TS7031 on a contextually typed parameter with a destructured = {} default #16

tsc-rs 0.1.0 reports TS7031 for a destructured parameter with a = {} default, even when the function is contextually typed and the binding element has a real type.

Repro

// tsconfig: { "compilerOptions": { "strict": true, "noEmit": true } }
type Mk = (options?: { recursive?: boolean }) => void

export const mk: Mk = ({ recursive } = {}) => {
  const proof: string = recursive
  void proof
}

a.ts(3,26): error TS7031: Binding element 'recursive' implicitly has an 'any' type.
a.ts(4,9): error TS2322: Type 'boolean | undefined' is not assignable to type 'string'.

The two errors contradict each other: the second one shows that recursive is boolean | undefined.

The same happens for a callback argument and for a method of an object literal typed by an interface:

declare function take(cb: (options?: { deep?: boolean }) => void): void
take(({ deep } = {}) => void deep) // TS7031

interface Driver { rm(path: string, options?: { force?: boolean }): void }
export const driver: Driver = { rm: (path, { force } = {}) => void [path, force] } // TS7031

An annotated parameter is fine (({ a }: { a?: number } = {})), and a parameter with no type anywhere (function f({ a } = {}) {}) should keep its error.

Where it comes from

This is upstream behaviour that the port copies. typescript@6.0.3, typescript@7.0.2 and typescript@7.1.0-dev.20260922.1 accept the code. typescript@7.1.0-dev.20260923.1 and later report TS7031. The change is microsoft/TypeScript#64043 ("Align object binding defaults with arrays"): padObjectLiteralType now pads every binding element missing from the default and calls getTypeFromBindingElement with reportErrors set, without looking at the contextual type of the parameter.

In the port that is pad_object_literal_type in crates/ts_goport/src/checker/checker_p19.rs.

Effect on a real project

On our monorepo (17 projects, Effect 4) tsc-rs and tsc 7.0.2 with @effect/tsgo give the same 1,677 diagnostics, and these are the only 3 lines that differ. They come from an object that implements an SDK interface:

mkdir: (path, { recursive } = {}) => ...
rm: (path, { recursive, force } = {}) => ...

I understand the port follows Go on purpose. I am opening this so the difference from 7.0.x is on record, and I have a small fix in a pull request in case you want it before upstream changes.