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Type inference issue in subclasses #15191
Description
Activity
The problem is that
foo"overrides" (not really but in OO speak) the base property and is allowed to declare a less specific type.Improved workaround:
class A<T> { foo: T; } class B extends A<'bar'> { readonly foo = 'bar'; }
Note there have been dozens of issues about inheriting exact signatures, and Nathan Shively-Sanders (@sandersn) worked very hard on multiple potential implementations. See #6118 and #10570 where this is discussed in detail.
Personally, the compile time checked immutability in the above workaround is a nice side-effect at least.
Reacted by Nathan Shively-Sanders and Tommy Troy Lin- locked and limited conversation to collaborators
on Jun 21, 2018
TypeScript Version: 2.2.2
Code
workaround:
Expected behavior:
No Error;
Actual behavior:
Type string is not assignable to type 'bar';
I don't know if this behavior is intended.
I think type inference should be more accurate in this case to make programmers not to write
as sometypeonce again.