tests/cases/compiler/strictOptionalProperties1.ts(6,5): error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
tests/cases/compiler/strictOptionalProperties1.ts(12,5): error TS2412: Type 'string | undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
  Type 'undefined' is not assignable to type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(20,9): error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
tests/cases/compiler/strictOptionalProperties1.ts(28,9): error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
tests/cases/compiler/strictOptionalProperties1.ts(53,5): error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
tests/cases/compiler/strictOptionalProperties1.ts(60,5): error TS2322: Type 'undefined' is not assignable to type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(64,5): error TS2322: Type '[number, string?, string?]' is not assignable to type '[number, string?]'.
  Target allows only 2 element(s) but source may have more.
tests/cases/compiler/strictOptionalProperties1.ts(73,5): error TS2322: Type '[number, never?, never?, never?]' is not assignable to type '[number, string?, boolean?]'.
  Target allows only 3 element(s) but source may have more.
tests/cases/compiler/strictOptionalProperties1.ts(74,5): error TS2322: Type '[never?, never?, true?]' is not assignable to type '[number, string?, boolean?]'.
  Source provides no match for required element at position 0 in target.
tests/cases/compiler/strictOptionalProperties1.ts(75,5): error TS2322: Type '[number, undefined, true]' is not assignable to type '[number, string?, boolean?]'.
  Type at position 1 in source is not compatible with type at position 1 in target.
    Type 'undefined' is not assignable to type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(99,7): error TS2375: Type '{ foo: undefined; bar: string; }' is not assignable to type 'InputProps' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
  Types of property 'foo' are incompatible.
    Type 'undefined' is not assignable to type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(105,7): error TS2322: Type '[number, undefined]' is not assignable to type '[number, string?, boolean?]'.
  Type at position 1 in source is not compatible with type at position 1 in target.
    Type 'undefined' is not assignable to type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(106,7): error TS2322: Type '[number, string, undefined]' is not assignable to type '[number, string?, boolean?]'.
  Type at position 2 in source is not compatible with type at position 2 in target.
    Type 'undefined' is not assignable to type 'boolean'.
tests/cases/compiler/strictOptionalProperties1.ts(107,7): error TS2322: Type '[number, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
  Type at position 1 in source is not compatible with type at position 1 in target.
    Type 'undefined' is not assignable to type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(111,7): error TS2375: Type '{ foo: undefined; }' is not assignable to type '{ foo?: number; }' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
  Types of property 'foo' are incompatible.
    Type 'undefined' is not assignable to type 'number'.
tests/cases/compiler/strictOptionalProperties1.ts(119,5): error TS2411: Property 'bar' of type 'string | undefined' is not assignable to 'string' index type 'string'.
tests/cases/compiler/strictOptionalProperties1.ts(190,15): error TS2451: Cannot redeclare block-scoped variable 'e'.
tests/cases/compiler/strictOptionalProperties1.ts(193,1): error TS2322: Type 'string | boolean | undefined' is not assignable to type 'string | number | undefined'.
  Type 'false' is not assignable to type 'string | number | undefined'.
tests/cases/compiler/strictOptionalProperties1.ts(194,1): error TS2412: Type 'string | boolean | undefined' is not assignable to type 'string | number' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
  Type 'undefined' is not assignable to type 'string | number'.
tests/cases/compiler/strictOptionalProperties1.ts(195,1): error TS2375: Type '{ name: string; email: undefined; }' is not assignable to type 'U2' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
  Types of property 'email' are incompatible.
    Type 'undefined' is not assignable to type 'string | number'.
tests/cases/compiler/strictOptionalProperties1.ts(206,13): error TS2451: Cannot redeclare block-scoped variable 'e'.
tests/cases/compiler/strictOptionalProperties1.ts(210,1): error TS2322: Type '{ a: number; b: string | undefined; }' is not assignable to type '{ [x: string]: string | number; }'.
  Property 'b' is incompatible with index signature.
    Type 'string | undefined' is not assignable to type 'string | number'.
      Type 'undefined' is not assignable to type 'string | number'.
tests/cases/compiler/strictOptionalProperties1.ts(211,1): error TS2322: Type 'string | boolean | undefined' is not assignable to type '{ [x: string]: string | number; }'.
  Type 'undefined' is not assignable to type '{ [x: string]: string | number; }'.


