llvm-project/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

//===--- SemaTemplateInstantiateDecl.cpp - C++ Template Decl Instantiation ===/
//
//                     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 instantiation for declarations.
//
//===----------------------------------------------------------------------===/
#include "Sema.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DeclVisitor.h"
#include "clang/AST/Expr.h"
#include "llvm/Support/Compiler.h"

using namespace clang;

namespace {
  class VISIBILITY_HIDDEN TemplateDeclInstantiator 
    : public DeclVisitor<TemplateDeclInstantiator, Decl *> 
  {
    Sema &SemaRef;
    DeclContext *Owner;
    const TemplateArgument *TemplateArgs;
    unsigned NumTemplateArgs;
    
  public:
    typedef Sema::OwningExprResult OwningExprResult;

    TemplateDeclInstantiator(Sema &SemaRef, DeclContext *Owner,
                             const TemplateArgument *TemplateArgs,
                             unsigned NumTemplateArgs)
      : SemaRef(SemaRef), Owner(Owner), TemplateArgs(TemplateArgs), 
        NumTemplateArgs(NumTemplateArgs) { }
    
    // FIXME: Once we get closer to completion, replace these
    // manually-written declarations with automatically-generated ones
    // from clang/AST/DeclNodes.def.
    Decl *VisitTypedefDecl(TypedefDecl *D);
    Decl *VisitFieldDecl(FieldDecl *D);
    Decl *VisitStaticAssertDecl(StaticAssertDecl *D);
    Decl *VisitEnumDecl(EnumDecl *D);

    // Base case. FIXME: Remove once we can instantiate everything.
    Decl *VisitDecl(Decl *) { 
      return 0;
    }
  };
}

Decl *TemplateDeclInstantiator::VisitTypedefDecl(TypedefDecl *D) {
  bool Invalid = false;
  QualType T = D->getUnderlyingType();
  if (T->isDependentType()) {
    T = SemaRef.InstantiateType(T, TemplateArgs, NumTemplateArgs,
                                D->getLocation(),
                                D->getDeclName());
    if (T.isNull()) {
      Invalid = true;
      T = SemaRef.Context.IntTy;
    }
  }
       
  // Create the new typedef
  TypedefDecl *Typedef
    = TypedefDecl::Create(SemaRef.Context, Owner, D->getLocation(),
                          D->getIdentifier(), T);
  if (Invalid)
    Typedef->setInvalidDecl();

  Owner->addDecl(Typedef);
  return Typedef;
}

Decl *TemplateDeclInstantiator::VisitFieldDecl(FieldDecl *D) {
  bool Invalid = false;
  QualType T = D->getType();
  if (T->isDependentType())  {
    T = SemaRef.InstantiateType(T, TemplateArgs, NumTemplateArgs,
                                D->getLocation(),
                                D->getDeclName());
    if (!T.isNull() && T->isFunctionType()) {
      // C++ [temp.arg.type]p3:
      //   If a declaration acquires a function type through a type
      //   dependent on a template-parameter and this causes a
      //   declaration that does not use the syntactic form of a
      //   function declarator to have function type, the program is
      //   ill-formed.
      SemaRef.Diag(D->getLocation(), diag::err_field_instantiates_to_function)
        << T;
      T = QualType();
      Invalid = true;
    }
  }

  Expr *BitWidth = D->getBitWidth();
  if (Invalid)
    BitWidth = 0;
  else if (BitWidth) {
    OwningExprResult InstantiatedBitWidth
      = SemaRef.InstantiateExpr(BitWidth, TemplateArgs, NumTemplateArgs);
    if (InstantiatedBitWidth.isInvalid()) {
      Invalid = true;
      BitWidth = 0;
    } else
      BitWidth = (Expr *)InstantiatedBitWidth.release();
  }

  FieldDecl *Field = SemaRef.CheckFieldDecl(D->getDeclName(), T,
                                            cast<RecordDecl>(Owner), 
                                            D->getLocation(),
                                            D->isMutable(),
                                            BitWidth,
                                            D->getAccess(),
                                            0);
  if (Field) {
    if (Invalid)
      Field->setInvalidDecl();
    
    Owner->addDecl(Field);
  }

  return Field;
}

Decl *TemplateDeclInstantiator::VisitStaticAssertDecl(StaticAssertDecl *D) {
  Expr *AssertExpr = D->getAssertExpr();
      
  OwningExprResult InstantiatedAssertExpr
    = SemaRef.InstantiateExpr(AssertExpr, TemplateArgs, NumTemplateArgs);
  if (InstantiatedAssertExpr.isInvalid())
    return 0;

  OwningExprResult Message = SemaRef.Clone(D->getMessage());
  Decl *StaticAssert 
    = (Decl *)SemaRef.ActOnStaticAssertDeclaration(D->getLocation(), 
                                                move(InstantiatedAssertExpr),
                                                   move(Message));
  return StaticAssert;
}

Decl *TemplateDeclInstantiator::VisitEnumDecl(EnumDecl *D) {
  EnumDecl *Enum = EnumDecl::Create(SemaRef.Context, Owner, 
                                    D->getLocation(), D->getIdentifier(),
                                    /*PrevDecl=*/0);
  Owner->addDecl(Enum);
  Enum->startDefinition();

  llvm::SmallVector<Sema::DeclTy *, 16> Enumerators;

  EnumConstantDecl *LastEnumConst = 0;
  for (EnumDecl::enumerator_iterator EC = D->enumerator_begin(),
         ECEnd = D->enumerator_end();
       EC != ECEnd; ++EC) {
    // The specified value for the enumerator.
    OwningExprResult Value = SemaRef.Owned((Expr *)0);
    if (Expr *UninstValue = EC->getInitExpr())
      Value = SemaRef.InstantiateExpr(UninstValue, 
                                      TemplateArgs, NumTemplateArgs);

    // Drop the initial value and continue.
    bool isInvalid = false;
    if (Value.isInvalid()) {
      Value = SemaRef.Owned((Expr *)0);
      isInvalid = true;
    }

    EnumConstantDecl *EnumConst 
      = SemaRef.CheckEnumConstant(Enum, LastEnumConst,
                                  EC->getLocation(), EC->getIdentifier(),
                                  move(Value));

    if (isInvalid) {
      if (EnumConst)
        EnumConst->setInvalidDecl();
      Enum->setInvalidDecl();
    }

    if (EnumConst) {
      Enum->addDecl(EnumConst);
      Enumerators.push_back(EnumConst);
      LastEnumConst = EnumConst;
    }
  }
      
  SemaRef.ActOnEnumBody(Enum->getLocation(), Enum,
                        &Enumerators[0], Enumerators.size());

  return Enum;
}

Decl *Sema::InstantiateDecl(Decl *D, DeclContext *Owner,
                            const TemplateArgument *TemplateArgs,
                            unsigned NumTemplateArgs) {
  TemplateDeclInstantiator Instantiator(*this, Owner, TemplateArgs,
                                        NumTemplateArgs);
  return Instantiator.Visit(D);
}