const_caller_location: edit FIXME to explain use of

Author: cachebag

compiler/rustc_const_eval/src/util/caller_location.rs

@@ -61,14 +61,14 @@ pub(crate) fn const_caller_location_provider(
     trace!("const_caller_location: {}:{}:{}", file, line, col);
     let mut ecx = mk_eval_cx_to_read_const_val(
         tcx,
-        rustc_span::DUMMY_SP, // FIXME: use a proper span here?
+        rustc_span::DUMMY_SP, // This interpreter cannot fail, so the span is irrelevant
         ty::TypingEnv::fully_monomorphized(),
         CanAccessMutGlobal::No,
     );
 
     let loc_place = alloc_caller_location(&mut ecx, file, line, col);
     if intern_const_alloc_recursive(&mut ecx, InternKind::Constant, &loc_place).is_err() {
-        bug!("intern_const_alloc_recursive should not error in this case")
+        bug!("intern_const_alloc_recursive should not error in const_caller_location_provider")
     }
     mir::ConstValue::Scalar(Scalar::from_maybe_pointer(loc_place.ptr(), &tcx))
 }