From 76f0a58429b4cfb47c77935cfca6ce88ce9be53e Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Thu, 1 Jun 2017 15:25:31 +0200
Subject: [PATCH] [mcs] Moves using static lookup at the end of simple name
 lookup rules. Fixes #55348

---
 mcs/mcs/context.cs                |  3 ++-
 mcs/mcs/ecore.cs                  | 26 +++++++++++++++-----------
 mcs/mcs/namespace.cs              |  2 +-
 mcs/tests/test-static-using-13.cs | 21 +++++++++++++++++++++
 mcs/tests/ver-il-net_4_x.xml      | 10 ++++++++++
 5 files changed, 49 insertions(+), 13 deletions(-)
 create mode 100644 mcs/tests/test-static-using-13.cs

diff --git a/mcs/mcs/context.cs b/mcs/mcs/context.cs
index ddcb149f942..24bccb69187 100644
--- a/mcs/mcs/context.cs
+++ b/mcs/mcs/context.cs
@@ -22,7 +22,8 @@ namespace Mono.CSharp
 	{
 		Normal = 0,
 		Probing = 1,
-		IgnoreAccessibility = 2
+		IgnoreAccessibility = 2,
+		IgnoreStaticUsing = 1 << 10
 	}
 
 	//
diff --git a/mcs/mcs/ecore.cs b/mcs/mcs/ecore.cs
index 99ba10dcb9d..4d472070a00 100644
--- a/mcs/mcs/ecore.cs
+++ b/mcs/mcs/ecore.cs
@@ -2762,9 +2762,13 @@ namespace Mono.CSharp {
 			return null;
 		}
 
-		public bool IsPossibleTypeOrNamespace (IMemberContext mc)
+		bool IsPossibleTypeOrNamespace (IMemberContext mc)
 		{
-			return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) != null;
+			//
+			// Has to ignore static usings because we are looking for any member not just type
+			// in this context
+			//
+			return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing | LookupMode.IgnoreStaticUsing, loc) != null;
 		}
 
 		public bool IsPossibleType (IMemberContext mc)
@@ -2886,6 +2890,15 @@ namespace Mono.CSharp {
 					return me;
 				}
 
+				//
+				// Stage 3: Lookup nested types, namespaces and type parameters in the context
+				//
+				if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
+					if (IsPossibleTypeOrNamespace (rc)) {
+						return ResolveAsTypeOrNamespace (rc, false);
+					}
+				}
+
 				var expr = NamespaceContainer.LookupStaticUsings (rc, Name, Arity, loc);
 				if (expr != null) {
 					if (Arity > 0) {
@@ -2898,15 +2911,6 @@ namespace Mono.CSharp {
 					return expr;
 				}
 
-				//
-				// Stage 3: Lookup nested types, namespaces and type parameters in the context
-				//
-				if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
-					if (IsPossibleTypeOrNamespace (rc)) {
-						return ResolveAsTypeOrNamespace (rc, false);
-					}
-				}
-
 				if ((restrictions & MemberLookupRestrictions.NameOfExcluded) == 0 && Name == "nameof")
 					return new NameOf (this);
 
diff --git a/mcs/mcs/namespace.cs b/mcs/mcs/namespace.cs
index 5384ee13686..3314ca2d48c 100644
--- a/mcs/mcs/namespace.cs
+++ b/mcs/mcs/namespace.cs
@@ -1157,7 +1157,7 @@ namespace Mono.CSharp {
 					match = texpr_fne;
 			}
 
-			if (types_using_table != null) {
+			if (types_using_table != null && (mode & LookupMode.IgnoreStaticUsing) == 0) {
 				foreach (var using_type in types_using_table) {
 					var type = MemberCache.FindNestedType (using_type, name, arity, true);
 					if (type == null)
diff --git a/mcs/tests/test-static-using-13.cs b/mcs/tests/test-static-using-13.cs
new file mode 100644
index 00000000000..67605391800
--- /dev/null
+++ b/mcs/tests/test-static-using-13.cs
@@ -0,0 +1,21 @@
+using System;
+using static TestClass;
+
+internal class Program
+{
+	public static void Main (string[] args)
+	{
+		var res = Directions.Up;
+	}
+}
+
+public enum Directions
+{
+	Up,
+	NotUp,
+}
+
+public static class TestClass
+{
+	public static int Directions;
+}
diff --git a/mcs/tests/ver-il-net_4_x.xml b/mcs/tests/ver-il-net_4_x.xml
index ba198950ecb..84e616ca01f 100644
--- a/mcs/tests/ver-il-net_4_x.xml
+++ b/mcs/tests/ver-il-net_4_x.xml
@@ -72776,6 +72776,16 @@
       </method>
     </type>
   </test>
+  <test name="test-static-using-13.cs">
+    <type name="Program">
+      <method name="Void Main(System.String[])" attrs="150">
+        <size>4</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+  </test>
   <test name="test-var-01.cs">
     <type name="Test">
       <method name="Int32 Main()" attrs="150">
-- 
2.25.1