diff --git a/gen/midas.py b/gen/midas.py
index fb90199..423d16b 100644
--- a/gen/midas.py
+++ b/gen/midas.py
@@ -136,15 +136,6 @@ class ConstraintType:
     constraint: Expr
 
 
-class ComplexType:
-    members: list[MemberStmt]
-
-
-class ExtensionType:
-    base: Type
-    extension: ComplexType
-
-
 class FunctionType:
     params: ParamSpec
     returns: Type
diff --git a/midas/ast/midas.py b/midas/ast/midas.py
index eae434a..2a822e5 100644
--- a/midas/ast/midas.py
+++ b/midas/ast/midas.py
@@ -256,12 +256,6 @@ class Type(ABC):
         @abstractmethod
         def visit_constraint_type(self, type: ConstraintType) -> T: ...
 
-        @abstractmethod
-        def visit_complex_type(self, type: ComplexType) -> T: ...
-
-        @abstractmethod
-        def visit_extension_type(self, type: ExtensionType) -> T: ...
-
         @abstractmethod
         def visit_function_type(self, type: FunctionType) -> T: ...
 
@@ -295,23 +289,6 @@ class ConstraintType(Type):
         return visitor.visit_constraint_type(self)
 
 
-@dataclass(frozen=True)
-class ComplexType(Type):
-    members: list[MemberStmt]
-
-    def accept(self, visitor: Type.Visitor[T]) -> T:
-        return visitor.visit_complex_type(self)
-
-
-@dataclass(frozen=True)
-class ExtensionType(Type):
-    base: Type
-    extension: ComplexType
-
-    def accept(self, visitor: Type.Visitor[T]) -> T:
-        return visitor.visit_extension_type(self)
-
-
 @dataclass(frozen=True)
 class FunctionType(Type):
     params: ParamSpec
diff --git a/midas/ast/printer/midas.py b/midas/ast/printer/midas.py
index cbb62d7..56d7ce8 100644
--- a/midas/ast/printer/midas.py
+++ b/midas/ast/printer/midas.py
@@ -124,19 +124,6 @@ class MidasPrinter(
         res += " where " + type.constraint.accept(self)
         return res
 
-    def visit_complex_type(self, type: m.ComplexType) -> str:
-        res: str = "{\n"
-        self.level += 1
-        for member in type.members:
-            res += member.accept(self)
-            res += "\n"
-        self.level -= 1
-        res += self.indented("}")
-        return res
-
-    def visit_extension_type(self, type: m.ExtensionType) -> str:
-        return f"{type.base.accept(self)} & {type.extension.accept(self)}"
-
     def visit_function_type(self, type: m.FunctionType) -> str:
         spec: str = self._visit_param_spec(type.params)
         return f"fn {spec} -> {type.returns.accept(self)}"
diff --git a/midas/ast/printer/midas_ast.py b/midas/ast/printer/midas_ast.py
index 69a0b16..d2e5daf 100644
--- a/midas/ast/printer/midas_ast.py
+++ b/midas/ast/printer/midas_ast.py
@@ -177,21 +177,6 @@ class MidasAstPrinter(
             with self._child_level(single=True):
                 type.constraint.accept(self)
 
-    def visit_complex_type(self, type: m.ComplexType) -> None:
-        self._write_line("ComplexType")
-        with self._child_level():
-            self._write_sequence("members", type.members, last=True)
-
-    def visit_extension_type(self, type: m.ExtensionType) -> None:
-        self._write_line("ExtensionType")
-        with self._child_level():
-            self._write_line("base")
-            with self._child_level(single=True):
-                type.base.accept(self)
-            self._write_line("extension", last=True)
-            with self._child_level(single=True):
-                type.extension.accept(self)
-
     def visit_function_type(self, type: m.FunctionType) -> None:
         self._write_line("FunctionType")
         with self._child_level():
diff --git a/midas/checker/midas.py b/midas/checker/midas.py
index e8cf791..02eb547 100644
--- a/midas/checker/midas.py
+++ b/midas/checker/midas.py
@@ -13,11 +13,9 @@ from midas.checker.registry import TypesRegistry
 from midas.checker.reporter import FileReporter, Reporter
 from midas.checker.types import (
     ColumnType,
-    ComplexType,
     ConstraintType,
     DataFrameType,
     DerivedType,
-    ExtensionType,
     Function,
     GenericType,
     ParamSpec,
@@ -422,19 +420,6 @@ class MidasTyper(m.Stmt.Visitor[None], m.Expr.Visitor[Type], m.Type.Visitor[Type
             constraint=type.constraint,
         )
 
-    def visit_complex_type(self, type: m.ComplexType) -> ComplexType:
-        return ComplexType(
-            members={
-                member.name.lexeme: member.type.accept(self) for member in type.members
-            }
-        )
-
-    def visit_extension_type(self, type: m.ExtensionType) -> Type:
-        return ExtensionType(
-            base=type.base.accept(self),
-            extension=self.visit_complex_type(type.extension),
-        )
-
     def visit_function_type(self, type: m.FunctionType) -> Type:
         return Function(
             params=self._visit_param_spec(type.params),
diff --git a/midas/checker/registry.py b/midas/checker/registry.py
index c30c5e4..0c97074 100644
--- a/midas/checker/registry.py
+++ b/midas/checker/registry.py
@@ -8,11 +8,9 @@ from midas.checker.types import (
     AppliedType,
     BaseType,
     ColumnType,
-    ComplexType,
     ConstraintType,
     DataFrameType,
     DerivedType,
-    ExtensionType,
     Function,
     GenericType,
     OverloadedFunction,
@@ -202,14 +200,6 @@ class TypesRegistry:
             case (BaseType(name=name1), BaseType(name=name2)):
                 return self.is_builtin_subtype(name1, name2)
 
-            case (ComplexType(properties=props1), ComplexType(properties=props2)):
-                for k, t in props2.items():
-                    if k not in props1:
-                        return False
-                    if not self.is_subtype(props1[k], t):
-                        return False
-                return True
-
             case (DataFrameType(columns=columns1), DataFrameType(columns=columns2)):
                 # TODO: check order?
                 by_name1: dict[str, DataFrameType.Column] = {
@@ -506,20 +496,6 @@ class TypesRegistry:
                     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 ConstraintType(type=base):
                 return self.lookup_member(base, member_name)
 
diff --git a/midas/checker/types.py b/midas/checker/types.py
index 5b043bc..ae56374 100644
--- a/midas/checker/types.py
+++ b/midas/checker/types.py
@@ -113,28 +113,6 @@ class OverloadedFunction:
         return "<overloaded function>"
 
 
-@dataclass(frozen=True, kw_only=True)
-class ComplexType:
-    """A type with inline members"""
-
-    members: dict[str, Type]
-
-    def __str__(self) -> str:
-        props: list[str] = [f"{name}: {type}" for name, type in self.members.items()]
-        return f"{{{', '.join(props)}}}"
-
-
-@dataclass(frozen=True, kw_only=True)
-class ExtensionType:
-    """An extension of a type, adding members through a `ComplexType`"""
-
-    base: Type
-    extension: ComplexType
-
-    def __str__(self) -> str:
-        return f"{self.base} & {self.extension}"
-
-
 class Variance(StrEnum):
     """The variance of a :class:`TypeVar`"""
 
@@ -323,24 +301,6 @@ def substitute_typevars(type: Type, substitutions: dict[str, Type]) -> Type:
                 ]
             )
 
