fix: add 'K_TYPE' to KeywordOrIdentifier to allow 'type' as a column name (#2448)

TYPE is a non-reserved keyword in MySQL, so statements like
'ALTER TABLE tbl DROP COLUMN type' are valid without quoting.
Follows the same approach as #2340 (K_DATA).

Fixes #2447

Author: minleejae

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -1756,7 +1756,7 @@ TOKEN:
  * Supported tokens:
  *  - <S_IDENTIFIER>: Standard unquoted SQL identifier
  *  - <S_QUOTED_IDENTIFIER>: Quoted identifier (e.g., `identifier` or "identifier")
- *  - <K_NAME>, <K_NEXT>, <K_VALUE>, <K_PUBLIC>, <K_STRING>, <K_DATA>: Specific keywords treated as identifiers
+ *  - <K_NAME>, <K_NEXT>, <K_VALUE>, <K_PUBLIC>, <K_STRING>, <K_DATA>, <K_TYPE>: Specific keywords treated as identifiers
  *
  * @return Token representing the identifier or keyword used as identifier
  */
@@ -1774,6 +1774,7 @@ Token KeywordOrIdentifier():
       | tk = <K_PUBLIC>
       | tk = <K_STRING>
       | tk = <K_DATA>
+      | tk = <K_TYPE>
     )
     { return tk; }
 }

src/test/java/net/sf/jsqlparser/statement/alter/AlterTest.java

@@ -259,6 +259,11 @@ public void testAlterTableDropColumnIssue2339() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("ALTER TABLE test DROP COLUMN Data");
     }
 
+    @Test
+    public void testAlterTableDropColumnIssue2447() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("ALTER TABLE test DROP COLUMN type");
+    }
+
     @Test
     public void testAlterTableDropConstraint() throws JSQLParserException {
         final String sql = "ALTER TABLE test DROP CONSTRAINT YYY";
@@ -469,6 +474,11 @@ public void testAlterTableChangeColumnIssue2339() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("ALTER TABLE tb_test CHANGE data INT (10)");
     }
 
+    @Test
+    public void testAlterTableChangeColumnIssue2447() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("ALTER TABLE tb_test CHANGE type INT (10)");
+    }
+
     @Test
     public void testAlterTableAddColumnWithZone() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed(
@@ -668,6 +678,18 @@ public void testAlterTableRenameColumn2() throws JSQLParserException {
         assertEquals(expression.getColumnName(), "full_name");
     }
 
+    @Test
+    public void testAlterTableRenameColumnIssue2447() throws JSQLParserException {
+        String sql = "ALTER TABLE test_table RENAME COLUMN type TO type2";
+        assertSqlCanBeParsedAndDeparsed(sql);
+
+        Alter alter = (Alter) CCJSqlParserUtil.parse(sql);
+        AlterExpression expression = alter.getAlterExpressions().get(0);
+        assertEquals(expression.getOperation(), AlterOperation.RENAME);
+        assertEquals(expression.getColOldName(), "type");
+        assertEquals(expression.getColumnName(), "type2");
+    }
+
     @Test
     public void testAlterTableForeignKeyIssue981() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed(