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 boolean isSynchronized;
  22         public SubRoutineStatement[] subroutines;
  23         public boolean isAnySubRoutineEscaping = false;
  24         public LocalVariableBinding saveValueVariable;
  25
  26         public ReturnStatement(Expression expr, int s, int e ) {
  27                 sourceStart = s;
  28                 sourceEnd = e;
  29                 expression = expr ;
  30         }
  31         public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {      // here requires to generate a sequence of finally blocks invocations depending corresponding
  32                 // to each of the traversed try statements, so that execution will terminate properly.
  33
  34                 // lookup the label, this should answer the returnContext
  35
  36                 if (expression != null) {
  37                         flowInfo = expression.analyseCode(currentScope, flowContext, flowInfo);
  38                 }
  39                 // compute the return sequence (running the finally blocks)
  40                 FlowContext traversedContext = flowContext;
  41                 int subIndex = 0, maxSub = 5;
  42                 boolean saveValueNeeded = false;
  43                 boolean hasValueToSave = expression != null && expression.constant == NotAConstant;
  44                 do {
  45                         SubRoutineStatement sub;
  46                         if ((sub = traversedContext.subRoutine()) != null) {
  47                                 if (this.subroutines == null){
  48                                         this.subroutines = new SubRoutineStatement[maxSub];
  49                                 }
  50                                 if (subIndex == maxSub) {
  51                                         System.arraycopy(this.subroutines, 0, (this.subroutines = new SubRoutineStatement[maxSub *= 2]), 0, subIndex); // grow
  52                                 }
  53                                 this.subroutines[subIndex++] = sub;
  54                                 if (sub.isSubRoutineEscaping()) {
  55                                         saveValueNeeded = false;
  56                                         isAnySubRoutineEscaping = true;
  57                                         break;
  58                                 }
  59                         }
  60                         traversedContext.recordReturnFrom(flowInfo.unconditionalInits());
  61
  62                         ASTNode node;
  63                         if ((node = traversedContext.associatedNode) instanceof SynchronizedStatement) {
  64                                 isSynchronized = true;
  65
  66                         } else if (node instanceof TryStatement) {
  67                                 TryStatement tryStatement = (TryStatement) node;
  68                                 flowInfo.addInitializationsFrom(tryStatement.subRoutineInits); // collect inits
  69                                 if (hasValueToSave) {
  70                                         if (this.saveValueVariable == null){ // closest subroutine secret variable is used
  71                                                 prepareSaveValueLocation(tryStatement);
  72                                         }
  73                                         saveValueNeeded = true;
  74                                 }
  75
  76                         } else if (traversedContext instanceof InitializationFlowContext) {
  77                                         currentScope.problemReporter().cannotReturnInInitializer(this);
  78                                         return FlowInfo.DEAD_END;
  79                         }
  80                 } while ((traversedContext = traversedContext.parent) != null);
  81
  82                 // resize subroutines
  83                 if ((subroutines != null) && (subIndex != maxSub)) {
  84                         System.arraycopy(subroutines, 0, (subroutines = new SubRoutineStatement[subIndex]), 0, subIndex);
  85                 }
  86
  87                 // secret local variable for return value (note that this can only occur in a real method)
  88                 if (saveValueNeeded) {
  89                         if (this.saveValueVariable != null) {
  90                                 this.saveValueVariable.useFlag = LocalVariableBinding.USED;
  91                         }
  92                 } else {
  93                         this.saveValueVariable = null;
  94                         if (!isSynchronized && this.expression != null && this.expression.resolvedType == BooleanBinding) {
  95                                 this.expression.bits |= ValueForReturnMASK;
  96                         }
  97                 }
  98                 return FlowInfo.DEAD_END;
  99         }
 100
 101         /**
 102          * Retrun statement code generation
 103          *
 104          *   generate the finallyInvocationSequence.
