Implement support for captured Primary Constructor parameters in EE when portable PDB is used.

src/Compilers/CSharp/Portable/Binder/Binder.CapturedParametersFinder.cs

@@ -77,12 +77,10 @@ public static IReadOnlyDictionary<ParameterSymbol, FieldSymbol> GetCapturedParam
 
                 foreach (var parameter in captured)
                 {
-                    // https://github.com/dotnet/roslyn/issues/67103: Figure out naming strategy
-                    // Some thoughts/recommendations from Tomas:
-                    // We should define GeneratedNameKind entry (e..g P looks free to use) and add a helper to GeneratedNames that produces the name.
-                    // I'd also just keep the name as short as possible to avoid unnecessary metadata bloat. Could be just <name>P.
-                    string name = "<" + parameter.Name + ">PC__BackingField";
-                    result.Add(parameter, new SynthesizedPrimaryConstructorParameterBackingFieldSymbol(parameter, name, isReadOnly: containingType.IsReadOnly));
+                    result.Add(parameter,
+                               new SynthesizedPrimaryConstructorParameterBackingFieldSymbol(parameter,
+                                                                                            GeneratedNames.MakePrimaryConstructorParameterFieldName(parameter.Name),
+                                                                                            isReadOnly: containingType.IsReadOnly));
                 }
 
                 captured.Free();

src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs

@@ -1667,7 +1667,8 @@ private static MethodBody GenerateMethodBody(
                     stateMachineAwaiterSlots,
                     StateMachineStatesDebugInfo.Create(variableSlotAllocatorOpt, stateMachineStateDebugInfos),
                     moveNextBodyDebugInfoOpt,
-                    codeCoverageSpans);
+                    codeCoverageSpans,
+                    isPrimaryConstructor: method is SynthesizedPrimaryConstructor);
             }
             finally
             {

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

@@ -43,6 +43,7 @@ internal enum GeneratedNameKind
         AsyncBuilderField = 't',
         DelegateCacheContainerType = 'O',
         DynamicCallSiteContainerType = 'o',
+        PrimaryConstructorParameter = 'P',
         DynamicCallSiteField = 'p',
         AsyncIteratorPromiseOfValueOrEndBackingField = 'v',
         DisposeModeField = 'w',

src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNameParser.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Text.RegularExpressions;
@@ -173,6 +174,21 @@ internal static bool TryParseAnonymousTypeParameterName(string typeParameterName
             return false;
         }
 
+        internal static bool TryParsePrimaryConstructorParameterFieldName(string fieldName, [NotNullWhen(true)] out string? parameterName)
+        {
+            Debug.Assert((char)GeneratedNameKind.PrimaryConstructorParameter == 'P');
+
+            if (fieldName.StartsWith("<", StringComparison.Ordinal) &&
+                fieldName.EndsWith(">P", StringComparison.Ordinal))
+            {
+                parameterName = fieldName.Substring(1, fieldName.Length - 3);
+                return true;
+            }
+
+            parameterName = null;
+            return false;
+        }
+
         private const int sha256LengthBytes = 32;
         private const int sha256LengthHexChars = sha256LengthBytes * 2;
 

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

@@ -27,6 +27,12 @@ internal static string MakeBackingFieldName(string propertyName)
             return "<" + propertyName + ">k__BackingField";
         }
 
+        internal static string MakePrimaryConstructorParameterFieldName(string parameterName)
+        {
+            Debug.Assert((char)GeneratedNameKind.PrimaryConstructorParameter == 'P');
+            return "<" + parameterName + ">P";
+        }
+
         internal static string MakeIteratorFinallyMethodName(StateMachineState finalizeState)
         {
             Debug.Assert((int)finalizeState < -2);