Chaining error: improve the error message

parser/src/diagnostics.rs

@@ -170,7 +170,7 @@ impl ParsingError {
                 "This is only valid in some contexts, like a right-hand assignment or a function argument.",
             ),
             Self::NonAssociativeOperator(_) => Some(
-                "Some operators can't be chained to avoid logical errors, such as comparison ones.\n\
+                "Some operators cannot be chained because doing so could lead to logical errors. Comparison operators are one example.\n\
                 Example: write `a == b && b == c` instead of `a == b == c`.",
             ),
             Self::ExpectedIdentifier(_, _) => Some(

tests/by-util/test_awk.rs

@@ -249,6 +249,15 @@ fn write_to_dev_full_does_not_panic() {
     );
 }
 
+// Chaining non-associative operators must report the diagnostic's help text.
+#[test]
+fn chained_comparison_reports_help_text() {
+    ucmd()
+        .arg("BEGIN { p < q < r }")
+        .run()
+        .stderr_contains("Some operators cannot be chained");
+}
+
 #[test]
 fn array_single_index_get_set() {
     ucmd()