diff --git a/core/ast/printer.py b/core/ast/printer.py
index c624637..4394834 100644
--- a/core/ast/printer.py
+++ b/core/ast/printer.py
@@ -1,9 +1,11 @@
+from __future__ import annotations
+
 from contextlib import contextmanager
 from enum import Enum, auto
 import io
-from typing import Generator, Optional
+from typing import Generator, Generic, Optional, Protocol, TypeVar
 
-from core.ast.annotations import Expr, TypeExpr, SchemaExpr, SchemaElementExpr
+import core.ast.annotations as a
 
 
 class _Level(Enum):
@@ -12,7 +14,14 @@ class _Level(Enum):
     LAST = auto()
 
 
-class AnnotationAstPrinter(Expr.Visitor[None]):
+class Expr(Protocol):
+    def accept(self, printer: AstPrinter) -> None: ...
+
+
+T = TypeVar("T", bound=Expr)
+
+
+class AstPrinter(Generic[T]):
     LAST_CHILD = "└── "
     CHILD = "├── "
     VERTICAL = "│   "
@@ -23,7 +32,7 @@ class AnnotationAstPrinter(Expr.Visitor[None]):
         self._idx: Optional[int] = None
         self._buf: io.StringIO = io.StringIO()
 
-    def print(self, expr: Expr):
+    def print(self, expr: T):
         self._buf = io.StringIO()
         expr.accept(self)
         return self._buf.getvalue()
@@ -60,7 +69,7 @@ class AnnotationAstPrinter(Expr.Visitor[None]):
         return "".join(parts)
 
     def _write_optional_child(
-        self, label: str, child: Optional[Expr], *, last: bool = False
+        self, label: str, child: Optional[T], *, last: bool = False
     ):
         if last:
             self._mark_last()
@@ -71,13 +80,15 @@ class AnnotationAstPrinter(Expr.Visitor[None]):
             with self._child_level(last=True):
                 child.accept(self)
 
-    def visit_type_expr(self, expr: TypeExpr):
+
+class AnnotationAstPrinter(AstPrinter, a.Expr.Visitor[None]):
+    def visit_type_expr(self, expr: a.TypeExpr):
         self._write_line("TypeExpr")
         with self._child_level():
             self._write_line(f'name: "{expr.name.lexeme}"')
             self._write_optional_child("schema", expr.schema, last=True)
 
-    def visit_schema_expr(self, expr: SchemaExpr):
+    def visit_schema_expr(self, expr: a.SchemaExpr):
         self._write_line("SchemaExpr")
         with self._child_level():
             for i, elmt in enumerate(expr.elements):
@@ -86,7 +97,7 @@ class AnnotationAstPrinter(Expr.Visitor[None]):
                     self._mark_last()
                 elmt.accept(self)
 
-    def visit_schema_element_expr(self, expr: SchemaElementExpr):
+    def visit_schema_element_expr(self, expr: a.SchemaElementExpr):
         self._write_line("SchemaElementExpr")
         with self._child_level():
             name_text: str = "None" if expr.name is None else f'"{expr.name.lexeme}"'
@@ -94,23 +105,23 @@ class AnnotationAstPrinter(Expr.Visitor[None]):
             self._write_optional_child("type", expr.type, last=True)
 
 
-class AnnotationPrinter(Expr.Visitor[str]):
-    def print(self, expr: Expr):
+class AnnotationPrinter(a.Expr.Visitor[str]):
+    def print(self, expr: a.Expr):
         return expr.accept(self)
 
-    def visit_type_expr(self, expr: TypeExpr) -> str:
+    def visit_type_expr(self, expr: a.TypeExpr) -> str:
         schema: str = ""
         if expr.schema is not None:
             schema = expr.schema.accept(self)
         return f"{expr.name.lexeme}{schema}"
 
-    def visit_schema_expr(self, expr: SchemaExpr) -> str:
+    def visit_schema_expr(self, expr: a.SchemaExpr) -> str:
         res: str = expr.left.lexeme
         res += ", ".join(elmt.accept(self) for elmt in expr.elements)
         res += expr.right.lexeme
         return res
 
-    def visit_schema_element_expr(self, expr: SchemaElementExpr) -> str:
+    def visit_schema_element_expr(self, expr: a.SchemaElementExpr) -> str:
         parts: list[str] = []
         if expr.name is not None:
             parts.append(expr.name.lexeme)