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Maintain modifiers on Omit #31205

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merged 4 commits into from May 10, 2019
Merged

Maintain modifiers on Omit #31205

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60962a8
Added test.
DanielRosenwasser May 1, 2019
d22cb0c
Accepted baselines.
DanielRosenwasser May 1, 2019
d9e8246
Change `Omit` back to using `Pick<T, Exclude<keyof T, K>>` in order t…
DanielRosenwasser May 1, 2019
d7434a0
Accepted baselines.
DanielRosenwasser May 1, 2019
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4 changes: 1 addition & 3 deletions src/lib/es5.d.ts
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Expand Up @@ -1446,9 +1446,7 @@ type Extract<T, U> = T extends U ? T : never;
/**
* Construct a type with the properties of T except for those in type K.
*/
type Omit<T, K extends keyof any> = {
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@jwbay jwbay May 1, 2019 •
edited

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🤔Why can't this be K extends keyof T to make the type homomorphic?

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I don't believe that would make the type homomorphic, would it @ahejlsberg?

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Yeah, discussed offline, but for reasons outlined below, the fact that it's not just a simple keyof T or K (where K extends keyof T) means that TypeScript can't trivially look at that and say "yup, we gotta keep the modifiers around on this one".

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Could also do

type Omit<T, K extends keyof any> = T extends unknown ? Pick<T, Exclude<keyof T, K>> : never;

that is to say: making the builtin Omit distributive. (Which'd give it an alias symbol, too) A bunch of library authors end up swapping their internal Omit to this once they get into situations involving unions.

Distributive conditional like this have perf issues when nested repeatedly right now, tho, sooooo.... ehhhhh?

[P in Exclude<keyof T, K>]: T[P]
};
type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;

/**
* Exclude null and undefined from T
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12 changes: 6 additions & 6 deletions tests/baselines/reference/genericIsNeverEmptyObject.types
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Expand Up @@ -2,18 +2,18 @@
// Repro from #29067

function test<T extends { a: string }>(obj: T) {
>test : <T extends { a: string; }>(obj: T) => Omit<T, "a"> & { b: string; }
>test : <T extends { a: string; }>(obj: T) => Pick<T, Exclude<keyof T, "a">> & { b: string; }
>a : string
>obj : T

let { a, ...rest } = obj;
>a : string
>rest : Omit<T, "a">
>rest : Pick<T, Exclude<keyof T, "a">>
>obj : T

return { ...rest, b: a };
>{ ...rest, b: a } : Omit<T, "a"> & { b: string; }
>rest : Omit<T, "a">
>{ ...rest, b: a } : Pick<T, Exclude<keyof T, "a">> & { b: string; }
>rest : Pick<T, Exclude<keyof T, "a">>
>b : string
>a : string
}
Expand All @@ -30,7 +30,7 @@ let o2: { b: string, x: number } = test(o1);
>o2 : { b: string; x: number; }
>b : string
>x : number
>test(o1) : Omit<{ a: string; x: number; }, "a"> & { b: string; }
>test : <T extends { a: string; }>(obj: T) => Omit<T, "a"> & { b: string; }
>test(o1) : Pick<{ a: string; x: number; }, "x"> & { b: string; }
>test : <T extends { a: string; }>(obj: T) => Pick<T, Exclude<keyof T, "a">> & { b: string; }
>o1 : { a: string; x: number; }

16 changes: 8 additions & 8 deletions tests/baselines/reference/genericObjectRest.types
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Expand Up @@ -16,32 +16,32 @@ function f1<T extends { a: string, b: number }>(obj: T) {
let { a: a1, ...r1 } = obj;
>a : any
>a1 : string
>r1 : Omit<T, "a">
>r1 : Pick<T, Exclude<keyof T, "a">>
>obj : T

let { a: a2, b: b2, ...r2 } = obj;
>a : any
>a2 : string
>b : any
>b2 : number
>r2 : Omit<T, "a" | "b">
>r2 : Pick<T, Exclude<keyof T, "a" | "b">>
>obj : T

let { 'a': a3, ...r3 } = obj;
>a3 : string
>r3 : Omit<T, "a">
>r3 : Pick<T, Exclude<keyof T, "a">>
>obj : T

let { ['a']: a4, ...r4 } = obj;
>'a' : "a"
>a4 : string
>r4 : Omit<T, "a">
>r4 : Pick<T, Exclude<keyof T, "a">>
>obj : T

let { [a]: a5, ...r5 } = obj;
>a : "a"
>a5 : string
>r5 : Omit<T, "a">
>r5 : Pick<T, Exclude<keyof T, "a">>
>obj : T
}

