Implicits break when resolved to the same function.

[m-kurtenacker]

Example code:

implicit fn(f32) -> f32 = @|a| { a };
implicit fn(f16) -> f32 = @|a| { a as f32 };
fn convert_manual (a : f16) { a as f32 }

fn foo[A, B](a : &[A], b : &[B], implicit convert_A: fn(A) -> f32, implicit convert_B: fn(B) -> f32) {
    for _ in range(0, 42) {
        convert_A(a(0));
    }

    convert_B(b(0));
}

#[export]
fn bar (a : &[f16], b : &[f16]) -> () {
    foo[f16, f16](a, b);
}

This triggers artic: thorin/src/thorin/analyses/scope.cpp:93: void thorin::Scope::verify(): Assertion `cont_scope.has_free_params()' failed.. The IR obtained using --emit-thorin also looks broken, i.e. the function bar is not printed.