1 files changed, 17 insertions, 6 deletions

diff --git a/js/src/irregexp/imported/regexp-ast.cc b/js/src/irregexp/imported/regexp-ast.cc
index 63eeb5c05d..34946bd80c 100644
--- a/js/src/irregexp/imported/regexp-ast.cc
+++ b/js/src/irregexp/imported/regexp-ast.cc
@@ -307,7 +307,7 @@ void* RegExpUnparser::VisitCapture(RegExpCapture* that, void* data) {
 }
 
 void* RegExpUnparser::VisitGroup(RegExpGroup* that, void* data) {
-  os_ << "(?: ";
+  os_ << "(?" << that->flags() << ": ";
   that->body()->Accept(this, data);
   os_ << ")";
   return nullptr;
@@ -325,7 +325,11 @@ void* RegExpUnparser::VisitLookaround(RegExpLookaround* that, void* data) {
 
 void* RegExpUnparser::VisitBackReference(RegExpBackReference* that,
                                          void* data) {
-  os_ << "(<- " << that->index() << ")";
+  os_ << "(<- " << that->captures()->first()->index();
+  for (int i = 1; i < that->captures()->length(); ++i) {
+    os_ << "," << that->captures()->at(i)->index();
+  }
+  os_ << ")";
   return nullptr;
 }
 
@@ -406,10 +410,17 @@ RegExpClassSetExpression::RegExpClassSetExpression(
       may_contain_strings_(may_contain_strings),
       operands_(operands) {
   DCHECK_NOT_NULL(operands);
-  DCHECK_IMPLIES(is_negated_, !may_contain_strings_);
-  max_match_ = 0;
-  for (auto op : *operands) {
-    max_match_ = std::max(max_match_, op->max_match());
+  if (is_negated) {
+    DCHECK(!may_contain_strings_);
+    // We don't know anything about max matches for negated classes.
+    // As there are no strings involved, assume that we can match a unicode
+    // character (2 code points).
+    max_match_ = 2;
+  } else {
+    max_match_ = 0;
+    for (auto op : *operands) {
+      max_match_ = std::max(max_match_, op->max_match());
+    }
   }
 }