From 135dbb9c6d6add208ac0d0f763319fa37ecd6c11 Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Wed, 4 Oct 2017 12:40:13 +0200
Subject: [PATCH] [mcs] Allows shadowing of probing pattern variables

---
 mcs/errors/cs0136-6.cs | 16 ++++++++++++++++
 mcs/mcs/cs-parser.jay  |  2 +-
 mcs/mcs/statement.cs   |  6 +++---
 3 files changed, 20 insertions(+), 4 deletions(-)
 create mode 100644 mcs/errors/cs0136-6.cs

diff --git a/mcs/errors/cs0136-6.cs b/mcs/errors/cs0136-6.cs
new file mode 100644
index 00000000000..79fa771ff4d
--- /dev/null
+++ b/mcs/errors/cs0136-6.cs
@@ -0,0 +1,16 @@
+// CS0136: A local variable named `s' cannot be declared in this scope because it would give a different meaning to `s', which is already used in a `parent or current' scope to denote something else
+// Line: 11
+
+using System;
+
+class X
+{
+	void Test2 (object o)
+	{
+		if (o is ValueType s) {
+			if (o is long s) {
+				Console.WriteLine (s);
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/mcs/mcs/cs-parser.jay b/mcs/mcs/cs-parser.jay
index 6e20a8b13f0..2868d2fd8f6 100644
--- a/mcs/mcs/cs-parser.jay
+++ b/mcs/mcs/cs-parser.jay
@@ -4614,7 +4614,7 @@ additive_expression
 			var lt = (LocatedToken) $4;
 			var lv = new LocalVariable (current_block, lt.Value, lt.Location);
 			is_expr.Variable = lv;
-			current_block.AddLocalName (lv);
+			current_block.AddLocalName (lv.Name, lv, true);
 		}
 
 		$$ = is_expr;
diff --git a/mcs/mcs/statement.cs b/mcs/mcs/statement.cs
index 0c02bf0562a..369343a5df7 100644
--- a/mcs/mcs/statement.cs
+++ b/mcs/mcs/statement.cs
@@ -2878,9 +2878,9 @@ namespace Mono.CSharp {
 			AddLocalName (li.Name, li);
 		}
 
-		public void AddLocalName (string name, INamedBlockVariable li)
+		public virtual void AddLocalName (string name, INamedBlockVariable li, bool canShadowChildrenBlockName = false)
 		{
-			ParametersBlock.TopBlock.AddLocalName (name, li, false);
+			ParametersBlock.TopBlock.AddLocalName (name, li, canShadowChildrenBlockName);
 		}
 
 		public virtual void Error_AlreadyDeclared (string name, INamedBlockVariable variable, string reason)
@@ -4257,7 +4257,7 @@ namespace Mono.CSharp {
 			}
 		}
 
-		public void AddLocalName (string name, INamedBlockVariable li, bool ignoreChildrenBlocks)
+		public override void AddLocalName (string name, INamedBlockVariable li, bool ignoreChildrenBlocks)
 		{
 			if (names == null)
 				names = new Dictionary<string, object> ();
-- 
2.25.1