Experimental support for sealed class

Related to jspahrsummers#45

.vscode/settings.json

@@ -1,15 +1,14 @@
 {
     "editor.formatOnPaste": true,
     "editor.formatOnSave": true,
-    "python.formatting.provider": "yapf",
+    "python.formatting.provider": "black",
     "python.linting.mypyArgs": [
         "--strict",
         "--ignore-missing-imports",
         "--implicit-reexport",
         "--follow-imports=silent",
         "--show-column-numbers"
     ],
-    "python.pythonPath": "venv/bin/python3",
     "python.testing.unittestArgs": [
         "-v",
         "-s",

adt/decorator.py

@@ -1,8 +1,18 @@
 # mypy: no-warn-unused-ignores
 from enum import Enum
-from typing import Any, Callable, Type, TypeVar, no_type_check
+from typing import Any, Callable, Tuple, Type, TypeVar, no_type_check
 
-from adt.case import CaseConstructor
+from adt.case import CaseConstructor, Case
+
+
+def get_case(type_obj):
+    if isinstance(type_obj, type):
+        return Case[type_obj]
+    if type_obj is None:
+        return Case
+    if type_obj._name == "Tuple":
+        return Case[type_obj.__args__]
+    return Case
 
 
 @no_type_check
@@ -14,8 +24,8 @@ def adt(cls):
         return cls
 
     caseConstructors = {
-        k: constructor
-        for k, constructor in annotations.items()
+        k: get_case(typename)
+        for k, typename in annotations.items()
         if not k.startswith("__")
     }
 
@@ -25,9 +35,7 @@ def adt(cls):
                 f"Annotation {k} should be a Case[…] constructor, got {constructor!r} instead"
             )
 
-    cls._Key = Enum(  # type: ignore
-        "_Key", list(caseConstructors.keys())
-    )
+    cls._Key = Enum("_Key", list(caseConstructors.keys()))  # type: ignore
 
     cls._types = list(x.getTypes() for x in list(caseConstructors.values()))
 
@@ -107,7 +115,8 @@ def _hash(self: Any) -> int:
 def _installOneConstructor(cls: Any, case: Enum) -> None:
     def constructor(cls: Type[Any], *args: Any, _case: Enum = case) -> Any:
         return cls(
-            key=_case, value=cls.__annotations__[_case.name].constructCase(*args)
+            key=_case,
+            value=get_case(cls.__annotations__[_case.name]).constructCase(*args),
         )
 
     if hasattr(cls, case.name):

examples/sealed.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+
+from adt import adt as sealed
+from dataclasses import dataclass
+from typing import Tuple
+
+
+@sealed
+class Sealed1:
+    EMPTY: None
+    INTEGER: int
+    STRING_PAIR: Tuple[str, str]
+
+
+x1 = Sealed1.INTEGER(5)
+print(x1.integer())
+x2 = Sealed1.EMPTY()
+print(x2.empty())
+x3 = Sealed1.STRING_PAIR("foo", "bar")
+print(x3.string_pair())
+
+
+@dataclass
+class Leaf:
+    data: int
+
+
+@dataclass
+class Node:
+    left: "Tree"
+    right: "Tree"
+
+
+@sealed
+class Tree:
+    EMPTY: None
+    LEAF: Leaf
+    NODE: Node
+
+
+t1 = Tree.EMPTY()
+t2 = Tree.LEAF(3)
+t3 = Tree.NODE((Tree.LEAF(3), Tree.LEAF(4)))
+print(t1, t2, t3)