=== tests/cases/compiler/deleteExpressionMustBeOptional.ts ===
interface Foo {
    a: number
>a : number

    b: number | undefined
>b : number | undefined

    c: number | null
>c : number | null
>null : null

    d?: number
>d : number | undefined

    e: number | undefined | null
>e : number | null | undefined
>null : null

    f?: number | undefined | null
>f : number | null | undefined
>null : null

    g: unknown
>g : unknown

    h: any
>h : any

    i: never
>i : never
}

interface AA {
    [s: string]: number
>s : string
}

type BB = {
>BB : BB

    [P in keyof any]: number
}

declare const f: Foo
>f : Foo

declare const a: AA
>a : AA

declare const b: BB
>b : BB

delete f.a
>delete f.a : boolean
>f.a : number
>f : Foo
>a : number

delete f.b
>delete f.b : boolean
>f.b : number | undefined
>f : Foo
>b : number | undefined

delete f.c
>delete f.c : boolean
>f.c : number | null
>f : Foo
>c : number | null

delete f.d
>delete f.d : boolean
>f.d : number | undefined
>f : Foo
>d : number | undefined

delete f.e
>delete f.e : boolean
>f.e : number | null | undefined
>f : Foo
>e : number | null | undefined

delete f.f
>delete f.f : boolean
>f.f : number | null | undefined
>f : Foo
>f : number | null | undefined

delete f.g
>delete f.g : boolean
>f.g : unknown
>f : Foo
>g : unknown

delete f.h
>delete f.h : boolean
>f.h : any
>f : Foo
>h : any

delete f.i
>delete f.i : boolean
>f.i : never
>f : Foo
>i : never

delete f.j
>delete f.j : boolean
>f.j : any
>f : Foo
>j : any

delete a.a
>delete a.a : boolean
>a.a : number
>a : AA
>a : number

delete a.b
>delete a.b : boolean
>a.b : number
>a : AA
>b : number

delete b.a
>delete b.a : boolean
>b.a : number
>b : BB
>a : number

delete b.b
>delete b.b : boolean
>b.b : number
>b : BB
>b : number