Example #1
0
ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body, 
                                 Scope *CurScope, 
                                 bool IsInstantiation) {
  // Collect information from the lambda scope.
  llvm::SmallVector<LambdaExpr::Capture, 4> Captures;
  llvm::SmallVector<Expr *, 4> CaptureInits;
  LambdaCaptureDefault CaptureDefault;
  CXXRecordDecl *Class;
  CXXMethodDecl *CallOperator;
  SourceRange IntroducerRange;
  bool ExplicitParams;
  bool ExplicitResultType;
  bool LambdaExprNeedsCleanups;
  bool ContainsUnexpandedParameterPack;
  llvm::SmallVector<VarDecl *, 4> ArrayIndexVars;
  llvm::SmallVector<unsigned, 4> ArrayIndexStarts;
  {
    LambdaScopeInfo *LSI = getCurLambda();
    CallOperator = LSI->CallOperator;
    Class = LSI->Lambda;
    IntroducerRange = LSI->IntroducerRange;
    ExplicitParams = LSI->ExplicitParams;
    ExplicitResultType = !LSI->HasImplicitReturnType;
    LambdaExprNeedsCleanups = LSI->ExprNeedsCleanups;
    ContainsUnexpandedParameterPack = LSI->ContainsUnexpandedParameterPack;
    ArrayIndexVars.swap(LSI->ArrayIndexVars);
    ArrayIndexStarts.swap(LSI->ArrayIndexStarts);
    
    // Translate captures.
    for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
      LambdaScopeInfo::Capture From = LSI->Captures[I];
      assert(!From.isBlockCapture() && "Cannot capture __block variables");
      bool IsImplicit = I >= LSI->NumExplicitCaptures;

      // Handle 'this' capture.
      if (From.isThisCapture()) {
        Captures.push_back(LambdaExpr::Capture(From.getLocation(),
                                               IsImplicit,
                                               LCK_This));
        CaptureInits.push_back(new (Context) CXXThisExpr(From.getLocation(),
                                                         getCurrentThisType(),
                                                         /*isImplicit=*/true));
        continue;
      }

      VarDecl *Var = From.getVariable();
      LambdaCaptureKind Kind = From.isCopyCapture()? LCK_ByCopy : LCK_ByRef;
      Captures.push_back(LambdaExpr::Capture(From.getLocation(), IsImplicit, 
                                             Kind, Var, From.getEllipsisLoc()));
      CaptureInits.push_back(From.getCopyExpr());
    }

    switch (LSI->ImpCaptureStyle) {
    case CapturingScopeInfo::ImpCap_None:
      CaptureDefault = LCD_None;
      break;

    case CapturingScopeInfo::ImpCap_LambdaByval:
      CaptureDefault = LCD_ByCopy;
      break;

    case CapturingScopeInfo::ImpCap_LambdaByref:
      CaptureDefault = LCD_ByRef;
      break;

    case CapturingScopeInfo::ImpCap_Block:
      llvm_unreachable("block capture in lambda");
      break;
    }

    // C++11 [expr.prim.lambda]p4:
    //   If a lambda-expression does not include a
    //   trailing-return-type, it is as if the trailing-return-type
    //   denotes the following type:
    // FIXME: Assumes current resolution to core issue 975.
    if (LSI->HasImplicitReturnType) {
      deduceClosureReturnType(*LSI);

      //   - if there are no return statements in the
      //     compound-statement, or all return statements return
      //     either an expression of type void or no expression or
      //     braced-init-list, the type void;
      if (LSI->ReturnType.isNull()) {
        LSI->ReturnType = Context.VoidTy;
      }

      // Create a function type with the inferred return type.
      const FunctionProtoType *Proto
        = CallOperator->getType()->getAs<FunctionProtoType>();
      QualType FunctionTy
        = Context.getFunctionType(LSI->ReturnType,
                                  Proto->arg_type_begin(),
                                  Proto->getNumArgs(),
                                  Proto->getExtProtoInfo());
      CallOperator->setType(FunctionTy);
    }

