src/org/eclipse/jdt/internal/compiler/ast/ReturnStatement.java

   1 /*******************************************************************************
   2  * Copyright (c) 2000, 2004 IBM Corporation and others.
   3  * All rights reserved. This program and the accompanying materials
   4  * are made available under the terms of the Common Public License v1.0
   5  * which accompanies this distribution, and is available at
   6  * http://www.eclipse.org/legal/cpl-v10.html
   7  *
   8  * Contributors:
   9  *     IBM Corporation - initial API and implementation
  10  *******************************************************************************/
  11 package org.eclipse.jdt.internal.compiler.ast;
  12
  13 import org.eclipse.jdt.internal.compiler.ASTVisitor;
  14 import org.eclipse.jdt.internal.compiler.codegen.*;
  15 import org.eclipse.jdt.internal.compiler.flow.*;
  16 import org.eclipse.jdt.internal.compiler.lookup.*;
  17
  18 public class ReturnStatement extends Statement {
  19
  20         public Expression expression;
  21         public TypeBinding expressionType;
  22         public boolean isSynchronized;
  23         public SubRoutineStatement[] subroutines;
  24         public boolean isAnySubRoutineEscaping = false;
  25         public LocalVariableBinding saveValueVariable;
  26
  27         public ReturnStatement(Expression expr, int s, int e ) {
  28                 sourceStart = s;
  29                 sourceEnd = e;
  30                 expression = expr ;
  31         }
  32         public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {      // here requires to generate a sequence of finally blocks invocations depending corresponding
  33                 // to each of the traversed try statements, so that execution will terminate properly.
  34
  35                 // lookup the label, this should answer the returnContext
  36
  37                 if (expression != null) {
  38                         flowInfo = expression.analyseCode(currentScope, flowContext, flowInfo);
  39                 }
  40                 // compute the return sequence (running the finally blocks)
  41                 FlowContext traversedContext = flowContext;
  42                 int subIndex = 0, maxSub = 5;
  43                 boolean saveValueNeeded = false;
  44                 boolean hasValueToSave = expression != null && expression.constant == NotAConstant;
  45                 do {
  46                         SubRoutineStatement sub;
  47                         if ((sub = traversedContext.subRoutine()) != null) {
  48                                 if (this.subroutines == null){
  49                                         this.subroutines = new SubRoutineStatement[maxSub];
  50                                 }
  51                                 if (subIndex == maxSub) {
  52                                         System.arraycopy(this.subroutines, 0, (this.subroutines = new SubRoutineStatement[maxSub *= 2]), 0, subIndex); // grow
  53                                 }
  54                                 this.subroutines[subIndex++] = sub;
  55                                 if (sub.isSubRoutineEscaping()) {
  56                                         saveValueNeeded = false;
  57                                         isAnySubRoutineEscaping = true;
  58                                         break;
  59                                 }
  60                         }
  61                         traversedContext.recordReturnFrom(flowInfo.unconditionalInits());
  62
  63                         ASTNode node;
  64                         if ((node = traversedContext.associatedNode) instanceof SynchronizedStatement) {
  65                                 isSynchronized = true;
  66
  67                         } else if (node instanceof TryStatement) {
  68                                 TryStatement tryStatement = (TryStatement) node;
  69                                 flowInfo.addInitializationsFrom(tryStatement.subRoutineInits); // collect inits
  70                                 if (hasValueToSave) {
  71                                         if (this.saveValueVariable == null){ // closest subroutine secret variable is used
  72                                                 prepareSaveValueLocation(tryStatement);
  73                                         }
  74                                         saveValueNeeded = true;
  75                                 }
  76
  77                         } else if (traversedContext instanceof InitializationFlowContext) {
  78                                         currentScope.problemReporter().cannotReturnInInitializer(this);
  79                                         return FlowInfo.DEAD_END;
  80                         }
  81                 } while ((traversedContext = traversedContext.parent) != null);
  82
  83                 // resize subroutines
  84                 if ((subroutines != null) && (subIndex != maxSub)) {
  85                         System.arraycopy(subroutines, 0, (subroutines = new SubRoutineStatement[subIndex]), 0, subIndex);
  86                 }
  87
  88                 // secret local variable for return value (note that this can only occur in a real method)
  89                 if (saveValueNeeded) {
  90                         if (this.saveValueVariable != null) {
  91                                 this.saveValueVariable.useFlag = LocalVariableBinding.USED;
  92                         }
  93                 } else {
  94                         this.saveValueVariable = null;
  95                         if ((!isSynchronized) && (expressionType == BooleanBinding)) {
  96                                 this.expression.bits |= ValueForReturnMASK;
  97                         }
  98                 }
  99                 return FlowInfo.DEAD_END;
 100         }
 101
 102         /**
 103          * Retrun statement code generation
 104          *
 105          *   generate the finallyInvocationSequence.
