MirrorsUsed class Null safety

Annotation describing how "dart:mirrors" is used (EXPERIMENTAL).

When used as metadata on an import of "dart:mirrors" in library L, this class describes how "dart:mirrors" is used by library L unless overridden. See override.

The following text is non-normative:

In some scenarios, for example, when minifying Dart code, or when generating JavaScript code from a Dart program, the size and performance of the output can suffer from use of reflection. In those cases, telling the compiler what is used, can have a significant impact.

Example usage:

@MirrorsUsed(symbols: 'foo')
import 'dart:mirrors';

class Foo {
  noSuchMethod(Invocation invocation) {
    print(MirrorSystem.getName(invocation.memberName));
  }
}

main() {
  new Foo().foo(); // Prints "foo".
  new Foo().bar(); // Might print an arbitrary (mangled) name, "bar".
}

For a detailed description of the parameters to the MirrorsUsed constructor see the comments for symbols, targets, metaTargets and override.

An import of dart:mirrors may have multiple MirrorsUsed annotations. This is particularly helpful to specify overrides for specific libraries. For example:

@MirrorsUsed(targets: 'foo.Bar', override: 'foo')
@MirrorsUsed(targets: 'Bar')
import 'dart:mirrors';

will ensure that the target Bar from the current library and from library foo is available for reflection. See also override.