diff options
author | Richard Smith <richard-llvm@metafoo.co.uk> | 2019-05-09 03:31:27 +0000 |
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committer | Richard Smith <richard-llvm@metafoo.co.uk> | 2019-05-09 03:31:27 +0000 |
commit | fb98e7c13da639f34f34830a4e675367e0816cb6 (patch) | |
tree | 70e025e9b4a31559d1f061e72439b5414537ad3b /lib/Parse/ParseExprCXX.cpp | |
parent | 70cd574857c6023b8c60e325c4029a23f716c2dd (diff) |
[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.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@360308 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Parse/ParseExprCXX.cpp')
-rw-r--r-- | lib/Parse/ParseExprCXX.cpp | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp index fbafb43688..c6f457fb14 100644 --- a/lib/Parse/ParseExprCXX.cpp +++ b/lib/Parse/ParseExprCXX.cpp @@ -487,6 +487,14 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS, EnteringContext, Template, MemberOfUnknownSpecialization)) { + // If lookup didn't find anything, we treat the name as a template-name + // anyway. C++20 requires this, and in prior language modes it improves + // error recovery. But before we commit to this, check that we actually + // have something that looks like a template-argument-list next. + if (!IsTypename && TNK == TNK_Undeclared_template && + isTemplateArgumentList(1) == TPResult::False) + break; + // We have found a template name, so annotate this token // with a template-id annotation. We do not permit the // template-id to be translated into a type annotation, @@ -501,7 +509,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS, } if (MemberOfUnknownSpecialization && (ObjectType || SS.isSet()) && - (IsTypename || IsTemplateArgumentList(1))) { + (IsTypename || isTemplateArgumentList(1) == TPResult::True)) { // We have something like t::getAs<T>, where getAs is a // member of an unknown specialization. However, this will only // parse correctly as a template, so suggest the keyword 'template' @@ -2138,9 +2146,15 @@ bool Parser::ParseUnqualifiedIdTemplateId(CXXScopeSpec &SS, TemplateKWLoc.isValid(), Id, ObjectType, EnteringContext, Template, MemberOfUnknownSpecialization); + // If lookup found nothing but we're assuming that this is a template + // name, double-check that makes sense syntactically before committing + // to it. + if (TNK == TNK_Undeclared_template && + isTemplateArgumentList(0) == TPResult::False) + return false; if (TNK == TNK_Non_template && MemberOfUnknownSpecialization && - ObjectType && IsTemplateArgumentList()) { + ObjectType && isTemplateArgumentList(0) == TPResult::True) { // We have something like t->getAs<T>(), where getAs is a // member of an unknown specialization. However, this will only // parse correctly as a template, so suggest the keyword 'template' @@ -2244,11 +2258,9 @@ bool Parser::ParseUnqualifiedIdTemplateId(CXXScopeSpec &SS, ASTTemplateArgsPtr TemplateArgsPtr(TemplateArgs); // Constructor and destructor names. - TypeResult Type - = Actions.ActOnTemplateIdType(SS, TemplateKWLoc, - Template, Name, NameLoc, - LAngleLoc, TemplateArgsPtr, RAngleLoc, - /*IsCtorOrDtorName=*/true); + TypeResult Type = Actions.ActOnTemplateIdType( + getCurScope(), SS, TemplateKWLoc, Template, Name, NameLoc, LAngleLoc, + TemplateArgsPtr, RAngleLoc, /*IsCtorOrDtorName=*/true); if (Type.isInvalid()) return true; |