    // C++ [expr.prim.lambda]p7:
    //   The lambda-expression's compound-statement yields the
    //   function-body (8.4) of the function call operator [...].
    ActOnFinishFunctionBody(CallOperator, Body, IsInstantiation);
    CallOperator->setLexicalDeclContext(Class);
    Class->addDecl(CallOperator);
    PopExpressionEvaluationContext();

    // C++11 [expr.prim.lambda]p6:
    //   The closure type for a lambda-expression with no lambda-capture
    //   has a public non-virtual non-explicit const conversion function
    //   to pointer to function having the same parameter and return
    //   types as the closure type's function call operator.
    if (Captures.empty() && CaptureDefault == LCD_None)
      addFunctionPointerConversion(*this, IntroducerRange, Class,
                                   CallOperator);

    // Objective-C++:
    //   The closure type for a lambda-expression has a public non-virtual
    //   non-explicit const conversion function to a block pointer having the
    //   same parameter and return types as the closure type's function call
    //   operator.
    if (getLangOpts().Blocks && getLangOpts().ObjC1)
      addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
    
    // Finalize the lambda class.
    SmallVector<Decl*, 4> Fields;
    for (RecordDecl::field_iterator i = Class->field_begin(),
                                    e = Class->field_end(); i != e; ++i)
      Fields.push_back(*i);
    ActOnFields(0, Class->getLocation(), Class, Fields, 
                SourceLocation(), SourceLocation(), 0);
    CheckCompletedCXXClass(Class);
  }

  if (LambdaExprNeedsCleanups)
    ExprNeedsCleanups = true;
  
  LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange, 
                                          CaptureDefault, Captures, 
                                          ExplicitParams, ExplicitResultType,
                                          CaptureInits, ArrayIndexVars, 
                                          ArrayIndexStarts, Body->getLocEnd(),
                                          ContainsUnexpandedParameterPack);

  // C++11 [expr.prim.lambda]p2:
  //   A lambda-expression shall not appear in an unevaluated operand
  //   (Clause 5).
  if (!CurContext->isDependentContext()) {
    switch (ExprEvalContexts.back().Context) {
    case Unevaluated:
      // We don't actually diagnose this case immediately, because we
      // could be within a context where we might find out later that
      // the expression is potentially evaluated (e.g., for typeid).
      ExprEvalContexts.back().Lambdas.push_back(Lambda);
      break;

    case ConstantEvaluated:
    case PotentiallyEvaluated:
    case PotentiallyEvaluatedIfUsed:
      break;
    }
  }
  
  return MaybeBindToTemporary(Lambda);
}
Example #2
0
ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body, 
                                 Scope *CurScope, 
                                 llvm::Optional<unsigned> ManglingNumber,
                                 Decl *ContextDecl,
                                 bool IsInstantiation) {
  // Collect information from the lambda scope.
  llvm::SmallVector<LambdaExpr::Capture, 4> Captures;
  llvm::SmallVector<Expr *, 4> CaptureInits;
  LambdaCaptureDefault CaptureDefault;
  CXXRecordDecl *Class;
  CXXMethodDecl *CallOperator;
  SourceRange IntroducerRange;
  bool ExplicitParams;
  bool ExplicitResultType;
  bool LambdaExprNeedsCleanups;
  llvm::SmallVector<VarDecl *, 4> ArrayIndexVars;
  llvm::SmallVector<unsigned, 4> ArrayIndexStarts;
  {
    LambdaScopeInfo *LSI = getCurLambda();
    CallOperator = LSI->CallOperator;
    Class = LSI->Lambda;
    IntroducerRange = LSI->IntroducerRange;
    ExplicitParams = LSI->ExplicitParams;
    ExplicitResultType = !LSI->HasImplicitReturnType;
    LambdaExprNeedsCleanups = LSI->ExprNeedsCleanups;
    ArrayIndexVars.swap(LSI->ArrayIndexVars);
    ArrayIndexStarts.swap(LSI->ArrayIndexStarts);
    
