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feat: add 'Nullable' type #39523

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5 changes: 5 additions & 0 deletions lib/lib.es5.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1508,6 +1508,11 @@ type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
*/
type NonNullable<T> = T extends null | undefined ? never : T;

/**
* Include null and undefined with T
*/
type Nullable<T> = T | null | undefined;

/**
* Obtain the parameters of a function type in a tuple
*/
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5 changes: 5 additions & 0 deletions src/lib/es5.d.ts
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Expand Up @@ -1488,6 +1488,11 @@ type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
*/
type NonNullable<T> = T extends null | undefined ? never : T;

/**
* Include null and undefined with T
*/
type Nullable<T> = T | null | undefined;

/**
* Obtain the parameters of a function type in a tuple
*/
Expand Down
74 changes: 60 additions & 14 deletions tests/baselines/reference/mappedTypes6.errors.txt
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Expand Up @@ -13,20 +13,30 @@ tests/cases/conformance/types/mapped/mappedTypes6.ts(42,5): error TS2322: Type '
tests/cases/conformance/types/mapped/mappedTypes6.ts(43,5): error TS2322: Type 'Partial<T>' is not assignable to type 'Required<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(47,5): error TS2322: Type 'Partial<T>' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'Partial<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(56,5): error TS2322: Type '{}' is not assignable to type 'Denullified<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(57,5): error TS2322: Type '{}' is not assignable to type 'Required<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(58,5): error TS2322: Type '{}' is not assignable to type 'T'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(55,5): error TS2322: Type '{}' is not assignable to type 'Denullified<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(56,5): error TS2322: Type '{}' is not assignable to type 'Required<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(57,5): error TS2322: Type '{}' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to '{}'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(92,1): error TS2741: Property 'b' is missing in type '{ a: number; }' but required in type 'Foo'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(104,1): error TS2739: Type '{ a: number; }' is missing the following properties from type 'Required<Foo>': b, c, d
tests/cases/conformance/types/mapped/mappedTypes6.ts(105,1): error TS2739: Type '{ a: number; b: number; }' is missing the following properties from type 'Required<Foo>': c, d
tests/cases/conformance/types/mapped/mappedTypes6.ts(106,1): error TS2741: Property 'd' is missing in type '{ a: number; b: number; c: number; }' but required in type 'Required<Foo>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(116,4): error TS2540: Cannot assign to 'b' because it is a read-only property.
tests/cases/conformance/types/mapped/mappedTypes6.ts(119,4): error TS2540: Cannot assign to 'a' because it is a read-only property.
tests/cases/conformance/types/mapped/mappedTypes6.ts(120,4): error TS2540: Cannot assign to 'b' because it is a read-only property.
tests/cases/conformance/types/mapped/mappedTypes6.ts(84,5): error TS2322: Type 'Nullified<T>' is not assignable to type 'Required<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(86,5): error TS2322: Type 'T' is not assignable to type 'Required<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(87,5): error TS2322: Type 'Partial<T>' is not assignable to type 'Required<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(88,5): error TS2322: Type 'Nullified<T>' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'Nullified<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(91,5): error TS2322: Type 'Partial<T>' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'Partial<T>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(92,5): error TS2322: Type 'Nullified<T>' is not assignable to type 'Partial<T>'.
Type 'Nullable<T[P]>' is not assignable to type 'T[P] | undefined'.
Type 'null' is not assignable to type 'T[P] | undefined'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(112,1): error TS2741: Property 'b' is missing in type '{ a: number; }' but required in type 'Foo'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(124,1): error TS2739: Type '{ a: number; }' is missing the following properties from type 'Required<Foo>': b, c, d
tests/cases/conformance/types/mapped/mappedTypes6.ts(125,1): error TS2739: Type '{ a: number; b: number; }' is missing the following properties from type 'Required<Foo>': c, d
tests/cases/conformance/types/mapped/mappedTypes6.ts(126,1): error TS2741: Property 'd' is missing in type '{ a: number; b: number; c: number; }' but required in type 'Required<Foo>'.
tests/cases/conformance/types/mapped/mappedTypes6.ts(136,4): error TS2540: Cannot assign to 'b' because it is a read-only property.
tests/cases/conformance/types/mapped/mappedTypes6.ts(139,4): error TS2540: Cannot assign to 'a' because it is a read-only property.
tests/cases/conformance/types/mapped/mappedTypes6.ts(140,4): error TS2540: Cannot assign to 'b' because it is a read-only property.


