=== tests/cases/conformance/pedantic/noUncheckedIndexedAccess.ts ===
type CheckBooleanOnly<T extends boolean> = any;
>CheckBooleanOnly : any

// Validate CheckBooleanOnly works - should error
type T_ERR1 = CheckBooleanOnly<boolean | undefined>;
>T_ERR1 : any

enum NumericEnum1 { A, B, C }
>NumericEnum1 : NumericEnum1
>A : NumericEnum1.A
>B : NumericEnum1.B
>C : NumericEnum1.C

enum NumericEnum2 { A = 0, B = 1 , C = 2 }
>NumericEnum2 : NumericEnum2
>A : NumericEnum2.A
>0 : 0
>B : NumericEnum2.B
>1 : 1
>C : NumericEnum2.C
>2 : 2

enum StringEnum1 { A = "Alpha", B = "Beta" }
>StringEnum1 : StringEnum1
>A : StringEnum1.A
>"Alpha" : "Alpha"
>B : StringEnum1.B
>"Beta" : "Beta"

declare const strMap: { [s: string]: boolean };
>strMap : { [s: string]: boolean; }
>s : string

// All of these should be errors
const e1: boolean = strMap["foo"];
>e1 : boolean
>strMap["foo"] : boolean | undefined
>strMap : { [s: string]: boolean; }
>"foo" : "foo"

const e2: boolean = strMap.bar;
>e2 : boolean
>strMap.bar : boolean | undefined
>strMap : { [s: string]: boolean; }
>bar : boolean | undefined

const e3: boolean = strMap[0];
>e3 : boolean
>strMap[0] : boolean | undefined
>strMap : { [s: string]: boolean; }
>0 : 0

const e4: boolean = strMap[0 as string | number];
>e4 : boolean
>strMap[0 as string | number] : boolean | undefined
>strMap : { [s: string]: boolean; }
>0 as string | number : string | number
>0 : 0

const e5: boolean = strMap[0 as string | 0 | 1];
>e5 : boolean
>strMap[0 as string | 0 | 1] : boolean | undefined
>strMap : { [s: string]: boolean; }
>0 as string | 0 | 1 : string | 0 | 1
>0 : 0

const e6: boolean = strMap[0 as 0 | 1];
>e6 : boolean
>strMap[0 as 0 | 1] : boolean | undefined
>strMap : { [s: string]: boolean; }
>0 as 0 | 1 : 0 | 1
>0 : 0

const e7: boolean = strMap["foo" as "foo" | "baz"];
>e7 : boolean
>strMap["foo" as "foo" | "baz"] : boolean | undefined
>strMap : { [s: string]: boolean; }
>"foo" as "foo" | "baz" : "foo" | "baz"
>"foo" : "foo"

const e8: boolean = strMap[NumericEnum1.A];
>e8 : boolean
>strMap[NumericEnum1.A] : boolean | undefined
>strMap : { [s: string]: boolean; }
>NumericEnum1.A : NumericEnum1.A
>NumericEnum1 : typeof NumericEnum1
>A : NumericEnum1.A

const e9: boolean = strMap[NumericEnum2.A];
>e9 : boolean
>strMap[NumericEnum2.A] : boolean | undefined
>strMap : { [s: string]: boolean; }
>NumericEnum2.A : NumericEnum2.A
>NumericEnum2 : typeof NumericEnum2
>A : NumericEnum2.A

const e10: boolean = strMap[StringEnum1.A];
>e10 : boolean
>strMap[StringEnum1.A] : boolean | undefined
>strMap : { [s: string]: boolean; }
>StringEnum1.A : StringEnum1.A
>StringEnum1 : typeof StringEnum1
>A : StringEnum1.A

const e11: boolean = strMap[StringEnum1.A as StringEnum1];
>e11 : boolean
>strMap[StringEnum1.A as StringEnum1] : boolean | undefined
>strMap : { [s: string]: boolean; }
>StringEnum1.A as StringEnum1 : StringEnum1
>StringEnum1.A : StringEnum1.A
>StringEnum1 : typeof StringEnum1
>A : StringEnum1.A

const e12: boolean = strMap[NumericEnum1.A as NumericEnum1];
>e12 : boolean
>strMap[NumericEnum1.A as NumericEnum1] : boolean | undefined
>strMap : { [s: string]: boolean; }
>NumericEnum1.A as NumericEnum1 : NumericEnum1
>NumericEnum1.A : NumericEnum1.A
>NumericEnum1 : typeof NumericEnum1
>A : NumericEnum1.A

const e13: boolean = strMap[NumericEnum2.A as NumericEnum2];
>e13 : boolean
>strMap[NumericEnum2.A as NumericEnum2] : boolean | undefined
>strMap : { [s: string]: boolean; }
>NumericEnum2.A as NumericEnum2 : NumericEnum2
>NumericEnum2.A : NumericEnum2.A
>NumericEnum2 : typeof NumericEnum2
>A : NumericEnum2.A

const e14: boolean = strMap[null as any];
>e14 : boolean
>strMap[null as any] : boolean | undefined
>strMap : { [s: string]: boolean; }
>null as any : any
>null : null

