feat(parser): add extension type and rename properties

gen/midas.py

@@ -30,7 +30,7 @@ class TypeStmt:
     type: Type
 
 
-class PropertyStmt:
+class MemberStmt:
     name: Token
     type: Type
 
@@ -118,7 +118,12 @@ class ConstraintType:
 
 
 class ComplexType:
-    properties: list[PropertyStmt]
+    members: list[MemberStmt]
+
+
+class ExtensionType:
+    base: Type
+    extension: ComplexType
 
 
 class FunctionType:

midas/ast/midas.py

@@ -38,7 +38,7 @@ class Stmt(ABC):
         def visit_type_stmt(self, stmt: TypeStmt) -> T: ...
 
         @abstractmethod
-        def visit_property_stmt(self, stmt: PropertyStmt) -> T: ...
+        def visit_member_stmt(self, stmt: MemberStmt) -> T: ...
 
         @abstractmethod
         def visit_extend_stmt(self, stmt: ExtendStmt) -> T: ...
@@ -61,12 +61,12 @@ class TypeStmt(Stmt):
 
 
 @dataclass(frozen=True)
-class PropertyStmt(Stmt):
+class MemberStmt(Stmt):
     name: Token
     type: Type
 
     def accept(self, visitor: Stmt.Visitor[T]) -> T:
-        return visitor.visit_property_stmt(self)
+        return visitor.visit_member_stmt(self)
 
 
 @dataclass(frozen=True)
@@ -233,6 +233,9 @@ class Type(ABC):
         @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: ...
 
@@ -265,12 +268,21 @@ class ConstraintType(Type):
 
 @dataclass(frozen=True)
 class ComplexType(Type):
-    properties: list[PropertyStmt]
+    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):
     pos_args: list[Argument]

midas/ast/printer.py

@@ -111,8 +111,8 @@ class MidasAstPrinter(
             self._write_line(f'name: "{param.name.lexeme}"')
             self._write_optional_child("bound", param.bound, last=True)
 
-    def visit_property_stmt(self, stmt: m.PropertyStmt):
-        self._write_line("PropertyStmt")
+    def visit_member_stmt(self, stmt: m.MemberStmt):
+        self._write_line("MemberStmt")
         with self._child_level():
             self._write_line(f'name: "{stmt.name.lexeme}"')
             self._write_line("type", last=True)
@@ -262,13 +262,23 @@ class MidasAstPrinter(
     def visit_complex_type(self, type: m.ComplexType) -> None:
         self._write_line("ComplexType")
         with self._child_level():
-            self._write_line("properties", last=True)
+            self._write_line("members", last=True)
             with self._child_level():
-                for i, prop in enumerate(type.properties):
+                for i, member in enumerate(type.members):
                     self._idx = i
-                    if i == len(type.properties) - 1:
+                    if i == len(type.members) - 1:
                         self._mark_last()
-                    prop.accept(self)
+                    member.accept(self)
+
+    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")
@@ -332,7 +342,7 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str], m.Type.Visitor[str]
             res += "<:" + param.bound.accept(self)
         return res
 
-    def visit_property_stmt(self, stmt: m.PropertyStmt):
+    def visit_member_stmt(self, stmt: m.MemberStmt):
         res: str = f"{stmt.name.lexeme}: {stmt.type.accept(self)}"
         return self.indented(res)
 
@@ -411,16 +421,19 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str], m.Type.Visitor[str]
     def visit_complex_type(self, type: m.ComplexType) -> str:
         res: str = "{\n"
         self.level += 1
-        for prop in type.properties:
-            res += prop.accept(self)
+        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:
         pos_args: list[str] = [self._print_arg(arg) for arg in type.pos_args]
-        kw_args: list[str] = [self._print_arg(arg) for arg in type.pos_args]
+        kw_args: list[str] = [self._print_arg(arg) for arg in type.kw_args]
         args: list[str] = pos_args
 
         if len(pos_args) != 0:
@@ -429,7 +442,7 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str], m.Type.Visitor[str]
             args.append("*")
         args += kw_args
 
-        return f"({', '.join(args)}) -> {type.returns.accept(self)}"
+        return f"fn ({', '.join(args)}) -> {type.returns.accept(self)}"
 
     def _print_arg(self, arg: m.FunctionType.Argument) -> str:
         res: str = ""