Fix false positive non-existing-offset after array_key_last

Author: staabm

Diff for: src/Analyser/TypeSpecifier.php

@@ -662,7 +662,29 @@ public function specifyTypesInCondition(
 				throw new ShouldNotHappenException();
 			}
 			if ($context->null()) {
-				return $this->specifyTypesInCondition($scope->exitFirstLevelStatements(), $expr->expr, $context)->setRootExpr($expr);
+				$specifiedTypes = $this->specifyTypesInCondition($scope->exitFirstLevelStatements(), $expr->expr, $context)->setRootExpr($expr);
+
+				if (
+					$expr->expr instanceof FuncCall
+					&& $expr->expr->name instanceof Name
+					&& $expr->expr->name->toLowerString() === 'array_key_last'
+					&& count($expr->expr->getArgs()) >= 1
+				) {
+					$arrayArg = $expr->expr->getArgs()[0]->value;
+					$arrayType = $scope->getType($arrayArg);
+					if (
+						$arrayType->isArray()->yes()
+						&& $arrayType->isIterableAtLeastOnce()->yes()
+					) {
+						$dimFetch = new ArrayDimFetch($arrayArg, $expr->var);
+
+						return $specifiedTypes->unionWith(
+							$this->create($dimFetch, $arrayType->getLastIterableValueType(), TypeSpecifierContext::createTrue(), $scope),
+						);
+					}
+				}
+
+				return $specifiedTypes;
 			}
 
 			return $this->specifyTypesInCondition($scope->exitFirstLevelStatements(), $expr->var, $context)->setRootExpr($expr);

Diff for: tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -780,4 +780,16 @@ public function testInternalClassesWithOverloadedOffsetAccessInvalid84(): void
 		$this->analyse([__DIR__ . '/data/internal-classes-overload-offset-access-invalid-php84.php'], []);
 	}
 
+	public function testArrayDimFetchAfterArrayKeyFirstOrLast(): void
+	{
+		$this->reportPossiblyNonexistentGeneralArrayOffset = true;
+
+		$this->analyse([__DIR__ . '/data/array-dim-after-array-key-first-or-last.php'], [
+			[
+				'Offset null does not exist on array{}.',
+				17,
+			],
+		]);
+	}
+
 }

Diff for: tests/PHPStan/Rules/Arrays/data/array-dim-after-array-key-first-or-last.php

@@ -0,0 +1,47 @@
+<?php declare(strict_types = 1);
+
+namespace ArrayDimAfterArrayKeyFirstOrLast;
+
+class HelloWorld
+{
+	/**
+	 * @param list<string> $hellos
+	 */
+	public function last(array $hellos): string
+	{
+		if ($hellos !== []) {
+			$lastHelloKey = array_key_last($hellos);
+			return $hellos[$lastHelloKey];
+		} else {
+			$lastHelloKey = array_key_last($hellos);
+			return $hellos[$lastHelloKey];
+		}
+	}
+
+	/**
+	 * @param list<string> $hellos
+	 */
+	public function first(array $hellos): string
+	{
+		if ($hellos !== []) {
+			$firstHelloKey = array_key_first($hellos);
+			return $hellos[$firstHelloKey];
+		}
+
+		return 'nothing';
+	}
+
+	/**
+	 * @param array{first: int, middle: float, last: bool} $hellos
+	 */
+	public function shape(array $hellos): int|bool
+	{
+		$firstHelloKey = array_key_first($hellos);
+		$lastHelloKey = array_key_last($hellos);
+
+		if (rand(0,1)) {
+			return $hellos[$firstHelloKey];
+		}
+		return $hellos[$lastHelloKey];
+	}
+}