-        case ComplexType(members=members):
-            members2: dict[str, Type] = {
-                name: substitute_typevars(prop, substitutions)
-                for name, prop in members.items()
-            }
-            return ComplexType(members=members2)
-
-        case ExtensionType(base=base, extension=ComplexType(members=members)):
-            return ExtensionType(
-                base=substitute_typevars(base, substitutions),
-                extension=ComplexType(
-                    members={
-                        name: substitute_typevars(prop, substitutions)
-                        for name, prop in members.items()
-                    }
-                ),
-            )
-
         case AppliedType(name=name, args=args, body=body):
             return AppliedType(
                 name=name,
@@ -468,9 +428,6 @@ def to_annotation(type: Type) -> str:
         case OverloadedFunction():
             return "Callable"
 
-        case ComplexType() | ExtensionType():
-            raise NotImplementedError
-
         case TypeVar(name=name):
             return name
 
@@ -519,8 +476,6 @@ Type = (
     | UnitType
     | Function
     | OverloadedFunction
-    | ComplexType
-    | ExtensionType
     | TypeVar
     | GenericType
     | AppliedType
diff --git a/midas/cli/highlighter.py b/midas/cli/highlighter.py
index 15f3251..2db4637 100644
--- a/midas/cli/highlighter.py
+++ b/midas/cli/highlighter.py
@@ -338,21 +338,11 @@ class MidasHighlighter(
         type.type.accept(self)
         type.constraint.accept(self)
 
-    def visit_complex_type(self, type: m.ComplexType) -> None:
-        self.wrap(type, "complex-type")
-        for member in type.members:
-            member.accept(self)
-
     def visit_function_type(self, type: m.FunctionType) -> None:
         self.wrap(type, "function")
         self._visit_param_spec(type.params)
         type.returns.accept(self)
 
-    def visit_extension_type(self, type: m.ExtensionType) -> None:
-        self.wrap(type, "extension")
-        type.base.accept(self)
-        type.extension.accept(self)
-
     def _visit_param_spec(self, spec: m.ParamSpec) -> None:
         for param in spec.pos + spec.mixed + spec.kw:
             param.type.accept(self)
diff --git a/midas/cli/hl_midas.css b/midas/cli/hl_midas.css
index fabb84e..3580132 100644
--- a/midas/cli/hl_midas.css
+++ b/midas/cli/hl_midas.css
@@ -7,8 +7,7 @@ span {
 
     &.named-type,
     &.generic-type,
-    &.constraint-type,
-    &.complex-type {
+    &.constraint-type {
         --col: 150, 150, 150;
     }
 
diff --git a/midas/generator/generator.py b/midas/generator/generator.py
index 35634a5..18885a4 100644
--- a/midas/generator/generator.py
+++ b/midas/generator/generator.py
@@ -16,11 +16,9 @@ from midas.checker.types import (
     BaseType,
     ColumnGroupBy,
     ColumnType,
-    ComplexType,
     ConstraintType,
     DataFrameType,
     DerivedType,
-    ExtensionType,
     FrameGroupBy,
     Function,
     GenericType,
@@ -675,8 +673,6 @@ class Generator(p.Stmt.Visitor[ast.stmt], p.Expr.Visitor[ast.expr]):
             case (
                 Function()
                 | OverloadedFunction()
-                | ComplexType()
-                | ExtensionType()
                 | GenericType()
                 | FrameGroupBy()
                 | ColumnGroupBy()
diff --git a/midas/generator/stubs.py b/midas/generator/stubs.py
index f185f97..b228916 100644
--- a/midas/generator/stubs.py
+++ b/midas/generator/stubs.py
@@ -8,11 +8,9 @@ from midas.checker.types import (
     BaseType,
     ColumnGroupBy,
     ColumnType,
-    ComplexType,
     ConstraintType,
     DataFrameType,
     DerivedType,
-    ExtensionType,
     FrameGroupBy,
     Function,
     GenericType,
@@ -269,14 +267,6 @@ class StubsGenerator:
                     right=self.dump_type(overloads[-1]),
                 )
 
-            case ComplexType():
-                name: str = self.new_stub_name()
-                self.generate_stub(name, type)
-                return ast.Name(id=name)
-
-            case ExtensionType():
-                raise NotImplementedError
-
             case TypeVar():
                 return ast.Name(id=type.name)
 
diff --git a/midas/parser/midas.py b/midas/parser/midas.py
index 6678dbc..fef0e97 100644
--- a/midas/parser/midas.py
+++ b/midas/parser/midas.py
@@ -5,11 +5,9 @@ from midas.ast.midas import (
     AliasStmt,
     BinaryExpr,
     CallExpr,
-    ComplexType,
     ConstraintType,
     Expr,
     ExtendStmt,
-    ExtensionType,
     FrameType,
     FunctionType,
     GenericType,
@@ -187,19 +185,9 @@ class MidasParser(Parser[list[Stmt]]):
         Returns:
             TypeExpr: the parsed type expression
         """
-        base: Type
         if self.match(TokenType.FUNC):
-            base = self.function()
-        else:
-            base = self.constraint_type()
-        if self.match(TokenType.AND):
-            extension: ComplexType = self.complex_type()
-            return ExtensionType(
-                location=Location.span(base.location, extension.location),
-                base=base,
-                extension=extension,
-            )
-        return base
+            return self.function()
+        return self.constraint_type()
 
     def constraint_type(self) -> Type:
         """Parse a constraint type expression
@@ -235,9 +223,6 @@ class MidasParser(Parser[list[Stmt]]):
             self.consume(TokenType.RIGHT_PAREN, "Unclosed parenthesis")
             return type
 
-        if self.check(TokenType.LEFT_BRACE):
-            return self.complex_type()
-
         return self.generic_type()
 
     def generic_type(self) -> Type:
@@ -295,34 +280,6 @@ class MidasParser(Parser[list[Stmt]]):
             name=name,
         )
 
-    def complex_type(self) -> ComplexType:
-        """Parse a complex type expression
-
-        A complex type consists of zero or more member statements enclosed in
-        curly braces
-
-        Returns:
-            ComplexType: the parsed complex type expression
-        """
-        left: Token = self.consume(
-            TokenType.LEFT_BRACE, "Expected '{' to start type body"
-        )
-        members: list[MemberStmt] = []
-        # TODO: add keyword to differentiate properties and methods,
-        # and allow multiple methods with the same name but not properties
-        names: set[str] = set()
-        while not self.check(TokenType.RIGHT_BRACE) and not self.is_at_end():
-            member: MemberStmt = self.member_stmt()
-            # if member.name.lexeme in names:
-            #    raise self.error(member.name, "Duplicate property")
-            # names.add(member.name.lexeme)
-            members.append(member)
-        right: Token = self.consume(TokenType.RIGHT_BRACE, "Unclosed type body")
-        return ComplexType(
-            location=left.location_to(right),
-            members=members,
-        )
-
     def frame_type(self) -> FrameType:
         """Parse a frame type expression
 
diff --git a/syntax/midas.ebnf b/syntax/midas.ebnf
index a2bf9de..1caa366 100644
--- a/syntax/midas.ebnf
+++ b/syntax/midas.ebnf
@@ -66,15 +66,13 @@ Params ::= (
 )
 ParamSpec ::= "(" Params? ")"
 
-TypeProperty ::= Identifier ":" Type
-ComplexType ::= "{" TypeProperty* "}"
 NamedType ::= Identifier
 TypeArgs ::= "[" (Type ("," Type)*)? "]"
 FrameColumn ::= TOKEN ":" Type
 FrameSchema ::= "[" (FrameColumn ("," FrameColumn)*)? "]"
 GenericType ::= "Frame" FrameSchema | NamedType TypeArgs?
 GroupedType ::= "(" Type ")"
-BaseType ::= GroupedType | ComplexType | GenericType
+BaseType ::= GroupedType | GenericType
 ConstraintType ::= BaseType ("where" Constraint)?
 FuncType ::= "fn" ParamSpec "->" Type
 Type ::= ConstraintType
diff --git a/syntax/midas.typ b/syntax/midas.typ
index 736d0a3..9d8d805 100644
--- a/syntax/midas.typ
+++ b/syntax/midas.typ
@@ -72,14 +72,6 @@ svg.railroad .terminal rect {
 {[`template` "[" <!, 'template-param'*","> "]"]}
 ```
 
-#let type-property = ```
-{[`type-property` 'identifier' ":" 'type']}
-```
-
-#let complex-type = ```
-{[`complex-type` "{" <!, 'type-property'*!> "}"]}
-```
-
 #let named-type = ```
 {[`named-type` 'identifier']}
 ```
@@ -101,7 +93,7 @@ svg.railroad .terminal rect {
 ```
 
 #let base-type = ```
-{[`base-type` <'grouped-type', 'complex-type', 'generic-type'>]}
+{[`base-type` <'grouped-type', 'generic-type'>]}
 ```
 