// Should be OK
const ok1: boolean | undefined = strMap["foo"];
>ok1 : boolean | undefined
>strMap["foo"] : boolean | undefined
>strMap : { [s: string]: boolean; }
>"foo" : "foo"

const ok2: boolean | undefined = strMap.bar;
>ok2 : boolean | undefined
>strMap.bar : boolean | undefined
>strMap : { [s: string]: boolean; }
>bar : boolean | undefined

type T_OK1 = CheckBooleanOnly<(typeof strMap)[string]>;
>T_OK1 : any
>strMap : { [s: string]: boolean; }

type T_OK2 = CheckBooleanOnly<(typeof strMap)["foo"]>;
>T_OK2 : any
>strMap : { [s: string]: boolean; }

type T_OK3 = CheckBooleanOnly<(typeof strMap)["bar" | "baz"]>;
>T_OK3 : any
>strMap : { [s: string]: boolean; }

type T_OK4 = CheckBooleanOnly<(typeof strMap)[number]>;
>T_OK4 : any
>strMap : { [s: string]: boolean; }

type T_OK5 = CheckBooleanOnly<(typeof strMap)[any]>;
>T_OK5 : any
>strMap : { [s: string]: boolean; }

// Writes don't allow 'undefined'; all should be errors
strMap["baz"] = undefined;
>strMap["baz"] = undefined : undefined
>strMap["baz"] : boolean
>strMap : { [s: string]: boolean; }
>"baz" : "baz"
>undefined : undefined

strMap.qua = undefined;
>strMap.qua = undefined : undefined
>strMap.qua : boolean
>strMap : { [s: string]: boolean; }
>qua : boolean
>undefined : undefined

strMap[0] = undefined;
>strMap[0] = undefined : undefined
>strMap[0] : boolean
>strMap : { [s: string]: boolean; }
>0 : 0
>undefined : undefined

strMap[null as any] = undefined;
>strMap[null as any] = undefined : undefined
>strMap[null as any] : boolean
>strMap : { [s: string]: boolean; }
>null as any : any
>null : null
>undefined : undefined

// Numeric lookups are unaffected
declare const numMap: { [s: number]: boolean };
>numMap : { [s: number]: boolean; }
>s : number

// All of these should be ok
const num_ok1: boolean = numMap[0];
>num_ok1 : boolean
>numMap[0] : boolean | undefined
>numMap : { [s: number]: boolean; }
>0 : 0

const num_ok2: boolean = numMap[0 as number];
>num_ok2 : boolean
>numMap[0 as number] : boolean | undefined
>numMap : { [s: number]: boolean; }
>0 as number : number
>0 : 0

const num_ok3: boolean = numMap[0 as 0 | 1];
>num_ok3 : boolean
>numMap[0 as 0 | 1] : boolean | undefined
>numMap : { [s: number]: boolean; }
>0 as 0 | 1 : 0 | 1
>0 : 0

const num_ok4: boolean = numMap[NumericEnum1.A];
>num_ok4 : boolean
>numMap[NumericEnum1.A] : boolean | undefined
>numMap : { [s: number]: boolean; }
>NumericEnum1.A : NumericEnum1.A
>NumericEnum1 : typeof NumericEnum1
>A : NumericEnum1.A

const num_ok5: boolean = numMap[NumericEnum2.A];
>num_ok5 : boolean
>numMap[NumericEnum2.A] : boolean | undefined
>numMap : { [s: number]: boolean; }
>NumericEnum2.A : NumericEnum2.A
>NumericEnum2 : typeof NumericEnum2
>A : NumericEnum2.A

// Generics
function generic1<T extends { [s: string]: boolean }>(arg: T): boolean {
>generic1 : <T extends { [s: string]: boolean; }>(arg: T) => boolean
>s : string
>arg : T

    // Should error
    return arg["blah"];
>arg["blah"] : boolean | undefined
>arg : T
>"blah" : "blah"
}
function generic2<T extends { [s: string]: boolean }>(arg: T): boolean {
>generic2 : <T extends { [s: string]: boolean; }>(arg: T) => boolean
>s : string
>arg : T

    // Should OK
    return arg["blah"]!;
>arg["blah"]! : boolean
>arg["blah"] : boolean | undefined
>arg : T
>"blah" : "blah"
}
function generic3<T extends string>(arg: T): boolean {
>generic3 : <T extends string>(arg: T) => boolean
>arg : T

    // Should error
    return strMap[arg];
>strMap[arg] : boolean | undefined
>strMap : { [s: string]: boolean; }
>arg : T
}

