Code

// @noEmit: true
// @allowJs: true
// @checkJs: true
// @strict: true
// @Filename: a.js

/** @param {number} [p] */
function f(p) {
    p = undefined
    p = null
}

Expected behavior:

The type of p should be number | null | undefined, and should be optional in the signature of f.

Actual behavior:

p is optional but doesn't include null | undefined in its type.