The below commit started to cause the following failure:
$ cat test.cc template<typename> struct S1 { static int const n = 0; }; template<int, typename> struct S2 { typedef int t; }; template<typename T> struct S3 { typename S2<S1<T>::n < 0, int>::t n; }; $ clang++ -fsyntax-only test.cc test.cc:3:53: error: use 'template' keyword to treat 'n' as a dependent template name template<typename T> struct S3 { typename S2<S1<T>::n < 0, int>::t n; }; ^template test.cc:3:46: error: missing 'typename' prior to dependent type name'S1<T>::S1<T>::n<0, int>::t' template<typename T> struct S3 { typename S2<S1<T>::n < 0, int>::t n; }; ^~~~~~~~~~~~~~~~~~~~~typename test.cc:3:68: error: expected '>'template<typename T> struct S3 { typename S2<S1<T>::n < 0, int>::t n; }; ^ 3 errors generated.
On 09/05/2019 05:31, Richard Smith via cfe-commits wrote:
Author: rsmith Date: Wed May 8 20:31:27 2019 New Revision: 360308 URL: http://llvm.org/viewvc/llvm-project?rev=360308&view=rev Log: [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. Added: cfe/trunk/test/SemaCXX/cxx2a-adl-only-template-id.cpp Modified: cfe/trunk/include/clang/AST/ASTContext.h cfe/trunk/include/clang/AST/DeclarationName.h cfe/trunk/include/clang/AST/TemplateName.h cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td cfe/trunk/include/clang/Basic/TemplateKinds.h cfe/trunk/include/clang/Parse/Parser.h cfe/trunk/include/clang/Sema/Sema.h cfe/trunk/lib/AST/ASTContext.cpp cfe/trunk/lib/AST/ASTImporter.cpp cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp cfe/trunk/lib/AST/ItaniumMangle.cpp cfe/trunk/lib/AST/ODRHash.cpp cfe/trunk/lib/AST/TemplateName.cpp cfe/trunk/lib/Parse/ParseDecl.cpp cfe/trunk/lib/Parse/ParseDeclCXX.cpp cfe/trunk/lib/Parse/ParseExprCXX.cpp cfe/trunk/lib/Parse/ParseTemplate.cpp cfe/trunk/lib/Parse/ParseTentative.cpp cfe/trunk/lib/Parse/Parser.cpp cfe/trunk/lib/Sema/SemaCXXScopeSpec.cpp cfe/trunk/lib/Sema/SemaDecl.cpp cfe/trunk/lib/Sema/SemaDeclCXX.cpp cfe/trunk/lib/Sema/SemaExpr.cpp cfe/trunk/lib/Sema/SemaExprCXX.cpp cfe/trunk/lib/Sema/SemaOverload.cpp cfe/trunk/lib/Sema/SemaTemplate.cpp cfe/trunk/lib/Serialization/ASTReader.cpp cfe/trunk/lib/Serialization/ASTWriter.cpp cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.unqual/p3.cpp cfe/trunk/test/CXX/drs/dr2xx.cpp cfe/trunk/test/CXX/drs/dr6xx.cpp cfe/trunk/test/CXX/temp/temp.spec/temp.explicit/p5.cpp cfe/trunk/test/FixIt/typo-crash.cpp cfe/trunk/test/Misc/diag-template-diffing.cpp cfe/trunk/test/Modules/module-private.cpp cfe/trunk/test/Modules/submodules-merge-defs.cpp cfe/trunk/test/Parser/cxx-ambig-init-templ.cpp cfe/trunk/test/Parser/cxx-template-argument.cpp cfe/trunk/test/Parser/cxx-template-decl.cpp cfe/trunk/test/SemaCXX/alias-template.cpp cfe/trunk/test/SemaCXX/class.cpp cfe/trunk/test/SemaCXX/destructor.cpp cfe/trunk/test/SemaCXX/invalid-member-expr.cpp cfe/trunk/test/SemaCXX/typo-correction.cpp cfe/trunk/test/SemaTemplate/dependent-base-classes.cpp cfe/trunk/test/SemaTemplate/dependent-template-recover.cpp cfe/trunk/test/SemaTemplate/rdar9173693.cpp cfe/trunk/test/SemaTemplate/recovery-crash.cpp cfe/trunk/tools/libclang/CIndex.cpp cfe/trunk/www/cxx_status.html
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