    // Translate captures.
    for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
      LambdaScopeInfo::Capture From = LSI->Captures[I];
      assert(!From.isBlockCapture() && "Cannot capture __block variables");
      bool IsImplicit = I >= LSI->NumExplicitCaptures;

      // Handle 'this' capture.
      if (From.isThisCapture()) {
        Captures.push_back(LambdaExpr::Capture(From.getLocation(),
                                               IsImplicit,
                                               LCK_This));
        CaptureInits.push_back(new (Context) CXXThisExpr(From.getLocation(),
                                                         getCurrentThisType(),
                                                         /*isImplicit=*/true));
        continue;
      }

      VarDecl *Var = From.getVariable();
      LambdaCaptureKind Kind = From.isCopyCapture()? LCK_ByCopy : LCK_ByRef;
      Captures.push_back(LambdaExpr::Capture(From.getLocation(), IsImplicit, 
                                             Kind, Var, From.getEllipsisLoc()));
      CaptureInits.push_back(From.getCopyExpr());
    }

    switch (LSI->ImpCaptureStyle) {
    case CapturingScopeInfo::ImpCap_None:
      CaptureDefault = LCD_None;
      break;

    case CapturingScopeInfo::ImpCap_LambdaByval:
      CaptureDefault = LCD_ByCopy;
      break;

    case CapturingScopeInfo::ImpCap_LambdaByref:
      CaptureDefault = LCD_ByRef;
      break;

    case CapturingScopeInfo::ImpCap_Block:
      llvm_unreachable("block capture in lambda");
      break;
    }

    // C++11 [expr.prim.lambda]p4:
    //   If a lambda-expression does not include a
    //   trailing-return-type, it is as if the trailing-return-type
    //   denotes the following type:
    // FIXME: Assumes current resolution to core issue 975.
    if (LSI->HasImplicitReturnType) {
      //   - if there are no return statements in the
      //     compound-statement, or all return statements return
      //     either an expression of type void or no expression or
      //     braced-init-list, the type void;
      if (LSI->ReturnType.isNull()) {
        LSI->ReturnType = Context.VoidTy;
      } else {
        // C++11 [expr.prim.lambda]p4:
        //   - if the compound-statement is of the form
        //
        //       { attribute-specifier-seq[opt] return expression ; }
        //
        //     the type of the returned expression after
        //     lvalue-to-rvalue conversion (4.1), array-to-pointer
        //     conver- sion (4.2), and function-to-pointer conversion
        //     (4.3);
        //
        // Since we're accepting the resolution to a post-C++11 core
        // issue with a non-trivial extension, provide a warning (by
        // default).
        CompoundStmt *CompoundBody = cast<CompoundStmt>(Body);
        if (!(CompoundBody->size() == 1 &&
              isa<ReturnStmt>(*CompoundBody->body_begin())) &&
            !Context.hasSameType(LSI->ReturnType, Context.VoidTy))
          Diag(IntroducerRange.getBegin(), 
               diag::ext_lambda_implies_void_return);
      }

      // Create a function type with the inferred return type.
      const FunctionProtoType *Proto
        = CallOperator->getType()->getAs<FunctionProtoType>();
      QualType FunctionTy
        = Context.getFunctionType(LSI->ReturnType,
                                  Proto->arg_type_begin(),
                                  Proto->getNumArgs(),
                                  Proto->getExtProtoInfo());
      CallOperator->setType(FunctionTy);
    }

    // C++ [expr.prim.lambda]p7:
    //   The lambda-expression's compound-statement yields the
    //   function-body (8.4) of the function call operator [...].
    ActOnFinishFunctionBody(CallOperator, Body, IsInstantiation);
    CallOperator->setLexicalDeclContext(Class);
    Class->addDecl(CallOperator);
    PopExpressionEvaluationContext();

