Update CHANGELOG and fix mypy compatibility for curry.partial

- Added a bugfix entry in CHANGELOG for `curry.partial` compatibility with mypy 1.6.1+.
- Modified `inference.py` to use a local variable for argument inference context.
- Added mypy configuration file and a test for `partial` functionality in `test_partial.py`.

Author: Adrian Acala

CHANGELOG.md

@@ -6,6 +6,13 @@ incremental in minor, bugfixes only are patches.
 See [0Ver](https://0ver.org/).
 
 
+## Unreleased
+
+### Bugfixes
+
+- Fixes the `curry.partial` compatibility with mypy 1.6.1+
+
+
 ## 0.25.0
 
 ### Features

returns/contrib/mypy/_typeops/inference.py

@@ -82,13 +82,15 @@ def _infer_constraints(
             self._fallback.arg_names,
             lambda index: checker.accept(exprs[index]),
         )
+
+        arg_context = checker.argument_infer_context()
         constraints = infer_constraints_for_callable(
             self._fallback,
             arg_types=[arg.type for arg in applied_args],
             arg_kinds=kinds,
             arg_names=[arg.name for arg in applied_args],
             formal_to_actual=formal_to_actual,
-            context=checker.argument_infer_context(),
+            context=arg_context,
         )
         return {
             constraint.type_var: constraint.target for constraint in constraints

test_partial/mypy.ini

@@ -0,0 +1,3 @@
+[mypy]
+python_version = 3.11
+plugins = returns.contrib.mypy.returns_plugin

test_partial/test_partial.py

@@ -0,0 +1,10 @@
+from returns.curry import partial
+
+
+def foo(x, bar=None):
+    """Add bar to x if bar is provided, otherwise return x."""
+    return x + bar if bar else x
+
+
+my_partial = partial(foo, bar=1)
+# Type checking: reveal_type(my_partial)