Test that fn preconditions get typechecked

src/test/compile-fail/nonsense-constraints.rs

@@ -0,0 +1,18 @@
+// Tests that the typechecker checks constraints
+// error-pattern:mismatched types: expected uint but found u8
+use std;
+import std::uint;
+
+fn enum_chars(start:u8, end:u8) : uint::le(start, end) -> [char] {
+    let i = start;
+    let r = [];
+    while (i <= end) {
+        r += [i as char];
+        i += (1u as u8);
+    }
+    ret r;
+}
+
+fn main() {
+    log (enum_chars('a' as u8, 'z' as u8));
+}