[Outlining] Test stringify-walker and fix Ifs (#7800)

Add unit tests checking that stringify-walker unnests control flow and
places delimiters in the expected order. Fix a bug where control flow
structures as if conditions were not traversed properly. Add an
assertion that visited Try expressions do not have delegate clauses
because they are not handled yet.

Author: tlively

src/passes/stringify-walker.h

@@ -241,14 +241,14 @@ template<typename SubType>
 inline void StringifyWalker<SubType>::scan(SubType* self, Expression** currp) {
   Expression* curr = *currp;
   if (Properties::isControlFlowStructure(curr)) {
-    self->controlFlowQueue.push(curr);
     self->pushTask(doVisitExpression, currp);
     // The if-condition is a value child consumed by the if control flow, which
     // makes the if-condition a true sibling rather than part of its contents in
     // the binary format
     for (auto*& child : ValueChildIterator(curr)) {
-      Super::scan(self, &child);
+      scan(self, &child);
     }
+    self->controlFlowQueue.push(curr);
   } else {
     Super::scan(self, currp);
   }
@@ -285,7 +285,7 @@ template<typename SubType> void StringifyWalker<SubType>::dequeueControlFlow() {
     }
     case Expression::Id::TryId: {
       auto* tryy = curr->cast<Try>();
-
+      assert(!tryy->isDelegate() && "TODO: try-delegate");
       addUniqueSymbol(SeparatorReason::makeTryStart(tryy));
       Super::walk(tryy->body);
       for (size_t i = 0; i < tryy->catchBodies.size(); i++) {

src/wasm-builder.h

@@ -788,6 +788,7 @@ class Builder {
     ret->body = body;
     ret->catchTags.set(catchTags);
     ret->catchBodies.set(catchBodies);
+    ret->delegateTarget = delegateTarget;
     ret->finalize(type);
     return ret;
   }