Program: 161431
Project: 161431
Buggy source:
@Nullable @Override public TextRange adjustSurroundWithRange(PsiFile file,TextRange selectedRange,boolean hasSelection){
  int startOffset=selectedRange.getStartOffset();
  int endOffset=selectedRange.getEndOffset();
  if (endOffset < startOffset) {
    int tmp=endOffset;
    endOffset=startOffset;
    startOffset=tmp;
  }
  if (hasSelection) {
    final FileViewProvider viewProvider=file.getViewProvider();
    PsiElement element1=viewProvider.findElementAt(startOffset,MathematicaLanguage.INSTANCE);
    PsiElement element2=viewProvider.findElementAt(endOffset - 1,MathematicaLanguage.INSTANCE);
    if (element1 instanceof PsiWhiteSpace) {
      startOffset=element1.getTextRange().getEndOffset();
      element1=file.findElementAt(startOffset);
    }
    if (element2 instanceof PsiWhiteSpace) {
      endOffset=element2.getTextRange().getStartOffset();
      element2=file.findElementAt(endOffset - 1);
    }
    if (element1 != null && element2 != null) {
      final int startOffset1=element1.getTextRange().getStartOffset();
      final int endOffset1=element2.getTextRange().getEndOffset();
      if (startOffset1 < endOffset1) {
        return TextRange.create(startOffset1,endOffset1);
      }
    }
    return null;
  }
 else {
    final Project project=file.getProject();
    final Editor selectedTextEditor=FileEditorManager.getInstance(project).getSelectedTextEditor();
    if (selectedTextEditor == null) {
      return null;
    }
    PsiElement element=PsiUtilBase.getElementAtCaret(selectedTextEditor);
    if (element == null) {
      return null;
    }
    SurroundExpressionFinder expressionFinder=new SurroundExpressionFinder();
    element.accept(expressionFinder);
    PsiElement bestExpression=expressionFinder.getBestExpression();
    if (bestExpression instanceof Expression) {
      final TextRange textRange=bestExpression.getTextRange();
      selectedTextEditor.getSelectionModel().setSelection(textRange.getStartOffset(),textRange.getEndOffset());
      return bestExpression.getTextRange();
    }
  }
  return null;
}

Fixed version (ground truth):
@Nullable @Override public TextRange adjustSurroundWithRange(PsiFile file,TextRange selectedRange,boolean hasSelection){
  if (!(file instanceof MathematicaPsiFile)) {
    return selectedRange;
  }
  int startOffset=selectedRange.getStartOffset();
  int endOffset=selectedRange.getEndOffset();
  if (endOffset < startOffset) {
    int tmp=endOffset;
    endOffset=startOffset;
    startOffset=tmp;
  }
  if (hasSelection) {
    final FileViewProvider viewProvider=file.getViewProvider();
    PsiElement element1=viewProvider.findElementAt(startOffset,MathematicaLanguage.INSTANCE);
    PsiElement element2=viewProvider.findElementAt(endOffset - 1,MathematicaLanguage.INSTANCE);
    if (element1 instanceof PsiWhiteSpace) {
      startOffset=element1.getTextRange().getEndOffset();
      element1=file.findElementAt(startOffset);
    }
    if (element2 instanceof PsiWhiteSpace) {
      endOffset=element2.getTextRange().getStartOffset();
      element2=file.findElementAt(endOffset - 1);
    }
    if (element1 != null && element2 != null) {
      final int startOffset1=element1.getTextRange().getStartOffset();
      final int endOffset1=element2.getTextRange().getEndOffset();
      if (startOffset1 < endOffset1) {
        return TextRange.create(startOffset1,endOffset1);
      }
    }
    return null;
  }
 else {
    final Project project=file.getProject();
    final Editor selectedTextEditor=FileEditorManager.getInstance(project).getSelectedTextEditor();
    if (selectedTextEditor == null) {
      return null;
    }
    PsiElement element=PsiUtilBase.getElementAtCaret(selectedTextEditor);
    if (element == null) {
      return null;
    }
    SurroundExpressionFinder expressionFinder=new SurroundExpressionFinder();
    element.accept(expressionFinder);
    PsiElement bestExpression=expressionFinder.getBestExpression();
    if (bestExpression instanceof Expression) {
      final TextRange textRange=bestExpression.getTextRange();
      selectedTextEditor.getSelectionModel().setSelection(textRange.getStartOffset(),textRange.getEndOffset());
      return bestExpression.getTextRange();
    }
  }
  return selectedRange;
}