imprv: generate: Hint callbacks

tools/generate.py

@@ -292,9 +292,12 @@ def _type_to_python(
             else:
                 return_type = f"Tuple[{', '.join(return_args)}]"
 
-            # FIXME, how to express Callable with variable arguments?
             if (len(names) > 0 and names[-1].startswith("*")) or varargs:
-                return f"Callable[..., {return_type}]"
+                args = args[:-1]  # Closure data is always the last argument
+                if len(args) > 0:
+                    return f"Callable[Concatenate[{', '.join(args)}, _VarArgs], {return_type}]"
+                else:
+                    return f"Callable[Concatenate[_VarArgs], {return_type}]"
             else:
                 return f"Callable[[{', '.join(args)}], {return_type}]"
         else:
@@ -326,9 +329,25 @@ def _build(parent: ObjectT, namespace: str, overrides: dict[str, str]) -> str:
     ns = set()
     ret = _gi_build_stub(parent, namespace, dir(parent), ns, overrides, None, "")
 
-    typings = "from typing import Any, Callable, Literal, Optional, Tuple, Type, TypeVar, Sequence"
+    typings_list = [
+        "Any",
+        "Callable",
+        "Literal",
+        "Optional",
+        "Tuple",
+        "Type",
+        "TypeVar",
+        "Sequence",
+    ]
+
+    typing_extensions_list = ["Concatenate", "ParamSpec"]
+
+    typings = f"from typing import {' ,'.join(typings_list)}"
+    typing_extensions = (
+        f"from typing_extensions import {' ,'.join(typing_extensions_list)}"
+    )
 
-    typevars: list[str] = []
+    typevars: list[str] = ["_VarArgs = ParamSpec('_VarArgs')"]
     imports: list[str] = []
     if "cairo" in ns:
         imports = ["import cairo"]
@@ -340,6 +359,8 @@ def _build(parent: ObjectT, namespace: str, overrides: dict[str, str]) -> str:
     return (
         typings
         + "\n\n"
+        + typing_extensions
+        + "\n\n"
         + "\n".join(imports)
         + "\n"
         + "\n".join(typevars)