dart analyze <file> says the file is fine, dart <file> fails with compile-time error

[osa1]

Tried with the current HEAD (3669086).

Repro:

1. git clone https://github.com/osa1/protobuf.dart -b analyzer_bug
2. cd protobuf.dart/protobuf
3. dart pub get
4. dart analyze test/coded_buffer_reader_test.dart
5. dart test/coded_buffer_reader_test.dart

Step 4 says "No issues found!", but step 5 fails with compile-time error:

lib/src/protobuf/pb_list.dart:218:31: Error: The method 'deepCopy' isn't defined for the class 'GeneratedMessage'.
 - 'GeneratedMessage' is from 'package:protobuf/protobuf.dart' ('lib/protobuf.dart').
Try correcting the name to the name of an existing method, or defining a method named 'deepCopy'.
        wrappedList.add(value.deepCopy(freeze: freeze) as dynamic);
                              ^^^^^^^^
lib/src/protobuf/pb_map.dart:138:33: Error: The method 'deepCopy' isn't defined for the class 'GeneratedMessage'.
 - 'GeneratedMessage' is from 'package:protobuf/protobuf.dart' ('lib/protobuf.dart').
Try correcting the name to the name of an existing method, or defining a method named 'deepCopy'.
        wrappedMap[key] = value.deepCopy(freeze: freeze) as dynamic;
                                ^^^^^^^^

[osa1]

We discussed this at the office and @eernstg explained that the CFE error is valid. My understanding of the problem is:

• We have value : E
• We promote it with value is GeneratedMessage
• The resulting type is an intersection type of E and GeneratedMessage
• Intersection types are not reified
• Because the type is not reified, the extension bound T extends GeneratedMessage does not hold for this type
• So we can't call the extension methods

So the error is valid, and analyzer should've caught it.

[srawlins]

Still reproducible today. But there is a duplicate issue that is more active. Tracking as #53711.