[NFC] Inherit from Visitor in OverriddenVisitor (#5182)

Doing so shortens the code by removing duplicate logic.

Also this will avoid a compile error in a future PR, as by inheriting from
Visitor we include functions like visitFunction which were otherwise
missing from OverriddenVisitor. We could duplicate those like we
duplicated the expression logic, but just removing all the duplication
seems best.

I manually verified OverriddenVisitor still provides the same error messages
as before.

1 files changed, 1 insertions, 17 deletions

diff --git a/src/wasm-traversal.h b/src/wasm-traversal.h
index 1f3cb9ca4..b70c17154 100644
--- a/src/wasm-traversal.h
+++ b/src/wasm-traversal.h
@@ -74,7 +74,7 @@ template<typename SubType, typename ReturnType = void> struct Visitor {
 // A visitor which must be overridden for each visitor that is reached.
 
 template<typename SubType, typename ReturnType = void>
-struct OverriddenVisitor {
+struct OverriddenVisitor : public Visitor<SubType, ReturnType> {
 // Expression visitors, which must be overridden
 #define DELEGATE(CLASS_TO_VISIT)                                               \
   ReturnType visit##CLASS_TO_VISIT(CLASS_TO_VISIT* curr) {                     \
@@ -86,22 +86,6 @@ struct OverriddenVisitor {
   }
 
 #include "wasm-delegations.def"
-
-  ReturnType visit(Expression* curr) {
-    assert(curr);
-
-    switch (curr->_id) {
-#define DELEGATE(CLASS_TO_VISIT)                                               \
-  case Expression::Id::CLASS_TO_VISIT##Id:                                     \
-    return static_cast<SubType*>(this)->visit##CLASS_TO_VISIT(                 \
-      static_cast<CLASS_TO_VISIT*>(curr))
-
-#include "wasm-delegations.def"
-
-      default:
-        WASM_UNREACHABLE("unexpected expression type");
-    }
-  }
 };
 
 // Visit with a single unified visitor, called on every node, instead of