Hi all,
Safe indexing has been introduced since Groovy 3.0.0, it is useful but
confuses both parser and users sometimes because it is not a real operator
in order to not breaking existing code as possible as we could. For example,
```
// https://issues.apache.org/jira/browse/GROOVY-9522
def a() { null }
def b() { '' }
a()?[b(), a()].join(','):b() // statement with ambiguities
```
The above statement with ambiguities can be parsed into:
1) safe indexing expression, `a()?[[b(), a()]].join([',': b()])`
2) ternary expression, `a() ? ([b(), a()].join(',')) : b()`
As safe indexing(i.e. `?[`) has same precedence with safe reference(i.e.
`?.`), safe indexing has higher precedence than ternary expression. When
ambiguities appear, the expression with ambiguities will be parsed into safe
indexing. As a result, the potential issue is hard for user to find early
and is ususally found when code has been executed...
So I propose to make safe indexing operator `?[` become a real operator,
i.e. it will be defined in the groovy lexer.
* pros:
1) No ambiguities
2) Better parsing performance
* cons:
1) Breaking some existing ternary expressions without spaces between`?` and
`[`, e.g. `true?[0] : [1]` will be broken, so it has to be rewritten to
`true? [0] : [1]`
As Groovy 3 has been released, I proposed to apply the change to Groovy 4.
Any thoughts?
Cheers,
Daniel Sun
-----
Apache Groovy committer & PMC member
Blog: http://blog.sunlan.me
Twitter: @daniel_sun
--
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