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Merged
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Dec 12, 2018
Merged

Simplify indexed access types applied to mapped types #28965

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44116b5
Simplify indexed accesses on mapped types up to five levels deep
ahejlsberg Dec 11, 2018
2150a64
Add tests
ahejlsberg Dec 11, 2018
02b13a9
Accept new baselines
ahejlsberg Dec 11, 2018
0dcaaa5
Simplify indexed accesses on mapped types with no depth limit
ahejlsberg Dec 11, 2018
77d01ab
Update tests
ahejlsberg Dec 11, 2018
c3a9394
Accept new baselines
ahejlsberg Dec 11, 2018
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19 changes: 4 additions & 15 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9686,26 +9686,15 @@ namespace ts {

// If the object type is a mapped type { [P in K]: E }, where K is generic, instantiate E using a mapper
// that substitutes the index type for P. For example, for an index access { [P in K]: Box<T[P]> }[X], we
// construct the type Box<T[X]>. We do not further simplify the result because mapped types can be recursive
// and we might never terminate.
// construct the type Box<T[X]>.
if (isGenericMappedType(objectType)) {
return type.simplified = substituteIndexedMappedType(objectType, type);
}
if (objectType.flags & TypeFlags.TypeParameter) {
const constraint = getConstraintOfTypeParameter(objectType as TypeParameter);
if (constraint && isGenericMappedType(constraint)) {
return type.simplified = substituteIndexedMappedType(constraint, type);
}
const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [type.indexType]);
const templateMapper = combineTypeMappers(objectType.mapper, mapper);
return type.simplified = mapType(instantiateType(getTemplateTypeFromMappedType(objectType), templateMapper), getSimplifiedType);
}
return type.simplified = type;
}

function substituteIndexedMappedType(objectType: MappedType, type: IndexedAccessType) {
const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [type.indexType]);
const templateMapper = combineTypeMappers(objectType.mapper, mapper);
return instantiateType(getTemplateTypeFromMappedType(objectType), templateMapper);
}

function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode | PropertyName, missingType = accessNode ? errorType : unknownType): Type {
if (objectType === wildcardType || indexType === wildcardType) {
return wildcardType;
Expand Down
8 changes: 3 additions & 5 deletions tests/baselines/reference/keyofAndIndexedAccess.js
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Expand Up @@ -484,10 +484,10 @@ function onChangeGenericFunction<T>(handler: Handler<T & {preset: number}>) {
function updateIds<T extends Record<K, string>, K extends string>(
obj: T,
idFields: K[],
idMapping: { [oldId: string]: string }
idMapping: Partial<Record<T[K], T[K]>>
): Record<K, string> {
for (const idField of idFields) {
const newId = idMapping[obj[idField]];
const newId: T[K] | undefined = idMapping[obj[idField]];
if (newId) {
obj[idField] = newId;
}
Expand Down Expand Up @@ -1312,9 +1312,7 @@ declare type Handler<T> = {
declare function onChangeGenericFunction<T>(handler: Handler<T & {
preset: number;
}>): void;
declare function updateIds<T extends Record<K, string>, K extends string>(obj: T, idFields: K[], idMapping: {
[oldId: string]: string;
}): Record<K, string>;
declare function updateIds<T extends Record<K, string>, K extends string>(obj: T, idFields: K[], idMapping: Partial<Record<T[K], T[K]>>): Record<K, string>;
declare function updateIds2<T extends {
[x: string]: string;
}, K extends keyof T>(obj: T, key: K, stringMap: {
Expand Down
13 changes: 10 additions & 3 deletions tests/baselines/reference/keyofAndIndexedAccess.symbols
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Expand Up @@ -1767,9 +1767,14 @@ function updateIds<T extends Record<K, string>, K extends string>(
>idFields : Symbol(idFields, Decl(keyofAndIndexedAccess.ts, 483, 11))
>K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 482, 47))

idMapping: { [oldId: string]: string }
idMapping: Partial<Record<T[K], T[K]>>
>idMapping : Symbol(idMapping, Decl(keyofAndIndexedAccess.ts, 484, 18))
>oldId : Symbol(oldId, Decl(keyofAndIndexedAccess.ts, 485, 18))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
>T : Symbol(T, Decl(keyofAndIndexedAccess.ts, 482, 19))
>K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 482, 47))
>T : Symbol(T, Decl(keyofAndIndexedAccess.ts, 482, 19))
>K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 482, 47))

