Fix descriptor ParamSpec specialization

[Bill Schnurr (bschnurr)]

Description

Preserve descriptor __get__ specialization when a reused class-level ParamSpec appears inside Concatenate, so bound methods retain their callable shape instead of degrading to (...) -> bool.

How you figured out what to do

I traced descriptor binding in typeEvaluator.ts and compared reused, fresh, inherited, and nested ParamSpec cases. The failure occurred when __get__ needed to solve the class ParamSpec from the concrete descriptor instance after an early specialization had already lost that information.

Implementation

Add a deferred __get__ binding path when the descriptor class has class ParamSpecs embedded in a nontrivial Concatenate. Bind the unspecialized method after solving self from the concrete descriptor instance.

Screenshots or GIFs are not applicable because this change affects analyzer or language-service behavior and has no visual UI.

Testing

Added descriptor5.py and its evaluator test covering reused, fresh, inherited, nested, and single-signature wrappers, plus incompatible-receiver and non-descriptor fallback behavior. The evaluator regression suite passed with no errors.

Addresses

Fixes #11558

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

sympy (https://github.com/sympy/sympy)
+   .../projects/sympy/sympy/solvers/bivariate.py:135:15 - error: Operator "-" not supported for "None" (reportOptionalOperand)
+   .../projects/sympy/sympy/solvers/bivariate.py:139:17 - error: Operator "-" not supported for type "Basic | Unknown" (reportOperatorIssue)
+   .../projects/sympy/sympy/solvers/bivariate.py:144:23 - error: Operator "-" not supported for "None" (reportOptionalOperand)
+   .../projects/sympy/sympy/solvers/deutils.py:234:14 - error: Operator "not in" not supported for types "str" and "Unknown | int"
+     Operator "not in" not supported for types "str" and "int" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:423:38 - error: Argument of type "int | Expr" cannot be assigned to parameter "expr" of type "Expr" in function "make_args"
+   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:423:38 - error: Argument of type "Unknown | Expr | Literal[0]" cannot be assigned to parameter "expr" of type "Expr" in function "make_args"
-     Type "int | Expr" is not assignable to type "Expr"
+     Type "Unknown | Expr | Literal[0]" is not assignable to type "Expr"
-       "int" is not assignable to "Expr" (reportArgumentType)
+       "Literal[0]" is not assignable to "Expr" (reportArgumentType)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:504:19 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:505:19 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:506:19 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:569:42 - error: Operator "*" not supported for types "int" and "Unknown | Basic"
-     Operator "*" not supported for types "int" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:569:50 - error: Operator "*" not supported for types "Expr" and "Unknown | Basic"
-     Operator "*" not supported for types "Expr" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:725:42 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:735:19 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:736:19 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:737:19 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:814:47 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:841:26 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:842:22 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:843:36 - error: Operator "*" not supported for types "int" and "Unknown | Basic"
-     Operator "*" not supported for types "int" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:843:42 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:843:51 - error: Operator "*" not supported for types "int" and "Unknown | Basic"
-     Operator "*" not supported for types "int" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:843:57 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:843:66 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:845:53 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:854:18 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:856:22 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:865:22 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:865:36 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:867:27 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:868:27 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:869:27 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:870:27 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:871:27 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:872:27 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:876:24 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:877:24 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:878:24 - error: Operator "**" not supported for types "Unknown | Basic" and "Literal[2]"
-     Operator "**" not supported for types "Basic" and "Literal[2]" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:879:24 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:880:24 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:881:24 - error: Operator "*" not supported for types "Unknown | Basic" and "Unknown | Basic"
-     Operator "*" not supported for types "Basic" and "Basic" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:888:37 - error: Operator "*" not supported for types "int" and "Unknown | None"
-     Operator "*" not supported for types "int" and "None" (reportOperatorIssue)
-   .../projects/sympy/sympy/solvers/diophantine/diophantine.py:888:45 - error: Operator "*" not supported for types "int" and "Unknown | None"
-     Operator "*" not supported for types "int" and "None" (reportOperatorIssue)

... (truncated 1927 lines) ...