astletexpression.java

UML设计测试工具

/*
 * USE - UML based specification environment
 * Copyright (C) 1999-2004 Mark Richters, University of Bremen
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* $ProjectHeader: use 2-3-0-release.1 Mon, 12 Sep 2005 20:18:33 +0200 green $ */

package org.tzi.use.parser.ocl;

import org.tzi.use.parser.Context;
import org.tzi.use.parser.MyToken;
import org.tzi.use.parser.SemanticException;
import org.tzi.use.parser.Symtable;
import org.tzi.use.uml.ocl.expr.ExpInvalidException;
import org.tzi.use.uml.ocl.expr.ExpLet;
import org.tzi.use.uml.ocl.expr.Expression;
import org.tzi.use.uml.ocl.type.Type;

/**
 * Node of the abstract syntax tree constructed by the parser.
 *
 * @version     $ProjectVersion: 2-3-0-release.1 $
 * @author  Mark Richters
 */
public class ASTLetExpression extends ASTExpression {
    private MyToken fVarToken;
    private ASTType fVarType;   // optional: may be null
    private ASTExpression fVarExpr;
    private ASTExpression fInExpr;

    public ASTLetExpression(MyToken varToken, 
                            ASTType type,
                            ASTExpression varExpr) {
        fVarToken = varToken;
        fVarType = type;
        fVarExpr = varExpr;
    }

    public void setInExpr(ASTExpression inExpr) {
        fInExpr = inExpr;
    }   

    public Expression gen(Context ctx) throws SemanticException {
        Expression res = null;
        Expression varExpr = fVarExpr.gen(ctx);
        Type varType;

        if (fVarType == null )
            varType = varExpr.type();
        else {
            varType = fVarType.gen(ctx);
            if (! varExpr.type().isSubtypeOf(varType) )
                throw new SemanticException(fVarExpr.getStartToken(),
                                            "Expected expression of type `" +
                                            varType + "', found `" +
                                            varExpr.type() + "'.");
        }

        Symtable vars = ctx.varTable();
        vars.enterScope();
        vars.add(fVarToken, varType);
        Expression inExpr = fInExpr.gen(ctx);
        vars.exitScope();

        try {
            res = new ExpLet(fVarToken.getText(),
                             varType,
                             varExpr,
                             inExpr);
        } catch (ExpInvalidException ex) {
            throw new SemanticException(fVarToken, ex);
        }

        return res;
    }
}