Author: Danny Milosavljevic <dannym@friendly-machines.com>
Date: 2026-04-08
Subject: Make roslyn 2.0.0 build with mono 6.

--- a/src/Compilers/CSharp/Portable/Symbols/SymbolExtensions.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/SymbolExtensions.cs
@@ -165,7 +165,7 @@
                 // "this" can be accessed in a lambda in a field initializer if the initializer is 
                 // a script field initializer or global statement because these are initialized 
                 // after the call to the base constructor.
-                return type.IsScriptClass ? type.InstanceConstructors.Single().ThisParameter : null;
+                return type.IsScriptClass ? System.Linq.Enumerable.Single(type.InstanceConstructors).ThisParameter : null;
             }
         }
 
@@ -199,7 +199,7 @@
         /// </summary>
         public static bool IsContainingSymbolOfAllTypeParameters(this Symbol containingSymbol, ImmutableArray<TypeSymbol> types)
         {
-            return types.All(containingSymbol.IsContainingSymbolOfAllTypeParameters);
+            return System.Linq.Enumerable.All(types, containingSymbol.IsContainingSymbolOfAllTypeParameters);
         }
 
         private static readonly Func<TypeSymbol, Symbol, bool, bool> s_hasInvalidTypeParameterFunc = (type, containingSymbol, unused) => HasInvalidTypeParameter(type, containingSymbol);
@@ -292,14 +292,14 @@
         {
             if ((object)symbol != null)
             {
-                SyntaxReference reference = symbol.DeclaringSyntaxReferences.FirstOrDefault();
+                SyntaxReference reference = symbol.DeclaringSyntaxReferences.Length > 0 ? symbol.DeclaringSyntaxReferences[0] : null;
 
                 if (reference == null && symbol.IsImplicitlyDeclared)
                 {
                     Symbol containingSymbol = symbol.ContainingSymbol;
                     if ((object)containingSymbol != null)
                     {
-                        reference = containingSymbol.DeclaringSyntaxReferences.FirstOrDefault();
+                        reference = containingSymbol.DeclaringSyntaxReferences.Length > 0 ? containingSymbol.DeclaringSyntaxReferences[0] : null;
                     }
                 }
 
@@ -328,7 +328,7 @@
 
         internal static ImmutableArray<TypeSymbol> ToTypes(this ImmutableArray<TypeWithModifiers> typesWithModifiers, out bool hasModifiers)
         {
-            hasModifiers = typesWithModifiers.Any(a => !a.CustomModifiers.IsDefaultOrEmpty);
+            hasModifiers = System.Linq.Enumerable.Any(typesWithModifiers, a => !a.CustomModifiers.IsDefaultOrEmpty);
             return typesWithModifiers.SelectAsArray(a => a.Type);
         }
 
--- a/src/Compilers/CSharp/Portable/Symbols/TypeMap.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/TypeMap.cs
@@ -26,7 +26,7 @@
 
         // Only when the caller passes allowAlpha=true do we tolerate substituted (alpha-renamed) type parameters as keys
         internal TypeMap(ImmutableArray<TypeParameterSymbol> from, ImmutableArray<TypeParameterSymbol> to, bool allowAlpha = false)
-            : this(from, to.SelectAsArray(TypeSymbolAsTypeWithModifiers), allowAlpha)
+            : this(from, Microsoft.CodeAnalysis.ImmutableArrayExtensions.SelectAsArray<Symbols.TypeParameterSymbol, Symbols.TypeWithModifiers>(to, TypeSymbolAsTypeWithModifiers), allowAlpha)
         {
             // mapping contents are read-only hereafter
         }
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
@@ -2274,7 +2274,7 @@
         {
             foreach (Symbol member in ContainingType?.GetMembers(identifier) ?? ImmutableArray<Symbol>.Empty)
             {
-                GlobalExpressionVariable field;
+                GlobalExpressionVariable field = null;
                 if (member.Kind == SymbolKind.Field &&
                     (field = member as GlobalExpressionVariable)?.SyntaxTree == node.SyntaxTree &&
                     field.SyntaxNode == node)
--- a/src/Dependencies/CodeAnalysis.Metadata/CustomDebugInfoReader.cs
+++ b/src/Dependencies/CodeAnalysis.Metadata/CustomDebugInfoReader.cs
@@ -72,7 +72,7 @@
             }
 
             int offset = 0;
-            ReadGlobalHeader(customDebugInfo, ref offset, out var globalVersion, out var globalCount);
+            ReadGlobalHeader(customDebugInfo, ref offset, out byte globalVersion, out byte globalCount);
 
             if (globalVersion != CustomDebugInfoConstants.Version)
             {
@@ -81,7 +81,7 @@
 
             while (offset <= customDebugInfo.Length - CustomDebugInfoConstants.RecordHeaderSize)
             {
-                ReadRecordHeader(customDebugInfo, ref offset, out var version, out var kind, out var size, out var alignmentSize);
+                ReadRecordHeader(customDebugInfo, ref offset, out byte version, out CustomDebugInfoKind kind, out int size, out int alignmentSize);
                 if (size < CustomDebugInfoConstants.RecordHeaderSize)
                 {
                     throw new InvalidOperationException("Invalid header.");
@@ -495,7 +495,7 @@
                 char ch1 = importString[1];
                 if ('0' <= ch1 && ch1 <= '9')
                 {
-                    if (int.TryParse(importString.Substring(1), NumberStyles.None, CultureInfo.InvariantCulture, out var tempMethodToken))
+                    if (int.TryParse(importString.Substring(1), NumberStyles.None, CultureInfo.InvariantCulture, out int tempMethodToken))
                     {
                         importStrings = getMethodImportStrings(tempMethodToken, arg);
                         Debug.Assert(!importStrings.IsDefault);
--- a/src/Dependencies/PooledObjects/ArrayBuilder.cs
+++ b/src/Dependencies/PooledObjects/ArrayBuilder.cs
@@ -402,7 +402,7 @@
             {
                 var item = this[i];
                 var key = keySelector(item);
-                if (!accumulator.TryGetValue(key, out var bucket))
+                if (!accumulator.TryGetValue(key, out ArrayBuilder<T> bucket))
                 {
                     bucket = ArrayBuilder<T>.GetInstance();
                     accumulator.Add(key, bucket);