Refactor fieldRef to be compliant with the Liskov Substitution Principle

crashlink/core.py

@@ -256,10 +256,17 @@ class fieldRef(ResolvableVarInt):
     """
     Abstract class to represent a field index.
     """
-
-    def resolve(self, code: "Bytecode", obj: "Obj") -> "Field":
-        fields = obj.resolve_fields(code)
-        return fields[self.value]
+
+    obj: Optional["Obj"] = None
+
+    def resolve(self, code: "Bytecode") -> "Field":
+        if self.obj:
+            return self.obj.resolve_fields(code)[self.value]
+        raise ValueError("Cannot resolve field without context. Try setting `field.obj` to an instance of `Obj`, or use `field.resolve_obj(code, obj)` instead.")
+
+    def resolve_obj(self, code: "Bytecode", obj: "Obj") -> "Field":
+        self.obj = obj
+        return obj.resolve_fields(code)[self.value]
 
 
 class Reg(ResolvableVarInt):

crashlink/disasm.py

@@ -157,7 +157,7 @@ def pseudo_from_op(
                 this = reg.resolve(code)
                 break
         if this:
-            return f"reg{op.definition['dst']} = this.{op.definition['field'].resolve(code, this.definition).name.resolve(code)}"
+            return f"reg{op.definition['dst']} = this.{op.definition['field'].resolve_obj(code, this.definition).name.resolve(code)}"
         return f"reg{op.definition['dst']} = this.f@{op.definition['field'].value} (this not found!)"
     elif op.op == "Label":
         return "label"
@@ -209,14 +209,14 @@ def pseudo_from_op(
     elif op.op == "Field":
         field = (
             op.definition["field"]
-            .resolve(code, regs[op.definition["obj"].value].resolve(code).definition)
+            .resolve_obj(code, regs[op.definition["obj"].value].resolve(code).definition)
             .name.resolve(code)
         )
         return f"reg{op.definition['dst']} = reg{op.definition['obj']}.{field}"
     elif op.op == "SetField":
         field = (
             op.definition["field"]
-            .resolve(code, regs[op.definition["obj"].value].resolve(code).definition)
+            .resolve_obj(code, regs[op.definition["obj"].value].resolve(code).definition)
             .name.resolve(code)
         )
         return f"reg{op.definition['obj']}.{field} = reg{op.definition['src']}"