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Infer intersected reverse mapped types #52062

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Infer intersected reverse mapped types #52062

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Infer intersected reverse mapped types
Andarist Jan 1, 2023
16b6d35
Merge remote-tracking branch 'origin/main' into infer-intersected-map…
Andarist Jan 16, 2023
25af013
Merge remote-tracking branch 'origin/main' into infer-intersected-map…
Andarist Jan 17, 2023
1d1cf87
Merge remote-tracking branch 'origin/main' into infer-intersected-map…
Andarist Mar 17, 2023
53acfd3
Merge remote-tracking branch 'origin/main' into infer-intersected-map…
Andarist Mar 20, 2023
56f12bc
Avoid getting apparent type of intersected mapped types in contextual…
Andarist Mar 20, 2023
294e907
Merge remote-tracking branch 'origin/main' into infer-intersected-map…
Andarist Jun 13, 2023
27805ec
Merge remote-tracking branch 'origin/main' into infer-intersected-map…
Andarist Dec 12, 2023
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20 changes: 12 additions & 8 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -15735,7 +15735,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const type = elementTypes[i];
const flags = target.elementFlags[i];
if (flags & ElementFlags.Variadic) {
if (type.flags & TypeFlags.InstantiableNonPrimitive || isGenericMappedType(type)) {
if (type.flags & TypeFlags.InstantiableNonPrimitive || everyContainedType(type, isGenericMappedType)) {
// Generic variadic elements stay as they are.
addElement(type, ElementFlags.Variadic, target.labeledElementDeclarations?.[i]);
}
Expand Down Expand Up @@ -28577,13 +28577,17 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {

function getTypeOfPropertyOfContextualType(type: Type, name: __String, nameType?: Type) {
return mapType(type, t => {
if (isGenericMappedType(t) && !t.declaration.nameType) {
const constraint = getConstraintTypeFromMappedType(t);
const constraintOfConstraint = getBaseConstraintOfType(constraint) || constraint;
const propertyNameType = nameType || getStringLiteralType(unescapeLeadingUnderscores(name));
if (isTypeAssignableTo(propertyNameType, constraintOfConstraint)) {
return substituteIndexedMappedType(t, propertyNameType);
}
if (everyContainedType(t, t => isGenericMappedType(t) && !t.declaration.nameType)) {
const newTypes = mapDefined(t.flags & TypeFlags.Intersection ? (t as IntersectionType).types : [t], t => {
const mappedType = t as MappedType;
const constraint = getConstraintTypeFromMappedType(mappedType);
const constraintOfConstraint = getBaseConstraintOfType(constraint) || constraint;
const propertyNameType = nameType || getStringLiteralType(unescapeLeadingUnderscores(name));
if (isTypeAssignableTo(propertyNameType, constraintOfConstraint)) {
return substituteIndexedMappedType(mappedType, propertyNameType);
}
});
return newTypes.length ? getIntersectionType(newTypes) : undefined;
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This will quietly elide intersection members whose substitution fails the isTypeAssignableTo(propertyNameType, constraintOfConstraint) check. I honestly can't think of how that could occur offhand, but I think to better mimic old behavior, since intersections are structured types, and would previously only take the other branch. If newTypes.length !== (t.flags & TypeFlags.Intersection ? (t as IntersectionType).types : [t]).length, we need to fall through to the StructuredType fallback below.

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@Andarist Andarist Mar 18, 2023 •
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I've tried a couple of things to hit such a case and I can't think of any. I can introduce the proposed change but personally I think that it should be accompanied with a test case. I understand the desire to match the old behavior but:

  1. if we manage to grab a concrete property in the branch responsible for structured types then this is basically the same thing as substituting indexed mapped type (so doing it within this branch responsible for generic mapped types leads to the same results already)
  2. if we manage to grab some index info there then I find it extremely unlikely there is a way to reach that branch of code if all intersected mapped type failed isTypeAssignableTo(propertyNameType, constraintOfConstraint) check. In a lot of situations, the constraintOfConstraint is already string | number | symbol and even when it's not... the index type has to come from one of the intersected members, so some of them had to pass this isTypeAssignableTo check and thus newTypes wouldn't be empty.
  3. The isTupleType is just impossible to be hit by intersections

So, all in all, I think that the requested change wouldn't be meaningful - but, ofc, I could be wrong here. And even if such intersections could today return something meaningful then that, I think, would be inconsistent with the isGenericMappedType(t) && !t.declaration.nameType branch. That's because that branch doesn't fallback to the branch related to structured types - even if isTypeAssignableTo(propertyNameType, constraintOfConstraint). So if this doesn't happen for generic mapped types - why should it happen for intersected ones? That would be an inconsistent behavior to me.

}
else if (t.flags & TypeFlags.StructuredType) {
const prop = getPropertyOfType(t, name);
Expand Down
188 changes: 188 additions & 0 deletions tests/baselines/reference/reverseMappedIntersectionInference.symbols
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@@ -0,0 +1,188 @@
=== tests/cases/compiler/reverseMappedIntersectionInference.ts ===
type Results<T> = {
>Results : Symbol(Results, Decl(reverseMappedIntersectionInference.ts, 0, 0))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 0, 13))

[K in keyof T]: {
>K : Symbol(K, Decl(reverseMappedIntersectionInference.ts, 1, 3))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 0, 13))

data: T[K];
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 1, 19))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 0, 13))
>K : Symbol(K, Decl(reverseMappedIntersectionInference.ts, 1, 3))

onSuccess: (data: T[K]) => void;
>onSuccess : Symbol(onSuccess, Decl(reverseMappedIntersectionInference.ts, 2, 15))
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 3, 16))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 0, 13))
>K : Symbol(K, Decl(reverseMappedIntersectionInference.ts, 1, 3))

