Remove a few array allocations from enumeration (#118288)

Author: stephentoub

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/EnumConverter.cs

@@ -87,10 +87,9 @@ private static long GetEnumValue(bool isUnderlyingTypeUInt64, object enumVal, Cu
                     {
                         bool isUnderlyingTypeUInt64 = Enum.GetUnderlyingType(EnumType) == typeof(ulong);
                         long convertedValue = 0;
-                        string[] values = strValue.Split(',');
-                        foreach (string v in values)
+                        foreach (Range v in strValue.AsSpan().Split(','))
                         {
-                            convertedValue |= GetEnumValue(isUnderlyingTypeUInt64, Enum.Parse(EnumType, v, true), culture);
+                            convertedValue |= GetEnumValue(isUnderlyingTypeUInt64, Enum.Parse(EnumType, strValue.AsSpan(v), true), culture);
                         }
                         return Enum.ToObject(EnumType, convertedValue);
                     }

src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.Linux.cs

@@ -105,7 +105,7 @@ private static DateTime BootTime
         /// <summary>Gets execution path</summary>
         private static string? GetPathToOpenFile()
         {
-            string[] allowedProgramsToRun = { "xdg-open", "gnome-open", "kfmclient" };
+            ReadOnlySpan<string> allowedProgramsToRun = ["xdg-open", "gnome-open", "kfmclient"];
             foreach (var program in allowedProgramsToRun)
             {
                 string? pathToProgram = FindProgramInPath(program);

src/libraries/System.DirectoryServices.AccountManagement/src/System/DirectoryServices/AccountManagement/AD/ADStoreCtx_LoadStore.cs

@@ -602,15 +602,15 @@ private Principal FindPrincipalByIdentRefHelper(
                     // This is the tricky case.  They didn't specify a UrnScheme, so we need to
                     // try all of them.
 
-                    string[] urnSchemesToTry = new string[]
-                    {
+                    ReadOnlySpan<string> urnSchemesToTry =
+                    [
                         UrnScheme.SamAccountScheme,
                         UrnScheme.UpnScheme,
                         UrnScheme.DistinguishedNameScheme,
                         UrnScheme.SidScheme,
                         UrnScheme.GuidScheme,
                         UrnScheme.NameScheme
-                    };
+                    ];
 
                     StringBuilder innerLdapFilter = new StringBuilder();
 

src/libraries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/LinuxIPv4InterfaceProperties.cs

@@ -35,13 +35,13 @@ public LinuxIPv4InterfaceProperties(LinuxNetworkInterface linuxNetworkInterface)
 
         private bool GetIsForwardingEnabled()
         {
-            string[] paths = new string[]
-            {
+            ReadOnlySpan<string> paths =
+            [
                 // /proc/sys/net/ipv4/conf/<name>/forwarding
                 Path.Join(NetworkFiles.Ipv4ConfigFolder, _linuxNetworkInterface.Name, NetworkFiles.ForwardingFileName),
                 // Fall back to global forwarding config /proc/sys/net/ipv4/ip_forward
                 NetworkFiles.Ipv4GlobalForwardingFile
-            };
+            ];
 
             for (int i = 0; i < paths.Length; i++)
             {

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Unix.Android.cs

@@ -227,10 +227,10 @@ public AndroidTzData()
                 // On Android, time zone data is found in tzdata
                 // Based on https://github.com/mono/mono/blob/main/mcs/class/corlib/System/TimeZoneInfo.Android.cs
                 // Also follows the locations found at the bottom of https://github.com/aosp-mirror/platform_bionic/blob/master/libc/tzcode/bionic.cpp
-                string[] tzFileDirList = new string[] {GetApexTimeDataRoot() + "/etc/tz/", // Android 10+, TimeData module where the updates land
+                ReadOnlySpan<string> tzFileDirList = [ GetApexTimeDataRoot() + "/etc/tz/", // Android 10+, TimeData module where the updates land
                                                        GetApexRuntimeRoot() + "/etc/tz/", // Android 10+, Fallback location if the above isn't found or corrupted
                                                        Environment.GetEnvironmentVariable("ANDROID_DATA") + "/misc/zoneinfo/",
-                                                       Environment.GetEnvironmentVariable("ANDROID_ROOT") + DefaultTimeZoneDirectory};
+                                                       Environment.GetEnvironmentVariable("ANDROID_ROOT") + DefaultTimeZoneDirectory ];
                 foreach (var tzFileDir in tzFileDirList)
                 {
                     string tzFilePath = Path.Combine(tzFileDir, TimeZoneFileName);

src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/X509Certificates/CertificateHelpers.Windows.cs

@@ -101,7 +101,7 @@ private static bool TryGuessRsaKeySpec(CspParameters cspParameters, out int keyS
 
             // These are ordered in terms of perceived likeliness, given that the key
             // is AT_SIGNATURE.
-            int[] provTypes =
+            ReadOnlySpan<int> provTypes =
             [
                 PROV_RSA_FULL,
                 PROV_RSA_AES,
@@ -120,10 +120,8 @@ private static bool TryGuessRsaKeySpec(CspParameters cspParameters, out int keyS
                 {
                     using (new RSACryptoServiceProvider(cspParameters))
                     {
-                        {
-                            keySpec = cspParameters.KeyNumber;
-                            return true;
-                        }
+                        keySpec = cspParameters.KeyNumber;
+                        return true;
                     }
                 }
                 catch (CryptographicException)
@@ -141,7 +139,7 @@ private static bool TryGuessDsaKeySpec(CspParameters cspParameters, out int keyS
             const int PROV_DSS = 3;
             const int PROV_DSS_DH = 13;
 
-            int[] provTypes =
+            ReadOnlySpan<int> provTypes =
             [
                 PROV_DSS_DH,
                 PROV_DSS,
@@ -155,10 +153,8 @@ private static bool TryGuessDsaKeySpec(CspParameters cspParameters, out int keyS
                 {
                     using (new DSACryptoServiceProvider(cspParameters))
                     {
-                        {
-                            keySpec = cspParameters.KeyNumber;
-                            return true;
-                        }
+                        keySpec = cspParameters.KeyNumber;
+                        return true;
                     }
                 }
                 catch (CryptographicException)

src/libraries/System.Speech/src/Internal/ObjectToken/RegistryDataKey.cs

@@ -484,12 +484,13 @@ private static string GetFirstKeyAndParseRemainder(ref string registryPath)
 
         private static RegistryKey RegKeyFromRootPath(string rootPath)
         {
-            RegistryKey[] roots = new RegistryKey[] {
+            ReadOnlySpan<RegistryKey> roots =
+            [
                 Registry.ClassesRoot,
                 Registry.LocalMachine,
                 Registry.CurrentUser,
                 Registry.CurrentConfig
-            };
+            ];
 
             foreach (RegistryKey key in roots)
             {