Christopher Smith created GROOVY-11364:
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Summary: STC loses generic specialization on inheritance
Key: GROOVY-11364
URL: https://issues.apache.org/jira/browse/GROOVY-11364
Project: Groovy
Issue Type: Bug
Components: Static Type Checker
Affects Versions: 4.0.21, 4.0.15
Reporter: Christopher Smith
When a base class contains a type parameter {{<N>}} and a method returns {{N}},
the STC believes that the return type is the superclass bound of {{N}} and not
the actual type of {{N}}. Overriding the method in the subclass with the
specific type does not fix the problem.
{code:groovy}
package bug.groovy
import groovy.transform.CompileStatic
@CompileStatic
abstract class BugRepro<N extends Number> {
protected N process(N input) { input }
}
@CompileStatic
class IntegerRepro extends BugRepro<Integer> {
static void consume(Optional<Integer> input) {}
// The compilation fails with or without this override
@Override
protected Integer process(Integer input) { super.process(input) }
void run() {
consume(Optional.of(42).map(this::process))
}
}
{code}
Error:
{code}
Groovy:[Static type checking] - Cannot call
bug.groovy.IntegerRepro#consume(java.util.Optional<java.lang.Integer>) with
arguments [java.util.Optional<java.lang.Number>]
{code}
Expected: The compiler recognizes that {{N}} at the call site is {{Integer}}.
This bug appears to have been introduced in 4.0.15; the code compiles correctly
in 4.0.14. The bug is still present in 4.0.21.
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