Support for infer in template literals, intrinsic types and more
#2053
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Useful for extends types within conditional nodes
Added support for never types and template literal types for extends types
Useful for extends types within conditional nodes
Added support for returning intrinsic types for extends clauses. Also added support for Capitalize<string> expressions
…o isAssignableTo unit tests
… of conditional types
…onditionals with mapped type This type is the original type from our code which brought me onto this journey of adding support for more advanced inference in the first place. Thought it was good to have it here for reference in the future.
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@arthurfiorette could you take a look at this? |
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Closes #1355
Adding full type inference for template literals were quite a lot more work than first anticipated, particularly because
TemplateLiteralNodeParserwould narrow the type to aLiteralType,StringTypeorUnionTypebefore sent toisAssignableToinConditionalNodeParser. My proposed solution is to add a check withinTemplateLiteralNodeParserto see if the node exists within an extends clause of a conditional, in which case we create a newTemplateLiteralTypewhere we retain the original information stored in the template literal, which allows us to segment through the parts and verify if the source is assignable.Additionally, I've done the same for
IntrinsicNodeParser, which had the same limitations, where bothStringTypeandInferTypeas an argument in a condiitonal type would fail.I've added extensive test cases for both.