Debuginfo is emitted for some unreachable code, crashes

[Jojoshua]

error: internal compiler error: debuginfo::create_local_var_metadata() - Referenced variable location is not an alloca!
Test.rs:131 let take = if num_items <= split_by {
^~~~
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', C:\bot\slave\nightly-dist-rustc-win-64\build\src\libsyntax\diagnostic.rs:130

[steveklabnik]

Can you share the code please?

[Jojoshua]

Maybe it is a cargo issue. I was using cargo build but rustc worked

fn main(){

return; 
let num_items = 100;
let mut split_by = 50;
let mut start_at = 0;
let mut count = 0;  
let take = if num_items <= split_by { 
              split_by = 1;               
              num_items //Take all items at once in this case
            } else {                    
                num_items / split_by    // Take x number at a time                      
            };  

}

[jdm]

The Cargo build adds -g by default, which is what triggers this.

[jdm]

What version of rustc are you using (rustc --version)? This looks very similar to #20312.

[Jojoshua]

I am using the latest version (installed today).

[Jojoshua]

Yes 20312 looks exactly the same.

[jdm]

cc @michaelwoerister

[michaelwoerister]

Hm, maybe the LLVM basic-blocks in the nested expressions are not marked as unreachable during trans?

[michaelwoerister]

PR #23066 which fixes this (but needs close review for unintended side-effects) is open for a while now. Nothing new on this issue otherwise.