Add test to validate scenario.

src/EditorFeatures/CSharpTest/RemoveUnnecessaryCast/RemoveUnnecessaryCastTests.cs

@@ -4489,6 +4489,31 @@ void M()
 }", parameters: new TestParameters(new CSharpParseOptions(LanguageVersion.CSharp7_1)));
         }
 
+        [WorkItem(12631, "https://github.com/dotnet/roslyn/issues/12631")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
+        public async Task RemoveRedundantBoolCast()
+        {
+            await TestInRegularAndScript1Async(
+@"
+class C
+{
+    void M()
+    {
+        var a = true;
+        var b = ![|(bool)|]a;
+    }
+}",
+@"
+class C
+{
+    void M()
+    {
+        var a = true;
+        var b = !a;
+    }
+}");
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
         public async Task DontIntroduceDefaultLiteralInPatternSwitchCase()
         {