I was overthinking it.

Author: StanFromIreland

Lib/_ast_unparse.py

@@ -744,7 +744,6 @@ def visit_DictComp(self, node):
                 self.traverse(node.value)
             else:
                 self.write("**")
-                self.set_precedence(_Precedence.EXPR, node.key)
                 self.traverse(node.key)
             for gen in node.generators:
                 self.traverse(gen)

Python/ast_unparse.c

@@ -471,7 +471,7 @@ append_ast_dictcomp(PyUnicodeWriter *writer, expr_ty e)
     }
     else {
         APPEND_STR("**");
-        APPEND_EXPR(e->v.DictComp.key, PR_EXPR);
+        APPEND_EXPR(e->v.DictComp.key, PR_TEST);
     }
     APPEND(comprehensions, e->v.DictComp.generators);
     APPEND_CHAR_FINISH('}');