Merge pull request #4267 from amcasey/AnalyzerAssert

Loosen diagnostics assert

src/Features/Core/Diagnostics/EngineV1/DiagnosticIncrementalAnalyzer_GetLatestDiagnosticsForSpan.cs

@@ -163,7 +163,9 @@ private async Task<bool> TryGetSyntaxAndSemanticCompilerDiagnostics(StateSet sta
             [Conditional("DEBUG")]
             private void VerifyDiagnostics(SemanticModel model)
             {
-                Func<Diagnostic, bool> shouldInclude = d => _range.IntersectsWith(d.Location.SourceSpan);
+                // Exclude unused import diagnostics since they are never reported when a span is passed.
+                // (See CSharp/VisualBasicCompilation.GetDiagnosticsForMethodBodiesInTree.)
+                Func<Diagnostic, bool> shouldInclude = d => _range.IntersectsWith(d.Location.SourceSpan) && !IsUnusedImportDiagnostic(d);
 
                 // make sure what we got from range is same as what we got from whole diagnostics
                 var rangeDeclaractionDiagnostics = model.GetDeclarationDiagnostics(_range).ToArray();
@@ -192,6 +194,19 @@ private void VerifyDiagnostics(SemanticModel model)
                 }
             }
 
+            private static bool IsUnusedImportDiagnostic(Diagnostic d)
+            {
+                switch (d.Id)
+                {
+                    case "CS8019":
+                    case "BC50000":
+                    case "BC50001":
+                        return true;
+                    default:
+                        return false;
+                }
+            }
+
             private static TextSpan AdjustSpan(Document document, SyntaxNode root, TextSpan span)
             {
                 // this is to workaround a bug (https://github.com/dotnet/roslyn/issues/1557)