interpreterbase: Use explicit `TypeAlias` annotation to allow recursive types

And fix all of the issues that pop up once we remove the use of `Any`,
which hides so many problems.

mesonbuild/interpreterbase/baseobjects.py

@@ -15,7 +15,7 @@ from abc import ABCMeta
 from contextlib import AbstractContextManager
 
 if T.TYPE_CHECKING:
-    from typing_extensions import Protocol
+    from typing_extensions import Protocol, TypeAlias
 
     # Object holders need the actual interpreter
     from ..interpreter import Interpreter
@@ -28,8 +28,8 @@ if T.TYPE_CHECKING:
 
 TV_func = T.TypeVar('TV_func', bound=T.Callable[..., T.Any])
 
-TYPE_elementary = T.Union[str, int, bool, T.List[T.Any], T.Dict[str, T.Any]]
-TYPE_var = T.Union[TYPE_elementary, HoldableObject, 'MesonInterpreterObject']
+TYPE_elementary: TypeAlias = T.Union[str, int, bool, T.Sequence['TYPE_elementary'], T.Dict[str, 'TYPE_elementary']]
+TYPE_var: TypeAlias = T.Union[TYPE_elementary, HoldableObject, 'MesonInterpreterObject', T.Sequence['TYPE_var'], T.Dict[str, 'TYPE_var']]
 TYPE_nvar = T.Union[TYPE_var, mparser.BaseNode]
 TYPE_kwargs = T.Dict[str, TYPE_var]
 TYPE_nkwargs = T.Dict[str, TYPE_nvar]
@@ -122,7 +122,7 @@ class MutableInterpreterObject:
     ''' Dummy class to mark the object type as mutable '''
 
 HoldableTypes = (HoldableObject, int, bool, str, list, dict)
-TYPE_HoldableTypes = T.Union[TYPE_elementary, HoldableObject]
+TYPE_HoldableTypes = T.Union[TYPE_var, HoldableObject]
 InterpreterObjectTypeVar = T.TypeVar('InterpreterObjectTypeVar', bound=TYPE_HoldableTypes)
 
 class ObjectHolder(InterpreterObject, T.Generic[InterpreterObjectTypeVar]):