declare function f(fun: <T>(t: T) => void): void
f((t) => {
type T = typeof t
type IsStringArray = T[] extends string[] ? true : false // false
})
function g<T>(t: T) {
type IsStringArray = T extends string[] ? true : false // T extends string[] ? true : false
}
IsStringArray is false in the parameter of f, while is T extends string[] ? true : false in the body of g.
What make the difference?
https://www.typescriptlang.org/play/?ssl=10&ssc=2&pln=1&pc=1#code/CYUwxgNghgTiAEAzArgOzAFwJYHtVIAoVUAueAHgBUA+AjMygSngF5r4A3HLYRsrngChEBOszbwA3oPiz4GAJ4AHBJVbzlIHInky5ilfACSAZwDKGGFlQBzAIIwYUBesoBtALrwQADwwhUYBN4E0trG094AH55GGQEMkQoCBMEAHo0pGTUwUEAX0Zc4kxcfBsqWnp4Jik9WQMEUwsrWwcnFxZq7z8AoJCw20iYy3j4ROz0zLVff0Dg0JaIr2G4hKyUkHygA
I expected two types are the same
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