A little tweak to the SFINAE condition reporting. Don't say:
candidate template ignored: substitution failed [with T = int]: no type named 'type' in 'std::enable_if<false, void>'
Instead, just say:
candidate template ignored: disabled by 'enable_if' [with T = int]
... and point at the enable_if condition which (we assume) failed.
This is applied to all cases where the user writes 'typename enable_if<...>::type' (optionally prefixed with a nested name specifier), and 'enable_if<...>' names a complete class type which does not have a member named 'type', and this results in a candidate function being ignored in a SFINAE context. Thus it catches 'std::enable_if', 'std::__1::enable_if', 'boost::enable_if' and 'llvm::enable_if'.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156463 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index bde80fd..7faf80e 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -6923,6 +6923,42 @@
}
+/// Determine whether this failed name lookup should be treated as being
+/// disabled by a usage of std::enable_if.
+static bool isEnableIf(NestedNameSpecifierLoc NNS, const IdentifierInfo &II,
+ SourceRange &CondRange) {
+ // We must be looking for a ::type...
+ if (!II.isStr("type"))
+ return false;
+
+ // ... within an explicitly-written template specialization...
+ if (!NNS || !NNS.getNestedNameSpecifier()->getAsType())
+ return false;
+ TypeLoc EnableIfTy = NNS.getTypeLoc();
+ TemplateSpecializationTypeLoc *EnableIfTSTLoc =
+ dyn_cast<TemplateSpecializationTypeLoc>(&EnableIfTy);
+ if (!EnableIfTSTLoc || EnableIfTSTLoc->getNumArgs() == 0)
+ return false;
+ const TemplateSpecializationType *EnableIfTST =
+ cast<TemplateSpecializationType>(EnableIfTSTLoc->getTypePtr());
+
+ // ... which names a complete class template declaration...
+ const TemplateDecl *EnableIfDecl =
+ EnableIfTST->getTemplateName().getAsTemplateDecl();
+ if (!EnableIfDecl || EnableIfTST->isIncompleteType())
+ return false;
+
+ // ... called "enable_if".
+ const IdentifierInfo *EnableIfII =
+ EnableIfDecl->getDeclName().getAsIdentifierInfo();
+ if (!EnableIfII || !EnableIfII->isStr("enable_if"))
+ return false;
+
+ // Assume the first template argument is the condition.
+ CondRange = EnableIfTSTLoc->getArgLoc(0).getSourceRange();
+ return true;
+}
+
/// \brief Build the type that describes a C++ typename specifier,
/// e.g., "typename T::type".
QualType
@@ -6959,9 +6995,19 @@
unsigned DiagID = 0;
Decl *Referenced = 0;
switch (Result.getResultKind()) {
- case LookupResult::NotFound:
+ case LookupResult::NotFound: {
+ // If we're looking up 'type' within a template named 'enable_if', produce
+ // a more specific diagnostic.
+ SourceRange CondRange;
+ if (isEnableIf(QualifierLoc, II, CondRange)) {
+ Diag(CondRange.getBegin(), diag::err_typename_nested_not_found_enable_if)
+ << Ctx << CondRange;
+ return QualType();
+ }
+
DiagID = diag::err_typename_nested_not_found;
break;
+ }
case LookupResult::FoundUnresolvedValue: {
// We found a using declaration that is a value. Most likely, the using