Remove unnecessary extensions

Author: tmat

src/Compilers/CSharp/Portable/CommandLine/CommandLineDiagnosticFormatter.cs

@@ -71,7 +71,7 @@ internal string RelativizeNormalizedPath(string normalizedPath)
             if (PathUtilities.IsSameDirectoryOrChildOf(normalizedDirectory, normalizedBaseDirectory))
             {
                 return normalizedPath.Substring(
-                    PathUtilities.IsDirectorySeparator(normalizedBaseDirectory.Last())
+                    PathUtilities.IsDirectorySeparator(normalizedBaseDirectory[^1])
                         ? normalizedBaseDirectory.Length
                         : normalizedBaseDirectory.Length + 1);
             }

src/Compilers/CSharp/Portable/Syntax/SyntaxNormalizer.cs

@@ -927,8 +927,8 @@ private static bool NeedsSeparator(SyntaxToken token, SyntaxToken next)
             }
             else if (token.Width > 1 && next.Width > 1)
             {
-                var tokenLastChar = token.Text.Last();
-                var nextFirstChar = next.Text.First();
+                var tokenLastChar = token.Text[^1];
+                var nextFirstChar = next.Text[0];
                 if (tokenLastChar == nextFirstChar && TokenCharacterCanBeDoubled(tokenLastChar))
                 {
                     return true;
@@ -1251,7 +1251,7 @@ private static bool EndsInLineBreak(SyntaxTrivia trivia)
             if (trivia.Kind() == SyntaxKind.PreprocessingMessageTrivia || trivia.Kind() == SyntaxKind.DisabledTextTrivia)
             {
                 var text = trivia.ToFullString();
-                return text.Length > 0 && SyntaxFacts.IsNewLine(text.Last());
+                return text.Length > 0 && SyntaxFacts.IsNewLine(text[^1]);
             }
 
             if (trivia.HasStructure)

src/Compilers/Core/Portable/InternalUtilities/Hash.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;

src/Compilers/Core/Portable/InternalUtilities/RoslynString.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Diagnostics.CodeAnalysis;
 
 namespace Roslyn.Utilities

src/Compilers/Core/Portable/InternalUtilities/StringExtensions.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -13,6 +15,8 @@ namespace Roslyn.Utilities
 {
     internal static class StringExtensions
     {
+        private static readonly Func<char, char> s_toLower = char.ToLower;
+        private static readonly Func<char, char> s_toUpper = char.ToUpper;
         private static ImmutableArray<string> s_lazyNumerals;
         private static UTF8Encoding? s_lazyUtf8;
 
@@ -30,19 +34,7 @@ internal static string GetNumeral(int number)
         }
 
         public static string Join(this IEnumerable<string?> source, string separator)
-        {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
-
-            if (separator == null)
-            {
-                throw new ArgumentNullException(nameof(separator));
-            }
-
-            return string.Join(separator, source);
-        }
+            => string.Join(separator, source);
 
         public static bool LooksLikeInterfaceName(this string name)
         {
@@ -54,9 +46,6 @@ public static bool LooksLikeTypeParameterName(this string name)
             return name.Length >= 3 && name[0] == 'T' && char.IsUpper(name[1]) && char.IsLower(name[2]);
         }
 
-        private static readonly Func<char, char> s_toLower = char.ToLower;
-        private static readonly Func<char, char> s_toUpper = char.ToUpper;
-
         [return: NotNullIfNotNull(parameterName: nameof(shortName))]
         public static string? ToPascalCase(
             this string? shortName,
@@ -228,32 +217,6 @@ internal static string Unquote(this string arg, out bool quoted)
             }
         }
 
-        // String isn't IEnumerable<char> in the current Portable profile. 
-        internal static char First(this string arg)
-        {
-            return arg[0];
-        }
-
-        // String isn't IEnumerable<char> in the current Portable profile. 
-        internal static char Last(this string arg)
-        {
-            return arg[arg.Length - 1];
-        }
-
-        // String isn't IEnumerable<char> in the current Portable profile. 
-        internal static bool All(this string arg, Predicate<char> predicate)
-        {
-            foreach (char c in arg)
-            {
-                if (!predicate(c))
-                {
-                    return false;
-                }
-            }
-
-            return true;
-        }
-
         public static int GetCaseInsensitivePrefixLength(this string string1, string string2)
         {
             int x = 0;

src/Compilers/Core/Portable/SpecialTypeExtensions.cs

@@ -2,9 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Diagnostics;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis
 {

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Formatting/Engine/Trivia/TriviaDataFactory.CodeShapeAnalyzer.cs

@@ -310,7 +310,7 @@ private bool OnDisabledTextTrivia(SyntaxTrivia trivia, int index)
             if (trivia.IsKind(SyntaxKind.DisabledTextTrivia))
             {
                 var triviaString = trivia.ToString();
-                if (!string.IsNullOrEmpty(triviaString) && SyntaxFacts.IsNewLine(triviaString.Last()))
+                if (!string.IsNullOrEmpty(triviaString) && SyntaxFacts.IsNewLine(triviaString[^1]))
                 {
                     ResetStateAfterNewLine(index);
                 }

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Formatting/Engine/Trivia/TriviaDataFactory.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Diagnostics;
+using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Shared.Extensions;