Implements misc CR feedback: naming, comments, moving code around, etc. (changeset 1393287)

Src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml

@@ -556,11 +556,11 @@
   </Node>
 
   <!--
-  BoundIteratorScope represents a scope within a translated iterator method.
+  BoundStateMachineScope represents a scope within a translated iterator/async method.
   It is used to emit debugging information that allows the EE to map 
   fields to locals.
   -->
-  <Node Name="BoundIteratorScope" Base="BoundStatement">
+  <Node Name="BoundStateMachineScope" Base="BoundStatement">
     <Field Name="Fields" Type="ImmutableArray&lt;StateMachineFieldSymbol&gt;"/>
     <Field Name="Statement" Type="BoundStatement" Null="disallow"/>
   </Node>

Src/Compilers/CSharp/Portable/CodeGen/EmitStatement.cs

@@ -69,8 +69,8 @@ private void EmitStatement(BoundStatement statement)
                     EmitSwitchStatement((BoundSwitchStatement)statement);
                     break;
 
-                case BoundKind.IteratorScope:
-                    EmitIteratorScope((BoundIteratorScope)statement);
+                case BoundKind.StateMachineScope:
+                    EmitStateMachineScope((BoundStateMachineScope)statement);
                     break;
 
                 case BoundKind.NoOpStatement:
@@ -598,16 +598,16 @@ private void EmitBlock(BoundBlock block)
             }
         }
 
-        private void EmitIteratorScope(BoundIteratorScope scope)
+        private void EmitStateMachineScope(BoundStateMachineScope scope)
         {
-            builder.OpenIteratorScope();
+            builder.OpenStateMachineScope();
             foreach (var field in scope.Fields)
             {
                 builder.DefineUserDefinedStateMachineHoistedLocal(field.SlotIndex);
             }
 
             EmitStatement(scope.Statement);
-            builder.CloseIteratorScope();
+            builder.CloseStateMachineScope();
         }
 
         // There are two ways a value can be returned from a function:

Src/Compilers/CSharp/Portable/Lowering/AsyncRewriter/AsyncRewriter.cs

@@ -82,7 +82,7 @@ protected override void GenerateControlFields()
         {
             // the fields are initialized from async method, so they need to be public:
 
-            this.stateField = F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeStateMachineStateName(), isPublic: true);
+            this.stateField = F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeStateMachineStateFieldName(), isPublic: true);
             this.builderField = F.StateMachineField(asyncMethodBuilderMemberCollection.BuilderType, GeneratedNames.AsyncBuilderFieldName(), isPublic: true);
         }
 

Src/Compilers/CSharp/Portable/Lowering/IteratorRewriter/IteratorConstructor.cs

@@ -19,7 +19,7 @@ internal IteratorConstructor(IteratorStateMachine container)
         {
             var intType = container.DeclaringCompilation.GetSpecialType(SpecialType.System_Int32);
             parameters = ImmutableArray.Create<ParameterSymbol>(
-                new SynthesizedParameterSymbol(this, intType, 0, RefKind.None, GeneratedNames.MakeStateMachineStateName()));
+                new SynthesizedParameterSymbol(this, intType, 0, RefKind.None, GeneratedNames.MakeStateMachineStateFieldName()));
         }
 
         internal override void AddSynthesizedAttributes(ModuleCompilationState compilationState, ref ArrayBuilder<SynthesizedAttributeData> attributes)

Src/Compilers/CSharp/Portable/Lowering/IteratorRewriter/IteratorRewriter.cs

@@ -84,7 +84,7 @@ protected override bool PreserveInitialParameterValues
 
         protected override void GenerateControlFields()
         {
-            this.stateField = F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeStateMachineStateName());
+            this.stateField = F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeStateMachineStateFieldName());
 
             // Add a field: T current
             currentField = F.StateMachineField(elementType, GeneratedNames.MakeIteratorCurrentBackingFieldName());
@@ -97,7 +97,7 @@ protected override void GenerateControlFields()
                     (object)F.WellKnownMember(WellKnownMember.System_Environment__CurrentManagedThreadId, isOptional: true) != null);
 
             initialThreadIdField = addInitialThreadId
-                ? F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeIteratorCurrentThreadIdName())
+                ? F.StateMachineField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeIteratorCurrentThreadIdFieldName())
                 : null;
         }
 

