TS2.4 compile error with derived type assignment

[Diluka]

TypeScript Version: 2.4.1

Code

// A *self-contained* demonstration of the problem follows...
export class City extends BaseModel {
  //...
}

export abstract class BaseModel extends Model {
  //...
}

export abstract class Model {
  //...
}

Expected behavior:
compile without error
Actual behavior:

error TS2345: Argument of type 'typeof City' is not assignable to parameter of type 'typeof Model'.
  Type 'City' is not assignable to type 'Model'.
    Types of property 'set' are incompatible.
      Type '{ <K extends "reload" | "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "s...' is not assignable to type '{ <K extends "reload" | "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "s...'. Two different types with this name exist, but they are unrelated.
        Type 'City' is not assignable to type 'Model'.

[felixfbecker]

This is related to using workarounds for static polymorphic this as described in #5863

See https://travis-ci.org/types/sequelize/builds/247636686

[sylvanaar]

You left out the code that would tell us the answer

Type '{ <K extends "reload" | "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "s...' is not assignable to type '{ <K extends "reload" | "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "s...'. Two different types with this name exist, but they are unrelated.

[felixfbecker]

It's in the build that I linked. Seems to be an issue with module resolution - but it worked before 2.4
Maybe correct the issue title?

[RyanCavanaugh]

You'll need to provide a repro that actually demonstrates the problem. Three empty class declarations is not sufficient.

[felixfbecker]

@RyanCavanaugh You can reproduce by cloning https://github.com/types/sequelize and running the commands from the failed build (npm install, tsc -p .). It compiles under TS 2.3 but 2.4 produces the posted error. Please let me know if there is anything I am doing wrong on my side.

[txiaocao]

oh my god....i dont know what happend.my project can not run..because of something package update typescript version@2.4.0 by semantics version...

[kitsonk]

Almost all of these errors are actual errors in how people typed things. It may not be your code directly, but it maybe some sort of upstream system. Before 2.4, the type system was a bit lazy when it came to assessing the assignability of generics.

Likely somewhere City is being filled in a generic slot which before TypeScript didn't actually evaluate the assignability. The error Two different types with this name exist, but they are unrelated. can often be because you have duplicate versions of a package where that type comes from in two physically different locations where the TypeScript compiler is running, or actually those two types are coming from two separate definitions but are named the same. In some cases, especially with symbols and generic operators, TypeScript plays it "safe" by indicating it can't ensure that the types are the same, though they might look the same.

Either way there is a problem in the code that likely needs to be addressed, because there is some sort of unsound type handling going on. Of course you can 🙈 🙉 🙊 and turn on --noStrictGenericChecks in 2.4 which should restore the behaviour of not being so strict.

[felixfbecker]

@kitsonk can you explain the wrong typing in this error?

error TS2684: The 'this' context of type 'typeof User' is not assignable to method's 'this' of type '(new () => User) & typeof Model'.
  Type 'typeof User' is not assignable to type 'typeof Model'

if User extends Model, then typeof User should be assignable to typeof Model, and it was in TS 2.3

[lumaxis]

@RyanCavanaugh I'm trying to update the Sequelize types to 2.4 but that is blocked by this issue. Does the public repo work as a repro case for you?

[RyanCavanaugh]

@lumaxis we generally don't have time to investigate large external repositories to diagnose user code unless there's a crash or other clear evidence of a TS bug. If there's something blocking you from creating a self-contained minimal repro I can help you with some tips if needed.

[mitchell-garcia]

@RyanCavanaugh Hi Ryan - I created a self-contained repository with the mentioned packages above to demonstrate the issue. It is here: https://github.com/mmitchellgarcia/Derived-Type-Assignment-Error. If you run npm install then npm run build on that repo with Typescript 2.4.2, you'll get this issue:

src/MainModel.ts(20,19): error TS2345: Argument of type 'typeof AssociatedModel' is not assignable to parameter of type 'typeof Model'.
  Type 'AssociatedModel' is not assignable to type 'Model'.
    Types of property 'set' are incompatible.
      Type '{ <K extends "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "setDataValue...' is not assignable to type '{ <K extends "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "setDataValue...'. Two different types with this name exist, but they are unrelated.
        Type 'AssociatedModel' is not assignable to type 'Model'.
src/MainModel.ts(27,18): error TS2345: Argument of type 'typeof AdditionalModel' is not assignable to parameter of type 'typeof Model'.
  Type 'AdditionalModel' is not assignable to type 'Model'.
    Types of property 'set' are incompatible.
      Type '{ <K extends "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "setDataValue...' is not assignable to type '{ <K extends "isNewRecord" | "sequelize" | "aggregate" | "where" | "getDataValue" | "setDataValue...'. Two different types with this name exist, but they are unrelated.
        Type 'AdditionalModel' is not assignable to type 'Model'.