// Add all appropriate references to the compilation and set it as our final compilation
            // state.
            private async Task <Compilation> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                try
                {
                    var newReferences = new List <MetadataReference>();
                    newReferences.AddRange(this.ProjectState.MetadataReferences);

                    foreach (var projectReference in this.ProjectState.ProjectReferences)
                    {
                        var referencedProject = solution.GetProject(projectReference.ProjectId);

                        // Even though we're creating a final compilation (vs. an in progress compilation),
                        // it's possible that the target project has been removed.
                        if (referencedProject != null)
                        {
                            // If both projects are submissions, we'll count this as a previous submission link
                            // instead of a regular metadata reference
                            if (referencedProject.IsSubmission)
                            {
                                // if the referenced project is a submission project must be a submission as well:
                                Debug.Assert(this.ProjectState.IsSubmission);

                                var previousSubmissionCompilation =
                                    await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);

                                compilation = compilation.WithPreviousSubmission(previousSubmissionCompilation);
                            }
                            else
                            {
                                var metadataReference = await solution.GetMetadataReferenceAsync(
                                    projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                                // The compilation doesn't want to receive a null entry in the set
                                // of references it is constructed with. A reference can fail to be
                                // created if a skeleton assembly could not be constructed.
                                if (metadataReference != null)
                                {
                                    newReferences.Add(metadataReference);
                                }
                            }
                        }
                    }

                    if (!Enumerable.SequenceEqual(compilation.References, newReferences))
                    {
                        compilation = compilation.WithReferences(newReferences);
                    }

                    this.WriteState(new FinalState(this.Retain(solution, compilation)));

                    return(compilation);
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                    {
                        throw ExceptionUtilities.Unreachable;
                    }
            }
            // Add all appropriate references to the compilation and set it as our final compilation
            // state.
            private async Task<Compilation> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                var newReferences = new List<MetadataReference>();
                newReferences.AddRange(this.ProjectState.MetadataReferences);

                foreach (var projectReference in this.ProjectState.ProjectReferences)
                {
                    var referencedProject = solution.GetProject(projectReference.ProjectId);

                    // Even though we're creating a final compilation (vs. an in progress compilation),
                    // it's possible that the target project has been removed.
                    if (referencedProject != null)
                    {
                        // If both projects are submissions, we'll count this as a previous submission link
                        // instead of a regular metadata reference
                        if (referencedProject.IsSubmission)
                        {
                            // if the referenced project is a submission project must be a submission as well:
                            Debug.Assert(this.ProjectState.IsSubmission);

                            var previousSubmissionCompilation =
                                await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);
                            compilation = compilation.WithPreviousSubmission(previousSubmissionCompilation);
                        }
                        else
                        {
                            var metadataReference = await solution.GetMetadataReferenceAsync(
                                projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                            // The compilation doesn't want to receive a null entry in the set
                            // of references it is constructed with. A reference can fail to be
                            // created if a skeleton assembly could not be constructed.
                            if (metadataReference != null)
                            {
                                newReferences.Add(metadataReference);
                            }
                        }
                    }
                }

                if (!Enumerable.SequenceEqual(compilation.References, newReferences))
                {
                    compilation = compilation.WithReferences(newReferences);
                }

                this.WriteState(new FinalState(this.Retain(solution, compilation)));

                return compilation;
            }
Beispiel #3
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            /// <summary>
            /// Add all appropriate references to the compilation and set it as our final compilation
            /// state.
            /// </summary>
            private async Task <CompilationInfo> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                try
                {
                    bool hasCompleteReferences = true;
                    var  newReferences         = new List <MetadataReference>();
                    newReferences.AddRange(this.ProjectState.MetadataReferences);

                    foreach (var projectReference in this.ProjectState.ProjectReferences)
                    {
                        var referencedProject = solution.GetProject(projectReference.ProjectId);

                        // Even though we're creating a final compilation (vs. an in progress compilation),
                        // it's possible that the target project has been removed.
                        if (referencedProject != null)
                        {
                            // If both projects are submissions, we'll count this as a previous submission link
                            // instead of a regular metadata reference
                            if (referencedProject.IsSubmission)
                            {
                                // if the referenced project is a submission project must be a submission as well:
                                Debug.Assert(this.ProjectState.IsSubmission);

