ReturnStatement.java

/*******************************************************************************
 * Copyright (c) 2000, 2011 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.wst.jsdt.internal.compiler.ast;

import org.eclipse.wst.jsdt.core.ast.IASTNode;
import org.eclipse.wst.jsdt.core.ast.IExpression;
import org.eclipse.wst.jsdt.core.ast.IReturnStatement;
import org.eclipse.wst.jsdt.internal.compiler.ASTVisitor;
import org.eclipse.wst.jsdt.internal.compiler.flow.FlowContext;
import org.eclipse.wst.jsdt.internal.compiler.flow.FlowInfo;
import org.eclipse.wst.jsdt.internal.compiler.flow.InitializationFlowContext;
import org.eclipse.wst.jsdt.internal.compiler.flow.InsideSubRoutineFlowContext;
import org.eclipse.wst.jsdt.internal.compiler.impl.Constant;
import org.eclipse.wst.jsdt.internal.compiler.lookup.BlockScope;
import org.eclipse.wst.jsdt.internal.compiler.lookup.LocalVariableBinding;
import org.eclipse.wst.jsdt.internal.compiler.lookup.MethodBinding;
import org.eclipse.wst.jsdt.internal.compiler.lookup.MethodScope;
import org.eclipse.wst.jsdt.internal.compiler.lookup.TypeBinding;

public class ReturnStatement extends Statement implements IReturnStatement {

	public Expression expression;
	public SubRoutineStatement[] subroutines;
	public LocalVariableBinding saveValueVariable;
	public int initStateIndex = -1;

public ReturnStatement(Expression expression, int sourceStart, int sourceEnd) {
	this.sourceStart = sourceStart;
	this.sourceEnd = sourceEnd;
	this.expression = expression ;
}

public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
	if (this.expression != null) {
		flowInfo = this.expression.analyseCode(currentScope, flowContext, flowInfo);
	}

	// compute the return sequence (running the finally blocks)
	FlowContext traversedContext = flowContext;
	int subCount = 0;
	boolean saveValueNeeded = false;
	boolean hasValueToSave = this.expression != null
						&& this.expression.constant == Constant.NotAConstant
						&& !(this.expression instanceof NullLiteral);
	do {
		SubRoutineStatement sub;
		if ((sub = traversedContext.subroutine()) != null) {
			if (this.subroutines == null){
				this.subroutines = new SubRoutineStatement[5];
			}
			if (subCount == this.subroutines.length) {
				System.arraycopy(this.subroutines, 0, (this.subroutines = new SubRoutineStatement[subCount*2]), 0, subCount); // grow
			}
			this.subroutines[subCount++] = sub;
			if (sub.isSubRoutineEscaping()) {
				saveValueNeeded = false;
				this.bits |= ASTNode.IsAnySubRoutineEscaping;
				break;
			}
		}
		traversedContext.recordReturnFrom(flowInfo.unconditionalInits());

		if (traversedContext instanceof InsideSubRoutineFlowContext) {
			ASTNode node = traversedContext.associatedNode;
			if (node instanceof TryStatement) {
				TryStatement tryStatement = (TryStatement) node;
				flowInfo.addInitializationsFrom(tryStatement.subRoutineInits); // collect inits
				if (hasValueToSave) {
					if (this.saveValueVariable == null){ // closest subroutine secret variable is used
						prepareSaveValueLocation(tryStatement);
					}
					saveValueNeeded = true;
				}
			}
		} else if (traversedContext instanceof InitializationFlowContext) {
				currentScope.problemReporter().cannotReturnOutsideFunction(this);
				return FlowInfo.DEAD_END;
		}
	} while ((traversedContext = traversedContext.parent) != null);

	// resize subroutines
	if ((this.subroutines != null) && (subCount != this.subroutines.length)) {
		System.arraycopy(this.subroutines, 0, (this.subroutines = new SubRoutineStatement[subCount]), 0, subCount);
	}

	// secret local variable for return value (note that this can only occur in a real method)
	if (saveValueNeeded) {
		if (this.saveValueVariable != null) {
			this.saveValueVariable.useFlag = LocalVariableBinding.USED;
		}
	} else {
		this.saveValueVariable = null;
		if ( this.expression != null && this.expression.resolvedType == TypeBinding.BOOLEAN) {
			this.expression.bits |= ASTNode.IsReturnedValue;
		}
	}
	return FlowInfo.DEAD_END;
}

public boolean needValue() {
	return this.saveValueVariable != null
	|| ((this.bits & ASTNode.IsAnySubRoutineEscaping) == 0);
}

public void prepareSaveValueLocation(TryStatement targetTryStatement){
	this.saveValueVariable = targetTryStatement.secretReturnValue;
}

public StringBuffer printStatement(int tab, StringBuffer output){
	printIndent(tab, output).append("return "); //$NON-NLS-1$
	if (this.expression != null )
		this.expression.printExpression(0, output) ;
	return output.append(';');
}

public void resolve(BlockScope scope) {
	MethodScope methodScope = scope.methodScope();

	if(methodScope==null) {
		/* return statement outside of a method */
		scope.problemReporter().cannotReturnOutsideFunction(this);
		return;
	}

	MethodBinding methodBinding = null;
	TypeBinding methodType =
		(methodScope.referenceContext instanceof AbstractMethodDeclaration)
			? ((methodBinding = ((AbstractMethodDeclaration) methodScope.referenceContext).binding) == null
				? null
				: methodBinding.returnType)
			: TypeBinding.ANY;
	TypeBinding expressionType;
	if (this.expression == null) {
		if (methodType != null && !methodType.isAnyType()) scope.problemReporter().shouldReturn(methodType, this);
		return;
	}
	this.expression.setExpectedType(methodType); // needed in case of generic method invocation
	if ((expressionType = this.expression.resolveType(scope)) == null) return;
	if (methodType == null)
		return;

	if (methodType != expressionType) // must call before computeConversion() and typeMismatchError()
		scope.compilationUnitScope().recordTypeConversion(methodType, expressionType);
	if (this.expression.isConstantValueOfTypeAssignableToType(expressionType, methodType)
			|| expressionType.isCompatibleWith(methodType)) {

		return;
	}
	if(methodBinding != null && !methodBinding.isConstructor())
		scope.problemReporter().typeMismatchError(expressionType, methodType, this.expression);
}

public void traverse(ASTVisitor visitor, BlockScope scope) {
	if (visitor.visit(this, scope)) {
		if (this.expression != null)
			this.expression.traverse(visitor, scope);
	}
	visitor.endVisit(this, scope);
}
public int getASTType() {
	return IASTNode.RETURN_STATEMENT;

}

public IExpression getExpression() {
	return this.expression;
}
}