guice-assistedinject does not inject classes with default-constructors

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FactoryProvider.paramCanBeInjected(Parameter, Injector) is not
sophisticated enough, returning false for a whole spectrum of classes that
Guice *can* inject properly.

For example, if a class is not bound using Binder but it contains a default
constructor this method returns false even though Guice knows how to inject
it. If a class constructor contains a non-default constructor whose
parameters are all injectable it is also okay but this method returns false
again.

Original issue reported on code.google.com by gili.tza...@gmail.com on 24 Jul 2008 at 7:24

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Yup, these are known limitations of AssistedInject. AssistedInject for Guice 
1.0 is a fairly naive extension, and 
unfortunately Guice 1.0 doesn't have hooks for it to do much better 
(assistedinject only uses Guices' public API).

There are workarounds - always use explicit bind statements for 
assistedinject's dependencies.

Original comment by limpbizkit on 24 Jul 2008 at 7:41

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Original comment by limpbizkit on 24 Jul 2008 at 7:41

• Changed state: WontFix

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Are you saying this limitation only applies to guice-1.0? Is this limitation 
fixed in
guice-trunk?

Unfortunately, using explicit bind statements gets out of hand very quickly. 
It's
easy for default constructors but if you need to explicitly bind Providers and
instances you run into problems there are any cyclic dependencies or very deep
dependency graphs that Guice handles on your behalf very nicely.

Seeing how the guice-1.0 implementation is naive, can we not simply remove this 
check
and let it break later on if the type is not injectable? Wouldn't this yield the
desired flexibility at a cost of harder-to-read error messages?

Original comment by gili.tza...@gmail.com on 24 Jul 2008 at 7:53

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I just tried hard-coding paramCanBeInjected() to return true and it seems to 
work
just fine. If injection is allowed it proceeds properly, if not Guice gives its
standard error about not knowing how to construct X.

Is this a possible solution?

Original comment by gili.tza...@gmail.com on 24 Jul 2008 at 8:06