[
https://issues.apache.org/jira/browse/GROOVY-12607?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Scott Murphy Heiberg updated GROOVY-12607:
------------------------------------------
Description:
{code:groovy}
import java.util.function.Supplier
@groovy.transform.CompileStatic
class C {
int intMethod() { 1 }
Supplier<String> f() { this.&intMethod }
String take(Supplier<String> s) { s.get() }
def g() { take(this::intMethod) }
def h() { Supplier<String> s = this::intMethod; s.get().toUpperCase() }
}
new C().h()
{code}
Actual: the class compiles. At run time the supplier returns an Integer, so the
script fails with {{ClassCastException: class java.lang.Integer cannot be cast
to class java.lang.String}} (under @TypeChecked: MissingMethodException for
toUpperCase on Integer). The same happens for a Boolean supplier from a
String-returning method and a Long supplier from an int-returning method, with
.& or ::, returned, passed or assigned. A method pointer (.&) that is returned
or assigned is not checked at all, so even a method returning an Integer
supplier as this.&stringMethod compiles.
Expected: a compile error such as "Invalid return type: int is not convertible
to java.lang.String", as for the equivalent lambda.
Cause: the return-type check for method pointers and references uses assignment
compatibility, which allows conversions (to String, Boolean, wider number
wrappers) that a method pointer or reference never performs. A method pointer
gets no target type when it is returned or assigned.
Seen in 4.0.33, 5.0.8 and 6.0.0.
PR: https://github.com/apache/groovy/pull/3134
was:
{code:groovy}
import java.util.function.Supplier
@groovy.transform.CompileStatic
class C {
int intMethod() { 1 }
Supplier<String> f() { this.&intMethod }
String take(Supplier<String> s) { s.get() }
def g() { take(this::intMethod) }
def h() { Supplier<String> s = this::intMethod; s.get().toUpperCase() }
}
new C().h()
{code}
Actual: the class compiles. At run time the supplier returns an Integer, so the
script fails with {{ClassCastException: class java.lang.Integer cannot be cast
to class java.lang.String}} (under @TypeChecked: MissingMethodException for
toUpperCase on Integer). The same happens for a Boolean supplier from a
String-returning method and a Long supplier from an int-returning method, with
.& or ::, returned, passed or assigned. A method pointer (.&) that is returned
or assigned is not checked at all, so even a method returning an Integer
supplier as this.&stringMethod compiles.
Expected: a compile error such as "Invalid return type: int is not convertible
to java.lang.String", as for the equivalent lambda.
Cause: the return-type check for method pointers and references uses assignment
compatibility, which allows conversions (to String, Boolean, wider number
wrappers) that a method pointer or reference never performs. A method pointer
gets no target type when it is returned or assigned.
Seen in 4.0.33, 5.0.8 and 6.0.0.
> STC accepts a method pointer or method reference whose method return type
> does not fit the target functional interface
> ----------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12607
> URL: https://issues.apache.org/jira/browse/GROOVY-12607
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.33, 5.0.8, 6.0.0
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> {code:groovy}
> import java.util.function.Supplier
> @groovy.transform.CompileStatic
> class C {
> int intMethod() { 1 }
> Supplier<String> f() { this.&intMethod }
> String take(Supplier<String> s) { s.get() }
> def g() { take(this::intMethod) }
> def h() { Supplier<String> s = this::intMethod; s.get().toUpperCase() }
> }
> new C().h()
> {code}
> Actual: the class compiles. At run time the supplier returns an Integer, so
> the script fails with {{ClassCastException: class java.lang.Integer cannot be
> cast to class java.lang.String}} (under @TypeChecked: MissingMethodException
> for toUpperCase on Integer). The same happens for a Boolean supplier from a
> String-returning method and a Long supplier from an int-returning method,
> with .& or ::, returned, passed or assigned. A method pointer (.&) that is
> returned or assigned is not checked at all, so even a method returning an
> Integer supplier as this.&stringMethod compiles.
> Expected: a compile error such as "Invalid return type: int is not
> convertible to java.lang.String", as for the equivalent lambda.
> Cause: the return-type check for method pointers and references uses
> assignment compatibility, which allows conversions (to String, Boolean, wider
> number wrappers) that a method pointer or reference never performs. A method
> pointer gets no target type when it is returned or assigned.
> Seen in 4.0.33, 5.0.8 and 6.0.0.
> PR: https://github.com/apache/groovy/pull/3134
--
This message was sent by Atlassian Jira
(v10.3.26#10030026)
