Move /src/test to /tests

tests/ui/lint/dead-code/impl-trait.rs

@@ -0,0 +1,18 @@
+#![deny(dead_code)]
+
+trait Trait {
+    type Type;
+}
+
+impl Trait for () {
+    type Type = ();
+}
+
+type Used = ();
+type Unused = (); //~ ERROR type alias `Unused` is never used
+
+fn foo() -> impl Trait<Type = Used> {}
+
+fn main() {
+    foo();
+}