 #let constraint-type = ```
@@ -169,7 +161,6 @@ svg.railroad .terminal rect {
   template-param: template-param,
   template: template,
   type-property: type-property,
-  complex-type: complex-type,
   named-type: named-type,
   type-args: type-args,
   generic-type: generic-type,
@@ -196,7 +187,6 @@ svg.railroad .terminal rect {
   "template",
   "type-property",
   "call-args",
-  "complex-type",
   "type-args",
   "named-type",
   "grouped-type",
diff --git a/tests/cases/checker/09_frame_ops.py b/tests/cases/checker/09_frame_ops.py
index 6d478f6..908f4ba 100644
--- a/tests/cases/checker/09_frame_ops.py
+++ b/tests/cases/checker/09_frame_ops.py
@@ -1,8 +1,8 @@
 # type: ignore
 # ruff: disable [F821]
 
-df1: Frame[a:int, b:float]
-df2: Frame[a:int, b:float]
+df1: Frame[i:int, a:int, b:float]
+df2: Frame[i:int, a:int, b:float]
 
 _: Any
 
@@ -38,7 +38,7 @@ _ = df1.sum()
 _ = df1.var()
 
 # Groupby
-df_gb = df1.groupby(by="a")
+df_gb = df1.groupby(by="i")
 
 _ = df_gb.kurt()
 _ = df_gb.max()
diff --git a/tests/cases/checker/09_frame_ops.py.ref.json b/tests/cases/checker/09_frame_ops.py.ref.json
index dd689df..189640b 100644
--- a/tests/cases/checker/09_frame_ops.py.ref.json
+++ b/tests/cases/checker/09_frame_ops.py.ref.json
@@ -14,7 +14,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -23,6 +23,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -46,7 +55,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -55,6 +64,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -86,7 +104,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -95,6 +113,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -118,7 +145,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -127,6 +154,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -150,7 +186,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -159,6 +195,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -190,7 +235,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -199,6 +244,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -222,7 +276,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -231,6 +285,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -254,7 +317,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -263,6 +326,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -294,7 +366,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -303,6 +375,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -326,7 +407,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -335,6 +416,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -358,7 +448,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -367,6 +457,15 @@
           },
           {
             "index": 1,
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-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -2777,6 +3245,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -2822,7 +3299,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -2831,6 +3308,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4447,7 +4933,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4456,6 +4942,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4496,7 +4991,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4505,6 +5000,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4545,7 +5049,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4554,6 +5058,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4735,7 +5248,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4744,6 +5257,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4776,7 +5298,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4785,6 +5307,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4808,7 +5339,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4817,6 +5348,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
@@ -4849,7 +5389,7 @@
         "columns": [
           {
             "index": 0,
-            "name": "a",
+            "name": "i",
             "type": {
               "type": {
                 "name": "int"
@@ -4858,6 +5398,15 @@
           },
           {
             "index": 1,
+            "name": "a",
+            "type": {
+              "type": {
+                "name": "int"
+              }
+            }
+          },
+          {
+            "index": 2,
             "name": "b",
             "type": {
               "type": {
diff --git a/tests/cases/midas-parser/01_simple_types.midas b/tests/cases/midas-parser/01_simple_types.midas
index f0df3e2..3b982e1 100644
--- a/tests/cases/midas-parser/01_simple_types.midas
+++ b/tests/cases/midas-parser/01_simple_types.midas
@@ -9,26 +9,22 @@ type Longitude = float where (-180 <= _ <= 180)
 type Difference[T] = T
 
 // Complex custom type, containing two values accessible through properties
-type GeoLocation = {
+type GeoLocation = object
+
+extend GeoLocation {
     prop lat: Latitude
     prop lon: Longitude
 }
 
-// Define operations on our custom type
-extend GeoLocation {
-    // This type is compatible with the `-` operation with another GeoLocation
-    // i.e. you can subtract a GeoLocation from another GeoLocation, resulting
-    // in a Difference of GeoLocations
-    def __sub__: fn(GeoLocation, /) -> Difference[GeoLocation]
-}
+type GeoLocationDifference = object
 
-// For complex generics, you need to specify how the genericity the properties
-// are handled
-type Difference[GeoLocation] = {
+extend GeoLocationDifference {
     prop lat: Difference[Latitude]
     prop lon: Difference[Longitude]
 }
 
+// Define operations on our custom type
+
 // Simple operation defined on our custom types
 extend Latitude {
     def __sub__: fn(Latitude, /) -> Difference[Latitude]
@@ -38,13 +34,23 @@ extend Longitude {
     def __sub__: fn(Longitude, /) -> Difference[Longitude]
 }
 
+extend GeoLocation {
+    // This type is compatible with the `-` operation with another GeoLocation
+    // i.e. you can subtract a GeoLocation from another GeoLocation, resulting
+    // in a GeoLocationDifference
+    def __sub__: fn(GeoLocation, /) -> GeoLocationDifference
+}
+
+
 // Predefined custom predicates that can be referenced in other definitions
 predicate Positive(v: float) = v >= 0
 predicate StrictlyPositive(v: float) = v > 0
 predicate Equatorial(loc: GeoLocation) = (-10 <= loc.lat <= 10)
 predicate Arctic(loc: GeoLocation) = (loc.lat >= 66)
 
-type Person = {
+type Person = object
+
+extend Person {
     prop name: str
 
     // Property with an inline constraint
diff --git a/tests/cases/midas-parser/01_simple_types.midas.ref.json b/tests/cases/midas-parser/01_simple_types.midas.ref.json
index a49265b..62936de 100644
--- a/tests/cases/midas-parser/01_simple_types.midas.ref.json
+++ b/tests/cases/midas-parser/01_simple_types.midas.ref.json
@@ -493,8 +493,8 @@
       "column": 19
     },
     {
-      "type": "LEFT_BRACE",
-      "lexeme": "{",
+      "type": "IDENTIFIER",
+      "lexeme": "object",
       "line": 12,
       "column": 20
     },
@@ -502,620 +502,614 @@
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 12,
-      "column": 21
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
-      "line": 13,
-      "column": 1
-    },
-    {
-      "type": "PROP",
-      "lexeme": "prop",
-      "line": 13,
-      "column": 5
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 13,
-      "column": 9
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "lat",
-      "line": 13,
-      "column": 10
-    },
-    {
-      "type": "COLON",
-      "lexeme": ":",
-      "line": 13,
-      "column": 13
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 13,
-      "column": 14
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Latitude",
-      "line": 13,
-      "column": 15
+      "column": 26
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 13,
-      "column": 23
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
-      "line": 14,
       "column": 1
     },
-    {
-      "type": "PROP",
-      "lexeme": "prop",
-      "line": 14,
-      "column": 5
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 14,
-      "column": 9
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "lon",
-      "line": 14,
-      "column": 10
-    },
-    {
-      "type": "COLON",
-      "lexeme": ":",
-      "line": 14,
-      "column": 13
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 14,
-      "column": 14
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Longitude",
-      "line": 14,
-      "column": 15
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 14,
-      "column": 24
-    },
-    {
-      "type": "RIGHT_BRACE",
-      "lexeme": "}",
-      "line": 15,
-      "column": 1
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 15,
-      "column": 2
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 16,
-      "column": 1
-    },
-    {
-      "type": "COMMENT",
-      "lexeme": "// Define operations on our custom type",
-      "line": 17,
-      "column": 1
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 17,
-      "column": 40
-    },
     {
       "type": "EXTEND",
       "lexeme": "extend",
-      "line": 18,
+      "line": 14,
       "column": 1
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 18,
+      "line": 14,
       "column": 7
     },
     {
       "type": "IDENTIFIER",
       "lexeme": "GeoLocation",
-      "line": 18,
+      "line": 14,
       "column": 8
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 18,
+      "line": 14,
       "column": 19
     },
     {
       "type": "LEFT_BRACE",
       "lexeme": "{",
-      "line": 18,
+      "line": 14,
       "column": 20
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 18,
+      "line": 14,
       "column": 21
     },
     {
       "type": "WHITESPACE",
       "lexeme": "    ",
-      "line": 19,
-      "column": 1
-    },
-    {
-      "type": "COMMENT",
-      "lexeme": "// This type is compatible with the `-` operation with another GeoLocation",
-      "line": 19,
-      "column": 5
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 19,
-      "column": 79
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
-      "line": 20,
-      "column": 1
-    },
-    {
-      "type": "COMMENT",
-      "lexeme": "// i.e. you can subtract a GeoLocation from another GeoLocation, resulting",
-      "line": 20,
-      "column": 5
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 20,
-      "column": 79
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
-      "line": 21,
-      "column": 1
-    },
-    {
-      "type": "COMMENT",
-      "lexeme": "// in a Difference of GeoLocations",
-      "line": 21,
-      "column": 5
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 21,
-      "column": 39
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
-      "line": 22,
-      "column": 1
-    },
-    {
-      "type": "DEF",
-      "lexeme": "def",
-      "line": 22,
-      "column": 5
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 22,
-      "column": 8
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "__sub__",
-      "line": 22,
-      "column": 9
-    },
-    {
-      "type": "COLON",
-      "lexeme": ":",
-      "line": 22,
-      "column": 16
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 22,
-      "column": 17
-    },
-    {
-      "type": "FUNC",
-      "lexeme": "fn",
-      "line": 22,
-      "column": 18
-    },
-    {
-      "type": "LEFT_PAREN",
-      "lexeme": "(",
-      "line": 22,
-      "column": 20
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "GeoLocation",
-      "line": 22,
-      "column": 21
-    },
-    {
-      "type": "COMMA",
-      "lexeme": ",",
-      "line": 22,
-      "column": 32
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 22,
-      "column": 33
-    },
-    {
-      "type": "SLASH",
-      "lexeme": "/",
-      "line": 22,
-      "column": 34
-    },
-    {
-      "type": "RIGHT_PAREN",
-      "lexeme": ")",
-      "line": 22,
-      "column": 35
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 22,
-      "column": 36
-    },
-    {
-      "type": "ARROW",
-      "lexeme": "->",
-      "line": 22,
-      "column": 37
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 22,
-      "column": 39
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Difference",
-      "line": 22,
-      "column": 40
-    },
-    {
-      "type": "LEFT_BRACKET",
-      "lexeme": "[",
-      "line": 22,
-      "column": 50
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "GeoLocation",
-      "line": 22,
-      "column": 51
-    },
-    {
-      "type": "RIGHT_BRACKET",
-      "lexeme": "]",
-      "line": 22,
-      "column": 62
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 22,
-      "column": 63
-    },
-    {
-      "type": "RIGHT_BRACE",
-      "lexeme": "}",
-      "line": 23,
-      "column": 1
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 23,
-      "column": 2
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 24,
-      "column": 1
-    },
-    {
-      "type": "COMMENT",
-      "lexeme": "// For complex generics, you need to specify how the genericity the properties",
-      "line": 25,
-      "column": 1
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 25,
-      "column": 79
-    },
-    {
-      "type": "COMMENT",
-      "lexeme": "// are handled",
-      "line": 26,
-      "column": 1
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 26,
-      "column": 15
-    },
-    {
-      "type": "TYPE",
-      "lexeme": "type",
-      "line": 27,
-      "column": 1
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 27,
-      "column": 5
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Difference",
-      "line": 27,
-      "column": 6
-    },
-    {
-      "type": "LEFT_BRACKET",
-      "lexeme": "[",
-      "line": 27,
-      "column": 16
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "GeoLocation",
-      "line": 27,
-      "column": 17
-    },
-    {
-      "type": "RIGHT_BRACKET",
-      "lexeme": "]",
-      "line": 27,
-      "column": 28
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 27,
-      "column": 29
-    },
-    {
-      "type": "EQUAL",
-      "lexeme": "=",
-      "line": 27,
-      "column": 30
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 27,
-      "column": 31
-    },
-    {
-      "type": "LEFT_BRACE",
-      "lexeme": "{",
-      "line": 27,
-      "column": 32
-    },
-    {
-      "type": "NEWLINE",
-      "lexeme": "\n",
-      "line": 27,
-      "column": 33
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
-      "line": 28,
+      "line": 15,
       "column": 1
     },
     {
       "type": "PROP",
       "lexeme": "prop",
-      "line": 28,
+      "line": 15,
       "column": 5
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 28,
+      "line": 15,
       "column": 9
     },
     {
       "type": "IDENTIFIER",
       "lexeme": "lat",
-      "line": 28,
+      "line": 15,
       "column": 10
     },
     {
       "type": "COLON",
       "lexeme": ":",
-      "line": 28,
+      "line": 15,
       "column": 13
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 28,
+      "line": 15,
       "column": 14
     },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Difference",
-      "line": 28,
-      "column": 15
-    },
-    {
-      "type": "LEFT_BRACKET",
-      "lexeme": "[",
-      "line": 28,
-      "column": 25
-    },
     {
       "type": "IDENTIFIER",
       "lexeme": "Latitude",
-      "line": 28,
-      "column": 26
-    },
-    {
-      "type": "RIGHT_BRACKET",
-      "lexeme": "]",
-      "line": 28,
-      "column": 34
+      "line": 15,
+      "column": 15
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 28,
-      "column": 35
+      "line": 15,
+      "column": 23
     },
     {
       "type": "WHITESPACE",
       "lexeme": "    ",
-      "line": 29,
+      "line": 16,
       "column": 1
     },
     {
       "type": "PROP",
       "lexeme": "prop",
