Fix phpstan/phpstan#2572: Optional templated args not provided cause unbound template errors#5175
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…rams - When a template type is only used on a variadic parameter and no arguments are passed, it was incorrectly reported as unresolvable - Fixed by inferring NeverType for variadic parameters with no arguments in GenericParametersAcceptorResolver, since an empty variadic means the element type is never - Added regression tests in both rule test and NSRT format Closes phpstan/phpstan#2572
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Summary
When a function has a template type bound to a variadic parameter (e.g.
@param TR ...$elts) and the function is called without providing any variadic arguments, PHPStan incorrectly reports "Unable to resolve the template type TR". Since variadic parameters are optional, not providing them should not trigger this error.Changes
src/Reflection/GenericParametersAcceptorResolver.phpto inferNeverTypefor variadic parameters that receive no arguments, instead of leaving the template type asErrorTypetests/PHPStan/Rules/Functions/data/bug-2572.phpandtests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.phptests/PHPStan/Analyser/nsrt/bug-2572.phpRoot cause
In
GenericParametersAcceptorResolver::resolve(), all template types are initially mapped toErrorType, then overwritten by types inferred from actual arguments. When a variadic parameter receives no arguments, it was simply skipped (continue), leaving its template type asErrorType. TheFunctionCallParametersCheckthen saw thisErrorTypeand reported the template as unresolvable.The fix adds an
elseif ($param->isVariadic())branch that infers the template type fromNeverTypeinstead of skipping. This is semantically correct: an empty variadic parameter means an empty array, and the element type of an empty array isnever. This causesTE|TRto resolve toTE|never=TE, which is the expected behavior.Test
collect("a")(previously a false positive) andcollect("a", "b", "c")(always worked)collect("a")infers type'a'andcollect("a", "b", "c")infers type'a'|'b'|'c'Fixes phpstan/phpstan#2572