Fix implode losing non-empty-string when ConstantArrayType has all-optional keys#5578
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VincentLanglet merged 3 commits intophpstan:2.1.xfrom May 2, 2026
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…tional keys When a ConstantArrayType has all-optional keys (e.g. from union-typed key expressions in loops), ImplodeFunctionReturnTypeExtension's inferConstantType() enumerated every optional-key subset including the empty array. This produced '' as a possible implode result, which generalized to literal-string and lost the non-empty-string guarantee. Pass the isIterableAtLeastOnce() result into inferConstantType() and filter out the empty-array partial when the array is guaranteed non-empty. Closes phpstan/phpstan#14558
Instead of a separate array_filter step before the loop, skip empty partials directly inside the foreach that builds ConstantStringType values. This is simpler and avoids the extra array_filter/array_values calls. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
VincentLanglet
approved these changes
May 1, 2026
staabm
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May 2, 2026
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Summary
ImplodeFunctionReturnTypeExtension::inferConstantType()to respectisIterableAtLeastOnce()when enumerating optional-key subsets of aConstantArrayType''as a possible result''result generalizes toliteral-stringduring loop iterations, which contaminates the union and causesnon-empty-string/non-falsy-stringto widen to plainstringTest plan
tests/PHPStan/Analyser/nsrt/bug-14558.phpwith both playground scenarios from the issuemake testspasses (11,974 tests, 79,546 assertions)make phpstanpasses (no errors)make cs-fixpasses (no violations)Closes phpstan/phpstan#14558