-      "line": 29,
+      "line": 16,
       "column": 5
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 29,
+      "line": 16,
       "column": 9
     },
     {
       "type": "IDENTIFIER",
       "lexeme": "lon",
-      "line": 29,
+      "line": 16,
       "column": 10
     },
     {
       "type": "COLON",
       "lexeme": ":",
-      "line": 29,
+      "line": 16,
       "column": 13
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 29,
+      "line": 16,
       "column": 14
     },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Difference",
-      "line": 29,
-      "column": 15
-    },
-    {
-      "type": "LEFT_BRACKET",
-      "lexeme": "[",
-      "line": 29,
-      "column": 25
-    },
     {
       "type": "IDENTIFIER",
       "lexeme": "Longitude",
-      "line": 29,
-      "column": 26
-    },
-    {
-      "type": "RIGHT_BRACKET",
-      "lexeme": "]",
-      "line": 29,
-      "column": 35
+      "line": 16,
+      "column": 15
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 29,
-      "column": 36
+      "line": 16,
+      "column": 24
     },
     {
       "type": "RIGHT_BRACE",
       "lexeme": "}",
-      "line": 30,
+      "line": 17,
       "column": 1
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 30,
+      "line": 17,
       "column": 2
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 31,
+      "line": 18,
       "column": 1
     },
     {
-      "type": "COMMENT",
-      "lexeme": "// Simple operation defined on our custom types",
-      "line": 32,
+      "type": "TYPE",
+      "lexeme": "type",
+      "line": 19,
+      "column": 1
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 19,
+      "column": 5
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "GeoLocationDifference",
+      "line": 19,
+      "column": 6
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 19,
+      "column": 27
+    },
+    {
+      "type": "EQUAL",
+      "lexeme": "=",
+      "line": 19,
+      "column": 28
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 19,
+      "column": 29
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "object",
+      "line": 19,
+      "column": 30
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 19,
+      "column": 36
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 20,
+      "column": 1
+    },
+    {
+      "type": "EXTEND",
+      "lexeme": "extend",
+      "line": 21,
+      "column": 1
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 21,
+      "column": 7
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "GeoLocationDifference",
+      "line": 21,
+      "column": 8
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 21,
+      "column": 29
+    },
+    {
+      "type": "LEFT_BRACE",
+      "lexeme": "{",
+      "line": 21,
+      "column": 30
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 21,
+      "column": 31
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 22,
+      "column": 1
+    },
+    {
+      "type": "PROP",
+      "lexeme": "prop",
+      "line": 22,
+      "column": 5
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 22,
+      "column": 9
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "lat",
+      "line": 22,
+      "column": 10
+    },
+    {
+      "type": "COLON",
+      "lexeme": ":",
+      "line": 22,
+      "column": 13
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 22,
+      "column": 14
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Difference",
+      "line": 22,
+      "column": 15
+    },
+    {
+      "type": "LEFT_BRACKET",
+      "lexeme": "[",
+      "line": 22,
+      "column": 25
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Latitude",
+      "line": 22,
+      "column": 26
+    },
+    {
+      "type": "RIGHT_BRACKET",
+      "lexeme": "]",
+      "line": 22,
+      "column": 34
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 22,
+      "column": 35
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 23,
+      "column": 1
+    },
+    {
+      "type": "PROP",
+      "lexeme": "prop",
+      "line": 23,
+      "column": 5
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 23,
+      "column": 9
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "lon",
+      "line": 23,
+      "column": 10
+    },
+    {
+      "type": "COLON",
+      "lexeme": ":",
+      "line": 23,
+      "column": 13
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 23,
+      "column": 14
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Difference",
+      "line": 23,
+      "column": 15
+    },
+    {
+      "type": "LEFT_BRACKET",
+      "lexeme": "[",
+      "line": 23,
+      "column": 25
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Longitude",
+      "line": 23,
+      "column": 26
+    },
+    {
+      "type": "RIGHT_BRACKET",
+      "lexeme": "]",
+      "line": 23,
+      "column": 35
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 23,
+      "column": 36
+    },
+    {
+      "type": "RIGHT_BRACE",
+      "lexeme": "}",
+      "line": 24,
       "column": 1
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 32,
+      "line": 24,
+      "column": 2
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 25,
+      "column": 1
+    },
+    {
+      "type": "COMMENT",
+      "lexeme": "// Define operations on our custom type",
+      "line": 26,
+      "column": 1
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 26,
+      "column": 40
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 27,
+      "column": 1
+    },
+    {
+      "type": "COMMENT",
+      "lexeme": "// Simple operation defined on our custom types",
+      "line": 28,
+      "column": 1
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 28,
       "column": 48
     },
+    {
+      "type": "EXTEND",
+      "lexeme": "extend",
+      "line": 29,
+      "column": 1
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 29,
+      "column": 7
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Latitude",
+      "line": 29,
+      "column": 8
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 29,
+      "column": 16
+    },
+    {
+      "type": "LEFT_BRACE",
+      "lexeme": "{",
+      "line": 29,
+      "column": 17
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 29,
+      "column": 18
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 30,
+      "column": 1
+    },
+    {
+      "type": "DEF",
+      "lexeme": "def",
+      "line": 30,
+      "column": 5
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 30,
+      "column": 8
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "__sub__",
+      "line": 30,
+      "column": 9
+    },
+    {
+      "type": "COLON",
+      "lexeme": ":",
+      "line": 30,
+      "column": 16
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 30,
+      "column": 17
+    },
+    {
+      "type": "FUNC",
+      "lexeme": "fn",
+      "line": 30,
+      "column": 18
+    },
+    {
+      "type": "LEFT_PAREN",
+      "lexeme": "(",
+      "line": 30,
+      "column": 20
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Latitude",
+      "line": 30,
+      "column": 21
+    },
+    {
+      "type": "COMMA",
+      "lexeme": ",",
+      "line": 30,
+      "column": 29
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 30,
+      "column": 30
+    },
+    {
+      "type": "SLASH",
+      "lexeme": "/",
+      "line": 30,
+      "column": 31
+    },
+    {
+      "type": "RIGHT_PAREN",
+      "lexeme": ")",
+      "line": 30,
+      "column": 32
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 30,
+      "column": 33
+    },
+    {
+      "type": "ARROW",
+      "lexeme": "->",
+      "line": 30,
+      "column": 34
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 30,
+      "column": 36
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Difference",
+      "line": 30,
+      "column": 37
+    },
+    {
+      "type": "LEFT_BRACKET",
+      "lexeme": "[",
+      "line": 30,
+      "column": 47
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Latitude",
+      "line": 30,
+      "column": 48
+    },
+    {
+      "type": "RIGHT_BRACKET",
+      "lexeme": "]",
+      "line": 30,
+      "column": 56
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 30,
+      "column": 57
+    },
+    {
+      "type": "RIGHT_BRACE",
+      "lexeme": "}",
+      "line": 31,
+      "column": 1
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 31,
+      "column": 2
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 32,
+      "column": 1
+    },
     {
       "type": "EXTEND",
       "lexeme": "extend",
@@ -1130,7 +1124,7 @@
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "Latitude",
+      "lexeme": "Longitude",
       "line": 33,
       "column": 8
     },
@@ -1138,19 +1132,19 @@
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 33,
-      "column": 16
+      "column": 17
     },
     {
       "type": "LEFT_BRACE",
       "lexeme": "{",
       "line": 33,
-      "column": 17
+      "column": 18
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 33,
-      "column": 18
+      "column": 19
     },
     {
       "type": "WHITESPACE",
@@ -1202,7 +1196,7 @@
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "Latitude",
+      "lexeme": "Longitude",
       "line": 34,
       "column": 21
     },
@@ -1210,73 +1204,73 @@
       "type": "COMMA",
       "lexeme": ",",
       "line": 34,
-      "column": 29
+      "column": 30
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 34,
-      "column": 30
+      "column": 31
     },
     {
