Merge pull request #899 from dotnet/generator_version

eng/Versions.props

@@ -24,6 +24,8 @@
     <MicrosoftCodeAnalysisEditorFeaturesTextVersion>3.9.0</MicrosoftCodeAnalysisEditorFeaturesTextVersion>
     <MicrosoftCodeAnalysisVisualBasicVersion>3.9.0</MicrosoftCodeAnalysisVisualBasicVersion>
     <MicrosoftCodeAnalysisWorkspacesCommonVersion>3.9.0</MicrosoftCodeAnalysisWorkspacesCommonVersion>
+    <!-- We target a lower roslyn API to build internal generators against so they still load in earlier VS versions -->
+    <MicrosoftCodeAnalysisGeneratorVersion>3.9.0</MicrosoftCodeAnalysisGeneratorVersion>
     <!-- VS SDK -->
     <EnvDTE80Version>16.9.30921.233</EnvDTE80Version>
     <EnvDTE90Version>16.8.30705.32</EnvDTE90Version>

src/VisualStudio.Roslyn.SDK/AssemblyVersionGenerator/AssemblyVersionGenerator.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="$(MicrosoftCodeAnalysisCommonVersion)" />
+    <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="$(MicrosoftCodeAnalysisGeneratorVersion)" />
   </ItemGroup>
 
 </Project>