[PATCH] D49848: Parse a possible trailing postsfix expression suffix after a fold expression

[Nicolas Lesser via Phabricator via cfe-commits]

Rakete1111 created this revision.
Rakete1111 added a reviewer: rsmith.

This patch allows the parsing of a postfix expression involving a fold expression, which is legal as a fold-expression is a primary-expression.

See also https://llvm.org/pr38282


Repository:
  rC Clang

https://reviews.llvm.org/D49848

Files:
  lib/Parse/ParseExpr.cpp
  test/Parser/cxx1z-fold-expressions.cpp


Index: test/Parser/cxx1z-fold-expressions.cpp
===================================================================
--- test/Parser/cxx1z-fold-expressions.cpp
+++ test/Parser/cxx1z-fold-expressions.cpp
@@ -60,3 +60,21 @@
 }
 
 static_assert(nestedFoldOperator<3, 1>() == 1);
+
+// A fold-expression is a primary-expression.
+template <typename T, typename... Ts>
+constexpr auto castSum(Ts... Args) {
+  return (T)(Args + ...).Value; // expected-error{{member reference base type 'int' is not a structure or union}}
+}
+
+void prim() {
+  castSum<int>(1, 2);
+  // expected-note at -1{{in instantiation of function template specialization}}
+
+  struct Number {
+    int Value;
+    constexpr Number operator+(Number Rhs) const { return {Rhs.Value + Value}; }
+  };
+
+  static_assert(castSum<long>(Number{1}, Number{2}) == 3);
+}
Index: lib/Parse/ParseExpr.cpp
===================================================================
--- lib/Parse/ParseExpr.cpp
+++ lib/Parse/ParseExpr.cpp
@@ -2514,7 +2514,10 @@
     }
   } else if (Tok.is(tok::ellipsis) &&
              isFoldOperator(NextToken().getKind())) {
-    return ParseFoldExpression(ExprResult(), T);
+    Result = ParseFoldExpression(ExprResult(), T);
+    if (!Result.isInvalid())
+      Result = ParsePostfixExpressionSuffix(Result.get());
+    return Result;
   } else if (isTypeCast) {
     // Parse the expression-list.
     InMessageExpressionRAIIObject InMessage(*this, false);
@@ -2526,8 +2529,12 @@
       // FIXME: If we ever support comma expressions as operands to
       // fold-expressions, we'll need to allow multiple ArgExprs here.
       if (ArgExprs.size() == 1 && isFoldOperator(Tok.getKind()) &&
-          NextToken().is(tok::ellipsis))
-        return ParseFoldExpression(ArgExprs[0], T);
+          NextToken().is(tok::ellipsis)) {
+        Result = ParseFoldExpression(ArgExprs[0], T);
+        if (!Result.isInvalid())
+          Result = ParsePostfixExpressionSuffix(Result.get());
+        return Result;
+      }
 
       ExprType = SimpleExpr;
       Result = Actions.ActOnParenListExpr(OpenLoc, Tok.getLocation(),
@@ -2544,8 +2551,12 @@
     }
     ExprType = SimpleExpr;
 
-    if (isFoldOperator(Tok.getKind()) && NextToken().is(tok::ellipsis))
-      return ParseFoldExpression(Result, T);
+    if (isFoldOperator(Tok.getKind()) && NextToken().is(tok::ellipsis)) {
+      Result = ParseFoldExpression(Result, T);
+      if (!Result.isInvalid())
+        Result = ParsePostfixExpressionSuffix(Result.get());
+      return Result;
+    }
 
     // Don't build a paren expression unless we actually match a ')'.
     if (!Result.isInvalid() && Tok.is(tok::r_paren))


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