ForeachStatement.java

/*******************************************************************************
 * Copyright (c) 2000, 2010 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
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.BranchLabel;
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.flow.LoopingFlowContext;
import org.eclipse.jdt.internal.compiler.flow.UnconditionalFlowInfo;
import org.eclipse.jdt.internal.compiler.impl.Constant;
import org.eclipse.jdt.internal.compiler.lookup.ArrayBinding;
import org.eclipse.jdt.internal.compiler.lookup.Binding;
import org.eclipse.jdt.internal.compiler.lookup.BlockScope;
import org.eclipse.jdt.internal.compiler.lookup.LocalVariableBinding;
import org.eclipse.jdt.internal.compiler.lookup.ParameterizedTypeBinding;
import org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding;
import org.eclipse.jdt.internal.compiler.lookup.TypeBinding;

public class ForeachStatement extends Statement {

	public LocalDeclaration elementVariable;

	public int elementVariableImplicitWidening= -1;

	public Expression collection;

	public Statement action;

	// set the kind of foreach
	private int kind;

	// possible kinds of iterating behavior
	private static final int ARRAY= 0;

	private static final int RAW_ITERABLE= 1;

	private static final int GENERIC_ITERABLE= 2;

	private TypeBinding iteratorReceiverType;

	private TypeBinding collectionElementType;

	// loop labels
	private BranchLabel breakLabel;

	private BranchLabel continueLabel;

	public BlockScope scope;

	// secret variables for codegen
	public LocalVariableBinding indexVariable;

	public LocalVariableBinding collectionVariable; // to store the collection expression value

	public LocalVariableBinding maxVariable;

	// secret variable names
	private static final char[] SecretIteratorVariableName= " iterator".toCharArray(); //$NON-NLS-1$

	private static final char[] SecretIndexVariableName= " index".toCharArray(); //$NON-NLS-1$

	private static final char[] SecretCollectionVariableName= " collection".toCharArray(); //$NON-NLS-1$

	private static final char[] SecretMaxVariableName= " max".toCharArray(); //$NON-NLS-1$

	int postCollectionInitStateIndex= -1;

	int mergedInitStateIndex= -1;

	public ForeachStatement(
			LocalDeclaration elementVariable,
			int start) {

		this.elementVariable= elementVariable;
		this.sourceStart= start;
		this.kind= -1;
	}

	public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
		// initialize break and continue labels
		this.breakLabel= new BranchLabel();
		this.continueLabel= new BranchLabel();
		int initialComplaintLevel= (flowInfo.reachMode() & FlowInfo.UNREACHABLE) != 0 ? Statement.COMPLAINED_FAKE_REACHABLE : Statement.NOT_COMPLAINED;

		// process the element variable and collection
		this.collection.checkNPE(currentScope, flowContext, flowInfo);
		flowInfo= this.elementVariable.analyseCode(this.scope, flowContext, flowInfo);
		FlowInfo condInfo= this.collection.analyseCode(this.scope, flowContext, flowInfo.copy());

		// element variable will be assigned when iterating
		condInfo.markAsDefinitelyAssigned(this.elementVariable.binding);

		this.postCollectionInitStateIndex= currentScope.methodScope().recordInitializationStates(condInfo);

		// process the action
		LoopingFlowContext loopingContext=
				new LoopingFlowContext(flowContext, flowInfo, this, this.breakLabel,
						this.continueLabel, this.scope);
		UnconditionalFlowInfo actionInfo=
				condInfo.nullInfoLessUnconditionalCopy();
		actionInfo.markAsDefinitelyUnknown(this.elementVariable.binding);
		FlowInfo exitBranch;
		if (!(this.action == null || (this.action.isEmptyBlock() && currentScope.compilerOptions().complianceLevel <= ClassFileConstants.JDK1_3))) {

			if (this.action.complainIfUnreachable(actionInfo, this.scope, initialComplaintLevel) < Statement.COMPLAINED_UNREACHABLE) {
				actionInfo= this.action.analyseCode(this.scope, loopingContext, actionInfo).unconditionalCopy();
			}

			// code generation can be optimized when no need to continue in the loop
			exitBranch= flowInfo.unconditionalCopy().
					addInitializationsFrom(condInfo.initsWhenFalse());
			// TODO (maxime) no need to test when false: can optimize (same for action being unreachable above)
			if ((actionInfo.tagBits & loopingContext.initsOnContinue.tagBits & FlowInfo.UNREACHABLE) != 0) {
				this.continueLabel= null;
			} else {
				actionInfo= actionInfo.mergedWith(loopingContext.initsOnContinue);
				loopingContext.complainOnDeferredFinalChecks(this.scope, actionInfo);
				exitBranch.addPotentialInitializationsFrom(actionInfo);
			}
		} else {
			exitBranch= condInfo.initsWhenFalse();
		}

