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.

4 files changed, 44 insertions, 40 deletions

diff --git a/test/lit/passes/flatten_all-features.wast b/test/lit/passes/flatten_all-features.wast
index b563159c6..6a9ffc16a 100644
--- a/test/lit/passes/flatten_all-features.wast
+++ b/test/lit/passes/flatten_all-features.wast
@@ -3416,55 +3416,59 @@
   ;; value type, we need the value to be set into two locals: one with the outer
   ;; block's type, and one with its value type.
   ;; CHECK:      (func $subtype (result anyref)
-  ;; CHECK-NEXT:  (local $0 anyref)
+  ;; CHECK-NEXT:  (local $0 eqref)
   ;; CHECK-NEXT:  (local $1 anyref)
-  ;; CHECK-NEXT:  (local $2 anyref)
-  ;; CHECK-NEXT:  (local $3 anyref)
-  ;; CHECK-NEXT:  (local $4 anyref)
-  ;; CHECK-NEXT:  (local $5 anyref)
-  ;; CHECK-NEXT:  (local $6 anyref)
+  ;; CHECK-NEXT:  (local $2 eqref)
+  ;; CHECK-NEXT:  (local $3 eqref)
+  ;; CHECK-NEXT:  (local $4 eqref)
+  ;; CHECK-NEXT:  (local $5 eqref)
+  ;; CHECK-NEXT:  (local $6 eqref)
+  ;; CHECK-NEXT:  (local $7 anyref)
   ;; CHECK-NEXT:  (block $label0
   ;; CHECK-NEXT:   (block $block
   ;; CHECK-NEXT:    (local.set $1
-  ;; CHECK-NEXT:     (ref.null any)
+  ;; CHECK-NEXT:     (ref.null eq)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (local.set $2
+  ;; CHECK-NEXT:     (ref.null eq)
   ;; CHECK-NEXT:    )
   ;; CHECK-NEXT:    (br_if $label0
   ;; CHECK-NEXT:     (i32.const 0)
   ;; CHECK-NEXT:    )
-  ;; CHECK-NEXT:    (local.set $2
-  ;; CHECK-NEXT:     (local.get $1)
+  ;; CHECK-NEXT:    (local.set $3
+  ;; CHECK-NEXT:     (local.get $2)
   ;; CHECK-NEXT:    )
   ;; CHECK-NEXT:    (local.set $0
-  ;; CHECK-NEXT:     (local.get $2)
+  ;; CHECK-NEXT:     (local.get $3)
   ;; CHECK-NEXT:    )
-  ;; CHECK-NEXT:    (local.set $3
+  ;; CHECK-NEXT:    (local.set $4
   ;; CHECK-NEXT:     (local.get $0)
   ;; CHECK-NEXT:    )
-  ;; CHECK-NEXT:    (local.set $4
-  ;; CHECK-NEXT:     (local.get $3)
+  ;; CHECK-NEXT:    (local.set $5
+  ;; CHECK-NEXT:     (local.get $4)
   ;; CHECK-NEXT:    )
   ;; CHECK-NEXT:   )
-  ;; CHECK-NEXT:   (local.set $5
-  ;; CHECK-NEXT:    (local.get $4)
+  ;; CHECK-NEXT:   (local.set $6
+  ;; CHECK-NEXT:    (local.get $5)
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:   (local.set $1
-  ;; CHECK-NEXT:    (local.get $5)
+  ;; CHECK-NEXT:    (local.get $6)
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
-  ;; CHECK-NEXT:  (local.set $6
+  ;; CHECK-NEXT:  (local.set $7
   ;; CHECK-NEXT:   (local.get $1)
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (return
-  ;; CHECK-NEXT:   (local.get $6)
+  ;; CHECK-NEXT:   (local.get $7)
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT: )
   (func $subtype (result anyref)
-    (local $0 externref)
+    (local $0 eqref)
     (block $label0 (result anyref)
-      (block (result externref)
+      (block (result eqref)
         (local.tee $0
           (br_if $label0
-            (ref.null extern)
+            (ref.null eq)
             (i32.const 0)
           )
         )
diff --git a/test/lit/passes/gufa-refs.wast b/test/lit/passes/gufa-refs.wast
index d8fb51e50..73201a169 100644
--- a/test/lit/passes/gufa-refs.wast
+++ b/test/lit/passes/gufa-refs.wast
@@ -2961,7 +2961,7 @@
 
   ;; CHECK:      (memory $0 10)
 
-  ;; CHECK:      (table $t 0 anyref)
+  ;; CHECK:      (table $t 0 externref)
 