Src/Compilers/CSharp/Portable/Lowering/LambdaRewriter/LambdaCapturedVariable.cs

@@ -49,7 +49,7 @@ private static string GetCapturedVariableFieldName(Symbol variable, ref int uniq
         {
             if (IsThis(variable))
             {
-                return GeneratedNames.ThisProxyName();
+                return GeneratedNames.ThisProxyFieldName();
             }
 
             var local = variable as LocalSymbol;

Src/Compilers/CSharp/Portable/Lowering/LambdaRewriter/LambdaFrame.cs

@@ -31,7 +31,7 @@ internal LambdaFrame(VariableSlotAllocator slotAllocatorOpt, TypeCompilationStat
             if (isStatic)
             {
                 this.staticConstructor = new SynthesizedStaticConstructor(this);
-                var cacheVariableName = GeneratedNames.MakeCachedFrameInstanceName();
+                var cacheVariableName = GeneratedNames.MakeCachedFrameInstanceFieldName();
                 singletonCache = new SynthesizedLambdaCacheFieldSymbol(this, this, cacheVariableName, topLevelMethod, isReadOnly: true, isStatic: true);
                 this.ScopeSyntaxOpt = null;
             }

Src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/IteratorAndAsyncCaptureWalker.cs

@@ -94,20 +94,6 @@ public static OrderedSet<Symbol> Analyze(CSharpCompilation compilation, MethodSy
             return variablesToHoist;
         }
 
-        private static int GetVariableSourcePosition(Symbol symbol)
-        {
-            if (symbol.Locations.IsEmpty)
-            {
-                // All user-defined locals and long-lived synthesized variables have to have a position.
-                Debug.Assert(symbol is SynthesizedParameterSymbol || !((LocalSymbol)symbol).SynthesizedKind.IsLongLived());
-
-                // Short-lived locals don't get hoisted to fields, so their order doesn't matter.
-                return -1;
-            }
-
-            return symbol.Locations[0].SourceSpan.Start;
-        }
-
         private static bool HoistInDebugBuild(Symbol symbol)
         {
             // in Debug build hoist all parameters that can be hoisted:
@@ -177,11 +163,7 @@ public override BoundNode VisitYieldReturnStatement(BoundYieldReturnStatement no
         protected override ImmutableArray<PendingBranch> Scan(ref bool badRegion)
         {
             variablesToHoist.Clear();
-
-            if (lazyDisallowedCaptures != null)
-            {
-                lazyDisallowedCaptures.Clear();
-            }
+            lazyDisallowedCaptures?.Clear();
 
             return base.Scan(ref badRegion);
         }

Src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/MethodToStateMachineRewriter.cs

@@ -322,7 +322,7 @@ private BoundStatement PossibleIteratorScope(ImmutableArray<LocalSymbol> locals,
             // wrap the node in an iterator scope for debugging
             if (hoistedLocalsWithDebugScopes.Count != 0)
             {
-                translatedStatement = F.Block(new BoundIteratorScope(F.Syntax, hoistedLocalsWithDebugScopes.ToImmutable(), translatedStatement));
+                translatedStatement = F.Block(new BoundStateMachineScope(F.Syntax, hoistedLocalsWithDebugScopes.ToImmutable(), translatedStatement));
             }
 
             hoistedLocalsWithDebugScopes.Free();

Src/Compilers/CSharp/Portable/Lowering/StateMachineRewriter/StateMachineRewriter.cs

@@ -201,7 +201,7 @@ protected BoundStatement Rewrite()
                     if (parameter.IsThis)
                     {
                         var containingType = method.ContainingType;
-                        var proxyField = F.StateMachineField(containingType, GeneratedNames.ThisProxyName(), isPublic: true);
+                        var proxyField = F.StateMachineField(containingType, GeneratedNames.ThisProxyFieldName(), isPublic: true);
                         proxiesBuilder.Add(parameter, new CapturedToStateMachineFieldReplacement(proxyField, isReusable: false));
 
                         if (PreserveInitialParameterValues)
@@ -221,7 +221,7 @@ protected BoundStatement Rewrite()
 