		// we need the variable to iterate the collection even if the
		// element variable is not used
		final boolean hasEmptyAction= this.action == null
				|| this.action.isEmptyBlock()
				|| ((this.action.bits & IsUsefulEmptyStatement) != 0);

		switch (this.kind) {
			case ARRAY:
				if (!hasEmptyAction
						|| this.elementVariable.binding.resolvedPosition != -1) {
					this.collectionVariable.useFlag= LocalVariableBinding.USED;
					if (this.continueLabel != null) {
						this.indexVariable.useFlag= LocalVariableBinding.USED;
						this.maxVariable.useFlag= LocalVariableBinding.USED;
					}
				}
				break;
			case RAW_ITERABLE:
			case GENERIC_ITERABLE:
				this.indexVariable.useFlag= LocalVariableBinding.USED;
				break;
		}
		//end of loop
		loopingContext.complainOnDeferredNullChecks(currentScope, actionInfo);

		FlowInfo mergedInfo= FlowInfo.mergedOptimizedBranches(
				(loopingContext.initsOnBreak.tagBits &
						FlowInfo.UNREACHABLE) != 0 ?
								loopingContext.initsOnBreak :
									flowInfo.addInitializationsFrom(loopingContext.initsOnBreak), // recover upstream null info
				false,
									exitBranch,
									false,
									true /*for(;;){}while(true); unreachable(); */);
		this.mergedInitStateIndex= currentScope.methodScope().recordInitializationStates(mergedInfo);
		return mergedInfo;
	}

	/**
	 * For statement code generation
	 * 
	 * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
	 * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
	 */
	public void generateCode(BlockScope currentScope, CodeStream codeStream) {

		if ((this.bits & IsReachable) == 0) {
			return;
		}
		int pc= codeStream.position;
		final boolean hasEmptyAction= this.action == null
				|| this.action.isEmptyBlock()
				|| ((this.action.bits & IsUsefulEmptyStatement) != 0);

		if (hasEmptyAction
				&& this.elementVariable.binding.resolvedPosition == -1
				&& this.kind == ARRAY) {
			this.collection.generateCode(this.scope, codeStream, false);
			codeStream.exitUserScope(this.scope);
			if (this.mergedInitStateIndex != -1) {
				codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
				codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
			}
			codeStream.recordPositionsFrom(pc, this.sourceStart);
			return;
		}

		// generate the initializations
		switch (this.kind) {
			case ARRAY:
				this.collection.generateCode(this.scope, codeStream, true);
				codeStream.store(this.collectionVariable, true);
				codeStream.addVariable(this.collectionVariable);
				if (this.continueLabel != null) {
					// int length = (collectionVariable = [collection]).length;
					codeStream.arraylength();
					codeStream.store(this.maxVariable, false);
					codeStream.addVariable(this.maxVariable);
					codeStream.iconst_0();
					codeStream.store(this.indexVariable, false);
					codeStream.addVariable(this.indexVariable);
				} else {
					// leave collectionVariable on execution stack (will be consumed when swapping condition further down)
				}
				break;
			case RAW_ITERABLE:
			case GENERIC_ITERABLE:
				this.collection.generateCode(this.scope, codeStream, true);
				// declaringClass.iterator();
				codeStream.invokeIterableIterator(this.iteratorReceiverType);
				codeStream.store(this.indexVariable, false);
				codeStream.addVariable(this.indexVariable);
				break;
		}
		// label management
		BranchLabel actionLabel= new BranchLabel(codeStream);
		actionLabel.tagBits|= BranchLabel.USED;
		BranchLabel conditionLabel= new BranchLabel(codeStream);
		conditionLabel.tagBits|= BranchLabel.USED;
		this.breakLabel.initialize(codeStream);
		if (this.continueLabel == null) {
			// generate the condition (swapped for optimizing)
			conditionLabel.place();
			int conditionPC= codeStream.position;
			switch (this.kind) {
				case ARRAY:
					// inline the arraylength call
					// collectionVariable is already on execution stack
					codeStream.arraylength();
					codeStream.ifeq(this.breakLabel);
					break;
				case RAW_ITERABLE:
				case GENERIC_ITERABLE:
					codeStream.load(this.indexVariable);
					codeStream.invokeJavaUtilIteratorHasNext();
					codeStream.ifeq(this.breakLabel);
					break;
			}
			codeStream.recordPositionsFrom(conditionPC, this.elementVariable.sourceStart);
		} else {
			this.continueLabel.initialize(codeStream);
			this.continueLabel.tagBits|= BranchLabel.USED;
			// jump over the actionBlock
			codeStream.goto_(conditionLabel);
		}

