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.
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