Expand All @@ -68,7 +68,7 @@ function f2<T extends { [sa]: string, [sb]: number }>(obj: T) {
>a1 : string
>sb : unique symbol
>b1 : number
>r1 : Omit<T, unique symbol | unique symbol>
>r1 : Pick<T, Exclude<keyof T, unique symbol | unique symbol>>
>obj : T
}

Expand All @@ -83,7 +83,7 @@ function f3<T, K1 extends keyof T, K2 extends keyof T>(obj: T, k1: K1, k2: K2) {
>a1 : T[K1]
>k2 : K2
>a2 : T[K2]
>r1 : Omit<T, K1 | K2>
>r1 : Pick<T, Exclude<keyof T, K1 | K2>>
>obj : T
}

Expand All @@ -104,7 +104,7 @@ function f4<K1 extends keyof Item, K2 extends keyof Item>(obj: Item, k1: K1, k2:
>a1 : Item[K1]
>k2 : K2
>a2 : Item[K2]
>r1 : Omit<Item, K1 | K2>
>r1 : Pick<Item, Exclude<"a", K1 | K2> | Exclude<"b", K1 | K2> | Exclude<"c", K1 | K2>>
>obj : Item
}

6 changes: 3 additions & 3 deletions tests/baselines/reference/literalTypeWidening.types
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Expand Up @@ -443,14 +443,14 @@ function test<T extends { a: string, b: string }>(obj: T): T {

let { a, ...rest } = obj;
>a : string
>rest : Omit<T, "a">
>rest : Pick<T, Exclude<keyof T, "a">>
>obj : T

return { a: 'hello', ...rest } as T;
>{ a: 'hello', ...rest } as T : T
>{ a: 'hello', ...rest } : { a: string; } & Omit<T, "a">
>{ a: 'hello', ...rest } : { a: string; } & Pick<T, Exclude<keyof T, "a">>
>a : string
>'hello' : "hello"
>rest : Omit<T, "a">
>rest : Pick<T, Exclude<keyof T, "a">>
}

4 changes: 2 additions & 2 deletions tests/baselines/reference/mappedTypeConstraints.symbols
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Expand Up @@ -132,9 +132,9 @@ const modifier = <T extends TargetProps>(targetProps: T) => {
>targetProps : Symbol(targetProps, Decl(mappedTypeConstraints.ts, 30, 41))

rest.foo;
>rest.foo : Symbol(foo)
>rest.foo : Symbol(foo, Decl(mappedTypeConstraints.ts, 25, 20))
>rest : Symbol(rest, Decl(mappedTypeConstraints.ts, 31, 13))
>foo : Symbol(foo)
>foo : Symbol(foo, Decl(mappedTypeConstraints.ts, 25, 20))

};

4 changes: 2 additions & 2 deletions tests/baselines/reference/mappedTypeConstraints.types
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Expand Up @@ -98,12 +98,12 @@ const modifier = <T extends TargetProps>(targetProps: T) => {

let {bar, ...rest} = targetProps;
>bar : string
>rest : Omit<T, "bar">
>rest : Pick<T, Exclude<keyof T, "bar">>
>targetProps : T

rest.foo;
>rest.foo : T["foo"]
>rest : Omit<T, "bar">
>rest : Pick<T, Exclude<keyof T, "bar">>
>foo : T["foo"]

};
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6 changes: 3 additions & 3 deletions tests/baselines/reference/objectRestNegative.types
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Expand Up @@ -36,18 +36,18 @@ function stillMustBeLast({ ...mustBeLast, a }: { a: number, b: string }): void {
>b : string
}
function generic<T extends { x, y }>(t: T) {
>generic : <T extends { x: any; y: any; }>(t: T) => Omit<T, "x">
>generic : <T extends { x: any; y: any; }>(t: T) => Pick<T, Exclude<keyof T, "x">>
>x : any
>y : any
>t : T

let { x, ...rest } = t;
>x : any
>rest : Omit<T, "x">
>rest : Pick<T, Exclude<keyof T, "x">>
>t : T

return rest;
>rest : Omit<T, "x">
>rest : Pick<T, Exclude<keyof T, "x">>
}

let rest: { b: string }
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27 changes: 27 additions & 0 deletions tests/baselines/reference/omitTypeHelperModifiers01.errors.txt
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@@ -0,0 +1,27 @@
tests/cases/compiler/omitTypeHelperModifiers01.ts(16,7): error TS2540: Cannot assign to 'c' because it is a read-only property.


