Added compile-fail tests

src/test/compile-fail/lint-type-limits.rs

@@ -0,0 +1,25 @@
+// compile-flags: -D type-limits
+fn main() { }
+
+fn foo() {
+    let mut i = 100u;
+    while i >= 0 { //~ ERROR comparison is useless due to type limits
+        i -= 1;
+    }
+}
+
+fn bar() -> i8 {
+    return 123;
+}
+
+fn baz() -> bool {
+    128 > bar() //~ ERROR comparison is useless due to type limits
+}
+
+fn qux() {
+    let mut i = 1i8;
+    while 200 != i { //~ ERROR comparison is useless due to type limits
+        i += 1;
+    }
+}
+