feat(checker): implement lookup_member method

midas/checker/python.py

@@ -11,14 +11,11 @@ from midas.checker.registry import TypesRegistry
 from midas.checker.reporter import FileReporter, Reporter
 from midas.checker.resolver import Resolver
 from midas.checker.types import (
-    ComplexType,
-    ExtensionType,
     Function,
     Operation,
     Type,
     UnitType,
     UnknownType,
-    unfold_type,
 )
 from midas.parser.python import PythonParser
 
@@ -250,8 +247,7 @@ class PythonTyper(
                 self._assign_var(location, target, value_type)
 
             case p.GetExpr(object=object, name=name):
-                object_type: Type = self.type_of(object)
-                self._assign_attr(location, object_type, name, value_type)
+                self._assign_attr(location, object, name, value_type)
 
             case _:
                 if not isinstance(target, p.VariableExpr):
@@ -277,42 +273,18 @@ class PythonTyper(
                 )
 
     def _assign_attr(
-        self, location: Location, object: Type, name: str, value_type: Type
+        self, location: Location, object: p.Expr, name: str, value_type: Type
     ):
-        # TODO: improve recursion to have better error messages
-        base_object: Type = unfold_type(object)
-        match base_object:
-            case ComplexType(members=members):
-                if name not in members:
-                    self.reporter.error(location, f"Unknown member '{object}.{name}'")
+        object_type: Type = self.type_of(object)
+        member: Optional[Type] = self.types.lookup_member(object_type, name)
+        if member is None:
+            self.reporter.error(location, f"Unknown member '{name}' of {object_type}")
             return
-
-                member_type: Type = members[name]
-                if not self.is_subtype(value_type, member_type):
+        self.logger.debug(f"Member '{name}' of {object_type} has type {member}")
+        if not self.is_subtype(value_type, member):
             self.reporter.error(
                 location,
-                        f"Cannot assign {value_type} to member '{object}.{name}' of type {member_type}",
-                    )
-                    return
-
-            case ExtensionType(base=base, extension=ComplexType(members=members)):
-                if name in members:
-                    member_type: Type = members[name]
-                    if not self.is_subtype(value_type, member_type):
-                        self.reporter.error(
-                            location,
-                            f"Cannot assign {value_type} to member '{object}.{name}' of type {member_type}",
-                        )
-                        return
-                return self._assign_attr(location, base, name, value_type)
-
-            case UnknownType():
-                pass
-
-            case _:
-                self.reporter.error(
-                    location,
-                    f"Cannot assign {value_type} to unknown property '{object}.{name}'",
+                f"Cannot assign {value_type} to member '{object_type}.{name}' of type {member}",
             )
 
     def visit_return_stmt(self, stmt: p.ReturnStmt) -> None:
@@ -433,39 +405,15 @@ class PythonTyper(
 
     def visit_get_expr(self, expr: p.GetExpr) -> Type:
         object: Type = self.type_of(expr.object)
-        member: Optional[Type] = self._get_member(object, expr.name)
+        member: Optional[Type] = self.types.lookup_member(object, expr.name)
         if member is None:
             self.reporter.error(
-                expr.location, f"Unknown property '{expr.name}' on {object}"
+                expr.location, f"Unknown member '{expr.name}' of {object}"
             )
             return UnknownType()
-        self.logger.debug(f"Property '{expr.name}' on {object} has type {member}")
+        self.logger.debug(f"Member '{expr.name}' of {object} has type {member}")
         return member
 
-    def _get_member(self, object: Type, name: str) -> Optional[Type]:
-        base_object: Type = unfold_type(object)
-        match base_object:
-            case ComplexType(members=members):
-                if name in members:
-                    return members[name]
-                self.logger.debug(f"No property '{name}' in {base_object}")
-                return None
-
-            case ExtensionType(base=base, extension=ComplexType(members=members)):
-                if name in members:
-                    return members[name]
-                self.logger.debug(
-                    f"No property '{name}' on {base_object}, looking up in base"
-                )
-                return self._get_member(base, name)
-
-            case UnknownType():
-                return UnknownType()
-
-            case _:
-                self.logger.debug(f"Can't get property on {base_object}")
-                return UnknownType()
-
     def visit_literal_expr(self, expr: p.LiteralExpr) -> Type:
         match expr.value:
             case bool():  # Must be before int

midas/checker/registry.py

@@ -7,11 +7,13 @@ from midas.checker.types import (
     AppliedType,
     BaseType,
     ComplexType,
+    ExtensionType,
     Function,
     GenericType,
     Operation,
     OverloadedFunction,
     Type,
+    UnknownType,
     substitute_typevars,
 )
 
@@ -337,3 +339,51 @@ class TypesRegistry:
                     reduced = True
                     break
         return [types[i] for i in keep]
+
+    def lookup_member(self, type: Type, member_name: str) -> Optional[Type]:
+        match type:
+            case AliasType(name=name, type=base):
+                if name in self._members:
+                    if member_name in self._members[name]:
+                        return self._members[name][member_name]
+                return self.lookup_member(base, member_name)
+
+            case AppliedType(name=name, body=body, args=args):
+                generic: Type = self.get_type(name)
+
+                if not isinstance(generic, GenericType):
+                    raise ValueError("AppliedType not derived from a GenericType")
+
+                substitutions = {
+                    type_var.name: arg for arg, type_var in zip(args, generic.params)
+                }
+                if name in self._members:
+                    if member_name in self._members[name]:
+                        member_type: Type = self._members[name][member_name]
+                        return substitute_typevars(member_type, substitutions)
+
+                member_type2: Optional[Type] = self.lookup_member(body, member_name)
+                if member_type2 is not None:
+                    member_type2 = substitute_typevars(member_type2, substitutions)
+                return member_type2
+
+            case ComplexType(members=members):
+                if member_name in members:
+                    return members[member_name]
+                self.logger.debug(f"No member '{member_name}' in {type}")
+                return None
+
+            case ExtensionType(base=base, extension=ComplexType(members=members)):
+                if member_name in members:
+                    return members[member_name]
+                self.logger.debug(
+                    f"No member '{member_name}' on {type}, looking up in base"
+                )
+                return self.lookup_member(base, member_name)
+
+            case UnknownType():
+                return UnknownType()
+
+            case _:
+                self.logger.debug(f"Can't get member on {type}")
+                return None