Add ui test with suffixed string literals in attribute

test_suite/tests/ui/malformed/str_suffix.rs

@@ -0,0 +1,10 @@
+use serde::Serialize;
+
+#[derive(Serialize)]
+#[serde(bound = ""huh)]
+pub struct Struct {
+    #[serde(rename = ""what)]
+    pub field: i32,
+}
+
+fn main() {}