This specific distinction seems to be very important for Psalm, as `explode()` and
`lowercase-string` are used aggressively across the codebase.
Also, this change expands the baseline by a few entries, since some of the code locations
instide Psalm itself have un-checked list destructuring operations, as well as array
access calls on potentially undefined array keys produced by `explode()`, which were
previously just `list<string>`, and are now `array{0: string, 1?: string}`, which is
a bit more precise.
* in PHP 8.0, `ReflectionUnionType` is composed on `ReflectionNamedType`s
* in PHP 8.1, `ReflectionIntersectionType` is composed of `ReflectionNamedType`s
* in PHP 8.2, `ReflectionUnionType` is composed of `ReflectionIntersectionType|ReflectionNamedType`s
Slight variations for each PHP version.
As per local testing, this doesn't work yet.
## Local testing setup:
I did some digging to make sure that the stubs work as expected.
Here's what I did to validate this patch locally (since I don't think it can really be fully automated)
## Create a dummy file to verify used symbols
```php
<?php
namespace Testing;
/** @return \ReflectionClass<\stdClass> */
function getAClass(): \ReflectionClass { throw new \Exception('irrelevant'); }
function getAnUnionType(): \ReflectionUnionType { throw new \Exception('irrelevant'); }
function getAnIntersectionType(): \ReflectionIntersectionType { throw new \Exception('irrelevant'); }
// verifying that `getName()` is stubbed in all versions: this should always be a `class-string<\stdClass>`
$name = getAClass()->getName();
// union types should appear starting with PHP 8.0. Starting with PHP 8.2, they allow for intersections.
$unionTypes = getAnUnionType()->getTypes();
// intersection types should appear starting with PHP 8.1
$intersectionTypes = getAnIntersectionType()->getTypes();
$results = [$name, $unionTypes, $intersectionTypes];
/** @psalm-trace $results */ // tracing this will show us the differences between versions
return $results;
```
## Run the script against various `vimeo/psalm` versions
```sh
docker run --rm -ti -v $(pwd):/app -w /app php:7.4 ./psalm --php-version=7.4 --no-cache reflection-test.php | grep Trace
docker run --rm -ti -v $(pwd):/app -w /app php:8.0 ./psalm --php-version=8.0 --no-cache reflection-test.php | grep Trace
docker run --rm -ti -v $(pwd):/app -w /app php:8.1 ./psalm --php-version=8.1 --no-cache reflection-test.php | grep Trace
docker run --rm -ti -v $(pwd):/app -w /app php:8.2.0RC7-cli ./psalm --php-version=8.2 --no-cache reflection-test.php | grep Trace
```
## Evaluate output
```
❯ docker run --rm -ti -v $(pwd):/app -w /app php:7.4 ./psalm --php-version=7.4 --no-cache reflection-test.php | grep Trace
ERROR: Trace - reflection-test.php:20:1 - $results: list{class-string<stdClass>, mixed, mixed} (see https://psalm.dev/224)
❯ docker run --rm -ti -v $(pwd):/app -w /app php:8.0 ./psalm --php-version=8.0 --no-cache reflection-test.php | grep Trace
ERROR: Trace - reflection-test.php:20:1 - $results: list{class-string<stdClass>, non-empty-list<ReflectionNamedType>, mixed} (see https://psalm.dev/224)
❯ docker run --rm -ti -v $(pwd):/app -w /app php:8.1 ./psalm --php-version=8.1 --no-cache reflection-test.php | grep Trace
ERROR: Trace - reflection-test.php:20:1 - $results: list{class-string<stdClass>, non-empty-list<ReflectionNamedType>, non-empty-list<ReflectionNamedType>} (see https://psalm.dev/224)
psalm on feature/#8720-improve-types-and-purity-for-reflection-symbols [!?] via 🐘 v8.1.13 via ❄️ impure (nix-shell) took 4s
❯ docker run --rm -ti -v $(pwd):/app -w /app php:8.2.0RC7-cli ./psalm --php-version=8.2 --no-cache reflection-test.php | grep Trace
ERROR: Trace - reflection-test.php:20:1 - $results: list{class-string<stdClass>, non-empty-list<ReflectionNamedType>, non-empty-list<ReflectionNamedType>} (see https://psalm.dev/224)
```
These templates were leading to false positives: assuming
an `object` is given as input, the inferred return
type would always have been `true`, which is obviously
not valid.
Removing them is the healthier alternative, for now.
Ref: https://github.com/vimeo/psalm/pull/8722#discussion_r1027102713
As per @weirdan's feedback, we can prevent
the usage of `object` instances that
implement `__invoke()`, as well as `array`
callables, by declaring the ctor argument of
`ReflectionFunction` to be either a real `Closure`,
or a `callable-string`.
While this may not be 100% of scenarios, it is a
healthy way to identify errors in userland.
Ref: https://github.com/vimeo/psalm/pull/8722#discussion_r1027151421
