[NominalFuzzing] Fix getHeapTypeCounts() on unreachable casts (#4609)

The cast instruction may be unreachable but the intended type for the cast
still needs to be collected. Otherwise we end up with problems both during
optimizations that look at heap types and in printing (which will use the heap
type in code but not declare it).

Diff without whitespace is much smaller: this just moves code around so
that we can use a template to avoid code duplication. The actual change
is just to scan ->intendedType unconditionally, and not ignore it if the
cast is unreachable.

1 files changed, 24 insertions, 0 deletions

diff --git a/test/lit/passes/signature-pruning.wast b/test/lit/passes/signature-pruning.wast
index 3c27ee874..3c4500eaf 100644
--- a/test/lit/passes/signature-pruning.wast
+++ b/test/lit/passes/signature-pruning.wast
@@ -786,3 +786,27 @@
     (call $bar (ref.null func))
   )
 )
+
+(module
+  ;; CHECK:      (type $none_=>_none (func_subtype func))
+
+  ;; CHECK:      (type $A (struct_subtype  data))
+  (type $A (struct_subtype data))
+  ;; CHECK:      (func $0 (type $none_=>_none)
+  ;; CHECK-NEXT:  (local $0 f32)
+  ;; CHECK-NEXT:  (ref.cast_static $A
+  ;; CHECK-NEXT:   (unreachable)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $0 (param $0 f32)
+    ;; $A is only used in an unreachable cast. We should not error when
+    ;; removing the param from this function, during which we collect heap
+    ;; types, and must find this one even though the cast is unreachable, as
+    ;; we do need to handle it in the optimization as well as print it (note how
+    ;; type $A is declared in the output here - it would be a bug if it were
+    ;; not, which this is a regression test for).
+    (ref.cast_static $A
+      (unreachable)
+    )
+  )
+)