Nullable: String (#23450)

1 files changed, 64 insertions, 63 deletions

diff --git a/src/System.Private.CoreLib/shared/System/String.Manipulation.cs b/src/System.Private.CoreLib/shared/System/String.Manipulation.cs
index 82d74225c2..bd56d0c33a 100644
--- a/src/System.Private.CoreLib/shared/System/String.Manipulation.cs
+++ b/src/System.Private.CoreLib/shared/System/String.Manipulation.cs
@@ -2,6 +2,7 @@
 // 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.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -33,7 +34,7 @@ namespace System
             }
         }
 
-        public static string Concat(object arg0)
+        public static string Concat(object? arg0)
         {
             if (arg0 == null)
             {
@@ -42,7 +43,7 @@ namespace System
             return arg0.ToString();
         }
 
-        public static string Concat(object arg0, object arg1)
+        public static string Concat(object? arg0, object? arg1)
         {
             if (arg0 == null)
             {
@@ -56,7 +57,7 @@ namespace System
             return Concat(arg0.ToString(), arg1.ToString());
         }
 
-        public static string Concat(object arg0, object arg1, object arg2)
+        public static string Concat(object? arg0, object? arg1, object? arg2)
         {
             if (arg0 == null)
             {
@@ -76,7 +77,7 @@ namespace System
             return Concat(arg0.ToString(), arg1.ToString(), arg2.ToString());
         }
 
-        public static string Concat(params object[] args)
+        public static string Concat(params object?[] args)
         {
             if (args == null)
             {
@@ -105,7 +106,7 @@ namespace System
 
             for (int i = 0; i < args.Length; i++)
             {
-                object value = args[i];
+                object? value = args[i];
 
                 string toString = value?.ToString() ?? string.Empty; // We need to handle both the cases when value or value.ToString() is null
                 strings[i] = toString;
@@ -195,7 +196,7 @@ namespace System
                     // Everything should be called in the order
                     // MoveNext-Current-ToString, unless further optimizations
                     // can be made, to avoid breaking changes
-                    string firstString = currentValue?.ToString();
+                    string? firstString = currentValue?.ToString();
 
                     // If there's only 1 item, simply call ToString on that
                     if (!en.MoveNext())
@@ -225,17 +226,17 @@ namespace System
             }
         }
 
-        public static string Concat(IEnumerable<string> values)
+        public static string Concat(IEnumerable<string?> values)
         {
             if (values == null)
                 throw new ArgumentNullException(nameof(values));
 
-            using (IEnumerator<string> en = values.GetEnumerator())
+            using (IEnumerator<string?> en = values.GetEnumerator())
             {
                 if (!en.MoveNext())
                     return string.Empty;
 
-                string firstValue = en.Current;
+                string? firstValue = en.Current;
 
                 if (!en.MoveNext())
                 {
@@ -255,7 +256,7 @@ namespace System
             }
         }
 
-        public static string Concat(string str0, string str1)
+        public static string Concat(string? str0, string? str1)
         {
             if (IsNullOrEmpty(str0))
             {
@@ -281,7 +282,7 @@ namespace System
             return result;
         }
 
-        public static string Concat(string str0, string str1, string str2)
+        public static string Concat(string? str0, string? str1, string? str2)
         {
             if (IsNullOrEmpty(str0))
             {
@@ -308,7 +309,7 @@ namespace System
             return result;
         }
 
-        public static string Concat(string str0, string str1, string str2, string str3)
+        public static string Concat(string? str0, string? str1, string? str2, string? str3)
         {
             if (IsNullOrEmpty(str0))
             {
@@ -405,7 +406,7 @@ namespace System
             return result;
         }
 
