Bump analyzer to v5

[GZGavinZhao]

Previously we just add deprecated_member_use: ignore to the analysis_options.yaml file in the monorepo root. Now analyzer has gone to v5 so the usage of deprecated APIs must be dealt with now.

The hardest parts are the last three, since they change the class returned or require another variable, so likely we'll have to work around them.

• [x] Replace getType with getClass for LibraryCompilationUnitElement and LibraryElement.
• [ ] Replace name with getDisplayString for DartType. Note: need to think about whether nullability
• [x] Replace element with element2. Note that the return type changes from ClassElement to InterfaceElement, so it requires a bit more work. Most times we should be able to just cast it to ClassElement since ClassElement implements InterfaceElement.
• [x] Replace enclosingElement with enclosingElement3.
• [x] Somehow replace resolveToBound from DartType with TypeSystem's instance method resolveToBound.
• [ ] Replace parts (CompilationUnitElement) with parts2 (PartsElement) from LibraryElement.
• [ ] Replace import (ImportElement) with imports2 (LibraryInputElement) from LibraryElement.

[denniskaselow]

Replace element with element2. Note that the return type changes from ClassElement to InterfaceElement, so it requires a bit more work. Most times we should be able to just cast it to ClassElement since ClassElement implements InterfaceElement.

FYI in case you want to migrate to the current version of analyzer and plan to have no lints about deprecated members: with analyzer 5.2 element2 is deprecated and element is the new one (The old element is removed in 5.0).

[GZGavinZhao]

Yeah, so my process will be:

1. Migrate deprecated API's in analyzer v4
2. Upgrade analyzer to v5, ensure everything is still working
3. Migrate deprecated API's again
4. Then I'll probably have to repeat these steps for analyzer v6

As I might've said previously, unfortunately the analyzer is probably one of the most tiresome packages to keep up-to-date with.

[ykmnkmi]

Any progress? I'm now doing the same, fixing all static analysis warnings and upgrading to the new analyzer. PS: ngast and ngcompiler.

[GZGavinZhao]

Sorry, not really. It's the busiest time of the year for me and I've been having a bad cold/flu. I am blocked on the resolveToBound issue, particularly with the case when dartType is FunctionType (see where resolveToBound is defined).

[GZGavinZhao]

@ykmnkmi Also, I'm absolutely okay if you want to use the existing changes from my PR in yours. You don't need to let me know.

[GZGavinZhao]

Fixed by #37.