                                var previousSubmissionCompilation =
                                    await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);

                                compilation = compilation.WithScriptCompilationInfo(
                                    compilation.ScriptCompilationInfo.WithPreviousScriptCompilation(previousSubmissionCompilation));
                            }
                            else
                            {
                                var metadataReference = await solution.GetMetadataReferenceAsync(
                                    projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                                // A reference can fail to be created if a skeleton assembly could not be constructed.
                                if (metadataReference != null)
                                {
                                    newReferences.Add(metadataReference);
                                }
                                else
                                {
                                    hasCompleteReferences = false;
                                }
                            }
                        }
                    }

                    if (!Enumerable.SequenceEqual(compilation.References, newReferences))
                    {
                        compilation = compilation.WithReferences(newReferences);
                    }

                    this.WriteState(new FinalState(State.CreateValueSource(compilation, solution.Services), hasCompleteReferences), solution);

                    return(new CompilationInfo(compilation, hasCompleteReferences));
                }
                catch (Exception e) when(FatalError.ReportUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }
            private async Task<Compilation> GetOrBuildDeclarationCompilationAsync(Solution solution, CancellationToken cancellationToken)
            {
                try
                {
                    cancellationToken.ThrowIfCancellationRequested();

                    using (await this.buildLock.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
                    {
                        var state = this.ReadState();

                        // we are already in the final stage. just return it.
                        var compilation = state.FinalCompilation.GetValue(cancellationToken);
                        if (compilation != null)
                        {
                            return compilation;
                        }

                        compilation = state.Compilation.GetValue(cancellationToken);
                        if (compilation == null)
                        {
                            // let's see whether we have declaration only compilation
                            if (state.DeclarationOnlyCompilation != null)
                            {
                                // okay, move to full declaration state. do this so that declaration only compilation never
                                // realize symbols.
                                this.WriteState(new FullDeclarationState(this.Retain(solution, state.DeclarationOnlyCompilation)));
                                return state.DeclarationOnlyCompilation;
                            }

                            // We've got nothing.  Build it from scratch :(
                            return await BuildDeclarationCompilationFromScratchAsync(solution, cancellationToken).ConfigureAwait(false);
                        }
                        else if (state is FullDeclarationState)
                        {
                            // we have full declaration, just use it.
                            return state.Compilation.GetValue(cancellationToken);
                        }
                        else if (state is InProgressState)
                        {
                            // We have an in progress compilation.  Build off of that.
                            return await BuildDeclarationCompilationFromInProgressAsync(solution, state as InProgressState, compilation, cancellationToken).ConfigureAwait(false);
                        }
                        else
                        {
                            throw Contract.Unreachable;
                        }
                    }
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            private async Task<Compilation> GetOrBuildCompilationAsync(
                Solution solution,
                bool lockGate,
                CancellationToken cancellationToken)
            {
                try
                {
                    using (Logger.LogBlock(FunctionId.Workspace_Project_CompilationTracker_BuildCompilationAsync,
                                           logBuildCompilationAsync, this.ProjectState, cancellationToken))
                    {
                        cancellationToken.ThrowIfCancellationRequested();

                        var state = this.ReadState();

                        // Try to get the built compilation.  If it exists, then we can just return that.
                        var finalCompilation = state.FinalCompilation.GetValue(cancellationToken);
                        if (finalCompilation != null)
                        {
                            return finalCompilation;
                        }

                        // Otherwise, we actually have to build it.  Ensure that only one thread is trying to
                        // build this compilation at a time.
                        if (lockGate)
                        {
                            using (await this.buildLock.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
                            {
                                return await BuildCompilationAsync(solution, cancellationToken).ConfigureAwait(false);
                            }
                        }
                        else
                        {
                            return await BuildCompilationAsync(solution, cancellationToken).ConfigureAwait(false);
                        }
                    }
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            /// <summary>
            /// Builds the compilation matching the project state. In the process of building, also
            /// produce in progress snapshots that can be accessed from other threads.
            /// </summary>
            private Task<Compilation> BuildCompilationAsync(
                Solution solution,
                CancellationToken cancellationToken)
            {
                cancellationToken.ThrowIfCancellationRequested();

                var state = this.ReadState();