		// generate the loop action
		actionLabel.place();

		// generate the loop action
		switch (this.kind) {
			case ARRAY:
				if (this.elementVariable.binding.resolvedPosition != -1) {
					codeStream.load(this.collectionVariable);
					if (this.continueLabel == null) {
						codeStream.iconst_0(); // no continue, thus simply hardcode offset 0
					} else {
						codeStream.load(this.indexVariable);
					}
					codeStream.arrayAt(this.collectionElementType.id);
					if (this.elementVariableImplicitWidening != -1) {
						codeStream.generateImplicitConversion(this.elementVariableImplicitWidening);
					}
					codeStream.store(this.elementVariable.binding, false);
					codeStream.addVisibleLocalVariable(this.elementVariable.binding);
					if (this.postCollectionInitStateIndex != -1) {
						codeStream.addDefinitelyAssignedVariables(
								currentScope,
								this.postCollectionInitStateIndex);
					}
				}
				break;
			case RAW_ITERABLE:
			case GENERIC_ITERABLE:
				codeStream.load(this.indexVariable);
				codeStream.invokeJavaUtilIteratorNext();
				if (this.elementVariable.binding.type.id != T_JavaLangObject) {
					if (this.elementVariableImplicitWidening != -1) {
						codeStream.checkcast(this.collectionElementType);
						codeStream.generateImplicitConversion(this.elementVariableImplicitWidening);
					} else {
						codeStream.checkcast(this.elementVariable.binding.type);
					}
				}
				if (this.elementVariable.binding.resolvedPosition == -1) {
					codeStream.pop();
				} else {
					codeStream.store(this.elementVariable.binding, false);
					codeStream.addVisibleLocalVariable(this.elementVariable.binding);
					if (this.postCollectionInitStateIndex != -1) {
						codeStream.addDefinitelyAssignedVariables(
								currentScope,
								this.postCollectionInitStateIndex);
					}
				}
				break;
		}

		if (!hasEmptyAction) {
			this.action.generateCode(this.scope, codeStream);
		}
		codeStream.removeVariable(this.elementVariable.binding);
		if (this.postCollectionInitStateIndex != -1) {
			codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.postCollectionInitStateIndex);
		}
		// continuation point
		if (this.continueLabel != null) {
			this.continueLabel.place();
			int continuationPC= codeStream.position;
			// generate the increments for next iteration
			switch (this.kind) {
				case ARRAY:
					if (!hasEmptyAction || this.elementVariable.binding.resolvedPosition >= 0) {
						codeStream.iinc(this.indexVariable.resolvedPosition, 1);
					}
					// generate the condition
					conditionLabel.place();
					codeStream.load(this.indexVariable);
					codeStream.load(this.maxVariable);
					codeStream.if_icmplt(actionLabel);
					break;
				case RAW_ITERABLE:
				case GENERIC_ITERABLE:
					// generate the condition
					conditionLabel.place();
					codeStream.load(this.indexVariable);
					codeStream.invokeJavaUtilIteratorHasNext();
					codeStream.ifne(actionLabel);
					break;
			}
			codeStream.recordPositionsFrom(continuationPC, this.elementVariable.sourceStart);
		}
		switch (this.kind) {
			case ARRAY:
				codeStream.removeVariable(this.indexVariable);
				codeStream.removeVariable(this.maxVariable);
				codeStream.removeVariable(this.collectionVariable);
				break;
			case RAW_ITERABLE:
			case GENERIC_ITERABLE:
				// generate the condition
				codeStream.removeVariable(this.indexVariable);
				break;
		}
		codeStream.exitUserScope(this.scope);
		if (this.mergedInitStateIndex != -1) {
			codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
			codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
		}
		this.breakLabel.place();
		codeStream.recordPositionsFrom(pc, this.sourceStart);
	}

	public StringBuffer printStatement(int indent, StringBuffer output) {

		printIndent(indent, output).append("for ("); //$NON-NLS-1$
		this.elementVariable.printAsExpression(0, output);
		output.append(" : ");//$NON-NLS-1$
		if (this.collection != null) {
			this.collection.print(0, output).append(") "); //$NON-NLS-1$
		} else {
			output.append(')');
		}
		//block
		if (this.action == null) {
			output.append(';');
		} else {
			output.append('\n');
			this.action.printStatement(indent + 1, output);
		}
		return output;
	}

	public void resolve(BlockScope upperScope) {
		// use the scope that will hold the init declarations
		this.scope= new BlockScope(upperScope);
		this.elementVariable.resolve(this.scope); // collection expression can see itemVariable
		TypeBinding elementType= this.elementVariable.type.resolvedType;
		TypeBinding collectionType= this.collection == null ? null : this.collection.resolveType(this.scope);

