Add Invocation constructors

[DartBot]

This issue was originally filed by @seaneagan

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From the mailing list:

https://groups.google.com/a/dartlang.org/d/msg/misc/yc57k6TflOQ/UYOeNH-kRU0J

I have a use case for constructing Invocations, but Invocation currently has no constructors.

I could potentially do:

class InvocationMaker {
  noSuchMethod(Invocation invocation) => invocation;
}

var invocation = new InvocationMaker().a(b, c: d);

But that is clearly a hack, and noSuchMethod won't get called for things like == and hashCode that are in Object.

I could also implement Invocation on my own, but will that work when I pass it to InstanceMirror#delegate?

The Invocation constructors could be something like:

  Invocation.getter(Symbol fieldName);
  Invocation.setter(Symbol fieldName, value);
  Invocation.method(
      Symbol methodName,
      {List positionalArguments,
       Map<Symbol, dynamic> namedArguments});

[gbracha]

This is by design. Analyzing the use of noSuchMethod and mirrors is problematic enough without random instances of Invocation being created.

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Set owner to @gbracha.
Added Area-Language, AsDesigned labels.

[DartBot]

This comment was originally written by @seaneagan

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Why do Invocations merely existing affect mirror and noSuchMethod usage analysis? They are just plain data objects, right? It seems like Invocations are harmless, until they are actually consumed by InstanceMirror#delegate or some other dynamic invocation API.

[DartBot]

This comment was originally written by @seaneagan

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Some use cases:

* issue #14725

• to create a Converter between Invocations and command line arguments (as passed to main) to implement issue args: define args using dart method signature #12272