Fix

Author: VincentLanglet

src/Type/Constant/ConstantArrayType.php

@@ -734,7 +734,9 @@ public function unsetOffset(Type $offsetType): Type
 					$k++;
 				}
 
-				return new self($newKeyTypes, $newValueTypes, $this->nextAutoIndexes, $newOptionalKeys, TrinaryLogic::createNo());
+				$isList = $this->isList()->and(TrinaryLogic::createFromBoolean($i === count($this->keyTypes) - 1));
+
+				return new self($newKeyTypes, $newValueTypes, $this->nextAutoIndexes, $newOptionalKeys, $isList);
 			}
 
 			return $this;

src/Type/Constant/ConstantArrayTypeBuilder.php

@@ -109,6 +109,9 @@ public function setOffsetValueType(?Type $offsetType, Type $valueType, bool $opt
 				}
 
 				$max = max($this->nextAutoIndexes);
+				if ($max !== count($this->keyTypes)) {
+					$this->isList = TrinaryLogic::createNo();
+				}
 
 				$this->keyTypes[] = new ConstantIntegerType($max);
 				$this->valueTypes[] = $valueType;

tests/PHPStan/Analyser/nsrt/array-is-list-unset.php

@@ -19,7 +19,7 @@ function () {
 	assertType('true', array_is_list($a));
 	unset($a[2]);
 	assertType('array{1, 2}', $a);
-	assertType('false', array_is_list($a));
+	assertType('true', array_is_list($a));
 	$a[] = 4;
 	assertType('array{0: 1, 1: 2, 3: 4}', $a);
 	assertType('false', array_is_list($a));