Fix incorrect narrowing of nested array after assignment with non-constant key

When assigning to a nested array with a non-constant key like
`$array[$id]['state'] = 'foo'`, PHPStan incorrectly inferred that ALL
elements of the outer array had the narrowed type, not just the one
being modified. For example, `array<int, array{state: string}>` became
`non-empty-array<int, array{state: 'foo'}>` instead of the correct
`non-empty-array<int, array{state: string}>`.

The fix ensures that when the outer array key is non-constant (no
constant scalar decomposition), the new value type is unioned with
the existing item type rather than replacing it entirely, since we
cannot know which specific element was modified.

Fixes phpstan/phpstan#13857

Author: staabm

src/Analyser/ExprHandler/AssignHandler.php

@@ -980,7 +980,9 @@ private function produceArrayDimFetchAssignValueToWrite(array $dimFetchStack, ar
 				}
 
 			} else {
-				$valueToWrite = $offsetValueType->setOffsetValueType($offsetType, $valueToWrite, $i === 0);
+				$unionValues = $i === 0
+					|| ($offsetType !== null && count($offsetType->getConstantScalarTypes()) === 0);
+				$valueToWrite = $offsetValueType->setOffsetValueType($offsetType, $valueToWrite, $unionValues);
 			}
 
 			if ($arrayDimFetch === null || !$offsetValueType->isList()->yes()) {

src/DependencyInjection/AutowiredAttributeServicesExtension.php

@@ -139,7 +139,7 @@ public function loadConfiguration(): void
 
 	/**
 	 * @param class-string $className
-	 * @param array<lowercase-string, non-empty-list<TargetMethodParameter<AutowiredParameter>>> $constructorParameters
+	 * @param array<lowercase-string, list<TargetMethodParameter<AutowiredParameter>>> $constructorParameters
 	 */
 	private function processConstructorParameters(string $className, ServiceDefinition $definition, array $constructorParameters): void
 	{

tests/PHPStan/Analyser/nsrt/assign-nested-arrays.php

@@ -14,7 +14,7 @@ public function doFoo(int $i)
 		$array[$i]['bar'] = 1;
 		$array[$i]['baz'] = 2;
 
-		assertType('non-empty-array<int, array{bar: 1, baz: 2}>', $array);
+		assertType('non-empty-array<int, array{bar: 1, baz?: 2}>', $array);
 	}
 
 	public function doBar(int $i, int $j)
@@ -27,7 +27,7 @@ public function doBar(int $i, int $j)
 		echo $array[$i][$j]['bar'];
 		echo $array[$i][$j]['baz'];
 
-		assertType('non-empty-array<int, non-empty-array<int, array{bar: 1, baz: 2}>>', $array);
+		assertType('non-empty-array<int, non-empty-array<int, array{bar: 1, baz?: 2}>>', $array);
 	}
 
 }

tests/PHPStan/Analyser/nsrt/bug-10438.php

@@ -25,7 +25,7 @@ public function extract(SimpleXMLElement $data, string $type = 'Meta'): array
 			$meta[$key] = [];
 			assertType('array{}', $meta[$key]);
 			foreach ($tag->{$valueName} as $value) {
-				assertType('list<string>', $meta[$key]);
+				assertType('list<string>|string', $meta[$key]);
 				$meta[$key][] = (string)$value;
 			}
 		}

tests/PHPStan/Analyser/nsrt/bug-13857.php

@@ -0,0 +1,24 @@
+<?php declare(strict_types = 1);
+
+namespace Bug13857;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param array<int, array{state: string}> $array
+ */
+function test(array $array, int $id): void {
+	$array[$id]['state'] = 'foo';
+	// only one element was set to 'foo', not all of them.
+	// correct type would be: non-empty-array<int, array{state: string}>
+	assertType('non-empty-array<int, array{state: string}>', $array);
+}
+
+/**
+ * @param array<string, array{name: string, age: int}> $people
+ */
+function test2(array $people, string $key): void {
+	$people[$key]['name'] = 'John';
+	// age becomes optional because $key might not exist yet, creating array{name: 'John'} without age
+	assertType('non-empty-array<string, array{name: string, age?: int}>', $people);
+}

tests/PHPStan/Analyser/nsrt/pr-4390.php

@@ -13,6 +13,6 @@ function (string $s): void {
 		}
 	}
 
-	assertType('non-empty-array<int<0, 9>, non-empty-array<int<0, 9>, string>>', $locations);
-	assertType('non-empty-array<int<0, 9>, string>', $locations[0]);
+	assertType('non-empty-array<int<0, 9>, list<string>>', $locations);
+	assertType('list<string>', $locations[0]);
 };

tests/PHPStan/Rules/Arrays/data/bug-11679.php

@@ -31,7 +31,7 @@ public function sayHello(int $index): bool
 		assertType('array<int, array{foo?: bool}>', $this->arr);
 		if (!isset($this->arr[$index]['foo'])) {
 			$this->arr[$index]['foo'] = true;
-			assertType('non-empty-array<int, array{foo: true}>', $this->arr);
+			assertType('non-empty-array<int, array{foo?: bool}>', $this->arr);
 		}
 		assertType('array<int, array{foo?: bool}>', $this->arr);
 		return $this->arr[$index]['foo']; // PHPStan does not realize 'foo' is set

tests/PHPStan/Rules/Arrays/data/slevomat-foreach-array-key-exists-bug.php

@@ -18,7 +18,7 @@ public function doFoo(array $percentageIntervals, array $changes): void
 						assertType('non-empty-array<array{itemsCount: mixed, interval: mixed}>', $intervalResults);
 						assertType('array{itemsCount: mixed, interval: mixed}', $intervalResults[$key]);
 						$intervalResults[$key]['itemsCount'] += $itemsCount;
-						assertType('non-empty-array<array{itemsCount: (array|float|int), interval: mixed}>', $intervalResults);
+						assertType('non-empty-array<array{itemsCount: mixed, interval: mixed}>', $intervalResults);
 						assertType('array{itemsCount: (array|float|int), interval: mixed}', $intervalResults[$key]);
 					} else {
 						assertType('array<array{itemsCount: mixed, interval: mixed}>', $intervalResults);

tests/PHPStan/Rules/Methods/data/bug-12927.php

@@ -40,7 +40,7 @@ public function sayFoo2(array $list): void
 	{
 		foreach($list as $k => $v) {
 			$list[$k]['abc'] = 'world';
-			assertType("non-empty-list<non-empty-array<string, string>&hasOffsetValue('abc', 'world')>", $list);
+			assertType("non-empty-list<array<string, string>>", $list);
 			assertType("non-empty-array<string, string>&hasOffsetValue('abc', 'world')", $list[$k]);
 		}
 		assertType("list<non-empty-array<string, string>&hasOffsetValue('abc', 'world')>", $list);