Fix missing param spec argument generics, fixes #465

Author: davidhalter

crates/zuban_python/src/file/type_computation/mod.rs

@@ -2159,15 +2159,16 @@ impl<'db: 'x + 'file, 'file, 'i_s, 'c, 'x> TypeComputation<'db, 'file, 'i_s, 'c>
                     break;
                 }
                 TypeVarLike::ParamSpec(param_spec) => {
-                    given += 1;
                     if expected == 1 && slice_type.iter().count() != 1 {
+                        given += 1;
                         // PEP 612 allows us to write C[int, str] instead of C[[int, str]],
                         // because "for aesthetic purposes we allow these to be omitted".
                         let params =
                             self.calculate_simplified_param_spec_generics(&mut slice_type.iter());
                         is_single_param_spec = true;
                         GenericItem::ParamSpecArg(ParamSpecArg::new(params, None))
                     } else if let Some(spec) = type_args.next_param_spec(self, expected == 1) {
+                        given += 1;
                         GenericItem::ParamSpecArg(spec)
                     } else if let Some(default) = param_spec.default(db) {
                         resolve_default(

crates/zuban_python/tests/mypylike/tests/type-definitions.test

@@ -1232,3 +1232,11 @@ func2(Cls.IN_CLASS)  # E: Argument 1 to "func2" has incompatible type "Sentinel(
 func3(1)  # ok
 func3(MISSING)  # E: Argument 1 to "func3" has incompatible type "Sentinel('<MISSING>')"; expected "int | Sentinel('Cls.IN_CLASS')"
 func3(Cls.IN_CLASS)  # ok
+
+[case no_crash_on_type_with_missing_param_spec_argument]
+# From GH #465
+class Base[T, **P]:
+    def m(self, *args: P.args, **kwargs: P.kwargs) -> T: ...
+
+x: Base[int]   # E: "Base" expects 2 type arguments, but 1 given
+x.m            # Should not cause problems