False positive for undefined variable in try-catch-finally

[Radiergummi]

This is probably related to #5123, but a more general case:
https://psalm.dev/r/17c2685cb3

In all possible code paths, the variable will be defined.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/17c2685cb3

<?php

function f(): int {
    try {
        $x = 10;
    } catch (Throwable $e) {
        $x = 20;
    } finally {
        return $x;
    }
}

Psalm output (using commit 52d2692):

INFO: PossiblyUndefinedVariable - 9:16 - Possibly undefined variable $x defined in try block

[weirdan]

That works only for catch(Throwable), catching any other descendant of Throwable instead would leave $x potentially undefined.

[Radiergummi]

Yup - or if $x is defined in all catch blocks for any exception the try block may throw. A concrete (if a little contrived) example would be something like this:

$start = microtime(true);

try {
  HttpClient::request($req);
  $duration = microtime(true) - $start;
} catch (HttpExeption $e) {
  // ...
  $duration = microtime(true) - $start;
} catch (Throwable $e) {
  $duration = 0;
} finally {
  Log::debug(sprintf('Request took %0.2fs', $duration));
}

In every code path, duration will be defined at the time the code in finally is executed.