                         if (PreserveInitialParameterValues)
                         {
-                            var field = F.StateMachineField(typeMap.SubstituteType(parameter.Type), GeneratedNames.StateMachineParameterProxyName(parameter.Name), isPublic: true);
+                            var field = F.StateMachineField(typeMap.SubstituteType(parameter.Type), GeneratedNames.StateMachineParameterProxyFieldName(parameter.Name), isPublic: true);
                             initialParameters.Add(parameter, new CapturedToStateMachineFieldReplacement(field, isReusable: false));
                         }
                     }

Src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNameKind.cs

 // Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-using System;
-using System.Diagnostics;
-using Roslyn.Utilities;
-
 namespace Microsoft.CodeAnalysis.CSharp.Symbols
 {
     internal enum GeneratedNameKind
@@ -11,11 +7,11 @@ internal enum GeneratedNameKind
         None = 0,
 
         // Used by EE:
-        ThisProxy = '4',
+        ThisProxyField = '4',
         HoistedLocalField = '5',
         DisplayClassLocalOrField = '8',
         LambdaMethod = 'b',
-        LambdaDisplayClassType = 'c',
+        LambdaDisplayClass = 'c',
         StateMachineType = 'd',
 
         // Used by EnC:
@@ -23,60 +19,35 @@ internal enum GeneratedNameKind
         HoistedSynthesizedLocalField = 's',
 
         // Currently not parsed:
-        DynamicCallSiteContainer = 'o',
+        StateMachineStateField = '1',
+        IteratorCurrentBackingField = '2',
+        StateMachineParameterProxyField = '3',
+        ReusableHoistedLocalField = '7',
         LambdaCacheField = '9',
+        FixedBufferField = 'e',
+        AutoPropertyBackingField = 'k',
+        IteratorCurrentThreadIdField = 'l',
+        IteratorFinallyMethod = 'm',
+        BaseMethodWrapper = 'n',
+        AsyncBuilderField = 't',
+        DynamicCallSiteContainerType = 'o',
+        DynamicCallSiteField = 'p',
     }
 
-    internal static partial class GeneratedNames
+    internal static class GeneratedNameKindExtensions
     {
-        // The type of generated name. See TryParseGeneratedName.
-        internal static GeneratedNameKind GetKind(string name)
+        internal static bool IsTypeName(this GeneratedNameKind kind)
         {
-            GeneratedNameKind kind;
-            int openBracketOffset;
-            int closeBracketOffset;
-            return TryParseGeneratedName(name, out kind, out openBracketOffset, out closeBracketOffset) ? kind : GeneratedNameKind.None;
-        }
-
-        // Parse the generated name. Returns true for names of the form
-        // [CS$]<[middle]>c[__[suffix]] where [CS$] is included for certain
-        // generated names, where [middle] and [__[suffix]] are optional,
-        // and where c is a single character in [1-9a-z]
-        // (csharp\LanguageAnalysis\LIB\SpecialName.cpp).
-        internal static bool TryParseGeneratedName(
-            string name,
-            out GeneratedNameKind kind,
-            out int openBracketOffset,
-            out int closeBracketOffset)
+            switch (kind)
         {
-            openBracketOffset = -1;
-            if (name.StartsWith("CS$<", StringComparison.Ordinal))
-            {
-                openBracketOffset = 3;
-            }
-            else if (name.StartsWith("<", StringComparison.Ordinal))
-            {
-                openBracketOffset = 0;
-            }
-
-            if (openBracketOffset >= 0)
-            {
-                closeBracketOffset = name.IndexOfBalancedParenthesis(openBracketOffset, '>');
-                if (closeBracketOffset >= 0 && closeBracketOffset + 1 < name.Length)
-                {
-                    int c = name[closeBracketOffset + 1];
-                    if ((c >= '1' && c <= '9') || (c >= 'a' && c <= 'z')) // Note '0' is not special.
-                    {
-                        kind = (GeneratedNameKind)c;
+                case GeneratedNameKind.LambdaDisplayClass:
+                case GeneratedNameKind.StateMachineType:
+                case GeneratedNameKind.DynamicCallSiteContainerType:
                         return true;
-                    }
-                }
-            }
 
-            kind = GeneratedNameKind.None;
-            openBracketOffset = -1;
-            closeBracketOffset = -1;
+                default:
             return false;
         }
     }
 }
+}

Src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNames.cs

 // Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Globalization;
 using System.Linq;
@@ -20,14 +17,6 @@ internal static partial class GeneratedNames
         private const char IdSeparator = '_';
         private const char GenerationSeparator = '#';
 
