Allow auto(x) to appear in a parenthesis
expression.

The pattern (auto( can appear as part of a declarator,
so the parser is modified to avoid the ambiguity,
in a way consistent with the proposed resolution to CWG1223.

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D149276

(This relands 59337263ab45d7657e and makes sure comma operator
 diagnostics are suppressed in a SFINAE context.)

While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938

This reverts commit cbbf2e8c8ae7730ff0121f4868de4a7d188feb65.
It seems causing diagnoses in SFINAE context.

While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938

This reverts commit 63e0d038fc20c894a3d541effa1bc2b1fdea37b9.

It causes test failures:

http://lab.llvm.org:8011/#/builders/119/builds/5612
https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8835548361443044001/+/u/clang/test/stdout

While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938

This reverts commit e48f444751cf781c42934b242b81f549da77bad0.

thakis noticed false reports, so reverting this change for now until
those can be sorted out.

See https://reviews.llvm.org/D71714

Patch by Ilya Mirsky!

Fixes: http://llvm.org/PR44343

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D71714

The syntax rules for ptr-operator allow attributes after *, &,
&&, therefore we should be able to parse the following:

void fn() {
    void (*[[attr]] x)() = &fn;
    void (&[[attr]] y)() = fn;
    void (&&[[attr]] z)() = fn;
}
However the current logic in TryParsePtrOperatorSeq does not consider
the presence of attributes leading to unexpected parsing errors.

Moreover we should also consider _Atomic a possible qualifier that can
appear after the sequence of attribute specifiers.