Array.indexOf - searchElement is too Restrictive?

[halfnibble]

TypeScript Version: 3.8.3

Search Terms:
indexOf, too restrictive, searchElement

Expected behavior:
I expect Array.indexOf() to allow a searchElement with a type that includes and extends beyond the array. E.g. If the haystack is [2, 3], then I expect to the needle could be of type 1 | 2 | 3 and that a value of -1 would be returned if the needle is 1. But I do not expect a compiler error.

Actual behavior:
Compiler error.
Argument of type 'CoolNumbers' is not assignable to parameter of type '2 | 3'.
Type '1' is not assignable to type '2 | 3'. (2345)

Related Issues:
#29290
#35257

Code

type CoolNumbers = 1 | 2 | 3;

const B: CoolNumbers = 2;
const C: CoolNumbers = 3;

const A: CoolNumbers = Math.floor(Math.random() * 3 + 1) as CoolNumbers;

if ([B, C].indexOf(A) === -1) {  // <--- Error here.
    console.log('My favorite 2 numbers.');
} else {
    console.log("it's 1");
}

Output

"use strict";
const B = 2;
const C = 3;
const A = Math.floor(Math.random() * 3 + 1);
if ([B, C].indexOf(A) === -1) {
    console.log('My favorite 2 numbers.');
}
else {
    console.log("it's 1");
}

Compiler Options

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "ES2017",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

[RyanCavanaugh]

Root cause is #14520

[halfnibble]

Thanks for the root cause! I honestly don't understand all the terminology in that issue, but I feel like this is a fairly common use case for indexOf. Please let me know if I'm doing something wrong.

My current workaround is to typecast A as any to get past compilation errors.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.