text: //===--- ParseInit.cpp - Initializer Parsing ------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements initializer parsing as specified by C99 6.7.8.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Parse/Parser.h"
  #include "clang/Parse/ParseDiagnostic.h"
  #include "RAIIObjectsForParser.h"
  #include "clang/Sema/Designator.h"
  #include "clang/Sema/Scope.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/Support/raw_ostream.h"
  using namespace clang;
  
  
  /// MayBeDesignationStart - Return true if this token might be the start of a
  /// designator.  If we can tell it is impossible that it is a designator, return
  /// false.
  static bool MayBeDesignationStart(tok::TokenKind K, Preprocessor &PP) {
    switch (K) {
    default: return false;
    case tok::period:      // designator: '.' identifier
    case tok::l_square:    // designator: array-designator
        return true;
    case tok::identifier:  // designation: identifier ':'
      return PP.LookAhead(0).is(tok::colon);
    }
  }
  
  static void CheckArrayDesignatorSyntax(Parser &P, SourceLocation Loc,
                                         Designation &Desig) {
    // If we have exactly one array designator, this used the GNU
    // 'designation: array-designator' extension, otherwise there should be no
    // designators at all!
    if (Desig.getNumDesignators() == 1 &&
        (Desig.getDesignator(0).isArrayDesignator() ||
         Desig.getDesignator(0).isArrayRangeDesignator()))
      P.Diag(Loc, diag::ext_gnu_missing_equal_designator);
    else if (Desig.getNumDesignators() > 0)
      P.Diag(Loc, diag::err_expected_equal_designator);
  }
  
  /// ParseInitializerWithPotentialDesignator - Parse the 'initializer' production
  /// checking to see if the token stream starts with a designator.
  ///
  ///       designation:
  ///         designator-list '='
  /// [GNU]   array-designator
  /// [GNU]   identifier ':'
  ///
  ///       designator-list:
  ///         designator
  ///         designator-list designator
  ///
  ///       designator:
  ///         array-designator
  ///         '.' identifier
  ///
  ///       array-designator:
  ///         '[' constant-expression ']'
  /// [GNU]   '[' constant-expression '...' constant-expression ']'
  ///
  /// NOTE: [OBC] allows '[ objc-receiver objc-message-args ]' as an
  /// initializer (because it is an expression).  We need to consider this case
  /// when parsing array designators.
  ///
  ExprResult Parser::ParseInitializerWithPotentialDesignator() {
  
    // If this is the old-style GNU extension:
    //   designation ::= identifier ':'
    // Handle it as a field designator.  Otherwise, this must be the start of a
    // normal expression.
    if (Tok.is(tok::identifier)) {
      const IdentifierInfo *FieldName = Tok.getIdentifierInfo();
  
      llvm::SmallString<256> NewSyntax;
      llvm::raw_svector_ostream(NewSyntax) << '.' << FieldName->getName()
                                           << " = ";
  
      SourceLocation NameLoc = ConsumeToken(); // Eat the identifier.
  
      assert(Tok.is(tok::colon) && "MayBeDesignationStart not working properly!");
      SourceLocation ColonLoc = ConsumeToken();
  
      Diag(Tok, diag::ext_gnu_old_style_field_designator)
        << FixItHint::CreateReplacement(SourceRange(NameLoc, ColonLoc),
                                        NewSyntax.str());
  
      Designation D;
      D.AddDesignator(Designator::getField(FieldName, SourceLocation(), NameLoc));
      return Actions.ActOnDesignatedInitializer(D, ColonLoc, true,
                                                ParseInitializer());
    }
  
    // Desig - This is initialized when we see our first designator.  We may have
    // an objc message send with no designator, so we don't want to create this
    // eagerly.
    Designation Desig;
  
    // Parse each designator in the designator list until we find an initializer.
    while (Tok.is(tok::period) || Tok.is(tok::l_square)) {
      if (Tok.is(tok::period)) {
        // designator: '.' identifier
        SourceLocation DotLoc = ConsumeToken();
  
        if (Tok.isNot(tok::identifier)) {
          Diag(Tok.getLocation(), diag::err_expected_field_designator);
          return ExprError();
        }
  
        Desig.AddDesignator(Designator::getField(Tok.getIdentifierInfo(), DotLoc,
                                                 Tok.getLocation()));
        ConsumeToken(); // Eat the identifier.
        continue;
      }
  
      // We must have either an array designator now or an objc message send.
      assert(Tok.is(tok::l_square) && "Unexpected token!");
  
      // Handle the two forms of array designator:
      //   array-designator: '[' constant-expression ']'
      //   array-designator: '[' constant-expression '...' constant-expression ']'
      //
      // Also, we have to handle the case where the expression after the
      // designator an an objc message send: '[' objc-message-expr ']'.
      // Interesting cases are:
      //   [foo bar]         -> objc message send
      //   [foo]             -> array designator
      //   [foo ... bar]     -> array designator
      //   [4][foo bar]      -> obsolete GNU designation with objc message send.
      //
      InMessageExpressionRAIIObject InMessage(*this, true);
      
