fix: avoid one JavaCC ambiguity warning

- LookAhead(2) DISTINCT | ALL
- `GroupBy` returns `ExpressionList<Expression>`

Signed-off-by: Andreas Reichel <andreas@manticore-projects.com>

Author: manticore-projects

src/main/java/net/sf/jsqlparser/statement/select/GroupByElement.java

@@ -22,8 +22,8 @@
 import net.sf.jsqlparser.expression.operators.relational.ParenthesedExpressionList;
 
 public class GroupByElement implements Serializable {
-    private ExpressionList groupByExpressions = new ExpressionList();
-    private List<ExpressionList> groupingSets = new ArrayList<>();
+    private ExpressionList<Expression> groupByExpressions = new ExpressionList<>();
+    private List<ExpressionList<Expression>> groupingSets = new ArrayList<>();
     // postgres rollup is an ExpressionList
     private boolean mysqlWithRollup = false;
 
@@ -53,14 +53,14 @@ public void addGroupByExpression(Expression groupByExpression) {
         if (groupByExpressions.getExpressions() == null) {
             groupByExpressions.setExpressions(new ArrayList());
         }
-        groupByExpressions.getExpressions().add(groupByExpression);
+        groupByExpressions.add(groupByExpression);
     }
 
-    public List<ExpressionList> getGroupingSets() {
+    public List<ExpressionList<Expression>> getGroupingSets() {
         return groupingSets;
     }
 
-    public void setGroupingSets(List<ExpressionList> groupingSets) {
+    public void setGroupingSets(List<ExpressionList<Expression>> groupingSets) {
         this.groupingSets = groupingSets;
     }
 
@@ -75,7 +75,7 @@ public String toString() {
         b.append("GROUP BY ");
 
         if (groupByExpressions != null) {
-            b.append(groupByExpressions.toString());
+            b.append(groupByExpressions);
         }
 
         int i = 0;

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

@@ -2442,7 +2442,7 @@ SelectPipeOperator SelectPipeOperator():
 }
 {
     (
-        ( operatorKeyToken = <K_SELECT> [ modifierToken=<K_DISTINCT> | modifierToken=<K_ALL> ] )
+        ( operatorKeyToken = <K_SELECT> [ LOOKAHEAD(2) ( modifierToken=<K_DISTINCT> | modifierToken=<K_ALL> ) ] )
         |
         operatorKeyToken = <K_EXTEND>
         |
@@ -3981,7 +3981,7 @@ GroupByElement GroupByColumnReferences():
     Expression columnReference;
     GroupByElement groupBy = new GroupByElement();
     Expression expr;
-    ExpressionList list;
+    ExpressionList<Expression> list;
     Token token;
 }
 {
@@ -4012,16 +4012,16 @@ GroupByElement GroupByColumnReferences():
     }
 }
 
-ExpressionList GroupingSet():
+ExpressionList<Expression> GroupingSet():
 {
-    ExpressionList list;
+    ExpressionList<Expression> list;
     Expression expression;
 }
 {
     (
         LOOKAHEAD(2) list = ParenthesedExpressionList()
         |
-        expression = SimpleExpression() { list = new ExpressionList(expression); }
+        expression = SimpleExpression() { list = new ExpressionList<Expression>(expression); }
     )
     {
         return list;