"Order" not works when custom toString() is defined

[rysi3k]

Issue Description

When model has custom toString() implementation it is not possible to proper use order clause.
Additional typeorm thinks that is ok to sort by method name.

Expected Behavior

1. Sorting when toString() is defined should be possible
2. Not possible to sort by defined methods

Actual Behavior

TS2769: No overload matches this call.
  Overload 1 of 2, '(options?: FindManyOptions<Transaction>): Promise<Transaction[]>', gave the following error.
    Type '{ someMethod: "ASC"; }' is not assignable to type '{ id?: 1 | "ASC" | "DESC" | -1; name?: 1 | "ASC" | "DESC" | -1; toString?: 1 | "ASC" | "DESC" | -1; someMethod?: 1 | "ASC" | "DESC" | -1; }'.
      Types of property 'toString' are incompatible.
        Type '() => string' is not assignable to type '1 | "ASC" | "DESC" | -1'.
          Type '() => string' is not assignable to type '-1'.
  Overload 2 of 2, '(conditions?: FindConditions<Transaction>): Promise<Transaction[]>', gave the following error.
    Argument of type '{ order: { someMethod: string; }; where: { id: number; }; }' is not assignable to parameter of type 'FindConditions<Transaction>'.
      Object literal may only specify known properties, and 'order' does not exist in type 'FindConditions<Transaction>'.

Steps to Reproduce

import {Column, Entity, EntityRepository, PrimaryGeneratedColumn, Repository} from 'typeorm';

@Entity('Transactions')
class Transaction {
    @PrimaryGeneratedColumn()
    public id?: number;

    @Column()
    public name?: string;

    // when defined there is ERROR in find call, below
    public toString() {
        return `${this.name}`;
    }

    public someMethod() {
        return 123;
    }
}

@EntityRepository(Transaction)
class TransactionsRepository extends Repository<Transaction> {

}

const repo = new TransactionsRepository();
repo.find({
    order: {
        someMethod: 'ASC', // wrong usage, but for typeorm it is ok
    },
    where: {
        id: 1,
    },
});

My Environment

Dependency	Version
Operating System	macos
Node.js version	v12.18.0
Typescript version	v3.9.7
TypeORM version	v0.2.29

Relevant Database Driver(s)

• aurora-data-api
• aurora-data-api-pg
• better-sqlite3
• cockroachdb
• cordova
• expo
• mongodb
• mysql
• nativescript
• oracle
• postgres
• react-native
• sap
• sqlite
• sqlite-abstract
• sqljs
• sqlserver

Are you willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time, and I know how to start.
• Yes, I have the time, but I don't know how to start. I would need guidance.
• No, I don't have the time, although I believe I could do it if I had the time...
• No, I don't have the time and I wouldn't even know how to start.

[nebkat]

Interesting problem, I guess the solution is to exclude all function keys since you can't sort by functions anyway?