Copyright (c) 2000, 2019 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  - Contributions for
							bug 185682 - Increment/decrement operators mark local variables as read
							bug 392862 - [1.8][compiler][null] Evaluate null annotations on array types
							bug 331649 - [compiler][null] consider null annotations for fields
							bug 383368 - [compiler][null] syntactic null analysis for field references
							bug 392384 - [1.8][compiler][null] Restore nullness info from type annotations in class files
							Bug 392099 - [1.8][compiler][null] Apply null annotation on types for null analysis 
							Bug 411964 - [1.8][null] leverage null type annotation in foreach statement
							Bug 407414 - [compiler][null] Incorrect warning on a primitive type being null
/*******************************************************************************
 * Copyright (c) 2000, 2019 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 <stephan@cs.tu-berlin.de> - Contributions for
 *								bug 185682 - Increment/decrement operators mark local variables as read
 *								bug 392862 - [1.8][compiler][null] Evaluate null annotations on array types
 *								bug 331649 - [compiler][null] consider null annotations for fields
 *								bug 383368 - [compiler][null] syntactic null analysis for field references
 *								bug 392384 - [1.8][compiler][null] Restore nullness info from type annotations in class files
 *								Bug 392099 - [1.8][compiler][null] Apply null annotation on types for null analysis 
 *								Bug 411964 - [1.8][null] leverage null type annotation in foreach statement
 *								Bug 407414 - [compiler][null] Incorrect warning on a primitive type being null
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;

import org.eclipse.jdt.internal.compiler.codegen.CodeStream;
import org.eclipse.jdt.internal.compiler.codegen.Opcodes;
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.BlockScope;
import org.eclipse.jdt.internal.compiler.lookup.ExtraCompilerModifiers;
import org.eclipse.jdt.internal.compiler.lookup.FieldBinding;
import org.eclipse.jdt.internal.compiler.lookup.LocalVariableBinding;
import org.eclipse.jdt.internal.compiler.lookup.MethodBinding;
import org.eclipse.jdt.internal.compiler.lookup.MethodScope;
import org.eclipse.jdt.internal.compiler.lookup.Scope;
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 abstract class Reference extends Expression  {
BaseLevelReference constructor comment.
/**
 * BaseLevelReference constructor comment.
 */
public Reference() {
	super();
}
public abstract FlowInfo analyseAssignment(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo, Assignment assignment, boolean isCompound);

@Override
public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
	return flowInfo;
}

@Override
public boolean checkNPE(BlockScope scope, FlowContext flowContext, FlowInfo flowInfo, int ttlForFieldCheck) {
	if (flowContext.isNullcheckedFieldAccess(this)) {
		return true; // enough seen
	}
	return super.checkNPE(scope, flowContext, flowInfo, ttlForFieldCheck);
}

protected boolean checkNullableFieldDereference(Scope scope, FieldBinding field, long sourcePosition, FlowContext flowContext, int ttlForFieldCheck) {
	if (field != null) {
		if (ttlForFieldCheck > 0 && scope.compilerOptions().enableSyntacticNullAnalysisForFields)
			flowContext.recordNullCheckedFieldReference(this, ttlForFieldCheck);
		// preference to type annotations if we have any
		if ((field.type.tagBits & TagBits.AnnotationNullable) != 0) {
			scope.problemReporter().dereferencingNullableExpression(sourcePosition, scope.environment());
			return true;
		} 
		if (field.type.isFreeTypeVariable()) {
			scope.problemReporter().fieldFreeTypeVariableReference(field, sourcePosition);
			return true;
		}
		if ((field.tagBits & TagBits.AnnotationNullable) != 0) {
			scope.problemReporter().nullableFieldDereference(field, sourcePosition);
			return true;
		}
	}
	return false;
}

public FieldBinding fieldBinding() {
	//this method should be sent one FIELD-tagged references
	//  (ref.bits & BindingIds.FIELD != 0)()
	return null ;
}

public void fieldStore(Scope currentScope, CodeStream codeStream, FieldBinding fieldBinding, MethodBinding syntheticWriteAccessor, TypeBinding receiverType, boolean isImplicitThisReceiver, boolean valueRequired) {
	int pc = codeStream.position;
	if (fieldBinding.isStatic()) {
		if (valueRequired) {
			switch (fieldBinding.type.id) {
				case TypeIds.T_long :
				case TypeIds.T_double :
					codeStream.dup2();
					break;
				default : 
					codeStream.dup();
					break;
			}
		}
		if (syntheticWriteAccessor == null) {
			TypeBinding constantPoolDeclaringClass = CodeStream.getConstantPoolDeclaringClass(currentScope, fieldBinding, receiverType, isImplicitThisReceiver);
			codeStream.fieldAccess(Opcodes.OPC_putstatic, fieldBinding, constantPoolDeclaringClass);
		} else {
			codeStream.invoke(Opcodes.OPC_invokestatic, syntheticWriteAccessor, null /* default declaringClass */);
		}
	} else { // Stack:  [owner][new field value]  ---> [new field value][owner][new field value]
		if (valueRequired) {
			switch (fieldBinding.type.id) {
				case TypeIds.T_long :
				case TypeIds.T_double :
					codeStream.dup2_x1();
					break;
				default : 
					codeStream.dup_x1();
					break;
			}
		}
		if (syntheticWriteAccessor == null) {
			TypeBinding constantPoolDeclaringClass = CodeStream.getConstantPoolDeclaringClass(currentScope, fieldBinding, receiverType, isImplicitThisReceiver);
			codeStream.fieldAccess(Opcodes.OPC_putfield, fieldBinding, constantPoolDeclaringClass);
		} else {
			codeStream.invoke(Opcodes.OPC_invokestatic, syntheticWriteAccessor, null /* default declaringClass */);
		}
	}
	codeStream.recordPositionsFrom(pc, this.sourceStart);
}

public abstract void generateAssignment(BlockScope currentScope, CodeStream codeStream, Assignment assignment, boolean valueRequired);

public abstract void generateCompoundAssignment(BlockScope currentScope, CodeStream codeStream, Expression expression, int operator, int assignmentImplicitConversion, boolean valueRequired);

public abstract void generatePostIncrement(BlockScope currentScope, CodeStream codeStream, CompoundAssignment postIncrement, boolean valueRequired);

