Rely on first-class span conversions of C# 14

Author: BCSharp

src/core/IronPython/Hosting/PythonOptionsParser.cs

@@ -150,12 +150,12 @@ protected override void ParseArgument(string/*!*/ arg) {
             }
 
             if (arg == "/?" || arg == "--help") {
-                HandleOptions("h".AsSpan());
+                HandleOptions("h");
                 return;
             }
 
             if (arg == "--version") {
-                HandleOptions("V".AsSpan());
+                HandleOptions("V");
                 return;
             }
 

src/core/IronPython/Modules/_io/StringIO.cs

@@ -114,7 +114,7 @@ private string readline(int limit) {
                         span = span.Slice(0, idx + 1);
                     }
                 } else if (_newline == string.Empty) {
-                    var idx = span.IndexOfAny("\r\n".AsSpan());
+                    var idx = span.IndexOfAny("\r\n");
                     if (idx != -1) {
                         if (span[idx++] == '\r') {
                             // ensure we don't split \r\n
@@ -377,7 +377,7 @@ private int DoWrite(string str) {
 
                 if (_newline is null) {
                     while (true) {
-                        var idx = span.IndexOfAny("\r\n".AsSpan());
+                        var idx = span.IndexOfAny("\r\n");
                         if (idx == -1)
                             break;
 

src/core/IronPython/Runtime/LiteralParser.cs

@@ -219,7 +219,7 @@ void handleError(in ReadOnlySpan<T> data, int start, int end, string reason) {
 #nullable enable
 
         private static bool TryParseExpression(Parser parser, ReadOnlySpan<char> data, [NotNullWhen(true)] out Expression? expression, [NotNullWhen(false)] out string? error) {
-            if (data.TrimStart(" \t\f\r\n".AsSpan()).Length == 0) {
+            if (data.TrimStart(" \t\f\r\n").Length == 0) {
                 expression = null;
                 error = "f-string: empty expression not allowed";
                 return false;
@@ -649,7 +649,7 @@ private static bool TryParseInt<T>(in ReadOnlySpan<T> text, int start, int lengt
         }
 
         public static object ParseInteger(string text, int b) {
-            if (TryParseInteger(text.AsSpan(), b, false, out object val)) {
+            if (TryParseInteger(text, b, false, out object val)) {
                 return val;
             }
             throw new ValueErrorException($"invalid literal with base {b}: {text}");

src/core/IronPython/Runtime/Operations/PythonOps.cs

@@ -3689,10 +3689,6 @@ internal static string MakeString(this IList<byte> bytes, int startIdx, int maxB
             return StringOps.Latin1Encoding.GetString(byteArr, startIdx, maxBytes);
         }
 
-        internal static string MakeString(this Span<byte> bytes) {
-            return MakeString((ReadOnlySpan<byte>)bytes);
-        }
-
         internal static string MakeString(this ReadOnlySpan<byte> bytes) {
             if (bytes.IsEmpty) {
                 return string.Empty;