-        public static string Concat(params string[] values)
+        public static string Concat(params string?[] values)
         {
             if (values == null)
                 throw new ArgumentNullException(nameof(values));
@@ -428,7 +429,7 @@ namespace System
             long totalLengthLong = 0;
             for (int i = 0; i < values.Length; i++)
             {
-                string value = values[i];
+                string? value = values[i];
                 if (value != null)
                 {
                     totalLengthLong += value.Length;
@@ -451,7 +452,7 @@ namespace System
             int copiedLength = 0;
             for (int i = 0; i < values.Length; i++)
             {
-                string value = values[i];
+                string? value = values[i];
                 if (!string.IsNullOrEmpty(value))
                 {
                     int valueLen = value.Length;
@@ -470,25 +471,25 @@ namespace System
             // something changed concurrently to mutate the input array: fall back to
             // doing the concatenation again, but this time with a defensive copy. This
             // fall back should be extremely rare.
-            return copiedLength == totalLength ? result : Concat((string[])values.Clone());
+            return copiedLength == totalLength ? result : Concat((string?[])values.Clone());
         }
 
-        public static string Format(string format, object arg0)
+        public static string Format(string format, object? arg0)
         {
             return FormatHelper(null, format, new ParamsArray(arg0));
         }
 
-        public static string Format(string format, object arg0, object arg1)
+        public static string Format(string format, object? arg0, object? arg1)
         {
             return FormatHelper(null, format, new ParamsArray(arg0, arg1));
         }
 
-        public static string Format(string format, object arg0, object arg1, object arg2)
+        public static string Format(string format, object? arg0, object? arg1, object? arg2)
         {
             return FormatHelper(null, format, new ParamsArray(arg0, arg1, arg2));
         }
 
-        public static string Format(string format, params object[] args)
+        public static string Format(string format, params object?[] args)
         {
             if (args == null)
             {
@@ -500,22 +501,22 @@ namespace System
             return FormatHelper(null, format, new ParamsArray(args));
         }
 
-        public static string Format(IFormatProvider provider, string format, object arg0)
+        public static string Format(IFormatProvider? provider, string format, object? arg0)
         {
             return FormatHelper(provider, format, new ParamsArray(arg0));
         }
 
-        public static string Format(IFormatProvider provider, string format, object arg0, object arg1)
+        public static string Format(IFormatProvider? provider, string format, object? arg0, object? arg1)
         {
             return FormatHelper(provider, format, new ParamsArray(arg0, arg1));
         }
 
-        public static string Format(IFormatProvider provider, string format, object arg0, object arg1, object arg2)
+        public static string Format(IFormatProvider? provider, string format, object? arg0, object? arg1, object? arg2)
         {
             return FormatHelper(provider, format, new ParamsArray(arg0, arg1, arg2));
         }
 
-        public static string Format(IFormatProvider provider, string format, params object[] args)
+        public static string Format(IFormatProvider? provider, string format, params object?[] args)
         {
             if (args == null)
             {
@@ -527,7 +528,7 @@ namespace System
             return FormatHelper(provider, format, new ParamsArray(args));
         }
 
-        private static string FormatHelper(IFormatProvider provider, string format, ParamsArray args)
+        private static string FormatHelper(IFormatProvider? provider, string format, ParamsArray args)
         {
             if (format == null)
                 throw new ArgumentNullException(nameof(format));
@@ -574,7 +575,7 @@ namespace System
             return result;
         }
 
-        public static string Join(char separator, params string[] value)
+        public static string Join(char separator, params string?[] value)
         {
             if (value == null)
             {
@@ -584,7 +585,7 @@ namespace System
             return Join(separator, value, 0, value.Length);
         }
 
-        public static unsafe string Join(char separator, params object[] values)
+        public static unsafe string Join(char separator, params object?[] values)
         {
             // Defer argument validation to the internal function
             return JoinCore(&separator, 1, values);
@@ -596,7 +597,7 @@ namespace System
             return JoinCore(&separator, 1, values);
         }
 
-        public static unsafe string Join(char separator, string[] value, int startIndex, int count)
+        public static unsafe string Join(char separator, string?[] value, int startIndex, int count)
         {
             // Defer argument validation to the internal function
             return JoinCore(&separator, 1, value, startIndex, count);
@@ -604,7 +605,7 @@ namespace System
 