-        private static readonly ImmutableArray<string> numericStrings = ImmutableArray.Create("0", "1", "2", "3", "4", "5", "6", "7", "8", "9");
-
-        private static string GetString(int number)
-        {
-            Debug.Assert(number >= 0);
-            return (number < numericStrings.Length) ? numericStrings[number] : number.ToString();
-        }
-
         internal static bool IsGeneratedMemberName(string memberName)
         {
             return memberName.Length > 0 && memberName[0] == '<';
@@ -35,6 +24,7 @@ internal static bool IsGeneratedMemberName(string memberName)
 
         internal static string MakeBackingFieldName(string propertyName)
         {
+            Debug.Assert((char)GeneratedNameKind.AutoPropertyBackingField == 'k');
             return "<" + propertyName + ">k__BackingField";
         }
 
@@ -46,12 +36,13 @@ internal static string MakeIteratorFinallyMethodName(int iteratorState)
             // <>m__Finally3
             // . . . 
             // that will roughly match native naming scheme and may also be easier when need to debug.
-            return "<>m__Finally" + GetString(Math.Abs(iteratorState + 2));
+            Debug.Assert((char)GeneratedNameKind.IteratorFinallyMethod == 'm');
+            return "<>m__Finally" + StringExtensions.GetNumeral(Math.Abs(iteratorState + 2));
         }
 
         internal static string MakeStaticLambdaDisplayClassName(int methodOrdinal, int generation)
         {
-            return MakeMethodScopedSynthesizedName(GeneratedNameKind.LambdaDisplayClassType, methodOrdinal, generation);
+            return MakeMethodScopedSynthesizedName(GeneratedNameKind.LambdaDisplayClass, methodOrdinal, generation);
         }
 
         internal static string MakeLambdaDisplayClassName(int methodOrdinal, int generation, int scopeOrdinal)
@@ -60,15 +51,15 @@ internal static string MakeLambdaDisplayClassName(int methodOrdinal, int generat
             Debug.Assert(scopeOrdinal >= -1);
             Debug.Assert(methodOrdinal >= 0);
 
-            return MakeMethodScopedSynthesizedName(GeneratedNameKind.LambdaDisplayClassType, methodOrdinal, generation, suffix: "DisplayClass", uniqueId: scopeOrdinal, isTypeName: true);
+            return MakeMethodScopedSynthesizedName(GeneratedNameKind.LambdaDisplayClass, methodOrdinal, generation, suffix: "DisplayClass", uniqueId: scopeOrdinal, isTypeName: true);
         }
 
         internal static string MakeAnonymousTypeTemplateName(int index, int submissionSlotIndex, string moduleId)
         {
-            var name = "<" + moduleId + ">f__AnonymousType" + GetString(index);
+            var name = "<" + moduleId + ">f__AnonymousType" + StringExtensions.GetNumeral(index);
             if (submissionSlotIndex >= 0)
             {
-                name += "#" + GetString(submissionSlotIndex);
+                name += "#" + StringExtensions.GetNumeral(submissionSlotIndex);
             }
 
             return name;
@@ -125,7 +116,8 @@ internal static string MakeStateMachineTypeName(string methodName, int methodOrd
 
         internal static string MakeBaseMethodWrapperName(int uniqueId)
         {
-            return "<>n__" + GetString(uniqueId);
+            Debug.Assert((char)GeneratedNameKind.BaseMethodWrapper == 'n');
+            return "<>n__" + StringExtensions.GetNumeral(uniqueId);
         }
 
         internal static string MakeLambdaMethodName(string methodName, int methodOrdinal, int generation, int lambdaOrdinal)
@@ -168,7 +160,7 @@ private static string MakeMethodScopedSynthesizedName(GeneratedNameKind kind, in
                 // consumer cannot figure where namespace ends and actual type name starts.
                 // Therefore it is a good practice to avoid type names with dots.
                 // As a replacement use a character not allowed in C# identifier to avoid conflicts.
-                if (isTypeName)
+                if (kind.IsTypeName())
                 {
                     builder.Replace('.', DotReplacementInTypeNames);
                 }
@@ -241,7 +233,7 @@ internal static string MakeHoistedLocalFieldName(SynthesizedLocalKind kind, int
             }
             else
             {
-                builder.Append('s');
+                builder.Append((char)GeneratedNameKind.HoistedSynthesizedLocalField);
             }
 
             builder.Append("__");
@@ -250,9 +242,87 @@ internal static string MakeHoistedLocalFieldName(SynthesizedLocalKind kind, int
             return result.ToStringAndFree();
         }
 