Is the given reference equivalent to the receiver, meaning that both denote the same path of field reads? Used from FlowContext.isNullcheckedFieldAccess(Reference). /** 
 * Is the given reference equivalent to the receiver, 
 * meaning that both denote the same path of field reads?
 * Used from {@link FlowContext#isNullcheckedFieldAccess(Reference)}.
 */
public boolean isEquivalent(Reference reference) {
	return false;
}

public FieldBinding lastFieldBinding() {
	// override to answer the field designated by the entire reference
	// (as opposed to fieldBinding() which answers the first field in a QNR)
	return null;
}

@Override
public int nullStatus(FlowInfo flowInfo, FlowContext flowContext) {
	if ((this.implicitConversion & TypeIds.BOXING) != 0)
		return FlowInfo.NON_NULL;
	FieldBinding fieldBinding = lastFieldBinding();
	if (fieldBinding != null) {
		if (fieldBinding.isFinal() && fieldBinding.constant() != Constant.NotAConstant)
			return FlowInfo.NON_NULL;
		if (fieldBinding.isNonNull() || flowContext.isNullcheckedFieldAccess(this)) {
			return FlowInfo.NON_NULL;
		} else if (fieldBinding.isNullable()) {
			return FlowInfo.POTENTIALLY_NULL;
		} else if (fieldBinding.type.isFreeTypeVariable()) {
			return FlowInfo.FREE_TYPEVARIABLE;
		}
	}
	if (this.resolvedType != null) {
		return FlowInfo.tagBitsToNullStatus(this.resolvedType.tagBits);
	}
	return FlowInfo.UNKNOWN;
}

/* report if a private field is only read from a 'special operator',
 * i.e., in a postIncrement expression or a compound assignment,
 * where the information is never flowing out off the field. */
void reportOnlyUselesslyReadPrivateField(BlockScope currentScope, FieldBinding fieldBinding, boolean valueRequired) {
	if (valueRequired) {
		// access is relevant, turn compound use into real use:
		fieldBinding.compoundUseFlag = 0;
		fieldBinding.modifiers |= ExtraCompilerModifiers.AccLocallyUsed;
	} else {
		if (fieldBinding.isUsedOnlyInCompound()) {
			fieldBinding.compoundUseFlag--; // consume one
			if (fieldBinding.compoundUseFlag == 0					// report only the last usage
					&& fieldBinding.isOrEnclosedByPrivateType() 
					&& (this.implicitConversion & TypeIds.UNBOXING) == 0) // don't report if unboxing is involved (might cause NPE)
			{
				// compoundAssignment/postIncrement is the only usage of this field
				currentScope.problemReporter().unusedPrivateField(fieldBinding.sourceField());
			}
		}
	}
}
/* report a local/arg that is only read from a 'special operator',
 * i.e., in a postIncrement expression or a compound assignment,
 * where the information is never flowing out off the local/arg. */
static void reportOnlyUselesslyReadLocal(BlockScope currentScope, LocalVariableBinding localBinding, boolean valueRequired) {
	if (localBinding.declaration == null)
		return;  // secret local
	if ((localBinding.declaration.bits & ASTNode.IsLocalDeclarationReachable) == 0)
		return;  // declaration is unreachable
	if (localBinding.useFlag >= LocalVariableBinding.USED)
		return;  // we're only interested in cases with only compound access (negative count)

	if (valueRequired) {
		// access is relevant
		localBinding.useFlag = LocalVariableBinding.USED;
		return;
	} else {
		localBinding.useFlag++;
		if (localBinding.useFlag != LocalVariableBinding.UNUSED) // have all negative counts been consumed?
			return; // still waiting to see more usages of this kind
	}
	// at this point we know we have something to report
	if (localBinding.declaration instanceof Argument) {
		// check compiler options to report against unused arguments
		MethodScope methodScope = currentScope.methodScope();
		if (methodScope != null && !methodScope.isLambdaScope()) { // lambda must be congruent with the descriptor.
			MethodBinding method = ((AbstractMethodDeclaration)methodScope.referenceContext()).binding;
			
			boolean shouldReport = !method.isMain();
			if (method.isImplementing()) {
				shouldReport &= currentScope.compilerOptions().reportUnusedParameterWhenImplementingAbstract;
			} else if (method.isOverriding()) {
				shouldReport &= currentScope.compilerOptions().reportUnusedParameterWhenOverridingConcrete;
			}
			
			if (shouldReport) {
				// report the case of an argument that is unread except through a special operator
				currentScope.problemReporter().unusedArgument(localBinding.declaration);
			}
		}
	} else {
		// report the case of a local variable that is unread except for a special operator
		currentScope.problemReporter().unusedLocalVariable(localBinding.declaration);
	}
}
}