                // if we already have a compilation, we must be already done!  This can happen if two
                // threads were waiting to build, and we came in after the other succeeded.
                var compilation = state.FinalCompilation.GetValue(cancellationToken);
                if (compilation != null)
                {
                    return SpecializedTasks.FromResult(compilation);
                }

                compilation = state.Compilation.GetValue(cancellationToken);
                if (compilation == null)
                {
                    // this can happen if compilation is already kicked out from the cache.
                    // check whether the state we have support declaration only compilation
                    if (state.DeclarationOnlyCompilation != null)
                    {
                        // we have declaration only compilation. build final one from it.
                        return FinalizeCompilationAsync(solution, state.DeclarationOnlyCompilation, cancellationToken);
                    }

                    // We've got nothing.  Build it from scratch :(
                    return BuildCompilationFromScratchAsync(solution, state, cancellationToken);
                }
                else if (state is FullDeclarationState)
                {
                    // We have a declaration compilation, use it to reconstruct the final compilation
                    return this.FinalizeCompilationAsync(solution, compilation, cancellationToken);
                }
                else if (state is InProgressState)
                {
                    // We have an in progress compilation.  Build off of that.
                    return BuildFinalStateFromInProgressStateAsync(solution, state as InProgressState, compilation, cancellationToken);
                }
                else
                {
                    throw Contract.Unreachable;
                }
            }

            private async Task<Compilation> BuildCompilationFromScratchAsync(
                Solution solution, State state, CancellationToken cancellationToken)
            {
                try
                {
                    var compilation = await BuildDeclarationCompilationFromScratchAsync(solution, cancellationToken).ConfigureAwait(false);
                    return await FinalizeCompilationAsync(solution, compilation, cancellationToken).ConfigureAwait(false);
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            private async Task<Compilation> BuildDeclarationCompilationFromScratchAsync(
                Solution solution, CancellationToken cancellationToken)
            {
                try
                {
                    var compilation = CreateEmptyCompilation(solution);

                    foreach (var document in this.ProjectState.OrderedDocumentStates)
                    {
                        cancellationToken.ThrowIfCancellationRequested();
                        compilation = compilation.AddSyntaxTrees(await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false));
                    }

                    this.WriteState(new FullDeclarationState(this.Retain(solution, compilation)));
                    return compilation;
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            private Compilation CreateEmptyCompilation(Solution solution)
            {
                var compilationFactory = this.ProjectState.LanguageServices.GetService<ICompilationFactoryService>();

                if (this.ProjectState.IsSubmission)
                {
                    return compilationFactory.CreateSubmissionCompilation(
                        this.ProjectState.AssemblyName,
                        this.ProjectState.CompilationOptions,
                        this.ProjectState.HostObjectType);
                }
                else
                {
                    return compilationFactory.CreateCompilation(
                        this.ProjectState.AssemblyName,
                        this.ProjectState.CompilationOptions);
                }
            }

            private async Task<Compilation> BuildFinalStateFromInProgressStateAsync(
                Solution solution, InProgressState state, Compilation inProgressCompilation, CancellationToken cancellationToken)
            {
                try
                {
                    var compilation = await BuildDeclarationCompilationFromInProgressAsync(solution, state, inProgressCompilation, cancellationToken).ConfigureAwait(false);
                    return await FinalizeCompilationAsync(solution, compilation, cancellationToken).ConfigureAwait(false);
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            private async Task<Compilation> BuildDeclarationCompilationFromInProgressAsync(
                Solution solution, InProgressState state, Compilation inProgressCompilation, CancellationToken cancellationToken)
            {
                try
                {
                    Contract.Requires(inProgressCompilation != null);
                    var intermediateProjects = state.IntermediateProjects;

                    while (intermediateProjects.Length > 0)
                    {
                        cancellationToken.ThrowIfCancellationRequested();

                        var intermediateProject = intermediateProjects[0];
                        var inProgressProject = intermediateProject.Item1;
                        var action = intermediateProject.Item2;

                        inProgressCompilation = await action.InvokeAsync(inProgressCompilation, cancellationToken).ConfigureAwait(false);
                        intermediateProjects = intermediateProjects.RemoveAt(0);

