
+type actor<T> = {
+    unused: bool
+};
+
+fn act2<T>() -> actor<T> {
+    fail;
+}
+
+fn main() {
+    let a: actor<int> = act2();
+}