Restore the `extern` heap type (#4898)

The GC proposal has split `any` and `extern` back into two separate types, so
reintroduce `HeapType::ext` to represent `extern`. Before it was originally
removed in #4633, externref was a subtype of anyref, but now it is not. Now that
we have separate heaptype type hierarchies, make `HeapType::getLeastUpperBound`
fallible as well.

1 files changed, 7 insertions, 7 deletions

diff --git a/test/lit/passes/optimize-instructions-gc.wast b/test/lit/passes/optimize-instructions-gc.wast
index f6a1b5d09..7a0eea294 100644
--- a/test/lit/passes/optimize-instructions-gc.wast
+++ b/test/lit/passes/optimize-instructions-gc.wast
@@ -47,37 +47,37 @@
   ;; These functions test if an `if` with subtyped arms is correctly folded
   ;; 1. if its `ifTrue` and `ifFalse` arms are identical (can fold)
   ;; CHECK:      (func $if-arms-subtype-fold (result anyref)
-  ;; CHECK-NEXT:  (ref.null any)
+  ;; CHECK-NEXT:  (ref.null eq)
   ;; CHECK-NEXT: )
   ;; NOMNL:      (func $if-arms-subtype-fold (type $none_=>_anyref) (result anyref)
-  ;; NOMNL-NEXT:  (ref.null any)
+  ;; NOMNL-NEXT:  (ref.null eq)
   ;; NOMNL-NEXT: )
   (func $if-arms-subtype-fold (result anyref)
     (if (result anyref)
       (i32.const 0)
-      (ref.null extern)
-      (ref.null extern)
+      (ref.null eq)
+      (ref.null eq)
     )
   )
   ;; 2. if its `ifTrue` and `ifFalse` arms are not identical (cannot fold)
   ;; CHECK:      (func $if-arms-subtype-nofold (result anyref)
   ;; CHECK-NEXT:  (if (result anyref)
   ;; CHECK-NEXT:   (i32.const 0)
-  ;; CHECK-NEXT:   (ref.null any)
+  ;; CHECK-NEXT:   (ref.null eq)
   ;; CHECK-NEXT:   (ref.null func)
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT: )
   ;; NOMNL:      (func $if-arms-subtype-nofold (type $none_=>_anyref) (result anyref)
   ;; NOMNL-NEXT:  (if (result anyref)
   ;; NOMNL-NEXT:   (i32.const 0)
-  ;; NOMNL-NEXT:   (ref.null any)
+  ;; NOMNL-NEXT:   (ref.null eq)
   ;; NOMNL-NEXT:   (ref.null func)
   ;; NOMNL-NEXT:  )
   ;; NOMNL-NEXT: )
   (func $if-arms-subtype-nofold (result anyref)
     (if (result anyref)
       (i32.const 0)
-      (ref.null extern)
+      (ref.null eq)
       (ref.null func)
     )
   )