==== tests/cases/conformance/types/mapped/mappedTypes6.ts (19 errors) ====
==== tests/cases/conformance/types/mapped/mappedTypes6.ts (25 errors) ====
type T00<T> = { [P in keyof T]: T[P] };
type T01<T> = { [P in keyof T]?: T[P] };
type T02<T> = { [P in keyof T]+?: T[P] };
Expand Down Expand Up @@ -104,7 +114,6 @@ tests/cases/conformance/types/mapped/mappedTypes6.ts(120,4): error TS2540: Canno
z = z;
}


function f3<T>(w: Denullified<T>, x: Required<T>, y: T, z: Partial<T>) {
w = {}; // Error
~
Expand Down Expand Up @@ -135,6 +144,43 @@ tests/cases/conformance/types/mapped/mappedTypes6.ts(120,4): error TS2540: Canno
z = z;
}

type Nullified<T> = { [P in keyof T]?: Nullable<T[P]> };

function f11<T>(w: Nullified<T>, x: Required<T>, y: T, z: Partial<T>) {
w = w;
w = x;
w = y;
w = z;
x = w; // Error
~
!!! error TS2322: Type 'Nullified<T>' is not assignable to type 'Required<T>'.
x = x;
x = y; // Error
~
!!! error TS2322: Type 'T' is not assignable to type 'Required<T>'.
x = z; // Error
~
!!! error TS2322: Type 'Partial<T>' is not assignable to type 'Required<T>'.
y = w; // Error
~
!!! error TS2322: Type 'Nullified<T>' is not assignable to type 'T'.
!!! error TS2322: 'T' could be instantiated with an arbitrary type which could be unrelated to 'Nullified<T>'.
y = x;
y = y;
y = z; // Error
~
!!! error TS2322: Type 'Partial<T>' is not assignable to type 'T'.
!!! error TS2322: 'T' could be instantiated with an arbitrary type which could be unrelated to 'Partial<T>'.
z = w;
~
!!! error TS2322: Type 'Nullified<T>' is not assignable to type 'Partial<T>'.
!!! error TS2322: Type 'Nullable<T[P]>' is not assignable to type 'T[P] | undefined'.
!!! error TS2322: Type 'null' is not assignable to type 'T[P] | undefined'.
z = x;
z = y;
z = z;
}

type Foo = {
a: number;
b: number | undefined;
Expand All @@ -152,7 +198,7 @@ tests/cases/conformance/types/mapped/mappedTypes6.ts(120,4): error TS2540: Canno
x1 = { a: 1 }; // Error
~~
!!! error TS2741: Property 'b' is missing in type '{ a: number; }' but required in type 'Foo'.
!!! related TS2728 tests/cases/conformance/types/mapped/mappedTypes6.ts:80:5: 'b' is declared here.
!!! related TS2728 tests/cases/conformance/types/mapped/mappedTypes6.ts:100:5: 'b' is declared here.
x1 = { a: 1, b: 1 };
x1 = { a: 1, b: 1, c: 1 };
x1 = { a: 1, b: 1, c: 1, d: 1 };
Expand All @@ -173,7 +219,7 @@ tests/cases/conformance/types/mapped/mappedTypes6.ts(120,4): error TS2540: Canno
x2 = { a: 1, b: 1, c: 1 }; // Error
~~
!!! error TS2741: Property 'd' is missing in type '{ a: number; b: number; c: number; }' but required in type 'Required<Foo>'.
!!! related TS2728 tests/cases/conformance/types/mapped/mappedTypes6.ts:82:5: 'd' is declared here.
!!! related TS2728 tests/cases/conformance/types/mapped/mappedTypes6.ts:102:5: 'd' is declared here.
x2 = { a: 1, b: 1, c: 1, d: 1 };

type Bar = {
Expand Down
44 changes: 43 additions & 1 deletion tests/baselines/reference/mappedTypes6.js
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,6 @@ function f2<T>(w: Denullified<T>, x: Required<T>, y: T, z: Partial<T>) {
z = z;
}


function f3<T>(w: Denullified<T>, x: Required<T>, y: T, z: Partial<T>) {
w = {}; // Error
x = {}; // Error
Expand All @@ -76,6 +75,27 @@ function f10<T>(x: Readonly<T>, y: T, z: Readwrite<T>) {
z = z;
}

type Nullified<T> = { [P in keyof T]?: Nullable<T[P]> };

function f11<T>(w: Nullified<T>, x: Required<T>, y: T, z: Partial<T>) {
w = w;
w = x;
w = y;
w = z;
x = w; // Error
x = x;
x = y; // Error
x = z; // Error
y = w; // Error
y = x;
y = y;
y = z; // Error
z = w;
z = x;
z = y;
z = z;
}

type Foo = {
a: number;
b: number | undefined;
Expand Down Expand Up @@ -173,6 +193,24 @@ function f10(x, y, z) {
z = y;
z = z;
}
function f11(w, x, y, z) {
w = w;
w = x;
w = y;
w = z;
x = w; // Error
x = x;
x = y; // Error
x = z; // Error
y = w; // Error
y = x;
y = y;
y = z; // Error
z = w;
z = x;
z = y;
z = z;
}
x1.a; // number
x1.b; // number | undefined
x1.c; // number | undefined
Expand Down Expand Up @@ -256,6 +294,10 @@ declare type Readwrite<T> = {
-readonly [P in keyof T]: T[P];
};
declare function f10<T>(x: Readonly<T>, y: T, z: Readwrite<T>): void;
declare type Nullified<T> = {
[P in keyof T]?: Nullable<T[P]>;
};
declare function f11<T>(w: Nullified<T>, x: Required<T>, y: T, z: Partial<T>): void;
declare type Foo = {
a: number;
b: number | undefined;
Expand Down
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