[c++20] Implement P0846R0: allow (ADL-only) calls to template-ids whose
template name is not visible to unqualified lookup.
In order to support this without a severe degradation in our ability to
diagnose typos in template names, this change significantly restructures
the way we handle template-id-shaped syntax for which lookup of the
template name finds nothing.
Instead of eagerly diagnosing an undeclared template name, we now form a
placeholder template-name representing a name that is known to not find
any templates. When the parser sees such a name, it attempts to
disambiguate whether we have a less-than comparison or a template-id.
Any diagnostics or typo-correction for the name are delayed until its
point of use.
The upshot should be a small improvement of our diagostic quality
overall: we now take more syntactic context into account when trying to
resolve an undeclared identifier on the left hand side of a '<'. In
fact, this works well enough that the backwards-compatible portion (for
an undeclared identifier rather than a lookup that finds functions but
no function templates) is enabled in all language modes.
llvm-svn: 360308
diff --git a/clang/lib/AST/ODRHash.cpp b/clang/lib/AST/ODRHash.cpp
index 9d484bd..ba3b2ee 100644
--- a/clang/lib/AST/ODRHash.cpp
+++ b/clang/lib/AST/ODRHash.cpp
@@ -140,6 +140,7 @@
break;
// TODO: Support these cases.
case TemplateName::OverloadedTemplate:
+ case TemplateName::AssumedTemplate:
case TemplateName::QualifiedTemplate:
case TemplateName::DependentTemplate:
case TemplateName::SubstTemplateTemplateParm: