Remove implicit string operator from Utf8String

src/coreclr/tools/Common/Compiler/NativeAotNameMangler.cs

@@ -268,7 +268,7 @@ private Utf8String ComputeMangledTypeName(TypeDesc type)
                         // This problem needs a better fix.
                         if (isSystemPrivate)
                             assemblyName = string.Concat("S.P.", assemblyName.AsSpan(15));
-                        Utf8String prependAssemblyName = SanitizeName(assemblyName);
+                        Utf8String prependAssemblyName = new Utf8String(SanitizeName(assemblyName));
 
                         var deduplicator = new HashSet<Utf8String>();
 
@@ -358,12 +358,12 @@ static void AppendTypeName(Utf8StringBuilder sb, MetadataType t)
                 case TypeFlags.ByRef:
                     mangledName = new Utf8StringBuilder()
                         .Append(GetMangledTypeName(((ByRefType)type).ParameterType))
-                        .Append(NestMangledName("ByRef")).ToUtf8String();
+                        .Append(NestMangledName(new Utf8String("ByRef"u8.ToArray()))).ToUtf8String();
                     break;
                 case TypeFlags.Pointer:
                     mangledName = new Utf8StringBuilder()
                         .Append(GetMangledTypeName(((PointerType)type).ParameterType))
-                        .Append(NestMangledName("Pointer")).ToUtf8String();
+                        .Append(NestMangledName(new Utf8String("Pointer"u8.ToArray()))).ToUtf8String();
                     break;
                 case TypeFlags.FunctionPointer:
                 {
@@ -408,17 +408,17 @@ static void AppendTypeName(Utf8StringBuilder sb, MetadataType t)
                     }
                     else if (type is IPrefixMangledMethod)
                     {
-                        mangledName = GetPrefixMangledMethodName((IPrefixMangledMethod)type).ToString();
+                        mangledName = GetPrefixMangledMethodName((IPrefixMangledMethod)type);
                     }
                     else if (type is IPrefixMangledType)
                     {
-                        mangledName = GetPrefixMangledTypeName((IPrefixMangledType)type).ToString();
+                        mangledName = GetPrefixMangledTypeName((IPrefixMangledType)type);
                     }
                     else
                     {
                         // This is a type definition. Since we didn't fall in the `is EcmaType` case above,
                         // it's likely a compiler-generated type.
-                        mangledName = SanitizeName(((DefType)type).GetFullName());
+                        mangledName = new Utf8String(SanitizeName(((DefType)type).GetFullName()));
                     }
                     break;
             }

src/coreclr/tools/Common/Internal/Text/Utf8String.cs

@@ -23,13 +23,6 @@ public Utf8String(string s)
 
         public int Length => _value.Length;
 
-        // For now, define implicit conversions between string and Utf8String to aid the transition
-        // These conversions will be removed eventually
-        public static implicit operator Utf8String(string s)
-        {
-            return new Utf8String(s);
-        }
-
         public ReadOnlySpan<byte> AsSpan() => _value;
 
         public override string ToString()

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ExternEETypeSymbolNode.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using Internal.Text;
 using Internal.TypeSystem;
 
 namespace ILCompiler.DependencyAnalysis
@@ -14,7 +15,7 @@ public sealed class ExternEETypeSymbolNode : ExternDataSymbolNode, IEETypeNode
         private TypeDesc _type;
 
         public ExternEETypeSymbolNode(NodeFactory factory, TypeDesc type)
-            : base(factory.NameMangler.NodeMangler.MethodTable(type))
+            : base(new Utf8String(factory.NameMangler.NodeMangler.MethodTable(type)))
         {
             _type = type;
 

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ExternMethodSymbolNode.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using Internal.Text;
 using Internal.TypeSystem;
 
 namespace ILCompiler.DependencyAnalysis
@@ -14,7 +15,7 @@ public sealed class ExternMethodSymbolNode : ExternFunctionSymbolNode, IMethodNo
         private MethodDesc _method;
 
         public ExternMethodSymbolNode(NodeFactory factory, MethodDesc method, bool isUnboxing = false)
-            : base(isUnboxing ? UnboxingStubNode.GetMangledName(factory.NameMangler, method) :
+            : base(isUnboxing ? new Utf8String(UnboxingStubNode.GetMangledName(factory.NameMangler, method)) :
                   factory.NameMangler.GetMangledMethodName(method))
         {
             _method = method;

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ExternSymbolsImportedNodeProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+
+using Internal.Text;
 using Internal.TypeSystem;
 
 namespace ILCompiler.DependencyAnalysis
@@ -15,12 +17,12 @@ public override IEETypeNode ImportedEETypeNode(NodeFactory factory, TypeDesc typ
 
         public override ISortableSymbolNode ImportedGCStaticNode(NodeFactory factory, MetadataType type)
         {
-            return new ExternDataSymbolNode(GCStaticsNode.GetMangledName(type, factory.NameMangler));
+            return new ExternDataSymbolNode(new Utf8String(GCStaticsNode.GetMangledName(type, factory.NameMangler)));
         }
 
         public override ISortableSymbolNode ImportedNonGCStaticNode(NodeFactory factory, MetadataType type)
         {
-            return new ExternDataSymbolNode(NonGCStaticsNode.GetMangledName(type, factory.NameMangler));
+            return new ExternDataSymbolNode(new Utf8String(NonGCStaticsNode.GetMangledName(type, factory.NameMangler)));
         }
 
         public override ISortableSymbolNode ImportedMethodDictionaryNode(NodeFactory factory, MethodDesc method)

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/NodeFactory.cs

@@ -46,7 +46,7 @@ public NodeFactory(
         {
             _target = context.Target;
 
-            InitialInterfaceDispatchStub = new AddressTakenExternFunctionSymbolNode("RhpInitialDynamicInterfaceDispatch");
+            InitialInterfaceDispatchStub = new AddressTakenExternFunctionSymbolNode(new Utf8String("RhpInitialDynamicInterfaceDispatch"u8.ToArray()));
 
             _context = context;
             _compilationModuleGroup = compilationModuleGroup;
@@ -275,15 +275,15 @@ private void CreateNodeCaches()
 
             _externFunctionSymbols = new NodeCache<string, ExternFunctionSymbolNode>((string name) =>
             {
-                return new ExternFunctionSymbolNode(name);
+                return new ExternFunctionSymbolNode(new Utf8String(name));
             });
             _externIndirectFunctionSymbols = new NodeCache<string, ExternFunctionSymbolNode>((string name) =>
             {
-                return new ExternFunctionSymbolNode(name, isIndirection: true);
+                return new ExternFunctionSymbolNode(new Utf8String(name), isIndirection: true);
             });
             _externDataSymbols = new NodeCache<string, ExternDataSymbolNode>((string name) =>
             {
-                return new ExternDataSymbolNode(name);
+                return new ExternDataSymbolNode(new Utf8String(name));
             });
 
             _pInvokeModuleFixups = new NodeCache<PInvokeModuleData, PInvokeModuleFixupNode>((PInvokeModuleData moduleData) =>
@@ -1520,7 +1520,7 @@ public ISymbolNode ConstantUtf8String(string str)
             byte[] stringBytes = new byte[stringBytesCount + 1];
             Encoding.UTF8.GetBytes(str, 0, str.Length, stringBytes, 0);
 
-            string symbolName = "__utf8str_" + NameMangler.GetMangledStringName(str);
+            Utf8String symbolName = new Utf8String("__utf8str_" + NameMangler.GetMangledStringName(str));
 
             return ReadOnlyDataBlob(symbolName, stringBytes, 1);
         }

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/PInvokeModuleFixupNode.cs

@@ -124,7 +124,7 @@ public void AppendMangledName(NameMangler nameMangler, Utf8StringBuilder sb)
         {
             sb.Append(nameMangler.GetMangledTypeName(DeclaringModule.GetGlobalModuleType()));
             sb.Append('_');
-            sb.Append(nameMangler.SanitizeName(ModuleName));
+            sb.Append(nameMangler.SanitizeName(new Utf8String(ModuleName)));
             if (DllImportSearchPath.HasValue)
             {
                 sb.Append('_');