 105          *
 106          * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 107          * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 108          */
 109         public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 110                 if ((bits & IsReachableMASK) == 0) {
 111                         return;
 112                 }
 113                 int pc = codeStream.position;
 114                 // generate the expression
 115                 if ((expression != null) && (expression.constant == NotAConstant)) {
 116                         expression.generateCode(currentScope, codeStream, needValue()); // no value needed if non-returning subroutine
 117                         generateStoreSaveValueIfNecessary(codeStream);
 118                 }
 119
 120                 // generation of code responsible for invoking the finally blocks in sequence
 121                 if (subroutines != null) {
 122                         for (int i = 0, max = subroutines.length; i < max; i++) {
 123                                 SubRoutineStatement sub = subroutines[i];
 124                                 sub.generateSubRoutineInvocation(currentScope, codeStream);
 125                                 if (sub.isSubRoutineEscaping()) {
 126                                                 codeStream.recordPositionsFrom(pc, this.sourceStart);
 127                                                 SubRoutineStatement.reenterExceptionHandlers(subroutines, i, codeStream);
 128                                                 return;
 129                                 }
 130                                 sub.exitAnyExceptionHandler();
 131                         }
 132                 }
 133                 if (saveValueVariable != null) codeStream.load(saveValueVariable);
 134
 135                 if ((expression != null) && (expression.constant != NotAConstant)) {
 136                         codeStream.generateConstant(expression.constant, expression.implicitConversion);
 137                         generateStoreSaveValueIfNecessary(codeStream);
 138                 }
 139                 // output the suitable return bytecode or wrap the value inside a descriptor for doits
 140                 this.generateReturnBytecode(codeStream);
 141                 codeStream.recordPositionsFrom(pc, this.sourceStart);
 142                 SubRoutineStatement.reenterExceptionHandlers(subroutines, -1, codeStream);
 143         }
 144         /**
 145          * Dump the suitable return bytecode for a return statement
 146          *
 147          */
 148         public void generateReturnBytecode(CodeStream codeStream) {
 149
 150                 if (expression == null) {
 151                         codeStream.return_();
 152                 } else {
 153                         final int implicitConversion = expression.implicitConversion;
 154                         if ((implicitConversion & BOXING) != 0) {
 155                                 codeStream.areturn();
 156                                 return;
 157                         }
 158                         int runtimeType = (implicitConversion & IMPLICIT_CONVERSION_MASK) >> 4;
 159                         switch (runtimeType) {
 160                                 case T_boolean :
 161                                 case T_int :
 162                                         codeStream.ireturn();
 163                                         break;
 164                                 case T_float :
 165                                         codeStream.freturn();
 166                                         break;
 167                                 case T_long :
 168                                         codeStream.lreturn();
 169                                         break;
 170                                 case T_double :
 171                                         codeStream.dreturn();
 172                                         break;
 173                                 default :
 174                                         codeStream.areturn();
 175                         }
 176                 }
 177         }
 178         public void generateStoreSaveValueIfNecessary(CodeStream codeStream){
 179                 if (saveValueVariable != null) codeStream.store(saveValueVariable, false);
 180         }
 181         public boolean needValue(){
 182                 return (subroutines == null) || (saveValueVariable != null) || isSynchronized;
 183         }
 184         public void prepareSaveValueLocation(TryStatement targetTryStatement){
 185
 186                 this.saveValueVariable = targetTryStatement.secretReturnValue;
 187         }
 188         public StringBuffer printStatement(int tab, StringBuffer output){
 189
 190                 printIndent(tab, output).append("return "); //$NON-NLS-1$
 191                 if (expression != null )
 192                         expression.printExpression(0, output) ;
 193                 return output.append(';');
 194         }
 195
 196         public void resolve(BlockScope scope) {
 197
 198                 MethodScope methodScope = scope.methodScope();
 199                 MethodBinding methodBinding;
 200                 TypeBinding methodType =
 201                         (methodScope.referenceContext instanceof AbstractMethodDeclaration)
 202                                 ? ((methodBinding = ((AbstractMethodDeclaration) methodScope.referenceContext).binding) == null
 203                                         ? null
 204                                         : methodBinding.returnType)
 205                                 : VoidBinding;
 206                 TypeBinding expressionType;
 207                 if (methodType == VoidBinding) {
 208                         // the expression should be null
 209                         if (expression == null)
 210                                 return;
 211                         if ((expressionType = expression.resolveType(scope)) != null)
 212                                 scope.problemReporter().attemptToReturnNonVoidExpression(this, expressionType);
 213                         return;
 214                 }
 215                 if (expression == null) {
 216                         if (methodType != null) scope.problemReporter().shouldReturn(methodType, this);
 217                         return;
 218                 }
 219                 expression.setExpectedType(methodType); // needed in case of generic method invocation
 220                 if ((expressionType = expression.resolveType(scope)) == null) return;
 221                 if (expressionType == VoidBinding) {
 222                         scope.problemReporter().attemptToReturnVoidValue(this);
 223                         return;
 224                 }
 225                 if (methodType == null)
 226                         return;
 227
 228                 if (methodType != expressionType) // must call before computeConversion() and typeMismatchError()
 229                         scope.compilationUnitScope().recordTypeConversion(methodType, expressionType);
 230                 if (expression.isConstantValueOfTypeAssignableToType(expressionType, methodType)
 231                                 || expressionType.isCompatibleWith(methodType)) {
 232
 233                         expression.computeConversion(scope, methodType, expressionType);
 234                         if (expressionType.needsUncheckedConversion(methodType)) {
 235                             scope.problemReporter().unsafeRawConversion(this.expression, expressionType, methodType);
 236                         }
 237                         return;
 238                 } else if (scope.isBoxingCompatibleWith(expressionType, methodType)) {
 239                         expression.computeConversion(scope, methodType, expressionType);
 240                         return;
 241                 }
 242                 scope.problemReporter().typeMismatchError(expressionType, methodType, expression);
 243         }
 244         public void traverse(ASTVisitor visitor, BlockScope scope) {
 245                 if (visitor.visit(this, scope)) {
 246                         if (expression != null)
 247                                 expression.traverse(visitor, scope);
 248                 }
 249                 visitor.endVisit(this, scope);
 250         }
 251 }