         // Joins an array of strings together as one string with a separator between each original string.
         //
-        public static string Join(string separator, params string[] value)
+        public static string Join(string? separator, params string?[] value)
         {
             if (value == null)
             {
@@ -613,7 +614,7 @@ namespace System
             return Join(separator, value, 0, value.Length);
         }
 
-        public static unsafe string Join(string separator, params object[] values)
+        public static unsafe string Join(string? separator, params object?[] values)
         {
             separator = separator ?? string.Empty;
             fixed (char* pSeparator = &separator._firstChar)
@@ -623,7 +624,7 @@ namespace System
             }
         }
 
-        public static unsafe string Join<T>(string separator, IEnumerable<T> values)
+        public static unsafe string Join<T>(string? separator, IEnumerable<T> values)
         {
             separator = separator ?? string.Empty;
             fixed (char* pSeparator = &separator._firstChar)
@@ -633,7 +634,7 @@ namespace System
             }
         }
 
-        public static string Join(string separator, IEnumerable<string> values)
+        public static string Join(string? separator, IEnumerable<string> values)
         {
             if (values == null)
             {
@@ -672,7 +673,7 @@ namespace System
 
         // Joins an array of strings together as one string with a separator between each original string.
         //
-        public static unsafe string Join(string separator, string[] value, int startIndex, int count)
+        public static unsafe string Join(string? separator, string?[] value, int startIndex, int count)
         {
             separator = separator ?? string.Empty;
             fixed (char* pSeparator = &separator._firstChar)
@@ -682,7 +683,7 @@ namespace System
             }
         }
 
-        private static unsafe string JoinCore(char* separator, int separatorLength, object[] values)
+        private static unsafe string JoinCore(char* separator, int separatorLength, object?[] values)
         {
             if (values == null)
             {
@@ -694,7 +695,7 @@ namespace System
                 return string.Empty;
             }
 
-            string firstString = values[0]?.ToString();
+            string? firstString = values[0]?.ToString();
 
             if (values.Length == 1)
             {
@@ -707,7 +708,7 @@ namespace System
             for (int i = 1; i < values.Length; i++)
             {
                 result.Append(separator, separatorLength);
-                object value = values[i];
+                object? value = values[i];
                 if (value != null)
                 {
                     result.Append(value.ToString());
@@ -739,7 +740,7 @@ namespace System
                 // Everything should be called in the order
                 // MoveNext-Current-ToString, unless further optimizations
                 // can be made, to avoid breaking changes
-                string firstString = currentValue?.ToString();
+                string? firstString = currentValue?.ToString();
 
                 // If there's only 1 item, simply call ToString on that
                 if (!en.MoveNext())
@@ -769,7 +770,7 @@ namespace System
             }
         }
 
-        private static unsafe string JoinCore(char* separator, int separatorLength, string[] value, int startIndex, int count)
+        private static unsafe string JoinCore(char* separator, int separatorLength, string?[] value, int startIndex, int count)
         {
             // If the separator is null, it is converted to an empty string before entering this function.
             // Even for empty strings, fixed should never return null (it should return a pointer to a null char).
@@ -810,7 +811,7 @@ namespace System
             // Calculate the length of the resultant string so we know how much space to allocate.
             for (int i = startIndex, end = startIndex + count; i < end; i++)
             {
-                string currentValue = value[i];
+                string? currentValue = value[i];
                 if (currentValue != null)
                 {
                     totalLength += currentValue.Length;
@@ -833,7 +834,7 @@ namespace System
 
                 // We range check again to avoid buffer overflows if this happens.
 
