handle soon-to-be-invalid types

Author: tlively

src/passes/Unsubtyping.cpp

@@ -849,7 +849,11 @@ struct Unsubtyping : Pass {
     // Add all the edges. Don't worry about duplicating existing edges because
     // checking whether they're necessary now would be about as expensive as
     // discarding them later.
-    noteSubtype(*sub, *super);
+    // TODO: We will be able to assume this once we update the descriptor
+    // validation rules.
+    if (HeapType::isSubType(*sub, *super)) {
+      noteSubtype(*sub, *super);
+    }
     noteSubtype(*subDesc, *superDesc);
     noteDescriptor(*super, *superDesc);
     noteDescriptor(*sub, *subDesc);

test/lit/passes/unsubtyping-desc.wast

@@ -1086,3 +1086,22 @@
     )
   )
 )
+
+;; This will be invalid soon, but in the meantime we should not be confused when
+;; the types described by two related descriptors are unrelated.
+(module
+  (rec
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $A (descriptor $super (struct)))
+    (type $A (descriptor $super (struct)))
+    ;; CHECK:       (type $B (descriptor $sub (struct)))
+    (type $B (descriptor $sub (struct)))
+    ;; CHECK:       (type $super (sub (describes $A (struct))))
+    (type $super (sub (describes $A (struct))))
+    ;; CHECK:       (type $sub (sub $super (describes $B (struct))))
+    (type $sub (sub $super (describes $B (struct))))
+  )
+  ;; CHECK:      (global $public (ref null $B) (ref.null none))
+  (global $public (export "public") (ref null $B) (ref.null none))
+)
+;; CHECK:      (export "public" (global $public))