+        // The type of generated name. See TryParseGeneratedName.
+        internal static GeneratedNameKind GetKind(string name)
+        {
+            GeneratedNameKind kind;
+            int openBracketOffset;
+            int closeBracketOffset;
+            return TryParseGeneratedName(name, out kind, out openBracketOffset, out closeBracketOffset) ? kind : GeneratedNameKind.None;
+        }
+
+        // Parse the generated name. Returns true for names of the form
+        // [CS$]<[middle]>c[__[suffix]] where [CS$] is included for certain
+        // generated names, where [middle] and [__[suffix]] are optional,
+        // and where c is a single character in [1-9a-z]
+        // (csharp\LanguageAnalysis\LIB\SpecialName.cpp).
+        internal static bool TryParseGeneratedName(
+            string name,
+            out GeneratedNameKind kind,
+            out int openBracketOffset,
+            out int closeBracketOffset)
+        {
+            openBracketOffset = -1;
+            if (name.StartsWith("CS$<", StringComparison.Ordinal))
+            {
+                openBracketOffset = 3;
+            }
+            else if (name.StartsWith("<", StringComparison.Ordinal))
+            {
+                openBracketOffset = 0;
+            }
+
+            if (openBracketOffset >= 0)
+            {
+                closeBracketOffset = name.IndexOfBalancedParenthesis(openBracketOffset, '>');
+                if (closeBracketOffset >= 0 && closeBracketOffset + 1 < name.Length)
+                {
+                    int c = name[closeBracketOffset + 1];
+                    if ((c >= '1' && c <= '9') || (c >= 'a' && c <= 'z')) // Note '0' is not special.
+                    {
+                        kind = (GeneratedNameKind)c;
+                        return true;
+                    }
+                }
+            }
+
+            kind = GeneratedNameKind.None;
+            openBracketOffset = -1;
+            closeBracketOffset = -1;
+            return false;
+        }
+
+        internal static bool TryParseSourceMethodNameFromGeneratedName(string generatedName, GeneratedNameKind requiredKind, out string methodName)
+        {
+            int openBracketOffset;
+            int closeBracketOffset;
+            GeneratedNameKind kind;
+            if (!TryParseGeneratedName(generatedName, out kind, out openBracketOffset, out closeBracketOffset))
+            {
+                methodName = null;
+                return false;
+            }
+
+            if (requiredKind != 0 && kind != requiredKind)
+            {
+                methodName = null;
+                return false;
+            }
+
+            methodName = generatedName.Substring(openBracketOffset + 1, closeBracketOffset - openBracketOffset - 1);
+
+            if (kind.IsTypeName())
+            {
+                methodName = methodName.Replace(DotReplacementInTypeNames, '.');
+            }
+
+            return true;
+        }
+
         internal static string AsyncAwaiterFieldName(int slotIndex)
         {
-            return "<>u__" + GetString(slotIndex + 1);
+            Debug.Assert((char)GeneratedNameKind.AwaiterField == 'u');
+            return "<>u__" + StringExtensions.GetNumeral(slotIndex + 1);
         }
 
         // Extracts the slot index from a name of a field that stores hoisted variables or awaiters.
@@ -277,8 +347,9 @@ internal static bool TryParseSlotIndex(string fieldName, out int slotIndex)
             return false;
         }
 
-        internal static string MakeCachedFrameInstanceName()
+        internal static string MakeCachedFrameInstanceFieldName()
         {
+            Debug.Assert((char)GeneratedNameKind.LambdaCacheField == '9');
             return "<>9";
         }
 
@@ -298,7 +369,7 @@ internal static string MakeSynthesizedLocalName(SynthesizedLocalKind kind, ref i
         internal static string MakeLambdaDisplayLocalName(int uniqueId)
         {
             Debug.Assert((char)GeneratedNameKind.DisplayClassLocalOrField == '8');
-            return SynthesizedLocalNamePrefix + "<>8__locals" + GetString(uniqueId);
+            return SynthesizedLocalNamePrefix + "<>8__locals" + StringExtensions.GetNumeral(uniqueId);
         }
 
         internal static bool IsSynthesizedLocalName(string name)
@@ -309,94 +380,68 @@ internal static bool IsSynthesizedLocalName(string name)
         internal static string MakeFixedFieldImplementationName(string fieldName)
         {
             // the native compiler adds numeric digits at the end.  Roslyn does not.
+            Debug.Assert((char)GeneratedNameKind.FixedBufferField == 'e');
             return "<" + fieldName + ">e__FixedBuffer";
         }
 