==== tests/cases/compiler/strictOptionalProperties1.ts (23 errors) ====
    function f1(obj: { a?: string, b?: string | undefined }) {
        let a = obj.a;  // string | undefined
        let b = obj.b;  // string | undefined
        obj.a = 'hello';
        obj.b = 'hello';
        obj.a = undefined;  // Error
        ~~~~~
!!! error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
        obj.b = undefined;
    }
    
    function f2(obj: { a?: string, b?: string | undefined }) {
        obj = obj;
        obj.a = obj.a;  // Error
        ~~~~~
!!! error TS2412: Type 'string | undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
!!! error TS2412:   Type 'undefined' is not assignable to type 'string'.
        obj.b = obj.b;
        if ('a' in obj) {
            obj.a;
            obj.a = obj.a;
        }
        else {
            obj.a;
            obj.a = obj.a;  // Error
            ~~~~~
!!! error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
        }
        if (obj.hasOwnProperty('a')) {
            obj.a;
            obj.a = obj.a;
        }
        else {
            obj.a;
            obj.a = obj.a;  // Error
            ~~~~~
!!! error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
        }
        if ('b' in obj) {
            obj.b;
            obj.b = obj.b;
        }
        else {
            obj.b;
            obj.b = obj.b;
        }
        if (obj.hasOwnProperty('b')) {
            obj.b;
            obj.b = obj.b;
        }
        else {
            obj.b;
            obj.b = obj.b;
        }
    }
    
    function f3(obj: Partial<{ a: string, b: string | undefined }>) {
        let a = obj.a;  // string | undefined
        let b = obj.b;  // string | undefined
        obj.a = 'hello';
        obj.b = 'hello';
        obj.a = undefined;  // Error
        ~~~~~
!!! error TS2412: Type 'undefined' is not assignable to type 'string' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
        obj.b = undefined;
    }
    
    function f4(t: [string?]) {
        let x = t[0];  // string | undefined
        t[0] = 'hello';
        t[0] = undefined;  // Error
        ~~~~
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
    }
    
    function f4a(t1: [number, string?], t2: [number, string?, string?]) {
        t1 = t2;  // Wasn't an error, but should be
        ~~
!!! error TS2322: Type '[number, string?, string?]' is not assignable to type '[number, string?]'.
!!! error TS2322:   Target allows only 2 element(s) but source may have more.
    }
    
    function f5(t: [number, string?, boolean?]) {
        t = [42];
        t = [42, 'abc'];
        t = [42, 'abc', true];
        t = [42, ,];
        t = [42, , ,];
        t = [42, , , ,];  // Error
        ~
!!! error TS2322: Type '[number, never?, never?, never?]' is not assignable to type '[number, string?, boolean?]'.
!!! error TS2322:   Target allows only 3 element(s) but source may have more.
        t = [, , true];  // Error
        ~
!!! error TS2322: Type '[never?, never?, true?]' is not assignable to type '[number, string?, boolean?]'.
!!! error TS2322:   Source provides no match for required element at position 0 in target.
        t = [42, undefined, true];  // Error
        ~
!!! error TS2322: Type '[number, undefined, true]' is not assignable to type '[number, string?, boolean?]'.
!!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
!!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
    }
    
    function f6() {
        const t1 = [1, 2] as const;
        const t2 = [1, 2, ,] as const;
        const t3 = [1, 2, , ,] as const;
        const t4 = [1, , 2] as const;
        const t5 = [1, , , 2] as const;
    }
    
    // Example from #13195
    
    type Props = {
        foo: string;
        bar: string
    }
    
    type InputProps = {
        foo?: string;
        bar: string;
    }
    
    const defaultProps: Pick<Props, 'foo'> = { foo: 'foo' };
    const inputProps: InputProps = { foo: undefined, bar: 'bar' };
          ~~~~~~~~~~
!!! error TS2375: Type '{ foo: undefined; bar: string; }' is not assignable to type 'InputProps' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
!!! error TS2375:   Types of property 'foo' are incompatible.
!!! error TS2375:     Type 'undefined' is not assignable to type 'string'.
    const completeProps: Props = { ...defaultProps, ...inputProps };
    
    // Example from #13195
    
    const t1: [number, string?, boolean?] = [1];
    const t2: [number, string?, boolean?] = [1, undefined];
          ~~
!!! error TS2322: Type '[number, undefined]' is not assignable to type '[number, string?, boolean?]'.
!!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
!!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
    const t3: [number, string?, boolean?] = [1, "string", undefined];
          ~~
!!! error TS2322: Type '[number, string, undefined]' is not assignable to type '[number, string?, boolean?]'.
!!! error TS2322:   Type at position 2 in source is not compatible with type at position 2 in target.
!!! error TS2322:     Type 'undefined' is not assignable to type 'boolean'.
    const t4: [number, string?, boolean?] = [1, undefined, undefined];
          ~~
!!! error TS2322: Type '[number, undefined, undefined]' is not assignable to type '[number, string?, boolean?]'.
!!! error TS2322:   Type at position 1 in source is not compatible with type at position 1 in target.
!!! error TS2322:     Type 'undefined' is not assignable to type 'string'.
    
