Converts the code that reports diagnostic codes `invalidAssignment`
and `argumentTypeNotAssignable` to use the literate diagnostic
reporting API.
This was challenging because some of the code for reporting these
diagnostics (specifically the method
`ErrorDetectionHelpers.checkForAssignableExpressionAtType`) was
parameterized by diagnostic code, but the two diagnostics accepted a
different number of parameters. To get the type safety of the literate
diagnostic API while preserving the existing behavior, I've created an
abstract base class, `NonAssignabilityReporter`, with a method
`createDiagnostic`, that encapsulates the differences in how to handle
the two diagnostic codes.
Change-Id: I6a6a69649e53f6980b5033771b14dbfdaa5895d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/467481
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Paul Berry
758d3a8803