Fix phpstan/phpstan#14440: Intersections in class-string<A&B> not correctly detected, reported as string

[phpstan-bot]

Summary

When a ConstantStringType represented a class-string (e.g. from SomeClass::class), its describe() method at typeOnly verbosity level returned just string, losing the class-string information. This caused misleading error messages like:

Method ChildOne::getCounterpartClass() should return class-string but returns string.

After the fix, the error message correctly shows:

Method ChildOne::getCounterpartClass() should return class-string but returns class-string.

Changes

• Modified ConstantStringType::describe() in src/Type/Constant/ConstantStringType.php to return class-string<ClassName> at typeOnly level when the isClassString flag is set
• Added regression test in tests/PHPStan/Rules/Methods/data/bug-14440.php and tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php
• Updated test expectations in 5 existing test files to match improved error messages:
  • tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php (bug-8071)
  • tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php (ClassStringWithUpperBounds)
  • tests/PHPStan/Rules/Methods/CallStaticMethodsRuleTest.php (TemplateTypeInOneBranchOfConditional)
  • tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php (bug-4413, bug-4371, is-subclass-allow-string)

Root cause

ConstantStringType::describe() used a static closure static fn (): string => 'string' for the typeOnly handler, which always returned 'string' regardless of whether the constant represented a class-string. This is inconsistent with GenericClassStringType which includes its generic parameter at all verbosity levels (e.g. class-string<ChildOne>). The fix uses the isClassString flag (set during construction for ::class expressions) to return class-string<ClassName> instead.

Test

Added testBug14440 in ReturnTypeRuleTest with test data reproducing the issue: an abstract class with @return class-string<static&I>, and two final child classes returning each other's ::class. The test verifies the error messages correctly describe the return types as class-string<ChildTwo> and class-string<ChildOne> respectively.

Fixes phpstan/phpstan#14440

[VincentLanglet]

Rather than modifying ConstantStringType::info, consider working on VerbosityLevel::getRecommendedLevelByType

[phpstan-bot]

Done. Here's a summary of the changes addressing the review:

What changed:

1. VerbosityLevel::getRecommendedLevelByType() - Added isClassString()->yes() check to $moreVerboseCallback, so when the accepting type contains a class-string type (e.g., class-string<Exception>), verbosity is bumped to value level.

2. ConstantStringType::describe() - Reverted typeOnly handler back to returning 'string'. Moved the class-string<ClassName> description to the value handler instead, which is only used when VerbosityLevel decides the extra detail is needed.

Why this approach is better:

• The typeOnly level stays clean and generic ('string'), as intended for basic type descriptions
• VerbosityLevel::getRecommendedLevelByType controls when to show extra detail, which is its architectural role
• The value handler in ConstantStringType provides the what — showing class-string<ClassName> when the context warrants it

Test impact: Updated 12 test files and 2 config files where class-string constants now show as class-string<ClassName> instead of quoted 'ClassName' at value verbosity.

[VincentLanglet]

Do not modify AT ALL the ConstantStringType::describe implémentation.

And getRecommendedLevelByType should require a moreVerbose level only if acceptingType is a string.
If a method should return object but return a constantString there is no need for a more verbose type than string.

[phpstan-bot]

Done. Here's a summary of the changes:

What changed:

1. ConstantStringType::describe() - Fully reverted to original. No modifications at all, as the reviewer requested.

2. VerbosityLevel::getRecommendedLevelByType() - Added a check $type->isString()->yes() && $type->isClassString()->yes() in the $moreVerboseCallback. This bumps verbosity to value level only when the accepting type contains a class-string type (e.g., class-string<Exception>). When the accepting type is something like object, verbosity stays at typeOnly and the constant string shows as just string.

3. Test expectations - Updated only the tests where the accepting type contains class-string, changing from string to quoted format (e.g., 'Throwable', 'stdClass'). Tests where the accepting type doesn't contain class-string remain unchanged. Tests that already used value-level verbosity (ImpossibleCheckType, StrictComparison, etc.) were reverted to their original expectations.

4. Baselines - Updated build/phpstan.neon to match the new error messages where string given became 'PHPStan…' given.