net.sourceforge.phpeclipse/src/net/sourceforge/phpdt/internal/compiler/ast/ReturnStatement.java

   1 /*******************************************************************************
   2  * Copyright (c) 2000, 2001, 2002 International Business Machines Corp. and others.
   3  * All rights reserved. This program and the accompanying materials
   4  * are made available under the terms of the Common Public License v0.5
   5  * which accompanies this distribution, and is available at
   6  * http://www.eclipse.org/legal/cpl-v05.html
   7  *
   8  * Contributors:
   9  *     IBM Corporation - initial API and implementation
  10  ******************************************************************************/
  11 package net.sourceforge.phpdt.internal.compiler.ast;
  12
  13 import net.sourceforge.phpdt.internal.compiler.IAbstractSyntaxTreeVisitor;
  14 import net.sourceforge.phpdt.internal.compiler.codegen.*;
  15 import net.sourceforge.phpdt.internal.compiler.flow.*;
  16 import net.sourceforge.phpdt.internal.compiler.lookup.*;
  17
  18 public class ReturnStatement extends Statement {
  19         public Expression expression;
  20
  21         public TypeBinding expressionType;
  22         public boolean isSynchronized;
  23         public AstNode[] subroutines;
  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         while (true) {
  45                 AstNode sub;
  46                 if ((sub = traversedContext.subRoutine()) != null) {
  47                         if (this.subroutines == null){
  48                                 this.subroutines = new AstNode[maxSub];
  49                         }
  50                         if (subIndex == maxSub) {
  51                                 System.arraycopy(this.subroutines, 0, (this.subroutines = new AstNode[maxSub *= 2]), 0, subIndex); // grow
  52                         }
  53                         this.subroutines[subIndex++] = sub;
  54                         if (sub.cannotReturn()) {
  55                                 saveValueNeeded = false;
  56                                 break;
  57                         }
  58                 }
  59                 AstNode node;
  60
  61                 if ((node = traversedContext.associatedNode) instanceof SynchronizedStatement) {
  62                         isSynchronized = true;
  63
  64                 } else if (node instanceof TryStatement && hasValueToSave) {
  65                                 if (this.saveValueVariable == null){ // closest subroutine secret variable is used
  66                                         prepareSaveValueLocation((TryStatement)node);
  67                                 }
  68                                 saveValueNeeded = true;
  69
  70                 } else if (traversedContext instanceof InitializationFlowContext) {
  71                                 currentScope.problemReporter().cannotReturnInInitializer(this);
  72                                 return FlowInfo.DeadEnd;
  73                 }
  74
  75                 // remember the initialization at this
  76                 // point for dealing with blank final variables.
  77                 traversedContext.recordReturnFrom(flowInfo.unconditionalInits());
  78
  79                 FlowContext parentContext;
  80                 if ((parentContext = traversedContext.parent) == null) { // top-context
  81                         break;
  82                 } else {
  83                         traversedContext = parentContext;
  84                 }
  85         }
  86         // resize subroutines
  87         if ((subroutines != null) && (subIndex != maxSub)) {
  88                 System.arraycopy(subroutines, 0, (subroutines = new AstNode[subIndex]), 0, subIndex);
  89         }
  90
  91         // secret local variable for return value (note that this can only occur in a real method)
  92         if (saveValueNeeded) {
  93                 if (this.saveValueVariable != null) {
  94                         this.saveValueVariable.used = true;
  95                 }
  96         } else {
  97                 this.saveValueVariable = null;
  98                 if ((!isSynchronized) && (expressionType == BooleanBinding)) {
  99                         this.expression.bits |= ValueForReturnMASK;
 100                 }
 101         }
 102         return FlowInfo.DeadEnd;
 103 }
 104
 105 /**
 106  * Retrun statement code generation
 107  *
 108  *   generate the finallyInvocationSequence.