-        internal static string MakeStateMachineStateName()
+        internal static string MakeStateMachineStateFieldName()
         {
             // Microsoft.VisualStudio.VIL.VisualStudioHost.AsyncReturnStackFrame depends on this name.
+            Debug.Assert((char)GeneratedNameKind.StateMachineStateField == '1');
             return "<>1__state";
         }
 
-        internal static bool TryParseIteratorName(string mangledTypeName, out string iteratorName)
-        {
-            GeneratedNameKind kind;
-            int openBracketOffset;
-            int closeBracketOffset;
-            if (TryParseGeneratedName(mangledTypeName, out kind, out openBracketOffset, out closeBracketOffset) &&
-                (kind == GeneratedNameKind.StateMachineType) &&
-                (openBracketOffset == 0))
-            {
-                iteratorName = mangledTypeName.Substring(openBracketOffset + 1, closeBracketOffset - openBracketOffset - 1);
-                return true;
-            }
-
-            iteratorName = null;
-            return false;
-        }
-
-        internal static bool TryParseLambdaMethodName(string mangledTypeName, out string containingMethodName)
-        {
-            GeneratedNameKind kind;
-            int openBracketOffset;
-            int closeBracketOffset;
-            if (TryParseGeneratedName(mangledTypeName, out kind, out openBracketOffset, out closeBracketOffset) &&
-                (kind == GeneratedNameKind.LambdaMethod) &&
-                (openBracketOffset == 0))
-            {
-                containingMethodName = mangledTypeName.Substring(openBracketOffset + 1, closeBracketOffset - openBracketOffset - 1);
-                return true;
-            }
-
-            containingMethodName = null;
-            return false;
-        }
-
         internal static string MakeIteratorCurrentBackingFieldName()
         {
+            Debug.Assert((char)GeneratedNameKind.IteratorCurrentBackingField == '2');
             return "<>2__current";
         }
 
-        internal static string MakeIteratorCurrentThreadIdName()
+        internal static string MakeIteratorCurrentThreadIdFieldName()
         {
+            Debug.Assert((char)GeneratedNameKind.IteratorCurrentThreadIdField == 'l');
             return "<>l__initialThreadId";
         }
 
-        internal static string ThisProxyName()
+        internal static string ThisProxyFieldName()
         {
-            Debug.Assert((char)GeneratedNameKind.ThisProxy == '4');
+            Debug.Assert((char)GeneratedNameKind.ThisProxyField == '4');
             return "<>4__this";
         }
 
         internal static string StateMachineThisParameterProxyName()
         {
-            return StateMachineParameterProxyName(ThisProxyName());
+            return StateMachineParameterProxyFieldName(ThisProxyFieldName());
         }
 
-        internal static string StateMachineParameterProxyName(string parameterName)
+        internal static string StateMachineParameterProxyFieldName(string parameterName)
         {
+            Debug.Assert((char)GeneratedNameKind.StateMachineParameterProxyField == '3');
             return "<>3__" + parameterName;
         }
 
         internal static string MakeDynamicCallSiteContainerName(int methodOrdinal, int generation)
         {
-            return MakeMethodScopedSynthesizedName(GeneratedNameKind.DynamicCallSiteContainer, methodOrdinal, generation, isTypeName: true);
+            return MakeMethodScopedSynthesizedName(GeneratedNameKind.DynamicCallSiteContainerType, methodOrdinal, generation, isTypeName: true);
         }
 
         internal static string MakeDynamicCallSiteFieldName(int uniqueId)
         {
-            return "<>p__" + GetString(uniqueId);
+            Debug.Assert((char)GeneratedNameKind.DynamicCallSiteField == 'p');
+            return "<>p__" + StringExtensions.GetNumeral(uniqueId);
         }
 
         internal static string AsyncBuilderFieldName()
         {
             // Microsoft.VisualStudio.VIL.VisualStudioHost.AsyncReturnStackFrame depends on this name.
+            Debug.Assert((char)GeneratedNameKind.AsyncBuilderField == 't');
             return "<>t__builder";
         }
 
         internal static string ReusableHoistedLocalFieldName(int number)
         {
-            return "<>7__wrap" + GetString(number);
+            Debug.Assert((char)GeneratedNameKind.ReusableHoistedLocalField == '7');
+            return "<>7__wrap" + StringExtensions.GetNumeral(number);
         }
     }
 }

