"Found value name used as type"

[bytwise]

Trying to compile:

struct Foo {
    x: int
}

impl Fo {
    fn foo() {}
}

fn main() {}

gives the unhelpful error:

main.rs:5:5: 5:7 error: found value name used as a type: def_mod({crate: 0, node: 13})
main:rs:5 impl Fo {
               ^~

A better error message would be:

error: use of undeclared type name `Fo`

Even better would be, if it could recognize the typo:

error: use of undeclared type name `Fo`. Did you mean `Foo`?

[nikomatsakis]

The problem is not just a matter of an error message. I encountered the same error with this example:

pub mod a {
    pub struct Foo { a: uint }
}

pub mod b {
    use a::Foo;
    impl Foo { // ERROR: found value name used as type
        fn bar(&self) { }
    }
}

pub fn main() { }

Somehow the impl seems to "override" imported struct names? Or at least interact badly with them. Rewriting to impl a::Foo works.

[nikomatsakis]

Adjusting title.

[domluna]

I'm also getting the error in this context:

enum Shape {
    Circle { center: Point, radius: float },
    Rectangle { top_left: Point, bottom_right: Point }
}

impl Circle {
    fn area(&self) -> float {
        self.radius * self.radius * float::consts::pi
    }
}

I get "error: found value name used as type", so I'm thinking that because Circle is defined inside Shape it doesn't recognize Circle is actually type, due to closure I'm guessing.

One way to get around this in my particular case is defining the types outside of the Shape enum.

struct Circle { center: Point, radius: float }
struct Rectangle { top_left: Point, bottom_right: Point }

enum Shape {
    Circle,
    Rectangle
}

impl Circle {
    fn area(&self) -> float {
        self.radius * self.radius * float::consts::pi
    }
}