Switch on typeof does not narrow unknown correctly.

[jack-williams]

TypeScript Version: master 83fe1ea

Search Terms: switch typeof unknown

Code

// @strictNullChecks: true
function unknownNarrowing(x: unknown) {
    switch (typeof x) {
        case 'function': x; return; // x is unknown, should be Function
        case 'object': x; return; // x is unknown, should be object | null
    }
}

Expected behavior:

• Narrowing unknown in switch at clause "function" should result in type Function.
• Narrowing unknown in switch at clause "object" should result in type object | null.

Actual behavior:

• Value of type unknown does not narrow.

Playground Link: N/A (Playground not on this version).