wish python had lexical scoping

Justfile

@@ -3,6 +3,7 @@ watch:
 
 fmt:
     pipenv run black .
+    dos2unix *
 
 run:
     mypy *.py

aggen.py

@@ -12,6 +12,21 @@ global i
 i = 0
 
 
+def gensym(prefix: str = "", suffix: str = "") -> str:
+    global i
+    presan = re.sub("[^0-9a-zA-Z]+", "_", prefix)
+    sufsan = re.sub("[^0-9a-zA-Z]+", "_", suffix)
+    i += 1
+    return f"{presan}{i}{sufsan}"
+
+
+class NodeDesc:
+    def __init__(self, node: Node):
+        self.node = node
+        self.name = node.name
+        self.nonterminal = gensym(node.name.lower())
+
+
 class GenResult:
     def __init__(self, pd: str = "", ex: str = ""):
         self.literals: Dict[str, str] = dict()
@@ -43,13 +58,6 @@ class GenResult:
 def gen(program: List[Decl]) -> GenResult:
     res = GenResult()
 
-    def gen(prefix: str = "", suffix: str = "") -> str:
-        global i
-        presan = re.sub("[^0-9a-zA-Z]+", "_", prefix)
-        sufsan = re.sub("[^0-9a-zA-Z]+", "_", suffix)
-        i += 1
-        return f"{presan}{i}{sufsan}"
-
     def v(name: str) -> str:
         return f"__ag_{name}"
 
@@ -116,42 +124,41 @@ def gen(program: List[Decl]) -> GenResult:
             return dict()
         raise Exception(f"unhandled {expr.__class__}")
 
-    node_map = dict(
+    node_map: Dict[str, NodeDesc] = dict(
-        map(lambda n: (n.name, n), filter(lambda c: isinstance(c, Node), program))
+        map(
-    )
+            lambda n: (n.name, NodeDesc(cast(Node, n))),
-    node_name_map = dict(
+            filter(lambda c: isinstance(c, Node), program),
-        map(lambda n: (n[0], gen(n[1].name.lower())), node_map.items())
+        )
     )
 
-    for node in node_map.values():
+    for node_desc in node_map.values():
-        node = cast(Node, node)
+        assert isinstance(node_desc, NodeDesc)
-        node_name_lower = node.name.lower()
+
-        node_name = node_name_map[node.name]
+        res.starts.add(node_desc.name.lower())
-        res.parse_rules[f"?{node_name_lower}"].append(node_name)
+        res.parse_rules[f"?{node_desc.name.lower()}"].append(node_desc.nonterminal)
-        res.starts.add(node_name_lower)
 
         class_decl = textwrap.dedent(
             f"""
-            class {v(node_name)}: pass
+            class {node_desc.nonterminal}: pass
         """
         )
         res.extra += class_decl
 
-        print(node.name, node.ifaces)
+        print(node_desc.name, node_desc.node.ifaces)
 
-        for variant in node.variants:
+        for variant in node_desc.node.variants:
-            v_class_name = gen(f"{node_name}_var")
+            v_class_name = gensym(f"{node_desc.nonterminal}_var")
             class_decl = textwrap.dedent(
                 f"""
-                class {v(v_class_name)}({v(node_name)}):
+                class {v_class_name}({node_desc.nonterminal}):
                     ''' '''
                     pass
             """
             )
             res.extra += class_decl
 
-            prod_name = gen(node_name + "_")
+            prod_name = gensym(node_desc.nonterminal + "_")
-            res.parse_rules[node_name].append(prod_name)
+            res.parse_rules[node_desc.nonterminal].append(prod_name)
             print("PRODUCTION", prod_name, variant.prod)
 
             # resolving a production just means checking to make sure it's a
@@ -160,18 +167,18 @@ def gen(program: List[Decl]) -> GenResult:
                 print(f"resolve_production({sym})")
                 if isinstance(sym, SymRename):
                     if isinstance(sym.ty, NodeRefByName):
-                        if sym.ty.name in node_name_map:
+                        if sym.ty.name in node_map:
-                            return node_name_map[sym.ty.name]
+                            return node_map[sym.ty.name].nonterminal
                         else:
                             raise Exception(
                                 f"unresolved name {sym.ty.name} in production"
                             )
                     elif isinstance(sym.ty, NodeRegex):
-                        sym_name = gen("sym")
+                        sym_name = gensym("sym")
                         res.literals[sym_name] = f"/{sym.ty.pat.pattern}/"
                         return sym_name
                 elif isinstance(sym, SymLit):
-                    sym_name = gen("lit")
+                    sym_name = gensym("lit")
                     # hack to make repr have double quotes
                     res.literals[sym_name] = json.dumps(sym.lit)
                     return sym_name
@@ -195,8 +202,8 @@ def gen(program: List[Decl]) -> GenResult:
             # trying to compute, and generate a thunk corresponding to
             # that value.
             for eq in variant.equations:
-                eq_name = gen(f"eq_{node.name}")
+                eq_name = gensym(f"eq_{node_desc.name}")
-                thunk_name = gen(f"thunk_{node.name}")
+                thunk_name = gensym(f"thunk_{node_desc.name}")
 
                 print("RHS", eq.rhs, eq.rhs.id)
                 collect_required_thunks(copy.deepcopy(env), eq.rhs)
@@ -213,8 +220,4 @@ def gen(program: List[Decl]) -> GenResult:
                 print(f"```py\n{func_impl}\n```")
                 res.extra += func_impl
 
-        # this is a "type alias" that connects it to one of the generated
-        # names above
-        res.extra += f"{node.name} = {v(node_name)}"
-
     return res

agmain.py

@@ -9,7 +9,7 @@ from aggen import *
 p = Lark(open("grammar.lark").read(), start="program", parser="lalr")
 
 if __name__ == "__main__":
-    with open("arith.ag") as f:
+    with open("test/arith.ag") as f:
         data = f.read()
 
     cst = p.parse(data)