Fix phpstan/phpstan#5473: TypeSpecifier should be called in processExprNode

[phpstan-bot]

Summary

When a function/method call with @phpstan-assert was used as a sub-expression (e.g., Assert::notNull($value)->throws(...)), the type narrowing from the assertion was lost. Similarly, assert($x !== null) && assert(strlen($x) > 1) as an expression statement did not properly combine both assertions.

Changes

• Modified src/Analyser/TypeSpecifier.php:
  • In the MethodCall handler, for null context (statement-level), recursively process $expr->var to apply assertions from intermediate calls. This handles chained patterns like Assert::notNull($value)->throws(...).
  • When the method itself also has assertions, union both the method's and var's assertions while preserving the original rootExpr (to avoid breaking impossible check detection).
  • For BooleanAnd with null context, use unionWith instead of intersectWith to properly combine assertions from both sides of &&.

Root cause

The TypeSpecifier only examined the outermost call in a chain when processing statement-level expressions with null context. For Assert::notNull($value)->throws(...), it checked throws() for assertions (finding none) but never examined the intermediate Assert::notNull($value) call which carried the @phpstan-assert !null $value annotation.

For the && case, intersectWith was used for null context which takes the union of types (broader) for common entries and drops entries not in both — losing narrowing information. Using unionWith (which intersects types for common entries and keeps all unique entries) correctly combines both assertions.

Test

Added tests/PHPStan/Analyser/nsrt/bug-5473.php covering:

• Standalone assert call (already worked)
• Chained method call after assert (was broken, now fixed)
• Assignment of assert result (already worked)
• assert() && assert() expression statement (was broken, now fixed)
• Property access after chained assert (was broken, now fixed)

Fixes phpstan/phpstan#5473