llvm-project

bb38a428 - [clang] make concept normalization a SFINAE context (#197356)

[clang] make concept normalization a SFINAE context (#197356) It is incorrect to allow the substitution failures in concept normalization to make the program ill-formed. These can happen when comparing the equivalence of constraints for redeclaration checking, and a failure here only means these declarations are not equivalent. For now, these diagnostics are simply discarded. It would be nice if some day, as part of diagnostics for non-matching out-of-line definitions, we would explain why matching failed for each candidate, and then add these as notes explaining why the constraints were not equivalent.