		TypeBinding expectedCollectionType= null;
		if (elementType != null && collectionType != null) {
			boolean isTargetJsr14= this.scope.compilerOptions().targetJDK == ClassFileConstants.JDK1_4;
			if (collectionType.isArrayType()) { // for(E e : E[])
				this.kind= ARRAY;
				this.collectionElementType= ((ArrayBinding)collectionType).elementsType();
				if (!this.collectionElementType.isCompatibleWith(elementType)
						&& !this.scope.isBoxingCompatibleWith(this.collectionElementType, elementType)) {
					this.scope.problemReporter().notCompatibleTypesErrorInForeach(this.collection, this.collectionElementType, elementType);
				}
				// in case we need to do a conversion
				int compileTimeTypeID= this.collectionElementType.id;
				if (elementType.isBaseType()) {
					this.collection.computeConversion(this.scope, collectionType, collectionType);
					if (!this.collectionElementType.isBaseType()) {
						compileTimeTypeID= this.scope.environment().computeBoxingType(this.collectionElementType).id;
						this.elementVariableImplicitWidening= UNBOXING;
						if (elementType.isBaseType()) {
							this.elementVariableImplicitWidening|= (elementType.id << 4) + compileTimeTypeID;
							this.scope.problemReporter().autoboxing(this.collection, this.collectionElementType, elementType);
						}
					} else {
						this.elementVariableImplicitWidening= (elementType.id << 4) + compileTimeTypeID;
					}
				} else if (this.collectionElementType.isBaseType()) {
					this.collection.computeConversion(this.scope, collectionType, collectionType);
					int boxedID= this.scope.environment().computeBoxingType(this.collectionElementType).id;
					this.elementVariableImplicitWidening= BOXING | (compileTimeTypeID << 4) | compileTimeTypeID; // use primitive type in implicit conversion
					compileTimeTypeID= boxedID;
					this.scope.problemReporter().autoboxing(this.collection, this.collectionElementType, elementType);
				} else {
					expectedCollectionType= upperScope.createArrayType(elementType, 1);
					this.collection.computeConversion(this.scope, expectedCollectionType, collectionType);
				}
			} else if (collectionType instanceof ReferenceBinding) {
				ReferenceBinding iterableType= ((ReferenceBinding)collectionType).findSuperTypeOriginatingFrom(T_JavaLangIterable, false /*Iterable is not a class*/);
				if (iterableType == null && isTargetJsr14) {
					iterableType= ((ReferenceBinding)collectionType).findSuperTypeOriginatingFrom(T_JavaUtilCollection, false /*Iterable is not a class*/);
				}
				checkIterable: {
					if (iterableType == null)
						break checkIterable;

					this.iteratorReceiverType= collectionType.erasure();
					if (isTargetJsr14) {
						if (((ReferenceBinding)this.iteratorReceiverType).findSuperTypeOriginatingFrom(T_JavaUtilCollection, false) == null) {
							this.iteratorReceiverType= iterableType; // handle indirect inheritance thru variable secondary bound
							this.collection.computeConversion(this.scope, iterableType, collectionType);
						} else {
							this.collection.computeConversion(this.scope, collectionType, collectionType);
						}
					} else if (((ReferenceBinding)this.iteratorReceiverType).findSuperTypeOriginatingFrom(T_JavaLangIterable, false) == null) {
						this.iteratorReceiverType= iterableType; // handle indirect inheritance thru variable secondary bound
						this.collection.computeConversion(this.scope, iterableType, collectionType);
					} else {
						this.collection.computeConversion(this.scope, collectionType, collectionType);
					}

