E151: A generic struct declared inside a function

A struct can be declared inside a function body, for a type only that function uses:

fn area(w: int, h: int): int {    struct Rect { w: int, h: int }    mut r: Rect = Rect::default();    r.w = w;    r.h = h;    return r.w * r.h;}

Such a local struct can’t have type parameters. A local type has no methods, so a type parameter would have nothing to use it, and E151 is writing one anyway:

fn f(): int {    struct Box<T> { v: T }   // E151    ...}

Declare the generic struct at the top level of the file instead, where its methods can be written too, or give the local struct’s fields concrete types.

Run turf --explain E151 in a terminal to read this again.