Ensure mscorlib is included when ignoring unreferenced assemblies

src/Compilers/Core/Portable/MetadataReader/MetadataReaderExtensions.cs

@@ -157,5 +157,34 @@ internal static Guid GetModuleVersionIdOrThrow(this MetadataReader reader)
                 contentType: (AssemblyContentType)((int)(flags & AssemblyFlags.ContentTypeMask) >> 9),
                 noThrow: true);
         }
+
+        internal static bool DeclaresTheObjectClass(this MetadataReader reader)
+        {
+            foreach (TypeDefinitionHandle handle in reader.TypeDefinitions)
+            {
+                try
+                {
+                    var typeDef = reader.GetTypeDefinition(handle);
+                    if (typeDef.BaseType.IsNil &&
+                        (typeDef.Attributes & (TypeAttributes.Public | TypeAttributes.Interface)) == TypeAttributes.Public &&
+                        reader.IsSystemObjectOrThrow(typeDef))
+                    {
+                        return true;
+                    }
+                }
+                catch (BadImageFormatException)
+                {
+                }
+            }
+
+            return false;
+        }
+
+        /// <exception cref="BadImageFormatException">An exception from metadata reader.</exception>
+        private static bool IsSystemObjectOrThrow(this MetadataReader reader, TypeDefinition typeDef)
+        {
+            return reader.StringComparer.Equals(typeDef.Name, "Object") &&
+                reader.StringComparer.Equals(typeDef.Namespace, "System");
+        }
     }
 }

src/Compilers/Core/Portable/MetadataReader/PEAssembly.cs

@@ -167,13 +167,8 @@ internal bool DeclaresTheObjectClass
             {
                 if (_lazyDeclaresTheObjectClass == ThreeState.Unknown)
                 {
-                    if (!_modules[0].FindSystemObjectTypeDef().IsNil)
-                    {
-                        _lazyDeclaresTheObjectClass = ThreeState.True;
-                        return true;
-                    }
-
-                    _lazyDeclaresTheObjectClass = ThreeState.False;
+                    var value = _modules[0].MetadataReader.DeclaresTheObjectClass();
+                    _lazyDeclaresTheObjectClass = value.ToThreeState();
                 }
 
                 return _lazyDeclaresTheObjectClass == ThreeState.True;

src/Compilers/Core/Portable/MetadataReader/PEModule.cs

@@ -500,37 +500,6 @@ public bool HasGenericParametersOrThrow(TypeDefinitionHandle typeDef)
             extends = row.BaseType;
         }
 
-        internal TypeDefinitionHandle FindSystemObjectTypeDef()
-        {
-            MetadataReader reader = MetadataReader;
-
-            foreach (TypeDefinitionHandle handle in reader.TypeDefinitions)
-            {
-                try
-                {
-                    var typeDef = reader.GetTypeDefinition(handle);
-
-                    if (typeDef.BaseType.IsNil &&
-                        (typeDef.Attributes & (TypeAttributes.Public | TypeAttributes.Interface)) == TypeAttributes.Public &&
-                        IsSystemObjectOrThrow(typeDef))
-                    {
-                        return handle;
-                    }
-                }
-                catch (BadImageFormatException)
-                { }
-            }
-
-            return default(TypeDefinitionHandle);
-        }
-
-        /// <exception cref="BadImageFormatException">An exception from metadata reader.</exception>
-        private bool IsSystemObjectOrThrow(TypeDefinition typeDef)
-        {
-            return MetadataReader.StringComparer.Equals(typeDef.Name, "Object") &&
-                   MetadataReader.StringComparer.Equals(typeDef.Namespace, "System");
-        }
-
         /// <exception cref="BadImageFormatException">An exception from metadata reader.</exception>
         internal bool IsNestedTypeDefOrThrow(TypeDefinitionHandle typeDef)
         {

src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/ReferencedModulesTests.cs

@@ -13,6 +13,7 @@
 using Roslyn.Test.PdbUtilities;
 using Roslyn.Test.Utilities;
 using Xunit;
+using Resources = Microsoft.CodeAnalysis.ExpressionEvaluator.UnitTests.Resources;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
 {
@@ -463,7 +464,7 @@ .maxstack  1
         /// compiled against portable framework assemblies.
         /// </summary>
         [WorkItem(1150981)]
-        [Fact(Skip = "1150981")]
+        [Fact]
         public void MissingMscorlib()
         {
             var sourceA =
@@ -507,6 +508,10 @@ class C
             var referenceB = AssemblyMetadata.CreateFromImage(exeBytesB).GetReference(display: assemblyNameB);
             var moduleB = referenceB.ToModuleInstance(exeBytesB, new SymReader(pdbBytesB));
 
