DR1391: Check for implicit conversion sequences for non-dependent function
template parameters between deduction and substitution. The idea is to accept
as many cases as possible, on the basis that substitution failure outside
the immediate context is much more common during substitution than during
implicit conversion sequence formation.
This does not implement the partial ordering portion of DR1391, which so
far appears to be misguided.
llvm-svn: 290808
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 0bc85a2..dc29183 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -2849,14 +2849,13 @@
///
/// \param OriginalCallArgs If non-NULL, the original call arguments against
/// which the deduced argument types should be compared.
-Sema::TemplateDeductionResult
-Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
- SmallVectorImpl<DeducedTemplateArgument> &Deduced,
- unsigned NumExplicitlySpecified,
- FunctionDecl *&Specialization,
- TemplateDeductionInfo &Info,
- SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
- bool PartialOverloading) {
+Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
+ FunctionTemplateDecl *FunctionTemplate,
+ SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+ unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
+ TemplateDeductionInfo &Info,
+ SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs,
+ bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
// Unevaluated SFINAE context.
EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
SFINAETrap Trap(*this);
@@ -2883,6 +2882,18 @@
PartialOverloading))
return Result;
+ // C++ [temp.deduct.call]p10: [DR1391]
+ // If deduction succeeds for all parameters that contain
+ // template-parameters that participate in template argument deduction,
+ // and all template arguments are explicitly specified, deduced, or
+ // obtained from default template arguments, remaining parameters are then
+ // compared with the corresponding arguments. For each remaining parameter
+ // P with a type that was non-dependent before substitution of any
+ // explicitly-specified template arguments, if the corresponding argument
+ // A cannot be implicitly converted to P, deduction fails.
+ if (CheckNonDependent())
+ return TDK_NonDependentConversionFailure;
+
// Form the template argument list from the deduced template arguments.
TemplateArgumentList *DeducedArgumentList
= TemplateArgumentList::CreateCopy(Context, Builder);
@@ -3307,12 +3318,17 @@
/// \param Info the argument will be updated to provide additional information
/// about template argument deduction.
///
+/// \param CheckNonDependent A callback to invoke to check conversions for
+/// non-dependent parameters, between deduction and substitution, per DR1391.
+/// If this returns true, substitution will be skipped and we return
+/// TDK_NonDependentConversionFailure.
+///
/// \returns the result of template argument deduction.
Sema::TemplateDeductionResult Sema::DeduceTemplateArguments(
FunctionTemplateDecl *FunctionTemplate,
TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
FunctionDecl *&Specialization, TemplateDeductionInfo &Info,
- bool PartialOverloading) {
+ bool PartialOverloading, llvm::function_ref<bool()> CheckNonDependent) {
if (FunctionTemplate->isInvalidDecl())
return TDK_Invalid;
@@ -3496,7 +3512,7 @@
return FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
NumExplicitlySpecified, Specialization,
Info, &OriginalCallArgs,
- PartialOverloading);
+ PartialOverloading, CheckNonDependent);
}
QualType Sema::adjustCCAndNoReturn(QualType ArgFunctionType,