Prior to the patch, we didn't build a DeclRefExpr if the Decl being
referred to is invalid, because many clang downstream AST consumers
assume it, violating it will cause many diagnostic regressions.
With this patch, we build a DeclRefExpr enven for an invalid decl (when the
AcceptInvalidDecl is true), and wrap it with a dependent-type
RecoveryExpr (to prevent follow-up semantic analysis, and diagnostic
regressions).
This is a revised version of https://reviews.llvm.org/D76831
Reviewed By: sammccall
Differential Revision: https://reviews.llvm.org/D121599
We would previously try to evaluate atomic constraints of non-template functions as-is,
and since they are now unevaluated at first, this would cause incorrect evaluation (bugs #44657, #44656).
Substitute into atomic constraints of non-template functions as we would atomic constraints
of template functions, in order to rebuild the expressions in a constant-evaluated context.
As per P1980R0, constraint expressions are unevaluated operands, and their constituent atomic
constraints only become constant evaluated during satisfaction checking.
Change the evaluation context during parsing and instantiation of constraints to unevaluated.
Haojian Wu