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
    Genady Beriozkin - added support for reporting assignment with no effect
    Stephan Herrmann  - Contributions for
							bug 319201 - [null] no warning when unboxing SingleNameReference causes NPE
							bug 292478 - Report potentially null across variable assignment
    						bug 335093 - [compiler][null] minimal hook for future null annotation support
    						bug 349326 - [1.7] new warning for missing try-with-resources
						bug 186342 - [compiler][null] Using annotations for null checking
						bug 358903 - Filter practically unimportant resource leak warnings
						bug 370639 - [compiler][resource] restore the default for resource leak warnings
						bug 365859 - [compiler][null] distinguish warnings based on flow analysis vs. null annotations
						bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
						bug 388996 - [compiler][resource] Incorrect 'potential resource leak'
						bug 394768 - [compiler][resource] Incorrect resource leak warning when creating stream in conditional
						bug 395002 - Self bound generic class doesn't resolve bounds properly for wildcards for certain parametrisation.
						bug 331649 - [compiler][null] consider null annotations for fields
						bug 383368 - [compiler][null] syntactic null analysis for field references
						bug 402993 - [null] Follow up of bug 401088: Missing warning about redundant null check
						bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
						Bug 392099 - [1.8][compiler][null] Apply null annotation on types for null analysis
						Bug 427438 - [1.8][compiler] NPE at org.eclipse.jdt.internal.compiler.ast.ConditionalExpression.generateCode(ConditionalExpression.java:280)
						Bug 453483 - [compiler][null][loop] Improve null analysis for loops
						Bug 407414 - [compiler][null] Incorrect warning on a primitive type being null
/*******************************************************************************
 * 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
 *     Genady Beriozkin - added support for reporting assignment with no effect
 *     Stephan Herrmann <stephan@cs.tu-berlin.de> - Contributions for
 * 							bug 319201 - [null] no warning when unboxing SingleNameReference causes NPE
 * 							bug 292478 - Report potentially null across variable assignment
 *     						bug 335093 - [compiler][null] minimal hook for future null annotation support
 *     						bug 349326 - [1.7] new warning for missing try-with-resources
 *							bug 186342 - [compiler][null] Using annotations for null checking
 *							bug 358903 - Filter practically unimportant resource leak warnings
 *							bug 370639 - [compiler][resource] restore the default for resource leak warnings
 *							bug 365859 - [compiler][null] distinguish warnings based on flow analysis vs. null annotations
 *							bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
 *							bug 388996 - [compiler][resource] Incorrect 'potential resource leak'
 *							bug 394768 - [compiler][resource] Incorrect resource leak warning when creating stream in conditional
 *							bug 395002 - Self bound generic class doesn't resolve bounds properly for wildcards for certain parametrisation.
 *							bug 331649 - [compiler][null] consider null annotations for fields
 *							bug 383368 - [compiler][null] syntactic null analysis for field references
 *							bug 402993 - [null] Follow up of bug 401088: Missing warning about redundant null check
 *							bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
 *							Bug 392099 - [1.8][compiler][null] Apply null annotation on types for null analysis
 *							Bug 427438 - [1.8][compiler] NPE at org.eclipse.jdt.internal.compiler.ast.ConditionalExpression.generateCode(ConditionalExpression.java:280)
 *							Bug 453483 - [compiler][null][loop] Improve null analysis for loops
 *							Bug 407414 - [compiler][null] Incorrect warning on a primitive type being null
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;

import static org.eclipse.jdt.internal.compiler.ast.ExpressionContext.ASSIGNMENT_CONTEXT;

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.CompilerOptions;
import org.eclipse.jdt.internal.compiler.impl.Constant;
import org.eclipse.jdt.internal.compiler.lookup.*;

public class Assignment extends Expression {

	public Expression lhs;
	public Expression expression;

public Assignment(Expression lhs, Expression expression, int sourceEnd) {
	this.lhs = lhs;
	lhs.bits |= IsStrictlyAssigned; // tag lhs as assigned
	this.expression = expression;
	this.sourceStart = lhs.sourceStart;
	this.sourceEnd = sourceEnd;
}

@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.
	LocalVariableBinding local = this.lhs.localVariableBinding();
	this.expression.checkNPEbyUnboxing(currentScope, flowContext, flowInfo);
	