       "type": "SLASH",
       "lexeme": "/",
       "line": 34,
-      "column": 31
+      "column": 32
     },
     {
       "type": "RIGHT_PAREN",
       "lexeme": ")",
       "line": 34,
-      "column": 32
+      "column": 33
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 34,
-      "column": 33
+      "column": 34
     },
     {
       "type": "ARROW",
       "lexeme": "->",
       "line": 34,
-      "column": 34
+      "column": 35
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 34,
-      "column": 36
+      "column": 37
     },
     {
       "type": "IDENTIFIER",
       "lexeme": "Difference",
       "line": 34,
-      "column": 37
+      "column": 38
     },
     {
       "type": "LEFT_BRACKET",
       "lexeme": "[",
       "line": 34,
-      "column": 47
+      "column": 48
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "Latitude",
+      "lexeme": "Longitude",
       "line": 34,
-      "column": 48
+      "column": 49
     },
     {
       "type": "RIGHT_BRACKET",
       "lexeme": "]",
       "line": 34,
-      "column": 56
+      "column": 58
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 34,
-      "column": 57
+      "column": 59
     },
     {
       "type": "RIGHT_BRACE",
@@ -1310,7 +1304,7 @@
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "Longitude",
+      "lexeme": "GeoLocation",
       "line": 37,
       "column": 8
     },
@@ -1318,19 +1312,19 @@
       "type": "WHITESPACE",
       "lexeme": " ",
       "line": 37,
-      "column": 17
+      "column": 19
     },
     {
       "type": "LEFT_BRACE",
       "lexeme": "{",
       "line": 37,
-      "column": 18
+      "column": 20
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 37,
-      "column": 19
+      "column": 21
     },
     {
       "type": "WHITESPACE",
@@ -1339,674 +1333,308 @@
       "column": 1
     },
     {
-      "type": "DEF",
-      "lexeme": "def",
+      "type": "COMMENT",
+      "lexeme": "// This type is compatible with the `-` operation with another GeoLocation",
       "line": 38,
       "column": 5
     },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 38,
-      "column": 8
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "__sub__",
-      "line": 38,
-      "column": 9
-    },
-    {
-      "type": "COLON",
-      "lexeme": ":",
-      "line": 38,
-      "column": 16
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 38,
-      "column": 17
-    },
-    {
-      "type": "FUNC",
-      "lexeme": "fn",
-      "line": 38,
-      "column": 18
-    },
-    {
-      "type": "LEFT_PAREN",
-      "lexeme": "(",
-      "line": 38,
-      "column": 20
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Longitude",
-      "line": 38,
-      "column": 21
-    },
-    {
-      "type": "COMMA",
-      "lexeme": ",",
-      "line": 38,
-      "column": 30
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 38,
-      "column": 31
-    },
-    {
-      "type": "SLASH",
-      "lexeme": "/",
-      "line": 38,
-      "column": 32
-    },
-    {
-      "type": "RIGHT_PAREN",
-      "lexeme": ")",
-      "line": 38,
-      "column": 33
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 38,
-      "column": 34
-    },
-    {
-      "type": "ARROW",
-      "lexeme": "->",
-      "line": 38,
-      "column": 35
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 38,
-      "column": 37
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Difference",
-      "line": 38,
-      "column": 38
-    },
-    {
-      "type": "LEFT_BRACKET",
-      "lexeme": "[",
-      "line": 38,
-      "column": 48
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "Longitude",
-      "line": 38,
-      "column": 49
-    },
-    {
-      "type": "RIGHT_BRACKET",
-      "lexeme": "]",
-      "line": 38,
-      "column": 58
-    },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 38,
-      "column": 59
+      "column": 79
     },
     {
-      "type": "RIGHT_BRACE",
-      "lexeme": "}",
+      "type": "WHITESPACE",
+      "lexeme": "    ",
       "line": 39,
       "column": 1
     },
     {
-      "type": "NEWLINE",
-      "lexeme": "\n",
+      "type": "COMMENT",
+      "lexeme": "// i.e. you can subtract a GeoLocation from another GeoLocation, resulting",
       "line": 39,
-      "column": 2
+      "column": 5
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
+      "line": 39,
+      "column": 79
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
       "line": 40,
       "column": 1
     },
     {
       "type": "COMMENT",
-      "lexeme": "// Predefined custom predicates that can be referenced in other definitions",
-      "line": 41,
-      "column": 1
+      "lexeme": "// in a GeoLocationDifference",
+      "line": 40,
+      "column": 5
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 41,
-      "column": 76
+      "line": 40,
+      "column": 34
     },
     {
-      "type": "PREDICATE",
-      "lexeme": "predicate",
-      "line": 42,
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 41,
       "column": 1
     },
+    {
+      "type": "DEF",
+      "lexeme": "def",
+      "line": 41,
+      "column": 5
+    },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 42,
-      "column": 10
+      "line": 41,
+      "column": 8
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "Positive",
-      "line": 42,
-      "column": 11
-    },
-    {
-      "type": "LEFT_PAREN",
-      "lexeme": "(",
-      "line": 42,
-      "column": 19
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "v",
-      "line": 42,
-      "column": 20
+      "lexeme": "__sub__",
+      "line": 41,
+      "column": 9
     },
     {
       "type": "COLON",
       "lexeme": ":",
-      "line": 42,
+      "line": 41,
+      "column": 16
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 41,
+      "column": 17
+    },
+    {
+      "type": "FUNC",
+      "lexeme": "fn",
+      "line": 41,
+      "column": 18
+    },
+    {
+      "type": "LEFT_PAREN",
+      "lexeme": "(",
+      "line": 41,
+      "column": 20
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "GeoLocation",
+      "line": 41,
       "column": 21
     },
     {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 42,
-      "column": 22
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "float",
-      "line": 42,
-      "column": 23
-    },
-    {
-      "type": "RIGHT_PAREN",
-      "lexeme": ")",
-      "line": 42,
-      "column": 28
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 42,
-      "column": 29
-    },
-    {
-      "type": "EQUAL",
-      "lexeme": "=",
-      "line": 42,
-      "column": 30
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 42,
-      "column": 31
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "v",
-      "line": 42,
+      "type": "COMMA",
+      "lexeme": ",",
+      "line": 41,
       "column": 32
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 42,
+      "line": 41,
       "column": 33
     },
     {
-      "type": "GREATER_EQUAL",
-      "lexeme": ">=",
-      "line": 42,
+      "type": "SLASH",
+      "lexeme": "/",
+      "line": 41,
       "column": 34
     },
+    {
+      "type": "RIGHT_PAREN",
+      "lexeme": ")",
+      "line": 41,
+      "column": 35
+    },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 42,
+      "line": 41,
       "column": 36
     },
     {
-      "type": "NUMBER",
-      "lexeme": "0",
-      "line": 42,
+      "type": "ARROW",
+      "lexeme": "->",
+      "line": 41,
       "column": 37
     },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 41,
+      "column": 39
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "GeoLocationDifference",
+      "line": 41,
+      "column": 40
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 41,
+      "column": 61
+    },
+    {
+      "type": "RIGHT_BRACE",
+      "lexeme": "}",
+      "line": 42,
+      "column": 1
+    },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 42,
-      "column": 38
+      "column": 2
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 43,
+      "column": 1
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 44,
+      "column": 1
+    },
+    {
+      "type": "COMMENT",
+      "lexeme": "// Predefined custom predicates that can be referenced in other definitions",
+      "line": 45,
+      "column": 1
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 45,
+      "column": 76
     },
     {
       "type": "PREDICATE",
       "lexeme": "predicate",
-      "line": 43,
+      "line": 46,
       "column": 1
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 43,
+      "line": 46,
       "column": 10
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "StrictlyPositive",
-      "line": 43,
+      "lexeme": "Positive",
+      "line": 46,
       "column": 11
     },
     {
       "type": "LEFT_PAREN",
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+      "type": "LEFT_PAREN",
+      "lexeme": "(",
+      "line": 49,
+      "column": 38
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "loc",
+      "line": 49,
+      "column": 39
+    },
+    {
+      "type": "DOT",
+      "lexeme": ".",
+      "line": 49,
+      "column": 42
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "lat",
+      "line": 49,
+      "column": 43
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 49,
+      "column": 46
+    },
+    {
+      "type": "GREATER_EQUAL",
+      "lexeme": ">=",
+      "line": 49,
+      "column": 47
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 49,
+      "column": 49
+    },
+    {
