Move /src/test to /tests

tests/ui/for-loop-while/for-loop-has-unit-body.rs

@@ -0,0 +1,13 @@
+// run-pass
+fn main() {
+    // Check that the tail statement in the body unifies with something
+    for _ in 0..3 {
+        // `()` is fine to zero-initialize as it is zero sized and inhabited.
+        unsafe { std::mem::zeroed() }
+    }
+
+    // Check that the tail statement in the body can be unit
+    for _ in 0..3 {
+        ()
+    }
+}