Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2018 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 383368 - [compiler][null] syntactic null analysis for field references * bug 402993 - [null] Follow up of bug 401088: Missing warning about redundant null check * Jesper S Moller - Contributions for * bug 382721 - [1.8][compiler] Effectively final variables needs special treatment *******************************************************************************/ package org.eclipse.jdt.internal.compiler.ast; import org.eclipse.jdt.internal.compiler.ASTVisitor; import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants; import org.eclipse.jdt.internal.compiler.codegen.*; import org.eclipse.jdt.internal.compiler.flow.*; import org.eclipse.jdt.internal.compiler.impl.Constant; import org.eclipse.jdt.internal.compiler.lookup.*; public class CompoundAssignment extends Assignment implements OperatorIds { public int operator; public int preAssignImplicitConversion; // var op exp is equivalent to var = (varType) var op exp // assignmentImplicitConversion stores the cast needed for the assignment public CompoundAssignment(Expression lhs, Expression expression, int operator, int sourceEnd) { //lhs is always a reference by construction , //but is build as an expression ==> the checkcast cannot fail super(lhs, expression, sourceEnd); lhs.bits &= ~IsStrictlyAssigned; // tag lhs as NON assigned - it is also a read access lhs.bits |= IsCompoundAssigned; // tag lhs as assigned by compound this.operator = operator; } @Override public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) { // record setting a variable: various scenarii are possible, setting an array reference, // a field reference, a blank final field reference, a field of an enclosing instance or // just a local variable. if (this.resolvedType.id != T_JavaLangString) { this.lhs.checkNPE(currentScope, flowContext, flowInfo); // account for exceptions thrown by any arithmetics: flowContext.recordAbruptExit(); } this.expression.checkNPEbyUnboxing(currentScope, flowContext, flowInfo); flowInfo = ((Reference) this.lhs).analyseAssignment(currentScope, flowContext, flowInfo, this, true) .unconditionalInits(); if (this.resolvedType.id == T_JavaLangString) { // https://bugs.eclipse.org/bugs/show_bug.cgi?id=339250 LocalVariableBinding local = this.lhs.localVariableBinding(); if (local != null) { // compound assignment results in a definitely non null value for String flowInfo.markAsDefinitelyNonNull(local); flowContext.markFinallyNullStatus(local, FlowInfo.NON_NULL); } } return flowInfo; } public boolean checkCastCompatibility() { return true; } @Override public void generateCode(BlockScope currentScope, CodeStream codeStream, boolean valueRequired) { // various scenarii are possible, setting an array reference, // a field reference, a blank final field reference, a field of an enclosing instance or // just a local variable. int pc = codeStream.position; ((Reference) this.lhs).generateCompoundAssignment(currentScope, codeStream, this.expression, this.operator, this.preAssignImplicitConversion, valueRequired); if (valueRequired) { codeStream.generateImplicitConversion(this.implicitConversion); } codeStream.recordPositionsFrom(pc, this.sourceStart); } @Override public int nullStatus(FlowInfo flowInfo, FlowContext flowContext) { return FlowInfo.NON_NULL; // we may have complained on checkNPE, but we avoid duplicate error } public String operatorToString() { switch (this.operator) { case PLUS: return "+="; //$NON-NLS-1$ case MINUS: return "-="; //$NON-NLS-1$ case MULTIPLY: return "*="; //$NON-NLS-1$ case DIVIDE: return "/="; //$NON-NLS-1$ case AND: return "&="; //$NON-NLS-1$ case OR: return "|="; //$NON-NLS-1$ case XOR: return "^="; //$NON-NLS-1$ case REMAINDER: return "%="; //$NON-NLS-1$ case LEFT_SHIFT: return "<<="; //$NON-NLS-1$ case RIGHT_SHIFT: return ">>="; //$NON-NLS-1$ case UNSIGNED_RIGHT_SHIFT: return ">>>="; //$NON-NLS-1$ } return "unknown operator"; //$NON-NLS-1$ } @Override public StringBuffer printExpressionNoParenthesis(int indent, StringBuffer output) { this.lhs.printExpression(indent, output).append(' ').append(operatorToString()).append(' '); return this.expression.printExpression(0, output); } @Override public TypeBinding resolveType(BlockScope scope) { this.constant = Constant.NotAConstant; if (!