LLVM assertion failure with moving boxed DST

[apasel422]

The following successfully typechecks on rustc 1.12.0-nightly (b30eff7ba 2016-08-05), but generates an LLVM assertion failure:

struct Node<T: ?Sized + Send> {
    next: Option<Box<Node<Send>>>,
    value: T,
}

fn clear(head: &mut Option<Box<Node<Send>>>) {
    while let Some(node) = head.take() {
        *head = node.next;
    }
}

fn main() {}

Error:

rustc: /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/Instructions.cpp:263: void llvm::CallInst::init(llvm::FunctionType*, llvm::Value*, llvm::ArrayRef<llvm::Value*>, llvm::ArrayRef<llvm::OperandBundleDefT<llvm::Value*> >, const llvm::Twine&): Assertion `(i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && "Calling a function with a bad signature!"' failed.

Note that replacing *head = node.next with *head = node.next.take() (and making node mutable) allows compilation to succeed.

[TimNN]

First occurs in nightly-2016-08-03 which turns on mir by default, does not occur on nightly-2016-08-03 with -Z orbit=off.

[TimNN]

Using -Z orbit this was introduced between nightly-2016-06-05 and nightly-2016-06-06 (Changes).

[nikomatsakis]

Problem seems to be that we call the drop with a fat pointer as 2 arguments, but it expects a pointer to a tuple.

[nikomatsakis]

I have a fix for this, running the full make check locally now to see if I broke anything else on the way.