                        this.WriteState(State.Create(
                            this.Retain(solution, inProgressCompilation),
                            intermediateProjects));
                    }

                    return inProgressCompilation;
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            // Add all appropriate references to the compilation and set it as our final compilation
            // state.
            private async Task<Compilation> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                try
                {
                    var newReferences = new List<MetadataReference>();
                    newReferences.AddRange(this.ProjectState.MetadataReferences);

                    foreach (var projectReference in this.ProjectState.ProjectReferences)
                    {
                        var referencedProject = solution.GetProject(projectReference.ProjectId);

                        // Even though we're creating a final compilation (vs. an in progress compilation),
                        // it's possible that the target project has been removed.
                        if (referencedProject != null)
                        {
                            // If both projects are submissions, we'll count this as a previous submission link
                            // instead of a regular metadata reference
                            if (referencedProject.IsSubmission)
                            {
                                // if the referenced project is a submission project must be a submission as well:
                                Debug.Assert(this.ProjectState.IsSubmission);

                                var previousSubmissionCompilation =
                                    await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);
                                compilation = compilation.WithPreviousSubmission(previousSubmissionCompilation);
                            }
                            else
                            {
                                var metadataReference = await solution.GetMetadataReferenceAsync(
                                    projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                                // The compilation doesn't want to receive a null entry in the set
                                // of references it is constructed with. A reference can fail to be
                                // created if a skeleton assembly could not be constructed.
                                if (metadataReference != null)
                                {
                                    newReferences.Add(metadataReference);
                                }
                            }
                        }
                    }

                    if (!Enumerable.SequenceEqual(compilation.References, newReferences))
                    {
                        compilation = compilation.WithReferences(newReferences);
                    }

                    this.WriteState(new FinalState(this.Retain(solution, compilation)));

                    return compilation;
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            /// <summary>
            /// Get a metadata reference to this compilation info's compilation with respect to
            /// another project. For cross language references produce a skeletal assembly. If the
            /// compilation is not available, it is built. If a skeletal assembly reference is
            /// needed and does not exist, it is also built.
            /// </summary>
            internal async Task<MetadataReference> GetMetadataReferenceAsync(
                Solution solution,
                ProjectState fromProject,
                ProjectReference projectReference,
                CancellationToken cancellationToken)
            {
                try
                {
                    Compilation compilation;

                    // if we already have the compilation and its right kind then use it.
                    if (this.ProjectState.LanguageServices == fromProject.LanguageServices
                        && this.TryGetCompilation(out compilation))
                    {
                        return compilation.ToMetadataReference(projectReference.Aliases, projectReference.EmbedInteropTypes);
                    }

                    // If same language then we can wrap the other project's compilation into a compilation reference
                    if (this.ProjectState.LanguageServices == fromProject.LanguageServices)
                    {
                        // otherwise, base it off the compilation by building it first.
                        compilation = await this.GetCompilationAsync(solution, cancellationToken).ConfigureAwait(false);
                        return compilation.ToMetadataReference(projectReference.Aliases, projectReference.EmbedInteropTypes);
                    }
                    else
                    {
                        // otherwise get a metadata only image reference that is built by emitting the metadata from the referenced project's compilation and re-importing it.
                        return await this.GetMetadataOnlyImageReferenceAsync(solution, projectReference, cancellationToken).ConfigureAwait(false);
                    }
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            /// <summary>
            /// Attempts to get (without waiting) a metadata reference to a possibly in progress
            /// compilation. Actual compilation references are preferred over skeletal assembly
            /// references.  Could potentially return null if nothing can be provided.
            /// </summary>
            internal MetadataReference GetPartialMetadataReference(Solution solution, ProjectState fromProject, ProjectReference projectReference, CancellationToken cancellationToken)
            {
                var state = this.ReadState();

