Hi Andreas On Fri, Jun 16, 2023 at 9:23 PM Andreas Hennings <[email protected]> wrote: > > Hello list, > I don't know if something like this was already proposed in the past, > I did not find anything. > > Sometimes it would be nice to have a code block inside an expression, like > this: > > public function f(string $key) { > return $this->cache[$key] ??= { > // Calculate a value for $key. > [...] > return $value; > } > }
This has been discussed a few years back when match expressions were proposed. I originally wanted to include support for code blocks along with expressions to offer a more complete alternative to switch statements. The other major use-case for block expressions are arrow functions. Unfortunately, a general solution seems suboptimal due to the subtle semantic differences. See this message for my detailed thought process. https://externals.io/message/109941#109947 I believe it would be best to address blocks for match arms and arrow functions separately. I don't believe blocks for general expressions are that useful in PHP due to the lack of block scoping. Your suggestion to make the block a separate closure could avoid that (as well as the optimizer issue mentioned below) but comes with new issues, like making modification of captured values impossible without by-ref capturing. It seems confusing that fn {} is auto-executed while fn() {} isn't, as the former looks like a shortened version of the latter. fn() => fn {} would also look quite weird. match ($x) { 1 => fn {} } seems ok, except for being somewhat lengthy. On another note, the vote for blocks in short closures has failed lately (https://wiki.php.net/rfc/auto-capture-closure). The message above also addresses the syntax ambiguity you mentioned. The {} syntax would be unambiguous in the most useful contexts (e.g. function parameters, match arms, arrow function bodies, rhs of binary operators, etc.). It is ambiguous in the general expression context due to expression statements (statements containing a single expression followed by `;`), where it's unclear (without lookahead) whether the `{` refers to a statement block or a block expression. Replacing all statement blocks with block expressions comes with the added difficulty of allowing to omit the `;` of block expressions in a expression statement. I remember there also being issues with the optimizer (related to https://www.npopov.com/2022/05/22/The-opcache-optimizer.html#liveness-range-calculation). The details went over my head at the time. I'm interested in picking this back up at some point, at least for match arms. Ilija -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: https://www.php.net/unsub.php
