more tweak on diagnostic messages

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -430,6 +430,7 @@ pub(crate) struct NotAsNegationOperator {
     #[primary_span]
     pub negated: Span,
     pub negated_desc: String,
+    pub negated_msg: String,
     #[suggestion_short(applicability = "machine-applicable", code = "!")]
     pub not: Span,
 }

compiler/rustc_parse/src/parser/expr.rs

@@ -660,9 +660,18 @@ impl<'a> Parser<'a> {
     fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
         // Emit the error...
         let negated_token = self.look_ahead(1, |t| t.clone());
+        let negtated_msg = if negated_token.is_numeric_lit() {
+            "bitwise not"
+        } else if negated_token.is_bool_lit() {
+            "logical negation"
+        } else {
+            "logical negation or bitwise not"
+        };
+
         self.sess.emit_err(NotAsNegationOperator {
             negated: negated_token.span,
             negated_desc: super::token_descr(&negated_token),
+            negated_msg: negtated_msg.to_string(),
             // Span the `not` plus trailing whitespace to avoid
             // trailing whitespace after the `!` in our suggestion
             not: self.sess.source_map().span_until_non_whitespace(lo.to(negated_token.span)),