feat(checker): add members registry

midas/checker/midas.py

@@ -85,15 +85,19 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[Type
 
     def visit_extend_stmt(self, stmt: m.ExtendStmt) -> None:
         self._resolve_type_params(stmt.params)
-        base: Type = stmt.type.accept(self)
-        for op in stmt.operations:
-            right: Type = op.operand.accept(self)
-            result: Type = op.result.accept(self)
-            self.types.define_operation(
-                left=base,
-                operator=op.name.lexeme,
-                right=right,
-                result=result,
+        base_name: str = stmt.name.lexeme
+        try:
+            _ = self.get_type(base_name)
+        except NameError:
+            self.reporter.error(stmt.name.get_location(), f"Unknown type '{base_name}'")
+
+        for member in stmt.members:
+            member_type: Type = member.type.accept(self)
+            self.types.define_member(
+                base_name,
+                member.name.lexeme,
+                member_type,
+                member.kind == m.MemberKind.METHOD,
             )
 
     def visit_op_stmt(self, stmt: m.OpStmt) -> None: ...

midas/checker/registry.py

@@ -1,3 +1,4 @@
+import logging
 from typing import Optional
 
 from midas.checker.builtins import BUILTIN_SUBTYPES
@@ -9,6 +10,7 @@ from midas.checker.types import (
     Function,
     GenericType,
     Operation,
+    OverloadedFunction,
     Type,
     substitute_typevars,
 )
@@ -16,7 +18,9 @@ from midas.checker.types import (
 
 class TypesRegistry:
     def __init__(self) -> None:
+        self.logger: logging.Logger = logging.getLogger("TypesRegistry")
         self._types: dict[str, Type] = {}
+        self._members: dict[str, dict[str, Type]] = {}
         self._operations: dict[Operation.CallSignature, Type] = {}
 
     def get_type(self, name: str) -> Type:
@@ -86,6 +90,28 @@ class TypesRegistry:
         self._types[name] = type
         return type
 
+    def define_member(
+        self, type_name: str, member_name: str, member_type: Type, is_method: bool
+    ):
+        members: dict[str, Type] = self._members.setdefault(type_name, {})
+        if member_name in members:
+            if not is_method:
+                self.logger.error(
+                    f"Member '{member_name}' already defined for type {type_name}"
+                )
+                return
+            current: Type = members[member_name]
+            combined: Type
+            match current:
+                case OverloadedFunction(overloads=overloads):
+                    combined = OverloadedFunction(overloads=overloads + [member_type])
+                case _:
+                    combined = OverloadedFunction(overloads=[current, member_type])
+            members[member_name] = combined
+
+        else:
+            members[member_name] = member_type
+
     def define_operation(self, left: Type, operator: str, right: Type, result: Type):
         """Define an operation in the registry
 

midas/checker/types.py

@@ -69,6 +69,14 @@ class Function:
             return f"{self.name}: {self.type}{opt}"
 
 
+@dataclass(frozen=True, kw_only=True)
+class OverloadedFunction:
+    overloads: list[Type]
+
+    def __str__(self) -> str:
+        return "<overloaded function>"
+
+
 @dataclass(frozen=True, kw_only=True)
 class ComplexType:
     members: dict[str, Type]
@@ -209,6 +217,7 @@ Type = (
     | UnknownType
     | UnitType
     | Function
+    | OverloadedFunction
     | ComplexType
     | ExtensionType
     | TypeVar