Basic initial inheritance

tests/compiler/class-extends.ts

@@ -0,0 +1,14 @@
+class A {
+  a: i32 = 0;
+}
+
+class B extends A {
+  b: i16 = 1;
+}
+
+export function test(b: B): void {
+  b.a;
+  b.b;
+  b.a = 2;
+  b.b = 3;
+}