Fix phpstan/phpstan#14215: Nonexistent offset detection on lists with count() -1#5116
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Fix phpstan/phpstan#14215: Nonexistent offset detection on lists with count() -1#5116phpstan-bot wants to merge 1 commit intophpstan:2.1.xfrom
count() -1#5116phpstan-bot wants to merge 1 commit intophpstan:2.1.xfrom
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… `count() - 1` - Extended TypeSpecifier to detect `count($list) - K` patterns in comparisons, not just plain `count($list)` - Adjusted sizeType computation to account for the subtraction value - List offset inference now works with both `$index < count($list) - K` and `$index <= count($list) - K` (when K >= 1) - Non-empty array narrowing threshold adjusted for subtraction - New regression test in tests/PHPStan/Rules/Arrays/data/bug-14215.php
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VincentLanglet
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VincentLanglet
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Seems interesting, dunno if you plan/want to work on it @staabm ?
| $sizeType = $leftType->shift($offset); | ||
| $sizeType = $leftType->shift($offset + $subtraction); | ||
| } else { | ||
| $sizeType = $leftType; |
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Shouldn't we add $substraction here too ?
| $subtraction = $expr->right->right->value; | ||
| } | ||
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| if ( |
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I think the bot is trying to support thing like
if (3 < count($array) - 1)
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I can have a look. If you are interested feel free to take it |
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Summary
PHPStan was reporting false positive "Offset might not exist" errors when accessing a list element after a
$index < count($array) - 1or$index <= count($array) - 1guard. This extends the fix from #5090 (which handled plaincount($array)) to also handlecount($array) - Kpatterns.Changes
src/Analyser/TypeSpecifier.phpto extractcount()/sizeof()calls fromBinaryOp\Minusexpressions (e.g.count($list) - 1)sizeTypecomputation to account for the subtraction value K when narrowing the count type$index <= count($list) - Kis safe when K >= 1 (equivalent to$index < count($list) - (K-1))Root cause
The
TypeSpecifieronly looked forFuncCallnodes matchingcount/sizeofon the right side of comparisons. When the right side wasBinaryOp\Minus(FuncCall(count), Int_(K)), it was not recognized, so no offset validity inference was made. The fix extracts the count call from the minus expression and adjusts the comparison semantics by the subtraction amount.Test
Added
tests/PHPStan/Rules/Arrays/data/bug-14215.phpwith test cases for:$index < count($array) - 1with positive-int (no error)$index <= count($array) - 1with positive-int (no error)$index <= count($array) - 1with plain int (still reports - could be negative)$index < count($array) - 1withint<0, max>(no error)$index <= count($array) - 1withint<0, max>(no error)$index < count($array) - 2/$index <= count($array) - 2with positive-int (no error)sizeof()variant (no error)count($array) - 1 > $index(no error)Fixes phpstan/phpstan#14215