Fix an ICE in conflict errors diagnostics

Author: WaffleLapkin

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1359,7 +1359,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
 
         // Get closure's arguments
-        let ty::Closure(_, substs) = typeck_results.expr_ty(closure_expr).kind() else { unreachable!() };
+        let ty::Closure(_, substs) = typeck_results.expr_ty(closure_expr).kind() else { /* hir::Closure can be a generator too */ return };
         let sig = substs.as_closure().sig();
         let tupled_params =
             tcx.erase_late_bound_regions(sig.inputs().iter().next().unwrap().map_bound(|&b| b));

tests/ui/generator/issue-110929-generator-conflict-error-ice.rs

@@ -1,12 +1,12 @@
 // edition:2021
 // compile-flags: -Zdrop-tracking-mir=yes
-// failure-status: 101
 #![feature(generators)]
 
 fn main() {
     let x = &mut ();
     || {
         let _c = || yield *&mut *x;
         || _ = &mut *x;
+        //~^ cannot borrow `*x` as mutable more than once at a time
     };
 }