Disallow implicit casts

Explicit casts make it easier to confidently navigate the code base and
apply refactorings which tighten types. This change exposes a number of
places where types can be tightened, but only the most trivial were
applied. For most places I added the explicit cast that would have
happened anyway and so behavior shouldn't be changing.

- Add the configuration which disallows implicit casts in the analyzer.
- Add explicit casts in almost all instances.
- Where the implicit cast was due to a local variable type on the left,
  change it to a `var` so the type is not repeated.
- In a few places add argument types where they were already applied on
  the parent type, and the subclass was unnecessarily loosening argument
  types to dynamic.
- In a few places where a method was defined with an implicit dynamic
  return but had an obvious and consistent return type, annotate the
  method instead of casting after calls to that method.

Change-Id: I90e11b1cc08ce69967ea5705b507d5758a8f668f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/103381
Reviewed-by: Nicholas Shahan <nshahan@google.com>
17 files changed
tree: df0440563246f7bd21eab40acefd9b4902134580
  1. .clang-format
  2. .gitattributes
  3. .gitconfig
  4. .github/
  5. .gitignore
  6. .gn
  7. .mailmap
  8. .packages
  9. .vpython
  11. BUILD.gn
  12. CHANGELOG.md
  14. DEPS
  17. PRESUBMIT.py
  18. README.dart-sdk
  19. README.md
  21. build/
  22. client/
  23. codereview.settings
  24. docs/
  25. pkg/
  26. runtime/
  27. samples-dev/
  28. samples/
  29. sdk/
  30. tests/
  31. third_party/
  32. tools/
  33. utils/


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