+      "type": "NUMBER",
+      "lexeme": "66",
+      "line": 49,
+      "column": 50
+    },
+    {
+      "type": "RIGHT_PAREN",
+      "lexeme": ")",
+      "line": 49,
+      "column": 52
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 49,
+      "column": 53
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 50,
+      "column": 1
+    },
+    {
+      "type": "TYPE",
+      "lexeme": "type",
       "line": 51,
-      "column": 48
+      "column": 1
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 51,
+      "column": 5
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Person",
+      "line": 51,
+      "column": 6
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 51,
+      "column": 12
+    },
+    {
+      "type": "EQUAL",
+      "lexeme": "=",
+      "line": 51,
+      "column": 13
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 51,
+      "column": 14
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "object",
+      "line": 51,
+      "column": 15
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 51,
-      "column": 49
+      "column": 21
     },
     {
       "type": "NEWLINE",
@@ -2281,22 +2095,40 @@
       "column": 1
     },
     {
-      "type": "WHITESPACE",
-      "lexeme": "    ",
+      "type": "EXTEND",
+      "lexeme": "extend",
       "line": 53,
       "column": 1
     },
     {
-      "type": "COMMENT",
-      "lexeme": "// Property referencing a predicate",
+      "type": "WHITESPACE",
+      "lexeme": " ",
       "line": 53,
-      "column": 5
+      "column": 7
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Person",
+      "line": 53,
+      "column": 8
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 53,
+      "column": 14
+    },
+    {
+      "type": "LEFT_BRACE",
+      "lexeme": "{",
+      "line": 53,
+      "column": 15
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 53,
-      "column": 40
+      "column": 16
     },
     {
       "type": "WHITESPACE",
@@ -2318,7 +2150,7 @@
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "height",
+      "lexeme": "name",
       "line": 54,
       "column": 10
     },
@@ -2326,49 +2158,25 @@
       "type": "COLON",
       "lexeme": ":",
       "line": 54,
+      "column": 14
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 54,
+      "column": 15
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "str",
+      "line": 54,
       "column": 16
     },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 54,
-      "column": 17
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "float",
-      "line": 54,
-      "column": 18
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 54,
-      "column": 23
-    },
-    {
-      "type": "WHERE",
-      "lexeme": "where",
-      "line": 54,
-      "column": 24
-    },
-    {
-      "type": "WHITESPACE",
-      "lexeme": " ",
-      "line": 54,
-      "column": 29
-    },
-    {
-      "type": "IDENTIFIER",
-      "lexeme": "StrictlyPositive",
-      "line": 54,
-      "column": 30
-    },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
       "line": 54,
-      "column": 46
+      "column": 19
     },
     {
       "type": "NEWLINE",
@@ -2382,64 +2190,334 @@
       "line": 56,
       "column": 1
     },
+    {
+      "type": "COMMENT",
+      "lexeme": "// Property with an inline constraint",
+      "line": 56,
+      "column": 5
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 56,
+      "column": 42
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 57,
+      "column": 1
+    },
     {
       "type": "PROP",
       "lexeme": "prop",
-      "line": 56,
+      "line": 57,
       "column": 5
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 56,
+      "line": 57,
       "column": 9
     },
     {
       "type": "IDENTIFIER",
-      "lexeme": "home",
-      "line": 56,
+      "lexeme": "age",
+      "line": 57,
       "column": 10
     },
     {
       "type": "COLON",
       "lexeme": ":",
-      "line": 56,
+      "line": 57,
+      "column": 13
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 14
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "Optional",
+      "line": 57,
+      "column": 15
+    },
+    {
+      "type": "LEFT_BRACKET",
+      "lexeme": "[",
+      "line": 57,
+      "column": 23
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "int",
+      "line": 57,
+      "column": 24
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 27
+    },
+    {
+      "type": "WHERE",
+      "lexeme": "where",
+      "line": 57,
+      "column": 28
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 33
+    },
+    {
+      "type": "LEFT_PAREN",
+      "lexeme": "(",
+      "line": 57,
+      "column": 34
+    },
+    {
+      "type": "NUMBER",
+      "lexeme": "0",
+      "line": 57,
+      "column": 35
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 36
+    },
+    {
+      "type": "LESS_EQUAL",
+      "lexeme": "<=",
+      "line": 57,
+      "column": 37
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 39
+    },
+    {
+      "type": "UNDERSCORE",
+      "lexeme": "_",
+      "line": 57,
+      "column": 40
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 41
+    },
+    {
+      "type": "LESS",
+      "lexeme": "<",
+      "line": 57,
+      "column": 42
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 57,
+      "column": 43
+    },
+    {
+      "type": "NUMBER",
+      "lexeme": "150",
+      "line": 57,
+      "column": 44
+    },
+    {
+      "type": "RIGHT_PAREN",
+      "lexeme": ")",
+      "line": 57,
+      "column": 47
+    },
+    {
+      "type": "RIGHT_BRACKET",
+      "lexeme": "]",
+      "line": 57,
+      "column": 48
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 57,
+      "column": 49
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 58,
+      "column": 1
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 59,
+      "column": 1
+    },
+    {
+      "type": "COMMENT",
+      "lexeme": "// Property referencing a predicate",
+      "line": 59,
+      "column": 5
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 59,
+      "column": 40
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 60,
+      "column": 1
+    },
+    {
+      "type": "PROP",
+      "lexeme": "prop",
+      "line": 60,
+      "column": 5
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 60,
+      "column": 9
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "height",
+      "line": 60,
+      "column": 10
+    },
+    {
+      "type": "COLON",
+      "lexeme": ":",
+      "line": 60,
+      "column": 16
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 60,
+      "column": 17
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "float",
+      "line": 60,
+      "column": 18
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 60,
+      "column": 23
+    },
+    {
+      "type": "WHERE",
+      "lexeme": "where",
+      "line": 60,
+      "column": 24
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 60,
+      "column": 29
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "StrictlyPositive",
+      "line": 60,
+      "column": 30
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 60,
+      "column": 46
+    },
+    {
+      "type": "NEWLINE",
+      "lexeme": "\n",
+      "line": 61,
+      "column": 1
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": "    ",
+      "line": 62,
+      "column": 1
+    },
+    {
+      "type": "PROP",
+      "lexeme": "prop",
+      "line": 62,
+      "column": 5
+    },
+    {
+      "type": "WHITESPACE",
+      "lexeme": " ",
+      "line": 62,
+      "column": 9
+    },
+    {
+      "type": "IDENTIFIER",
+      "lexeme": "home",
+      "line": 62,
+      "column": 10
+    },
+    {
+      "type": "COLON",
+      "lexeme": ":",
+      "line": 62,
       "column": 14
     },
     {
       "type": "WHITESPACE",
       "lexeme": " ",
-      "line": 56,
+      "line": 62,
       "column": 15
     },
     {
       "type": "IDENTIFIER",
       "lexeme": "GeoLocation",
-      "line": 56,
+      "line": 62,
       "column": 16
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 56,
+      "line": 62,
       "column": 27
     },
     {
       "type": "RIGHT_BRACE",
       "lexeme": "}",
-      "line": 57,
+      "line": 63,
       "column": 1
     },
     {
       "type": "NEWLINE",
       "lexeme": "\n",
-      "line": 57,
+      "line": 63,
       "column": 2
     },
     {
       "type": "EOF",
       "lexeme": "",
-      "line": 58,
+      "line": 64,
       "column": 1
     }
   ],
@@ -2548,27 +2626,8 @@
       "name": "GeoLocation",
       "params": [],
       "type": {
-        "_type": "ComplexType",
-        "members": [
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "lat",
-            "type": {
-              "_type": "NamedType",
-              "name": "Latitude"
-            }
-          },
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "lon",
-            "type": {
-              "_type": "NamedType",
-              "name": "Longitude"
-            }
-          }
-        ]
+        "_type": "NamedType",
+        "name": "object"
       }
     },
     {
@@ -2578,93 +2637,76 @@
       "members": [
         {
           "_type": "MemberStmt",
-          "kind": "METHOD",
-          "name": "__sub__",
+          "kind": "PROPERTY",
+          "name": "lat",
           "type": {
-            "_type": "FunctionType",
-            "params": {
-              "_type": "ParamSpec",
-              "pos": [
-                {
-                  "name": null,
-                  "type": {
