Merge pull request #3643 from Hosch250/Issue2182

Extract Interface refactoring edge casr fix

Author: retailcoder

RetailCoder.VBE/UI/Command/Refactorings/RefactorExtractInterfaceCommand.cs

@@ -1,6 +1,9 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.InteropServices;
+using Antlr4.Runtime;
+using Rubberduck.Parsing;
+using Rubberduck.Parsing.Grammar;
 using Rubberduck.Parsing.Symbols;
 using Rubberduck.Parsing.VBA;
 using Rubberduck.Refactorings.ExtractInterface;
@@ -41,14 +44,27 @@ protected override bool EvaluateCanExecute(object parameter)
                 item.QualifiedName.QualifiedModuleName.Equals(selection.Value.QualifiedName)
                 && ModuleTypes.Contains(item.DeclarationType));
 
+            if (interfaceClass == null)
+            {
+                return false;
+            }
+
             // interface class must have members to be implementable
             var hasMembers = _state.AllUserDeclarations.Any(item => 
                 item.DeclarationType.HasFlag(DeclarationType.Member) 
                 && item.ParentDeclaration != null 
                 && item.ParentDeclaration.Equals(interfaceClass));
+            
+            if (!hasMembers)
+            {
+                return false;
+            }
+
+            var parseTree = _state.GetParseTree(interfaceClass.QualifiedName.QualifiedModuleName);
+            var context = ((ParserRuleContext)parseTree).FindChildren<VBAParser.ImplementsStmtContext>();
 
             // true if active code pane is for a class/document/form module
-            return interfaceClass != null && hasMembers;
+            return !context.Any();
         }
 
         protected override void OnExecute(object parameter)