Replace the local marker-based _AstTest helper in ast_test.dart with
ParserDiagnosticsTest parsing and the shared findNode utilities. This
keeps the tests aligned with the inline diagnostics style used by other
parser tests, and avoids a second way to locate AST nodes from marked
source snippets.
Update the affected tests to parse normal source text, then locate the
expected node through findNode single-node accessors. Add a
singleConstructorName accessor so constructor-name tests can use the
same shared lookup path.
Change-Id: Ib8c7c2e7c2c1b320c95810ce148b5a27e68dda43
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/508421
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Konstantin Shcheglov
164cfda948