[
https://issues.apache.org/jira/browse/GROOVY-12716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18139949#comment-18139949
]
ASF GitHub Bot commented on GROOVY-12716:
-----------------------------------------
codeconsole opened a new pull request, #3250:
URL: https://github.com/apache/groovy/pull/3250
A method pointer assigned to or returned as a functional interface has its
return type checked since GROOVY-12623, against the common type of every
overload of the name. So an overloaded method that works on 6.0.0 no longer
compiles on master:
```groovy
@groovy.transform.CompileStatic
class C {
Function<Integer,Integer> f() { Math.&abs } // Possible
loss of precision from double to java.lang.Integer
BiFunction<Integer,Integer,Integer> g() { Math.&max } // same
}
```
An `Integer` argument selects `abs(int)` and `max(int,int)` at run time, so
`abs(double)` should not count.
The check now uses the methods that values of the functional interface's
parameter types can select: the best match for those types, and any method with
narrower parameter types, which a value of a subtype selects.
`ToIntFunction<Object> g = C.&f` with `int f(Object)` and `long f(Long)` is
still reported, as `f(Long)` may be called, and so is `ToIntFunction<Number> h
= Math.&abs`. All the candidates still count when the parameter types select
none of them, or when an instance method referenced through its class takes the
first parameter as its receiver. A method reference (`::`) is not affected.
#3134 (GROOVY-12607) includes this commit, as it depends on it.
## Tests
`MethodReferenceTest.testMethodPointerToOverloadsSelectedByParameterTypes`
fails without the change, on its assignments and return of `Math.&abs` and
`Math.&max`. It also runs them and covers the overloads that must still be
reported. `groovy.transform.stc.*` and `org.codehaus.groovy.classgen.asm.sc.*`
pass. The Checkstyle and CodeNarc gates pass.
> STC: an overloaded method pointer assigned to a functional interface is
> checked against overloads its parameter types cannot select
> -----------------------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12716
> URL: https://issues.apache.org/jira/browse/GROOVY-12716
> Project: Groovy
> Issue Type: Bug
> Components: Static Type Checker
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> {code:groovy}
> import java.util.function.*
> @groovy.transform.CompileStatic
> class C {
> Function<Integer,Integer> f() { Math.&abs }
> BiFunction<Integer,Integer,Integer> g() { Math.&max }
> void h() { Function<Integer,Integer> i = Math.&abs; assert i.apply(-1) ==
> 1 }
> }
> {code}
> *Actual:* {{Possible loss of precision from double to java.lang.Integer}} for
> each method pointer.
> *Expected:* it compiles and runs, as on 6.0.0. An {{Integer}} argument
> selects {{abs(int)}} and {{max(int,int)}} at run time.
> The check for the return value of a method pointer takes the common type of
> all the overloads of the name, here {{double}}, including those that values
> of the functional interface's parameter types never select. Since
> GROOVY-12623 (commit d1710f88eb) a method pointer gets its target type when
> it is assigned or returned, so such a pointer now reaches this check.
> The overloads that count are the best match for the parameter types, and any
> with narrower parameter types, which a value of a subtype selects. So
> {{ToIntFunction<Object> g = C.&f}} with {{int f(Object)}} and {{long
> f(Long)}} is still reported, as {{f(Long)}} may be called.
> Master only: 6.0.0 compiles and runs the example.
--
This message was sent by Atlassian Jira
(v10.3.26#10030026)
