Completions bug

[orta]

function returnFoo<T extends {a: 1, b: 2}>(foo: T): T {
    return foo;
}

// ✅ auto-completion works
returnFoo({  })
//          ^|
// ❌ auto-completion broken
returnFoo({  } as const)
//          ^|

[orta]

I think this error validation, and the exception being raised should probably not happen in this mode.

[typescript-bot]

It looks like something has changed with this repro on today's nightly build of TypeScript. You can see what has changed on TypeScript between 473113 and 9a5c02 here.

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Issue body code block by @orta

Before	After
❌ Failed: - Property 'tag' does not exist on type 'never'.	👍 Compiled

[typescript-bot]

👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of the repro in the issue body running against the nightly TypeScript.

---

Issue body code block by @orta

❌ Failed: -

• Argument of type '{}' is not assignable to parameter of type '{ a: 1; b: 2; }'. Type '{}' is missing the following properties from type '{ a: 1; b: 2; }': a, b
• Argument of type '{}' is not assignable to parameter of type '{ a: 1; b: 2; }'. Type '{}' is missing the following properties from type '{ a: 1; b: 2; }': a, b

Historical Information

Version	Reproduction Outputs
4.2.2, 4.3.2, 4.4.2, 4.5.2, 4.6.2	❌ Failed: - Argument of type '{}' is not assignable to parameter of type '{ a: 1; b: 2; }'. Type '{}' is missing the following properties from type '{ a: 1; b: 2; }': a, b Argument of type '{}' is not assignable to parameter of type '{ a: 1; b: 2; }'. Type '{}' is missing the following properties from type '{ a: 1; b: 2; }': a, b