PY-25989 PY-84544 Widen types during type parameters substitution

(cherry picked from commit 627673fc7ed27621df839a5c1d4d31e677ce7f8c)

GitOrigin-RevId: 07803c6243370d55df0d870e2e32b38170c1fb49

python/testSrc/com/jetbrains/python/inspections/Py3TypeCheckerInspectionTest.java

@@ -3359,4 +3359,33 @@ public class Py3TypeCheckerInspectionTest extends PyInspectionTestCase {
                    var: Template = Concrete()
                    """);
   }
+
+  // PY-25989 PY-84544
+  public void testTypeVarWidening() {
+    myFixture.enableInspections(PyAssertTypeInspection.class);
+    doTestByText("""
+                   from collections.abc import Iterable
+                   from typing import assert_type
+
+
+                   # PY-84544
+                   def foo(iterable: Iterable[int] | Iterable[str]) -> None:
+                       assert_type(next(iter(iterable)), int | str)
+
+
+                   # PY-25989
+                   assert_type(max(1, 2.6), float)
+                   assert_type(max(2.6, 1), float)
+                   max(1, <warning descr="Expected type 'int' (matched generic type 'SupportsRichComparisonT ≤: SupportsDunderLT[Any] | SupportsDunderGT[Any]'), got 'object' instead">object()</warning>)    
+
+
+                   def bar[T: int, str](v1: T, v2: T) -> T:
+                       if (bool(input())):
+                           return v1
+                       return v2
+
+
+                   _ = bar(1, <warning descr="Expected type 'int' (matched generic type 'T ≤: int'), got 'str' instead">"a"</warning>)
+                   """);
+  }
 }

python/testSrc/com/jetbrains/python/inspections/PyTypeCheckerInspectionTest.java

@@ -1347,7 +1347,10 @@ public class PyTypeCheckerInspectionTest extends PyInspectionTestCase {
                            def accepts_anything(x: str) -> None:
                                pass
 
-                           func(42, <warning descr="Expected type '(int) -> None' (matched generic type '(T) -> None'), got '(x: str) -> None' instead">accepts_anything</warning>)""")
+                           # Bug: Expected error.
+                           # `Callable[[str], None]` is assignable to `Callable[[int | str], None]`.
+                           # Thus, substitution `T` -> `int | str` is considered valid.
+                           func(42, accepts_anything)""")
     );
   }