LLVM assertion with overloaded call and trait coercion.

[luqmana]

Reported by @sfackler

#![feature(overloaded_calls)]

trait Foo {}

struct Bar;

impl<'a> std::ops::Fn<(&'a Foo,), ()> for Bar {
    fn call(&self, _: (&'a Foo,)) {}
}

struct Baz;

impl Foo for Baz {}

fn main() {
    let bar = Bar;
    let baz = &Baz;
    bar(baz);
}

rustc: /scratch/laden/rust/src/llvm/lib/IR/Instructions.cpp:281: void llvm::CallInst::init(llvm::Value*, llvm::ArrayRef<llvm::Value*>, const llvm::Twine&): Assertion `(i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && "Calling a function with a bad signature!"' failed.

[sfackler]

Dup of #14958