ICE - Option Refcount causes an LLVM assertion to fail.

[DavidJFelix]

The following code:

use std::rc::Rc

struct ProblemType {
    children [Option<Rc<ProblemType>>; 8],
}

impl ProblemType {
    fn breaks_compiler() -> Option<Rc<ProblemType>> {
        None
    }
}

Causes LLVM to fail an assertion, claiming:

rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/DataLayout.cpp:636: unsigned int llvm::DataLayout::getAlignment(llvm::Type*, bool) const: Assertion `Ty->isSized() && "Cannot getTypeInfo() on a type that is unsized!"' failed.

[dotdash]

Reduced test case:

struct Outer(*mut ProblemType);
struct ProblemType ([Outer; 8]);

fn breaks_compiler(_: Outer) {}

[dotdash]

This depends on the array in ProblemType being fixed sized, and ProblemType being either a struct or a single variant enum. Under those conditions, the code ends up trying to get the size of Outer in a state where the struct body has not yet been set.

[tamird]

Triage: no longer ICEs.

The original case:

use std::rc::Rc;

struct ProblemType {
    children: [Option<Rc<ProblemType>>; 8],
}

impl ProblemType {
    fn breaks_compiler() -> Option<Rc<ProblemType>> {
        None
    }
}

fn main() {
    // Add code here
}

as well as the reduced test case now compile without error.

[pmarcelll]

On my machine both test cases fail with the ICE mentioned in the first comment.

rustc 1.2.0-nightly (0250ff9a5 2015-06-17)

[arielb1]

Confirming still ICEs

[wheals]

This is strange: it compiles fine in stable and beta (also with rustc 1.2.0), but fails in nightly.

[arielb1]

@wheals

LLVM assertions are disabled in stable/beta.

[arielb1]

duplicate of #19001