): Record<K, string> {
>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
Expand All @@ -1779,8 +1784,10 @@ function updateIds<T extends Record<K, string>, K extends string>(
>idField : Symbol(idField, Decl(keyofAndIndexedAccess.ts, 487, 14))
>idFields : Symbol(idFields, Decl(keyofAndIndexedAccess.ts, 483, 11))

const newId = idMapping[obj[idField]];
const newId: T[K] | undefined = idMapping[obj[idField]];
>newId : Symbol(newId, Decl(keyofAndIndexedAccess.ts, 488, 13))
>T : Symbol(T, Decl(keyofAndIndexedAccess.ts, 482, 19))
>K : Symbol(K, Decl(keyofAndIndexedAccess.ts, 482, 47))
>idMapping : Symbol(idMapping, Decl(keyofAndIndexedAccess.ts, 484, 18))
>obj : Symbol(obj, Decl(keyofAndIndexedAccess.ts, 482, 66))
>idField : Symbol(idField, Decl(keyofAndIndexedAccess.ts, 487, 14))
Expand Down
21 changes: 10 additions & 11 deletions tests/baselines/reference/keyofAndIndexedAccess.types
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Expand Up @@ -1731,40 +1731,39 @@ function onChangeGenericFunction<T>(handler: Handler<T & {preset: number}>) {
// Repro from #13285

function updateIds<T extends Record<K, string>, K extends string>(
>updateIds : <T extends Record<K, string>, K extends string>(obj: T, idFields: K[], idMapping: { [oldId: string]: string; }) => Record<K, string>
>updateIds : <T extends Record<K, string>, K extends string>(obj: T, idFields: K[], idMapping: Partial<Record<T[K], T[K]>>) => Record<K, string>

obj: T,
>obj : T

idFields: K[],
>idFields : K[]

idMapping: { [oldId: string]: string }
>idMapping : { [oldId: string]: string; }
>oldId : string
idMapping: Partial<Record<T[K], T[K]>>
>idMapping : Partial<Record<T[K], T[K]>>

): Record<K, string> {
for (const idField of idFields) {
>idField : K
>idFields : K[]

const newId = idMapping[obj[idField]];
>newId : { [oldId: string]: string; }[T[K]]
>idMapping[obj[idField]] : { [oldId: string]: string; }[T[K]]
>idMapping : { [oldId: string]: string; }
const newId: T[K] | undefined = idMapping[obj[idField]];
>newId : T[K] | undefined
>idMapping[obj[idField]] : Partial<Record<T[K], T[K]>>[T[K]]
>idMapping : Partial<Record<T[K], T[K]>>
>obj[idField] : T[K]
>obj : T
>idField : K

if (newId) {
>newId : { [oldId: string]: string; }[T[K]]
>newId : T[K] | undefined

