Unwrap NoInfer types when narrowing
#58292
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Andarist
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Apr 23, 2024
src/compiler/checker.ts
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| declaredType = isNoInferType(declaredType) ? (declaredType as SubstitutionType).baseType : declaredType; | ||
| initialType = isNoInferType(initialType) ? (initialType as SubstitutionType).baseType : initialType; |
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My first instinct was that I should re-wrap the result of narrowing with NoInfer but quoting the original NoInfer PR:
Other than blocking inference, NoInfer markers have no effect on T. Indeed, T and NoInfer are considered identical types in all other contexts.
So I don't see a reason why that would be necessary. I also tested something like this (TS playground) to see if this would be needed and I don't think it is:
declare function inner<T>(arg: T): T;
declare function outer<T>(a: T, cb: (arg: NoInfer<T>) => void): void;
outer({ foo: "bar" }, (arg) => {
arg
// ^? (parameter) arg: NoInfer<{ foo: string; }>
const result = inner(arg); // inferred despite `arg` being a `NoInfer` type!
// ^? const result: NoInfer<{ foo: string; }>
});
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I agree it's fine to erase NoInfer in variable, parameter, and property references, but I think it would be simpler and more consistent to do it first thing in the getNarrowableTypeForReference function. I think that's all you'd need.
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moved it to getNarrowableTypeForReference, works like a charm - thanks!
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May 28, 2024
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@sandersn @RyanCavanaugh could this one land before the upcoming RC? |
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* upstream/main: (37 commits) Added NoTruncation flag to completions (microsoft#58719) Clone node to remove location even when it has been modified if needed (microsoft#58706) Properly account for `this` argument in intersection apparent type caching (microsoft#58677) Fix: Include Values of Script Extensions for Unicode Property Value Expressions in Regular Expressions (microsoft#58615) In `reScanSlashToken` use `charCodeChecked` not `codePointChecked` (microsoft#58727) Shorten error spans for errors reported on constructor declarations (microsoft#58061) Mark file as skips typechecking if it contains ts-nocheck (microsoft#58593) Fixed an issue with broken `await using` declarations in `for of` loops (microsoft#56466) Do not expand type references in keyof and index access (microsoft#58715) Improve the performance of isolatedDeclarations quickfix (microsoft#58722) Unwrap `NoInfer` types when narrowing (microsoft#58292) Recover from type reuse errors by falling back to inferred type printing (microsoft#58720) Fixing self import (microsoft#58718) Enable JS emit for noCheck and noCheck for transpileModule (microsoft#58364) Revert PR 55371 (microsoft#58702) Update dependencies (microsoft#58639) Fix baselines after PR 58621 (microsoft#58705) Do not infer `yield*` type from contextual `TReturn` (microsoft#58621) `await using` normative changes (microsoft#58624) Handling statements from a known source file (microsoft#58679) ...
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fixes #58266