[all-commits] [llvm/llvm-project] 1881f6: Remove ^^ as a token in OpenCL (#108224)

[Aaron Ballman via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1881f648e28aa58aa0a4dca1422572f65dafa9a4
      https://github.com/llvm/llvm-project/commit/1881f648e28aa58aa0a4dca1422572f65dafa9a4
  Author: Aaron Ballman <aaron at aaronballman.com>
  Date:   2024-09-16 (Mon, 16 Sep 2024)

  Changed paths:
    M clang-tools-extra/clang-tidy/readability/AvoidUnconditionalPreprocessorIfCheck.cpp
    M clang-tools-extra/pseudo/lib/cxx/cxx.bnf
    M clang/include/clang/Basic/DiagnosticLexKinds.td
    M clang/include/clang/Basic/DiagnosticParseKinds.td
    M clang/include/clang/Basic/TokenKinds.def
    M clang/lib/Basic/OperatorPrecedence.cpp
    M clang/lib/Lex/Lexer.cpp
    M clang/lib/Parse/ParseExpr.cpp
    M clang/lib/Sema/SemaCodeComplete.cpp
    M clang/test/SemaOpenCL/unsupported.cl

  Log Message:
  -----------
  Remove ^^ as a token in OpenCL (#108224)

OpenCL has a reserved operator (^^), the use of which was diagnosed as
an error (735c6cdebdcd4292928079cb18a90f0dd5cd65fb). However, OpenCL
also encourages working with the blocks language extension. This token
has a parsing ambiguity as a result. Consider:

  unsigned x=0;
  unsigned y=x^^{return 0;}();

This should result in y holding the value zero (0^0) through an
immediately invoked block call as the right-hand side of the xor
operator. However, it causes errors instead because of this reserved
token: https://godbolt.org/z/navf7jTv1

This token is still reserved in OpenCL 3.0, so we still wish to issue a
diagnostic for its use. However, we do not need to create a token for an
extension point that's been unused for about a decade. So this patch
moves the diagnostic from a parsing diagnostic to a lexing diagnostic
and no longer forms a single token. The diagnostic behavior is slightly
worse as a result, but still seems acceptable.

Part of the reason this is coming up is because WG21 is considering
using ^^ as a token for reflection, so this token may come back in the
future.



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