+            // Include an empty assembly to verify that not all assemblies
+            // with no references are treated as mscorlib.
+            var referenceC = AssemblyMetadata.CreateFromImage(Resources.Empty).GetReference();
+
             // At runtime System.Runtime.dll contract assembly is replaced
             // by mscorlib.dll and System.Runtime.dll facade assemblies.
             var moduleBuilder = ArrayBuilder<ModuleInstance>.GetInstance();
@@ -514,6 +519,7 @@ class C
             moduleBuilder.Add(SystemRuntimeFacadeRef.ToModuleInstance(null, null));
             moduleBuilder.Add(moduleA);
             moduleBuilder.Add(moduleB);
+            moduleBuilder.Add(referenceC.ToModuleInstance(null, null));
             var modules = moduleBuilder.ToImmutableAndFree();
 
             using (var runtime = new RuntimeInstance(modules))

src/ExpressionEvaluator/CSharp/Test/ExpressionCompiler/WinMdTests.cs

@@ -6,15 +6,15 @@
 using Microsoft.CodeAnalysis.ExpressionEvaluator;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.VisualStudio.Debugger.Evaluation;
+using Roslyn.Test.PdbUtilities;
 using Roslyn.Test.Utilities;
+using Roslyn.Utilities;
 using System;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Reflection.Metadata;
 using Xunit;
 using Resources = Microsoft.CodeAnalysis.ExpressionEvaluator.UnitTests.Resources;
-using Roslyn.Test.PdbUtilities;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
 {

src/ExpressionEvaluator/Core/Source/ExpressionCompiler/MetadataUtilities.cs

@@ -86,6 +86,7 @@ internal static class MetadataUtilities
             // Build assembly references from modules in primary module manifests.
             var referencesBuilder = ArrayBuilder<MetadataReference>.GetInstance();
             var identitiesBuilder = (identityComparer == null) ? null : ArrayBuilder<AssemblyIdentity>.GetInstance();
+            AssemblyIdentity corLibrary = null;
 
             foreach (var metadata in metadataBuilder)
             {
@@ -95,8 +96,17 @@ internal static class MetadataUtilities
                 }
                 if (identitiesBuilder != null)
                 {
-                    var identity = metadata.MetadataReader.ReadAssemblyIdentityOrThrow();
+                    var reader = metadata.MetadataReader;
+                    var identity = reader.ReadAssemblyIdentityOrThrow();
                     identitiesBuilder.Add(identity);
+                    // If this assembly has no references, and declares
+                    // System.Object, assume it is the COR library.
+                    if ((corLibrary == null) &&
+                        (reader.AssemblyReferences.Count == 0) &&
+                        reader.DeclaresTheObjectClass())
+                    {
+                        corLibrary = identity;
+                    }
                 }
                 var reference = MakeAssemblyMetadata(metadata, modulesByName);
                 referencesBuilder.Add(reference);
@@ -112,6 +122,15 @@ internal static class MetadataUtilities
                     var referencedModules = ArrayBuilder<AssemblyIdentity>.GetInstance();
                     referencedModules.Add(module.MetadataReader.ReadAssemblyIdentityOrThrow());
                     referencedModules.AddRange(module.MetadataReader.GetReferencedAssembliesOrThrow());
+                    // Ensure COR library is included, otherwise any compilation will fail.
+                    // (Note, an equivalent assembly may have already been included from
+                    // GetReferencedAssembliesOrThrow above but RemoveUnreferencedModules
+                    // allows duplicates.)
+                    Debug.Assert(corLibrary != null);
+                    if (corLibrary != null)
+                    {
+                        referencedModules.Add(corLibrary);
+                    }
                     RemoveUnreferencedModules(referencesBuilder, identitiesBuilder, identityComparer, referencedModules);
                     referencedModules.Free();
                 }

src/ExpressionEvaluator/Core/Test/ExpressionCompiler/ExpressionCompilerTestUtilities.csproj

@@ -77,6 +77,7 @@
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />
+    <None Include="Resources\Empty.dll" />
     <None Include="Resources\LibraryA.winmd" />
     <None Include="Resources\LibraryB.winmd" />
     <None Include="Resources\NoValidTables.metadata" />

src/ExpressionEvaluator/Core/Test/ExpressionCompiler/Resources.Designer.cs

@@ -60,6 +60,16 @@ internal class Resources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized resource of type System.Byte[].
+        /// </summary>
+        internal static byte[] Empty {
+            get {
+                object obj = ResourceManager.GetObject("Empty", resourceCulture);
+                return ((byte[])(obj));
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized resource of type System.Byte[].
         /// </summary>

src/ExpressionEvaluator/Core/Test/ExpressionCompiler/Resources.resx

@@ -119,6 +119,14 @@
   </resheader>
   <assembly alias="System.Windows.Forms" name="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
 <!--
+copy NUL Empty.txt
+resgen.exe Empty.txt
+al.exe /embed:Empty.resources /t:lib /out:Empty.dll
+-->
+  <data name="Empty" type="System.Resources.ResXFileRef, System.Windows.Forms">
+    <value>Resources\Empty.dll;System.Byte[], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </data>
+  <!--
 echo namespace Windows.Data.Text { public sealed class TextSegment { } } > Windows.Data.cs
 csc /t:winmdobj Windows.Data.cs
 winmdexp.exe /r:"%ProgramFiles(x86)%\Reference Assemblies\Microsoft\Framework\.NETCore\v4.5\mscorlib.dll" /r:"%ProgramFiles(x86)%\Reference Assemblies\Microsoft\Framework\.NETCore\v4.5\System.Runtime.dll" /r:"%ProgramFiles(x86)%\Microsoft SDKs\Portable\v14.0\110C4FEFF2BA61C0746933A9ED6E248D\Windows.winmd" /out:Windows.Data.winmd Windows.Data.winmdobj