// Element access into known properties is ok
declare const obj1: { x: string, y: number, [key: string]: string | number };
>obj1 : { [key: string]: string | number; x: string; y: number; }
>x : string
>y : number
>key : string

obj1["x"];
>obj1["x"] : string
>obj1 : { [key: string]: string | number; x: string; y: number; }
>"x" : "x"

const y = "y";
>y : "y"
>"y" : "y"

obj1[y];
>obj1[y] : number
>obj1 : { [key: string]: string | number; x: string; y: number; }
>y : "y"

let yy = "y";
>yy : string
>"y" : "y"

obj1[yy];
>obj1[yy] : string | number | undefined
>obj1 : { [key: string]: string | number; x: string; y: number; }
>yy : string

let z = "z";
>z : string
>"z" : "z"

obj1[z];
>obj1[z] : string | number | undefined
>obj1 : { [key: string]: string | number; x: string; y: number; }
>z : string

// Distributivity cases
declare const strMapUnion: { [s: string]: boolean } | { [s: string]: number };
>strMapUnion : { [s: string]: boolean; } | { [s: string]: number; }
>s : string
>s : string

// Should error
const f1: boolean | number = strMapUnion["foo"];
>f1 : number | boolean
>strMapUnion["foo"] : number | boolean | undefined
>strMapUnion : { [s: string]: boolean; } | { [s: string]: number; }
>"foo" : "foo"

// Symbol index signatures
declare const s: unique symbol;
>s : unique symbol

declare const symbolMap: { [s]: string };
>symbolMap : { [s]: string; }
>[s] : string
>s : unique symbol

const e15: string = symbolMap[s]; // Should OK
>e15 : string
>symbolMap[s] : string
>symbolMap : { [s]: string; }
>s : unique symbol

symbolMap[s] = undefined; // Should error
>symbolMap[s] = undefined : undefined
>symbolMap[s] : string
>symbolMap : { [s]: string; }
>s : unique symbol
>undefined : undefined

// Variadic tuples
declare const nonEmptyStringArray: [string, ...string[]];
>nonEmptyStringArray : [string, ...string[]]

const variadicOk1: string = nonEmptyStringArray[0];  // Should OK
>variadicOk1 : string
>nonEmptyStringArray[0] : string
>nonEmptyStringArray : [string, ...string[]]
>0 : 0

const variadicError1: string = nonEmptyStringArray[1]; // Should error
>variadicError1 : string
>nonEmptyStringArray[1] : string | undefined
>nonEmptyStringArray : [string, ...string[]]
>1 : 1

// Generic index type
declare const myRecord1: { a: string; b: string };
>myRecord1 : { a: string; b: string; }
>a : string
>b : string

declare const myRecord2: { a: string; b: string, [key: string]: string };
>myRecord2 : { [key: string]: string; a: string; b: string; }
>a : string
>b : string
>key : string

const fn1 = <Key extends keyof typeof myRecord1>(key: Key): string => myRecord1[key]; // Should OK
>fn1 : <Key extends "a" | "b">(key: Key) => string
><Key extends keyof typeof myRecord1>(key: Key): string => myRecord1[key] : <Key extends "a" | "b">(key: Key) => string
>myRecord1 : { a: string; b: string; }
>key : Key
>myRecord1[key] : { a: string; b: string; }[Key]
>myRecord1 : { a: string; b: string; }
>key : Key

const fn2 = <Key extends keyof typeof myRecord1>(key: Key): string => myRecord2[key]; // Should OK
>fn2 : <Key extends "a" | "b">(key: Key) => string
><Key extends keyof typeof myRecord1>(key: Key): string => myRecord2[key] : <Key extends "a" | "b">(key: Key) => string
>myRecord1 : { a: string; b: string; }
>key : Key
>myRecord2[key] : { [key: string]: string; a: string; b: string; }[Key]
>myRecord2 : { [key: string]: string; a: string; b: string; }
>key : Key

const fn3 = <Key extends keyof typeof myRecord2>(key: Key) => {
>fn3 : <Key extends string | number>(key: Key) => void
><Key extends keyof typeof myRecord2>(key: Key) => {    myRecord2[key] = undefined; // Should error    const v: string = myRecord2[key]; // Should error} : <Key extends string | number>(key: Key) => void
>myRecord2 : { [key: string]: string; a: string; b: string; }
>key : Key

    myRecord2[key] = undefined; // Should error
>myRecord2[key] = undefined : undefined
>myRecord2[key] : { [key: string]: string; a: string; b: string; }[Key]
>myRecord2 : { [key: string]: string; a: string; b: string; }
>key : Key
>undefined : undefined

    const v: string = myRecord2[key]; // Should error
>v : string
>myRecord2[key] : string | undefined
>myRecord2 : { [key: string]: string; a: string; b: string; }
>key : Key

};