[ty] support callability of bound/constrained typevars

[carljm]

Summary

Allow a typevar to be callable if it is bound to a callable type, or constrained to callable types.

I spent some time digging into why this support didn't fall out naturally, and ultimately the reason is that we look up __call__ on the meta type (since its a dunder), and our implementation of Type::to_meta_type for Type::Callable does not return a type with __call__.

A more general solution here would be to have Type::to_meta_type for Type::Callable synthesize a protocol with __call__ and return an intersection with that protocol (since for a type to be callable, we know its meta-type must have __call__). That solution could in principle also replace the special-case handling of Type::Callable itself, here in Type::bindings. But that more general approach would also be slower, and our protocol support isn't quite ready for that yet, and handling this directly in Type::bindings is really not bad.

Fixes astral-sh/ty#480

Test Plan

Added mdtests.

[github-actions]

mypy_primer results

Changes were detected when running on open source projects

pegen (https://github.com/we-like-parsers/pegen)
- error[call-non-callable] src/pegen/parser.py:32:20: Object of type `F` is not callable
- error[call-non-callable] src/pegen/parser.py:37:16: Object of type `F` is not callable
- error[call-non-callable] src/pegen/parser.py:66:20: Object of type `F` is not callable
- Found 56 diagnostics
+ Found 53 diagnostics

beartype (https://github.com/beartype/beartype)
- error[call-non-callable] beartype/_util/cache/utilcachecall.py:243:71: Object of type `CallableT` is not callable
- error[call-non-callable] beartype/_util/cache/utilcachecall.py:243:71: Object of type `CallableT` is not callable
- error[call-non-callable] beartype/_util/cache/utilcachecall.py:259:20: Object of type `CallableT` is not callable
- error[call-non-callable] beartype/_util/cache/utilcachecall.py:470:71: Object of type `CallableT` is not callable
- error[call-non-callable] beartype/_util/cache/utilcachecall.py:470:71: Object of type `CallableT` is not callable
- error[call-non-callable] beartype/_util/cache/utilcachecall.py:486:20: Object of type `CallableT` is not callable
- Found 576 diagnostics
+ Found 570 diagnostics

kopf (https://github.com/nolar/kopf)
- error[call-non-callable] kopf/_cogs/clients/auth.py:41:30: Object of type `_F` is not callable
- error[call-non-callable] kopf/_cogs/clients/auth.py:51:34: Object of type `_F` is not callable
- error[call-non-callable] kopf/_core/intents/callbacks.py:254:20: Object of type `_FnT` is not callable
- error[call-non-callable] kopf/_core/intents/callbacks.py:260:20: Object of type `_FnT` is not callable
- error[call-non-callable] kopf/_core/intents/callbacks.py:266:20: Object of type `_FnT` is not callable
- error[call-non-callable] kopf/_core/intents/callbacks.py:272:24: Object of type `_FnT` is not callable
- error[call-non-callable] kopf/_kits/webhacks.py:86:24: Object of type `_ServerFn` is not callable
- Found 163 diagnostics
+ Found 156 diagnostics

check-jsonschema (https://github.com/python-jsonschema/check-jsonschema)
- error[call-non-callable] src/check_jsonschema/cli/param_types.py:21:20: Object of type `C` is not callable
- error[call-non-callable] src/check_jsonschema/cli/param_types.py:22:16: Object of type `C` is not callable
- Found 68 diagnostics
+ Found 66 diagnostics

ignite (https://github.com/pytorch/ignite)
- error[call-non-callable] ignite/utils.py:413:20: Object of type `F` is not callable
- Found 2223 diagnostics
+ Found 2222 diagnostics

urllib3 (https://github.com/urllib3/urllib3)
- error[call-non-callable] test/__init__.py:186:20: Object of type `_TestFuncT` is not callable
- Found 443 diagnostics
+ Found 442 diagnostics

paasta (https://github.com/yelp/paasta)
- error[call-non-callable] paasta_tools/utils.py:3990:22: Object of type `_UseRequestsCacheFuncT` is not callable
- Found 943 diagnostics
+ Found 942 diagnostics

jinja (https://github.com/pallets/jinja)
- error[call-non-callable] src/jinja2/compiler.py:56:16: Object of type `F` is not callable
- error[call-non-callable] src/jinja2/runtime.py:139:16: Object of type `F` is not callable
- Found 230 diagnostics
+ Found 228 diagnostics

werkzeug (https://github.com/pallets/werkzeug)
- error[call-non-callable] src/werkzeug/datastructures/mixins.py:235:14: Object of type `F` is not callable
- error[call-non-callable] src/werkzeug/local.py:379:16: Object of type `F` is not callable
- Found 451 diagnostics
+ Found 449 diagnostics

psycopg (https://github.com/psycopg/psycopg)
- error[call-non-callable] psycopg/psycopg/pq/_debug.py:96:18: Object of type `Func` is not callable
- Found 1115 diagnostics
+ Found 1114 diagnostics

vision (https://github.com/pytorch/vision)
- error[call-non-callable] torchvision/models/_utils.py:201:43: Object of type `W` is not callable
+ error[call-non-callable] torchvision/models/_utils.py:201:43: Object of type `WeightsEnum` is not callable

