Update checkexpr.py

Author: BobTheBuidler

mypy/checkexpr.py

@@ -657,7 +657,7 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
         return ret_type
 
     def check_str_format_call(self, e: CallExpr) -> None:
-        """More precise type checking for str.format() calls on literals."""
+        """More precise type checking for str.format() calls on literals and folded constants."""
         assert isinstance(e.callee, MemberExpr)
         format_value = None
         folded_callee_expr = constant_fold_expr(e.callee.expr, "<unused>")