[feature] Add intermediate AST support for delete expression

Author: gabriele-tomassetti

exist-core/src/main/antlr/org/exist/xquery/parser/XQueryTree.g

@@ -2198,6 +2198,8 @@ throws PermissionDeniedException, EXistException, XPathException
     |
     step=xqufInsertExpr [path]
     |
+    step=xqufDeleteExpr [path]
+    |
     step=transformWithExpr [path]
     |
     step=copyModifyExpr [path]
@@ -3930,6 +3932,26 @@ throws XPathException, PermissionDeniedException, EXistException
 	)
 	;
 
+xqufDeleteExpr [PathExpr path]
+returns [Expression step]
+throws XPathException, PermissionDeniedException, EXistException
+{
+}:
+	#(
+	    deleteAST:"delete"
+		{
+			PathExpr target = new PathExpr(context);
+		}
+		step=expr [target]
+		{
+			DeleteExpr deleteExpr = new DeleteExpr(context, target);
+			deleteExpr.setASTNode(deleteAST);
+			path.add(deleteExpr);
+			step = deleteExpr;
+		}
+	)
+	;
+
 mapConstr [PathExpr path]
 returns [Expression step]
 throws XPathException, PermissionDeniedException, EXistException