Feed the 'this' type as a type argument to constraints during relation checking #7290
Conversation
DanielRosenwasser
changed the title
| if (!constraint || constraint.flags & TypeFlags.Any) { | ||
| constraint = emptyObjectType; | ||
| } | ||
|
|
||
| // The constraint may need to be further instantiated with its 'this' type. | ||
| constraint = getTypeWithThisArgument(constraint); |
There was a problem hiding this comment.
Let me check my understanding: an unconstrained type parameter gets 'any' or '{}' as its constraint, which shouldn't have a this-type, so this is a no-op there. Am I right?
There was a problem hiding this comment.
Yup. I could have introduced an else branch, but I figured that this would be a little simpler to read. I'm open to changing it.
There was a problem hiding this comment.
No, I think it's fine. Just checking.
There was a problem hiding this comment.
You want to instantiate the constraint with source as the this-type parameter, so this line should be:
constraint = getTypeWithThisArgument(constraint, source);As you have it now you're instantiating the constraint with its own this-type as the this-type parameter. I think the reason it works with the example in the bug is because the this-type of Something is assignable to the this-type of Bar, but it's not the right solution.
|
👍 |
|
@DanielRosenwasser can you update the PR and respond to the remaining comments. |
Fixes #7276.
@ahejlsberg @sandersn @RyanCavanaugh can you take a look?
Right now, the types are being instantiated with their
target. Is this sufficient?