obj[idField] = newId;
>obj[idField] = newId : { [oldId: string]: string; }[T[K]]
>obj[idField] = newId : T[K]
>obj[idField] : T[K]
>obj : T
>idField : K
>newId : { [oldId: string]: string; }[T[K]]
>newId : T[K]
}
}
return obj;
Expand Down
10 changes: 10 additions & 0 deletions tests/baselines/reference/keyofAndIndexedAccessErrors.errors.txt
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Expand Up @@ -321,4 +321,14 @@ tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(142,5): error
~~~~
!!! error TS2322: Type 'number[]' is not assignable to type 'T[K]'.
}

// Repro from #28839

function f30<T, K extends keyof T>() {
let x: Partial<Record<keyof T, string>>[K] = "hello";
}

function f31<T, K extends keyof T>() {
let x: Partial<Partial<Partial<Partial<Partial<Partial<Partial<Record<keyof T, string>>>>>>>>[K] = "hello";
}

17 changes: 17 additions & 0 deletions tests/baselines/reference/keyofAndIndexedAccessErrors.js
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Expand Up @@ -142,6 +142,16 @@ function test1<T extends Record<string, any>, K extends keyof T>(t: T, k: K) {
t[k] = "hello"; // Error
t[k] = [10, 20]; // Error
}

// Repro from #28839

function f30<T, K extends keyof T>() {
let x: Partial<Record<keyof T, string>>[K] = "hello";
}

function f31<T, K extends keyof T>() {
let x: Partial<Partial<Partial<Partial<Partial<Partial<Partial<Record<keyof T, string>>>>>>>>[K] = "hello";
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Aside: Part of me wonders if we should have come rule in place to compact mapped types like this, even when generic.

}


//// [keyofAndIndexedAccessErrors.js]
Expand Down Expand Up @@ -215,3 +225,10 @@ function test1(t, k) {
t[k] = "hello"; // Error
t[k] = [10, 20]; // Error
}
// Repro from #28839
function f30() {
var x = "hello";
}
function f31() {
var x = "hello";
}
36 changes: 36 additions & 0 deletions tests/baselines/reference/keyofAndIndexedAccessErrors.symbols
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Expand Up @@ -486,3 +486,39 @@ function test1<T extends Record<string, any>, K extends keyof T>(t: T, k: K) {
>k : Symbol(k, Decl(keyofAndIndexedAccessErrors.ts, 138, 70))
}

// Repro from #28839

function f30<T, K extends keyof T>() {
>f30 : Symbol(f30, Decl(keyofAndIndexedAccessErrors.ts, 142, 1))
>T : Symbol(T, Decl(keyofAndIndexedAccessErrors.ts, 146, 13))
>K : Symbol(K, Decl(keyofAndIndexedAccessErrors.ts, 146, 15))
>T : Symbol(T, Decl(keyofAndIndexedAccessErrors.ts, 146, 13))

let x: Partial<Record<keyof T, string>>[K] = "hello";
>x : Symbol(x, Decl(keyofAndIndexedAccessErrors.ts, 147, 7))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
>T : Symbol(T, Decl(keyofAndIndexedAccessErrors.ts, 146, 13))
>K : Symbol(K, Decl(keyofAndIndexedAccessErrors.ts, 146, 15))
}

function f31<T, K extends keyof T>() {
>f31 : Symbol(f31, Decl(keyofAndIndexedAccessErrors.ts, 148, 1))
>T : Symbol(T, Decl(keyofAndIndexedAccessErrors.ts, 150, 13))
>K : Symbol(K, Decl(keyofAndIndexedAccessErrors.ts, 150, 15))
>T : Symbol(T, Decl(keyofAndIndexedAccessErrors.ts, 150, 13))

let x: Partial<Partial<Partial<Partial<Partial<Partial<Partial<Record<keyof T, string>>>>>>>>[K] = "hello";
>x : Symbol(x, Decl(keyofAndIndexedAccessErrors.ts, 151, 7))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
>T : Symbol(T, Decl(keyofAndIndexedAccessErrors.ts, 150, 13))
>K : Symbol(K, Decl(keyofAndIndexedAccessErrors.ts, 150, 15))
}

18 changes: 18 additions & 0 deletions tests/baselines/reference/keyofAndIndexedAccessErrors.types
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Expand Up @@ -465,3 +465,21 @@ function test1<T extends Record<string, any>, K extends keyof T>(t: T, k: K) {
>20 : 20
}

// Repro from #28839

function f30<T, K extends keyof T>() {
>f30 : <T, K extends keyof T>() => void

let x: Partial<Record<keyof T, string>>[K] = "hello";
>x : Partial<Record<keyof T, string>>[K]
>"hello" : "hello"
}

function f31<T, K extends keyof T>() {
>f31 : <T, K extends keyof T>() => void

let x: Partial<Partial<Partial<Partial<Partial<Partial<Partial<Record<keyof T, string>>>>>>>>[K] = "hello";
>x : Partial<Partial<Partial<Partial<Partial<Partial<Partial<Record<keyof T, string>>>>>>>>[K]
>"hello" : "hello"
}

4 changes: 2 additions & 2 deletions tests/cases/conformance/types/keyof/keyofAndIndexedAccess.ts
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Expand Up @@ -486,10 +486,10 @@ function onChangeGenericFunction<T>(handler: Handler<T & {preset: number}>) {
function updateIds<T extends Record<K, string>, K extends string>(
obj: T,
idFields: K[],
idMapping: { [oldId: string]: string }
idMapping: Partial<Record<T[K], T[K]>>
): Record<K, string> {
for (const idField of idFields) {
const newId = idMapping[obj[idField]];
const newId: T[K] | undefined = idMapping[obj[idField]];
if (newId) {
obj[idField] = newId;
}
Expand Down
10 changes: 10 additions & 0 deletions tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts
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Expand Up @@ -141,3 +141,13 @@ function test1<T extends Record<string, any>, K extends keyof T>(t: T, k: K) {
t[k] = "hello"; // Error
t[k] = [10, 20]; // Error
}

// Repro from #28839

function f30<T, K extends keyof T>() {
let x: Partial<Record<keyof T, string>>[K] = "hello";
}

function f31<T, K extends keyof T>() {
let x: Partial<Partial<Partial<Partial<Partial<Partial<Partial<Record<keyof T, string>>>>>>>>[K] = "hello";
}