Curtis Mackie created GROOVY-10085:
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Summary: Class.isCase() documentation does not clarify that
Class.isCase(SomeClass
Key: GROOVY-10085
URL: https://issues.apache.org/jira/browse/GROOVY-10085
Project: Groovy
Issue Type: Bug
Components: Documentation, groovy-runtime
Affects Versions: 4.0.0-alpha-3, 3.0.8
Environment: Pop!_OS 20.04 LTS
Linux Kernel 5.11.0-7614-generic
Reporter: Curtis Mackie
>From the documentation for Groovy's java.lang.Class extensions:
{panel:title=public boolean isCase(Object switchValue)}
Special 'Case' implementation for Class, which allows testing for a certain
class in a switch statement. For example:
{code:java}
switch( obj ) {
case List :
// obj is a list
break;
case Set :
// etc
}{code}
{panel}
Reading that, a person might reasonably be confused by the following behavior:
{code:groovy}
class SomeClass {}
switch (SomeClass) {
case Class:
// we expect to go here
println("case Class")
break
/* ... more cases here, presumably ... */
default:
// but we end up here?
println("default")
break
}
{code}
Looking at the code, I believe this is intentional - because TestClass is
itself a Class, isCase() uses isAssignableFrom() rather than the expected
isInstance(), and Class is not assignable from the unrelated SomeClass type.
Since this case is ambiguous, the code clearly cannot do both things, and we
shouldn't change the existing behavior in case any applications depend on it.
However, we could provide better documentation so it's clear that using this
with a Class will not work as expected.
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