Report an error when a part-of refers to an unnamed library.

pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart

Index: pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart b/pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart
index 9dbffe77c63e5bd20850d267b3e577a1571bea57..9a9eca481126406bc3fd214b34f587bae2f0f282 100644
--- a/pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart
@@ -484,6 +484,9 @@ class LibraryAnalyzer {
                     StaticWarningCode.PART_OF_DIFFERENT_LIBRARY,
                     partUri,
                     [libraryNameNode.name, name]);
+              } else if (libraryNameNode == null) {
+                libraryErrorReporter.reportErrorForNode(
+                    StaticWarningCode.PART_OF_UNNAMED_LIBRARY, partUri, [name]);

[Lasse Reichstein Nielsen, 2017/06/08 19:31:19]

Logic seems backwards.
Put the second branch first:
  if (libraryNameNode == null) { 
    ...
  } else if (libraryNameNode.name != name) {
    ...
  }

[floitsch, 2017/06/08 19:47:33]

Done.

               }
             } else {
               Source source = nameOrSource.source;