Rust 1.20.0-nightly ICE with never_type: Broken MIR #43061

Activity

1. sfackler

   added

   I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️

   on Jul 5, 2017
2. Mark-Simulacrum

   added

   C-bugCategory: This is a bug.Category: This is a bug.

   on Jul 22, 2017
3. SimonSapin commented on Nov 26, 2017

   

   SimonSapin

   on Nov 26, 2017

   Contributor

   More actions

   What’s the correct fix? Compiler error with a nice error message?
4. arielb1 commented on Nov 26, 2017

   

   arielb1

   on Nov 26, 2017

   Contributor

   More actions

   @SimonSapin

   I think this should compile and UB, but a lint against this is probably a good idea.
5. varkor commented on Dec 31, 2017

   

   varkor

   on Dec 31, 2017

   Last edited by varkor

   Contributor

   More actions

   Reduced test case:

   // error: internal compiler error: broken MIR in NodeId(4) (_2 = ()):
   //     bad assignment (! = ()): Sorts(ExpectedFound { expected: !, found: () })
   #![crate_type = "lib"]
   #![feature(never_type)]
   
   fn blah(x: !) {
       x;
       // () // Uncommenting this explicit unit return avoids the ICE
   }
6. varkor commented on Jan 9, 2018

   

   varkor

   on Jan 9, 2018

   Contributor

   More actions

   I'm working on a fix for this. Progress on this branch. The idea is to avoid the typing issues entirely by terminating the blocks with unreachable as soon as a !-value is constructed. Currently the examples given here are fixed, but some more convoluted examples still crash.
7. bors

   closed this as completedin #47746on Jan 28, 2018