hydra-zen (https://github.com/mit-ll-responsible-ai/hydra-zen)
- error[call-non-callable] src/hydra_zen/_hydra_overloads.py:110:20: Object of type `F` is not callable
- error[call-non-callable] src/hydra_zen/_hydra_overloads.py:341:16: Object of type `F` is not callable
- error[call-non-callable] src/hydra_zen/_utils/coerce.py:199:16: Object of type `_T` is not callable
- Found 640 diagnostics
+ Found 637 diagnostics

boostedblob (https://github.com/hauntsaninja/boostedblob)
- error[call-non-callable] boostedblob/globals.py:254:26: Object of type `F` is not callable
- error[call-non-callable] boostedblob/path.py:268:16: Object of type `F` is not callable
- error[call-non-callable] boostedblob/path.py:272:16: Object of type `F` is not callable
- Found 40 diagnostics
+ Found 37 diagnostics

mypy (https://github.com/python/mypy)
- error[call-non-callable] mypyc/codegen/emitmodule.py:230:15: Object of type `F` is not callable
- error[call-non-callable] mypyc/test-data/fixtures/testutil.py:102:16: Object of type `F` is not callable
- error[call-non-callable] mypyc/test/testutil.py:129:15: Object of type `F` is not callable
- Found 3330 diagnostics
+ Found 3327 diagnostics

mongo-python-driver (https://github.com/mongodb/mongo-python-driver)
- error[call-non-callable] pymongo/_csot.py:108:38: Object of type `F` is not callable
- error[call-non-callable] pymongo/_csot.py:109:26: Object of type `F` is not callable
- error[call-non-callable] pymongo/_csot.py:118:32: Object of type `F` is not callable
- error[call-non-callable] pymongo/_csot.py:119:20: Object of type `F` is not callable
- error[call-non-callable] pymongo/asynchronous/helpers.py:47:26: Object of type `F` is not callable
- error[call-non-callable] pymongo/asynchronous/helpers.py:67:30: Object of type `F` is not callable
- error[call-non-callable] pymongo/synchronous/helpers.py:47:20: Object of type `F` is not callable
- error[call-non-callable] pymongo/synchronous/helpers.py:67:24: Object of type `F` is not callable
- Found 560 diagnostics
+ Found 552 diagnostics

meson (https://github.com/mesonbuild/meson)
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:53:16: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:62:16: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:76:15: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:85:15: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:103:20: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:118:20: Object of type `_TV_FN_Operator` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:237:20: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:556:20: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:650:20: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/interpreterbase/decorators.py:806:20: Object of type `TV_func` is not callable
- error[call-non-callable] mesonbuild/rewriter.py:99:20: Object of type `TV_func` is not callable
- Found 1398 diagnostics
+ Found 1387 diagnostics

bokeh (https://github.com/bokeh/bokeh)
- error[call-non-callable] src/bokeh/document/locking.py:93:19: Object of type `F` is not callable
- error[call-non-callable] src/bokeh/document/locking.py:97:13: Object of type `F` is not callable
- error[call-non-callable] src/bokeh/server/session.py:94:30: Object of type `F` is not callable
- Found 953 diagnostics
+ Found 950 diagnostics

streamlit (https://github.com/streamlit/streamlit)
- error[call-non-callable] lib/streamlit/deprecation_util.py:97:18: Object of type `TFunc` is not callable
- error[call-non-callable] lib/streamlit/elements/dialog_decorator.py:99:17: Object of type `F` is not callable
- error[call-non-callable] lib/streamlit/runtime/fragment.py:245:38: Object of type `F` is not callable
- error[call-non-callable] lib/streamlit/runtime/metrics_util.py:443:22: Object of type `F` is not callable
- Found 3274 diagnostics
+ Found 3270 diagnostics

rotki (https://github.com/rotki/rotki)
- error[call-non-callable] rotkehlchen/chain/evm/transactions.py:78:22: Object of type `T` is not callable
- Found 2043 diagnostics
+ Found 2042 diagnostics

zulip (https://github.com/zulip/zulip)
- error[call-non-callable] corporate/tests/test_stripe.py:153:33: Object of type `CallableT` is not callable
- error[call-non-callable] zerver/lib/rest.py:217:12: Object of type `_F` is not callable
- error[call-non-callable] zerver/tests/test_auth_backends.py:1095:28: Object of type `AuthFuncT` is not callable
- error[call-non-callable] zerver/tests/test_auth_backends.py:8094:28: Object of type `AuthFuncT` is not callable
- error[call-non-callable] zproject/backends.py:349:16: Object of type `AuthFuncT` is not callable
- error[call-non-callable] zproject/backends.py:357:16: Object of type `AuthFuncT` is not callable
- error[call-non-callable] zproject/backends.py:376:14: Object of type `AuthFuncT` is not callable
- error[call-non-callable] zproject/backends.py:386:14: Object of type `AuthFuncT` is not callable
- Found 6977 diagnostics
+ Found 6969 diagnostics