Copyright (c) 2000, 2015 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
    Stephan Herrmann - Contribution for
							bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
							bug 392862 - [1.8][compiler][null] Evaluate null annotations on array types
							bug 383368 - [compiler][null] syntactic null analysis for field references
							bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Stephan Herrmann - Contribution for
 *								bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
 *								bug 392862 - [1.8][compiler][null] Evaluate null annotations on array types
 *								bug 383368 - [compiler][null] syntactic null analysis for field references
 *								bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;

import org.eclipse.jdt.internal.compiler.ASTVisitor;
import org.eclipse.jdt.internal.compiler.codegen.CodeStream;
import org.eclipse.jdt.internal.compiler.flow.FlowContext;
import org.eclipse.jdt.internal.compiler.flow.FlowInfo;
import org.eclipse.jdt.internal.compiler.impl.Constant;
import org.eclipse.jdt.internal.compiler.lookup.ArrayBinding;
import org.eclipse.jdt.internal.compiler.lookup.BlockScope;
import org.eclipse.jdt.internal.compiler.lookup.TagBits;
import org.eclipse.jdt.internal.compiler.lookup.TypeBinding;
import org.eclipse.jdt.internal.compiler.lookup.TypeIds;

public class ArrayReference extends Reference {

	public Expression receiver;
	public Expression position;

public ArrayReference(Expression rec, Expression pos) {
	this.receiver = rec;
	this.position = pos;
	this.sourceStart = rec.sourceStart;
}

@Override
public FlowInfo analyseAssignment(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo, Assignment assignment, boolean compoundAssignment) {
	// TODO (maxime) optimization: unconditionalInits is applied to all existing calls
	// account for potential ArrayIndexOutOfBoundsException:
	flowContext.recordAbruptExit();
	if (assignment.expression == null) {
		return analyseCode(currentScope, flowContext, flowInfo);
	}
	flowInfo = assignment
		.expression
		.analyseCode(
			currentScope,
			flowContext,
			analyseCode(currentScope, flowContext, flowInfo).unconditionalInits());
	if (currentScope.environment().usesNullTypeAnnotations()) {
		checkAgainstNullTypeAnnotation(currentScope, this.resolvedType, assignment.expression, flowContext, flowInfo);
	}
	return flowInfo;
}

@Override
public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
	flowInfo = this.receiver.analyseCode(currentScope, flowContext, flowInfo);
	this.receiver.checkNPE(currentScope, flowContext, flowInfo, 1);
	flowInfo = this.position.analyseCode(currentScope, flowContext, flowInfo);
	this.position.checkNPEbyUnboxing(currentScope, flowContext, flowInfo);
	// account for potential ArrayIndexOutOfBoundsException:
	flowContext.recordAbruptExit();
	return flowInfo;
}

@Override
public boolean checkNPE(BlockScope scope, FlowContext flowContext, FlowInfo flowInfo, int ttlForFieldCheck) {
	if ((this.resolvedType.tagBits & TagBits.AnnotationNullable) != 0) {
		scope.problemReporter().arrayReferencePotentialNullReference(this);
		return true;
	} else {
		return super.checkNPE(scope, flowContext, flowInfo, ttlForFieldCheck);
	}
}

@Override
public void generateAssignment(BlockScope currentScope, CodeStream codeStream, Assignment assignment, boolean valueRequired) {
	int pc = codeStream.position;
	this.receiver.generateCode(currentScope, codeStream, true);
	if (this.receiver instanceof CastExpression	// ((type[])null)[0]
			&& ((CastExpression)this.receiver).innermostCastedExpression().resolvedType == TypeBinding.NULL){
		codeStream.checkcast(this.receiver.resolvedType);
	}
	codeStream.recordPositionsFrom(pc, this.sourceStart);
	this.position.generateCode(currentScope, codeStream, true);
	assignment.expression.generateCode(currentScope, codeStream, true);
	codeStream.arrayAtPut(this.resolvedType.id, valueRequired);
	if (valueRequired) {
		codeStream.generateImplicitConversion(assignment.implicitConversion);
	}
}

Code generation for a array reference
/**
 * Code generation for a array reference
 */
@Override
public void generateCode(BlockScope currentScope, CodeStream codeStream, boolean valueRequired) {
	int pc = codeStream.position;
	this.receiver.generateCode(currentScope, codeStream, true);
	if (this.receiver instanceof CastExpression	// ((type[])null)[0]
			&& ((CastExpression)this.receiver).innermostCastedExpression().resolvedType == TypeBinding.NULL){
		codeStream.checkcast(this.receiver.resolvedType);
	}
	this.position.generateCode(currentScope, codeStream, true);
	codeStream.arrayAt(this.resolvedType.id);
	// Generating code for the potential runtime type checking
	if (valueRequired) {
		codeStream.generateImplicitConversion(this.implicitConversion);
	} else {
		boolean isUnboxing = (this.implicitConversion & TypeIds.UNBOXING) != 0;
		// conversion only generated if unboxing
		if (isUnboxing) codeStream.generateImplicitConversion(this.implicitConversion);
		switch (isUnboxing ? postConversionType(currentScope).id : this.resolvedType.id) {
			case T_long :
			case T_double :
				codeStream.pop2();
				break;
			default :
				codeStream.pop();
		}
	}
	codeStream.recordPositionsFrom(pc, this.sourceStart);
}

