Include inferred usages in 'find references'

[OliverJAsh]

type Child = { name: string }
type Parent = { children: Child[] }
const createParent = (): Parent => (
  { children: ['foo', 'bar']
    .map((name) => ({ name }))
  }
)

TS is type-checking Parent, which involves type checking the children property and thus each `Child.

When I select name inside my Array mapper function and invoke TS to find references, VSCode/TypeScript server does not include the original type definition of Child.name:

(See Child.name is not highlighted).

However, if I add the type annotation for Child, it does include it in the list of references:

type Child = { name: string }
type Parent = { children: Child[] }
const createParent = (): Parent => (
  { children: ['foo', 'bar']
    .map((name): Child => ({ name }))
  }
)

Would it be possible to make TypeScript include the references that are inferred instead of annotated, e.g. example 1 as well as example 2?

The problem is that in (name) => ({ name }), the type of { name } isn't inferred to be Child. It's inferred to be { name: string }, a different type which happens to be assignable to Child. So it's not the case that ({ name }) is a Child, but it's assignable to one.

So find-all-references won't work because the name there is actually a different property, defined on a newly created type. When you explicitly specify : Child, that gives us a contextual type for the literal and we can find references correctly.

The real fix for this situation would be to provide contextual types even through generic calls, so that ({ name }) would be interpreted as a Child literal and not as its own type. See #15680.

#15680 is closed now but that didn't fix this. See #11152 and #3423 now.