Inconsistent recursive type allowed by Typescript #38098

TypeScript Version:

3.8.3

Search Terms:

Recursive type, recursive type alias, inconsistent type

Code

type M<T> = { value: T };
interface M2 extends M<M3> {};  // M2 = { value: M3 }
type M3 = M2[keyof M2];         // M3 = M3

function f(m: M3) {
  return m.value;
}

Expected behavior:

Typescript should either show an error message on M3 signalling the inconsistent type or consistently infer M3 to be never.

Actual behavior:

Typescript accepts M3 as a valid type. When I hover over the parameter type of m in the function it infers type M3 = any, while when used as a value (e.g. m.value it infers it as never).

Playground Link:

https://www.typescriptlang.org/play/?ssl=8&ssc=1&pln=1&pc=1#code/C4TwDgpgBAsgPAFQHxQLxQN5QG4EMA2ArhAFxQJQC+A3ALABQAlgHbAQBOAZrgMbQwAmKBAAebZgBMAzrDgwAzCgw0oUAPRrYQ9FjxFSseVQahIhtFoDaAawggA9py0BdaqvceN59AoYNOhMw8wIz2zFCcABQAtmQKAJSYDKrsEMCE7OHRAHR6xHT0lAxAA

Related Issues:

None