Fix stringview subtyping (#6440)

The stringview types (`stringview_wtf8`, `stringview_wtf16`, and
`stringview_iter`) are not subtypes of `any` even though they are supertypes of
`none`. This breaks the type system invariant that types share a bottom type iff
they share a top type, but we can work around that.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/tools/fuzzing/heap-types.cpp b/src/tools/fuzzing/heap-types.cpp
index 13ad01474..5c948e44d 100644
--- a/src/tools/fuzzing/heap-types.cpp
+++ b/src/tools/fuzzing/heap-types.cpp
@@ -454,12 +454,19 @@ struct HeapTypeGeneratorImpl {
         candidates.push_back(HeapType::any);
         break;
       case HeapType::string:
+        candidates.push_back(HeapType::any);
+        break;
       case HeapType::stringview_wtf8:
       case HeapType::stringview_wtf16:
       case HeapType::stringview_iter:
-        candidates.push_back(HeapType::any);
         break;
       case HeapType::none:
+        if (rand.oneIn(10)) {
+          candidates.push_back(HeapType::stringview_wtf8);
+          candidates.push_back(HeapType::stringview_wtf16);
+          candidates.push_back(HeapType::stringview_iter);
+          break;
+        }
         return pickSubAny();
       case HeapType::nofunc:
         return pickSubFunc();