OptimizeInstructions: Fix merging of exact cast + ref.as_non_null (#7646)

We must not forget exactness there.

Author: kripken

src/passes/OptimizeInstructions.cpp

@@ -1759,7 +1759,7 @@ struct OptimizeInstructions
           }
         }
         if (canOptimize) {
-          cast->type = Type(cast->type.getHeapType(), NonNullable);
+          cast->type = cast->type.with(NonNullable);
         }
       }
     }
@@ -2583,7 +2583,7 @@ struct OptimizeInstructions
       // The cast cannot be non-nullable, or we would have handled this right
       // above by just removing the ref.as, since it would not be needed.
       assert(!cast->type.isNonNullable());
-      cast->type = Type(cast->type.getHeapType(), NonNullable);
+      cast->type = cast->type.with(NonNullable);
       replaceCurrent(cast);
     }
   }

test/lit/passes/optimize-instructions-exact.wast

@@ -6,7 +6,7 @@
  ;; CHECK:      (type $foo (sub (struct)))
  (type $foo (sub (struct)))
 
- ;; CHECK:      (func $ref-cast-exact-fallthrough (type $1) (param $exact (ref (exact $foo))) (result (ref $foo))
+ ;; CHECK:      (func $ref-cast-exact-fallthrough (type $2) (param $exact (ref (exact $foo))) (result (ref $foo))
  ;; CHECK-NEXT:  (local $inexact (ref $foo))
  ;; CHECK-NEXT:  (local $2 (ref (exact $foo)))
  ;; CHECK-NEXT:  (drop
@@ -29,7 +29,7 @@
   )
  )
 
- ;; CHECK:      (func $prefer-exactness (type $2) (param $exact-null (ref null (exact $foo))) (result (ref $foo))
+ ;; CHECK:      (func $prefer-exactness (type $3) (param $exact-null (ref null (exact $foo))) (result (ref $foo))
  ;; CHECK-NEXT:  (local $inexact-nn (ref $foo))
  ;; CHECK-NEXT:  (local $inexact-null (ref null $foo))
  ;; CHECK-NEXT:  (local $3 (ref null (exact $foo)))
@@ -64,7 +64,7 @@
   )
  )
 
- ;; CHECK:      (func $combine-non-null (type $3) (param $foo (ref null $foo)) (result (ref (exact $foo)))
+ ;; CHECK:      (func $combine-non-null (type $1) (param $foo (ref null $foo)) (result (ref (exact $foo)))
  ;; CHECK-NEXT:  (ref.cast (ref (exact $foo))
  ;; CHECK-NEXT:   (local.get $foo)
  ;; CHECK-NEXT:  )
@@ -78,4 +78,18 @@
    )
   )
  )
+
+ ;; CHECK:      (func $combine-non-null-reverse (type $1) (param $foo (ref null $foo)) (result (ref (exact $foo)))
+ ;; CHECK-NEXT:  (ref.cast (ref (exact $foo))
+ ;; CHECK-NEXT:   (local.get $foo)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $combine-non-null-reverse (param $foo (ref null $foo)) (result (ref (exact $foo)))
+  ;; As above, but flipped.
+  (ref.as_non_null
+   (ref.cast (ref null (exact $foo))
+    (local.get $foo)
+   )
+  )
+ )
 )