Fixed an issue with mapped property symbol not displaying added | undefined when its origin symbol was optional - #64100
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…defined` when its origin symbol was optional
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Mateusz Burzyński (Andarist)
August 30, 2026 17:24
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Pull request overview
Fixes mapped-property quick info so explicit undefined remains visible after optionality transformations.
Changes:
- Updates implicit-
undefineddetection for mapped properties. - Adds six fourslash regression tests covering optional, required, nested, and exact-optional cases.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
tsc/internal/checker/emitresolver.go |
Updates mapped-property serialization logic. |
tsc/internal/fourslash/tests/quickInfoMappedTypeOptionalPropertyExplicitUndefined_test.go |
Tests explicit undefined preservation. |
tsc/internal/fourslash/tests/quickInfoMappedPropertyUnionUndefined1_test.go |
Tests exact optional properties. |
tsc/internal/fourslash/tests/quickInfoMappedPropertyUnionUndefined2_test.go |
Tests default optional semantics. |
tsc/internal/fourslash/tests/quickInfoMappedPropertyUnionUndefined3_test.go |
Tests nested mapped transformations. |
tsc/internal/fourslash/tests/quickInfoMappedPropertyUnionUndefined4_test.go |
Tests required-to-undefined mapping. |
tsc/internal/fourslash/tests/quickInfoMappedPropertyUnionUndefined5_test.go |
Covers issue #62325. |
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Mateusz Burzyński (Andarist)
marked this pull request as draft
August 30, 2026 19:22
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recreates #59957
fixes #59948
fixes #60411
fixes #62325