@Override
public void generateCompoundAssignment(BlockScope currentScope, CodeStream codeStream, Expression expression, int operator, int assignmentImplicitConversion, boolean valueRequired) {
	this.receiver.generateCode(currentScope, codeStream, true);
	if (this.receiver instanceof CastExpression	// ((type[])null)[0]
			&& ((CastExpression)this.receiver).innermostCastedExpression().resolvedType == TypeBinding.NULL){
		codeStream.checkcast(this.receiver.resolvedType);
	}
	this.position.generateCode(currentScope, codeStream, true);
	codeStream.dup2();
	codeStream.arrayAt(this.resolvedType.id);
	int operationTypeID;
	switch(operationTypeID = (this.implicitConversion & TypeIds.IMPLICIT_CONVERSION_MASK) >> 4) {
		case T_JavaLangString :
		case T_JavaLangObject :
		case T_undefined :
			codeStream.generateStringConcatenationAppend(currentScope, null, expression);
			break;
		default :
			// promote the array reference to the suitable operation type
			codeStream.generateImplicitConversion(this.implicitConversion);
			// generate the increment value (will by itself  be promoted to the operation value)
			if (expression == IntLiteral.One) { // prefix operation
				codeStream.generateConstant(expression.constant, this.implicitConversion);
			} else {
				expression.generateCode(currentScope, codeStream, true);
			}
			// perform the operation
			codeStream.sendOperator(operator, operationTypeID);
			// cast the value back to the array reference type
			codeStream.generateImplicitConversion(assignmentImplicitConversion);
	}
	codeStream.arrayAtPut(this.resolvedType.id, valueRequired);
}

@Override
public void generatePostIncrement(BlockScope currentScope, CodeStream codeStream, CompoundAssignment postIncrement, boolean valueRequired) {
	this.receiver.generateCode(currentScope, codeStream, true);
	if (this.receiver instanceof CastExpression	// ((type[])null)[0]
			&& ((CastExpression)this.receiver).innermostCastedExpression().resolvedType == TypeBinding.NULL){
		codeStream.checkcast(this.receiver.resolvedType);
	}
	this.position.generateCode(currentScope, codeStream, true);
	codeStream.dup2();
	codeStream.arrayAt(this.resolvedType.id);
	if (valueRequired) {
		switch(this.resolvedType.id) {
			case TypeIds.T_long :
			case TypeIds.T_double :
				codeStream.dup2_x2();
				break;
			default :
				codeStream.dup_x2();
				break;
		}
	}
	codeStream.generateImplicitConversion(this.implicitConversion);
	codeStream.generateConstant(
		postIncrement.expression.constant,
		this.implicitConversion);
	codeStream.sendOperator(postIncrement.operator, this.implicitConversion & TypeIds.COMPILE_TYPE_MASK);
	codeStream.generateImplicitConversion(
		postIncrement.preAssignImplicitConversion);
	codeStream.arrayAtPut(this.resolvedType.id, false);
}

@Override
public StringBuffer printExpression(int indent, StringBuffer output) {
	this.receiver.printExpression(0, output).append('[');
	return this.position.printExpression(0, output).append(']');
}

@Override
public TypeBinding resolveType(BlockScope scope) {
	this.constant = Constant.NotAConstant;
	if (this.receiver instanceof CastExpression	// no cast check for ((type[])null)[0]
			&& ((CastExpression)this.receiver).innermostCastedExpression() instanceof NullLiteral) {
		this.receiver.bits |= ASTNode.DisableUnnecessaryCastCheck; // will check later on
	}
	TypeBinding arrayType = this.receiver.resolveType(scope);
	if (arrayType != null) {
		this.receiver.computeConversion(scope, arrayType, arrayType);
		if (arrayType.isArrayType()) {
			TypeBinding elementType = ((ArrayBinding) arrayType).elementsType();
			this.resolvedType = ((this.bits & ASTNode.IsStrictlyAssigned) == 0) ? elementType.capture(scope, this.sourceStart, this.sourceEnd) : elementType;
		} else {
			scope.problemReporter().referenceMustBeArrayTypeAt(arrayType, this);
		}
	}
	TypeBinding positionType = this.position.resolveTypeExpecting(scope, TypeBinding.INT);
	if (positionType != null) {
		this.position.computeConversion(scope, TypeBinding.INT, positionType);
	}
	return this.resolvedType;
}

@Override
public void traverse(ASTVisitor visitor, BlockScope scope) {
	if (visitor.visit(this, scope)) {
		this.receiver.traverse(visitor, scope);
		this.position.traverse(visitor, scope);
	}
	visitor.endVisit(this, scope);
}

@Override
public int nullStatus(FlowInfo flowInfo, FlowContext flowContext) {
	if (this.resolvedType != null && (this.resolvedType.tagBits & TagBits.AnnotationNullMASK) == 0L && this.resolvedType.isFreeTypeVariable()) {
		return FlowInfo.FREE_TYPEVARIABLE;
	}
	return super.nullStatus(flowInfo, flowContext);
}
}