==== tests/cases/compiler/omitTypeHelperModifiers01.ts (1 errors) ====
type A = {
a: number;
b?: string;
readonly c: boolean;
d: unknown;
};

type B = Omit<A, 'a'>;

function f(x: B) {
const b = x.b;
x.b = "hello";
x.b = undefined;

const c = x.c;
x.c = true;
~
!!! error TS2540: Cannot assign to 'c' because it is a read-only property.

const d = x.d;
x.d = d;
}

34 changes: 34 additions & 0 deletions tests/baselines/reference/omitTypeHelperModifiers01.js
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@@ -0,0 +1,34 @@
//// [omitTypeHelperModifiers01.ts]
type A = {
a: number;
b?: string;
readonly c: boolean;
d: unknown;
};

type B = Omit<A, 'a'>;

function f(x: B) {
const b = x.b;
x.b = "hello";
x.b = undefined;

const c = x.c;
x.c = true;

const d = x.d;
x.d = d;
}


//// [omitTypeHelperModifiers01.js]
"use strict";
function f(x) {
var b = x.b;
x.b = "hello";
x.b = undefined;
var c = x.c;
x.c = true;
var d = x.d;
x.d = d;
}
69 changes: 69 additions & 0 deletions tests/baselines/reference/omitTypeHelperModifiers01.symbols
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@@ -0,0 +1,69 @@
=== tests/cases/compiler/omitTypeHelperModifiers01.ts ===
type A = {
>A : Symbol(A, Decl(omitTypeHelperModifiers01.ts, 0, 0))

a: number;
>a : Symbol(a, Decl(omitTypeHelperModifiers01.ts, 0, 10))

b?: string;
>b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))

readonly c: boolean;
>c : Symbol(c, Decl(omitTypeHelperModifiers01.ts, 2, 15))

d: unknown;
>d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 3, 24))

};

type B = Omit<A, 'a'>;
>B : Symbol(B, Decl(omitTypeHelperModifiers01.ts, 5, 2))
>Omit : Symbol(Omit, Decl(lib.es5.d.ts, --, --))
>A : Symbol(A, Decl(omitTypeHelperModifiers01.ts, 0, 0))

function f(x: B) {
>f : Symbol(f, Decl(omitTypeHelperModifiers01.ts, 7, 22))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>B : Symbol(B, Decl(omitTypeHelperModifiers01.ts, 5, 2))

const b = x.b;
>b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 10, 9))
>x.b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))

x.b = "hello";
>x.b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))

x.b = undefined;
>x.b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>b : Symbol(b, Decl(omitTypeHelperModifiers01.ts, 1, 14))
>undefined : Symbol(undefined)

const c = x.c;
>c : Symbol(c, Decl(omitTypeHelperModifiers01.ts, 14, 9))
>x.c : Symbol(c, Decl(omitTypeHelperModifiers01.ts, 2, 15))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>c : Symbol(c, Decl(omitTypeHelperModifiers01.ts, 2, 15))

x.c = true;
>x.c : Symbol(c, Decl(omitTypeHelperModifiers01.ts, 2, 15))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>c : Symbol(c, Decl(omitTypeHelperModifiers01.ts, 2, 15))

const d = x.d;
>d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 17, 9))
>x.d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 3, 24))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 3, 24))

x.d = d;
>x.d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 3, 24))
>x : Symbol(x, Decl(omitTypeHelperModifiers01.ts, 9, 11))
>d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 3, 24))
>d : Symbol(d, Decl(omitTypeHelperModifiers01.ts, 17, 9))
}

72 changes: 72 additions & 0 deletions tests/baselines/reference/omitTypeHelperModifiers01.types
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@@ -0,0 +1,72 @@
=== tests/cases/compiler/omitTypeHelperModifiers01.ts ===
type A = {
>A : A

a: number;
>a : number

b?: string;
>b : string | undefined

readonly c: boolean;
>c : boolean

d: unknown;
>d : unknown

};

type B = Omit<A, 'a'>;
>B : Pick<A, "b" | "c" | "d">

function f(x: B) {
>f : (x: Pick<A, "b" | "c" | "d">) => void
>x : Pick<A, "b" | "c" | "d">

const b = x.b;
>b : string | undefined
>x.b : string | undefined
>x : Pick<A, "b" | "c" | "d">
>b : string | undefined

x.b = "hello";
>x.b = "hello" : "hello"
>x.b : string | undefined
>x : Pick<A, "b" | "c" | "d">
>b : string | undefined
>"hello" : "hello"

x.b = undefined;
>x.b = undefined : undefined
>x.b : string | undefined
>x : Pick<A, "b" | "c" | "d">
>b : string | undefined
>undefined : undefined

const c = x.c;
>c : boolean
>x.c : boolean
>x : Pick<A, "b" | "c" | "d">
>c : boolean

x.c = true;
>x.c = true : true
>x.c : any
>x : Pick<A, "b" | "c" | "d">
>c : any
>true : true

const d = x.d;
>d : unknown
>x.d : unknown
>x : Pick<A, "b" | "c" | "d">
>d : unknown

x.d = d;
>x.d = d : unknown
>x.d : unknown
>x : Pick<A, "b" | "c" | "d">
>d : unknown
>d : unknown
}