    // Example from #13195
    
    const x: { foo?: number } = { foo: undefined };
          ~
!!! error TS2375: Type '{ foo: undefined; }' is not assignable to type '{ foo?: number; }' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
!!! error TS2375:   Types of property 'foo' are incompatible.
!!! error TS2375:     Type 'undefined' is not assignable to type 'number'.
    const y: { foo: number } = { foo: 123, ...x };
    
    // Index signatures and strict optional properties
    
    interface Test {
        [key: string]: string;
        foo?: string;  // Should be ok
        bar?: string | undefined;  // Error
        ~~~
!!! error TS2411: Property 'bar' of type 'string | undefined' is not assignable to 'string' index type 'string'.
    }
    
    // Strict optional properties and inference
    
    declare let ox1: { p: string };
    declare let ox2: { p: string | undefined };
    declare let ox3: { p?: string };
    declare let ox4: { p?: string | undefined };
    
    declare let tx1: [string];
    declare let tx2: [string | undefined];
    declare let tx3: [string?];
    declare let tx4: [(string | undefined)?];
    
    declare function f11<T>(x: { p?: T }): T;
    
    f11(ox1);  // string
    f11(ox2);  // string | undefined
    f11(ox3);  // string
    f11(ox4);  // string | undefined
    
    declare function f12<T>(x: [T?]): T;
    
    f12(tx1);  // string
    f12(tx2);  // string | undefined
    f12(tx3);  // string
    f12(tx4);  // string | undefined
    
    declare function f13<T>(x: Partial<T>): T;
    
    f13(ox1);  // { p: string }
    f13(ox2);  // { p: string | undefined }
    f13(ox3);  // { p: string }
    f13(ox4);  // { p: string | undefined }
    
    f13(tx1);  // [string]
    f13(tx2);  // [string | undefined]
    f13(tx3);  // [string]
    f13(tx4);  // [string | undefined]
    
    // Repro from #44388
    
    type Undefinable<T> = T | undefined;
    
    function expectNotUndefined<T>(value: Undefinable<T>): T {
        if (value === undefined) {
            throw new TypeError('value is undefined');
        }
        return value;
    }
    
    interface Bar {
        bar?: number;
    }
    
    function aa(input: Bar): void {
        const notUndefinedVal = expectNotUndefined(input.bar);
        bb(notUndefinedVal);
    }
    
    declare function bb(input: number): void;
    
    interface U1 {
        name: string
        email?: string | number | undefined
    }
    interface U2 {
        name: string
        email?: string | number
    }
    declare const e: string | boolean | undefined
                  ~
!!! error TS2451: Cannot redeclare block-scoped variable 'e'.
    declare const u1: U1
    declare let u2: U2
    u1.email = e // error, but only because boolean isn't in email's type
    ~~~~~~~~
!!! error TS2322: Type 'string | boolean | undefined' is not assignable to type 'string | number | undefined'.
!!! error TS2322:   Type 'false' is not assignable to type 'string | number | undefined'.
    u2.email = e // error, and suggest adding undefined
    ~~~~~~~~
!!! error TS2412: Type 'string | boolean | undefined' is not assignable to type 'string | number' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the type of the target.
!!! error TS2412:   Type 'undefined' is not assignable to type 'string | number'.
    u2 = {
    ~~
!!! error TS2375: Type '{ name: string; email: undefined; }' is not assignable to type 'U2' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
!!! error TS2375:   Types of property 'email' are incompatible.
!!! error TS2375:     Type 'undefined' is not assignable to type 'string | number'.
        name: 'hi',
        email: undefined
    }
    
    // Repro from #44437
    
    declare var a: {[x: string]: number | string }
    declare var b: {a: number, b: string}
    declare var c: {a: number, b?: string}
    declare var d: {a: number, b: string | undefined }
    declare var e: {a: number, b?: string | undefined }
                ~
!!! error TS2451: Cannot redeclare block-scoped variable 'e'.
    
    a = b;
    a = c;
    a = d;  // Error
    ~
!!! error TS2322: Type '{ a: number; b: string | undefined; }' is not assignable to type '{ [x: string]: string | number; }'.
!!! error TS2322:   Property 'b' is incompatible with index signature.
!!! error TS2322:     Type 'string | undefined' is not assignable to type 'string | number'.
!!! error TS2322:       Type 'undefined' is not assignable to type 'string | number'.
    a = e;  // Error
    ~
!!! error TS2322: Type 'string | boolean | undefined' is not assignable to type '{ [x: string]: string | number; }'.
!!! error TS2322:   Type 'undefined' is not assignable to type '{ [x: string]: string | number; }'.
    
    // Repro from #46004
    
    interface PropsFromReact {
        onClick?: () => void;
    }
    
    interface PropsFromMaterialUI {
        onClick?: (() => void) | undefined;
    }
    
    type TheTypeFromMaterialUI = PropsFromReact & PropsFromMaterialUI;
    
    interface NavBottomListItem extends TheTypeFromMaterialUI {
        value: string;
    }
    
    // Repro from #46004
    
    type UA = undefined;  // Explicit undefined type
    type UB = { x?: never }['x'];  // undefined from missing property
    
    type UC = UA & UB;  // undefined