Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Data.Linq/SqlClient/Query/SqlAggregateChecker.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using System.Data.Linq;
+
+namespace System.Data.Linq.SqlClient {
+
+    internal class SqlAggregateChecker {
+        Visitor visitor;
+
+        internal SqlAggregateChecker() {
+            this.visitor = new Visitor();
+        }
+
+        internal bool HasAggregates(SqlNode node) {
+            visitor.hasAggregates = false;
+            visitor.Visit(node);
+            return visitor.hasAggregates;
+        }
+
+        class Visitor : SqlVisitor {
+            internal bool hasAggregates;
+
+            internal Visitor() {
+            }
+
+            internal override SqlExpression VisitSubSelect(SqlSubSelect ss) {
+                return ss;
+            }
+            internal override SqlSource VisitSource(SqlSource source) {
+                return source;
+            }
+            internal override SqlExpression VisitUnaryOperator(SqlUnary uo) {
+                switch (uo.NodeType) {
+                    case SqlNodeType.Min:
+                    case SqlNodeType.Max:
+                    case SqlNodeType.Avg:
+                    case SqlNodeType.Sum:
+                    case SqlNodeType.Count:
+                    case SqlNodeType.LongCount:
+                        this.hasAggregates = true;
+                        return uo;
+                    default:
+                        return base.VisitUnaryOperator(uo);
+                }
+            }
+        }
+    }
+}