Move /src/test to /tests

tests/ui/tuple/tuple-struct-fields/test.rs

@@ -0,0 +1,9 @@
+mod foo {
+    type T = ();
+    struct S1(pub(in foo) (), pub(T), pub(crate) (), pub(((), T)));
+    struct S2(pub((foo)) ());
+    //~^ ERROR expected one of `)` or `,`, found `(`
+    //~| ERROR cannot find type `foo` in this scope
+}
+
+fn main() {}