					TypeBinding[] arguments= null;
					switch (iterableType.kind()) {
						case Binding.RAW_TYPE: // for(Object o : Iterable)
							this.kind= RAW_ITERABLE;
							this.collectionElementType= this.scope.getJavaLangObject();
							if (!this.collectionElementType.isCompatibleWith(elementType)
									&& !this.scope.isBoxingCompatibleWith(this.collectionElementType, elementType)) {
								this.scope.problemReporter().notCompatibleTypesErrorInForeach(this.collection, this.collectionElementType, elementType);
							}
							// no conversion needed as only for reference types
							break checkIterable;

						case Binding.GENERIC_TYPE: // for (T t : Iterable<T>) - in case used inside Iterable itself
							arguments= iterableType.typeVariables();
							break;

						case Binding.PARAMETERIZED_TYPE: // for(E e : Iterable<E>)
							arguments= ((ParameterizedTypeBinding)iterableType).arguments;
							break;

						default:
							break checkIterable;
					}
					// generic or parameterized case
					if (arguments.length != 1)
						break checkIterable; // per construction can only be one
					this.kind= GENERIC_ITERABLE;

					this.collectionElementType= arguments[0];
					if (!this.collectionElementType.isCompatibleWith(elementType)
							&& !this.scope.isBoxingCompatibleWith(this.collectionElementType, elementType)) {
						this.scope.problemReporter().notCompatibleTypesErrorInForeach(this.collection, this.collectionElementType, elementType);
					}
					int compileTimeTypeID= this.collectionElementType.id;
					// no conversion needed as only for reference types
					if (elementType.isBaseType()) {
						if (!this.collectionElementType.isBaseType()) {
							compileTimeTypeID= this.scope.environment().computeBoxingType(this.collectionElementType).id;
							this.elementVariableImplicitWidening= UNBOXING;
							if (elementType.isBaseType()) {
								this.elementVariableImplicitWidening|= (elementType.id << 4) + compileTimeTypeID;
							}
						} else {
							this.elementVariableImplicitWidening= (elementType.id << 4) + compileTimeTypeID;
						}
					} else {
						if (this.collectionElementType.isBaseType()) {
							this.elementVariableImplicitWidening= BOXING | (compileTimeTypeID << 4) | compileTimeTypeID; // use primitive type in implicit conversion
						}
					}
				}
			}
			switch (this.kind) {
				case ARRAY:
					// allocate #index secret variable (of type int)
					this.indexVariable= new LocalVariableBinding(SecretIndexVariableName, TypeBinding.INT, ClassFileConstants.AccDefault, false);
					this.scope.addLocalVariable(this.indexVariable);
					this.indexVariable.setConstant(Constant.NotAConstant); // not inlinable
					// allocate #max secret variable
					this.maxVariable= new LocalVariableBinding(SecretMaxVariableName, TypeBinding.INT, ClassFileConstants.AccDefault, false);
					this.scope.addLocalVariable(this.maxVariable);
					this.maxVariable.setConstant(Constant.NotAConstant); // not inlinable
					// add #array secret variable (of collection type)
					if (expectedCollectionType == null) {
						this.collectionVariable= new LocalVariableBinding(SecretCollectionVariableName, collectionType, ClassFileConstants.AccDefault, false);
					} else {
						this.collectionVariable= new LocalVariableBinding(SecretCollectionVariableName, expectedCollectionType, ClassFileConstants.AccDefault, false);
					}
					this.scope.addLocalVariable(this.collectionVariable);
					this.collectionVariable.setConstant(Constant.NotAConstant); // not inlinable
					break;
				case RAW_ITERABLE:
				case GENERIC_ITERABLE:
					// allocate #index secret variable (of type Iterator)
					this.indexVariable= new LocalVariableBinding(SecretIteratorVariableName, this.scope.getJavaUtilIterator(), ClassFileConstants.AccDefault, false);
					this.scope.addLocalVariable(this.indexVariable);
					this.indexVariable.setConstant(Constant.NotAConstant); // not inlinable
					break;
				default:
					if (isTargetJsr14) {
						this.scope.problemReporter().invalidTypeForCollectionTarget14(this.collection);
					} else {
						this.scope.problemReporter().invalidTypeForCollection(this.collection);
					}
			}
		}
		if (this.action != null) {
			this.action.resolve(this.scope);
		}
	}

	public void traverse(
			ASTVisitor visitor,
			BlockScope blockScope) {

		if (visitor.visit(this, blockScope)) {
			this.elementVariable.traverse(visitor, this.scope);
			if (this.collection != null) {
				this.collection.traverse(visitor, this.scope);
			}
			if (this.action != null) {
				this.action.traverse(visitor, this.scope);
			}
		}
		visitor.endVisit(this, blockScope);
	}
}