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Fixed an issue with not being able to use mapped type over union constraint as rest param #49947

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Merged
weswigham merged 7 commits into from
Mar 20, 2023
Merged

Fixed an issue with not being able to use mapped type over union constraint as rest param #49947

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6554965
Fixed an issue with not being able to use mapped type over union cons…
Andarist Jul 19, 2022
f94efbd
Fixed an issue when targeting non-readonly arrays with source being a…
Andarist Jul 29, 2022
ce8483c
Merge remote-tracking branch 'origin/main' into fix/rest-param-using-…
Andarist Dec 26, 2022
29d4bb9
Merge remote-tracking branch 'origin/main' into fix/rest-param-using-…
Andarist Mar 16, 2023
940e1ad
Bring back resolving apparent type for mapped types with tuple constr…
Andarist Mar 19, 2023
88764fe
Merge remote-tracking branch 'origin/main' into fix/rest-param-using-…
Andarist Mar 20, 2023
8e78414
Add extra test cases
Andarist Mar 20, 2023
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14 changes: 11 additions & 3 deletions src/compiler/checker.ts
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Expand Up @@ -13861,7 +13861,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const typeVariable = getHomomorphicTypeVariable(type);
if (typeVariable && !type.declaration.nameType) {
const constraint = getConstraintOfTypeParameter(typeVariable);
if (constraint && isArrayType(constraint)) {
if (constraint && everyType(constraint, isArrayOrTupleType)) {
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@Andarist Andarist Mar 19, 2023

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In a way, this reverts the recent change from #52651 . That issue is now fixed by avoiding getting the apparent type of mapped types within getApparentTypeOfContextualType - you can see the change in the commit here

I think this is a better fix for that issue anyway, I just didn't figure it out earlier. Getting the "resolved" apparent type for mapped types with tuple constraint (and array) constraints is important for relationship checking. The mapped type that resolves~ to a tuple is usually "normalized" here, that allows tuple/array-oriented branches to relate things.

return instantiateType(type, prependTypeMapping(typeVariable, constraint, type.mapper));
}
}
Expand Down Expand Up @@ -21655,7 +21655,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return varianceResult;
}
}
else if (isReadonlyArrayType(target) ? isArrayOrTupleType(source) : isArrayType(target) && isTupleType(source) && !source.target.readonly) {
else if (isReadonlyArrayType(target) ? everyType(source, isArrayOrTupleType) : isArrayType(target) && everyType(source, t => isTupleType(t) && !t.target.readonly)) {
if (relation !== identityRelation) {
return isRelatedTo(getIndexTypeOfType(source, numberType) || anyType, getIndexTypeOfType(target, numberType) || anyType, RecursionFlags.Both, reportErrors);
}
Expand Down Expand Up @@ -29205,7 +29205,15 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
getContextualType(node, contextFlags);
const instantiatedType = instantiateContextualType(contextualType, node, contextFlags);
if (instantiatedType && !(contextFlags && contextFlags & ContextFlags.NoConstraints && instantiatedType.flags & TypeFlags.TypeVariable)) {
const apparentType = mapType(instantiatedType, getApparentType, /*noReductions*/ true);
const apparentType = mapType(
instantiatedType,
// When obtaining apparent type of *contextual* type we don't want to get apparent type of mapped types.
// That would evaluate mapped types with array or tuple type constraints too eagerly
// and thus it would prevent `getTypeOfPropertyOfContextualType` from obtaining per-position contextual type for elements of array literal expressions.
// Apparent type of other mapped types is already the mapped type itself so we can just avoid calling `getApparentType` here for all mapped types.
t => getObjectFlags(t) & ObjectFlags.Mapped ? t : getApparentType(t),
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@Andarist Andarist Mar 19, 2023

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This might also need to handle intersections better, their mapped types parts should be left alone similarly. I don't have a test case to validate this at hand though so I refrained from making further changes to this. However, I think that I know how to write a sensible test case for this with the changes from this PR. So I would like to wait for one of them to land so I could tweak this part of the code and add the appropriate test case to the other PR.

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@Andarist Andarist Mar 20, 2023

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And I pushed out this extra fix here: 56f12bc

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@weswigham weswigham Mar 20, 2023

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Would you care to open a new PR for the further improvement? Since it comes with a test case proving it's utility, it looks pretty good - will just need to make sure the extended suites stay clean when that handling is in place.

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Oh, I thought that this would be linked better - this commit is already part of the #52062 :) it only made sense for me to add this change there as that PR was already concerned with intersected mapped types and thus I already had an idea what a test to write there for this patch

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Ahh, OK.

/*noReductions*/ true
);
return apparentType.flags & TypeFlags.Union && isObjectLiteralExpression(node) ? discriminateContextualTypeByObjectMembers(node, apparentType as UnionType) :
apparentType.flags & TypeFlags.Union && isJsxAttributes(node) ? discriminateContextualTypeByJSXAttributes(node, apparentType as UnionType) :
apparentType;
Expand Down
18 changes: 18 additions & 0 deletions tests/baselines/reference/mappedTypeUnionConstrainTupleTreatedAsArrayLike.errors.txt
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@@ -0,0 +1,18 @@
tests/cases/compiler/mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts(9,9): error TS2322: Type 'HomomorphicMappedType<T>' is not assignable to type 'any[]'.


