Span trace utilities and runner source hint

src/mir/builder/ssa/local.rs

@@ -121,7 +121,9 @@ pub fn ensure(builder: &mut MirBuilder, v: ValueId, kind: LocalKind) -> ValueId
             // CRITICAL FIX: For receiver kind, if type is missing but origin exists,
             // infer MirType::Box from origin
             if kind == LocalKind::Recv && builder.value_types.get(&loc).is_none() {
-                builder.value_types.insert(loc, crate::mir::MirType::Box(cls));
+                builder
+                    .value_types
+                    .insert(loc, crate::mir::MirType::Box(cls));
             }
         }
         builder.local_ssa_map.insert(key, loc);