                // get compilation in any state it happens to be in right now.
                Compilation compilation;
                if (state.Compilation.TryGetValue(out compilation)
                    && compilation != null
                    && this.ProjectState.LanguageServices == fromProject.LanguageServices)
                {
                    // if we have a compilation and its the correct language, use a simple compilation reference
                    return compilation.ToMetadataReference(projectReference.Aliases, projectReference.EmbedInteropTypes);
                }

                return null;
            }

            /// <summary>
            /// Gets a metadata reference to the metadata-only-image corresponding to the compilation.
            /// </summary>
            private async Task<MetadataReference> GetMetadataOnlyImageReferenceAsync(
                Solution solution, ProjectReference projectReference, CancellationToken cancellationToken)
            {
                try
                {
                    using (Logger.LogBlock(FunctionId.Workspace_SkeletonAssembly_GetMetadataOnlyImage, cancellationToken))
                    {
                        var projectId = this.ProjectState.Id;
                        var version = await this.GetDependentSemanticVersionAsync(solution, cancellationToken).ConfigureAwait(false);

                        // get or build compilation up to decleration state. this compilation will be used to provide live xml doc comment
                        var declarationCompilation = await this.GetOrBuildDeclarationCompilationAsync(solution, cancellationToken: cancellationToken).ConfigureAwait(false);

                        MetadataReference reference;
                        if (!MetadataOnlyReference.TryGetReference(solution, projectReference, declarationCompilation, version, out reference))
                        {
                            // using async build lock so we don't get multiple consumers attempting to build metadata-only images for the same compilation.
                            using (await this.buildLock.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
                            {
                                // okay, we still don't have one. bring the compilation to final state since we are going to use it to create skeleton assembly
                                var compilation = await this.GetOrBuildCompilationAsync(solution, lockGate: false, cancellationToken: cancellationToken).ConfigureAwait(false);
                                reference = MetadataOnlyReference.GetOrBuildReference(solution, projectReference, compilation, version, cancellationToken);
                            }
                        }

                        return reference;
                    }
                }
                catch (Exception e) if (ExceptionHelpers.CrashUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }

            /// <summary>
            /// Converts a compilation into a ValueSource employing an external compilation retention policy.
            /// </summary>
            private ValueSource<Compilation> Retain(Solution solution, Compilation compilation)
            {
                var cache = solution.Services.CompilationCacheService;
                if (cache != null)
                {
                    return new CachedObjectSource<Compilation>(compilation, cache);
                }
                else
                {
                    return new ConstantValueSource<Compilation>(compilation);
                }
            }

            #region Versions

            // Dependent Versions are stored on compilation tracker so they are more likely to survive when unrelated solution branching occurs.

            private AsyncLazy<VersionStamp> lazyDependentVersion;
            private AsyncLazy<VersionStamp> lazyDependentSemanticVersion;

            internal async Task<VersionStamp> GetDependentVersionAsync(Solution solution, CancellationToken cancellationToken)
            {
                if (this.lazyDependentVersion == null)
                {
                    // note: solution is captured here, but it will go away once GetValueAsync executes.
                    Interlocked.CompareExchange(ref this.lazyDependentVersion, new AsyncLazy<VersionStamp>(c => ComputeDependentVersionAsync(solution, c), cacheResult: true), null);
                }

                return await this.lazyDependentVersion.GetValueAsync(cancellationToken).ConfigureAwait(false);
            }
Beispiel #5
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        private void ValidateSolutionAndCompilations(Solution solution)
        {
            foreach (var project in solution.Projects)
            {
                Assert.True(solution.ContainsProject(project.Id), "Solution was expected to have project " + project.Id);
                Assert.Equal(project, solution.GetProject(project.Id));

                // these won't always be unique in real-world but should be for these tests
                Assert.Equal(project, solution.GetProjectsByName(project.Name).FirstOrDefault());

                var compilation = project.GetCompilationAsync().Result;
                Assert.NotNull(compilation);

                // check that the options are the same
                Assert.Equal(project.CompilationOptions, compilation.Options);

                // check that all known metadata references are present in the compilation
                foreach (var meta in project.MetadataReferences)
                {
                    Assert.True(compilation.References.Contains(meta), "Compilation references were expected to contain " + meta);
                }

