Reduce size of InterpErrorInfo to 8 bytes

compiler/rustc_mir/src/const_eval/error.rs

@@ -84,7 +84,11 @@ impl<'tcx> ConstEvalErr<'tcx> {
     {
         error.print_backtrace();
         let stacktrace = ecx.generate_stacktrace();
-        ConstEvalErr { error: error.kind, stacktrace, span: span.unwrap_or_else(|| ecx.cur_span()) }
+        ConstEvalErr {
+            error: error.into_kind(),
+            stacktrace,
+            span: span.unwrap_or_else(|| ecx.cur_span()),
+        }
     }
 
     pub fn struct_error(

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -230,7 +230,7 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
         };
         return eval_nullary_intrinsic(tcx, key.param_env, def_id, substs).map_err(|error| {
             let span = tcx.def_span(def_id);
-            let error = ConstEvalErr { error: error.kind, stacktrace: vec![], span };
+            let error = ConstEvalErr { error: error.into_kind(), stacktrace: vec![], span };
             error.report_as_error(tcx.at(span), "could not evaluate nullary intrinsic")
         });
     }

compiler/rustc_mir/src/const_eval/machine.rs

@@ -245,8 +245,8 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
         Ok(Some(match ecx.load_mir(instance.def, None) {
             Ok(body) => body,
             Err(err) => {
-                if let err_unsup!(NoMirFor(did)) = err.kind {
-                    let path = ecx.tcx.def_path_str(did);
+                if let err_unsup!(NoMirFor(did)) = err.kind() {
+                    let path = ecx.tcx.def_path_str(*did);
                     return Err(ConstEvalErrKind::NeedsRfc(format!(
                         "calling extern function `{}`",
                         path