   ;; CHECK:      (tag $e-i32 (param i32))
   (tag $e-i32 (param i32))
@@ -3210,7 +3210,7 @@
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (drop
   ;; CHECK-NEXT:   (table.grow $t
-  ;; CHECK-NEXT:    (ref.null any)
+  ;; CHECK-NEXT:    (ref.null extern)
   ;; CHECK-NEXT:    (i32.const 1)
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
diff --git a/test/lit/passes/instrument-locals_all-features_disable-typed-function-references.wast b/test/lit/passes/instrument-locals_all-features_disable-typed-function-references.wast
index 3c0ded9ee..70ccf3364 100644
--- a/test/lit/passes/instrument-locals_all-features_disable-typed-function-references.wast
+++ b/test/lit/passes/instrument-locals_all-features_disable-typed-function-references.wast
@@ -14,7 +14,7 @@
 
   ;; CHECK:      (type $i32_i32_funcref_=>_funcref (func (param i32 i32 funcref) (result funcref)))
 
-  ;; CHECK:      (type $i32_i32_anyref_=>_anyref (func (param i32 i32 anyref) (result anyref)))
+  ;; CHECK:      (type $i32_i32_externref_=>_externref (func (param i32 i32 externref) (result externref)))
 
   ;; CHECK:      (type $i32_i32_v128_=>_v128 (func (param i32 i32 v128) (result v128)))
 
@@ -40,9 +40,9 @@
 
   ;; CHECK:      (import "env" "set_funcref" (func $set_funcref (param i32 i32 funcref) (result funcref)))
 
-  ;; CHECK:      (import "env" "get_anyref" (func $get_anyref (param i32 i32 anyref) (result anyref)))
+  ;; CHECK:      (import "env" "get_externref" (func $get_externref (param i32 i32 externref) (result externref)))
 
-  ;; CHECK:      (import "env" "set_anyref" (func $set_anyref (param i32 i32 anyref) (result anyref)))
+  ;; CHECK:      (import "env" "set_externref" (func $set_externref (param i32 i32 externref) (result externref)))
 
   ;; CHECK:      (import "env" "get_v128" (func $get_v128 (param i32 i32 v128) (result v128)))
 
@@ -56,7 +56,7 @@
   ;; CHECK-NEXT:  (local $z f32)
   ;; CHECK-NEXT:  (local $w f64)
   ;; CHECK-NEXT:  (local $F funcref)
-  ;; CHECK-NEXT:  (local $X anyref)
+  ;; CHECK-NEXT:  (local $X externref)
   ;; CHECK-NEXT:  (local $S v128)
   ;; CHECK-NEXT:  (drop
   ;; CHECK-NEXT:   (call $get_i32
@@ -90,7 +90,7 @@
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (drop
-  ;; CHECK-NEXT:   (call $get_anyref
+  ;; CHECK-NEXT:   (call $get_externref
   ;; CHECK-NEXT:    (i32.const 4)
   ;; CHECK-NEXT:    (i32.const 5)
   ;; CHECK-NEXT:    (local.get $X)
@@ -128,7 +128,7 @@
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (drop
-  ;; CHECK-NEXT:   (call $get_anyref
+  ;; CHECK-NEXT:   (call $get_externref
   ;; CHECK-NEXT:    (i32.const 9)
   ;; CHECK-NEXT:    (i32.const 5)
   ;; CHECK-NEXT:    (local.get $X)
@@ -162,10 +162,10 @@
   ;; CHECK-NEXT:   (ref.func $test)
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (local.set $X
-  ;; CHECK-NEXT:   (call $set_anyref
+  ;; CHECK-NEXT:   (call $set_externref
   ;; CHECK-NEXT:    (i32.const 14)
   ;; CHECK-NEXT:    (i32.const 5)
-  ;; CHECK-NEXT:    (call $get_anyref
+  ;; CHECK-NEXT:    (call $get_externref
   ;; CHECK-NEXT:     (i32.const 13)
   ;; CHECK-NEXT:     (i32.const 5)
   ;; CHECK-NEXT:     (local.get $X)
@@ -208,10 +208,10 @@
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT:  (local.set $X
-  ;; CHECK-NEXT:   (call $set_anyref
+  ;; CHECK-NEXT:   (call $set_externref
   ;; CHECK-NEXT:    (i32.const 21)
   ;; CHECK-NEXT:    (i32.const 5)
-  ;; CHECK-NEXT:    (call $get_anyref
+  ;; CHECK-NEXT:    (call $get_externref
   ;; CHECK-NEXT:     (i32.const 20)
   ;; CHECK-NEXT:     (i32.const 5)
   ;; CHECK-NEXT:     (local.get $X)
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)
     )
   )