Compiler panicked "ident only path should have been covered already"

[e-oz]

Hello.
Trying to learn Rust, playing with closures. Compiler asked me to report bug.

Code:

fn main() {
    let caller<F> = |f: F|
    where F: Fn() -> i32
    {
        let x = f();
        println!("Y {}",x);
        return x;
    };

    caller(bar_handler);
}

fn bar_handler() -> i32 {
    println!("zz");
    return 5;
}

Error:

 cargo run RUST_BACKTRACE=1
   Compiling app v0.0.1
src/main.rs:2:6: 2:12 error: internal compiler error: ident only path should have been covered already
src/main.rs:2   let caller<F> = |f: F|
                    ^~~~~~
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libsyntax/diagnostic.rs:129

File /Users/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-mac/build/src/libsyntax/diagnostic.rs doesn't exist, folder /Users/rustbuild/ too.

In this code I tried to create closure with function as first argument, but can't yet find how to declare it. But it's offtopic :)

[jdm]

Probably the same as #22426 and #22589.