path: root/lib/Sema/SemaTemplateDeduction.cpp

//===------- 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"

namespace clang {
  /// \brief Various flags that control template argument deduction.
  ///
  /// These flags can be bitwise-OR'd together.
  enum TemplateDeductionFlags {
    /// \brief No template argument deduction flags, which indicates the
    /// strictest results for template argument deduction (as used for, e.g.,
    /// matching class template partial specializations).
    TDF_None = 0,
    /// \brief Within template argument deduction from a function call, we are
    /// matching with a parameter type for which the original parameter was
    /// a reference.
    TDF_ParamWithReferenceType = 0x1,
    /// \brief Within template argument deduction from a function call, we
    /// are matching in a case where we ignore cv-qualifiers.
    TDF_IgnoreQualifiers = 0x02,
    /// \brief Within template argument deduction from a function call,
    /// we are matching in a case where we can perform template argument
    /// deduction from a template-id of a derived class of the argument type.
    TDF_DerivedClass = 0x04
  };
}

using namespace clang;

static Sema::TemplateDeductionResult
DeduceTemplateArguments(ASTContext &Context, 
                        TemplateParameterList *TemplateParams,
                        const TemplateArgument &Param,
                        const TemplateArgument &Arg,
                        Sema::TemplateDeductionInfo &Info,
                        llvm::SmallVectorImpl<TemplateArgument> &Deduced);

/// \brief If the given expression is of a form that permits the deduction
/// of a non-type template parameter, return the declaration of that
/// non-type template parameter.
static NonTypeTemplateParmDecl *getDeducedParameterFromExpr(Expr *E) {
  if (ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(E))
    E = IC->getSubExpr();
  
  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
    return dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl());
  
  return 0;
}

/// \brief Deduce the value of the given non-type template parameter 
/// from the given constant.
static Sema::TemplateDeductionResult
DeduceNonTypeTemplateArgument(ASTContext &Context, 
                              NonTypeTemplateParmDecl *NTTP, 
                              llvm::APSInt Value,
                              Sema::TemplateDeductionInfo &Info,
                              llvm::SmallVectorImpl<TemplateArgument> &Deduced) {
  assert(NTTP->getDepth() == 0 && 
         "Cannot deduce non-type template argument with depth > 0");
  
  if (Deduced[NTTP->getIndex()].isNull()) {
    QualType T