      SourceLocation StartLoc = ConsumeBracket();
      ExprResult Idx;
  
      // If Objective-C is enabled and this is a typename (class message
      // send) or send to 'super', parse this as a message send
      // expression.  We handle C++ and C separately, since C++ requires
      // much more complicated parsing.
      if  (getLang().ObjC1 && getLang().CPlusPlus) {
        // Send to 'super'.
        if (Tok.is(tok::identifier) && Tok.getIdentifierInfo() == Ident_super &&
            NextToken().isNot(tok::period) && 
            getCurScope()->isInObjcMethodScope()) {
          CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
          return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
                                                             ConsumeToken(),
                                                             ParsedType(), 
                                                             0);
        }
  
        // Parse the receiver, which is either a type or an expression.
        bool IsExpr;
        void *TypeOrExpr;
        if (ParseObjCXXMessageReceiver(IsExpr, TypeOrExpr)) {
          SkipUntil(tok::r_square);
          return ExprError();
        }
        
        // If the receiver was a type, we have a class message; parse
        // the rest of it.
        if (!IsExpr) {
          CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
          return ParseAssignmentExprWithObjCMessageExprStart(StartLoc, 
                                                             SourceLocation(), 
                                     ParsedType::getFromOpaquePtr(TypeOrExpr),
                                                             0);
        }
  
        // If the receiver was an expression, we still don't know
        // whether we have a message send or an array designator; just
        // adopt the expression for further analysis below.
        // FIXME: potentially-potentially evaluated expression above?
        Idx = ExprResult(static_cast<Expr*>(TypeOrExpr));
      } else if (getLang().ObjC1 && Tok.is(tok::identifier)) {
        IdentifierInfo *II = Tok.getIdentifierInfo();
        SourceLocation IILoc = Tok.getLocation();
        ParsedType ReceiverType;
        // Three cases. This is a message send to a type: [type foo]
        // This is a message send to super:  [super foo]
        // This is a message sent to an expr:  [super.bar foo]
        switch (Sema::ObjCMessageKind Kind
                  = Actions.getObjCMessageKind(getCurScope(), II, IILoc, 
                                               II == Ident_super,
                                               NextToken().is(tok::period),
                                               ReceiverType)) {
        case Sema::ObjCSuperMessage:
        case Sema::ObjCClassMessage:
          CheckArrayDesignatorSyntax(*this, StartLoc, Desig);
          if (Kind == Sema::ObjCSuperMessage)
            return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
                                                               ConsumeToken(),
                                                               ParsedType(),
                                                               0);
          ConsumeToken(); // the identifier
          if (!ReceiverType) {
            SkipUntil(tok::r_square);
            return ExprError();
          }
  
          return ParseAssignmentExprWithObjCMessageExprStart(StartLoc, 
                                                             SourceLocation(), 
                                                             ReceiverType, 
                                                             0);
  
        case Sema::ObjCInstanceMessage:
          // Fall through; we'll just parse the expression and
          // (possibly) treat this like an Objective-C message send
          // later.
          break;
        }
      }
  
      // Parse the index expression, if we haven't already gotten one
      // above (which can only happen in Objective-C++).
      // Note that we parse this as an assignment expression, not a constant
      // expression (allowing *=, =, etc) to handle the objc case.  Sema needs
      // to validate that the expression is a constant.
      // FIXME: We also need to tell Sema that we're in a
      // potentially-potentially evaluated context.
      if (!Idx.get()) {
        Idx = ParseAssignmentExpression();
        if (Idx.isInvalid()) {
          SkipUntil(tok::r_square);
          return move(Idx);
        }
      }
  
      // Given an expression, we could either have a designator (if the next
      // tokens are '...' or ']' or an objc message send.  If this is an objc
      // message send, handle it now.  An objc-message send is the start of
      // an assignment-expression production.
      if (getLang().ObjC1 && Tok.isNot(tok::ellipsis) &&
          Tok.isNot(tok::r_square)) {
        CheckArrayDesignatorSyntax(*this, Tok.getLocation(), Desig);
        return ParseAssignmentExprWithObjCMessageExprStart(StartLoc,
                                                           SourceLocation(),
                                                           ParsedType(),
                                                           Idx.take());
      }
  
      // If this is a normal array designator, remember it.
      if (Tok.isNot(tok::ellipsis)) {
        Desig.AddDesignator(Designator::getArray(Idx.release(), StartLoc));
      } else {
        // Handle the gnu array range extension.
        Diag(Tok, diag::ext_gnu_array_range);
        SourceLocation EllipsisLoc = ConsumeToken();
  
