Add check that type is unboxed in annotation result

trans/transpiler/phases/typing/common.py

@@ -4,7 +4,7 @@ from typing import Dict, Optional
 
 from transpiler.phases.typing.annotations import TypeAnnotationVisitor
 from transpiler.phases.typing.scope import Scope, ScopeKind, VarDecl
-from transpiler.phases.typing.types import BaseType, TypeVariable, TY_NONE
+from transpiler.phases.typing.types import BaseType, TypeVariable, TY_NONE, TypeType
 from transpiler.phases.utils import NodeVisitorSeq
 
 PRELUDE = Scope.make_global()
@@ -19,7 +19,9 @@ class ScoperVisitor(NodeVisitorSeq):
         return TypeAnnotationVisitor(self.scope, self.cur_class)
 
     def visit_annotation(self, expr: Optional[ast.expr]) -> BaseType:
-        return self.anno().visit(expr) if expr else TypeVariable()
+        res = self.anno().visit(expr) if expr else TypeVariable()
+        assert not isinstance(res, TypeType)
+        return res
 
     def visit_block(self, block: list[ast.AST]):
         from transpiler.phases.typing.block import ScoperBlockVisitor
@@ -34,3 +36,4 @@ class ScoperVisitor(NodeVisitorSeq):
                 b.decls = decls
             if not node.inner_scope.has_return:
                 rtype.unify(TY_NONE)
+