From b23c5e8c3df850177449268c5ca7dbf986157525 Mon Sep 17 00:00:00 2001 From: Richard Smith Date: Thu, 9 May 2019 03:31:27 +0000 Subject: [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 --- clang/lib/AST/ASTContext.cpp | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'clang/lib/AST/ASTContext.cpp') diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp index 63488853759..c144e01626e 100644 --- a/clang/lib/AST/ASTContext.cpp +++ b/clang/lib/AST/ASTContext.cpp @@ -5226,6 +5226,11 @@ ASTContext::getNameForTemplate(TemplateName Name, return DeclarationNameInfo((*Storage->begin())->getDeclName(), NameLoc); } + case TemplateName::AssumedTemplate: { + AssumedTemplateStorage *Storage = Name.getAsAssumedTemplateName(); + return DeclarationNameInfo(Storage->getDeclName(), NameLoc); + } + case TemplateName::DependentTemplate: { DependentTemplateName *DTN = Name.getAsDependentTemplateName(); DeclarationName DName; @@ -5273,7 +5278,8 @@ TemplateName ASTContext::getCanonicalTemplateName(TemplateName Name) const { } case TemplateName::OverloadedTemplate: - llvm_unreachable("cannot canonicalize overloaded template"); + case TemplateName::AssumedTemplate: + llvm_unreachable("cannot canonicalize unresolved template"); case TemplateName::DependentTemplate: { DependentTemplateName *DTN = Name.getAsDependentTemplateName(); @@ -7620,6 +7626,13 @@ ASTContext::getOverloadedTemplateName(UnresolvedSetIterator Begin, return TemplateName(OT); } +/// Retrieve a template name representing an unqualified-id that has been +/// assumed to name a template for ADL purposes. +TemplateName ASTContext::getAssumedTemplateName(DeclarationName Name) const { + auto *OT = new (*this) AssumedTemplateStorage(Name); + return TemplateName(OT); +} + /// Retrieve the template name that represents a qualified /// template name such as \c std::vector. TemplateName -- cgit v1.2.3