-                string currentValue = value[i];
+                string? currentValue = value[i];
                 if (currentValue != null)
                 {
                     int valueLen = currentValue.Length;
@@ -875,7 +876,7 @@ namespace System
             // fall back should be extremely rare.
             return copiedLength == totalLength ?
                 result :
-                JoinCore(separator, separatorLength, (string[])value.Clone(), startIndex, count);
+                JoinCore(separator, separatorLength, (string?[])value.Clone(), startIndex, count);
         }
 
         public string PadLeft(int totalWidth) => PadLeft(totalWidth, ' ');
@@ -973,12 +974,12 @@ namespace System
             return Substring(0, startIndex);
         }
 
-        public string Replace(string oldValue, string newValue, bool ignoreCase, CultureInfo culture)
+        public string Replace(string oldValue, string? newValue, bool ignoreCase, CultureInfo? culture)
         {
             return ReplaceCore(oldValue, newValue, culture, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
         }
 
-        public string Replace(string oldValue, string newValue, StringComparison comparisonType)
+        public string Replace(string oldValue, string? newValue, StringComparison comparisonType)
         {
             switch (comparisonType)
             {
@@ -1001,7 +1002,7 @@ namespace System
             }
         }
 
-        private unsafe string ReplaceCore(string oldValue, string newValue, CultureInfo culture, CompareOptions options)
+        private unsafe string ReplaceCore(string oldValue, string? newValue, CultureInfo? culture, CompareOptions options)
         {
             if (oldValue == null)
                 throw new ArgumentNullException(nameof(oldValue));
@@ -1121,7 +1122,7 @@ namespace System
             }
         }
 
-        public string Replace(string oldValue, string newValue)
+        public string Replace(string oldValue, string? newValue)
         {
             if (oldValue == null)
                 throw new ArgumentNullException(nameof(oldValue));
@@ -1232,7 +1233,7 @@ namespace System
         // If the separator is null
         // whitespace (i.e., Character.IsWhitespace) is used as the separator.
         //
-        public string[] Split(params char[] separator)
+        public string[] Split(params char[]? separator)
         {
             return SplitInternal(separator, int.MaxValue, StringSplitOptions.None);
         }
@@ -1248,17 +1249,17 @@ namespace System
         // If there are more than count different strings, the last n-(count-1)
         // elements are concatenated and added as the last string.
         //
-        public string[] Split(char[] separator, int count)
+        public string[] Split(char[]? separator, int count)
         {
             return SplitInternal(separator, count, StringSplitOptions.None);
         }
 
-        public string[] Split(char[] separator, StringSplitOptions options)
+        public string[] Split(char[]? separator, StringSplitOptions options)
         {
             return SplitInternal(separator, int.MaxValue, options);
         }
 
-        public string[] Split(char[] separator, int count, StringSplitOptions options)
+        public string[] Split(char[]? separator, int count, StringSplitOptions options)
         {
             return SplitInternal(separator, count, options);
         }
@@ -1305,27 +1306,27 @@ namespace System
             return result;
         }
 
-        public string[] Split(string separator, StringSplitOptions options = StringSplitOptions.None)
+        public string[] Split(string? separator, StringSplitOptions options = StringSplitOptions.None)
         {
             return SplitInternal(separator ?? string.Empty, null, int.MaxValue, options);
         }
 
-        public string[] Split(string separator, int count, StringSplitOptions options = StringSplitOptions.None)
+        public string[] Split(string? separator, int count, StringSplitOptions options = StringSplitOptions.None)
         {
             return SplitInternal(separator ?? string.Empty, null, count, options);
         }
 
-        public string[] Split(string[] separator, StringSplitOptions options)
+        public string[] Split(string[]? separator, StringSplitOptions options)
         {
             return SplitInternal(null, separator, int.MaxValue, options);
         }
 
-        public string[] Split(string[] separator, int count, StringSplitOptions options)
+        public string[] Split(string[]? separator, int count, StringSplitOptions options)
         {
             return SplitInternal(null, separator, count, options);
         }
 