	FlowInfo preInitInfo = null;
	CompilerOptions compilerOptions = currentScope.compilerOptions();
	boolean shouldAnalyseResource = local != null
			&& flowInfo.reachMode() == FlowInfo.REACHABLE
			&& compilerOptions.analyseResourceLeaks
			&& (FakedTrackingVariable.isAnyCloseable(this.expression.resolvedType)
					|| this.expression.resolvedType == TypeBinding.NULL);
	if (shouldAnalyseResource) {
		preInitInfo = flowInfo.unconditionalCopy();
		// analysis of resource leaks needs additional context while analyzing the RHS:
		FakedTrackingVariable.preConnectTrackerAcrossAssignment(this, local, this.expression, flowInfo);
	}
	
	flowInfo = ((Reference) this.lhs)
		.analyseAssignment(currentScope, flowContext, flowInfo, this, false)
		.unconditionalInits();

	if (shouldAnalyseResource)
		FakedTrackingVariable.handleResourceAssignment(currentScope, preInitInfo, flowInfo, flowContext, this, this.expression, local);
	else
		FakedTrackingVariable.cleanUpAfterAssignment(currentScope, this.lhs.bits, this.expression);

	int nullStatus = this.expression.nullStatus(flowInfo, flowContext);
	if (local != null && (local.type.tagBits & TagBits.IsBaseType) == 0) {
		if (nullStatus == FlowInfo.NULL) {
			flowContext.recordUsingNullReference(currentScope, local, this.lhs,
				FlowContext.CAN_ONLY_NULL | FlowContext.IN_ASSIGNMENT, flowInfo);
		}
	}
	if (compilerOptions.isAnnotationBasedNullAnalysisEnabled) {
		VariableBinding var = this.lhs.nullAnnotatedVariableBinding(compilerOptions.sourceLevel >= ClassFileConstants.JDK1_8);
		if (var != null) {
			nullStatus = NullAnnotationMatching.checkAssignment(currentScope, flowContext, var, flowInfo, nullStatus, this.expression, this.expression.resolvedType);
			if (nullStatus == FlowInfo.NON_NULL
					&& var instanceof FieldBinding
					&& this.lhs instanceof Reference
					&& compilerOptions.enableSyntacticNullAnalysisForFields)
			{
				int timeToLive = (this.bits & InsideExpressionStatement) != 0
									? 2  // assignment is statement: make info survives the end of this statement
									: 1; // assignment is expression: expire on next event.
				flowContext.recordNullCheckedFieldReference((Reference) this.lhs, timeToLive);
			}
		}
	}
	if (local != null && (local.type.tagBits & TagBits.IsBaseType) == 0) {
		flowInfo.markNullStatus(local, nullStatus);
		flowContext.markFinallyNullStatus(local, nullStatus);
	}
	return flowInfo;
}

void checkAssignment(BlockScope scope, TypeBinding lhsType, TypeBinding rhsType) {
	FieldBinding leftField = getLastField(this.lhs);
	if (leftField != null &&  rhsType != TypeBinding.NULL && (lhsType.kind() == Binding.WILDCARD_TYPE) && ((WildcardBinding)lhsType).boundKind != Wildcard.SUPER) {
	    scope.problemReporter().wildcardAssignment(lhsType, rhsType, this.expression);
	} else if (leftField != null && !leftField.isStatic() && leftField.declaringClass != null /*length pseudo field*/&& leftField.declaringClass.isRawType()) {
	    scope.problemReporter().unsafeRawFieldAssignment(leftField, rhsType, this.lhs);
	} else if (rhsType.needsUncheckedConversion(lhsType)) {
	    scope.problemReporter().unsafeTypeConversion(this.expression, rhsType, lhsType);
	}
}

@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).generateAssignment(currentScope, codeStream, this, valueRequired);
	// variable may have been optimized out
	// the lhs is responsible to perform the implicitConversion generation for the assignment since optimized for unused local assignment.
	codeStream.recordPositionsFrom(pc, this.sourceStart);
}

FieldBinding getLastField(Expression someExpression) {
    if (someExpression instanceof SingleNameReference) {
        if ((someExpression.bits & RestrictiveFlagMASK) == Binding.FIELD) {
            return (FieldBinding) ((SingleNameReference)someExpression).binding;
        }
    } else if (someExpression instanceof FieldReference) {
        return ((FieldReference)someExpression).binding;
    } else if (someExpression instanceof QualifiedNameReference) {
        QualifiedNameReference qName = (QualifiedNameReference) someExpression;
        if (qName.otherBindings == null) {
        	if ((someExpression.bits & RestrictiveFlagMASK) == Binding.FIELD) {
        		return (FieldBinding)qName.binding;
        	}
        } else {
            return qName.otherBindings[qName.otherBindings.length - 1];
        }
    }
    return null;
}

@Override
public int nullStatus(FlowInfo flowInfo, FlowContext flowContext) {
	if ((this.implicitConversion & TypeIds.BOXING) != 0)
		return FlowInfo.NON_NULL;
	return this.expression.nullStatus(flowInfo, flowContext);
}

@Override
public StringBuffer print(int indent, StringBuffer output) {
	//no () when used as a statement
	printIndent(indent, output);
	return printExpressionNoParenthesis(indent, output);
}
@Override
public StringBuffer printExpression(int indent, StringBuffer output) {
	//subclass redefine printExpressionNoParenthesis()
	output.append('(');
	return printExpressionNoParenthesis(0, output).append(')');
}

public StringBuffer printExpressionNoParenthesis(int indent, StringBuffer output) {
	this.lhs.printExpression(indent, output).append(" = "); //$NON-NLS-1$
	return this.expression.printExpression(0, output);
}

