Add optionality to mapped type indexed access substitutions #57549
Conversation
typescript-bot
added
Author: Team
For Uncommitted Bug
|
@typescript-bot test top200 |
|
Heya @ahejlsberg, I've started to run the faster perf test suite on this PR at ab3184b. You can monitor the build here. Update: The results are in! |
|
Heya @ahejlsberg, I've started to run the diff-based top-repos suite on this PR at ab3184b. You can monitor the build here. Update: The results are in! |
|
Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at ab3184b. You can monitor the build here. Update: The results are in! |
|
Heya @ahejlsberg, I've started to run the diff-based user code test suite on this PR at ab3184b. You can monitor the build here. Update: The results are in! |
|
@ahejlsberg Here are the results of running the user test suite comparing There were infrastructure failures potentially unrelated to your change:
Otherwise... Something interesting changed - please have a look. Details
|
|
@ahejlsberg Here they are:
tscComparison Report - baseline..pr
System info unknown
Hosts
Scenarios
Developer Information: |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Hey @ahejlsberg, the results of running the DT tests are ready. |
| getObjectFlags(type) & ObjectFlags.Mapped ? getMappedTypeOptionality(type as MappedType) : | ||
| 0; | ||
| } | ||
|
|
||
| function getCombinedMappedTypeOptionality(type: MappedType): number { |
There was a problem hiding this comment.
If I'm not mistaken this currently falls short here:
type Obj = {
a: 1,
b: 2
};
type Identity<T> = { [K in keyof T]: T[K] };
const mapped: {
[K in keyof Identity<Partial<Obj>>]: Obj[K]
} = {}
const resolveMapped = <K extends keyof typeof mapped>(key: K) => mapped[key].toString(); // should error but it doesntSome extra handling of homomorphic mapped types might have to be added here.
There was a problem hiding this comment.
Yeah, looks like we need to recurse in getCombinedMappedTypeOptionality.
|
@ahejlsberg Here are the results of running the top-repos suite comparing Everything looks good! |
| @@ -18517,7 +18521,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| function substituteIndexedMappedType(objectType: MappedType, index: Type) { | |||
| const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]); | |||
| const templateMapper = combineTypeMappers(objectType.mapper, mapper); | |||
| return instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper); | |||
| const instantiatedTemplateType = instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper); | |||
| return addOptionality(instantiatedTemplateType, /*isProperty*/ true, getCombinedMappedTypeOptionality(objectType) > 0); | |||
There was a problem hiding this comment.
Taking known properties into consideration would fix this inconsistency that this PR creates:
type Obj = {
a: string;
b: number;
};
type Obj2 = {
b: number;
c: boolean;
};
declare const mapped: {
[K in keyof (Partial<Obj> & Required<Obj2>)]: number;
};
// displays the same way as `resolved` below!
mapped;
// ^? const mapped: { a?: number | undefined; b: number; c: number; }
const accessMapped = <K extends keyof Obj2>(key: K) => mapped[key].toString();
declare const resolved: { a?: number | undefined; b: number; c: number };
const accessResolved = <K extends keyof Obj2>(key: K) => resolved[key].toString();There was a problem hiding this comment.
Right, when mapping over intersections constructed from multiple mapped types the PR makes the most conservative assumption about optionality. I think that's an acceptable compromise and I'm concerned with the potential cost of examining every member possibly selected by the key.
| @@ -14040,10 +14040,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| return modifiers & MappedTypeModifiers.ExcludeOptional ? -1 : modifiers & MappedTypeModifiers.IncludeOptional ? 1 : 0; | |||
| } | |||
|
|
|||
| function getModifiersTypeOptionality(type: Type): number { | |||
There was a problem hiding this comment.
I don't understand what this is computing. What does a result of 2 mean?
There was a problem hiding this comment.
The result is always either -1, 0, or 1. -1 means optionality is stripped (i.e. -?), 0 means optionality is unchanged, 1 means optionality is added (i.e. +?). When a homomorphic mapped type doesn't modify optionality, we (recursively) consult the optionality of the type you're mapping over to see if it strips or adds optionality.
There was a problem hiding this comment.
Should this be an enum? Then it'd be easier to tell what the numbers mean.
There was a problem hiding this comment.
It could be an enum, but number feels more appropriate since we use the greater and less than operators to relate the combined values.
There was a problem hiding this comment.
Would a comment about what each number represents work?
Fixes #57487.