Only cast when switching on enum

Author: GrahamTheCoder

CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ### VB -> C#
 * Handle Option Compare Text case insensitive comparisons in switch statements [#579](https://github.com/icsharpcode/CodeConverter/issues/579)
+* Fix compilation error when switching with enum cases [#549](https://github.com/icsharpcode/CodeConverter/issues/549)
 
 ### C# -> VB
 

CodeConverter/CSharp/MethodBodyExecutableStatementVisitor.cs

@@ -660,18 +660,18 @@ public override async Task<SyntaxList<StatementSyntax>> VisitSelectBlock(VBSynta
                 foreach (var c in block.CaseStatement.Cases) {
                     if (c is VBSyntax.SimpleCaseClauseSyntax s) {
                         var originalExpressionSyntax = (ExpressionSyntax)await s.Value.AcceptAsync(_expressionVisitor);
-                        // CSharp requires an explicit cast from the base type (e.g. int) in most cases switching on an enum
+                        var caseTypeInfo = _semanticModel.GetTypeInfo(s.Value);
                         var typeConversionKind = CommonConversions.TypeConversionAnalyzer.AnalyzeConversion(s.Value);
                         var correctTypeExpressionSyntax = CommonConversions.TypeConversionAnalyzer.AddExplicitConversion(s.Value, originalExpressionSyntax, typeConversionKind, true, true);
                         var constantValue = _semanticModel.GetConstantValue(s.Value);
-                        var caseTypeInfo = _semanticModel.GetTypeInfo(s.Value);
                         var notAlreadyUsed = !constantValue.HasValue || usedConstantValues.Add(constantValue.Value);
 
                         // Pass both halves in case we can optimize away the check based on the switch expr
                         var wrapForStringComparison = isStringComparison && (caseInsensitiveStringComparison ||
                             vbEquality.VbCoerceToNonNullString(vbExpr, csSwitchExpr, switchExprTypeInfo, true, s.Value, originalExpressionSyntax, caseTypeInfo, false).rhs != originalExpressionSyntax);
 
-                        var csExpressionToUse = wrapForStringComparison ? originalExpressionSyntax : correctTypeExpressionSyntax.Expr;
+                        // CSharp requires an explicit cast from the base type (e.g. int) in most cases switching on an enum
+                        var csExpressionToUse = wrapForStringComparison || switchExprTypeInfo.ConvertedType?.IsEnumType() == false || caseTypeInfo.Type?.IsEnumType() == true ? originalExpressionSyntax : correctTypeExpressionSyntax.Expr;
 
                         var caseSwitchLabelSyntax = !wrapForStringComparison && correctTypeExpressionSyntax.IsConst && notAlreadyUsed
                             ? (SwitchLabelSyntax)SyntaxFactory.CaseSwitchLabel(csExpressionToUse)

Tests/CSharp/StatementTests/StatementTests.cs

@@ -1923,6 +1923,53 @@ private IEnumerable<int> TestMethod(int number)
             yield return i;
         yield break;
     }
+}");
+        }
+
+        [Fact]
+        public async Task SwitchIntToEnumAsync()
+        {
+            await TestConversionVisualBasicToCSharpAsync(@"Module Main
+    Public Enum EWhere As Short
+        None = 0
+        Bottom = 1
+    End Enum
+
+    Friend Function prtWhere(ByVal aWhere As EWhere) As String
+        Select Case aWhere
+            Case EWhere.None
+                Return "" ""
+            Case EWhere.Bottom
+                Return ""_ ""
+        End Select
+
+    End Function
+End Module", @"
+internal static partial class Main
+{
+    public enum EWhere : short
+    {
+        None = 0,
+        Bottom = 1
+    }
+
+    internal static string prtWhere(EWhere aWhere)
+    {
+        switch (aWhere)
+        {
+            case EWhere.None:
+                {
+                    return "" "";
+                }
+
+            case EWhere.Bottom:
+                {
+                    return ""_ "";
+                }
+        }
+
+        return default;
+    }
 }");
         }
     }

Tests/VB/StatementTests.cs

@@ -1389,7 +1389,9 @@ End Class
         [Fact]
         public async Task YieldAsync()
         {
-            await TestConversionCSharpToVisualBasicAsync(@"class TestClass
+            await TestConversionCSharpToVisualBasicAsync(@"using System.Collections.Generic;
+
+class TestClass
 {
     IEnumerable<int> TestMethod(int number)
     {
@@ -1398,19 +1400,19 @@ IEnumerable<int> TestMethod(int number)
         for (int i = 0; i < number; i++)
             yield return i;
     }
-}", @"Friend Class TestClass
+}", @"Imports System.Collections.Generic
+
+Friend Class TestClass
     Private Iterator Function TestMethod(ByVal number As Integer) As IEnumerable(Of Integer)
         If number < 0 Then Return
 
         For i As Integer = 0 To number - 1
             Yield i
         Next
     End Function
-End Class
-
-1 source compilation errors:
-CS0246: The type or namespace name 'IEnumerable<>' could not be found (are you missing a using directive or an assembly reference?)");
+End Class");
         }
+
         [Fact]
         public async Task ObjectCreationExpressionInInvocationExpressionAsync() {
             await TestConversionCSharpToVisualBasicAsync(