Eric Milles created GROOVY-10074:
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Summary: DGM: Fix transform generics for collect and similar
Key: GROOVY-10074
URL: https://issues.apache.org/jira/browse/GROOVY-10074
Project: Groovy
Issue Type: Bug
Components: groovy-jdk
Reporter: Eric Milles
The {{collect}} DGM is defined like this for {{Iterable}}, arrays, etc.:
{code:java}
<T> List<T> collect(Object self, Closure<T> transform)
<S,T> List<T> collect(S[] self, @ClosureParams(FirstParam.Component.class)
Closure<T> transform)
<S,T> List<T> collect(Iterable<S> self,
@ClosureParams(FirstParam.FirstGenericType.class) Closure<T> transform)
<S,T> List<T> collect(Iterator<S> self,
@ClosureParams(FirstParam.FirstGenericType.class) Closure<T> transform)
{code}
and like this for the variants that accept an output collection:
{code:java}
<T> Collection<T> collect(Object self, Collection<T> collector, Closure<?
extends T> transform)
...
{code}
I think {{Closure<? extends T>}} is better. It would allow plain {{collect}}
to work for this example under STC without requiring {{? extends CharSequence}}
on the target or a typecast for "it" or the call expression:
{code:groovy}
List<CharSequence> list = ['string'].collect { it }
{code}
For comparison, Java's {{Stream#map}} function is defined this way:
{code:java}
<R> Stream<R> map(Function<? super T, ? extends R> mapper)
{code}
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