Drop the `StringTypes` test helper and use the existing type parsing
helpers directly in type-system tests.
This makes the tests construct the types they assert on through the same
`parseType`, `parseFunctionType`, and `parseRecordType` paths used
elsewhere in the suite. It also removes manual instantiation of common
interface types where a parsed type string is clearer.
Update failure messages and string comparisons to rely on the type
implementation's string form instead of maintaining a separate display
string helper. This keeps diagnostics local to each assertion while
removing the custom type-parameter collection logic that was only needed
by `StringTypes`.
Change-Id: I4720a7ad0d4b2b94eb4b6766d671086fcebdaef5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/498481
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Konstantin Shcheglov
5b5960aac7