TypeScript 4.0: Support labeled tuple elements #11754
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nicolo-ribaudo
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PR: New Feature 🚀
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| @@ -76,6 +76,8 @@ const TSErrors = Object.freeze({ | |||
| IndexSignatureHasStatic: "Index signatures cannot have the 'static' modifier", | |||
| OptionalTypeBeforeRequired: | |||
| "A required element cannot follow an optional element.", | |||
| LabeledElementBeforeUnlabeled: | |||
| "An unlabeled element cannot follow a labeled element.", | |||
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TypeScript throws Tuple members must all have names or all not have names. However, it accepts this code:
type B = [A, x: C];
@weswigham / @DanielRosenwasser Which is the correct behavior?
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Uhh.. we shouldn't accept that (but it is just a grammar error, not a parse error). Care to open an issue?
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Oh I completely missed rest labeled elements. |
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Should the AST be a |
extend interface TSRestType {
typeAnnotation: TSType | TSNamedTupleMember;
}looks good to me, and it is consistent with how we model |
packages/babel-parser/src/types.js
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| elementTypes: $ReadOnlyArray<TsType | TsTupleElementType>, | ||
| }; | ||
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| export type TsNamedTupleMember = TsTypeBase & { |
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Since it is a new node type, we should also add support on @babel/generator.
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| const isLabeled = type === "TSNamedTupleMember"; | ||
| // Flow doesn't support ??= | ||
| labeledElements = labeledElements ?? isLabeled; |
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| labeledElements = labeledElements ?? isLabeled; | |
| labeledElements ?? (labeledElements = isLabeled); |
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Even if it's one operation more, I find the = ... ?? more readable
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😂 But that's not the intended semantics of ||=. They are just nitpicks, feel free to ignore them if current code looks good to you.
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In this case, without with or MemberExpression, it has exactly the same behavior 😛
| seenOptionalElement = | ||
| seenOptionalElement || | ||
| (type === "TSNamedTupleMember" && elementNode.optional) || | ||
| type === "TSOptionalType"; |
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| seenOptionalElement = | |
| seenOptionalElement || | |
| (type === "TSNamedTupleMember" && elementNode.optional) || | |
| type === "TSOptionalType"; | |
| seenOptionalElement || | |
| (seenOptionalElement = | |
| (type === "TSNamedTupleMember" && elementNode.optional) || | |
| type === "TSOptionalType"); |
existentialism
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PR: Ready to be Merged
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@existentialism I think this can be merged because it targets to |
JLHwung
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PR: Ready to be Merged
* TypeScript 4.0: Support labeled tuple elements * More tests * Disallow mixing labeled and unlabeled elements * Update AST shape * Enable test after rebase * Allow labeled spread types * Fix flow * Add types and generator suport * Update packages/babel-parser/src/plugins/typescript/index.js * Prettier
* TypeScript 4.0: Support labeled tuple elements * More tests * Disallow mixing labeled and unlabeled elements * Update AST shape * Enable test after rebase * Allow labeled spread types * Fix flow * Add types and generator suport * Update packages/babel-parser/src/plugins/typescript/index.js * Prettier
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https://devblogs.microsoft.com/typescript/announcing-typescript-4-0-beta/#labeled-tuple-elements