implement valtrees as the type-system representation for constant values

1 files changed, 11 insertions, 1 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index c95d43b71cf..a63790b594d 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -6,6 +6,7 @@ use super::*;
 use crate::infer::region_constraints::{Constraint, RegionConstraintData};
 use crate::infer::InferCtxt;
 use crate::traits::project::ProjectAndUnifyResult;
+use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{Region, RegionVid, Term};
 
@@ -834,7 +835,16 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                                 unevaluated,
                                 Some(obligation.cause.span),
                             ) {
-                                Ok(val) => Ok(ty::Const::from_value(select.tcx(), val, c.ty())),
+                                Ok(Some(valtree)) => {
+                                    Ok(ty::Const::from_value(select.tcx(), valtree, c.ty()))
+                                }
+                                Ok(None) => {
+                                    let tcx = self.tcx;
+                                    let def_id = unevaluated.def.did;
+                                    let reported = tcx.sess.struct_span_err(tcx.def_span(def_id), &format!("unable to construct a constant value for the unevaluated constant {:?}", unevaluated)).emit();
+
+                                    Err(ErrorHandled::Reported(reported))
+                                }
                                 Err(err) => Err(err),
                             }
                         } else {