r295224 - PR24440: Do not silently discard a fold-expression appearing as the operand of a cast-expression.

[Hans Wennborg via cfe-commits]

Merged in r295375.

Thanks,
Hans

On Wed, Feb 15, 2017 at 12:14 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> Hans, this would be a good candidate for Clang 4. The bug in question is not
> a regression, but it is an accepts-invalid / wrong-code bug.
>
> On 15 February 2017 at 11:57, Richard Smith via cfe-commits
> <cfe-commits at lists.llvm.org> wrote:
>>
>> Author: rsmith
>> Date: Wed Feb 15 13:57:10 2017
>> New Revision: 295224
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=295224&view=rev
>> Log:
>> PR24440: Do not silently discard a fold-expression appearing as the
>> operand of a cast-expression.
>>
>> Modified:
>>     cfe/trunk/lib/Parse/ParseExpr.cpp
>>     cfe/trunk/lib/Sema/SemaTemplateVariadic.cpp
>>     cfe/trunk/test/Parser/cxx1z-fold-expressions.cpp
>>
>> Modified: cfe/trunk/lib/Parse/ParseExpr.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseExpr.cpp?rev=295224&r1=295223&r2=295224&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Parse/ParseExpr.cpp (original)
>> +++ cfe/trunk/lib/Parse/ParseExpr.cpp Wed Feb 15 13:57:10 2017
>> @@ -2409,7 +2409,7 @@ Parser::ParseParenExpression(ParenParseO
>>        // fold-expressions, we'll need to allow multiple ArgExprs here.
>>        if (ArgExprs.size() == 1 && isFoldOperator(Tok.getKind()) &&
>>            NextToken().is(tok::ellipsis))
>> -        return ParseFoldExpression(Result, T);
>> +        return ParseFoldExpression(ArgExprs[0], T);
>>
>>        ExprType = SimpleExpr;
>>        Result = Actions.ActOnParenListExpr(OpenLoc, Tok.getLocation(),
>>
>> Modified: cfe/trunk/lib/Sema/SemaTemplateVariadic.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplateVariadic.cpp?rev=295224&r1=295223&r2=295224&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/Sema/SemaTemplateVariadic.cpp (original)
>> +++ cfe/trunk/lib/Sema/SemaTemplateVariadic.cpp Wed Feb 15 13:57:10 2017
>> @@ -1015,6 +1015,11 @@ ExprResult Sema::ActOnCXXFoldExpr(Source
>>    CheckFoldOperand(*this, LHS);
>>    CheckFoldOperand(*this, RHS);
>>
>> +  auto DiscardOperands = [&] {
>> +    CorrectDelayedTyposInExpr(LHS);
>> +    CorrectDelayedTyposInExpr(RHS);
>> +  };
>> +
>>    // [expr.prim.fold]p3:
>>    //   In a binary fold, op1 and op2 shall be the same fold-operator, and
>>    //   either e1 shall contain an unexpanded parameter pack or e2 shall
>> contain
>> @@ -1022,6 +1027,7 @@ ExprResult Sema::ActOnCXXFoldExpr(Source
>>    if (LHS && RHS &&
>>        LHS->containsUnexpandedParameterPack() ==
>>            RHS->containsUnexpandedParameterPack()) {
>> +    DiscardOperands();
>>      return Diag(EllipsisLoc,
>>                  LHS->containsUnexpandedParameterPack()
>>                      ? diag::err_fold_expression_packs_both_sides
>> @@ -1035,6 +1041,7 @@ ExprResult Sema::ActOnCXXFoldExpr(Source
>>    if (!LHS || !RHS) {
>>      Expr *Pack = LHS ? LHS : RHS;
>>      assert(Pack && "fold expression with neither LHS nor RHS");
>> +    DiscardOperands();
>>      if (!Pack->containsUnexpandedParameterPack())
>>        return Diag(EllipsisLoc,
>> diag::err_pack_expansion_without_parameter_packs)
>>               << Pack->getSourceRange();
>>
>> Modified: cfe/trunk/test/Parser/cxx1z-fold-expressions.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx1z-fold-expressions.cpp?rev=295224&r1=295223&r2=295224&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/Parser/cxx1z-fold-expressions.cpp (original)
>> +++ cfe/trunk/test/Parser/cxx1z-fold-expressions.cpp Wed Feb 15 13:57:10
>> 2017
>> @@ -34,3 +34,12 @@ template<int ...N> int bad9() { return (
>>  template<int ...N> int bad10() { return (3 ? ... : N); } //
>> expected-error +{{}} expected-note {{to match}}
>>  template<int ...N> int bad11() { return (N + ... 0); } // expected-error
>> {{expected a foldable binary operator}} expected-error {{expected
>> expression}}
>>  template<int ...N> int bad12() { return (... N); } // expected-error
>> {{expected expression}}
>> +
>> +template<typename ...T> void as_operand_of_cast(int a, T ...t) {
>> +  return
>> +    (int)(a + ... + undeclared_junk) + // expected-error {{undeclared}}
>> expected-error {{does not contain any unexpanded}}
>> +    (int)(t + ... + undeclared_junk) + // expected-error {{undeclared}}
>> +    (int)(... + undeclared_junk) + // expected-error {{undeclared}}
>> expected-error {{does not contain any unexpanded}}
>> +    (int)(undeclared_junk + ...) + // expected-error {{undeclared}}
>> +    (int)(a + ...); // expected-error {{does not contain any unexpanded}}
>> +}
>>
>>
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