Document assignment to aliasSymbol in getUnionTypeFromSortedList #17434
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Aug 29, 2017
src/compiler/checker.ts
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| @@ -7359,6 +7359,11 @@ namespace ts { | |||
| type = <UnionType>createType(TypeFlags.Union | propagatedFlags); | |||
| unionTypes.set(id, type); | |||
| type.types = types; | |||
| /* | |||
| Note: This is the alias symbol (or lack thereof) that we see when we first encounter this union type. | |||
| If there exist both `type T = number | boolean` and `type U = number | boolean`, it is arbitrary which one gets the aliasSymbol. | |||
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I would write this line as
For aliases of identical unions, eg
type T = A | B; type U = A | B, the symbol of the first alias encountered is thealiasSymbol.
This is technically true even for the language server, but "first alias encountered" depends on the order of actions by the user.
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Replaces #17349