Fix #14081: infer offset after array_key_first

src/Analyser/NodeScopeResolver.php

@@ -6108,6 +6108,46 @@
 					$conditionalExpressions = $this->processSureNotTypesForConditionalExpressionsAfterAssign($scope, $var->name, $conditionalExpressions, $falseySpecifiedTypes, $falseyType);
 				}
 
+				if (
+					$assignedExpr instanceof FuncCall
+					&& $assignedExpr->name instanceof Name
+					&& in_array($assignedExpr->name->toLowerString(), ['array_key_first', 'array_key_last'], true)
+					&& count($assignedExpr->getArgs()) >= 1
+				) {
+					$arrayArg = $assignedExpr->getArgs()[0]->value;
+					$arrayType = $scope->getType($arrayArg);
+					$nonNullType = TypeCombinator::removeNull($type);
+					if (
+						$arrayArg instanceof Variable
+						&& is_string($arrayArg->name)
+						&& $arrayType->isArray()->yes()
+						&& !$arrayType->isIterableAtLeastOnce()->yes()
+						&& !$nonNullType instanceof NeverType
+						&& !$type->equals($nonNullType)
+					) {
+						$narrowedArrayType = TypeCombinator::intersect($arrayType, new NonEmptyArrayType());
+
+						$arrayExprString = '$' . $arrayArg->name;
+						$arrayHolder = new ConditionalExpressionHolder([
+							'$' . $var->name => ExpressionTypeHolder::createYes(new Variable($var->name), $nonNullType),
+						], ExpressionTypeHolder::createYes(
+							$arrayArg,
+							$narrowedArrayType,
+						));
+						$conditionalExpressions[$arrayExprString][$arrayHolder->getKey()] = $arrayHolder;
+
+						$dimFetch = new ArrayDimFetch($arrayArg, $var);
+						$dimFetchExprString = sprintf('$%s[$%s]', $arrayArg->name, $var->name);
+						$dimFetchHolder = new ConditionalExpressionHolder([
+							'$' . $var->name => ExpressionTypeHolder::createYes(new Variable($var->name), $nonNullType),
+						], ExpressionTypeHolder::createYes(
+							$dimFetch,
+							$narrowedArrayType->getIterableValueType(),
+						));
+						$conditionalExpressions[$dimFetchExprString][$dimFetchHolder->getKey()] = $dimFetchHolder;
+					}
+				}
+
 				$this->callNodeCallback($nodeCallback, new VariableAssignNode($var, $assignedExpr), $scopeBeforeAssignEval, $storage);
 				$scope = $scope->assignVariable($var->name, $type, $scope->getNativeType($assignedExpr), TrinaryLogic::createYes());
 				foreach ($conditionalExpressions as $exprString => $holders) {

tests/PHPStan/Analyser/nsrt/bug-13546.php

@@ -66,7 +66,7 @@ function mixedLast($mixed): void
 function firstInCondition(array $array)
 {
 	if (($key = array_key_first($array)) !== null) {
-		assertType('list<string>', $array); // could be 'non-empty-list<string>'
+		assertType('non-empty-list<string>', $array);
 		return $array[$key];
 	}
 	assertType('list<string>', $array);

tests/PHPStan/Analyser/nsrt/bug-14081.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug14081Nsrt;
+
+use function PHPStan\Testing\assertType;
+
+/** @param list<string> $list */
+function firstWithNullCheck(array $list): void
+{
+	$key = array_key_first($list);
+	if ($key !== null) {
+		assertType('non-empty-list<string>', $list);
+		assertType('int<0, max>', $key);
+		assertType('string', $list[$key]);
+	}
+}
+
+/** @param list<string> $list */
+function lastWithNullCheck(array $list): void
+{
+	$key = array_key_last($list);
+	if ($key !== null) {
+		assertType('non-empty-list<string>', $list);
+		assertType('int<0, max>', $key);
+		assertType('string', $list[$key]);
+	}
+}
+
+/** @param array<string, int> $map */
+function firstOnMapWithNullCheck(array $map): void
+{
+	$key = array_key_first($map);
+	if ($key !== null) {
+		assertType('non-empty-array<string, int>', $map);
+		assertType('string', $key);
+		assertType('int', $map[$key]);
+	}
+}

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -1145,4 +1145,10 @@ public function testBug11276(): void
 		$this->analyse([__DIR__ . '/data/bug-11276.php'], []);
 	}
 
+	public function testBug14081(): void
+	{
+		$this->reportPossiblyNonexistentGeneralArrayOffset = true;
+		$this->analyse([__DIR__ . '/data/bug-14081.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Arrays/data/bug-14081.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug14081;
+
+class HelloWorld
+{
+	/**
+	 * @param list<string> $list
+	 */
+	public function firstWithNullCheck(array $list): string
+	{
+		$key = array_key_first($list);
+		if ($key !== null) {
+			return $list[$key];
+		}
+
+		return 'nothing';
+	}
+
+	/**
+	 * @param list<string> $list
+	 */
+	public function lastWithNullCheck(array $list): string
+	{
+		$key = array_key_last($list);
+		if ($key !== null) {
+			return $list[$key];
+		}
+
+		return 'nothing';
+	}
+
+	/**
+	 * @param array<string, int> $map
+	 */
+	public function firstOnMapWithNullCheck(array $map): int
+	{
+		$key = array_key_first($map);
+		if ($key !== null) {
+			return $map[$key];
+		}
+
+		return 0;
+	}
+
+	/**
+	 * @param array<string, int> $map
+	 */
+	public function lastOnMapWithNullCheck(array $map): int
+	{
+		$key = array_key_last($map);
+		if ($key !== null) {
+			return $map[$key];
+		}
+
+		return 0;
+	}
+
+	/**
+	 * @param list<string> $list
+	 */
+	public function nullCheckReversed(array $list): string
+	{
+		$key = array_key_first($list);
+		if (null !== $key) {
+			return $list[$key];
+		}
+
+		return 'nothing';
+	}
+}