                // check that all project-to-project reference metadata is present in the compilation
                foreach (var referenced in project.ProjectReferences)
                {
                    if (solution.ContainsProject(referenced.ProjectId))
                    {
                        var referencedMetadata = solution.GetMetadataReferenceAsync(referenced, solution.GetProjectState(project.Id), CancellationToken.None).Result;
                        Assert.NotNull(referencedMetadata);
                        var compilationReference = referencedMetadata as CompilationReference;
                        if (compilationReference != null)
                        {
                            compilation.References.Single(r =>
                            {
                                var cr = r as CompilationReference;
                                return cr != null && cr.Compilation == compilationReference.Compilation;
                            });
                        }
                    }
                }

                // check that the syntax trees are the same
                var docs = project.Documents.ToList();
                var trees = compilation.SyntaxTrees.ToList();
                Assert.Equal(docs.Count, trees.Count);

                foreach (var doc in docs)
                {
                    Assert.True(trees.Contains(doc.GetSyntaxTreeAsync().Result), "trees list was expected to contain the syntax tree of doc");
                }
            }
        }
            /// <summary>
            /// Add all appropriate references to the compilation and set it as our final compilation
            /// state.
            /// </summary>
            private async Task<CompilationInfo> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                try
                {
                    // if HasAllInformation is false, then this project is always not completed.
                    bool hasSuccessfullyLoaded = this.ProjectState.HasAllInformation;

                    var newReferences = new List<MetadataReference>();
                    var metadataReferenceToProjectId = new Dictionary<MetadataReference, ProjectId>();
                    newReferences.AddRange(this.ProjectState.MetadataReferences);

                    foreach (var projectReference in this.ProjectState.ProjectReferences)
                    {
                        var referencedProject = solution.GetProject(projectReference.ProjectId);

                        // Even though we're creating a final compilation (vs. an in progress compilation),
                        // it's possible that the target project has been removed.
                        if (referencedProject != null)
                        {
                            // If both projects are submissions, we'll count this as a previous submission link
                            // instead of a regular metadata reference
                            if (referencedProject.IsSubmission)
                            {
                                // if the referenced project is a submission project must be a submission as well:
                                Debug.Assert(this.ProjectState.IsSubmission);

                                var previousSubmissionCompilation =
                                    await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);

                                compilation = compilation.WithScriptCompilationInfo(
                                    compilation.ScriptCompilationInfo.WithPreviousScriptCompilation(previousSubmissionCompilation));
                            }
                            else
                            {
                                var metadataReference = await solution.GetMetadataReferenceAsync(
                                    projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                                // A reference can fail to be created if a skeleton assembly could not be constructed.
                                if (metadataReference != null)
                                {
                                    newReferences.Add(metadataReference);
                                    metadataReferenceToProjectId.Add(metadataReference, projectReference.ProjectId);
                                }
                                else
                                {
                                    hasSuccessfullyLoaded = false;
                                }
                            }
                        }
                    }

                    compilation = UpdateCompilationWithNewReferencesAndRecordAssemblySymbols(compilation, newReferences, metadataReferenceToProjectId);

                    bool hasSuccessfullyLoadedTransitively = !HasMissingReferences(compilation, this.ProjectState.MetadataReferences) && await ComputeHasSuccessfullyLoadedTransitivelyAsync(solution, hasSuccessfullyLoaded, cancellationToken).ConfigureAwait(false);

                    this.WriteState(new FinalState(State.CreateValueSource(compilation, solution.Services), hasSuccessfullyLoadedTransitively), solution);

                    return new CompilationInfo(compilation, hasSuccessfullyLoadedTransitively);
                }
                catch (Exception e) when (FatalError.ReportUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }
            /// <summary>
            /// Add all appropriate references to the compilation and set it as our final compilation
            /// state.
            /// </summary>
            private async Task <CompilationInfo> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                try
                {
                    // if HasAllInformation is false, then this project is always not completed.
                    bool hasSuccessfullyLoaded = this.ProjectState.HasAllInformation;

                    var newReferences = new List <MetadataReference>();
                    var metadataReferenceToProjectId = new Dictionary <MetadataReference, ProjectId>();
                    newReferences.AddRange(this.ProjectState.MetadataReferences);

                    foreach (var projectReference in this.ProjectState.ProjectReferences)
                    {
                        var referencedProject = solution.GetProject(projectReference.ProjectId);

