foo1.cs

      if (previousMember is IExpressionBodyOwnerDeclaration expressionBodyOwnerDeclaration)
      {
        return expressionBodyOwnerDeclaration.ArrowClause?.Expression != null
               && expressionBodyOwnerDeclaration.Semicolon == null;
      }

      return false;

foo2.cs

      if (previousMember is IExpressionBodyOwnerDeclaration { ArrowClause: { Expression: { } }, Semicolon: null })
      {
        return true;
      }

      return false;