Debug Failure. Parameter symbol already has a cached type which differs from newly assigned type.

[denis-sokolov]

Bug Report

🔎 Search Terms

Error: Debug Failure. Expected [object Object] === [object Object]. Parameter symbol already has a cached type which differs from newly assigned type

🕗 Version & Regression Information

• This is a crash
• This changed between versions 4.6.4 and 4.7.2
• This is still happening with the currently latest 4.8.0-dev.20220603

⏯ Playground Link

Does not reproduce in the playground, only reproduces in CLI. To reproduce, run tsc code.ts with the code below.

💻 Code

function wrap<Args extends unknown[]>(_: (...args: Args) => void) {}
wrap(({ cancelable } = {}) => {});

🙁 Actual behavior

Error: Debug Failure. Expected [object Object] === [object Object]. Parameter symbol already has a cached type which differs from newly assigned type
    at assignParameterType (node_modules/typescript/lib/tsc.js:64861:26)
    at assignContextualParameterTypes (node_modules/typescript/lib/tsc.js:64826:21)
    at contextuallyCheckFunctionExpressionOrObjectLiteralMethod (node_modules/typescript/lib/tsc.js:65228:29)
    at checkFunctionExpressionOrObjectLiteralMethod (node_modules/typescript/lib/tsc.js:65207:13)
    at checkExpressionWorker (node_modules/typescript/lib/tsc.js:66804:28)
    at checkExpression (node_modules/typescript/lib/tsc.js:66706:38)
    at checkExpressionWithContextualType (node_modules/typescript/lib/tsc.js:66395:28)
    at inferTypeArguments (node_modules/typescript/lib/tsc.js:62905:39)
    at chooseOverload (node_modules/typescript/lib/tsc.js:63565:53)
    at resolveCall (node_modules/typescript/lib/tsc.js:63402:26)

🙂 Expected behavior

No crash.

(Ideally an error about an implicit any)

[jkillian]

For anyone else who runs in to this, you can work around the crash for now by adding an explicit type to the function argument. Given the example above, this will fix the crash:

function wrap<Args extends unknown[]>(_: (...args: Args) => void) {}
wrap(({ cancelable }: { cancelable?: boolean } = {}) => {});

[jakebailey]

Unfortunately this bisected to #43845, which introduced the debug message, so that's no indication other than that this has to do with parameter fixing (a la #43835).

This same error had been showing up a lot in fuzzer runs; I think @weswigham said to ping if this sort of thing continued?

[weswigham]

Right. Anywhere this asset fires is somewhere we're erroneously trying to fix a parameter multiple times and need to, well, not (sometimes that can mean ignoring the second fix, or sometimes that can mean combining the secondary and primary results into the first fix).

[albertodvc]

I'm still having this issue with v4.8.3.