Cache eval_to_allocation_raw on disk

compiler/rustc_middle/src/mir/interpret/value.rs

@@ -13,7 +13,7 @@
 use super::{sign_extend, truncate, AllocId, Allocation, InterpResult, Pointer, PointerArithmetic};
 
 /// Represents the result of const evaluation via the `eval_to_allocation` query.
-#[derive(Clone, HashStable)]
+#[derive(Clone, HashStable, TyEncodable, TyDecodable)]
 pub struct ConstAlloc<'tcx> {
     // the value lives here, at offset 0, and that allocation definitely is a `AllocKind::Memory`
     // (so you can use `AllocMap::unwrap_memory`).

compiler/rustc_middle/src/query/mod.rs

@@ -716,6 +716,10 @@ fn describe_as_module(def_id: LocalDefId, tcx: TyCtxt<'_>) -> String {
                 "const-evaluating + checking `{}`",
                 key.value.display(tcx)
             }
+            cache_on_disk_if(_, opt_result) {
+                // Only store results without errors
+                opt_result.map_or(true, |r| r.is_ok())
+            }
         }
 
         /// Evaluates const items or anonymous constants