groovy/modules/classic/src/java/org/codehaus/groovy/syntax/parser/ExpressionSupport.java

/*
 $Id$

 Copyright 2003 (C) James Strachan and Bob Mcwhirter. All Rights Reserved.

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package org.codehaus.groovy.syntax.parser;

import org.codehaus.groovy.syntax.*;



/**
 *  A helper for the expression parsing system that provides in-depth
 *  analysis of <code>CSTNode</code>s.
 *
 *  @author <a href="mailto:cpoirier@dreaming.org">Chris Poirier</a>
 */

public class ExpressionSupport
{

  //---------------------------------------------------------------------------
  // EXPRESSION IDENTIFICATION


   /**
    *  Returns true if the node is a complete expression (something that has
    *  a value).
    */

    public static boolean isAnExpression( CSTNode node, boolean unknownReturns )
    {
        if( node.isA(Types.UNKNOWN) )
        {
            return unknownReturns;
        }

        return node.isAnExpression();
    }



   /**
    *  A synonym for <code>isAnExpression( node, false )</code>.
    */

    public static boolean isAnExpression( CSTNode node )
    {
        return isAnExpression( node, false );
    }




  //---------------------------------------------------------------------------
  // OPERATOR IDENTIFICATION


   /**
    *  Returns true if the node is an operator and not an expression (see
    *  above).
    */

    public static boolean isAnOperator( CSTNode node, boolean unknownReturns )
    {
        if( node.isA(Types.UNKNOWN) )
        {
            return unknownReturns;
        }

        return !node.isAnExpression();
    }



   /**
    *  A synonym for <code>isAnOperator(node, false)</code>.
    */

    public static boolean isAnOperator( CSTNode node )
    {
        return isAnOperator( node, false );
    }




  //---------------------------------------------------------------------------
  // VARIABLE IDENTIFICATION


   /**
    *  Returns true if the node might be a variable.
    */

    public static boolean isAVariable( CSTNode node )
    {
        switch( node.getMeaning() )
        {
            case Types.LEFT_SQUARE_BRACKET:
                if( node.isAnExpression() )
                {
                   return isAVariable( node.get(1) );
                }
                break;

            case Types.DOT:
            case Types.NAVIGATE:
            {
                if( node.isAnExpression() && node.get(2).getMeaning() == Types.IDENTIFIER )
                {
                    return true;
                }
                break;
            }

            case Types.IDENTIFIER:
            {
                return true;
            }
        }

        return false;
    }




  //---------------------------------------------------------------------------
  // METHOD IDENTIFICATION


   /**
    *  Returns true if the node might be a method.
    */

    public static boolean isInvokable( CSTNode node )
    {
        switch( node.getMeaning() )
        {
            case Types.SYNTH_CLOSURE:
            case Types.SYNTH_METHOD_CALL:
            case Types.KEYWORD_SUPER:
            case Types.KEYWORD_THIS:
                return true;

            default:
                return isAVariable(node);
        }
    }




  //---------------------------------------------------------------------------
  // ASSIGNMENT TARGET IDENTIFICATION


   /**
    *  Returns true if the node is a modifiable expression (ie. something that
    *  can be the target of an assignment).  Note that this determination is
    *  approximate: false negatives won't happen, but false positives are
    *  distinctly possible, and must be resolved in later phases.
    */

    public static boolean isAModifiableExpression( CSTNode node, boolean unknownReturns )
    {
        if( isAnExpression(node, unknownReturns) )
        {
            if( isAVariable(node) )
            {
                return true;
            }

            else if( node.getMeaning() == Types.SYNTH_LIST )
            {
                boolean is = true;
                for( int i = 1; i < node.size(); i++ )
                {
                    if( !isAModifiableExpression(node.get(i), unknownReturns) )
                    {
                        is = false;
                        break;
                    }
                }
                return is;
            }

        }

        return false;
    }



   /**
    *  A synonym for <code>isAModifiableExpression( node, false )</code>.
    */

    public static boolean isAModifiableExpression( CSTNode node )
    {
        return isAModifiableExpression( node, false );
    }




  //---------------------------------------------------------------------------
  // TYPE OPERATIONS IDENTIFICATION


   /**
    *  Returns true if the node is potentially a cast operator.
    */

    public static boolean isPotentialCastOperator( CSTNode node )
    {
        if( node.isA(Types.LEFT_PARENTHESIS) && node.isAnExpression() )
        {
            return isAPotentialTypeName( node.get(1), false );
        }

        return false;
    }



   /**
    *  Returns true if the node is potentially a type name.
    */

    public static boolean isAPotentialTypeName( CSTNode node, boolean allowVoid )
    {
        if( node.isA(allowVoid ? Types.TYPE_NAME : Types.CREATABLE_TYPE_NAME) )
        {
            return true;
        }
        else if( node.isA(Types.DOT) && node.isAnExpression() )
        {
            return isAPotentialTypeName(node.get(2), allowVoid) && isAPotentialTypeName(node.get(1), allowVoid);
        }
        else if( node.isA(Types.LEFT_SQUARE_BRACKET) && node.isAnExpression() && node.size() == 2 )
        {
            return isAPotentialTypeName(node.get(1), allowVoid );
        }

        return false;
    }




}