Issue #28739: f-string expressions no longer accepted as docstrings and
by ast.literal_eval() even if they do not include subexpressions.
diff --git a/Python/compile.c b/Python/compile.c
index 35151cd..0e16075 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -3415,7 +3415,8 @@
 compiler_joined_str(struct compiler *c, expr_ty e)
 {
     VISIT_SEQ(c, expr, e->v.JoinedStr.values);
-    ADDOP_I(c, BUILD_STRING, asdl_seq_LEN(e->v.JoinedStr.values));
+    if (asdl_seq_LEN(e->v.JoinedStr.values) != 1)
+        ADDOP_I(c, BUILD_STRING, asdl_seq_LEN(e->v.JoinedStr.values));
     return 1;
 }