Program: 69194
Project: 69194
Buggy source:
/** 
 * @param params
 */
private void createParameterUISection(IParameterDefn[] params){
  txtParams=new Text[params.length];
  for (int i=0; i < params.length; i++) {
    IParameterDefn param=params[i];
    Label paramLabel=new Label(parameterContainer,SWT.NONE | SWT.WRAP);
    paramLabel.setText(Utility.getNonNullString(param.getDisplayName()));
    GridData gd=new GridData();
    final int widthHint=firstLabel.computeSize(-1,-1).x - firstLabel.getBorderWidth();
    gd.widthHint=widthHint;
    paramLabel.setLayoutData(gd);
    Composite composite=ControlProvider.getDefaultComposite(parameterContainer);
    if (param.isDataField()) {
      String text=BLANK;
      if (lastExpression != null) {
        text=lastExpression;
      }
 else {
        text=(String)getProperty(getStructureOrHandle(),cellProperties[EXPRESSION_INDEX]);
      }
      txtParams[i]=ControlProvider.createText(composite,text);
      final Text txtDataField=txtParams[i];
      txtDataField.setLayoutData(ControlProvider.getGridDataWithHSpan(1));
      txtDataField.addModifyListener(new ModifyListener(){
        public void modifyText(        ModifyEvent e){
          lastExpression=txtDataField.getText();
          validateSyntax();
        }
      }
);
    }
 else {
      Text txtArgument=ControlProvider.createText(composite,null);
      txtArgument.setLayoutData(ControlProvider.getGridDataWithHSpan(1));
      txtArgument.addModifyListener(new ModifyListener(){
        public void modifyText(        ModifyEvent e){
          validateSyntax();
        }
      }
);
      txtParams[i]=txtArgument;
    }
    txtParams[i].setToolTipText(param.getDescription());
    createExpressionButton(composite,txtParams[i]);
  }
  updateParametersText(params);
}

Fixed version (ground truth):
/** 
 * @param params
 */
private void createParameterUISection(IParameterDefn[] params){
  txtParams=new Text[params.length];
  for (int i=0; i < params.length; i++) {
    IParameterDefn param=params[i];
    Label paramLabel=new Label(parameterContainer,SWT.NONE | SWT.WRAP);
    paramLabel.setText(Utility.getNonNullString(param.getDisplayName()));
    GridData gd=new GridData();
    this.maxWidth=computeMaxWidth(paramLabel);
    gd.widthHint=this.maxWidth;
    paramLabel.setLayoutData(gd);
    Composite composite=ControlProvider.getDefaultComposite(parameterContainer);
    if (param.isDataField()) {
      String text=BLANK;
      if (lastExpression != null) {
        text=lastExpression;
      }
 else {
        text=(String)getProperty(getStructureOrHandle(),cellProperties[EXPRESSION_INDEX]);
      }
      txtParams[i]=ControlProvider.createText(composite,text);
      final Text txtDataField=txtParams[i];
      txtDataField.setLayoutData(ControlProvider.getGridDataWithHSpan(1));
      txtDataField.addModifyListener(new ModifyListener(){
        public void modifyText(        ModifyEvent e){
          lastExpression=txtDataField.getText();
          validateSyntax();
        }
      }
);
    }
 else {
      Text txtArgument=ControlProvider.createText(composite,null);
      txtArgument.setLayoutData(ControlProvider.getGridDataWithHSpan(1));
      txtArgument.addModifyListener(new ModifyListener(){
        public void modifyText(        ModifyEvent e){
          validateSyntax();
        }
      }
);
      txtParams[i]=txtArgument;
    }
    txtParams[i].setToolTipText(param.getDescription());
    createExpressionButton(composite,txtParams[i]);
  }
  updateLabelWidth();
  updateParametersText(params);
}