enable semantic diagnostics for script file for misc workspace.

now, C#/VB script files in misc workspace will get semantic errors as well as syntax errors.

any language such as F# if document is added to misc workspace with SourceCodeKind.Script, they will automatically get semantic errors as well.

this PR doesn't address changes propagations for #load which was never supported for existing C#/VB script support.

src/VisualStudio/Core/Def/Implementation/ProjectSystem/MiscellaneousFilesWorkspace.cs

@@ -82,7 +82,9 @@ public void RegisterLanguage(Guid languageGuid, string languageName, string scri
 
         internal void StartSolutionCrawler()
         {
-            DiagnosticProvider.Enable(this, DiagnosticProvider.Options.Syntax);
+            // misc workspace will enable syntax errors and semantic errors for script files for
+            // all participating projects in the workspace
+            DiagnosticProvider.Enable(this, DiagnosticProvider.Options.Syntax | DiagnosticProvider.Options.ScriptSemantic);
         }
 
         internal void StopSolutionCrawler()
@@ -352,6 +354,8 @@ private ProjectInfo CreateProjectInfoForDocument(string filePath)
             var languageInformation = TryGetLanguageInformation(filePath);
             Contract.ThrowIfNull(languageInformation);
 
+            var fileExtension = PathUtilities.GetExtension(filePath);
+
             var languageServices = Services.GetLanguageServices(languageInformation.LanguageName);
             var compilationOptionsOpt = languageServices.GetService<ICompilationFactoryService>()?.GetDefaultCompilationOptions();
 
@@ -361,7 +365,7 @@ private ProjectInfo CreateProjectInfoForDocument(string filePath)
 
             if (parseOptionsOpt != null &&
                 compilationOptionsOpt != null &&
-                PathUtilities.GetExtension(filePath) == languageInformation.ScriptExtension)
+                fileExtension == languageInformation.ScriptExtension)
             {
                 parseOptionsOpt = parseOptionsOpt.WithKind(SourceCodeKind.Script);
 
@@ -391,10 +395,11 @@ private ProjectInfo CreateProjectInfoForDocument(string filePath)
             var projectId = ProjectId.CreateNewId(debugName: "Miscellaneous Files Project for " + filePath);
             var documentId = DocumentId.CreateNewId(projectId, debugName: filePath);
 
+            var sourceCodeKind = GetSourceCodeKind();
             var documentInfo = DocumentInfo.Create(
                 documentId,
                 filePath,
-                sourceCodeKind: parseOptionsOpt?.Kind ?? SourceCodeKind.Regular,
+                sourceCodeKind: sourceCodeKind,
                 loader: new FileTextLoader(filePath, defaultEncoding: null),
                 filePath: filePath);
 
@@ -414,8 +419,19 @@ private ProjectInfo CreateProjectInfoForDocument(string filePath)
                 metadataReferences: _metadataReferences);
 
             // Miscellaneous files projects are never fully loaded since, by definition, it won't know
-            // what the full set of information is.
-            return projectInfo.WithHasAllInformation(hasAllInformation: false);
+            // what the full set of information is except when the file is script code.
+            return projectInfo.WithHasAllInformation(hasAllInformation: sourceCodeKind == SourceCodeKind.Script);
+
+            SourceCodeKind GetSourceCodeKind()
+            {
+                if (parseOptionsOpt != null)
+                {
+                    return parseOptionsOpt.Kind;
+                }
+
+                return string.Equals(fileExtension, languageInformation.ScriptExtension, StringComparison.OrdinalIgnoreCase) ?
+                    SourceCodeKind.Script : SourceCodeKind.Regular;
+            }
         }
 
         private void DetachFromDocument(uint docCookie, string moniker)

src/Workspaces/Core/Portable/Workspace/Solution/DocumentState_SimpleProperties.cs

@@ -14,7 +14,7 @@ public SourceCodeKind SourceCodeKind
         {
             get
             {
-                return this.ParseOptions == null ? SourceCodeKind.Regular : this.ParseOptions.Kind;
+                return this.ParseOptions == null ? this.Attributes.SourceCodeKind : this.ParseOptions.Kind;
             }
         }