SAM conversion of inlined lambda expression

[maurizio cimadamore]

On 07/08/2010 15:57, Thomas Jung wrote:
> Hi Rémi,
>
> you're right. Defining
>
> public static<A,B,C>  Function<A,C>  simpleCompose(Function<B,C>  g,
> Function<A, B>  f){
>      return Functions.compose(g,f);
> }
> Function<String, String>  c = simpleCompose(#(x){ "a" + x }, #(x){ x + "b" });
>
> works. Is there is way to get some debugging information of the type inferencer?
>
> Thomas
>    
Hi
as Remi pointed out in an earlier email, there's a bug when the target 
method of a SAM conversion has a wildcard in return type position. 
Wildcards in argument types work w/o problems - a fix for this problem 
will be available soon.

Thanks
Maurizio
> On 7 August 2010 15:16, Rémi Forax<forax at univ-mlv.fr>  wrote:
>    
>>   Le 07/08/2010 09:58, Thomas Jung a écrit :
>>      
>>> Hi,
>>>
>>> I'm playing a bit with the prototype (i.e. I've not read the specs in
>>> full) and I'm puzzled after my second step.
>>>
>>> The initial code that uses Function
>>> (http://guava-libraries.googlecode.com/svn/trunk/javadoc/com/google/common/base/Function.html)
>>> is:
>>>
>>> Function<String, String>    a = #(x){ "a" + x };
>>> Function<String, String>    b = #(x){ x + "b" };
>>> assertEquals("axb", Functions.compose(a, b).apply("x"));
>>>
>>> This works with type inference and does the conversion to the type
>>> Function<F,T>. But if I inline the lambda expression it won't convert
>>> them.
>>>
>>> Function<String, String>    c = Functions.<String, String>
>>> compose(#(String x){ "a" + x }, #(String x){ x + "b" });
>>>
>>> I've added all type annotations to rule out that this is the problem.
>>> The error message is:
>>> "method compose in class Functions cannot be applied to given types".
>>> (Can I get more information here about the types/problem?)
>>>
>>> Is this not supported?
>>>
>>> Thomas
>>>
>>>        
>> This is a bug, the prototype have a problem to infer types
>> if there is a wilcard in the middle.
>>
>> by example, this doesn't compile:
>> Function<String, ? extends String>  b = #(x){ x + "b" };
>>
>> So you can't use compose which is declared:|*
>> *|<A,B,C>
>> <../../../../com/google/common/base/Functions.html#compose%28com.google.common.base.Function,%20com.google.common.base.Function%29>Function
>> <../../../../com/google/common/base/Function.html><A,C>  |compose
>> <../../../../com/google/common/base/Functions.html#compose%28com.google.common.base.Function,%20com.google.common.base.Function%29>(Function
>> <../../../../com/google/common/base/Function.html><B,C>  g, Function
>> <../../../../com/google/common/base/Function.html><A,*? extends* B>  f)|
>>
>> Rémi
>>
>>
>>
>>
>>      
>