Paul King created GROOVY-10905:
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Summary: Improve matching no-arg closures to SAM types
Key: GROOVY-10905
URL: https://issues.apache.org/jira/browse/GROOVY-10905
Project: Groovy
Issue Type: Improvement
Reporter: Paul King
Assignee: Paul King
Fix For: 5.x
When matching Closures to SAM types, we have special treatment for Closures
without a formal parameter section. Such Closures may have 0 or 1 arguments,
e.g.:
{code}
foo { println 42 } // zero-arg case
bar { println 'arg:' + it } // one-arg case
{code}
Our current matching says that because of this ambiguity, we know nothing about
the number of parameters, but this assumption is throwing away information: the
fact that we are expecting 0 or 1 args. I'd like to propose for Groovy 5 that
we match 0 or 1-arg SAMs more closely that say a 2-arg SAM for such a Closure.
The impact of this is that there will be less ambiguity errors (or conversely,
less places where we need to cast to get the correct method). It obviously
doesn't help if there are both 0 and 1-arg options available, where casting
would still be required.
Examples:
{code}
def method1(IntUnaryOperator unary) { '1a' }
def method1(IntBinaryOperator binary) { '1b' }
{code}
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