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Distribute 'keyof' intersection types#22300

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ahejlsberg merged 4 commits intomasterfromdistributeKeyofIntersection

Mar 3, 2018

Merged

Distribute 'keyof' intersection types#22300

ahejlsberg merged 4 commits intomasterfromdistributeKeyofIntersection

Mar 3, 2018

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ahejlsberg commentedMar 2, 2018•
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With this PR we transformkeyof applied to an intersection type to a union ofkeyof applied to each intersection constituent. In other words, we rewrite types of the formkeyof (A & B) tokeyof A | keyof B.

Some examples:

typeA={a:string};typeB={b:string};typeT1=keyof(A&B);// "a" | "b"typeT2<T>=keyof(T&B);// keyof T | "b"typeT3<U>=keyof(A&U);// "a" | keyof UtypeT4<T,U>=keyof(T&U);// keyof T | keyof UtypeT5=T2<A>;// "a" | "b"typeT6=T3<B>;// "a" | "b"typeT7=T4<A,B>;// "a" | "b"

Fixes#22291.

ahejlsberg added4 commits

March 2, 2018 09:11

Transform 'keyof (A & B)' to 'keyof A | keyof B'

fe075f2

Accept new baselines

4256be1

Add tests

95bb156

Accept new baselines

8861913

ahejlsberg requested review frommhegazy andweswigham

March 2, 2018 17:39

DanielRosenwasser mentioned this pull request

Mar 2, 2018

Design Meeting Notes, 3/2/2018#22304

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mhegazy mentioned this pull request

Mar 2, 2018

Can't use keyof index for indexing intersection of Partial<T> and another type in generic class<T>.#22286

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Mar 2, 2018

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weswigham commentedMar 2, 2018

keyof (string & {__brand: any}) and similar intersections needs tests documenting their behavior. (Other "empty" intersections likestring & number, too)

ahejlsberg merged commit2d5be24 intomaster

Mar 3, 2018

ahejlsberg deleted the distributeKeyofIntersection branch

March 3, 2018 00:08

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Griffork commentedMar 5, 2018•
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From#22286
Just downloaded the nightly, this doesn't work:

typeOptionalCommands<Cextendsstring,T>={[parameterinC]?:T};typeOptionalPropertyOrCommand<Cextendsstring,T>=Partial<T>&OptionalCommands<C,T>;

classThing<T>{thing:OptionalPropertyOrCommand<"this"|"that",T>;myfoo<VextendskeyofT>(property:V,newvalue:T[V]){this.thing[property]=newvalue;}myfoo2(newthing:T){this.thing["that"]=newthing;}}