Src/Compilers/Core/CodeAnalysisTest/CodeAnalysisTest.csproj

@@ -26,6 +26,7 @@
     <Compile Include="Diagnostics\DiagnosticLocalizationTests.cs" />
     <Compile Include="Emit\EmitOptionsTests.cs" />
     <Compile Include="Emit\CustomDebugInfoReaderTests.cs" />
+    <Compile Include="InternalUtilities\StringExtensionsTests.cs" />
     <Compile Include="PEWriter\BinaryWriterTests.cs" />
     <Compile Include="XmlDocumentationCommentTextReaderTests.cs" />
   </ItemGroup>

Src/Compilers/Core/CodeAnalysisTest/InternalUtilities/EnumerableExtensionsTests.cs

 // Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 using Xunit;
 
 namespace Roslyn.Utilities.UnitTests.InternalUtilities

Src/Compilers/Core/CodeAnalysisTest/InternalUtilities/StringExtensionsTests.cs

+// Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using Xunit;
+
+namespace Roslyn.Utilities.UnitTests.InternalUtilities
+{
+    public class StringExtensionsTests
+    {
+        [Fact]
+        public void GetNumeral1()
+        {
+            Assert.Equal("0", StringExtensions.GetNumeral(0));
+            Assert.Equal("5", StringExtensions.GetNumeral(5));
+            Assert.Equal("10", StringExtensions.GetNumeral(10));
+            Assert.Equal("10000000", StringExtensions.GetNumeral(10000000));
+        }
+    }
+}

Src/Compilers/Core/Portable/CodeGen/ILBuilder.cs

@@ -1133,7 +1133,7 @@ internal void OpenLocalScope(ScopeType scopeType = ScopeType.Variable, Microsoft
                     break;
                 case ScopeType.Variable:
                 case ScopeType.TryCatchFinally:
-                case ScopeType.IteratorVariable:
+                case ScopeType.StateMachineVariable:
                     break;
                 default:
                     throw ExceptionUtilities.UnexpectedValue(scopeType);
@@ -1166,9 +1166,9 @@ internal void CloseLocalScope()
             scopeManager.CloseScope(this);
         }
 
-        internal void OpenIteratorScope()
+        internal void OpenStateMachineScope()
         {
-            OpenLocalScope(ScopeType.IteratorVariable);
+            OpenLocalScope(ScopeType.StateMachineVariable);
         }
 
         internal void DefineUserDefinedStateMachineHoistedLocal(int slotIndex)
@@ -1178,7 +1178,7 @@ internal void DefineUserDefinedStateMachineHoistedLocal(int slotIndex)
             scopeManager.AddUserHoistedLocal(slotIndex);
         }
 
-        internal void CloseIteratorScope()
+        internal void CloseStateMachineScope()
         {
             scopeManager.ClosingScope(this);
             EndBlock(); // blocks should not cross scope boundaries.

Src/Compilers/Core/Portable/CodeGen/LocalScopeManager.cs

@@ -224,7 +224,7 @@ internal abstract class ScopeInfo
                 }
                 else
                 {
-                    Debug.Assert(scopeType == ScopeType.Variable || scopeType == ScopeType.IteratorVariable);
+                    Debug.Assert(scopeType == ScopeType.Variable || scopeType == ScopeType.StateMachineVariable);
                     return new LocalScopeInfo();
                 }
             }

Src/Compilers/Core/Portable/CodeGen/ScopeType.cs

@@ -11,6 +11,10 @@ internal enum ScopeType
         Filter,
         Finally,
         Fault,
-        IteratorVariable,
+
+        /// <summary>
+        /// Scope of user-defined variable hoisted to state machine.
+        /// </summary>
+        StateMachineVariable,
     }
 }

