refactor: unify range-indexer style across netstandard2.0 surface

src/ANcpLua.AotReflection/ANcpLua.Analyzers.AotReflection.csproj

@@ -43,6 +43,8 @@
     <!-- Polyfills from core Roslyn.Utilities (internal, must be linked per-project) -->
     <ItemGroup>
         <Compile Include="..\ANcpLua.Roslyn.Utilities\Polyfills\LanguageFeatures\IsExternalInit.cs" Link="Polyfills\IsExternalInit.cs"/>
+        <Compile Include="..\ANcpLua.Roslyn.Utilities\Polyfills\IndexRange\Index.cs" Link="Polyfills\Index.cs"/>
+        <Compile Include="..\ANcpLua.Roslyn.Utilities\Polyfills\IndexRange\Range.cs" Link="Polyfills\Range.cs"/>
     </ItemGroup>
 
     <ItemGroup>

src/ANcpLua.AotReflection/Generation/GenerationHelpers.cs

@@ -27,7 +27,7 @@ public static (string Namespace, string Name) GetNamespaceAndName(string fullyQu
 
         return lastDotIndex <= 0
             ? (string.Empty, type)
-            : (type.Substring(0, lastDotIndex), type.Substring(lastDotIndex + 1));
+            : (type[..lastDotIndex], type[(lastDotIndex + 1)..]);
     }
 
     public static string GetTypeOf(string fullyQualifiedType)
@@ -38,7 +38,7 @@ public static string GetTypeOf(string fullyQualifiedType)
     private static string RemoveGlobalPrefix(string fullyQualifiedType)
     {
         return fullyQualifiedType.StartsWith(GlobalPrefix, StringComparison.Ordinal)
-            ? fullyQualifiedType.Substring(GlobalPrefix.Length)
+            ? fullyQualifiedType[GlobalPrefix.Length..]
             : fullyQualifiedType;
     }
 }

src/ANcpLua.Roslyn.Utilities/Http/BearerHeader.cs

@@ -28,7 +28,7 @@ public static bool TryExtract(string? headerValue, out string? token)
         token = null;
         if (string.IsNullOrWhiteSpace(headerValue)) return false;
         if (!headerValue!.StartsWith(Scheme, StringComparison.OrdinalIgnoreCase)) return false;
-        var candidate = headerValue.Substring(Scheme.Length).Trim();
+        var candidate = headerValue[Scheme.Length..].Trim();
         if (candidate.Length == 0) return false;
         token = candidate;
         return true;

src/ANcpLua.Roslyn.Utilities/Ids/ShortId.cs

@@ -44,7 +44,7 @@ public static string NewHex(int hexChars)
         if (hexChars is < 1 or > 32)
             throw new ArgumentOutOfRangeException(nameof(hexChars), hexChars, "Must be 1–32.");
 
-        return Guid.NewGuid().ToString("N").Substring(0, hexChars);
+        return Guid.NewGuid().ToString("N")[..hexChars];
     }
 
     /// <summary>
@@ -101,7 +101,7 @@ public static string NewPrefixedSortable(string prefix, int randomHexChars = 24)
         var hex = BitConverter.ToString(buffer).Replace("-", "").ToLowerInvariant();
 #endif
 
-        return prefix + "-" + hex.Substring(0, randomHexChars);
+        return prefix + "-" + hex[..randomHexChars];
     }
 
     /// <summary>

src/ANcpLua.Roslyn.Utilities/OTel/SemconvVersion.cs

@@ -25,7 +25,7 @@ public static bool TryParse(string? value, out int major, out int minor, out int
         if (string.IsNullOrEmpty(value)) return false;
         if (!value!.StartsWith(Prefix, StringComparison.OrdinalIgnoreCase)) return false;
 
