[
https://issues.apache.org/jira/browse/GROOVY-11683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17956660#comment-17956660
]
Eric Milles commented on GROOVY-11683:
--------------------------------------
Do these intermediate types look correct?
{code:groovy}
def /*Stream<ListUsersResponse>*/ aaa = cognito.listUsersPaginator {
it.userPoolId(cognitoUserPool) }.stream()
def /*Stream<List<UserType>>*/ bbb = aaa.map(ListUsersResponse::users)
def /*Stream<UserType>*/ ccc = bbb.flatMap(List::stream)
def /*Stream<String>*/ ddd = ccc.map(UserType::username)
def /*List<String>*/ eee = ddd.toList()
{code}
This (example) does work properly in Groovy 5:
{code:groovy}
class Scratch {
@CompileStatic groovy11683(Scratch scratch) {
def aaa = Stream.of(scratch)
def bbb = aaa.map(Scratch::strings)
def ccc = bbb.flatMap(List::stream)
def ddd = ccc.map(Integer::valueOf)
}
List<String> strings() {
[ 'a', 'b', 'c' ]
}
}
{code}
I'm not sure about a Groovy 4 backport. The order of visit for method args and
method call is different for pointers/references.
> STC loses generic information on method reference
> -------------------------------------------------
>
> Key: GROOVY-11683
> URL: https://issues.apache.org/jira/browse/GROOVY-11683
> Project: Groovy
> Issue Type: Bug
> Components: Static Type Checker
> Affects Versions: 4.0.27
> Reporter: Christopher Smith
> Assignee: Eric Milles
> Priority: Minor
>
> I am using a typical stream pipeline to get a list of pages of results and
> flatMap them to the individual records:
> {code}
> //
> software.amazon.awssdk.services.cognitoidentityprovider.CognitoIdentityProviderClient
> cognito
> cognito.listUsersPaginator { it.userPoolId(cognitoUserPool) }
> .stream()
> .map(ListUsersResponse::users)
> .flatMap(List::stream) // produces UserType
> .map(UserType::username)
> .toList()
> {code}
> Both groovyc and GRECLIPSE report the compile-time error
> {code}
> Failed to find class method 'username(java.lang.Object)' or instance method
> 'username()' for the type:
> software.amazon.awssdk.services.cognitoidentityprovider.model.UserType
> {code}
> The cause appears to be a failure to propagate the type information out of
> the {{flatMap}} call: On hover, Eclipse correctly identifies the
> {{List::stream}} as returning {{Stream<UserType>}}, but the {{flatMap}} is
> reported as {{Stream<Object>}}. Inserting a type witness before the
> {{flatMap}} call resolves the error. Both the loss of type information and
> the incorrect error message appear to be bugs.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
