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//===------- SemaTemplateDeduction.cpp - Template Argument Deduction ------===/
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//===----------------------------------------------------------------------===/
//
// This file implements C++ template argument deduction.
//
//===----------------------------------------------------------------------===/
#include "Sema.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/Parse/DeclSpec.h"
#include "llvm/Support/Compiler.h"
using namespace clang;
static bool DeduceTemplateArguments(ASTContext &Context, QualType Param,
QualType Arg,
llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
// We only want to look at the canonical types, since typedefs and
// sugar are not part of template argument deduction.
Param = Context.getCanonicalType(Param);
Arg = Context.getCanonicalType(Arg);
// If the parameter type is not dependent, just compare the types
// directly.
if (!Param->isDependentType())
return Param == Arg;
// FIXME: Use a visitor or switch to handle all of the kinds of
// types that the parameter may be.
if (const TemplateTypeParmType *TemplateTypeParm
= Param->getAsTemplateTypeParmType()) {
// The argument type can not be less qualified than the parameter
// type.
if (Param.isMoreQualifiedThan(Arg))
return false;
assert(TemplateTypeParm->getDepth() == 0 && "Can't deduce with depth > 0");
unsigned Quals = Arg.getCVRQualifiers() & ~Param.getCVRQualifiers();
QualType DeducedType = Arg.getQualifiedType(Quals);
unsigned Index = TemplateTypeParm->getIndex();
if (Deduced[Index].isNull())
Deduced[Index] = TemplateArgument(SourceLocation(), DeducedType);
else {
// C++ [temp.deduct.type]p2:
// [...] If type deduction cannot be done for any P/A pair, or if for
// any pair the deduction leads to more than one possible set of
// deduced values, or if different pairs yield different deduced
// values, or if any template argument remains neither deduced nor
// explicitly specified, template argument deduction fails.
if (Deduced[Index].getAsType() != DeducedType)
return false;
}
return true;
}
if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
return false;
switch (Param->getTypeClass()) {
case Type::Pointer: {
const PointerType *PointerArg = Arg->getAsPointerType();
if (!PointerArg)
return false;
return DeduceTemplateArguments(Context,
cast<PointerType>(Param)->getPointeeType(),
PointerArg->getPointeeType(),
Deduced);
}
case Type::LValueReference: {
const LValueReferenceType *ReferenceArg = Arg->getAsLValueReferenceType();
if (!ReferenceArg)
return false;
return DeduceTemplateArguments(Context,
cast<LValueReferenceType>(Param)->getPointeeType(),
ReferenceArg->getPointeeType(),
Deduced);
}
case Type::RValueReference: {
const RValueReferenceType *ReferenceArg = Arg->getAsRValueReferenceType();
if (!ReferenceArg)
return false;
return DeduceTemplateArguments(Context,
cast<RValueReferenceType>(Param)->getPointeeType(),
ReferenceArg->getPointeeType(),
Deduced);
}
case Type::IncompleteArray: {
const IncompleteArrayType *IncompleteArrayArg =
Context.getAsIncompleteArrayType(Arg);
if (!IncompleteArrayArg)
return false;
return DeduceTemplateArguments(Context,
Context.getAsIncompleteArrayType(Param)->getElementType(),
IncompleteArrayArg->getElementType(),
Deduced);
}
case Type::ConstantArray: {
const ConstantArrayType *ConstantArrayArg =
Context.getAsConstantArrayType(Arg);
if (!ConstantArrayArg)
return false;
const ConstantArrayType *ConstantArrayParm =
Context.getAsConstantArrayType(Param);
if (ConstantArrayArg->getSize() != ConstantArrayParm->getSize())
return false;
return DeduceTemplateArguments(Context,
ConstantArrayParm->getElementType(),
ConstantArrayArg->getElementType(),
Deduced);
}
default:
break;
}
// FIXME: Many more cases to go (to go).
return false;
}
static bool
DeduceTemplateArguments(ASTContext &Context, const TemplateArgument &Param,
const TemplateArgument &Arg,
llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
assert(Param.getKind() == Arg.getKind() &&
"Template argument kind mismatch during deduction");
switch (Param.getKind()) {
case TemplateArgument::Type:
return DeduceTemplateArguments(Context, Param.getAsType(),
Arg.getAsType(), Deduced);
default:
return false;
}
}
static bool
DeduceTemplateArguments(ASTContext &Context,
const TemplateArgumentList &ParamList,
const TemplateArgumentList &ArgList,
llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
assert(ParamList.size() == ArgList.size());
for (unsigned I = 0, N = ParamList.size(); I != N; ++I) {
if (!DeduceTemplateArguments(Context, ParamList[I], ArgList[I], Deduced))
return false;
}
return true;
}
bool
Sema::DeduceTemplateArguments(ClassTemplatePartialSpecializationDecl *Partial,
const TemplateArgumentList &TemplateArgs) {
llvm::SmallVector<TemplateArgument, 4> Deduced;
Deduced.resize(Partial->getTemplateParameters()->size());
return ::DeduceTemplateArguments(Context, Partial->getTemplateArgs(),
TemplateArgs, Deduced);
}
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