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/RuntimeImportMethodNode.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using Internal.Text;
 using Internal.TypeSystem;
 using Internal.TypeSystem.Ecma;
 
@@ -14,7 +15,7 @@ public class RuntimeImportMethodNode : ExternFunctionSymbolNode, IMethodNode, IS
         private MethodDesc _method;
 
         public RuntimeImportMethodNode(MethodDesc method, NameMangler nameMangler)
-            : base(nameMangler.NodeMangler.ExternMethod(((EcmaMethod)method).GetRuntimeImportName(), method))
+            : base(new Utf8String(nameMangler.NodeMangler.ExternMethod(((EcmaMethod)method).GetRuntimeImportName(), method)))
         {
             _method = method;
         }

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/RootingServiceProvider.cs

@@ -4,6 +4,7 @@
 using ILCompiler.DependencyAnalysis;
 using ILCompiler.DependencyAnalysisFramework;
 
+using Internal.Text;
 using Internal.TypeSystem;
 
 using Debug = System.Diagnostics.Debug;
@@ -142,7 +143,7 @@ public void RootModuleMetadata(ModuleDesc module, string reason)
 
         public void RootReadOnlyDataBlob(byte[] data, int alignment, string reason, string exportName, bool exportHidden)
         {
-            var blob = _factory.ReadOnlyDataBlob("__readonlydata_" + exportName, data, alignment);
+            var blob = _factory.ReadOnlyDataBlob(new Utf8String($"__readonlydata_{exportName}"), data, alignment);
             _rootAdder(blob, reason);
             exportName = _factory.NameMangler.NodeMangler.ExternVariable(exportName);
             _factory.NodeAliases.Add(blob, (exportName, exportHidden));

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/UserDefinedTypeDescriptor.cs

@@ -6,6 +6,7 @@
 using System.Diagnostics;
 using System.Reflection.Metadata;
 
+using Internal.Text;
 using Internal.TypeSystem;
 using Internal.TypeSystem.Ecma;
 using Internal.TypeSystem.TypesDebugInfo;
@@ -61,7 +62,7 @@ public uint GetStateMachineThisVariableTypeIndex(TypeDesc type)
                     ClassTypeDescriptor classTypeDescriptor = new ClassTypeDescriptor
                     {
                         IsStruct = 1,
-                        Name = $"StateMachineLocals_{System.Reflection.Metadata.Ecma335.MetadataTokens.GetToken(((EcmaType)defType.GetTypeDefinition()).Handle):X}",
+                        Name = new Utf8String($"StateMachineLocals_{System.Reflection.Metadata.Ecma335.MetadataTokens.GetToken(((EcmaType)defType.GetTypeDefinition()).Handle):X}"),
                         InstanceSize = defType.InstanceByteCount.IsIndeterminate ? 0 : (ulong)defType.InstanceByteCount.AsInt,
                     };
 
@@ -764,7 +765,7 @@ private void InsertStaticFieldRegionMember(List<DataFieldDescriptor> fieldDescs,
                 ClassTypeDescriptor classTypeDescriptor = new ClassTypeDescriptor
                 {
                     IsStruct = !staticDataInObject ? 1 : 0,
-                    Name = $"__type{staticFieldForm}{_objectWriter.GetMangledName(defType)}",
+                    Name = new Utf8String($"__type{staticFieldForm}{_objectWriter.GetMangledName(defType)}"),
                     BaseClassId = 0
                 };
 
@@ -788,7 +789,7 @@ private void InsertStaticFieldRegionMember(List<DataFieldDescriptor> fieldDescs,
                     ClassTypeDescriptor helperClassTypeDescriptor = new ClassTypeDescriptor
                     {
                         IsStruct = 1,
-                        Name = $"__ThreadStaticHelper<{classTypeDescriptor.Name}>",
+                        Name = new Utf8String($"__ThreadStaticHelper<{classTypeDescriptor.Name}>"),
                         BaseClassId = 0
                     };
                     var pointerTypeDescriptor = new PointerTypeDescriptor