        ExprResult RHS(ParseConstantExpression());
        if (RHS.isInvalid()) {
          SkipUntil(tok::r_square);
          return move(RHS);
        }
        Desig.AddDesignator(Designator::getArrayRange(Idx.release(),
                                                      RHS.release(),
                                                      StartLoc, EllipsisLoc));
      }
  
      SourceLocation EndLoc = MatchRHSPunctuation(tok::r_square, StartLoc);
      Desig.getDesignator(Desig.getNumDesignators() - 1).setRBracketLoc(EndLoc);
    }
  
    // Okay, we're done with the designator sequence.  We know that there must be
    // at least one designator, because the only case we can get into this method
    // without a designator is when we have an objc message send.  That case is
    // handled and returned from above.
    assert(!Desig.empty() && "Designator is empty?");
  
    // Handle a normal designator sequence end, which is an equal.
    if (Tok.is(tok::equal)) {
      SourceLocation EqualLoc = ConsumeToken();
      return Actions.ActOnDesignatedInitializer(Desig, EqualLoc, false,
                                                ParseInitializer());
    }
  
    // We read some number of designators and found something that isn't an = or
    // an initializer.  If we have exactly one array designator, this
    // is the GNU 'designation: array-designator' extension.  Otherwise, it is a
    // parse error.
    if (Desig.getNumDesignators() == 1 &&
        (Desig.getDesignator(0).isArrayDesignator() ||
         Desig.getDesignator(0).isArrayRangeDesignator())) {
      Diag(Tok, diag::ext_gnu_missing_equal_designator)
        << FixItHint::CreateInsertion(Tok.getLocation(), "= ");
      return Actions.ActOnDesignatedInitializer(Desig, Tok.getLocation(),
                                                true, ParseInitializer());
    }
  
    Diag(Tok, diag::err_expected_equal_designator);
    return ExprError();
  }
  
  
  /// ParseBraceInitializer - Called when parsing an initializer that has a
  /// leading open brace.
  ///
  ///       initializer: [C99 6.7.8]
  ///         '{' initializer-list '}'
  ///         '{' initializer-list ',' '}'
  /// [GNU]   '{' '}'
  ///
  ///       initializer-list:
  ///         designation[opt] initializer ...[opt]
  ///         initializer-list ',' designation[opt] initializer ...[opt]
  ///
  ExprResult Parser::ParseBraceInitializer() {
    InMessageExpressionRAIIObject InMessage(*this, false);
    
    SourceLocation LBraceLoc = ConsumeBrace();
  
    /// InitExprs - This is the actual list of expressions contained in the
    /// initializer.
    ExprVector InitExprs(Actions);
  
    if (Tok.is(tok::r_brace)) {
      // Empty initializers are a C++ feature and a GNU extension to C.
      if (!getLang().CPlusPlus)
        Diag(LBraceLoc, diag::ext_gnu_empty_initializer);
      // Match the '}'.
      return Actions.ActOnInitList(LBraceLoc, MultiExprArg(Actions),
                                   ConsumeBrace());
    }
  
    bool InitExprsOk = true;
  
    while (1) {
      // Parse: designation[opt] initializer
  
      // If we know that this cannot be a designation, just parse the nested
      // initializer directly.
      ExprResult SubElt;
      if (MayBeDesignationStart(Tok.getKind(), PP))
        SubElt = ParseInitializerWithPotentialDesignator();
      else
        SubElt = ParseInitializer();
  
      if (Tok.is(tok::ellipsis))
        SubElt = Actions.ActOnPackExpansion(SubElt.get(), ConsumeToken());
      
      // If we couldn't parse the subelement, bail out.
      if (!SubElt.isInvalid()) {
        InitExprs.push_back(SubElt.release());
      } else {
        InitExprsOk = false;
  
        // We have two ways to try to recover from this error: if the code looks
        // gramatically ok (i.e. we have a comma coming up) try to continue
        // parsing the rest of the initializer.  This allows us to emit
        // diagnostics for later elements that we find.  If we don't see a comma,
        // assume there is a parse error, and just skip to recover.
        // FIXME: This comment doesn't sound right. If there is a r_brace
        // immediately, it can't be an error, since there is no other way of
        // leaving this loop except through this if.
        if (Tok.isNot(tok::comma)) {
          SkipUntil(tok::r_brace, false, true);
          break;
        }
      }
  
      // If we don't have a comma continued list, we're done.
      if (Tok.isNot(tok::comma)) break;
  
      // TODO: save comma locations if some client cares.
      ConsumeToken();
  
      // Handle trailing comma.
      if (Tok.is(tok::r_brace)) break;
    }
    if (InitExprsOk && Tok.is(tok::r_brace))
      return Actions.ActOnInitList(LBraceLoc, move_arg(InitExprs),
                                   ConsumeBrace());
  
    // Match the '}'.
    MatchRHSPunctuation(tok::r_brace, LBraceLoc);
    return ExprError(); // an error occurred.
  }
  
  