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

@@ -2,13 +2,28 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Diagnostics;
-using System.Linq;
 
 namespace Roslyn.Utilities
 {
     internal static class StringExtensions
     {
+        private static ImmutableArray<string> lazyNumerals;
+
+        internal static string GetNumeral(int number)
+        {
+            var numerals = lazyNumerals;
+            if (numerals.IsDefault)
+            {
+                numerals = ImmutableArray.Create("0", "1", "2", "3", "4", "5", "6", "7", "8", "9");
+                ImmutableInterlocked.InterlockedInitialize(ref lazyNumerals, numerals);
+            }
+
+            Debug.Assert(number >= 0);
+            return (number < numerals.Length) ? numerals[number] : number.ToString();
+        }
+
         public static string Join(this IEnumerable<string> source, string separator)
         {
             if (source == null)

Src/Compilers/Core/Portable/InternalUtilities/StringTable.cs

 // Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
-using System.Linq;
 using System.Text;
-using System.Threading.Tasks;
-using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.Text;
 using System.Threading;
 
 namespace Roslyn.Utilities

Src/Compilers/Core/Portable/PEWriter/BinaryWriter.cs

@@ -252,7 +252,13 @@ internal unsafe void WriteUlong(ulong value)
             }
         }
 
-        public void WriteReference(uint reference, int size)
+        /// <summary>
+        /// Writes a reference to a heap (heap index) or a table (row id).
+        /// </summary>
+        /// <remarks>
+        /// References may be small (2B) or large (4B).
+        /// </remarks>
+        internal void WriteReference(uint reference, int size)
         {
             Debug.Assert(size == 2 || size == 4);
 

Src/Compilers/Core/Portable/PEWriter/MetadataHeapsBuilder.cs

-
+// Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;

Src/Compilers/Core/Portable/PEWriter/MetadataSizes.cs

@@ -81,6 +81,9 @@ internal sealed class MetadataSizes
             int resourceDataSize, 
             bool isMinimalDelta)
         {
+            Debug.Assert(rowCounts.Length == MetadataTokens.TableCount);
+            Debug.Assert(heapSizes.Length == MetadataTokens.HeapCount);
+
             const byte large = 4;
             const byte small = 2;
 

Src/Compilers/Core/Portable/PEWriter/SequencePoint.cs

@@ -35,13 +35,7 @@ internal struct SequencePoint
             Document = document;
         }
 
-        public bool IsHidden
-        {
-            get
-            {
-                return StartLine == 0xfeefee;
-            }
-        }
+        public bool IsHidden => StartLine == 0xfeefee;
 
         public override int GetHashCode()
         {

Src/Test/PdbUtilities/Metadata/MetadataVisualizer.cs

@@ -1055,7 +1055,7 @@ private void WriteUserStrings()
             }
 
             // TODO: the heap is aligned, don't display the trailing empty strings
-            writer.WriteLine(string.Format("#US (size = {0}):", size));
+            writer.WriteLine($"#US (size = {size}):");
             var handle = MetadataTokens.UserStringHandle(0);
             do
             {
@@ -1076,7 +1076,7 @@ private void WriteStrings()
                 return;
             }
 
-            writer.WriteLine(string.Format("#String (size = {0}):", size));
+            writer.WriteLine($"#String (size = {size}):");
             var handle = MetadataTokens.StringHandle(0);
             do
             {
@@ -1099,7 +1099,7 @@ private void WriteBlobs()
 
             int[] sizePerKind = new int[(int)BlobKind.Count];
 
-            writer.WriteLine(string.Format("#Blob (size = {0}):", size));
+            writer.WriteLine($"#Blob (size = {size}):");
             var handle = MetadataTokens.BlobHandle(0);
             do
             {

Src/Workspaces/Core/Portable/Differencing/LongestCommonImmutableArraySubsequence.cs

@@ -11,10 +11,6 @@ namespace Microsoft.CodeAnalysis.Differencing
     /// </summary>
     internal abstract class LongestCommonImmutableArraySubsequence<TElement> : LongestCommonSubsequence<ImmutableArray<TElement>>
     {
-        protected LongestCommonImmutableArraySubsequence()
-        {
-        }
-
         protected abstract bool Equals(TElement oldElement, TElement newElement);
 
         protected sealed override bool ItemsEqual(ImmutableArray<TElement> oldSequence, int oldIndex, ImmutableArray<TElement> newSequence, int newIndex)