Revert "Replace a few stackallocs with collection expressions (#105121)…

…" (#105128)

This reverts commit 87cd893.

src/libraries/Common/src/Extensions/Logging/DebuggerDisplayFormatting.cs

@@ -31,15 +31,15 @@ internal static string DebuggerToString(string name, ILogger logger)
 
         internal static LogLevel? CalculateEnabledLogLevel(ILogger logger)
         {
-            ReadOnlySpan<LogLevel> logLevels =
-            [
+            ReadOnlySpan<LogLevel> logLevels = stackalloc LogLevel[]
+            {
                 LogLevel.Critical,
                 LogLevel.Error,
                 LogLevel.Warning,
                 LogLevel.Information,
                 LogLevel.Debug,
                 LogLevel.Trace,
-            ];
+            };
 
             LogLevel? minimumLevel = null;
 

src/libraries/Common/src/System/Net/Security/MD4.cs

@@ -66,10 +66,9 @@ internal static void HashData(ReadOnlySpan<byte> source, Span<byte> destination)
 
             Span<byte> buffer = stackalloc byte[64];
             buffer.Clear();
-
             // Initialize the context
-            Span<uint> state = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476];
-            Span<uint> count = [0, 0];
+            Span<uint> state = stackalloc uint[4] { 0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476 };
+            Span<uint> count = stackalloc uint[2] { 0, 0 };
 
             HashCore(source, state, count, buffer);
 

src/libraries/Microsoft.Bcl.Cryptography/src/System/Security/Cryptography/SP800108HmacCounterKdfImplementationCng.cs

@@ -38,7 +38,7 @@ internal unsafe SP800108HmacCounterKdfImplementationCng(ReadOnlySpan<byte> key,
             else
             {
                 // CNG requires a non-null pointer even when the length is zero.
-                symmetricKeyMaterial = [0];
+                symmetricKeyMaterial = stackalloc byte[] { 0 };
                 symmetricKeyMaterialLength = 0;
             }
 
@@ -82,7 +82,7 @@ internal unsafe SP800108HmacCounterKdfImplementationCng(byte[] key, HashAlgorith
             else
             {
                 // CNG requires a non-null pointer even when the length is zero.
-                symmetricKeyMaterial = [0];
+                symmetricKeyMaterial = stackalloc byte[] { 0 };
                 symmetricKeyMaterialLength = 0;
             }
 

src/libraries/Microsoft.Extensions.Logging/src/Logger.cs

@@ -238,15 +238,15 @@ private sealed class LoggerProviderDebugView(string providerName, MessageLogger?
                     return null;
                 }
 
-                ReadOnlySpan<LogLevel> logLevels =
-                [
+                ReadOnlySpan<LogLevel> logLevels = stackalloc LogLevel[]
+                {
                     LogLevel.Critical,
                     LogLevel.Error,
                     LogLevel.Warning,
                     LogLevel.Information,
                     LogLevel.Debug,
                     LogLevel.Trace,
-                ];
+                };
 
                 LogLevel? minimumLevel = null;
 

src/libraries/System.Private.CoreLib/src/System/StartupHookProvider.cs

@@ -85,13 +85,13 @@ private static unsafe void CallStartupHook(char* pStartupHookPart)
 
         private static void ParseStartupHook(ref StartupHookNameOrPath startupHook, string startupHookPart)
         {
-            ReadOnlySpan<char> disallowedSimpleAssemblyNameChars =
-            [
+            ReadOnlySpan<char> disallowedSimpleAssemblyNameChars = stackalloc char[4]
+            {
                 Path.DirectorySeparatorChar,
                 Path.AltDirectorySeparatorChar,
                 ' ',
                 ','
-            ];
+            };
 
             if (string.IsNullOrEmpty(startupHookPart))
             {

src/libraries/System.Private.DataContractSerialization/src/System/Xml/XmlBufferReader.cs

@@ -396,13 +396,13 @@ public decimal ReadDecimal()
             {
                 byte[] buffer = GetBuffer(ValueHandleLength.Decimal, out int offset);
                 ReadOnlySpan<byte> bytes = buffer.AsSpan(offset, sizeof(decimal));
-                ReadOnlySpan<int> span =
-                [
+                ReadOnlySpan<int> span = stackalloc int[4]
+                {
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(8, 4)),
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(12, 4)),
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(4, 4)),
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(0, 4))
-                ];
+                };
 
                 Advance(ValueHandleLength.Decimal);
                 return new decimal(span);
@@ -975,13 +975,13 @@ public decimal GetDecimal(int offset)
             else
             {
                 ReadOnlySpan<byte> bytes = _buffer.AsSpan(offset, sizeof(decimal));
-                ReadOnlySpan<int> span =
-                [
+                ReadOnlySpan<int> span = stackalloc int[4]
+                {
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(8, 4)),
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(12, 4)),
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(4, 4)),
                     BinaryPrimitives.ReadInt32LittleEndian(bytes.Slice(0, 4))
-                ];
+                };
 
                 return new decimal(span);
             }

src/libraries/System.Security.Cryptography.Cose/src/System/Security/Cryptography/Cose/CoseHelpers.cs

