Deal with coalescing literal null - fixes #707

Author: GrahamTheCoder

CodeConverter/CSharp/VisualBasicEqualityComparison.cs

@@ -91,8 +91,6 @@ private static bool IsNonEmptyStringLiteral(VBSyntax.ExpressionSyntax vbExpr)
 
         public ExpressionSyntax VbCoerceToNonNullString(VBSyntax.ExpressionSyntax vbNode, ExpressionSyntax csNode, TypeInfo typeInfo, bool knownNotNull = false)
         {
-            bool isStringType = typeInfo.Type.SpecialType == SpecialType.System_String;
-
             if (IsNothingOrEmpty(vbNode)) {
                 return EmptyStringExpression();
             }
@@ -101,7 +99,7 @@ public ExpressionSyntax VbCoerceToNonNullString(VBSyntax.ExpressionSyntax vbNode
                 return csNode;
             }
 
-            csNode = isStringType
+            csNode = typeInfo.Type.SpecialType == SpecialType.System_String
                 ? SyntaxFactory.ParenthesizedExpression(Coalesce(csNode, EmptyStringExpression()))
                 : Coalesce(csNode, EmptyCharArrayExpression());
 

Tests/CSharp/StatementTests/StatementTests.cs

@@ -1809,6 +1809,45 @@ internal partial class Issue579SelectCaseWithCaseInsensitiveTextCompare
 CS0825: The contextual keyword 'var' may only appear within a local variable declaration or in script code");
         }
 
+        [Fact]
+        public async Task Issue707SelectCaseAsync()
+        {
+            await TestConversionVisualBasicToCSharpAsync(@"
+Class Issue707SelectCaseAsyncClass
+    Private Function Exists(sort As Char?) As Boolean?
+        Select Case Microsoft.VisualBasic.LCase(sort + """")
+            Case """", Nothing
+                Return False
+            Case Else
+                Return True
+        End Select
+    End Function
+End Class", @"using Microsoft.VisualBasic; // Install-Package Microsoft.VisualBasic
+using Microsoft.VisualBasic.CompilerServices; // Install-Package Microsoft.VisualBasic
+
+internal partial class Issue707SelectCaseAsyncClass
+{
+    private bool? Exists(char? sort)
+    {
+        switch (Strings.LCase(Conversions.ToString(sort) + """") ?? """")
+        {
+            case var @case when @case == """":
+            case var case1 when case1 == """":
+                {
+                    return false;
+                }
+
+            default:
+                {
+                    return true;
+                }
+        }
+    }
+}
+1 target compilation errors:
+CS0825: The contextual keyword 'var' may only appear within a local variable declaration or in script code");
+        }
+
         [Fact]
         public async Task TryCatchAsync()
         {