path: root/lib/Parse/ParseTemplate.cpp

//===--- ParseTemplate.cpp - Template 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 parsing of C++ templates.
//
//===----------------------------------------------------------------------===//

#include "clang/Parse/Parser.h"
#include "clang/Parse/ParseDiagnostic.h"
#include "clang/Parse/DeclSpec.h"
#include "clang/Parse/Scope.h"

using namespace clang;

/// ParseTemplateDeclaration - Parse a template declaration, which includes 
/// the template parameter list and either a function of class declaration.
///
///       template-declaration: [C++ temp]
///         'export'[opt] 'template' '<' template-parameter-list '>' declaration
Parser::DeclTy *Parser::ParseTemplateDeclaration(unsigned Context) {
  assert((Tok.is(tok::kw_export) || Tok.is(tok::kw_template)) && 
	 "Token does not start a template declaration.");
  
  // Enter template-parameter scope.
  ParseScope TemplateParmScope(this, Scope::TemplateParamScope);

  // Parse multiple levels of template headers within this template
  // parameter scope, e.g.,
  //
  //   template<typename T>
  //     template<typename U>
  //       class A<T>::B { ... };
  //
  // We parse multiple levels non-recursively so that we can build a
  // single data structure containing all of the template parameter
  // lists, and easily differentiate between the case above and:
  //
  //   template<typename T>
  //   class A {
  //     template<typename U> class B;
  //   };
  //
  // In the first case, the action for declaring A<T>::B receives
  // both template parameter lists. In the second case, the action for
  // defining A<T>::B receives just the inner template parameter list
  // (and retrieves the outer template parameter list from its
  // context).
  TemplateParameterLists ParamLists;
  do {
    // Consume the 'export', if any.
    SourceLocation ExportLoc;
    if (Tok.is(tok::kw_export)) {
      ExportLoc = ConsumeToken();
    }

    // Consume the 'template', which should be here.
    SourceLocation TemplateLoc;
    if (Tok.is(tok::kw_template)) {
      TemplateLoc = ConsumeToken();
    } else {
      Diag(Tok.getLocation(), diag::err_expected_template);
      return 0;
    }
  
    // Parse the '<' template-parameter-list '>'
    SourceLocation LAngleLoc, RAngleLoc;
    TemplateParameterList TemplateParams;
    ParseTemplateParameters(ParamLists.size(), TemplateParams, LAngleLoc, 
                            RAngleLoc);

    ParamLists.push_back(
      Actions.ActOnTemplateParameterList(ParamLists.size(), ExportLoc, 
                                         TemplateLoc, LAngleLoc, 
                                         &TemplateParams[0],
                                         TemplateParams.size(), RAngleLoc));
  } while (Tok.is(tok::kw_export) || Tok.is(tok::kw_template));

  // Parse the actual template declaration.
  DeclTy *TemplateDecl = ParseDeclarationOrFunctionDefinition(&ParamLists);

  return TemplateDecl;
}

/// ParseTemplateParameters - Parses a template-parameter-list enclosed in
/// angle brackets. Depth is the depth of this
/// template-parameter-list, which is the number of template headers
/// directly enclosing this template header. TemplateParams is the
/// current list of template parameters we're building. The template
/// parameter we parse will be added to this list. LAngleLoc and
/// RAngleLoc will receive the positions of the '<' and '>',
/// respectively, that enclose this template parameter list.
bool Parser::ParseTemplateParameters(unsigned Depth,
                                     TemplateParameterList &TemplateParams,
                                     SourceLocation &LAngleLoc,
                                     SourceLocation &RAngleLoc) {
  // Get the template parameter list.
  if(!Tok.is(tok::less)) {
    Diag(Tok.getLocation(), diag::err_expected_less_after) << "template";
    return false;
  }
  LAngleLoc = ConsumeToken();
  
  // Try to parse the template parameter list.
  if (Tok.is(tok::greater))
    RAngleLoc = ConsumeToken();
  else if(ParseTemplateParameterList(Depth, TemplateParams)) {
    if(!Tok.is(tok::greater)) {
      Diag(Tok.getLocation(), diag::err_expected_greater);
      return false;
    }
    RAngleLoc = ConsumeToken();
  }
  return true;
}

/// ParseTemplateParameterList - Parse a template parameter list. If
/// the parsing fails badly (i.e., closing bracket was left out), this
/// will try to put the token stream in a reasonable position (closing
/// a statement, etc.) and return false. 
///
///       template-parameter-list:    [C++ temp]
///         template-parameter
///         template-parameter-list ',' template-parameter
bool 
Parser::ParseTemplateParameterList(unsigned Depth,
                                   TemplateParameterList &TemplateParams) {
  while(1) {
    if (DeclTy* TmpParam 
          = ParseTemplateParameter(Depth, TemplateParams.size())) {
      TemplateParams.push_back(TmpParam);
    } else {
      // If we failed to parse a template parameter, skip until we find
      // a comma or closing brace.
      SkipUntil(tok::comma, tok::greater, true, true);
    }
    