==== tests/cases/compiler/mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts (1 errors) ====
type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }

function test1<T extends [number] | [string]>(args: T) {
const arr: any[] = [] as HomomorphicMappedType<T>
const arr2: readonly any[] = [] as HomomorphicMappedType<T>
}

function test2<T extends [number] | readonly [string]>(args: T) {
const arr: any[] = [] as HomomorphicMappedType<T> // error
~~~
!!! error TS2322: Type 'HomomorphicMappedType<T>' is not assignable to type 'any[]'.
const arr2: readonly any[] = [] as HomomorphicMappedType<T>
}

43 changes: 43 additions & 0 deletions tests/baselines/reference/mappedTypeUnionConstrainTupleTreatedAsArrayLike.symbols
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=== tests/cases/compiler/mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts ===
type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 0))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 27))
>P : Symbol(P, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 35))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 27))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 27))
>P : Symbol(P, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 35))

function test1<T extends [number] | [string]>(args: T) {
>test1 : Symbol(test1, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 88))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 2, 15))
>args : Symbol(args, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 2, 46))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 2, 15))

const arr: any[] = [] as HomomorphicMappedType<T>
>arr : Symbol(arr, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 3, 7))
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 0))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 2, 15))

const arr2: readonly any[] = [] as HomomorphicMappedType<T>
>arr2 : Symbol(arr2, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 4, 7))
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 0))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 2, 15))
}

function test2<T extends [number] | readonly [string]>(args: T) {
>test2 : Symbol(test2, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 5, 1))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 7, 15))
>args : Symbol(args, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 7, 55))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 7, 15))

const arr: any[] = [] as HomomorphicMappedType<T> // error
>arr : Symbol(arr, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 8, 7))
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 0))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 7, 15))

const arr2: readonly any[] = [] as HomomorphicMappedType<T>
>arr2 : Symbol(arr2, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 9, 7))
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 0, 0))
>T : Symbol(T, Decl(mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts, 7, 15))
}

34 changes: 34 additions & 0 deletions tests/baselines/reference/mappedTypeUnionConstrainTupleTreatedAsArrayLike.types
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@@ -0,0 +1,34 @@
=== tests/cases/compiler/mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts ===
type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }
>HomomorphicMappedType : HomomorphicMappedType<T>

function test1<T extends [number] | [string]>(args: T) {
>test1 : <T extends [number] | [string]>(args: T) => void
>args : T

const arr: any[] = [] as HomomorphicMappedType<T>
>arr : any[]
>[] as HomomorphicMappedType<T> : HomomorphicMappedType<T>
>[] : []

const arr2: readonly any[] = [] as HomomorphicMappedType<T>
>arr2 : readonly any[]
>[] as HomomorphicMappedType<T> : HomomorphicMappedType<T>
>[] : []
}

function test2<T extends [number] | readonly [string]>(args: T) {
>test2 : <T extends [number] | readonly [string]>(args: T) => void
>args : T

const arr: any[] = [] as HomomorphicMappedType<T> // error
>arr : any[]
>[] as HomomorphicMappedType<T> : HomomorphicMappedType<T>
>[] : []

const arr2: readonly any[] = [] as HomomorphicMappedType<T>
>arr2 : readonly any[]
>[] as HomomorphicMappedType<T> : HomomorphicMappedType<T>
>[] : []
}

27 changes: 27 additions & 0 deletions tests/baselines/reference/restParamUsingMappedTypeOverUnionConstraint.symbols
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=== tests/cases/compiler/restParamUsingMappedTypeOverUnionConstraint.ts ===
// repro 29919#issuecomment-470948453

type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 0, 0))
>T : Symbol(T, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 2, 27))
>P : Symbol(P, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 2, 35))
>T : Symbol(T, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 2, 27))
>T : Symbol(T, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 2, 27))
>P : Symbol(P, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 2, 35))

declare function test<T extends [number] | [string]>(
>test : Symbol(test, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 2, 88))
>T : Symbol(T, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 4, 22))

args: T,
>args : Symbol(args, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 4, 53))
>T : Symbol(T, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 4, 22))

fn: (...args: HomomorphicMappedType<T>) => void
>fn : Symbol(fn, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 5, 10))
>args : Symbol(args, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 6, 7))
>HomomorphicMappedType : Symbol(HomomorphicMappedType, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 0, 0))
>T : Symbol(T, Decl(restParamUsingMappedTypeOverUnionConstraint.ts, 4, 22))

): void

18 changes: 18 additions & 0 deletions tests/baselines/reference/restParamUsingMappedTypeOverUnionConstraint.types
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=== tests/cases/compiler/restParamUsingMappedTypeOverUnionConstraint.ts ===
// repro 29919#issuecomment-470948453

type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }
>HomomorphicMappedType : HomomorphicMappedType<T>

declare function test<T extends [number] | [string]>(
>test : <T extends [number] | [string]>(args: T, fn: (...args: HomomorphicMappedType<T>) => void) => void

args: T,
>args : T

fn: (...args: HomomorphicMappedType<T>) => void
>fn : (...args: HomomorphicMappedType<T>) => void
>args : HomomorphicMappedType<T>

): void

14 changes: 14 additions & 0 deletions tests/cases/compiler/mappedTypeUnionConstrainTupleTreatedAsArrayLike.ts
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// @noEmit: true
// @strict: true

type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }

function test1<T extends [number] | [string]>(args: T) {
const arr: any[] = [] as HomomorphicMappedType<T>
const arr2: readonly any[] = [] as HomomorphicMappedType<T>
}

function test2<T extends [number] | readonly [string]>(args: T) {
const arr: any[] = [] as HomomorphicMappedType<T> // error
const arr2: readonly any[] = [] as HomomorphicMappedType<T>
}
11 changes: 11 additions & 0 deletions tests/cases/compiler/restParamUsingMappedTypeOverUnionConstraint.ts
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// @noEmit: true
// @strict: true

// repro 29919#issuecomment-470948453

type HomomorphicMappedType<T> = { [P in keyof T]: T[P] extends string ? boolean : null }

declare function test<T extends [number] | [string]>(
args: T,
fn: (...args: HomomorphicMappedType<T>) => void
): void