Create `ParentIndexIterator` to reduce iterator boilerplate (#4469)

Add a utility class for defining all the common operations like pre- and post-
increment and decrement, addition and subtraction, and assigning addition and
subtraction for iterators that are comprised of a parent object and an index
into that parent object. Use the new utility to reduce the boilerplate in
wasm-type.h. Add a new test of the iterator behavior.

1 files changed, 4 insertions, 13 deletions

diff --git a/src/wasm/wasm-type.cpp b/src/wasm/wasm-type.cpp
index af382da23..7801cc289 100644
--- a/src/wasm/wasm-type.cpp
+++ b/src/wasm/wasm-type.cpp
@@ -1082,13 +1082,13 @@ Type Type::getLeastUpperBound(Type a, Type b) {
   return TypeBounder().getLeastUpperBound(a, b);
 }
 
-Type::Iterator Type::end() const {
+size_t Type::size() const {
   if (isTuple()) {
-    return Iterator(this, getTypeInfo(*this)->tuple.types.size());
+    return getTypeInfo(*this)->tuple.types.size();
   } else {
     // TODO: unreachable is special and expands to {unreachable} currently.
     // see also: https://github.com/WebAssembly/binaryen/issues/3062
-    return Iterator(this, size_t(id != Type::none));
+    return size_t(id != Type::none);
   }
 }
 
@@ -1096,21 +1096,12 @@ const Type& Type::Iterator::operator*() const {
   if (parent->isTuple()) {
     return getTypeInfo(*parent)->tuple.types[index];
   } else {
-    // TODO: see comment in Type::end()
+    // TODO: see comment in Type::size()
     assert(index == 0 && parent->id != Type::none && "Index out of bounds");
     return *parent;
   }
 }
 
-const Type& Type::operator[](size_t index) const {
-  if (isTuple()) {
-    return getTypeInfo(*this)->tuple.types[index];
-  } else {
-    assert(index == 0 && "Index out of bounds");
-    return *begin();
-  }
-}
-
 HeapType::HeapType(Signature sig) {
   assert(!isTemp(sig.params) && "Leaking temporary type!");
   assert(!isTemp(sig.results) && "Leaking temporary type!");