Fix false positive for unhashable-member when subclassing dict. (#7757)

Closes #7501

Co-authored-by: Pierre Sassoulas <[email protected]>

Author: mbyrnepr2

doc/whatsnew/fragments/7501.false_positive

@@ -0,0 +1,3 @@
+Fix false positive for ``unhashable-member`` when subclassing ``dict`` and using the subclass as a dictionary key.
+
+Closes #7501

pylint/checkers/utils.py

@@ -1955,7 +1955,7 @@ def is_hashable(node: nodes.NodeNG) -> bool:
     """
     try:
         for inferred in node.infer():
-            if inferred is astroid.Uninferable:
+            if inferred is astroid.Uninferable or isinstance(inferred, nodes.ClassDef):
                 return True
             if not hasattr(inferred, "igetattr"):
                 return True

tests/functional/u/unhashable_member.py

@@ -22,3 +22,9 @@ class Unhashable:
 {"tomato": "tomahto"}
 {dict: {}}
 {lambda x: x: "tomato"}  # pylint: disable=unnecessary-lambda
+
+
+class FromDict(dict):
+    ...
+
+{FromDict: 1}