Claude's declass improvements

compiler/src/regify/mod.rs

@@ -167,6 +167,17 @@ fn walk_block(
             None => (),
         }
 
+        // A field write is a define whose result lands back in the object's own
+        // value, so later reads of that object see the field. This is what lets
+        // a chain of writes to one local build a single object type, and it is
+        // why no later stage needs to know PutField at all.
+        if instr.op == OpCode::PutField {
+            out_instr.op = OpCode::DefineField;
+            out_instr.dsts.push(out_instr.args[1]);
+            out[instr_idx] = out_instr;
+            continue;
+        }
+
         // Handle this instr's pushes
         for _ in 0..n_push {
             let v = fresh_val();