[PATCH] D18510: [cxx1z-constexpr-lambda] Make conversion function constexpr

[Faisal Vali via cfe-commits]

faisalv created this revision.
faisalv added a reviewer: rsmith.
faisalv added a subscriber: cfe-commits.

Mark the lambda's conversion to function-pointer as incontrovertibly constexpr. 

auto L = [](auto a) { return a; };
constexpr int* (*fp)(int*) = L; // This is now allowed.

By itself this is not terribly useful.  A subsequent patch will enable a call through the function pointer in a constant expression if the lambda's synthesized call operator is constexpr.

The more interesting/controversial aspect of the patch (and the part I really need feedback on) is emission of a warning if this is called in pre-c++1z constant expressions, and making sure such warnings are ignored when determining if the constant expression evaluation succeeded. Look forward to your feedback...







http://reviews.llvm.org/D18510

Files:
  include/clang/AST/ASTContext.h
  include/clang/Basic/DiagnosticASTKinds.td
  lib/AST/ASTContext.cpp
  lib/AST/Decl.cpp
  lib/AST/ExprConstant.cpp
  lib/Sema/SemaDecl.cpp
  lib/Sema/SemaDeclAttr.cpp
  lib/Sema/SemaDeclCXX.cpp
  lib/Sema/SemaLambda.cpp
  test/SemaCXX/cxx1z-constexpr-lambdas.cpp

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