                        // Even though we're creating a final compilation (vs. an in progress compilation),
                        // it's possible that the target project has been removed.
                        if (referencedProject != null)
                        {
                            // If both projects are submissions, we'll count this as a previous submission link
                            // instead of a regular metadata reference
                            if (referencedProject.IsSubmission)
                            {
                                // if the referenced project is a submission project must be a submission as well:
                                Debug.Assert(this.ProjectState.IsSubmission);

                                var previousSubmissionCompilation =
                                    await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);

                                compilation = compilation.WithScriptCompilationInfo(
                                    compilation.ScriptCompilationInfo.WithPreviousScriptCompilation(previousSubmissionCompilation));
                            }
                            else
                            {
                                var metadataReference = await solution.GetMetadataReferenceAsync(
                                    projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                                // A reference can fail to be created if a skeleton assembly could not be constructed.
                                if (metadataReference != null)
                                {
                                    newReferences.Add(metadataReference);
                                    metadataReferenceToProjectId.Add(metadataReference, projectReference.ProjectId);
                                }
                                else
                                {
                                    hasSuccessfullyLoaded = false;
                                }
                            }
                        }
                    }

                    compilation = UpdateCompilationWithNewReferencesAndRecordAssemblySymbols(compilation, newReferences, metadataReferenceToProjectId);

                    bool hasSuccessfullyLoadedTransitively = !HasMissingReferences(compilation, this.ProjectState.MetadataReferences) && await ComputeHasSuccessfullyLoadedTransitivelyAsync(solution, hasSuccessfullyLoaded, cancellationToken).ConfigureAwait(false);

                    this.WriteState(new FinalState(State.CreateValueSource(compilation, solution.Services), hasSuccessfullyLoadedTransitively), solution);

                    return(new CompilationInfo(compilation, hasSuccessfullyLoadedTransitively));
                }
                catch (Exception e) when(FatalError.ReportUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }
            /// <summary>
            /// Add all appropriate references to the compilation and set it as our final compilation
            /// state.
            /// </summary>
            private async Task<CompilationInfo> FinalizeCompilationAsync(
                Solution solution,
                Compilation compilation,
                CancellationToken cancellationToken)
            {
                try
                {
                    bool hasCompleteReferences = true;
                    var newReferences = new List<MetadataReference>();
                    newReferences.AddRange(this.ProjectState.MetadataReferences);

                    foreach (var projectReference in this.ProjectState.ProjectReferences)
                    {
                        var referencedProject = solution.GetProject(projectReference.ProjectId);

                        // Even though we're creating a final compilation (vs. an in progress compilation),
                        // it's possible that the target project has been removed.
                        if (referencedProject != null)
                        {
                            // If both projects are submissions, we'll count this as a previous submission link
                            // instead of a regular metadata reference
                            if (referencedProject.IsSubmission)
                            {
                                // if the referenced project is a submission project must be a submission as well:
                                Debug.Assert(this.ProjectState.IsSubmission);

                                var previousSubmissionCompilation =
                                    await solution.GetCompilationAsync(projectReference.ProjectId, cancellationToken).ConfigureAwait(false);

                                compilation = compilation.WithScriptCompilationInfo(
                                    compilation.ScriptCompilationInfo.WithPreviousScriptCompilation(previousSubmissionCompilation));
                            }
                            else
                            {
                                var metadataReference = await solution.GetMetadataReferenceAsync(
                                    projectReference, this.ProjectState, cancellationToken).ConfigureAwait(false);

                                // A reference can fail to be created if a skeleton assembly could not be constructed.
                                if (metadataReference != null)
                                {
                                    newReferences.Add(metadataReference);
                                }
                                else
                                {
                                    hasCompleteReferences = false;
                                }
                            }
                        }
                    }

                    if (!Enumerable.SequenceEqual(compilation.ExternalReferences, newReferences))
                    {
                        compilation = compilation.WithReferences(newReferences);
                    }

                    this.WriteState(new FinalState(State.CreateValueSource(compilation, solution.Services), hasCompleteReferences), solution);

                    return new CompilationInfo(compilation, hasCompleteReferences);
                }
                catch (Exception e) when (FatalError.ReportUnlessCanceled(e))
                {
                    throw ExceptionUtilities.Unreachable;
                }
            }