-                    "_type": "NamedType",
-                    "name": "GeoLocation"
-                  },
-                  "required": true
-                }
-              ],
-              "mixed": [],
-              "kw": []
-            },
-            "returns": {
-              "_type": "GenericType",
-              "type": {
-                "_type": "NamedType",
-                "name": "Difference"
-              },
-              "args": [
-                {
-                  "_type": "NamedType",
-                  "name": "GeoLocation"
-                }
-              ]
-            }
+            "_type": "NamedType",
+            "name": "Latitude"
+          }
+        },
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "lon",
+          "type": {
+            "_type": "NamedType",
+            "name": "Longitude"
           }
         }
       ]
     },
     {
       "_type": "TypeStmt",
-      "name": "Difference",
-      "params": [
-        {
-          "name": "GeoLocation",
-          "bound": null
-        }
-      ],
+      "name": "GeoLocationDifference",
+      "params": [],
       "type": {
-        "_type": "ComplexType",
-        "members": [
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "lat",
-            "type": {
-              "_type": "GenericType",
-              "type": {
-                "_type": "NamedType",
-                "name": "Difference"
-              },
-              "args": [
-                {
-                  "_type": "NamedType",
-                  "name": "Latitude"
-                }
-              ]
-            }
-          },
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "lon",
-            "type": {
-              "_type": "GenericType",
-              "type": {
-                "_type": "NamedType",
-                "name": "Difference"
-              },
-              "args": [
-                {
-                  "_type": "NamedType",
-                  "name": "Longitude"
-                }
-              ]
-            }
-          }
-        ]
+        "_type": "NamedType",
+        "name": "object"
       }
     },
+    {
+      "_type": "ExtendStmt",
+      "name": "GeoLocationDifference",
+      "params": [],
+      "members": [
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "lat",
+          "type": {
+            "_type": "GenericType",
+            "type": {
+              "_type": "NamedType",
+              "name": "Difference"
+            },
+            "args": [
+              {
+                "_type": "NamedType",
+                "name": "Latitude"
+              }
+            ]
+          }
+        },
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "lon",
+          "type": {
+            "_type": "GenericType",
+            "type": {
+              "_type": "NamedType",
+              "name": "Difference"
+            },
+            "args": [
+              {
+                "_type": "NamedType",
+                "name": "Longitude"
+              }
+            ]
+          }
+        }
+      ]
+    },
     {
       "_type": "ExtendStmt",
       "name": "Latitude",
@@ -2751,6 +2793,40 @@
         }
       ]
     },
+    {
+      "_type": "ExtendStmt",
+      "name": "GeoLocation",
+      "params": [],
+      "members": [
+        {
+          "_type": "MemberStmt",
+          "kind": "METHOD",
+          "name": "__sub__",
+          "type": {
+            "_type": "FunctionType",
+            "params": {
+              "_type": "ParamSpec",
+              "pos": [
+                {
+                  "name": null,
+                  "type": {
+                    "_type": "NamedType",
+                    "name": "GeoLocation"
+                  },
+                  "required": true
+                }
+              ],
+              "mixed": [],
+              "kw": []
+            },
+            "returns": {
+              "_type": "NamedType",
+              "name": "GeoLocationDifference"
+            }
+          }
+        }
+      ]
+    },
     {
       "_type": "PredicateStmt",
       "name": "Positive",
@@ -2914,87 +2990,93 @@
       "name": "Person",
       "params": [],
       "type": {
-        "_type": "ComplexType",
-        "members": [
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "name",
+        "_type": "NamedType",
+        "name": "object"
+      }
+    },
+    {
+      "_type": "ExtendStmt",
+      "name": "Person",
+      "params": [],
+      "members": [
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "name",
+          "type": {
+            "_type": "NamedType",
+            "name": "str"
+          }
+        },
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "age",
+          "type": {
+            "_type": "GenericType",
             "type": {
               "_type": "NamedType",
-              "name": "str"
-            }
-          },
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "age",
-            "type": {
-              "_type": "GenericType",
-              "type": {
-                "_type": "NamedType",
-                "name": "Optional"
-              },
-              "args": [
-                {
-                  "_type": "ConstraintType",
-                  "type": {
-                    "_type": "NamedType",
-                    "name": "int"
-                  },
-                  "constraint": {
-                    "_type": "GroupingExpr",
-                    "expr": {
+              "name": "Optional"
+            },
+            "args": [
+              {
+                "_type": "ConstraintType",
+                "type": {
+                  "_type": "NamedType",
+                  "name": "int"
+                },
+                "constraint": {
+                  "_type": "GroupingExpr",
+                  "expr": {
+                    "_type": "BinaryExpr",
+                    "left": {
                       "_type": "BinaryExpr",
                       "left": {
-                        "_type": "BinaryExpr",
-                        "left": {
-                          "_type": "LiteralExpr",
-                          "value": 0
-                        },
-                        "operator": "<=",
-                        "right": {
-                          "_type": "WildcardExpr"
-                        }
-                      },
-                      "operator": "<",
-                      "right": {
                         "_type": "LiteralExpr",
-                        "value": 150
+                        "value": 0
+                      },
+                      "operator": "<=",
+                      "right": {
+                        "_type": "WildcardExpr"
                       }
+                    },
+                    "operator": "<",
+                    "right": {
+                      "_type": "LiteralExpr",
+                      "value": 150
                     }
                   }
                 }
-              ]
-            }
-          },
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "height",
-            "type": {
-              "_type": "ConstraintType",
-              "type": {
-                "_type": "NamedType",
-                "name": "float"
-              },
-              "constraint": {
-                "_type": "VariableExpr",
-                "name": "StrictlyPositive"
               }
-            }
-          },
-          {
-            "_type": "MemberStmt",
-            "kind": "PROPERTY",
-            "name": "home",
+            ]
+          }
+        },
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "height",
+          "type": {
+            "_type": "ConstraintType",
             "type": {
               "_type": "NamedType",
-              "name": "GeoLocation"
+              "name": "float"
+            },
+            "constraint": {
+              "_type": "VariableExpr",
+              "name": "StrictlyPositive"
             }
           }
-        ]
-      }
+        },
+        {
+          "_type": "MemberStmt",
+          "kind": "PROPERTY",
+          "name": "home",
+          "type": {
+            "_type": "NamedType",
+            "name": "GeoLocation"
+          }
+        }
+      ]
     }
   ],
   "errors": []
diff --git a/tests/serializer/midas.py b/tests/serializer/midas.py
index 13fcbaa..599482b 100644
--- a/tests/serializer/midas.py
+++ b/tests/serializer/midas.py
@@ -4,11 +4,9 @@ from midas.ast.midas import (
     AliasStmt,
     BinaryExpr,
     CallExpr,
-    ComplexType,
     ConstraintType,
     Expr,
     ExtendStmt,
-    ExtensionType,
     FrameType,
     FunctionType,
     GenericType,
@@ -172,12 +170,6 @@ class MidasAstJsonSerializer(
             "constraint": type.constraint.accept(self),
         }
 
-    def visit_complex_type(self, type: ComplexType) -> dict:
-        return {
-            "_type": "ComplexType",
-            "members": self._serialize_list(type.members),
-        }
-
     def visit_function_type(self, type: FunctionType) -> dict:
         return {
             "_type": "FunctionType",
@@ -200,13 +192,6 @@ class MidasAstJsonSerializer(
             "required": param.required,
         }
 
-    def visit_extension_type(self, type: ExtensionType) -> dict:
-        return {
-            "_type": "ExtensionType",
-            "base": type.base.accept(self),
-            "extension": type.extension.accept(self),
-        }
-
     def visit_frame_type(self, type: FrameType) -> dict:
         return {
             "_type": "FrameType",