When explicit template arguments are provided for a function call,
substitute those template arguments into the function parameter types
prior to template argument deduction. There's still a bit of work to
do to make this work properly when only some of the template arguments
are specified.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74576 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 5300385..810de04 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -868,6 +868,16 @@
/// \param FunctionTemplate the function template for which we are performing
/// template argument deduction.
///
+/// \param HasExplicitTemplateArgs whether any template arguments were
+/// explicitly specified.
+///
+/// \param ExplicitTemplateArguments when @p HasExplicitTemplateArgs is true,
+/// the explicitly-specified template arguments.
+///
+/// \param NumExplicitTemplateArguments when @p HasExplicitTemplateArgs is true,
+/// the number of explicitly-specified template arguments in
+/// @p ExplicitTemplateArguments. This value may be zero.
+///
/// \param Args the function call arguments
///
/// \param NumArgs the number of arguments in Args
@@ -880,22 +890,22 @@
/// about template argument deduction.
///
/// \returns the result of template argument deduction.
-///
-/// FIXME: We will also need to pass in any explicitly-specified template
-/// arguments.
Sema::TemplateDeductionResult
Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
+ bool HasExplicitTemplateArgs,
+ const TemplateArgument *ExplicitTemplateArgs,
+ unsigned NumExplicitTemplateArgs,
Expr **Args, unsigned NumArgs,
FunctionDecl *&Specialization,
TemplateDeductionInfo &Info) {
FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
-
+
// C++ [temp.deduct.call]p1:
// Template argument deduction is done by comparing each function template
// parameter type (call it P) with the type of the corresponding argument
// of the call (call it A) as described below.
unsigned CheckArgs = NumArgs;
- if (NumArgs < Function->getNumParams())
+ if (NumArgs < Function->getMinRequiredArguments())
return TDK_TooFewArguments;
else if (NumArgs > Function->getNumParams()) {
const FunctionProtoType *Proto
@@ -905,18 +915,83 @@
CheckArgs = Function->getNumParams();
}
-
+
// Template argument deduction for function templates in a SFINAE context.
// Trap any errors that might occur.
SFINAETrap Trap(*this);
-
- // Deduce template arguments from the function parameters.
- llvm::SmallVector<TemplateArgument, 4> Deduced;
- Deduced.resize(FunctionTemplate->getTemplateParameters()->size());
+
+ // The types of the parameters from which we will perform template argument
+ // deduction.
TemplateParameterList *TemplateParams
= FunctionTemplate->getTemplateParameters();
+ llvm::SmallVector<TemplateArgument, 4> Deduced;
+ llvm::SmallVector<QualType, 4> ParamTypes;
+ if (NumExplicitTemplateArgs) {
+ // C++ [temp.arg.explicit]p3:
+ // Template arguments that are present shall be specified in the
+ // declaration order of their corresponding template-parameters. The
+ // template argument list shall not specify more template-arguments than
+ // there are corresponding template-parameters.
+ TemplateArgumentListBuilder Builder(TemplateParams,
+ NumExplicitTemplateArgs);
+ if (CheckTemplateArgumentList(FunctionTemplate,
+ SourceLocation(), SourceLocation(),
+ ExplicitTemplateArgs,
+ NumExplicitTemplateArgs,
+ SourceLocation(),
+ Builder) || Trap.hasErrorOccurred())
+ return TDK_InvalidExplicitArguments;
+
+ // Enter a new template instantiation context for the substitution of the
+ // explicitly-specified template arguments into the
+ InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
+ FunctionTemplate, Deduced.data(), Deduced.size());
+ if (Inst)
+ return TDK_InstantiationDepth;
+
+ // Form the template argument list from the explicitly-specified
+ // template arguments.
+ TemplateArgumentList *ExplicitArgumentList
+ = new (Context) TemplateArgumentList(Context, Builder, /*TakeArgs=*/true);
+ Info.reset(ExplicitArgumentList);
+
+ // Instantiate the types of each of the function parameters given the
+ // explicitly-specified template arguments.
+ for (FunctionDecl::param_iterator P = Function->param_begin(),
+ PEnd = Function->param_end();
+ P != PEnd;
+ ++P) {
+ QualType ParamType = InstantiateType((*P)->getType(),
+ *ExplicitArgumentList,
+ (*P)->getLocation(),
+ (*P)->getDeclName());
+ if (ParamType.isNull() || Trap.hasErrorOccurred())
+ return TDK_SubstitutionFailure;
+
+ ParamTypes.push_back(ParamType);
+ }
+
+ // C++ [temp.arg.explicit]p2:
+ // Trailing template arguments that can be deduced (14.8.2) may be
+ // omitted from the list of explicit template- arguments. If all of the
+ // template arguments can be deduced, they may all be omitted; in this
+ // case, the empty template argument list <> itself may also be omitted.
+ //
+ // Take all of the explicitly-specified arguments and put them into the
+ // set of deduced template arguments.
+ Deduced.reserve(TemplateParams->size());
+ for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I)
+ Deduced.push_back(ExplicitArgumentList->get(I));
+ } else {
+ // Just fill in the parameter types from the function declaration.
+ for (unsigned I = 0; I != CheckArgs; ++I)
+ ParamTypes.push_back(Function->getParamDecl(I)->getType());
+ }
+
+ // Deduce template arguments from the function parameters.
+ Deduced.resize(TemplateParams->size());
for (unsigned I = 0; I != CheckArgs; ++I) {
- QualType ParamType = Function->getParamDecl(I)->getType();
+ QualType ParamType = ParamTypes[I];
QualType ArgType = Args[I]->getType();
// C++ [temp.deduct.call]p2:
@@ -998,11 +1073,6 @@
// FIXME: C++ [temp.deduct.call] paragraphs 6-9 deal with function
// pointer parameters.
}
-
- InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
- FunctionTemplate, Deduced.data(), Deduced.size());
- if (Inst)
- return TDK_InstantiationDepth;
// C++ [temp.deduct.type]p2:
// [...] or if any template argument remains neither deduced nor
@@ -1030,6 +1100,13 @@
= new (Context) TemplateArgumentList(Context, Builder, /*TakeArgs=*/true);
Info.reset(DeducedArgumentList);
+ // Enter a new template instantiation context while we instantiate the
+ // actual function declaration.
+ InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
+ FunctionTemplate, Deduced.data(), Deduced.size());
+ if (Inst)
+ return TDK_InstantiationDepth;
+
// Substitute the deduced template arguments into the function template
// declaration to produce the function template specialization.
Specialization = cast_or_null<FunctionDecl>(