    // Did we find a comma or the end of the template parmeter list?
    if(Tok.is(tok::comma)) {
      ConsumeToken();
    } else if(Tok.is(tok::greater)) {
      // Don't consume this... that's done by template parser.
      break;
    } else {
      // Somebody probably forgot to close the template. Skip ahead and
      // try to get out of the expression. This error is currently
      // subsumed by whatever goes on in ParseTemplateParameter.
      // TODO: This could match >>, and it would be nice to avoid those
      // silly errors with template <vec<T>>.
      // Diag(Tok.getLocation(), diag::err_expected_comma_greater);
      SkipUntil(tok::greater, true, true);
      return false;
    }
  }
  return true;
}

/// ParseTemplateParameter - Parse a template-parameter (C++ [temp.param]).
///
///       template-parameter: [C++ temp.param]
///         type-parameter
///         parameter-declaration
///
///       type-parameter: (see below)
///         'class' identifier[opt]
///         'class' identifier[opt] '=' type-id
///         'typename' identifier[opt]
///         'typename' identifier[opt] '=' type-id
///         'template' '<' template-parameter-list '>' 'class' identifier[opt]
///         'template' '<' template-parameter-list '>' 'class' identifier[opt] = id-expression
Parser::DeclTy *
Parser::ParseTemplateParameter(unsigned Depth, unsigned Position) {
  if(Tok.is(tok::kw_class) ||
     (Tok.is(tok::kw_typename) && 
         // FIXME: Next token has not been annotated!
	 NextToken().isNot(tok::annot_typename))) {
    return ParseTypeParameter(Depth, Position);
  }
  
  if(Tok.is(tok::kw_template))
    return ParseTemplateTemplateParameter(Depth, Position);

  // If it's none of the above, then it must be a parameter declaration.
  // NOTE: This will pick up errors in the closure of the template parameter
  // list (e.g., template < ; Check here to implement >> style closures.
  return ParseNonTypeTemplateParameter(Depth, Position);
}

/// ParseTypeParameter - Parse a template type parameter (C++ [temp.param]).
/// Other kinds of template parameters are parsed in
/// ParseTemplateTemplateParameter and ParseNonTypeTemplateParameter.
///
///       type-parameter:     [C++ temp.param]
///         'class' identifier[opt]
///         'class' identifier[opt] '=' type-id
///         'typename' identifier[opt]
///         'typename' identifier[opt] '=' type-id
Parser::DeclTy *Parser::ParseTypeParameter(unsigned Depth, unsigned Position) {
  assert((Tok.is(tok::kw_class) || Tok.is(tok::kw_typename)) &&
	 "A type-parameter starts with 'class' or 'typename'");

  // Consume the 'class' or 'typename' keyword.
  bool TypenameKeyword = Tok.is(tok::kw_typename);
  SourceLocation KeyLoc = ConsumeToken();

  // Grab the template parameter name (if given)
  SourceLocation NameLoc;
  IdentifierInfo* ParamName = 0;
  if(Tok.is(tok::identifier)) {
    ParamName = Tok.getIdentifierInfo();
    NameLoc = ConsumeToken();
  } else if(Tok.is(tok::equal) || Tok.is(tok::comma) ||
	    Tok.is(tok::greater)) {
    // Unnamed template parameter. Don't have to do anything here, just
    // don't consume this token.
  } else {
    Diag(Tok.getLocation(), diag::err_expected_ident);
    return 0;
  }
  
  DeclTy *TypeParam = Actions.ActOnTypeParameter(CurScope, TypenameKeyword, 
						 KeyLoc, ParamName, NameLoc,
                                                 Depth, Position);

  // Grab a default type id (if given).
  if(Tok.is(tok::equal)) {
    SourceLocation EqualLoc = ConsumeToken();
    if (TypeTy *DefaultType = ParseTypeName())
      Actions.ActOnTypeParameterDefault(TypeParam, DefaultType);
  }
  
  return TypeParam;
}

/// ParseTemplateTemplateParameter - Handle the parsing of template
/// template parameters. 
///
///       type-parameter:    [C++ temp.param]
///         'template' '<' template-parameter-list '>' 'class' identifier[opt]
///         'template' '<' template-parameter-list '>' 'class' identifier[opt] = id-expression
Parser::DeclTy * 
Parser::ParseTemplateTemplateParameter(unsigned Depth, unsigned Position) {
  assert(Tok.is(tok::kw_template) && "Expected 'template' keyword");

  // Handle the template <...> part.
  SourceLocation TemplateLoc = ConsumeToken();
  TemplateParameterList TemplateParams; 
  SourceLocation LParenLoc, RParenLoc;
  if(!ParseTemplateParameters(Depth+1, TemplateParams, LParenLoc,
                              RParenLoc)) {
    return 0;
  }

  // Generate a meaningful error if the user forgot to put class before the
  // identifier, comma, or greater.
  if(!Tok.is(tok::kw_class)) {
    Diag(Tok.getLocation(), diag::err_expected_class_before) 
      << PP.getSpelling(Tok);
    return 0;
  }
  SourceLocation ClassLoc = ConsumeToken();

  // Get the identifier, if given.
  IdentifierInfo* ident = 0;
  if(Tok.is(tok::identifier)) {
    ident = Tok.getIdentifierInfo();
    ConsumeToken();
  } else if(Tok.is(tok::equal) || Tok.is(tok::comma) || Tok.is(tok::greater)) {
    // Unnamed template parameter. Don't have to do anything here, just
    // don't consume this token.
  } else {
    Diag(Tok.getLocation(), diag::err_expected_ident);
    return 0