Don't use XyzElementImpl and XyzElementImpl2 from the analyzer

[scheglov]

This does not let us rename these classes in the analyzer.

[srawlins]

Here is the list of code locations where such elements are used:

git grep -n 'ElementImpl' lib
lib/src/model/canonicalization.dart:94:      if (ancestor is! ElementImpl2) {
lib/src/model/canonicalization.dart:98:          throw Exception('${ancestor.runtimeType} is not an ElementImpl2');
lib/src/model/constructor.dart:33:        (element.firstFragment as ConstructorElementImpl).typeNameOffset;
lib/src/model/extension.dart:57:        element: otherType.element3 as InterfaceElementImpl2,

[srawlins]

If you have the new names of these (ElementImpl2, ConstructoElementImpl, InterfaceElementImpl2), we can push a branch that uses those names, and then you can sync that branch into the Dart SDK in the same CL as the renames.

[scheglov]

Is there a reason to use implementation classes at all?

[srawlins]

I'm not sure. Maybe not.

[srawlins]

How does one instantiate an interface to bounds? TypeSystem provides instantiateInterfaceToBounds, but that is forbidden, as it accepts an InterfaceElement. TypeSystemImpl, a forbidden class, offers instantiateToBounds2, which requires a forbidden parameter type, InterfaceElementImpl2.

[scheglov]

Analyzer 7.4.4 has TypeSystem.instantiateInterfaceToBounds2.

  /// Instantiate the given [element] with default type arguments.
  @experimental
  InterfaceType instantiateInterfaceToBounds2({
    required InterfaceElement2 element,
    required NullabilitySuffix nullabilitySuffix,
  });

Ignore @experimental.

[srawlins]

I believe this is fixed with #4040, #4041, and #4042.

[scheglov]

Thank you! :-)