Henri Biestro created JEXL-401:
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Summary: Captured variables should be read-only
Key: JEXL-401
URL: https://issues.apache.org/jira/browse/JEXL-401
Project: Commons JEXL
Issue Type: Improvement
Affects Versions: 3.3
Reporter: Henri Biestro
Fix For: 3.3.1
WHAT:
When a lambda captures local variables, these are copied into the lambda frame
and behave as local variables within the lambda's scope. It would be convenient
to alter this so that captured variables could be made read-only and reject
side-effect operators at parsing time.
WHY:
This is an element of surprise for users with a Java background since captured
variables must be final. It is also surprising when users expect dynamic (non
lexical) scoping and would expect side effects to be carried thru scopes.
The examples below illustrates the 2 ways this can be surprising.
{code}
let x = -42;
const f = y -> x += y; // x is implicitly declared as a copy in the lambda 'f'
frame
f(42);
// x is still -42
{code}
HOW:
By introducing a new feature flag aptly named 'constCapture'. This feature flag
determines whether captured variables are const or not (default).
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