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

   1 /*******************************************************************************
   2  * Copyright (c) 2000, 2003 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  *     Genady Beriozkin - added support for reporting assignment with no effect
  11  *******************************************************************************/
  12 package net.sourceforge.phpdt.internal.compiler.ast;
  13
  14 import net.sourceforge.phpdt.internal.compiler.ASTVisitor;
  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.lookup.BaseTypeBinding;
  18 import net.sourceforge.phpdt.internal.compiler.lookup.Binding;
  19 import net.sourceforge.phpdt.internal.compiler.lookup.BlockScope;
  20 import net.sourceforge.phpdt.internal.compiler.lookup.TypeBinding;
  21
  22 public class Assignment extends Expression {
  23
  24         public Expression lhs;
  25         public Expression expression;
  26
  27         public Assignment(Expression lhs, Expression expression, int sourceEnd) {
  28                 //lhs is always a reference by construction ,
  29                 //but is build as an expression ==> the checkcast cannot fail
  30
  31                 this.lhs = lhs;
  32                 lhs.bits |= IsStrictlyAssignedMASK; // tag lhs as assigned
  33
  34                 this.expression = expression;
  35
  36                 this.sourceStart = lhs.sourceStart;
  37                 this.sourceEnd = sourceEnd;
  38         }
  39
  40         public FlowInfo analyseCode(
  41                 BlockScope currentScope,
  42                 FlowContext flowContext,
  43                 FlowInfo flowInfo) {
  44                 // record setting a variable: various scenarii are possible, setting an array reference,
  45                 // a field reference, a blank final field reference, a field of an enclosing instance or
  46                 // just a local variable.
  47
  48                 return ((Reference) lhs)
  49                         .analyseAssignment(currentScope, flowContext, flowInfo, this, false)
  50                         .unconditionalInits();
  51         }
  52
  53         void checkAssignmentEffect(BlockScope scope) {
  54
  55                 Binding left = getDirectBinding(this.lhs);
  56                 if (left != null && left == getDirectBinding(this.expression)) {
  57                         scope.problemReporter().assignmentHasNoEffect(this, left.shortReadableName());
  58                         this.bits |= IsAssignmentWithNoEffectMASK; // record assignment has no effect
  59                 }
  60         }
  61
  62 //      public void generateCode(
  63 //              BlockScope currentScope,
  64 //              CodeStream codeStream,
  65 //              boolean valueRequired) {
  66 //
  67 //              // various scenarii are possible, setting an array reference,
  68 //              // a field reference, a blank final field reference, a field of an enclosing instance or
  69 //              // just a local variable.
  70 //
  71 //              int pc = codeStream.position;
  72 //              if ((this.bits & IsAssignmentWithNoEffectMASK) != 0) {
  73 //                      if (valueRequired) {
  74 //                              this.expression.generateCode(currentScope, codeStream, true);
  75 //                      }
  76 //              } else {
  77 //                       ((Reference) lhs).generateAssignment(currentScope, codeStream, this, valueRequired);
  78 //                      // variable may have been optimized out
  79 //                      // the lhs is responsible to perform the implicitConversion generation for the assignment since optimized for unused local assignment.
  80 //              }
  81 //              codeStream.recordPositionsFrom(pc, this.sourceStart);
  82 //      }
  83
  84         Binding getDirectBinding(Expression someExpression) {
  85                 if (someExpression instanceof SingleNameReference) {
  86                         return ((SingleNameReference)someExpression).binding;
  87                 } else if (someExpression instanceof FieldReference) {
  88                         FieldReference fieldRef = (FieldReference)someExpression;
  89                         if (fieldRef.receiver.isThis() && !(fieldRef.receiver instanceof QualifiedThisReference)) {
  90                                 return fieldRef.binding;
  91                         }
  92                 }
  93                 return null;
  94         }
  95         public StringBuffer print(int indent, StringBuffer output) {
  96
  97                 //no () when used as a statement
  98                 printIndent(indent, output);
  99                 return printExpressionNoParenthesis(indent, output);
 100         }
 101         public StringBuffer printExpression(int indent, StringBuffer output) {
 102
 103                 //subclass redefine printExpressionNoParenthesis()
 104                 output.append('(');
 105                 return printExpressionNoParenthesis(0, output).append(')');
 106         }
 107
 108         public StringBuffer printExpressionNoParenthesis(int indent, StringBuffer output) {
 109
 110                 lhs.printExpression(indent, output).append(" = "); //$NON-NLS-1$
 111                 return expression.printExpression(0, output);
 112         }
 113
 114         public StringBuffer printStatement(int indent, StringBuffer output) {
 115
 116                 //no () when used as a statement
 117                 return print(indent, output).append(';');
 118         }
 119         public TypeBinding resolveType(BlockScope scope) {
 120
 121                 // due to syntax lhs may be only a NameReference, a FieldReference or an ArrayReference
 122                 constant = NotAConstant;
 123                 if (!(this.lhs instanceof Reference)) {
 124                         scope.problemReporter().expressionShouldBeAVariable(this.lhs);
 125                 }
 126                 this.resolvedType = lhs.resolveType(scope); // expressionType contains the assignment type (lhs Type)
 127                 TypeBinding rhsType = expression.resolveType(scope);
 128                 if (this.resolvedType == null || rhsType == null) {
 129                         return null;
 130                 }
 131                 checkAssignmentEffect(scope);
 132
 133                 // Compile-time conversion of base-types : implicit narrowing integer into byte/short/character
 134                 // may require to widen the rhs expression at runtime
 135                 if ((expression.isConstantValueOfTypeAssignableToType(rhsType, this.resolvedType)
 136                                 || (this.resolvedType.isBaseType() && BaseTypeBinding.isWidening(this.resolvedType.id, rhsType.id)))
 137                                 || rhsType.isCompatibleWith(this.resolvedType)) {
 138                         expression.implicitWidening(this.resolvedType, rhsType);
 139                         return this.resolvedType;
 140                 }
 141                 scope.problemReporter().typeMismatchErrorActualTypeExpectedType(
 142                         expression,
 143                         rhsType,
 144                         this.resolvedType);
 145                 return this.resolvedType;
 146         }
 147
 148         public String toString(int tab) {
 149
 150                 //no () when used as a statement
 151                 return tabString(tab) + toStringExpressionNoParenthesis();
 152         }
 153
 154         public String toStringExpression() {
 155
 156                 //subclass redefine toStringExpressionNoParenthesis()
 157                 return "(" + toStringExpressionNoParenthesis() + ")"; //$NON-NLS-2$ //$NON-NLS-1$
 158         }
 159
 160         public String toStringExpressionNoParenthesis() {
 161
 162                 return lhs.toStringExpression() + " " //$NON-NLS-1$
 163                         + "=" //$NON-NLS-1$
 164                         + ((expression.constant != null) && (expression.constant != NotAConstant)
 165                                 ? " /*cst:" + expression.constant.toString() + "*/ " //$NON-NLS-1$ //$NON-NLS-2$
 166                                 : " ")  //$NON-NLS-1$
 167                         + expression.toStringExpression();
 168         }
 169         public void traverse(ASTVisitor visitor, BlockScope scope) {
 170
 171                 if (visitor.visit(this, scope)) {
 172                         lhs.traverse(visitor, scope);
 173                         expression.traverse(visitor, scope);
 174                 }
 175                 visitor.endVisit(this, scope);
 176         }
 177 }