unexpected callee type - compiler panicked

[blairn]

While trying to learn how to return a closure.... I came across this..

fn foo(x: i32) {
        |y| x + y
}

fn main() {
        let x = foo(5)(2);
}

gives....

2:12 error: can't infer the "kind" of the closure, explicitly annotate it. e.g. `|&:| {}`
src/hello_world.rs:2        |y| x + y
                            ^~~~~~~~~
src/hello_world.rs:2:3: 2:12 error: mismatched types: expected `()`, found `closure[src/hello_world.rs:2:3: 2:12]` (expected (), found closure)
src/hello_world.rs:2        |y| x + y
                            ^~~~~~~~~
src/hello_world.rs:6:11: 6:20 error: expected function, found `()`
src/hello_world.rs:6        let x = foo(5)(2);
                                    ^~~~~~~~~
src/hello_world.rs:6:11: 6:17 error: internal compiler error: unexpected callee type ()
src/hello_world.rs:6        let x = foo(5)(2);
                                    ^~~~~~
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:123

[kyledewey]

Commenting-out the body of foo still results in an ICE.

[nikomatsakis]

I can't seem to produce an ICE no matter what I do.

[bombless]

Those closure kinds info are already gone, so I think many related bugs are gone as well.
e.g. I cannot reproduce a bug related to closure kinds and macro #21087