fix circularity issue when inferring from overrides

[sigmundch]

When implementing inference on overriden methods and fields, I encountered a bug that only affects types with generics that are part of a library cycle.

The source of the problem is likely related to where in the pipeline we are running our inference. In particular, we do it right after the super classes have been resolved, and before our members are, however I'm not sure yet on why this is happening.

Here is an example flaky test that illustrates the problem. This test passes often, but sometimes fail with a null pointer exception:

 testChecker({
      '/a.dart': '''
          import 'main.dart';
        abstract class I<E> {
          A<E> m(a, String f(v, T e));
        }
      ''',
      '/main.dart': '''
          import 'a.dart';

        abstract class A<E> implements I<E> {
          const A();

          E value;
        }

        abstract class M {
          int y;
        }

        class B<E> extends A<E> implements M {
          const B();
          int get y => 0;

          m(a, f(v, T e)) {}
        }

        foo () {
          int y = /*severe:StaticTypeError*/new B<String>().m(null, null).value;
          String z = new B<String>().m(null, null).value;
        }
    '''
    }, inferFromOverrides: true);

When it fails, this is the exception we see:

Error while looking up m in I<E>:
 The null object does not have a method 'substitute2'.

NoSuchMethodError: method not found: 'substitute2'
Receiver: null
Arguments: [_List len:1, _List len:1]
#0      Object._noSuchMethod (dart:core-patch/object_patch.dart:42)
#1      Object.noSuchMethod (dart:core-patch/object_patch.dart:45)
#2      MethodMember.from (package:ddc_analyzer/src/generated/element.dart:8225:29)
#3      InterfaceTypeImpl.getMethod (package:ddc_analyzer/src/generated/element.dart:6418:24)
#4      _memberTypeGetter.f (package:ddc/src/utils.dart:150:34)
#5      searchTypeFor.search (package:ddc/src/utils.dart:105:32)
#6      searchTypeFor.search (package:ddc/src/utils.dart:118:19)
#7      searchTypeFor.search (package:ddc/src/utils.dart:114:17)
#8      searchTypeFor (package:ddc/src/utils.dart:125:16)
#9      RestrictedTypeResolverVisitor.visitMethodDeclaration (package:ddc/src/checker/resolver.dart:229:31)
#10     MethodDeclaration.accept (package:ddc_analyzer/src/generated/ast.dart:12944:63)
#11     TypeResolverVisitor.visitClassMembersInScope (package:ddc_analyzer/src/generated/resolver.dart:13952:26)
#12     ScopedVisitor.visitClassDeclaration (package:ddc_analyzer/src/generated/resolver.dart:12308:35)
#13     TypeResolverVisitor.visitClassDeclaration (package:ddc_analyzer/src/generated/resolver.dart:13900:32)
#14     ClassDeclaration.accept (package:ddc_analyzer/src/generated/ast.dart:4555:62)
#15     NodeList.accept (package:ddc_analyzer/src/generated/ast.dart:13507:26)
#16     CompilationUnit.visitChildren (package:ddc_analyzer/src/generated/ast.dart:5261:27)
#17     UnifyingAstVisitor.visitNode (package:ddc_analyzer/src/generated/ast.dart:20715:23)
#18     UnifyingAstVisitor.visitCompilationUnit (package:ddc_analyzer/src/generated/ast.dart:20555:60)
#19     CompilationUnit.accept (package:ddc_analyzer/src/generated/ast.dart:5254:61)
#20     LibraryResolver._buildTypeHierarchies (package:ddc_analyzer/src/generated/resolver.dart:8314:40)
#21     LibraryResolver.resolveLibrary (package:ddc_analyzer/src/generated/resolver.dart:7955:26)
#22     ResolveDartLibraryTask.internalPerform (package:ddc_analyzer/src/generated/engine.dart:11138:29)
#23     AnalysisTask._safelyPerform (package:ddc_analyzer/src/generated/engine.dart:6814:22)
#24     AnalysisTask.perform (package:ddc_analyzer/src/generated/engine.dart:6793:21)
#25     AnalysisContextImpl._cacheDartResolutionData (package:ddc_analyzer/src/generated/engine.dart:2901:33)
#26     AnalysisContextImpl._getDartResolutionData (package:ddc_analyzer/src/generated/engine.dart:3676:33)
#27     AnalysisContextImpl._getDartResolutionData2 (package:ddc_analyzer/src/generated/engine.dart:3708:36)
#28     AnalysisContextImpl.resolveCompilationUnit2 (package:ddc_analyzer/src/generated/engine.dart:2566:30)
#29     compile (package:ddc/devc.dart:69:61)
#30     testChecker (package:ddc/src/testing.dart:66:24)

[sigmundch]

The code for context is currently at:
https://chromereviews.googleplex.com/145247013/

[sigmundch]

Here are the references in the code that are relevant to this bug:

https://github.com/dart-lang/dart-dev-compiler/blob/9a63f5b69a587aa418495c83cfb762685a8443c2/lib/src/utils.dart#L153

https://github.com/dart-lang/dart-dev-compiler/blob/9a63f5b69a587aa418495c83cfb762685a8443c2/test/checker/inferred_type_test.dart#L391

[jmesserly]

fixed a while ago, I presume by Super Siggi :)

[sigmundch]

haha :)

Yeah the fix went in at 92e1373. According to this comment I probably intended to close this issue at the time :)