LUB coercions works for a function but fails for a closure

[kpazman]

I tried the following code (playground), following the examples for LUB coercion in the Reference, chapter 10.7.

The closure does not compile

    let clo = || {
        if true {
            let x: *mut i32 = &mut 1;
            x
        } else if false {
            let x: &i32 = &1;
            x
        } else {
            let x: &mut i32 = &mut 1;
            x
        }
    };
    let _: *const i32 = clo();

with the error:

error[E0308]: `if` and `else` have incompatible types

A similar function does compile:

fn f() -> *const i32 {
    if true {
        let x: *mut i32 = &mut 1;
        x
    } else if false {
        let x: &i32 = &1;
        x
    } else {
        let x: &mut i32 = &mut 1;
        x
    }
}

According to the Reference, I expected that either both the closure and the function compiles or neither of them.

[cyrgani]

Note that this compiles if you explicitly state what the closure should return:

let clo = || -> *const i32 {
    ...
};

I think that the unannotated closure does not compile because the compiler will first see that x should be an *mut i32 and then try to coerce &i32 to *mut i32, which it cannot. With the annotated closure or explicit function, it understands to coerce into *const i32 and succeed.