[regexp] break recursion in mutually recursive capture/back references.

src/ast/ast.h

Index: src/ast/ast.h
diff --git a/src/ast/ast.h b/src/ast/ast.h
index b4f2992e047215ac95d2c61b96a98d64afbfb5a1..eae0bda0e10adfb472385b903390a500669bf311 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -3180,24 +3180,21 @@ class RegExpLookaround final : public RegExpTree {
 class RegExpBackReference final : public RegExpTree {
  public:
   explicit RegExpBackReference(RegExpCapture* capture)
-      : capture_(capture) { }
+      : capture_(capture), max_match_(kUninitialized) {}
   void* Accept(RegExpVisitor* visitor, void* data) override;
   RegExpNode* ToNode(RegExpCompiler* compiler, RegExpNode* on_success) override;
   RegExpBackReference* AsBackReference() override;
   bool IsBackReference() override;
   int min_match() override { return 0; }
-  // The capture may not be completely parsed yet, if the reference occurs
-  // before the capture. In the ordinary case, nothing has been captured yet,
-  // so the back reference must have the length 0. If the back reference is
-  // inside a lookbehind, effectively making it a forward reference, we return
-  // 0 since lookbehinds have a length of 0.
-  int max_match() override {
-    return capture_->body() ? capture_->max_match() : 0;
-  }
+  int max_match() override;
   int index() { return capture_->index(); }
   RegExpCapture* capture() { return capture_; }
  private:
+  static const int kUninitialized = -1;
+  static const int kRecursionMarker = -2;
+
   RegExpCapture* capture_;
+  int max_match_;
 };