fix constrained typevar decorators #1
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When TypeVars have value restrictions (e.g., TypeVar("T", str, bytes)),
mypy expands them into concrete variants for type checking. However,
after checking, the function type was left as the last expanded variant
rather than the original polymorphic signature.
This commit preserves the original generic signature after checking
functions with constrained TypeVars.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
When a decorator with constrained TypeVars is applied to a function with matching constrained TypeVars, the decorator's TypeVars need to be matched with the function's TypeVars to preserve the polymorphic signature. This change: - Adds TypeVar matching logic in visit_decorator_inner that maps decorator TypeVars to function TypeVars with matching constraints - Preserves constrained TypeVars through infer_function_type_arguments by detecting matching TypeVars and applying polymorphic inference - Adds helper methods _finalize_poly_result and _build_typevar_substitution_map to handle the polymorphic result Fixes cases where decorated functions with constrained TypeVars would incorrectly collapse to concrete types instead of maintaining their polymorphic signatures. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
When an overloaded decorator is applied to a function with constrained TypeVars, the function is expanded into its constraint variants, each is matched against the appropriate overload, and the results are combined into an Overloaded return type. This change adds: - is_overload_decorator_constrained_call: detects when an overloaded decorator is applied to a constrained TypeVar function - has_constrained_typevars: helper to check for constrained TypeVars - handle_overload_decorator_constrained_call: expands and matches variants This is the reverse case of is_generic_decorator_overload_call, which handles a generic decorator applied to an overloaded function. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
When a function has both constrained TypeVars and @types.coroutine or @asyncio.coroutine decorator, the coroutine's AwaitableGenerator return type wrapper was being lost during signature restoration. This change applies the AwaitableGenerator transformation to the restored polymorphic signature, preserving both the polymorphism and the coroutine wrapper. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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