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Exclude<T, U> type not working like Diff<T, U> #21929
Description
TypeScript Version: 2.8.0-dev.20180213
Search Terms:
- Exclude
- Diff
Code
// Old 'Diff' type, superseded since #21847 by new 'Exclude' builtin type
type Diff<T extends string, U extends string>
= ({[P in T]: P } & {[P in U]: never } & { [x: string]: never })[T];
type NonFooKeys1<T extends object> = Diff<keyof T, 'foo'>; // remove 'foo' using Diff
type NonFooKeys2<T extends object> = Exclude<keyof T, 'foo'>; // remove 'foo' using Exclude
type Test1 = NonFooKeys1<{foo: 1, bar: 2, baz: 3}>; // Test1 is "bar" | "baz"
type Test2 = NonFooKeys2<{foo: 1, bar: 2, baz: 3}>; // Test2 is "foo" | "bar" | "baz"Expected behavior:
Test2 should be "bar" | "baz", the same as Test1.
Actual behavior:
The key "foo" was not removed from keyof T when using the Exclude builtin type.
Related Issues:
Activity
DanielRosenwasser commentedon Feb 14, 2018
Of note, I'm getting some strange quick info. When defined as
I get
jack-williams commentedon Feb 14, 2018
Is this related to #21664 ?
Excludeworks when used directly for me.falsandtru commentedon Feb 14, 2018
related #21862.
ahejlsberg commentedon Feb 14, 2018
Duplicate of #21862.
KiaraGrouwstra commentedon Feb 15, 2018
The other issue is marked fixed now.