 106          *
 107          * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 108          * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 109          */
 110         public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 111                 if ((bits & IsReachableMASK) == 0) {
 112                         return;
 113                 }
 114                 int pc = codeStream.position;
 115                 // generate the expression
 116                 if ((expression != null) && (expression.constant == NotAConstant)) {
 117                         expression.generateCode(currentScope, codeStream, needValue()); // no value needed if non-returning subroutine
 118                         generateStoreSaveValueIfNecessary(codeStream);
 119                 }
 120
 121                 // generation of code responsible for invoking the finally blocks in sequence
 122                 if (subroutines != null) {
 123                         for (int i = 0, max = subroutines.length; i < max; i++) {
 124                                 SubRoutineStatement sub = subroutines[i];
 125                                 sub.generateSubRoutineInvocation(currentScope, codeStream);
 126                                 if (sub.isSubRoutineEscaping()) {
 127                                                 codeStream.recordPositionsFrom(pc, this.sourceStart);
 128                                                 SubRoutineStatement.reenterExceptionHandlers(subroutines, i, codeStream);
 129                                                 return;
 130                                 }
 131                                 sub.exitAnyExceptionHandler();
 132                         }
 133                 }
 134                 if (saveValueVariable != null) codeStream.load(saveValueVariable);
 135
 136                 if ((expression != null) && (expression.constant != NotAConstant)) {
 137                         codeStream.generateConstant(expression.constant, expression.implicitConversion);
 138                         generateStoreSaveValueIfNecessary(codeStream);
 139                 }
 140                 // output the suitable return bytecode or wrap the value inside a descriptor for doits
 141                 this.generateReturnBytecode(codeStream);
 142                 codeStream.recordPositionsFrom(pc, this.sourceStart);
 143                 SubRoutineStatement.reenterExceptionHandlers(subroutines, -1, codeStream);
 144         }
 145         /**
 146          * Dump the suitable return bytecode for a return statement
 147          *
 148          */
 149         public void generateReturnBytecode(CodeStream codeStream) {
 150
 151                 if (expression == null) {
 152                         codeStream.return_();
 153                 } else {
 154                         switch (expression.implicitConversion >> 4) {
 155                                 case T_boolean :
 156                                 case T_int :
 157                                         codeStream.ireturn();
 158                                         break;
 159                                 case T_float :
 160                                         codeStream.freturn();
 161                                         break;
 162                                 case T_long :
 163                                         codeStream.lreturn();
 164                                         break;
 165                                 case T_double :
 166                                         codeStream.dreturn();
 167                                         break;
 168                                 default :
 169                                         codeStream.areturn();
 170                         }
 171                 }
 172         }
 173         public void generateStoreSaveValueIfNecessary(CodeStream codeStream){
 174                 if (saveValueVariable != null) codeStream.store(saveValueVariable, false);
 175         }
 176         public boolean needValue(){
 177                 return (subroutines == null) || (saveValueVariable != null) || isSynchronized;
 178         }
 179         public void prepareSaveValueLocation(TryStatement targetTryStatement){
 180
 181                 this.saveValueVariable = targetTryStatement.secretReturnValue;
 182         }
 183         public StringBuffer printStatement(int tab, StringBuffer output){
 184
 185                 printIndent(tab, output).append("return "); //$NON-NLS-1$
 186                 if (expression != null )
 187                         expression.printExpression(0, output) ;
 188                 return output.append(';');
 189         }
 190         public void resolve(BlockScope scope) {
 191                 MethodScope methodScope = scope.methodScope();
 192                 MethodBinding methodBinding;
 193                 TypeBinding methodType =
 194                         (methodScope.referenceContext instanceof AbstractMethodDeclaration)
 195                                 ? ((methodBinding = ((AbstractMethodDeclaration) methodScope.referenceContext).binding) == null
 196                                         ? null
 197                                         : methodBinding.returnType)
 198                                 : VoidBinding;
 199                 if (methodType == VoidBinding) {
 200                         // the expression should be null
 201                         if (expression == null)
 202                                 return;
 203                         if ((expressionType = expression.resolveType(scope)) != null)
 204                                 scope.problemReporter().attemptToReturnNonVoidExpression(this, expressionType);
 205                         return;
 206                 }
 207                 if (expression == null) {
 208                         if (methodType != null) scope.problemReporter().shouldReturn(methodType, this);
 209                         return;
 210                 }
 211                 if ((expressionType = expression.resolveType(scope)) == null)
 212                         return;
 213
 214                 if (methodType != null && expression.isConstantValueOfTypeAssignableToType(expressionType, methodType)) {
 215                         // dealing with constant
 216                         expression.implicitWidening(methodType, expressionType);
 217                         return;
 218                 }
 219                 if (expressionType == VoidBinding) {
 220                         scope.problemReporter().attemptToReturnVoidValue(this);
 221                         return;
 222                 }
 223                 if (methodType != null && expressionType.isCompatibleWith(methodType)) {
 224                         expression.implicitWidening(methodType, expressionType);
 225                         return;
 226                 }
 227                 if (methodType != null){
 228                         scope.problemReporter().typeMismatchErrorActualTypeExpectedType(expression, expressionType, methodType);
 229                 }
 230         }
 231         public void traverse(ASTVisitor visitor, BlockScope scope) {
 232                 if (visitor.visit(this, scope)) {
 233                         if (expression != null)
 234                                 expression.traverse(visitor, scope);
 235                 }
 236                 visitor.endVisit(this, scope);
 237         }
 238 }