Peter Schmitz created GROOVY-11341:
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Summary: @CompileStatic: Compilation fails due to synthetic bridge
methods (probably)
Key: GROOVY-11341
URL: https://issues.apache.org/jira/browse/GROOVY-11341
Project: Groovy
Issue Type: Bug
Components: Static compilation, Static Type Checker
Affects Versions: 4.0.20, 5.0.0-alpha-7, 3.0.21, 2.4.x, 2.5.x
Reporter: Peter Schmitz
Given the following Java classes:
{code:java}
public interface InterfaceBase {
Object getValue();
}
public class MyImplBase {
public Long getValue() {
return 42L;
}
}
public class MyImpl extends MyImplBase implements InterfaceBase {
} {code}
And the following SimpleCaller.groovy:
{code:java}
@groovy.transform.CompileStatic
class SimpleCaller {
public static void main(String[] args) {
Long v = new MyImpl().getValue();
System.out.println(v); //42
}
} {code}
The compilation fails with:
{{SimpleCaller.groovy: 7: [Static type checking] - Cannot assign value of type
java.lang.Object to variable of type java.lang.Long}}
{{ @ line 7, column 16.}}
{{ Long v = new MyImpl().getValue();}}
{{ ^}}
Compiling the equivalent {{SimpleCaller.java}} with _javac_ completes
successfully.
This structure is a bit uncommon, because MyImplBase uses a covariant return
type and doesn't implement the interface directly, only its subclass does.
I believe the problem is connected to the synthetic bridge method inserted into
the bytecode of {_}MyImpl{_}, which is picked up and preferred by _groovyc_
over the non-synthetic method in {_}MyImplBase{_}.
In case this is related: The synthetic bridge method is selected when using
reflection as well, causing the inferred type by javac and reflection to
diverge:
{code:java}
Method getNumber = MyImpl.class.getMethod("getValue");
// public java.lang.Object MyImpl.getValue() {code}
Workarounds: * Disable static compilation
* An explicit cast to Long in SimpleCaller.
* Explicitly repeat the method signature by repeating the method signature
* If possible, add/Move the implements to MyImplBase - then the synthetic
method is in the same class as the real one, which _groovyc_ is able to detect.
Using generics in the Interface doesn't work either (probably due to type
erasure).
Seems to be a more generalized issue when compared to the similar
[GROOVY-5003|https://issues.apache.org/jira/browse/GROOVY-5003]
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