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 - Contributions for
							bug 319201 - [null] no warning when unboxing SingleNameReference causes NPE
							bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
							bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
							Bug 415790 - [compiler][resource]Incorrect potential resource leak warning in for loop with close in try/catch
/*******************************************************************************
 * 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 - Contributions for
 *								bug 319201 - [null] no warning when unboxing SingleNameReference causes NPE
 *								bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
 *								bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
 *								Bug 415790 - [compiler][resource]Incorrect potential resource leak warning in for loop with close in try/catch
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;

import org.eclipse.jdt.internal.compiler.ASTVisitor;
import org.eclipse.jdt.internal.compiler.impl.*;
import org.eclipse.jdt.internal.compiler.codegen.*;
import org.eclipse.jdt.internal.compiler.flow.*;
import org.eclipse.jdt.internal.compiler.lookup.*;

public class DoStatement extends Statement {

	public Expression condition;
	public Statement action;

	private BranchLabel breakLabel, continueLabel;

	// for local variables table attributes
	int mergedInitStateIndex = -1;
	int preConditionInitStateIndex = -1;

public DoStatement(Expression condition, Statement action, int sourceStart, int sourceEnd) {

	this.sourceStart = sourceStart;
	this.sourceEnd = sourceEnd;
	this.condition = condition;
	this.action = action;
	// remember useful empty statement
	if (action instanceof EmptyStatement) action.bits |= ASTNode.IsUsefulEmptyStatement;
}

@Override
public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
	this.breakLabel = new BranchLabel();
	this.continueLabel = new BranchLabel();
	LoopingFlowContext loopingContext =
		new LoopingFlowContext(
			flowContext,
			flowInfo,
			this,
			this.breakLabel,
			this.continueLabel,
			currentScope,
			false);

	Constant cst = this.condition.constant;
	boolean isConditionTrue = cst != Constant.NotAConstant && cst.booleanValue() == true;
	cst = this.condition.optimizedBooleanConstant();
	boolean isConditionOptimizedTrue = cst != Constant.NotAConstant && cst.booleanValue() == true;
	boolean isConditionOptimizedFalse = cst != Constant.NotAConstant && cst.booleanValue() == false;

	int previousMode = flowInfo.reachMode();

	FlowInfo initsOnCondition = flowInfo;
	UnconditionalFlowInfo actionInfo = flowInfo.nullInfoLessUnconditionalCopy();
	// we need to collect the contribution to nulls of the coming paths through the
	// loop, be they falling through normally or branched to break, continue labels
	// or catch blocks
	if ((this.action != null) && !this.action.isEmptyBlock()) {
		actionInfo = this.action.
			analyseCode(currentScope, loopingContext, actionInfo).
			unconditionalInits();

		// code generation can be optimized when no need to continue in the loop
		if ((actionInfo.tagBits &
				loopingContext.initsOnContinue.tagBits &
				FlowInfo.UNREACHABLE_OR_DEAD) != 0) {
			this.continueLabel = null;
		}
		if ((this.condition.implicitConversion & TypeIds.UNBOXING) != 0) {
			initsOnCondition = flowInfo.unconditionalInits().
									addInitializationsFrom(
										actionInfo.mergedWith(loopingContext.initsOnContinue));
		}
	}
	this.condition.checkNPEbyUnboxing(currentScope, flowContext, initsOnCondition);
	/* Reset reach mode, to address following scenario.
	 *   final blank;
	 *   do { if (true) break; else blank = 0; } while(false);
	 *   blank = 1; // may be initialized already
	 */
	actionInfo.setReachMode(previousMode);

	LoopingFlowContext condLoopContext;
	FlowInfo condInfo =
		this.condition.analyseCode(
			currentScope,
			(condLoopContext =
				new LoopingFlowContext(flowContext,	flowInfo, this, null,
					null, currentScope, true)),
			(this.action == null
				? actionInfo
				: (actionInfo.mergedWith(loopingContext.initsOnContinue))).copy());
	/* https://bugs.eclipse.org/bugs/show_bug.cgi?id=367023, we reach the condition at the bottom via two arcs, 
	   one by free fall and another by continuing... Merge initializations propagated through the two pathways,
	   cf, while and for loops.
	*/
	this.preConditionInitStateIndex = currentScope.methodScope().recordInitializationStates(actionInfo.mergedWith(loopingContext.initsOnContinue));
	if (!isConditionOptimizedFalse && this.continueLabel != null) {
		loopingContext.complainOnDeferredFinalChecks(currentScope, condInfo);
		condLoopContext.complainOnDeferredFinalChecks(currentScope, condInfo);
		loopingContext.complainOnDeferredNullChecks(currentScope,
				flowInfo.unconditionalCopy().addPotentialNullInfoFrom(
					  condInfo.initsWhenTrue().unconditionalInits()));
		condLoopContext.complainOnDeferredNullChecks(currentScope,
				actionInfo.addPotentialNullInfoFrom(
				  condInfo.initsWhenTrue().unconditionalInits()));
	} else {
		loopingContext.complainOnDeferredNullChecks(currentScope,
				flowInfo.unconditionalCopy().addPotentialNullInfoFrom(
					  condInfo.initsWhenTrue().unconditionalInits()), false);
		condLoopContext.complainOnDeferredNullChecks(currentScope,
				actionInfo.addPotentialNullInfoFrom(
				  condInfo.initsWhenTrue().unconditionalInits()), false);
	}
	if (loopingContext.hasEscapingExceptions()) { // https://bugs.eclipse.org/bugs/show_bug.cgi?id=321926
		FlowInfo loopbackFlowInfo = flowInfo.copy();
		// loopback | (loopback + action + condition):
		loopbackFlowInfo = loopbackFlowInfo.mergedWith(loopbackFlowInfo.unconditionalCopy().addNullInfoFrom(condInfo.initsWhenTrue()).unconditionalInits());
		loopingContext.simulateThrowAfterLoopBack(loopbackFlowInfo);
	}
	// end of loop
	FlowInfo mergedInfo = 
		FlowInfo.mergedOptimizedBranches(
						(loopingContext.initsOnBreak.tagBits & FlowInfo.UNREACHABLE) != 0
								? loopingContext.initsOnBreak
								: flowInfo.unconditionalCopy().addInitializationsFrom(loopingContext.initsOnBreak),
								// recover upstream null info
						isConditionOptimizedTrue,
						(condInfo.tagBits & FlowInfo.UNREACHABLE) == 0
								? flowInfo.copy().addInitializationsFrom(condInfo.initsWhenFalse()) // https://bugs.eclipse.org/bugs/show_bug.cgi?id=380927
								: condInfo,
							// recover null inits from before condition analysis
						false, // never consider opt false case for DO loop, since break can always occur (47776)
						!isConditionTrue /*do{}while(true); unreachable(); */);
	this.mergedInitStateIndex = currentScope.methodScope().recordInitializationStates(mergedInfo);
	return mergedInfo;
}

