Convert constant characters directly to constant strings

Author: GrahamTheCoder

CodeConverter/CSharp/TypeConversionAnalyzer.cs

@@ -469,6 +469,11 @@ private static ExpressionSyntax GetToStringConversionOrNull(ExpressionSyntax csN
             return csNode;
         }
 
+        if (currentType is {SpecialType: SpecialType.System_Char} && csNode is CSSyntax.LiteralExpressionSyntax {Token: {} t} l) {
+            return SyntaxFactory.LiteralExpression(SyntaxKind.StringLiteralExpression, SyntaxFactory.Token(t.LeadingTrivia, SyntaxKind.StringLiteralToken, "\"" + t.Text.Trim('\'') + "\"", t.ValueText, t.TrailingTrivia))
+                .WithLeadingTrivia(csNode.GetLeadingTrivia()).WithTrailingTrivia(csNode.GetTrailingTrivia());
+        }
+
         if (currentType.IsNumericType()) {
             var toString = SyntaxFactory.MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression,
                 csNode.AddParens(), ValidSyntaxFactory.IdentifierName(toStringMethodName));

Tests/CSharp/MissingSemanticModelInfo/ExpressionTests.cs

@@ -310,6 +310,7 @@ public void PositionEnumFromString(char c)
                     Console.WriteLine(1);
                     break;
                 }
+
             case ',':
                 {
                     Console.WriteLine(2);

Tests/CSharp/SpecialConversionTests.cs

@@ -317,19 +317,19 @@ public void Test()
         string a;
         a = Conversions.ToString(Chr(2));
         a = Conversions.ToString(Chr(2));
-        a = Conversions.ToString('\u0002');
-        a = Conversions.ToString('\u0002');
-        a = Conversions.ToString('\u0002');
+        a = ""\u0002"";
+        a = ""\u0002"";
+        a = ""\u0002"";
     }
 
     public void TestW()
     {
         string a;
         a = Conversions.ToString(ChrW(2));
         a = Conversions.ToString(ChrW(2));
-        a = Conversions.ToString('\u0002');
-        a = Conversions.ToString('\u0002');
-        a = Conversions.ToString('\u0002');
+        a = ""\u0002"";
+        a = ""\u0002"";
+        a = ""\u0002"";
     }
 
     public char Chr(object o)