IDISP003 when discarding.

Was not really a bug but there are clearer warnings we can produce.
Nicer when suppressing if nothing else.
Fix #206

Author: JohanLarsson

IDisposableAnalyzers.Test/IDISP003DisposeBeforeReassigningTests/Valid.cs

@@ -1688,5 +1688,27 @@ public void Dispose()
 
             RoslynAssert.Valid(Analyzer, DisposableCode, baseClass, code);
         }
+
+        [Test]
+        public static void DiscardedTwice()
+        {
+            var code = @"
+namespace N
+{
+    using System;
+    using System.IO;
+
+    public class C
+    {
+        public void M()
+        {
+            _ = File.OpenRead(string.Empty);
+            _ = File.OpenRead(string.Empty);
+        }
+    }
+}";
+
+            RoslynAssert.Valid(Analyzer, code);
+        }
     }
 }

IDisposableAnalyzers/Analyzers/AssignmentAnalyzer.cs

@@ -68,7 +68,8 @@ private static bool IsReassignedWithCreated(AssignmentExpressionSyntax assignmen
             }
 
             if (assignedSymbol == KnownSymbol.SerialDisposable.Disposable ||
-                assignedSymbol == KnownSymbol.SingleAssignmentDisposable.Disposable)
+                assignedSymbol == KnownSymbol.SingleAssignmentDisposable.Disposable ||
+                assignedSymbol is IDiscardSymbol)
             {
                 return false;
             }