 109  *
 110  * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 111  * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 112  */
 113 public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 114         if ((bits & IsReachableMASK) == 0) {
 115                 return;
 116         }
 117         int pc = codeStream.position;
 118         // generate the expression
 119         if ((expression != null) && (expression.constant == NotAConstant)) {
 120                 expression.generateCode(currentScope, codeStream, needValue()); // no value needed if non-returning subroutine
 121                 generateStoreSaveValueIfNecessary(currentScope, codeStream);
 122         }
 123
 124         // generation of code responsible for invoking the finally blocks in sequence
 125         if (subroutines != null) {
 126                 for (int i = 0, max = subroutines.length; i < max; i++) {
 127                         AstNode sub;
 128                         if ((sub = subroutines[i]) instanceof SynchronizedStatement) {
 129                                 codeStream.load(((SynchronizedStatement) sub).synchroVariable);
 130                                 codeStream.monitorexit();
 131                         } else {
 132                                 TryStatement trySub = (TryStatement) sub;
 133                                 if (trySub.subRoutineCannotReturn) {
 134                                         codeStream.goto_(trySub.subRoutineStartLabel);
 135                                         codeStream.recordPositionsFrom(pc, this.sourceStart);
 136                                         return;
 137                                 } else {
 138                                         codeStream.jsr(trySub.subRoutineStartLabel);
 139                                 }
 140                         }
 141                 }
 142         }
 143         if (saveValueVariable != null) codeStream.load(saveValueVariable);
 144
 145         if ((expression != null) && (expression.constant != NotAConstant)) {
 146                 codeStream.generateConstant(expression.constant, expression.implicitConversion);
 147                 generateStoreSaveValueIfNecessary(currentScope, codeStream);
 148         }
 149         // output the suitable return bytecode or wrap the value inside a descriptor for doits
 150         this.generateReturnBytecode(currentScope, codeStream);
 151
 152         codeStream.recordPositionsFrom(pc, this.sourceStart);
 153 }
 154 /**
 155  * Dump the suitable return bytecode for a return statement
 156  *
 157  */
 158 public void generateReturnBytecode(BlockScope currentScope, CodeStream codeStream) {
 159
 160         if (expression == null) {
 161                 codeStream.return_();
 162         } else {
 163                 switch (expression.implicitConversion >> 4) {
 164                         case T_boolean :
 165                         case T_int :
 166                                 codeStream.ireturn();
 167                                 break;
 168                         case T_float :
 169                                 codeStream.freturn();
 170                                 break;
 171                         case T_long :
 172                                 codeStream.lreturn();
 173                                 break;
 174                         case T_double :
 175                                 codeStream.dreturn();
 176                                 break;
 177                         default :
 178                                 codeStream.areturn();
 179                 }
 180         }
 181 }
 182 public void generateStoreSaveValueIfNecessary(BlockScope currentScope, CodeStream codeStream){
 183
 184         if (saveValueVariable != null) codeStream.store(saveValueVariable, false);
 185 }
 186 public boolean needValue(){
 187         return (subroutines == null) || (saveValueVariable != null) || isSynchronized;
 188 }
 189 public void prepareSaveValueLocation(TryStatement targetTryStatement){
 190
 191         this.saveValueVariable = targetTryStatement.secretReturnValue;
 192 }
 193 public void resolve(BlockScope scope) {
 194         MethodScope methodScope = scope.methodScope();
 195         MethodBinding methodBinding;
 196         TypeBinding methodType =
 197                 (methodScope.referenceContext instanceof AbstractMethodDeclaration)
 198                         ? ((methodBinding = ((AbstractMethodDeclaration) methodScope.referenceContext).binding) == null
 199                                 ? null
 200                                 : methodBinding.returnType)
 201                         : VoidBinding;
 202         if (methodType == VoidBinding) {
 203                 // the expression should be null
 204                 if (expression == null)
 205                         return;
 206                 if ((expressionType = expression.resolveType(scope)) != null)
 207                         scope.problemReporter().attemptToReturnNonVoidExpression(this, expressionType);
 208                 return;
 209         }
 210         if (expression == null) {
 211                 if (methodType != null) scope.problemReporter().shouldReturn(methodType, this);
 212                 return;
 213         }
 214         if ((expressionType = expression.resolveType(scope)) == null)
 215                 return;
 216
 217         if (methodType != null && expression.isConstantValueOfTypeAssignableToType(expressionType, methodType)) {
 218                 // dealing with constant
 219                 expression.implicitWidening(methodType, expressionType);
 220                 return;
 221         }
 222         if (expressionType == VoidBinding) {
 223                 scope.problemReporter().attemptToReturnVoidValue(this);
 224                 return;
 225         }
 226         if (methodType != null && scope.areTypesCompatible(expressionType, methodType)) {
 227                 expression.implicitWidening(methodType, expressionType);
 228                 return;
 229         }
 230         if (methodType != null){
 231                 scope.problemReporter().typeMismatchErrorActualTypeExpectedType(expression, expressionType, methodType);
 232         }
 233 }
 234 public String toString(int tab){
 235
 236         String s = tabString(tab) ;
 237         s = s + "return "; //$NON-NLS-1$
 238         if (expression != null )
 239                 s = s + expression.toStringExpression() ;
 240         return s;
 241 }
 242 public void traverse(IAbstractSyntaxTreeVisitor visitor, BlockScope scope) {
 243         if (visitor.visit(this, scope)) {
 244                 if (expression != null)
 245                         expression.traverse(visitor, scope);
 246         }
 247         visitor.endVisit(this, scope);
 248 }
 249 }