re-add support for nested comments in mssql (apache#1754)

Author: lovasoa

src/dialect/mssql.rs

@@ -95,4 +95,9 @@ impl Dialect for MsSqlDialect {
     fn supports_timestamp_versioning(&self) -> bool {
         true
     }
+
+    /// See <https://learn.microsoft.com/en-us/sql/t-sql/language-elements/slash-star-comment-transact-sql?view=sql-server-ver16>
+    fn supports_nested_comments(&self) -> bool {
+        true
+    }
 }

tests/sqlparser_mssql.rs

@@ -1620,6 +1620,22 @@ fn parse_create_table_with_valid_options() {
     }
 }
 
+#[test]
+fn parse_nested_slash_star_comment() {
+    let sql = r#"
+    select
+    /*
+       comment level 1
+       /*
+          comment level 2
+       */
+    */
+    1;
+    "#;
+    let canonical = "SELECT 1";
+    ms().one_statement_parses_to(sql, canonical);
+}
+
 #[test]
 fn parse_create_table_with_invalid_options() {
     let invalid_cases = vec![