@@ -47,12 +47,12 @@ internal static void WriteByteStringLength(IncrementalHash hasher, ulong value)
             if (value < (byte)CborAdditionalInfo.Additional8BitData)
             {
                 initialByte = new CborInitialByte(MajorType, (CborAdditionalInfo)value);
-                hasher.AppendData([initialByte.InitialByte]);
+                hasher.AppendData(stackalloc byte[] { initialByte.InitialByte });
             }
             else if (value <= byte.MaxValue)
             {
                 initialByte = new CborInitialByte(MajorType, CborAdditionalInfo.Additional8BitData);
-                hasher.AppendData([initialByte.InitialByte, (byte)value]);
+                hasher.AppendData(stackalloc byte[] { initialByte.InitialByte, (byte)value });
             }
             else if (value <= ushort.MaxValue)
             {

src/libraries/System.Security.Cryptography.Pkcs/src/System/Security/Cryptography/Pkcs/CmsSignature.RSA.cs

@@ -186,7 +186,9 @@ protected override RSASignaturePadding GetSignaturePadding(
                     return RSASignaturePadding.Pkcs1;
                 }
 
-                ReadOnlySpan<byte> expectedParameters = [0x05, 0x00];
+                Span<byte> expectedParameters = stackalloc byte[2];
+                expectedParameters[0] = 0x05;
+                expectedParameters[1] = 0x00;
 
                 if (expectedParameters.SequenceEqual(signatureParameters.Value.Span))
                 {

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/Pbkdf2Implementation.Windows.cs

@@ -60,7 +60,8 @@ private static unsafe void FillKeyDerivation(
             if (password.IsEmpty)
             {
                 // CNG won't accept a null pointer for the password.
-                symmetricKeyMaterial = [0];
+                symmetricKeyMaterial = stackalloc byte[1];
+                symmetricKeyMaterialLength = 0;
                 clearSpan = default;
             }
             else if (password.Length <= hashBlockSizeBytes)

src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/DefaultJavaScriptEncoder.cs

@@ -31,9 +31,9 @@ private DefaultJavaScriptEncoder(TextEncoderSettings settings, bool allowMinimal
 
             _innerEncoder = allowMinimalJsonEscaping
                 ? new OptimizedInboxTextEncoder(EscaperImplementation.SingletonMinimallyEscaped, settings.GetAllowedCodePointsBitmap(), forbidHtmlSensitiveCharacters: false,
-                    extraCharactersToEscape: ['\"', '\\'])
+                    extraCharactersToEscape: stackalloc char[] { '\"', '\\' })
                 : new OptimizedInboxTextEncoder(EscaperImplementation.Singleton, settings.GetAllowedCodePointsBitmap(), forbidHtmlSensitiveCharacters: true,
-                    extraCharactersToEscape: ['\\', '`']);
+                    extraCharactersToEscape: stackalloc char[] { '\\', '`' });
         }
 
         public override int MaxOutputCharactersPerInputCharacter => 6; // "\uXXXX" for a single char ("\uXXXX\uYYYY" [12 chars] for supplementary scalar value)

src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/DefaultUrlEncoder.cs

@@ -64,7 +64,7 @@ internal DefaultUrlEncoder(TextEncoderSettings settings)
             // Basic Latin set is:
             // ALPHA / DIGIT / "-" / "." / "_" / "~" / "!" / "$" / "(" / ")" / "*" / "," / ";" / "@"
 
-            _innerEncoder = new OptimizedInboxTextEncoder(EscaperImplementation.Singleton, settings.GetAllowedCodePointsBitmap(), extraCharactersToEscape: [
+            _innerEncoder = new OptimizedInboxTextEncoder(EscaperImplementation.Singleton, settings.GetAllowedCodePointsBitmap(), extraCharactersToEscape: stackalloc char[] {
                 ' ', // chars from Basic Latin which aren't already disallowed by the base encoder
                 '#',
                 '%',
@@ -96,7 +96,7 @@ internal DefaultUrlEncoder(TextEncoderSettings settings)
                 '\uFFFD',
                 '\uFFFE',
                 '\uFFFF',
-            ]);
+            });
         }
 
         public override int MaxOutputCharactersPerInputCharacter => 9; // "%XX%YY%ZZ" for a single char ("%XX%YY%ZZ%WW" [12 chars] for supplementary scalar value)

src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.Ascii.cs

@@ -87,7 +87,7 @@ internal void PopulatePreescapedData(in AllowedBmpCodePointsBitmap allowedCodePo
             {
                 this = default; // clear all existing data
 
-                Span<char> tempBuffer = ['\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0'];
+                Span<char> tempBuffer = stackalloc char[8] { '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0' };
                 for (int i = 0; i < 128; i++)
                 {
                     ulong thisPreescapedData;

src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexCharClass.cs

@@ -1541,7 +1541,7 @@ private static RegexCharClass ParseRecursive(string charClass, int start)
         /// <param name="c">The character for which to create the set.</param>
         /// <returns>The create set string.</returns>
         public static string OneToStringClass(char c)
-            => CharsToStringClass([c]);
+            => CharsToStringClass(stackalloc char[1] { c });
 
         internal static unsafe string CharsToStringClass(ReadOnlySpan<char> chars)
         {