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Better typings for Array.map() #33832

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Better typings for Array.map() #33832

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4 changes: 2 additions & 2 deletions src/lib/es5.d.ts
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Expand Up @@ -1138,7 +1138,7 @@ interface ReadonlyArray<T> {
* @param callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
* @param thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
*/
map<U>(callbackfn: (value: T, index: number, array: readonly T[]) => U, thisArg?: any): U[];
map<U>(callbackfn: (value: T, index: number, array: readonly T[]) => U, thisArg?: any): { -readonly [P in keyof this]: U } extends U[] ? { -readonly [P in keyof this]: U } : U[];
/**
* Returns the elements of an array that meet the condition specified in a callback function.
* @param callbackfn A function that accepts up to three arguments. The filter method calls the callbackfn function one time for each element in the array.
Expand Down Expand Up @@ -1308,7 +1308,7 @@ interface Array<T> {
* @param callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
* @param thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
*/
map<U>(callbackfn: (value: T, index: number, array: T[]) => U, thisArg?: any): U[];
map<U>(callbackfn: (value: T, index: number, array: T[]) => U, thisArg?: any): { -readonly [P in keyof this]: U } extends U[] ? { -readonly [P in keyof this]: U } : U[];
/**
* Returns the elements of an array that meet the condition specified in a callback function.
* @param callbackfn A function that accepts up to three arguments. The filter method calls the callbackfn function one time for each element in the array.
Expand Down
5 changes: 4 additions & 1 deletion tests/baselines/reference/arityAndOrderCompatibility01.errors.txt
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@@ -1,4 +1,5 @@
tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(15,12): error TS2493: Tuple type '[string, number]' of length '2' has no element at index '2'.
tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(16,5): error TS2461: Type 'StrNum' is not an array type.
tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(17,5): error TS2461: Type '{ 0: string; 1: number; length: 2; }' is not an array type.
tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(18,5): error TS2741: Property '2' is missing in type '[string, number]' but required in type '[number, number, number]'.
tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(19,5): error TS2741: Property '2' is missing in type 'StrNum' but required in type '[number, number, number]'.
Expand Down Expand Up @@ -28,7 +29,7 @@ tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(31,5): error
tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(32,5): error TS2322: Type '{ 0: string; 1: number; length: 2; }' is not assignable to type '[number, string]'.


==== tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts (17 errors) ====
==== tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts (18 errors) ====
interface StrNum extends Array<string|number> {
0: string;
1: number;
Expand All @@ -47,6 +48,8 @@ tests/cases/conformance/types/tuple/arityAndOrderCompatibility01.ts(32,5): error
~
!!! error TS2493: Tuple type '[string, number]' of length '2' has no element at index '2'.
var [d, e, f] = y;
~~~~~~~~~
!!! error TS2461: Type 'StrNum' is not an array type.
var [g, h, i] = z;
~~~~~~~~~
!!! error TS2461: Type '{ 0: string; 1: number; length: 2; }' is not an array type.
Expand Down
6 changes: 3 additions & 3 deletions tests/baselines/reference/arityAndOrderCompatibility01.types
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Expand Up @@ -36,9 +36,9 @@ var [a, b, c] = x;
>x : [string, number]

var [d, e, f] = y;
>d : string
>e : number
>f : string | number
>d : any
>e : any
>f : any
>y : StrNum

var [g, h, i] = z;
Expand Down
39 changes: 38 additions & 1 deletion tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.errors.txt
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@@ -1,12 +1,29 @@
tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(13,1): error TS2322: Type 'A[]' is not assignable to type 'readonly B[]'.
Property 'b' is missing in type 'A' but required in type 'B'.
tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(15,1): error TS2322: Type 'C<A>' is not assignable to type 'readonly A[]'.
The types returned by 'map(...)' are incompatible between these types.
Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]' is not assignable to type 'U[]'.
Type 'U[] | { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
Types of property 'length' are incompatible.
Type 'U' is not assignable to type 'number'.
tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(16,1): error TS2322: Type 'C<B>' is not assignable to type 'readonly A[]'.
The types returned by 'map(...)' are incompatible between these types.
Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]' is not assignable to type 'U[]'.
Type 'U[] | { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
Types of property 'length' are incompatible.
Type 'U' is not assignable to type 'number'.
tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(17,1): error TS2322: Type 'C<B>' is not assignable to type 'readonly B[]'.
The types returned by 'map(...)' are incompatible between these types.
Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]' is not assignable to type 'U[]'.
tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(18,1): error TS2322: Type 'C<A>' is not assignable to type 'readonly B[]'.
The types returned by 'concat(...)' are incompatible between these types.
Type 'A[]' is not assignable to type 'B[]'.
Type 'A' is not assignable to type 'B'.


==== tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts (2 errors) ====
==== tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts (5 errors) ====
class A { a }
class B extends A { b }
class C<T> extends Array<T> { c }
Expand All @@ -26,8 +43,28 @@ tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(18,1): error T
!!! related TS2728 tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts:2:21: 'b' is declared here.

rra = cra;
~~~
!!! error TS2322: Type 'C<A>' is not assignable to type 'readonly A[]'.
!!! error TS2322: The types returned by 'map(...)' are incompatible between these types.
!!! error TS2322: Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]' is not assignable to type 'U[]'.
!!! error TS2322: Type 'U[] | { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
!!! error TS2322: Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
!!! error TS2322: Types of property 'length' are incompatible.
!!! error TS2322: Type 'U' is not assignable to type 'number'.
rra = crb; // OK, C<B> is assignable to ReadonlyArray<A>
~~~
!!! error TS2322: Type 'C<B>' is not assignable to type 'readonly A[]'.
!!! error TS2322: The types returned by 'map(...)' are incompatible between these types.
!!! error TS2322: Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]' is not assignable to type 'U[]'.
!!! error TS2322: Type 'U[] | { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
!!! error TS2322: Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; }' is not assignable to type 'U[]'.
!!! error TS2322: Types of property 'length' are incompatible.
!!! error TS2322: Type 'U' is not assignable to type 'number'.
rrb = crb;
~~~
!!! error TS2322: Type 'C<B>' is not assignable to type 'readonly B[]'.
!!! error TS2322: The types returned by 'map(...)' are incompatible between these types.
!!! error TS2322: Type '{ [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; c: U; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]' is not assignable to type 'U[]'.
rrb = cra; // error: 'A' is not assignable to 'B'
~~~
!!! error TS2322: Type 'C<A>' is not assignable to type 'readonly B[]'.
Expand Down
36 changes: 36 additions & 0 deletions tests/baselines/reference/bestChoiceType.errors.txt
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@@ -0,0 +1,36 @@
tests/cases/compiler/bestChoiceType.ts(3,23): error TS2349: This expression is not callable.
Each member of the union type '(<U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]) | (<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any) => U[])' has signatures, but none of those signatures are compatible with each other.
tests/cases/compiler/bestChoiceType.ts(10,15): error TS2349: This expression is not callable.
Each member of the union type '(<U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]) | (<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any) => U[])' has signatures, but none of those signatures are compatible with each other.
tests/cases/compiler/bestChoiceType.ts(16,15): error TS2349: This expression is not callable.
Each member of the union type '(<U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]) | (<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any) => U[])' has signatures, but none of those signatures are compatible with each other.


==== tests/cases/compiler/bestChoiceType.ts (3 errors) ====
// Repro from #10041

(''.match(/ /) || []).map(s => s.toLowerCase());
~~~
!!! error TS2349: This expression is not callable.
!!! error TS2349: Each member of the union type '(<U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]) | (<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any) => U[])' has signatures, but none of those signatures are compatible with each other.

// Similar cases

function f1() {
let x = ''.match(/ /);
let y = x || [];
let z = y.map(s => s.toLowerCase());
~~~
!!! error TS2349: This expression is not callable.
!!! error TS2349: Each member of the union type '(<U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]) | (<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any) => U[])' has signatures, but none of those signatures are compatible with each other.
}

function f2() {
let x = ''.match(/ /);
let y = x ? x : [];
let z = y.map(s => s.toLowerCase());
~~~
!!! error TS2349: This expression is not callable.
!!! error TS2349: Each member of the union type '(<U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } extends U[] ? { [x: number]: U; index?: U | undefined; input?: U | undefined; length: U; toString: U; toLocaleString: U; pop: U; push: U; concat: U; join: U; reverse: U; shift: U; slice: U; sort: U; splice: U; unshift: U; indexOf: U; lastIndexOf: U; every: U; some: U; forEach: U; map: U; filter: U; reduce: U; reduceRight: U; } : U[]) | (<U>(callbackfn: (value: never, index: number, array: never[]) => U, thisArg?: any) => U[])' has signatures, but none of those signatures are compatible with each other.
}

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