fix: Don't allow unparenthesizing walruses (#4155)

Signed-off-by: RedGuy12 <61329810+RedGuy12@users.noreply.github.com>
Signed-off-by: RedGuy12 <paul@reid-family.org>

CHANGES.md

@@ -22,6 +22,7 @@
 - Address a missing case in the change to allow empty lines at the beginning of all
   blocks, except immediately before a docstring (#4130)
 - For stubs, fix logic to enforce empty line after nested classes with bodies (#4141)
+- Fix crash when using a walrus in a dictionary (#4155)
 
 ### Configuration
 

src/black/linegen.py

@@ -242,7 +242,11 @@ def visit_dictsetmaker(self, node: Node) -> Iterator[Line]:
                 if i == 0:
                     continue
                 if node.children[i - 1].type == token.COLON:
-                    if child.type == syms.atom and child.children[0].type == token.LPAR:
+                    if (
+                        child.type == syms.atom
+                        and child.children[0].type == token.LPAR
+                        and not is_walrus_assignment(child)
+                    ):
                         if maybe_make_parens_invisible_in_atom(
                             child,
                             parent=node,

tests/data/cases/walrus_in_dict.py

@@ -0,0 +1,7 @@
+# flags: --preview
+{
+    "is_update": (up := commit.hash in update_hashes)
+}
+
+# output
+{"is_update": (up := commit.hash in update_hashes)}