Excessively deep type instantiation | TypeScript Community | Page 1

frozen forgeBOT Apr 9, 2024, 12:06 PM

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balam314#0

Playground Link

Preview:ts ... export type VariableTypeMapping<T> = T extends "INTEGER" ? number : T extends "DATE" ? Date : T extends RecordVariableType ? Record<string, VariableTypeMapping<any>> //ERROR: excessively deep : T extends ArrayVariableType ? Array<Va ...

lucid knoll Apr 9, 2024, 12:09 PM

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VariableTypeMapping returns the type of the JS value used to store the value of a variable of type T in a programming language runtime

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in this programming language, T can be an arbitrarily deep record, with arrays and other stuff mixed in

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I'm trying to get the correct typing but end up breaking TS instead

lucid knoll Apr 10, 2024, 4:37 AM

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!helper

tepid scroll Apr 10, 2024, 4:38 AM

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use the lazy evaluation trick or whatever there was the docs

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gimme sec

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i cant find it but the basic idea is adding something like

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T extends infer U ? U : never

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so it stops recursion there

dire spoke Apr 10, 2024, 8:22 AM

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https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-5.html#tail-recursion-elimination-on-conditional-types

Documentation - TypeScript 4.5

TypeScript 4.5 Release Notes

timber grove Apr 10, 2024, 1:02 PM

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you can also avoid the problem by writing out the index signature rather than using Record:

frozen forgeBOT Apr 10, 2024, 1:02 PM

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mkantor#0

Playground Link

Preview:ts ... te : T extends RecordVariableType ? {[key: string]: VariableTypeMapping<any>} : T extends ArrayVariabl ...

lucid knoll Apr 10, 2024, 2:03 PM

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timber grove you can also avoid the problem by writing out the index signature rather than us...

ah nice

#Excessively deep type instantiation