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

[Nicolas Lesser via Phabricator via cfe-commits]

Rakete1111 updated this revision to Diff 157578.
Rakete1111 added a comment.

@rsmith you're right, it should. But it doesn't, because the the fold expression is considered to be a cast expression by ParseParenExpression and which parses any postfix pieces immediately after a cast, but it doesn't do so for fold expression, because they don't (not surprisingly) involve a cast.

I've added a new type of ParenParseOption for fold-expressions for this, which makes the patch way more cleaner :) (I didn't want to reuse SimpleExpr for fold expressions - conflicts with the docs for it)


Repository:
  rC Clang

https://reviews.llvm.org/D49848

Files:
  include/clang/Parse/Parser.h
  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
@@ -779,6 +779,10 @@
       // We have parsed the cast-expression and no postfix-expr pieces are
       // following.
       return Res;
+    case FoldExpr:
+      // We parsed fold-expression only. There might be postfix-expr pieces
+      // afterwards; parse them now.
+      break;
     }
 
     break;
@@ -2514,6 +2518,7 @@
     }
   } else if (Tok.is(tok::ellipsis) &&
              isFoldOperator(NextToken().getKind())) {
+    ExprType = FoldExpr;
     return ParseFoldExpression(ExprResult(), T);
   } else if (isTypeCast) {
     // Parse the expression-list.
@@ -2526,8 +2531,10 @@
       // 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))
+          NextToken().is(tok::ellipsis)) {
+        ExprType = FoldExpr;
         return ParseFoldExpression(ArgExprs[0], T);
+      }
 
       ExprType = SimpleExpr;
       Result = Actions.ActOnParenListExpr(OpenLoc, Tok.getLocation(),
@@ -2544,8 +2551,10 @@
     }
     ExprType = SimpleExpr;
 
-    if (isFoldOperator(Tok.getKind()) && NextToken().is(tok::ellipsis))
+    if (isFoldOperator(Tok.getKind()) && NextToken().is(tok::ellipsis)) {
+      ExprType = FoldExpr;
       return ParseFoldExpression(Result, T);
+    }
 
     // Don't build a paren expression unless we actually match a ')'.
     if (!Result.isInvalid() && Tok.is(tok::r_paren))
Index: include/clang/Parse/Parser.h
===================================================================
--- include/clang/Parse/Parser.h
+++ include/clang/Parse/Parser.h
@@ -1654,7 +1654,8 @@
     SimpleExpr,      // Only parse '(' expression ')'
     CompoundStmt,    // Also allow '(' compound-statement ')'
     CompoundLiteral, // Also allow '(' type-name ')' '{' ... '}'
-    CastExpr         // Also allow '(' type-name ')' <anything>
+    CastExpr,        // Also allow '(' type-name ')' <anything>
+    FoldExpr         // Also allow fold-expression <anything>
   };
   ExprResult ParseParenExpression(ParenParseOption &ExprType,
                                         bool stopIfCastExpr,


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