Open
Description
openedon Jul 31, 2023
Bug Report
🔎 Search Terms
"No error for last overload signature" yields stale issue 35186, and a couple of more recent issues that got resolved: 48636, 37974. (The stale 35186 appears to be a different issue as it also occurs in versions before v5.0.4.)
🕗 Version & Regression Information
- This is a crash
- This changed between versions 4.9.5 and 5.0.4, and still occurs up to typescript@next.
⏯ Playground Link
Bug-workbench link with relevant code
💻 Code
// @filename: types.ts
export type ProductName = 'a' | 'b'
export type SubproductNameForProductName<P extends ProductName> = P extends unknown
? keyof EntitiesByProductName[P]
: never
type EntitiesByProductName = {
a: { a1: { value: 'a-a1' } }
b: { b1: { value: 'b-b1' } }
}
export type DiscriminatedUnion<
P extends ProductName = ProductName,
E extends SubproductNameForProductName<P> = SubproductNameForProductName<P>,
> = P extends ProductName
? E extends SubproductNameForProductName<P>
// ? E extends unknown // With unknown, the exception doesn't happen.
? EntitiesByProductName[P][E]
: never
: never
// @filename: app.ts
import { SubproductNameForProductName, DiscriminatedUnion, ProductName } from './types'
export const bug = <P extends ProductName>() => {
const subproducts: DiscriminatedUnion<P, SubproductNameForProductName<P>>[] = []
subproducts.map((_: DiscriminatedUnion) => null)
}🙁 Actual behavior
The compiler throws an exception:
/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:114747
throw e;
^
Error: Debug Failure. No error for last overload signature
at resolveCall (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:70223:19)
at resolveCallExpression (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:70605:12)
at resolveSignature (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:70988:16)
at getResolvedSignature (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:71008:18)
at checkCallExpression (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:71120:23)
at checkExpressionWorker (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:74278:16)
at checkExpression (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:74189:32)
at maybeCheckExpression (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:73280:28)
at BinaryExpressionStateMachine.onLeft (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:73216:16)
at Array.left (/Users/martijn/git/Insify/insify-core/node_modules/typescript/lib/tsc.js:25140:30)
🙂 Expected behavior
No compiler exception.
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