-        var parts = value.Substring(Prefix.Length).Split('.');
+        var parts = value[Prefix.Length..].Split('.');
         if (parts.Length < 2) return false;
         if (!int.TryParse(parts[0], NumberStyles.Integer, CultureInfo.InvariantCulture, out major)) return false;
         if (!int.TryParse(parts[1], NumberStyles.Integer, CultureInfo.InvariantCulture, out minor)) return false;

src/ANcpLua.Roslyn.Utilities/StringExtensions.cs

@@ -618,7 +618,7 @@ public static string UnwrapNullable(this string typeFqn, bool unwrap = true)
         var normalized = typeFqn.NormalizeTypeName();
         if (normalized.StartsWith("System.Nullable<", StringComparison.Ordinal) &&
             normalized.EndsWith(">", StringComparison.Ordinal))
-            return normalized.Substring("System.Nullable<".Length, normalized.Length - "System.Nullable<".Length - 1);
+            return normalized["System.Nullable<".Length..^1];
 
         return typeFqn;
     }
@@ -785,7 +785,7 @@ public static string ToShortHash(this string input)
 
 #if NET5_0_OR_GREATER
         var hash = SHA256.HashData(Encoding.UTF8.GetBytes(input));
-        return Convert.ToHexString(hash).Substring(0, 8);
+        return Convert.ToHexString(hash)[..8];
 #else
         using var sha256 = SHA256.Create();
         var hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(input));
@@ -823,14 +823,14 @@ public static string ToShortHash(this string input, int hexChars, bool lowercase
 #if NET5_0_OR_GREATER
         var hash = SHA256.HashData(Encoding.UTF8.GetBytes(input));
         var hex = Convert.ToHexString(hash);
-        return (lowercase ? hex.ToLowerInvariant() : hex).Substring(0, hexChars);
+        return (lowercase ? hex.ToLowerInvariant() : hex)[..hexChars];
 #else
         using var sha256 = SHA256.Create();
         var hash = sha256.ComputeHash(Encoding.UTF8.GetBytes(input));
         var needBytes = (hexChars + 1) / 2;
         var hex = BitConverter.ToString(hash, 0, needBytes).Replace("-", "");
         if (lowercase) hex = hex.ToLowerInvariant();
-        return hex.Substring(0, hexChars);
+        return hex[..hexChars];
 #endif
     }
 

src/ANcpLua.Roslyn.Utilities/SyntaxExtensions.cs

@@ -543,7 +543,7 @@ public static string ToGlobalTypeName(this string typeName, IReadOnlyList<string
         if (genericStart > 0 && typeName.EndsWithOrdinal(">"))
         {
             var baseTypeName = typeName[..genericStart];
-            var argsContent = typeName.Substring(genericStart + 1, typeName.Length - genericStart - 2);
+            var argsContent = typeName[(genericStart + 1)..^1];
 
             var args = ParseGenericArguments(argsContent);
             var qualifiedArgs = args.Select(a => a.ToGlobalTypeName(typeParameterNames));
@@ -621,7 +621,7 @@ private static IEnumerable<string> ParseGenericArguments(string argsContent)
                     depth--;
                     break;
                 case ',' when depth is 0:
-                    args.Add(argsContent.Substring(start, i - start).Trim());
+                    args.Add(argsContent[start..i].Trim());
                     start = i + 1;
                     break;
             }

src/ANcpLua.Roslyn.Utilities/Text/MarkdownText.cs

@@ -17,7 +17,7 @@ public static string TruncateCell(string? text, int maxLength = 50)
     {
         if (maxLength < 1) throw new ArgumentOutOfRangeException(nameof(maxLength), maxLength, "Must be at least 1.");
         if (string.IsNullOrEmpty(text)) return string.Empty;
-        return text!.Length <= maxLength ? text : text.Substring(0, maxLength - 1) + "…";
+        return text!.Length <= maxLength ? text : text[..(maxLength - 1)] + "…";
     }
 
     /// <summary>Escapes <c>|</c> and newlines so <paramref name="text" /> can be safely embedded in a markdown table cell.</summary>