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.CodeStream;
  15 import net.sourceforge.phpdt.internal.compiler.flow.FlowContext;
  16 import net.sourceforge.phpdt.internal.compiler.flow.FlowInfo;
  17 import net.sourceforge.phpdt.internal.compiler.flow.InitializationFlowContext;
  18 import net.sourceforge.phpdt.internal.compiler.lookup.BlockScope;
  19 import net.sourceforge.phpdt.internal.compiler.lookup.LocalVariableBinding;
  20 import net.sourceforge.phpdt.internal.compiler.lookup.MethodBinding;
  21 import net.sourceforge.phpdt.internal.compiler.lookup.MethodScope;
  22 import net.sourceforge.phpdt.internal.compiler.lookup.TypeBinding;
  23
  24 public class ReturnStatement extends Statement {
  25         public Expression expression;
  26
  27         public TypeBinding expressionType;
  28         public boolean isSynchronized;
  29         public AstNode[] subroutines;
  30         public LocalVariableBinding saveValueVariable;
  31
  32 public ReturnStatement(Expression expr, int s, int e ) {
  33         sourceStart = s;
  34         sourceEnd = e;
  35         expression = expr ;
  36 }
  37 public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {      // here requires to generate a sequence of finally blocks invocations depending corresponding
  38         // to each of the traversed try statements, so that execution will terminate properly.
  39
  40         // lookup the label, this should answer the returnContext
  41
  42         if (expression != null) {
  43                 flowInfo = expression.analyseCode(currentScope, flowContext, flowInfo);
  44         }
  45         // compute the return sequence (running the finally blocks)
  46         FlowContext traversedContext = flowContext;
  47         int subIndex = 0, maxSub = 5;
  48         boolean saveValueNeeded = false;
  49         boolean hasValueToSave = expression != null && expression.constant == NotAConstant;
  50         while (true) {
  51                 AstNode sub;
  52                 if ((sub = traversedContext.subRoutine()) != null) {
  53                         if (this.subroutines == null){
  54                                 this.subroutines = new AstNode[maxSub];
  55                         }
  56                         if (subIndex == maxSub) {
  57                                 System.arraycopy(this.subroutines, 0, (this.subroutines = new AstNode[maxSub *= 2]), 0, subIndex); // grow
  58                         }
  59                         this.subroutines[subIndex++] = sub;
  60                         if (sub.cannotReturn()) {
  61                                 saveValueNeeded = false;
  62                                 break;
  63                         }
  64                 }
  65                 AstNode node;
  66
  67                 if ((node = traversedContext.associatedNode) instanceof SynchronizedStatement) {
  68                         isSynchronized = true;
  69
  70                 } else if (node instanceof TryStatement && hasValueToSave) {
  71                                 if (this.saveValueVariable == null){ // closest subroutine secret variable is used
  72                                         prepareSaveValueLocation((TryStatement)node);
  73                                 }
  74                                 saveValueNeeded = true;
  75
  76                 } else if (traversedContext instanceof InitializationFlowContext) {
  77                                 currentScope.problemReporter().cannotReturnInInitializer(this);
  78                                 return FlowInfo.DeadEnd;
  79                 }
  80
  81                 // remember the initialization at this
  82                 // point for dealing with blank final variables.
  83                 traversedContext.recordReturnFrom(flowInfo.unconditionalInits());
  84
  85                 FlowContext parentContext;
  86                 if ((parentContext = traversedContext.parent) == null) { // top-context
  87                         break;
  88                 } else {
  89                         traversedContext = parentContext;
  90                 }
  91         }
  92         // resize subroutines
  93         if ((subroutines != null) && (subIndex != maxSub)) {
  94                 System.arraycopy(subroutines, 0, (subroutines = new AstNode[subIndex]), 0, subIndex);
  95         }
  96
  97         // secret local variable for return value (note that this can only occur in a real method)
  98         if (saveValueNeeded) {
  99                 if (this.saveValueVariable != null) {
 100                         this.saveValueVariable.used = true;
 101                 }
 102         } else {
 103                 this.saveValueVariable = null;
 104                 if ((!isSynchronized) && (expressionType == BooleanBinding)) {
 105                         this.expression.bits |= ValueForReturnMASK;
 106                 }
 107         }
 108         return FlowInfo.DeadEnd;
 109 }
 110
 111 /**
 112  * Retrun statement code generation
 113  *
 114  *   generate the finallyInvocationSequence.