@Override
public StringBuffer printStatement(int indent, StringBuffer output) {
	//no () when used as a statement
	return print(indent, output).append(';');
}

@Override
public TypeBinding resolveType(BlockScope scope) {
	// due to syntax lhs may be only a NameReference, a FieldReference or an ArrayReference
	this.constant = Constant.NotAConstant;
	if (!(this.lhs instanceof Reference) || this.lhs.isThis()) {
		scope.problemReporter().expressionShouldBeAVariable(this.lhs);
		return null;
	}
	TypeBinding lhsType = this.lhs.resolveType(scope);
	this.expression.setExpressionContext(ASSIGNMENT_CONTEXT);
	this.expression.setExpectedType(lhsType); // needed in case of generic method invocation
	if (lhsType != null) {
		this.resolvedType = lhsType.capture(scope, this.lhs.sourceStart, this.lhs.sourceEnd); // make it unique, `this' shares source end with 'this.expression'.
	}
	LocalVariableBinding localVariableBinding = this.lhs.localVariableBinding();
	if (localVariableBinding != null && (localVariableBinding.isCatchParameter() || localVariableBinding.isParameter())) { 
		localVariableBinding.tagBits &= ~TagBits.IsEffectivelyFinal;  // as it is already definitely assigned, we can conclude already. Also note: catch parameter cannot be compound assigned.
	}
	TypeBinding rhsType = this.expression.resolveType(scope);
	if (lhsType == null || rhsType == null) {
		return null;
	}
	// check for assignment with no effect
	Binding left = getDirectBinding(this.lhs);
	if (left != null && !left.isVolatile() && left == getDirectBinding(this.expression)) {
		scope.problemReporter().assignmentHasNoEffect(this, left.shortReadableName());
	}

	// Compile-time conversion of base-types : implicit narrowing integer into byte/short/character
	// may require to widen the rhs expression at runtime
	if (TypeBinding.notEquals(lhsType, rhsType)) { // must call before computeConversion() and typeMismatchError()
		scope.compilationUnitScope().recordTypeConversion(lhsType, rhsType);
	}
	if (this.expression.isConstantValueOfTypeAssignableToType(rhsType, lhsType)
			|| rhsType.isCompatibleWith(lhsType, scope)) {
		this.expression.computeConversion(scope, lhsType, rhsType);
		checkAssignment(scope, lhsType, rhsType);
		if (this.expression instanceof CastExpression
				&& (this.expression.bits & ASTNode.UnnecessaryCast) == 0) {
			CastExpression.checkNeedForAssignedCast(scope, lhsType, (CastExpression) this.expression);
		}
		return this.resolvedType;
	} else if (isBoxingCompatible(rhsType, lhsType, this.expression, scope)) {
		this.expression.computeConversion(scope, lhsType, rhsType);
		if (this.expression instanceof CastExpression
				&& (this.expression.bits & ASTNode.UnnecessaryCast) == 0) {
			CastExpression.checkNeedForAssignedCast(scope, lhsType, (CastExpression) this.expression);
		}
		return this.resolvedType;
	}
	scope.problemReporter().typeMismatchError(rhsType, lhsType, this.expression, this.lhs);
	return lhsType;
}

See Also:
resolveTypeExpecting.resolveTypeExpecting(BlockScope, TypeBinding)/**
 * @see org.eclipse.jdt.internal.compiler.ast.Expression#resolveTypeExpecting(org.eclipse.jdt.internal.compiler.lookup.BlockScope, org.eclipse.jdt.internal.compiler.lookup.TypeBinding)
 */
@Override
public TypeBinding resolveTypeExpecting(BlockScope scope, TypeBinding expectedType) {

	TypeBinding type = super.resolveTypeExpecting(scope, expectedType);
	if (type == null) return null;
	TypeBinding lhsType = this.resolvedType;
	TypeBinding rhsType = this.expression.resolvedType;
	// signal possible accidental boolean assignment (instead of using '==' operator)
	if (TypeBinding.equalsEquals(expectedType, TypeBinding.BOOLEAN)
			&& TypeBinding.equalsEquals(lhsType, TypeBinding.BOOLEAN)
			&& (this.lhs.bits & IsStrictlyAssigned) != 0) {
		scope.problemReporter().possibleAccidentalBooleanAssignment(this);
	}
	checkAssignment(scope, lhsType, rhsType);
	return type;
}

@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);
}
@Override
public LocalVariableBinding localVariableBinding() {
	return this.lhs.localVariableBinding();
}
@Override
public boolean statementExpression() {
	return ((this.bits & ASTNode.ParenthesizedMASK) == 0);
}
}