Slow analysis when working with multiple big const arrays

[dpeukert]

Bug report

Getting a value from a big (6500 values in the snippet) const array and using it to access a different similarly sized const array causes PHPStan to take about 70 seconds to analyze the file. I'm fairly sure the affected file in our codebase used to take no significant time to analyse before, but there were some changes to it around the time we updated PHPStan, so I'll check with some older versions of PHPStan to see if it is a regression and update the issue.

EDIT: Doesn't seem like a regression, see times below.

parameters:
    level: 8

./vendor/bin/phpstan analyse -c phpstan.neon --debug -vvv test.php

# PHPStan v1.8.11
# --- consumed 92 MB, total 128 MB, took 67.74 s

# PHPStan v1.8.2
# --- consumed 74 MB, total 132 MB, took 209.80 s

# PHPStan v1.4.8
# --- consumed 74 MB, total 130 MB (time reports 110.67 s)

Code snippet that reproduces the problem

The snippet causes the https://api.phpstan.org/analyse endpoint to return a 502, presumably because of the size, so here's a gist: https://gist.github.com/dpeukert/eadf816dc5cde760c1aa295fc065815e

Expected output

I would expect the analysis to be quicker.

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[mergeable]

This bug report is missing a link to reproduction at phpstan.org/try.

It will most likely be closed after manual review.

[staabm]

@ondrejmirtes what do you think about counting the number of elements in a constant array with a NodeVisitor and turn it into a OversizedArrayType instead of building all constant values into objects at first and let the type-analysis later on turn it into a OversizedArrayType?

doing so early and preventing the building up of all these Constant* object, which finally degrade seems like overhead, when we know a constant array has a certain number of elements..

[ondrejmirtes]

@staabm You don't need to ask me, you can just try out the solution and see if it works. Myself I tried several things in the last few days and none of them worked.

Ideally I'd like a solution that solves this problem for more than just one example. For example this one https://github.com/phpstan/phpstan-src/blob/aa7b1eabd197ef6b7fb2c8eebbb7876aebc0ba6a/tests/PHPStan/Analyser/data/bug-8146.php is really hard. 95% of time is spent in TypeCombinator::union() because PHPStan tries to collapse the arrays in values of the first-level array.

[staabm]

@dpeukert this should be pretty fast now starting with 1.9.5

[dpeukert]

@staabm Thanks for the fix, can confirm that analysis of both the test case and our codebase sped up massively:

./vendor/bin/phpstan analyse -c phpstan.neon --debug -vvv test.php

# PHPStan v1.9.6
# --- consumed 88 MB, total 126 MB, took 0.51 s

[github-actions]

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