Resolve per-element callback return types in array_map for closure and arrow function callbacks

src/Type/Php/ArrayMapFunctionReturnTypeExtension.php

@@ -7,12 +7,16 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Node\Expr\TypeExpr;
+use PHPStan\Node\Printer\ExprPrinter;
+use PHPStan\Parser\ArrayMapArgVisitor;
 use PHPStan\Reflection\FunctionReflection;
+use PHPStan\TrinaryLogic;
 use PHPStan\Type\Accessory\AccessoryArrayListType;
 use PHPStan\Type\Accessory\AccessoryType;
 use PHPStan\Type\Accessory\HasOffsetValueType;
 use PHPStan\Type\Accessory\NonEmptyArrayType;
 use PHPStan\Type\ArrayType;
+use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
@@ -128,9 +132,7 @@
 			if (count($constantArrays) > 0) {
 				$totalCount = TypeCombinator::countConstantArrayValueTypes($constantArrays) * TypeCombinator::countConstantArrayValueTypes([$valueType]);
 				if ($totalCount < ConstantArrayTypeBuilder::ARRAY_COUNT_LIMIT) {
-					$mappedArrayType = $arrayType->mapValueType(static fn (Type $type): Type => $scope->getType(new FuncCall($callback, [
-						new Node\Arg(new TypeExpr($type)),
-					])));
+					$mappedArrayType = $arrayType->mapValueType(static fn (Type $type): Type => self::resolveCallbackReturnType($scope, $callback, $type));
 				} else {
 					$mappedArrayType = TypeCombinator::intersect(new ArrayType(
 						$arrayType->getIterableKeyType(),
@@ -162,6 +164,33 @@
 		return $mappedArrayType;
 	}
 
+	private static function resolveCallbackReturnType(Scope $scope, Node\Expr $callback, Type $argType): Type
+	{
+		if ($callback instanceof Node\Expr\Closure || $callback instanceof Node\Expr\ArrowFunction) {
+			static $cloneCounter = 0;
+
+			$clone = clone $callback;
+			$wrappedType = new ConstantArrayType(
+				[new ConstantIntegerType(0)],
+				[$argType],
+				isList: TrinaryLogic::createYes(),
+			);
+			$clone->setAttribute(ArrayMapArgVisitor::ATTRIBUTE_NAME, [new Node\Arg(new TypeExpr($wrappedType))]);
+			$clone->setAttribute('phpstanCachedTypes', []);
+			$clone->setAttribute(ExprPrinter::ATTRIBUTE_CACHE_KEY, null);
+			$clone->setAttribute('startFilePos', -(++$cloneCounter));
+
+			$closureType = $scope->getType($clone);
+			if ($closureType->isCallable()->yes()) {
+				return $closureType->getCallableParametersAcceptors($scope)[0]->getReturnType();
+			}
+		}
+
+		return $scope->getType(new FuncCall($callback, [
+			new Node\Arg(new TypeExpr($argType)),
+		]));
+	}
+
 	/**
 	 * @return list<AccessoryType>
 	 */

tests/PHPStan/Analyser/nsrt/array-map.php

@@ -95,8 +95,8 @@ public function doFoo(): void
 
 		assertType("array{'0', '1'}", array_map('strval', $a));
 		assertType("array{'0', '1'}", array_map(strval(...), $a));
-		assertType("array{'0'|'1', '0'|'1'}", array_map(fn ($v) => strval($v), $a));
-		assertType("array{'0'|'1', '0'|'1'}", array_map(fn ($v) => (string)$v, $a));
+		assertType("array{'0', '1'}", array_map(fn ($v) => strval($v), $a));
+		assertType("array{'0', '1'}", array_map(fn ($v) => (string)$v, $a));
 	}
 
 	public function doFizzBuzz(): void

tests/PHPStan/Analyser/nsrt/bug-10685.php

@@ -19,7 +19,7 @@ function identity(mixed $value): mixed
 
 	public function doFoo(): void
 	{
-		assertType('array{1|2|3, 1|2|3, 1|2|3}', array_map(fn($i) => $i, [1, 2, 3]));
+		assertType('array{1, 2, 3}', array_map(fn($i) => $i, [1, 2, 3]));
 		assertType('array{1, 2, 3}', array_map($this->identity(...), [1, 2, 3]));
 	}
 

tests/PHPStan/Analyser/nsrt/bug-11656.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug11656;
+
+use function PHPStan\Testing\assertType;
+
+class Test
+{
+	/**
+	 * @param array{string[], string} $data
+	 */
+	public function test($data): string
+	{
+		$data = array_map(static fn ($value) => $value, $data);
+
+		assertType("array{array<string>, string}", $data);
+
+		return $data[1];
+	}
+}

tests/PHPStan/Analyser/nsrt/bug-14649.php

@@ -0,0 +1,80 @@
+<?php // lint >= 8.1
+
+declare(strict_types = 1);
+
+namespace Bug14649;
+
+use function PHPStan\Testing\assertType;
+
+enum Role: string
+{
+    case OWNER = 'OWNER';
+    case ADMIN = 'ADMIN';
+    case EDITOR = 'EDITOR';
+
+    public function isGreaterThanOrEqual(Role $role): bool
+    {
+		$map = array_map(
+            static fn (Role $role): string => $role->value,
+            self::cases()
+        );
+
+		assertType("array{'OWNER', 'ADMIN', 'EDITOR'}", $map);
+
+        $hierarchy = array_flip($map);
+
+		assertType("array{OWNER: 0, ADMIN: 1, EDITOR: 2}", $hierarchy);
+
+        return $hierarchy[$this->value] <= $hierarchy[$role->value];
+    }
+}
+
+function testArrowFunctionArithmetic(): void
+{
+	$arr = [1, 2, 3];
+	$result = array_map(fn(int $x): int => $x * 2, $arr);
+	assertType("array{2, 4, 6}", $result);
+}
+
+function testClosureArithmetic(): void
+{
+	$arr = [1, 2, 3];
+	$result = array_map(function (int $x): int { return $x * 2; }, $arr);
+	assertType("array{2, 4, 6}", $result);
+}
+
+function testArrowFunctionStringConcat(): void
+{
+	$arr = ['a', 'b', 'c'];
+	$result = array_map(fn(string $s): string => $s . '_suffix', $arr);
+	assertType("array{'a_suffix', 'b_suffix', 'c_suffix'}", $result);
+}
+
+function testNamedFunctionCallback(): void
+{
+	$arr = ['FOO', 'BAR', 'BAZ'];
+	$result = array_map('strtolower', $arr);
+	assertType("array{'foo', 'bar', 'baz'}", $result);
+}
+
+enum IntEnum: int
+{
+	case A = 10;
+	case B = 20;
+}
+
+function testIntBackedEnum(): void
+{
+	$result = array_map(
+		static fn (IntEnum $e): int => $e->value,
+		IntEnum::cases()
+	);
+	assertType("array{10, 20}", $result);
+}
+
+function testClosureWithStringKeys(): void
+{
+	$arr = ['x' => 1, 'y' => 2];
+	$result = array_map(fn(int $v): string => (string)$v, $arr);
+	assertType("array{x: '1', y: '2'}", $result);
+}