(this.lhs instanceof Reference) || this.lhs.isThis()) { scope.problemReporter().expressionShouldBeAVariable(this.lhs); return null; } boolean expressionIsCast = this.expression instanceof CastExpression; if (expressionIsCast) this.expression.bits |= ASTNode.DisableUnnecessaryCastCheck; // will check later on TypeBinding originalLhsType = this.lhs.resolveType(scope); TypeBinding originalExpressionType = this.expression.resolveType(scope); if (originalLhsType == null || originalExpressionType == null) return null; // autoboxing support LookupEnvironment env = scope.environment(); TypeBinding lhsType = originalLhsType, expressionType = originalExpressionType; boolean use15specifics = scope.compilerOptions().sourceLevel >= ClassFileConstants.JDK1_5; boolean unboxedLhs = false; if (use15specifics) { if (!lhsType.isBaseType() && expressionType.id != T_JavaLangString && expressionType.id != T_null) { TypeBinding unboxedType = env.computeBoxingType(lhsType); if (TypeBinding.notEquals(unboxedType, lhsType)) { lhsType = unboxedType; unboxedLhs = true; } } if (!expressionType.isBaseType() && lhsType.id != T_JavaLangString && lhsType.id != T_null) { expressionType = env.computeBoxingType(expressionType); } } if (restrainUsageToNumericTypes() && !lhsType.isNumericType()) { scope.problemReporter().operatorOnlyValidOnNumericType(this, lhsType, expressionType); return null; } int lhsID = lhsType.id; int expressionID = expressionType.id; if (lhsID > 15 || expressionID > 15) { if (lhsID != T_JavaLangString) { // String += Thread is valid whereas Thread += String is not scope.problemReporter().invalidOperator(this, lhsType, expressionType); return null; } expressionID = T_JavaLangObject; // use the Object has tag table } // the code is an int // (cast) left Op (cast) rigth --> result // 0000 0000 0000 0000 0000 // <<16 <<12 <<8 <<4 <<0 // the conversion is stored INTO the reference (info needed for the code gen) int result = OperatorExpression.OperatorSignatures[this.operator][(lhsID << 4) + expressionID]; if (result == T_undefined) { scope.problemReporter().invalidOperator(this, lhsType, expressionType); return null; } if (this.operator == PLUS) { if (lhsID == T_JavaLangObject && (scope.compilerOptions().complianceLevel < ClassFileConstants.JDK1_7)) { // <Object> += <String> is illegal (39248) for compliance < 1.7 scope.problemReporter().invalidOperator(this, lhsType, expressionType); return null; } else { // <int | boolean> += <String> is illegal if ((lhsType.isNumericType() || lhsID == T_boolean) && !expressionType.isNumericType()) { scope.problemReporter().invalidOperator(this, lhsType, expressionType); return null; } } } TypeBinding resultType = TypeBinding.wellKnownType(scope, result & 0x0000F); if (checkCastCompatibility()) { if (originalLhsType.id != T_JavaLangString && resultType.id != T_JavaLangString) { if (!checkCastTypesCompatibility(scope, originalLhsType, resultType, null)) { scope.problemReporter().invalidOperator(this, originalLhsType, expressionType); return null; } } } this.lhs.computeConversion(scope, TypeBinding.wellKnownType(scope, (result >>> 16) & 0x0000F), originalLhsType); this.expression.computeConversion(scope, TypeBinding.wellKnownType(scope, (result >>> 8) & 0x0000F), originalExpressionType); this.preAssignImplicitConversion = (unboxedLhs ? BOXING : 0) | (lhsID << 4) | (result & 0x0000F); if (unboxedLhs) scope.problemReporter().autoboxing(this, lhsType, originalLhsType); if (expressionIsCast) CastExpression.checkNeedForArgumentCasts(scope, this.operator, result, this.lhs, originalLhsType.id, false, this.expression, originalExpressionType.id, true); return this.resolvedType = originalLhsType; } public boolean restrainUsageToNumericTypes() { return false; } @Override public void traverse(ASTVisitor visitor, BlockScope scope) { if (visitor.visit(this, scope)) { this.lhs.traverse(visitor, scope); this.expression.traverse(visitor, scope); } visitor.endVisit(this, scope); } }