Do not remember an equality assertion statement as true when its arguments contain an impure call

[phpstan-bot]

Summary

Since 2.2.15, calling a templated @phpstan-assert =ExpectedType $actual assertion (like PHPUnit's assertSame()) twice with an impure call as an argument reported the second call as alreadyNarrowedType. An example is assertSame($key, $counter->next()) where next() is @phpstan-impure, or random_int(). This PR stops PHPStan from remembering the assertion's true outcome when the call's arguments contain a call that isn't known to be pure.

Changes

• src/Analyser/TypeSpecifier.php: add callOperandsContainNonPureCall(). It runs the existing non-pure-call search (findNonPureCall, now split so the sub-node walk can be reused) over the call's arguments and over what it is called on, without the call itself.
• src/Analyser/StmtHandler/ExpressionHandler.php: only assignExpression() the equality assertion statement as true when its operands contain no non-pure call.
• Analogous cases:
  • Function, method and static method assertion calls were all affected. All three are fixed and tested.
  • The impure call can be in either argument ($expected or $actual). Both positions are covered.
  • I probed the bool-returning @phpstan-assert-if-true =T variant used in a condition. It was already correct, because MutatingScope::filterByTruthyValue() stores the result through TypeSpecifier::create(), which already refuses expressions containing non-pure calls.

Root cause

Commit 14ad31b added storing a void equality-assertion statement's result as true, so that an exact duplicate assertion is reported as always true. Unlike the truthy/falsey path, it used assignExpression() directly. That bypasses the purity check TypeSpecifier::create() normally applies before remembering an expression's value. Because the expression key of assertSame($key, $counter->next()) is identical for both calls, the second call looked up the remembered true. The whole call can't be checked with the regular purity check, because a void assertion function is itself considered impure. So the fix checks only the call's operands.

Test

tests/PHPStan/Rules/Comparison/data/bug-15328.php contains the reproducer from the issue (impure method and random_int()), with an impure $expected argument, plus the same scenarios for a static-method and an instance-method assertion. It is analysed by ImpossibleCheckTypeFunctionCallRuleTest, ImpossibleCheckTypeMethodCallRuleTest and ImpossibleCheckTypeStaticMethodCallRuleTest. Each file also has a duplicate assertion with pure arguments, which is still reported. All three tests fail without the fix.

Fixes phpstan/phpstan#15328