};
};

type Errors<E> = {
>Errors : Symbol(Errors, Decl(reverseMappedIntersectionInference.ts, 5, 2))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 7, 12))

[K in keyof E]: {
>K : Symbol(K, Decl(reverseMappedIntersectionInference.ts, 8, 3))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 7, 12))

error: E[K];
>error : Symbol(error, Decl(reverseMappedIntersectionInference.ts, 8, 19))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 7, 12))
>K : Symbol(K, Decl(reverseMappedIntersectionInference.ts, 8, 3))

onError: (data: E[K]) => void;
>onError : Symbol(onError, Decl(reverseMappedIntersectionInference.ts, 9, 16))
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 10, 14))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 7, 12))
>K : Symbol(K, Decl(reverseMappedIntersectionInference.ts, 8, 3))

};
};

declare function withKeyedObj<T, E>(
>withKeyedObj : Symbol(withKeyedObj, Decl(reverseMappedIntersectionInference.ts, 12, 2))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 14, 30))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 14, 32))

arg: Results<T> & Errors<E>
>arg : Symbol(arg, Decl(reverseMappedIntersectionInference.ts, 14, 36))
>Results : Symbol(Results, Decl(reverseMappedIntersectionInference.ts, 0, 0))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 14, 30))
>Errors : Symbol(Errors, Decl(reverseMappedIntersectionInference.ts, 5, 2))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 14, 32))

): [T, E];
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 14, 30))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 14, 32))

const res = withKeyedObj({
>res : Symbol(res, Decl(reverseMappedIntersectionInference.ts, 18, 5))
>withKeyedObj : Symbol(withKeyedObj, Decl(reverseMappedIntersectionInference.ts, 12, 2))

a: {
>a : Symbol(a, Decl(reverseMappedIntersectionInference.ts, 18, 26))

data: "foo",
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 19, 6))

onSuccess: (dataArg) => {
>onSuccess : Symbol(onSuccess, Decl(reverseMappedIntersectionInference.ts, 20, 16))
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 21, 16))

dataArg;
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 21, 16))

},
error: 404,
>error : Symbol(error, Decl(reverseMappedIntersectionInference.ts, 23, 6))

onError: (errorArg) => {
>onError : Symbol(onError, Decl(reverseMappedIntersectionInference.ts, 24, 15))
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 25, 14))

errorArg;
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 25, 14))

},
},
b: {
>b : Symbol(b, Decl(reverseMappedIntersectionInference.ts, 28, 4))

data: true,
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 29, 6))

onSuccess: (dataArg) => {
>onSuccess : Symbol(onSuccess, Decl(reverseMappedIntersectionInference.ts, 30, 15))
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 31, 16))

dataArg;
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 31, 16))

},
error: 500,
>error : Symbol(error, Decl(reverseMappedIntersectionInference.ts, 33, 6))

onError: (errorArg) => {
>onError : Symbol(onError, Decl(reverseMappedIntersectionInference.ts, 34, 15))
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 35, 14))

errorArg;
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 35, 14))

},
},
});

declare function withTuples<T extends any[], E extends any[]>(
>withTuples : Symbol(withTuples, Decl(reverseMappedIntersectionInference.ts, 39, 3))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 41, 28))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 41, 44))

arg: [...(Results<T> & Errors<E>)]
>arg : Symbol(arg, Decl(reverseMappedIntersectionInference.ts, 41, 62))
>Results : Symbol(Results, Decl(reverseMappedIntersectionInference.ts, 0, 0))
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 41, 28))
>Errors : Symbol(Errors, Decl(reverseMappedIntersectionInference.ts, 5, 2))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 41, 44))

): [T, E];
>T : Symbol(T, Decl(reverseMappedIntersectionInference.ts, 41, 28))
>E : Symbol(E, Decl(reverseMappedIntersectionInference.ts, 41, 44))

const res2 = withTuples([
>res2 : Symbol(res2, Decl(reverseMappedIntersectionInference.ts, 45, 5))
>withTuples : Symbol(withTuples, Decl(reverseMappedIntersectionInference.ts, 39, 3))
{
data: "foo",
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 46, 3))

onSuccess: (dataArg) => {
>onSuccess : Symbol(onSuccess, Decl(reverseMappedIntersectionInference.ts, 47, 16))
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 48, 16))

dataArg;
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 48, 16))

},
error: 404,
>error : Symbol(error, Decl(reverseMappedIntersectionInference.ts, 50, 6))

onError: (errorArg) => {
>onError : Symbol(onError, Decl(reverseMappedIntersectionInference.ts, 51, 15))
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 52, 14))

errorArg;
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 52, 14))

},
},
{
data: true,
>data : Symbol(data, Decl(reverseMappedIntersectionInference.ts, 56, 3))

onSuccess: (dataArg) => {
>onSuccess : Symbol(onSuccess, Decl(reverseMappedIntersectionInference.ts, 57, 15))
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 58, 16))

dataArg;
>dataArg : Symbol(dataArg, Decl(reverseMappedIntersectionInference.ts, 58, 16))

},
error: 500,
>error : Symbol(error, Decl(reverseMappedIntersectionInference.ts, 60, 6))

onError: (errorArg) => {
>onError : Symbol(onError, Decl(reverseMappedIntersectionInference.ts, 61, 15))
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 62, 14))

errorArg;
>errorArg : Symbol(errorArg, Decl(reverseMappedIntersectionInference.ts, 62, 14))

},
},
]);

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