codeconsole opened a new pull request, #3112:
URL: https://github.com/apache/groovy/pull/3112
Inside a trait method, reading a static trait property through an explicit
`this` fails static type checking, while the unqualified reference and dynamic
Groovy work:
```groovy
@groovy.transform.CompileStatic
trait T {
static boolean flag = true
static boolean sm() { this.flag }
boolean im() { this.flag }
}
class C implements T {}
assert C.sm() && new C().im()
```
```
[Static type checking] - Cannot find matching method
java.lang.Class#T__flag$get() or static method T#T__flag$get().
[Static type checking] - Cannot find matching method
T$Trait$FieldHelper#T__flag$get().
```
`TraitReceiverTransformer` rewrote `this.<field>` with a placeholder
`FieldNode` that is always non-static, so the accessor was called on the field
helper (instance method; static accessors are on the static field helper) or on
the `Class` receiver (static method), without the `DO_DYNAMIC` marker that
static trait fields get. It now uses the trait's declared field, as the
unqualified reference does: a static property is accessed through the
implementing class, and the read is typed by the field's declared type. This
also covers compound assignments such as `this.count += 1`, and `this.x` inside
closures and lambdas.
## Tests
`TraitASTTransformationTest.testTraitStaticPropertyThroughThis` fails
without the change under `@TypeChecked` and `@CompileStatic`; it covers reads
and writes from static and instance methods, compound assignments, a
non-boolean property, per-implementer copies, and closure and lambda access.
The `org.codehaus.groovy.transform.traitx`, `groovy.transform.stc`,
`org.codehaus.groovy.classgen.asm.sc` and `gls` packages and
`groovy.ThisAndSuperTest` pass. The Checkstyle and CodeNarc gates pass.
Seen in 4.0.33, 5.0.8 and 6.0.0.
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