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Use type references for better error messages when relating to a union type #24776

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DanielRosenwasser opened this issue Jun 7, 2018 · 0 comments
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Use type references for better error messages when relating to a union type #24776

DanielRosenwasser opened this issue Jun 7, 2018 · 0 comments
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@DanielRosenwasser
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Bug A bug in TypeScript Domain: Error Messages The issue relates to error messaging Fixed A PR has been merged for this issue
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TypeScript 3.0

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@DanielRosenwasser
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When relating A<Foo> to A<Bar> | B<Baz> | C<Kwah>, if the check fails, it is highly likely that the user wants to see the elaboration from A<Foo> to A<Bar>, rather than for A<Foo> to B<Baz> or A<Foo> to C<Kwah>.

We should try to find candidates when source types are type references, and target types are unions.

As a real-world example, here's an error message where TypeScript had the chance to relate ComponentClass<...> to ComponentClass<...> | StatelessComponent<...>:

https://news.ycombinator.com/item?id=17244638

image

This should also work for if two types have a well-known type alias.

Vaguely related to #6541?
@DanielRosenwasser DanielRosenwasser changed the title Use type references for better error messages when relating a type to a union type Use type references for better error messages when relating to a union type Jun 7, 2018
@DanielRosenwasser DanielRosenwasser added Bug A bug in TypeScript Domain: Error Messages The issue relates to error messaging labels Jun 7, 2018
@DanielRosenwasser DanielRosenwasser added this to the TypeScript 3.0 milestone Jun 8, 2018
@DanielRosenwasser DanielRosenwasser mentioned this issue Jun 21, 2018
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@mhegazy mhegazy added the Fixed A PR has been merged for this issue label Jun 21, 2018
@DanielRosenwasser DanielRosenwasser mentioned this issue Jun 28, 2018
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@DanielRosenwasser DanielRosenwasser mentioned this issue Jul 10, 2018
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@DanielRosenwasser DanielRosenwasser mentioned this issue Jul 18, 2018
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