 115  *
 116  * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 117  * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 118  */
 119 public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 120         if ((bits & IsReachableMASK) == 0) {
 121                 return;
 122         }
 123         int pc = codeStream.position;
 124         // generate the expression
 125         if ((expression != null) && (expression.constant == NotAConstant)) {
 126                 expression.generateCode(currentScope, codeStream, needValue()); // no value needed if non-returning subroutine
 127                 generateStoreSaveValueIfNecessary(currentScope, codeStream);
 128         }
 129
 130         // generation of code responsible for invoking the finally blocks in sequence
 131         if (subroutines != null) {
 132                 for (int i = 0, max = subroutines.length; i < max; i++) {
 133                         AstNode sub;
 134                         if ((sub = subroutines[i]) instanceof SynchronizedStatement) {
 135                                 codeStream.load(((SynchronizedStatement) sub).synchroVariable);
 136                                 codeStream.monitorexit();
 137                         } else {
 138                                 TryStatement trySub = (TryStatement) sub;
 139                                 if (trySub.subRoutineCannotReturn) {
 140                                         codeStream.goto_(trySub.subRoutineStartLabel);
 141                                         codeStream.recordPositionsFrom(pc, this.sourceStart);
 142                                         return;
 143                                 } else {
 144                                         codeStream.jsr(trySub.subRoutineStartLabel);
 145                                 }
 146                         }
 147                 }
 148         }
 149         if (saveValueVariable != null) codeStream.load(saveValueVariable);
 150
 151         if ((expression != null) && (expression.constant != NotAConstant)) {
 152                 codeStream.generateConstant(expression.constant, expression.implicitConversion);
 153                 generateStoreSaveValueIfNecessary(currentScope, codeStream);
 154         }
 155         // output the suitable return bytecode or wrap the value inside a descriptor for doits
 156         this.generateReturnBytecode(currentScope, codeStream);
 157
 158         codeStream.recordPositionsFrom(pc, this.sourceStart);
 159 }
 160 /**
 161  * Dump the suitable return bytecode for a return statement
 162  *
 163  */
 164 public void generateReturnBytecode(BlockScope currentScope, CodeStream codeStream) {
 165
 166         if (expression == null) {
 167                 codeStream.return_();
 168         } else {
 169                 switch (expression.implicitConversion >> 4) {
 170                         case T_boolean :
 171                         case T_int :
 172                                 codeStream.ireturn();
 173                                 break;
 174                         case T_float :
 175                                 codeStream.freturn();
 176                                 break;
 177                         case T_long :
 178                                 codeStream.lreturn();
 179                                 break;
 180                         case T_double :
 181                                 codeStream.dreturn();
 182                                 break;
 183                         default :
 184                                 codeStream.areturn();
 185                 }
 186         }
 187 }
 188 public void generateStoreSaveValueIfNecessary(BlockScope currentScope, CodeStream codeStream){
 189
 190         if (saveValueVariable != null) codeStream.store(saveValueVariable, false);
 191 }
 192 public boolean needValue(){
 193         return (subroutines == null) || (saveValueVariable != null) || isSynchronized;
 194 }
 195 public void prepareSaveValueLocation(TryStatement targetTryStatement){
 196
 197         this.saveValueVariable = targetTryStatement.secretReturnValue;
 198 }
 199 public void resolve(BlockScope scope) {
 200         MethodScope methodScope = scope.methodScope();
 201         MethodBinding methodBinding;
 202         TypeBinding methodType =
 203                 (methodScope.referenceContext instanceof AbstractMethodDeclaration)
 204                         ? ((methodBinding = ((AbstractMethodDeclaration) methodScope.referenceContext).binding) == null
 205                                 ? null
 206                                 : methodBinding.returnType)
 207                         : VoidBinding;
 208         if (methodType == VoidBinding) {
 209                 // the expression should be null
 210                 if (expression == null)
 211                         return;
 212                 if ((expressionType = expression.resolveType(scope)) != null)
 213                         scope.problemReporter().attemptToReturnNonVoidExpression(this, expressionType);
 214                 return;
 215         }
 216         if (expression == null) {
 217                 if (methodType != null) scope.problemReporter().shouldReturn(methodType, this);
 218                 return;
 219         }
 220         if ((expressionType = expression.resolveType(scope)) == null)
 221                 return;
 222
 223         if (methodType != null && expression.isConstantValueOfTypeAssignableToType(expressionType, methodType)) {
 224                 // dealing with constant
 225                 expression.implicitWidening(methodType, expressionType);
 226                 return;
 227         }
 228         if (expressionType == VoidBinding) {
 229                 scope.problemReporter().attemptToReturnVoidValue(this);
 230                 return;
 231         }
 232         if (methodType != null && BlockScope.areTypesCompatible(expressionType, methodType)) {
 233                 expression.implicitWidening(methodType, expressionType);
 234                 return;
 235         }
 236         if (methodType != null){
 237                 scope.problemReporter().typeMismatchErrorActualTypeExpectedType(expression, expressionType, methodType);
 238         }
 239 }
 240 public String toString(int tab){
 241
 242         String s = tabString(tab) ;
 243         s = s + "return "; //$NON-NLS-1$
 244         if (expression != null )
 245                 s = s + expression.toStringExpression() ;
 246         return s;
 247 }
 248 public void traverse(IAbstractSyntaxTreeVisitor visitor, BlockScope scope) {
 249         if (visitor.visit(this, scope)) {
 250                 if (expression != null)
 251                         expression.traverse(visitor, scope);
 252         }
 253         visitor.endVisit(this, scope);
 254 }
 255 }