Fix used-before-assignment false positive for walrus operator in dictionary (#8176) (#8254)

(cherry picked from commit 32e1545)

Co-authored-by: Zen Lee <53538590+zenlyj@users.noreply.github.com>

Author: github-actions[bot]

doc/whatsnew/fragments/8125.bugfix

@@ -0,0 +1,4 @@
+Fix ``used-before-assignment`` false positive when the walrus operator
+is used with a ternary operator in dictionary key/value initialization.
+
+Closes #8125

pylint/checkers/variables.py

@@ -2245,6 +2245,11 @@ def _maybe_used_and_assigned_at_once(defstmt: nodes.Statement) -> bool:
             return True
         if isinstance(value, nodes.Lambda) and isinstance(value.body, nodes.IfExp):
             return True
+        if isinstance(value, nodes.Dict) and any(
+            isinstance(item[0], nodes.IfExp) or isinstance(item[1], nodes.IfExp)
+            for item in value.items
+        ):
+            return True
         if not isinstance(value, nodes.Call):
             return False
         return any(

tests/functional/u/used/used_before_assignment_ternary.py

@@ -29,6 +29,19 @@ def function_call_keyword_valid():
     var = foo(x=a if (a:='1') else '', y='', z='')
     var = foo(x='', y=foo(x='', y='', z=b if (b:='1') else ''), z='')
 
+def dictionary_items_valid():
+    """assignment as dictionary keys/values"""
+    var = {
+        0: w if (w:=input()) else "",
+    }
+    var = {
+        x if (x:=input()) else "": 0,
+    }
+    var = {
+        0: y if (y:=input()) else "",
+        z if (z:=input()) else "": 0,
+    }
+
 def complex_valid():
     """assignment within complex call expression"""
     var = str(bar(bar(a if (a:=1) else 0))).lower().upper()