From e2d4e96fb4929ffe9154cdee17639ebf7c35619b Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Mon, 11 Apr 2016 16:11:34 +0200
Subject: [PATCH] [mcs] Tie-breaking rules are applied also for non-equivalent
 parameter types. Fixess #40183

---
 mcs/mcs/ecore.cs               | 29 +++++++++++----
 mcs/tests/gtest-optional-36.cs | 66 ++++++++++++++++++++++++++++++++++
 mcs/tests/test-933.cs          | 22 ++++++++++++
 mcs/tests/ver-il-net_4_x.xml   | 44 +++++++++++++++++++++++
 4 files changed, 155 insertions(+), 6 deletions(-)
 create mode 100644 mcs/tests/gtest-optional-36.cs
 create mode 100644 mcs/tests/test-933.cs

diff --git a/mcs/mcs/ecore.cs b/mcs/mcs/ecore.cs
index 56c1b2edb88..145f222bdcd 100644
--- a/mcs/mcs/ecore.cs
+++ b/mcs/mcs/ecore.cs
@@ -4704,8 +4704,14 @@ namespace Mono.CSharp {
 
 				// for each argument, the conversion to 'ct' should be no worse than 
 				// the conversion to 'bt'.
-				if (result == 2)
-					return false;
+				if (result == 2) {
+					better_at_least_one = false;
+
+					++j;
+					while (j < args_count && !args [j++].IsDefaultArgument) ;
+
+					break;
+				}
 
 				// for at least one argument, the conversion to 'ct' should be better than 
 				// the conversion to 'bt'.
@@ -4717,15 +4723,26 @@ namespace Mono.CSharp {
 				return true;
 
 			//
-			// Tie-breaking rules are applied only for equivalent parameter types
+			// LAMESPEC: Tie-breaking rules for not equivalent parameter types
 			//
 			if (!are_equivalent) {
 				//
-				// LAMESPEC: A candidate with less default parameters is still better when there
+				// A candidate with no default parameters is still better when there
 				// is no better expression conversion
 				//
-				if (candidate_pd.Count < best_pd.Count && !candidate_params && best_pd.FixedParameters [j].HasDefaultValue) {
-					return true;
+				if (candidate_pd.Count < best_pd.Count) {
+					if (!candidate_params && !candidate_pd.FixedParameters [j - j].HasDefaultValue) {
+						return true;
+					}
+				} else if (candidate_pd.Count == best_pd.Count) {
+					if (candidate_params)
+						return false;
+
+					if (!candidate_pd.FixedParameters [j - 1].HasDefaultValue && best_pd.FixedParameters [j - 1].HasDefaultValue)
+						return true;
+
+					if (candidate_pd.FixedParameters [j - 1].HasDefaultValue && best_pd.HasParams)
+						return true;
 				}
 
 				return false;
diff --git a/mcs/tests/gtest-optional-36.cs b/mcs/tests/gtest-optional-36.cs
new file mode 100644
index 00000000000..bf9f7d1523b
--- /dev/null
+++ b/mcs/tests/gtest-optional-36.cs
@@ -0,0 +1,66 @@
+using System;
+
+public class Program
+{
+	static int Arg (uint a, long b)
+	{
+		return 2;
+	}
+
+	static int Arg (int a, ulong b, int c = 9)
+	{
+		return 3;
+	}
+
+	static int Arg_2 (uint a, long b, params int[] arg)
+	{
+		return 2;
+	}
+
+	static int Arg_2 (int a, ulong b, int c = 0)
+	{
+		return 3;
+	}
+
+	static int Arg_3 (int a, long b, params int[] arg)
+	{
+		return 2;
+	}
+
+	static int Arg_3 (uint a, ulong b, int c = 0, int d = 1, params int[] oo)
+	{
+		return 3;
+	}	
+
+	public static int Main ()
+	{
+		if (Arg (0, 0) != 2)
+			return 1;
+
+		if (Arg (0, 0, 0) != 3)
+			return 2;
+
+		if (Arg_2 (0, 0) != 3)
+			return 3;
+
+		if (Arg_2 (0, 0, 0, 0) != 2)
+			return 4;
+
+		if (Arg_3 (0, 0) != 2)
+			return 5;
+
+		if (Arg_3 (0, 0, 0) != 2)
+			return 6;
+
+		if (Arg_3 (0, 0, 0, 0) != 2)
+			return 7;
+
+		if (Arg_3 (0, 0, 0, 0, 0) != 2)
+			return 8;
+
+		if (Arg_3 (0, 0, 0, 0, 0) != 2)
+			return 9;
+
+		return 0;
+	}
+}
diff --git a/mcs/tests/test-933.cs b/mcs/tests/test-933.cs
new file mode 100644
index 00000000000..2f076ebd254
--- /dev/null
+++ b/mcs/tests/test-933.cs
@@ -0,0 +1,22 @@
+using System;
+
+class X
+{
+	static int Foo (params X[] p)
+	{
+		return 1;
+	}
+
+	static int Foo (object p)
+	{
+		return 0;
+	}
+
+	static int Main ()
+	{
+		if (Foo ((X[]) null) != 1)
+			return 1;
+
+		return 0;
+	}
+}
\ No newline at end of file
diff --git a/mcs/tests/ver-il-net_4_x.xml b/mcs/tests/ver-il-net_4_x.xml
index b7054e4b289..21da636a0c5 100644
--- a/mcs/tests/ver-il-net_4_x.xml
+++ b/mcs/tests/ver-il-net_4_x.xml
@@ -30666,6 +30666,34 @@
       </method>
     </type>
   </test>
+  <test name="gtest-optional-36.cs">
+    <type name="Program">
+      <method name="Int32 Arg(UInt32, Int64)" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Arg(Int32, UInt64, Int32)" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Arg_2(UInt32, Int64, Int32[])" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Arg_2(Int32, UInt64, Int32)" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Arg_3(Int32, Int64, Int32[])" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Arg_3(UInt32, UInt64, Int32, Int32, Int32[])" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Main()" attrs="150">
+        <size>238</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+  </test>
   <test name="gtest-partial-01.cs">
     <type name="B`1[U]">
       <method name="Void .ctor()" attrs="6278">
@@ -51945,6 +51973,22 @@
       </method>
     </type>
   </test>
+  <test name="test-933.cs">
+    <type name="X">
+      <method name="Int32 Foo(X[])" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Foo(System.Object)" attrs="145">
+        <size>10</size>
+      </method>
+      <method name="Int32 Main()" attrs="145">
+        <size>29</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+  </test>
   <test name="test-94.cs">
     <type name="Base">
       <method name="Int32 IVehicle.Start()" attrs="481">
-- 
2.25.1