Fix string interpolation bug and rename variable

- Fix ${regex} to {regex} in log message (was outputting literal text)
- Rename CaseSensitiveFunctions to CaseInsensitiveCapableFunctions
- Add test for IndexOfMatch with invalid regex in Compile()

Author: willibrandon

src/Serilog.Expressions/Expressions/Compilation/Text/TextMatchingTransformer.cs

@@ -66,7 +66,7 @@ Expression TryCompileIndexOfMatch(bool ignoreCase, Expression corpus, Expression
             }
         }
 
-        SelfLog.WriteLine($"Serilog.Expressions: `IndexOfMatch()` requires a constant string regular expression argument; found ${regex}.");
+        SelfLog.WriteLine($"Serilog.Expressions: `IndexOfMatch()` requires a constant string regular expression argument; found {regex}.");
         return new CallExpression(false, Operators.OpUndefined);
     }
 }

src/Serilog.Expressions/Expressions/Compilation/Validation/ExpressionValidator.cs

@@ -26,7 +26,7 @@ class ExpressionValidator : IdentityTransformer
     readonly List<string> _errors = new();
 
     // Functions that support case-insensitive operations (have StringComparison parameter)
-    static readonly HashSet<string> CaseSensitiveFunctions = new(StringComparer.OrdinalIgnoreCase)
+    static readonly HashSet<string> CaseInsensitiveCapableFunctions = new(StringComparer.OrdinalIgnoreCase)
     {
         // String operations
         Operators.OpContains,
@@ -103,7 +103,7 @@ protected override Expression Transform(CallExpression call)
         }
 
         // Check for invalid CI modifier usage
-        if (call.IgnoreCase && !CaseSensitiveFunctions.Contains(call.OperatorName))
+        if (call.IgnoreCase && !CaseInsensitiveCapableFunctions.Contains(call.OperatorName))
         {
             _errors.Add($"The function `{call.OperatorName}` does not support case-insensitive operation.");
         }

test/Serilog.Expressions.Tests/ExpressionValidationTests.cs

@@ -115,6 +115,9 @@ public void CompileMethodStillThrowsForInvalidExpressions()
 
         Assert.Throws<ArgumentException>(() => 
             SerilogExpression.Compile("Length(Name) ci"));
+        
+        Assert.Throws<ArgumentException>(() => 
+            SerilogExpression.Compile("IndexOfMatch(Text, '(?<')"));
     }
 
     [Theory]