    // C++11 [expr.prim.lambda]p6:
    //   The closure type for a lambda-expression with no lambda-capture
    //   has a public non-virtual non-explicit const conversion function
    //   to pointer to function having the same parameter and return
    //   types as the closure type's function call operator.
    if (Captures.empty() && CaptureDefault == LCD_None)
      addFunctionPointerConversion(*this, IntroducerRange, Class,
                                   CallOperator);

    // Objective-C++:
    //   The closure type for a lambda-expression has a public non-virtual
    //   non-explicit const conversion function to a block pointer having the
    //   same parameter and return types as the closure type's function call
    //   operator.
    if (getLangOpts().Blocks && getLangOpts().ObjC1)
      addBlockPointerConversion(*this, IntroducerRange, Class, CallOperator);
    
    // Finalize the lambda class.
    SmallVector<Decl*, 4> Fields(Class->field_begin(), Class->field_end());
    ActOnFields(0, Class->getLocation(), Class, Fields, 
                SourceLocation(), SourceLocation(), 0);
    CheckCompletedCXXClass(Class);
  }

  if (LambdaExprNeedsCleanups)
    ExprNeedsCleanups = true;

  // If we don't already have a mangling number for this lambda expression,
  // allocate one now.
  if (!ManglingNumber) {
    ContextDecl = ExprEvalContexts.back().LambdaContextDecl;
    
    enum ContextKind {
      Normal,
      DefaultArgument,
      DataMember,
      StaticDataMember
    } Kind = Normal;

    // Default arguments of member function parameters that appear in a class
    // definition, as well as the initializers of data members, receive special
    // treatment. Identify them.
    if (ContextDecl) {
      if (ParmVarDecl *Param = dyn_cast<ParmVarDecl>(ContextDecl)) {
        if (const DeclContext *LexicalDC
              = Param->getDeclContext()->getLexicalParent())
          if (LexicalDC->isRecord())
            Kind = DefaultArgument;
      } else if (VarDecl *Var = dyn_cast<VarDecl>(ContextDecl)) {
        if (Var->getDeclContext()->isRecord())
          Kind = StaticDataMember;
      } else if (isa<FieldDecl>(ContextDecl)) {
        Kind = DataMember;
      }
    }        
    
    switch (Kind) {
    case Normal:
      if (CurContext->isDependentContext() || isInInlineFunction(CurContext))
        ManglingNumber = Context.getLambdaManglingNumber(CallOperator);
      else
        ManglingNumber = 0;
        
      // There is no special context for this lambda.
      ContextDecl = 0;        
      break;
      
    case StaticDataMember:
      if (!CurContext->isDependentContext()) {
        ManglingNumber = 0;
        ContextDecl = 0;
        break;
      }
      // Fall through to assign a mangling number.
        
    case DataMember:
    case DefaultArgument:
      ManglingNumber = ExprEvalContexts.back().getLambdaMangleContext()
                         .getManglingNumber(CallOperator);
      break;
    }
  }
  
  LambdaExpr *Lambda = LambdaExpr::Create(Context, Class, IntroducerRange, 
                                          CaptureDefault, Captures, 
                                          ExplicitParams, ExplicitResultType,
                                          CaptureInits, ArrayIndexVars, 
                                          ArrayIndexStarts, Body->getLocEnd(),
                                          *ManglingNumber, ContextDecl);

  // C++11 [expr.prim.lambda]p2:
  //   A lambda-expression shall not appear in an unevaluated operand
  //   (Clause 5).
  if (!CurContext->isDependentContext()) {
    switch (ExprEvalContexts.back().Context) {
    case Unevaluated:
      // We don't actually diagnose this case immediately, because we
      // could be within a context where we might find out later that
      // the expression is potentially evaluated (e.g., for typeid).
      ExprEvalContexts.back().Lambdas.push_back(Lambda);
      break;

    case ConstantEvaluated:
    case PotentiallyEvaluated:
    case PotentiallyEvaluatedIfUsed:
      break;
    }
  }
  
  return MaybeBindToTemporary(Lambda);
}