[c++20] Implement P1009R2: allow omitting the array bound in an array

new expression.

This was voted into C++20 as a defect report resolution, so we
retroactively apply it to all prior language modes (though it can never
actually be used before C++11 mode).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@360006 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 5 deletions

diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 87a6b4df8f..fbafb43688 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -2929,12 +2929,12 @@ Parser::ParseCXXNewExpression(bool UseGlobal, SourceLocation Start) {
 /// passed to ParseDeclaratorInternal.
 ///
 ///        direct-new-declarator:
-///                   '[' expression ']'
+///                   '[' expression[opt] ']'
 ///                   direct-new-declarator '[' constant-expression ']'
 ///
 void Parser::ParseDirectNewDeclarator(Declarator &D) {
   // Parse the array dimensions.
-  bool first = true;
+  bool First = true;
   while (Tok.is(tok::l_square)) {
     // An array-size expression can't start with a lambda.
     if (CheckProhibitedCXX11Attribute())
@@ -2943,14 +2943,15 @@ void Parser::ParseDirectNewDeclarator(Declarator &D) {
     BalancedDelimiterTracker T(*this, tok::l_square);
     T.consumeOpen();
 
-    ExprResult Size(first ? ParseExpression()
-                                : ParseConstantExpression());
+    ExprResult Size =
+        First ? (Tok.is(tok::r_square) ? ExprResult() : ParseExpression())
+              : ParseConstantExpression();
     if (Size.isInvalid()) {
       // Recover
       SkipUntil(tok::r_square, StopAtSemi);
       return;
     }
-    first = false;
+    First = false;
 
     T.consumeClose();