Parse signed/unsigned integer data type in MySQL CAST

MySQL doesn't have the same set of possible CAST types as for e.g.
column definitions. For example, it raises a syntax error for `CAST(1 AS
INTEGER SIGNED)` and instead expects `CAST(1 AS SIGNED INTEGER)`.

We retain the current somewhat permissive datatype parsing behavior
(e.g. allowing `CAST(1 AS BIGINT)` even though MySQL would raise a
syntax error), and add two datatypes for this specific case (`SIGNED
[INTEGER]` and `UNSIGNED [INTEGER]`).

Closes apache#1589

src/ast/data_type.rs

@@ -238,6 +238,26 @@ pub enum DataType {
     UnsignedBigInt(Option<u64>),
     /// Unsigned Int8 with optional display width e.g. INT8 UNSIGNED or INT8(11) UNSIGNED
     UnsignedInt8(Option<u64>),
+    /// Signed integer as used in [MySQL CAST] target types, with optional `INTEGER` suffix:
+    /// `SIGNED [INTEGER]`
+    ///
+    /// Note that this doesn't accept a display width and is reversed from the syntax used in column
+    /// definitions ([`DataType::Int`]): `INTEGER [SIGNED]`
+    ///
+    /// Semantically equivalent to `BIGINT`.
+    ///
+    /// [MySQL CAST]: https://dev.mysql.com/doc/refman/8.4/en/cast-functions.html
+    Signed(bool),
+    /// Unsigned integer as used in [MySQL CAST] target types, with optional `INTEGER` suffix:
+    /// `UNSIGNED [INTEGER]`
+    ///
+    /// Note that this doesn't accept a display widths and is reversed from the syntax used in
+    /// column definitions ([`DataType::UnsignedInteger`]): `INTEGER [UNSIGNED]`
+    ///
+    /// Semantically equivalent to `BIGINT UNSIGNED`.
+    ///
+    /// [MySQL CAST]: https://dev.mysql.com/doc/refman/8.4/en/cast-functions.html
+    Unsigned(bool),
     /// Float4 as alias for Real in [postgresql]
     ///
     /// [postgresql]: https://www.postgresql.org/docs/15/datatype.html
@@ -515,6 +535,12 @@ impl fmt::Display for DataType {
             DataType::UInt256 => {
                 write!(f, "UInt256")
             }
+            DataType::Signed(integer) => {
+                write!(f, "SIGNED{}", if *integer { " INTEGER" } else { "" })
+            }
+            DataType::Unsigned(integer) => {
+                write!(f, "UNSIGNED{}", if *integer { " INTEGER" } else { "" })
+            }
             DataType::Real => write!(f, "REAL"),
             DataType::Float4 => write!(f, "FLOAT4"),
             DataType::Float32 => write!(f, "Float32"),

src/ast/mod.rs

@@ -798,8 +798,9 @@ pub enum Expr {
         kind: CastKind,
         expr: Box<Expr>,
         data_type: DataType,
-        // Optional CAST(string_expression AS type FORMAT format_string_expression) as used by BigQuery
-        // https://cloud.google.com/bigquery/docs/reference/standard-sql/format-elements#formatting_syntax
+        /// Optional CAST(string_expression AS type FORMAT format_string_expression) as used by [BigQuery]
+        ///
+        /// [BigQuery]: https://cloud.google.com/bigquery/docs/reference/standard-sql/format-elements#formatting_syntax
         format: Option<CastFormat>,
     },
     /// AT a timestamp to a different timezone e.g. `FROM_UNIXTIME(0) AT TIME ZONE 'UTC-06:00'`

src/keywords.rs

@@ -790,6 +790,7 @@ define_keywords!(
     SHARE,
     SHARING,
     SHOW,
+    SIGNED,
     SIMILAR,
     SKIP,
     SLOW,

src/parser/mod.rs

@@ -9110,6 +9110,14 @@ impl<'a> Parser<'a> {
                     let columns = self.parse_returns_table_columns()?;
                     Ok(DataType::Table(columns))
                 }
+                Keyword::SIGNED => {
+                    let integer = self.parse_keyword(Keyword::INTEGER);
+                    Ok(DataType::Signed(integer))
+                }
+                Keyword::UNSIGNED => {
+                    let integer = self.parse_keyword(Keyword::INTEGER);
+                    Ok(DataType::Unsigned(integer))
+                }
                 _ => {
                     self.prev_token();
                     let type_name = self.parse_object_name(false)?;

tests/sqlparser_mysql.rs

@@ -3255,3 +3255,21 @@ fn parse_looks_like_single_line_comment() {
         "UPDATE account SET balance = balance WHERE account_id = 5752",
     );
 }
+
+#[test]
+fn parse_cast_integers() {
+    mysql().verified_expr("CAST(foo AS UNSIGNED)");
+    mysql().verified_expr("CAST(foo AS SIGNED)");
+    mysql().verified_expr("CAST(foo AS UNSIGNED INTEGER)");
+    mysql().verified_expr("CAST(foo AS SIGNED INTEGER)");
+
+    mysql()
+        .run_parser_method("CAST(foo AS UNSIGNED(3))", |p| p.parse_expr())
+        .expect_err("CAST doesn't allow display width");
+    mysql()
+        .run_parser_method("CAST(foo AS UNSIGNED(3) INTEGER)", |p| p.parse_expr())
+        .expect_err("CAST doesn't allow display width");
+    mysql()
+        .run_parser_method("CAST(foo AS UNSIGNED INTEGER(3))", |p| p.parse_expr())
+        .expect_err("CAST doesn't allow display width");
+}