Struct and typedef subtypes inherit dynamic functions.

test/unit/regression/interface_inheritance.c3

@@ -0,0 +1,33 @@
+module inherit_interface;
+import std;
+interface Test
+{
+	fn int x();
+}
+
+struct Foo (Test)
+{
+	int z;
+}
+
+fn int Foo.x(&self) @dynamic
+{
+	return 42;
+}
+
+struct Baz
+{
+	inline Bar b;
+}
+
+struct Bar
+{
+	inline Foo f;
+}
+
+fn void test_inheritance() @test
+{
+	Baz x;
+	Test t = &x;
+	test::eq(t.x(), 42);
+}