Fixed an issue with optionality not being stripped from generic mapped types on indexed access #59921
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…d types on indexed access
typescript-bot
added
the
For Milestone Bug
Andarist
commented
Sep 10, 2024
| @@ -19103,9 +19103,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]); | |||
| const templateMapper = combineTypeMappers(objectType.mapper, mapper); | |||
| const instantiatedTemplateType = instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper); | |||
| const isOptional = getMappedTypeOptionality(objectType) > 0 || (isGenericType(objectType) ? | |||
There was a problem hiding this comment.
In the given repro the immediate modifiers type has -? for which getMappedTypeOptionality returns -1. So the first condition was not satisfied and the compiler proceeded to compute getCombinedMappedTypeOptionality. This time it was called with the modifiers type and not the original object type. Since that was a mapped type too it got its modifiers type etc.
Essentially this was skipping the outermost mapped type modifiers in this scenario - the ones that were supposed strip the optionality.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
fixes #59902