-        private string[] SplitInternal(string separator, string[] separators, int count, StringSplitOptions options)
+        private string[] SplitInternal(string? separator, string?[]? separators, int count, StringSplitOptions options)
         {
             if (count < 0)
             {
@@ -1344,7 +1345,7 @@ namespace System
 
             if (!singleSeparator && (separators == null || separators.Length == 0))
             {
-                return SplitInternal((char[])null, count, options);
+                return SplitInternal(default(ReadOnlySpan<char>), count, options);
             }
 
             if ((count == 0) || (omitEmptyEntries && Length == 0))
@@ -1352,14 +1353,14 @@ namespace System
                 return Array.Empty<string>();
             }
 
-            if (count == 1 || (singleSeparator && separator.Length == 0))
+            if (count == 1 || (singleSeparator && separator!.Length == 0))
             {
                 return new string[] { this };
             }
 
             if (singleSeparator)
             {
-                return SplitInternal(separator, count, options);
+                return SplitInternal(separator!, count, options);
             }
 
             Span<int> sepListInitialSpan = stackalloc int[StackallocIntBufferSizeLimit];
@@ -1368,7 +1369,7 @@ namespace System
             Span<int> lengthListInitialSpan = stackalloc int[StackallocIntBufferSizeLimit];
             var lengthListBuilder = new ValueListBuilder<int>(lengthListInitialSpan);
 
-            MakeSeparatorList(separators, ref sepListBuilder, ref lengthListBuilder);
+            MakeSeparatorList(separators!, ref sepListBuilder, ref lengthListBuilder);
             ReadOnlySpan<int> sepList = sepListBuilder.AsSpan();
             ReadOnlySpan<int> lengthList = lengthListBuilder.AsSpan();
 
@@ -1616,7 +1617,7 @@ namespace System
         /// <param name="separators">separator strngs</param>
         /// <param name="sepListBuilder"><see cref="ValueListBuilder{T}"/> for separator indexes</param>
         /// <param name="lengthListBuilder"><see cref="ValueListBuilder{T}"/> for separator length values</param>
-        private void MakeSeparatorList(string[] separators, ref ValueListBuilder<int> sepListBuilder, ref ValueListBuilder<int> lengthListBuilder)
+        private void MakeSeparatorList(string?[] separators, ref ValueListBuilder<int> sepListBuilder, ref ValueListBuilder<int> lengthListBuilder)
         {
             Debug.Assert(separators != null && separators.Length > 0, "separators != null && separators.Length > 0");
 
@@ -1626,7 +1627,7 @@ namespace System
             {
                 for (int j = 0; j < separators.Length; j++)
                 {
-                    string separator = separators[j];
+                    string? separator = separators[j];
                     if (IsNullOrEmpty(separator))
                     {
                         continue;
@@ -1768,7 +1769,7 @@ namespace System
         public unsafe string Trim(char trimChar) => TrimHelper(&trimChar, 1, TrimType.Both);
 
         // Removes a set of characters from the beginning and end of this string.
-        public unsafe string Trim(params char[] trimChars)
+        public unsafe string Trim(params char[]? trimChars)
         {
             if (trimChars == null || trimChars.Length == 0)
             {
@@ -1787,7 +1788,7 @@ namespace System
         public unsafe string TrimStart(char trimChar) => TrimHelper(&trimChar, 1, TrimType.Head);
 
         // Removes a set of characters from the beginning of this string.
-        public unsafe string TrimStart(params char[] trimChars)
+        public unsafe string TrimStart(params char[]? trimChars)
         {
             if (trimChars == null || trimChars.Length == 0)
             {
@@ -1806,7 +1807,7 @@ namespace System
         public unsafe string TrimEnd(char trimChar) => TrimHelper(&trimChar, 1, TrimType.Tail);
 
         // Removes a set of characters from the end of this string.
-        public unsafe string TrimEnd(params char[] trimChars)
+        public unsafe string TrimEnd(params char[]? trimChars)
         {
             if (trimChars == null || trimChars.Length == 0)
             {