TypeScript - Cannot access static members of model with .schema() call

[kvcpr]

Issue Description

When you call .schema() method of model then call static member typescript says that member doesn't exist.

What are you doing?

class TestModelWithStaticMethod extends Model {
  static someStaticFn() {
    return 'hello!';
  }
};
TestModelWithStaticMethod.init({ hello: { type: DataTypes.BOOLEAN, allowNull: false } }, { sequelize });
const testModelWithStaticMethod = TestModelWithStaticMethod.schema('some_schema');
testModelWithStaticMethod.someStaticFn();

What do you expect to happen?

Ability to use static members of model without warnings.

What is actually happening?

> tsc -b types/tsconfig.json && tsc -b types/test/tsconfig.json

types/test/model.ts:86:27 - error TS2339: Property 'someStaticFn' does not exist on type '(new () => TestModelWithStaticMethod) & typeof Model'.

86 testModelWithStaticMethod.someStaticFn();

Environment

• Sequelize version: 5.x and 6.x
• Node.js version: v13.2.0
• Operating System: macOS 10.15.3
• If TypeScript related: TypeScript version: 3.7.2

Issue Template Checklist

How does this problem relate to dialects?

• I think this problem happens regardless of the dialect.
• I think this problem happens only for the following dialect(s):
• I don't know, I was using PUT-YOUR-DIALECT-HERE, with connector library version XXX and database version XXX

Would you be 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.

[github-actions]

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