Add spread rewriting

src/ast/ast.h

Index: src/ast/ast.h
diff --git a/src/ast/ast.h b/src/ast/ast.h
index eaacf4b3cfade077490acfa553c92e708ad392b8..5c200c4da6c8e9317c404d8fa2ad183e18bd5aba 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -924,6 +924,11 @@ class ForOfStatement final : public ForEachStatement {
     return assign_each_;
   }
 
+  void set_assign_iterator(Expression* e) { assign_iterator_ = e; }
+  void set_next_result(Expression* e) { next_result_ = e; }
+  void set_result_done(Expression* e) { result_done_ = e; }
+  void set_assign_each(Expression* e) { assign_each_ = e; }
+
   BailoutId ContinueId() const override { return EntryId(); }
   BailoutId StackCheckId() const override { return BackEdgeId(); }
 
@@ -1682,6 +1687,19 @@ class ArrayLiteral final : public MaterializedLiteral {
     return flags;
   }
 
+  // Provide a mechanism for iterating through values to rewrite spreads.
+  ZoneList<Expression*>::iterator FirstSpread() const {
+    return (first_spread_index_ >= 0) ? values_->begin() + first_spread_index_
+                                      : values_->end();
+  }
+  ZoneList<Expression*>::iterator EndValue() const { return values_->end(); }
+
+  // Rewind an array literal omitting everything from the first spread on.
+  void RewindSpreads() {
+    values_->Rewind(first_spread_index_);
+    first_spread_index_ = -1;
+  }
+
   enum Flags {
     kNoFlags = 0,
     kShallowElements = 1,
@@ -3385,8 +3403,9 @@ class AstVisitor BASE_EMBEDDED {
  public:                                              \
   AstNode* Rewrite(AstNode* node) {                   \
     DCHECK_NULL(replacement_);                        \
+    DCHECK_NOT_NULL(node);                            \
     Visit(node);                                      \
-    if (HasStackOverflow()) return nullptr;           \
+    if (HasStackOverflow()) return node;              \
     if (replacement_ == nullptr) return node;         \
     AstNode* result = replacement_;                   \
     replacement_ = nullptr;                           \