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https://issues.apache.org/jira/browse/GROOVY-12678?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18137474#comment-18137474
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ASF GitHub Bot commented on GROOVY-12678:
-----------------------------------------
codeconsole opened a new pull request, #3199:
URL: https://github.com/apache/groovy/pull/3199
Under `@CompileStatic`, `owner` and `delegate` (and `getOwner()` and
`getDelegate()`) inside a lambda nested in a closure or another lambda were
typed as `Closure`:
```groovy
@CompileStatic
class C {
String name = 'n'
def q() {
Supplier<Supplier<Object>> s = () -> { name; (Supplier<Object>) (()
-> { name; owner.maximumNumberOfParameters }) }
s.get().get() // GroovyCastException: Cannot cast object 'C@…' with
class 'C' to class 'groovy.lang.Closure'
}
def t() {
def c = { -> Supplier<String> s = () -> { name; owner.name };
s.get() }
c() // No such property: name for class: groovy.lang.Closure
}
}
```
Seen in 4.0.33, 5.0.8 and 6.0.0 too.
A native lambda is constructed with the enclosing `this` as its owner
(`ClosureWriter.loadThis` reads `getThisObject()` inside a generated function),
so its owner is the enclosing instance at any depth. The type checker
(`StaticTypeCheckingVisitor.hasClosureOwner`) now types `owner` and `delegate`
in such a lambda as the enclosing class, as it already did for a top-level
lambda. A lambda counts as native when it is statically compiled and its target
type is a functional interface, the same rule
`StaticTypesLambdaWriter.writeLambda` uses. Closures and lambdas compiled as
closures (type-checked code, or no functional-interface target) still get
`Closure`, since their owner is the enclosing closure or lambda.
With #3193 (GROOVY-12672) also merged, a nested lambda that reads `owner`
but no instance member works at run time too (without it, such a lambda gets a
static `doCall`). The two merge cleanly, and cleanly with #3189 (GROOVY-12668).
## Tests
`LambdaTest.testNestedLambdaOwnerDelegateThisObject` and
`ClosuresStaticCompileTest.testNestedLambdaDelegateOwner` fail without the
change. `LambdaTest.testClosureOwnerInNestedFunction` and
`ClosuresSTCTest.testNestedLambdaDelegateOwner` check that closures, lambdas
compiled as closures and type-checked lambdas keep the `Closure` owner.
`groovy.transform.stc.*` and `org.codehaus.groovy.classgen.asm.sc.*` pass. The
Checkstyle and CodeNarc gates pass.
> STC types owner and delegate as Closure inside a lambda nested in a closure
> or lambda, so SC throws GroovyCastException
> -----------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12678
> URL: https://issues.apache.org/jira/browse/GROOVY-12678
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 4.0.33, 5.0.8, 7.0.0-alpha-1, 6.0.0
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> {code:groovy}
> import java.util.function.Supplier
> @groovy.transform.CompileStatic
> class C {
> String name = 'n'
> def q() {
> Supplier<Supplier<Object>> s = () -> { name; (Supplier<Object>) (()
> -> { name; owner.maximumNumberOfParameters }) }
> s.get().get()
> }
> def r() {
> def c = { -> Supplier<Object> s = () -> { name;
> owner.maximumNumberOfParameters }; s.get() }
> c()
> }
> def t() {
> def c = { -> Supplier<String> s = () -> { name; owner.name }; s.get()
> }
> c()
> }
> }
> new C().q()
> {code}
> *Actual:* {{q()}} and {{r()}} throw {{GroovyCastException: Cannot cast object
> 'C@...' with class 'C' to class 'groovy.lang.Closure'}}, and {{t()}} fails to
> compile with "No such property: name for class: groovy.lang.Closure".
> {{delegate}}, {{getOwner()}} and {{getDelegate()}} behave the same.
> *Expected:* the owner of a statically compiled native lambda is the enclosing
> instance at any depth of nesting, as it is for a top-level lambda. So
> {{owner}} and {{delegate}} should be typed as {{C}}: {{t()}} returns 'n', and
> {{owner.maximumNumberOfParameters}} is rejected at compile time, as it is in
> a top-level lambda.
> Cause: {{StaticTypeCheckingVisitor}} types {{owner}} and {{getOwner()}}, and
> {{delegate}} without delegation metadata, as {{Closure}} whenever more than
> one closure or lambda encloses the reference. A native lambda's owner is the
> enclosing {{this}}, not the enclosing function. A closure, or a lambda
> compiled as a closure (type-checked code, or no functional-interface target),
> is still owned by the enclosing function.
> Verified on 4.0.33 (owner reference in a lambda inside a closure), 5.0.8,
> 6.0.0 and master.
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