Do statement code generation
/**
 * Do statement code generation
 *
 */
@Override
public void generateCode(BlockScope currentScope, CodeStream codeStream) {
	if ((this.bits & ASTNode.IsReachable) == 0) {
		return;
	}
	int pc = codeStream.position;

	// labels management
	BranchLabel actionLabel = new BranchLabel(codeStream);
	if (this.action != null) actionLabel.tagBits |= BranchLabel.USED;
	actionLabel.place();
	this.breakLabel.initialize(codeStream);
	boolean hasContinueLabel = this.continueLabel != null;
	if (hasContinueLabel) {
		this.continueLabel.initialize(codeStream);
	}

	// generate action
	if (this.action != null) {
		this.action.generateCode(currentScope, codeStream);
	}
	// continue label (135602)
	if (hasContinueLabel) {
		this.continueLabel.place();
		// May loose some local variable initializations : affecting the local variable attributes
		if (this.preConditionInitStateIndex != -1) {
			codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.preConditionInitStateIndex);
			codeStream.addDefinitelyAssignedVariables(currentScope, this.preConditionInitStateIndex);
		}
		// generate condition
		Constant cst = this.condition.optimizedBooleanConstant();
		boolean isConditionOptimizedFalse = cst != Constant.NotAConstant && cst.booleanValue() == false;
		if (isConditionOptimizedFalse){
			this.condition.generateCode(currentScope, codeStream, false);
		} else {
			this.condition.generateOptimizedBoolean(
				currentScope,
				codeStream,
				actionLabel,
				null,
				true);
		}
	}
	// May loose some local variable initializations : affecting the local variable attributes
	if (this.mergedInitStateIndex != -1) {
		codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
		codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
	}
	if (this.breakLabel.forwardReferenceCount() > 0) {
		this.breakLabel.place();
	}

	codeStream.recordPositionsFrom(pc, this.sourceStart);
}

@Override
public StringBuffer printStatement(int indent, StringBuffer output) {
	printIndent(indent, output).append("do"); //$NON-NLS-1$
	if (this.action == null)
		output.append(" ;\n"); //$NON-NLS-1$
	else {
		output.append('\n');
		this.action.printStatement(indent + 1, output).append('\n');
	}
	output.append("while ("); //$NON-NLS-1$
	return this.condition.printExpression(0, output).append(");"); //$NON-NLS-1$
}

@Override
public void resolve(BlockScope scope) {
	TypeBinding type = this.condition.resolveTypeExpecting(scope, TypeBinding.BOOLEAN);
	this.condition.computeConversion(scope, type, type);
	if (this.action != null)
		this.action.resolve(scope);
}

@Override
public void traverse(ASTVisitor visitor, BlockScope scope) {
	if (visitor.visit(this, scope)) {
		if (this.action != null) {
			this.action.traverse(visitor, scope);
		}
		this.condition.traverse(visitor, scope);
	}
	visitor.endVisit(this, scope);
}

@Override
public boolean doesNotCompleteNormally() {
	Constant cst = this.condition.constant;
	boolean isConditionTrue = cst == null || cst != Constant.NotAConstant && cst.booleanValue() == true;
	cst = this.condition.optimizedBooleanConstant();
	boolean isConditionOptimizedTrue = cst == null ? true : cst != Constant.NotAConstant && cst.booleanValue() == true;
	
	if (isConditionTrue || isConditionOptimizedTrue)
		return this.action == null || !this.action.breaksOut(null);
	if (this.action == null || this.action.breaksOut(null))
		return false;
	return this.action.doesNotCompleteNormally() && !this.action.completesByContinue();
}

@Override
public boolean completesByContinue() {
	return this.action.continuesAtOuterLabel();
}
}