More precise array_keys return type

Author: staabm

src/Type/Php/ArrayKeysFunctionDynamicReturnTypeExtension.php

@@ -6,10 +6,14 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Php\PhpVersion;
 use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\Accessory\AccessoryArrayListType;
+use PHPStan\Type\ArrayType;
 use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\GeneralizePrecision;
 use PHPStan\Type\NeverType;
 use PHPStan\Type\NullType;
 use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
 use function count;
 use function strtolower;
 
@@ -27,7 +31,7 @@ public function isFunctionSupported(FunctionReflection $functionReflection): boo
 
 	public function getTypeFromFunctionCall(FunctionReflection $functionReflection, FuncCall $functionCall, Scope $scope): ?Type
 	{
-		if (count($functionCall->getArgs()) !== 1) {
+		if (count($functionCall->getArgs()) < 1) {
 			return null;
 		}
 
@@ -36,7 +40,22 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 			return $this->phpVersion->arrayFunctionsReturnNullWithNonArray() ? new NullType() : new NeverType();
 		}
 
-		return $arrayType->getKeysArray();
+		$keysArray = $arrayType->getKeysArray();
+		if (count($functionCall->getArgs()) === 1) {
+			return $keysArray;
+		}
+
+		$newArrayType = $keysArray;
+		if (!$keysArray->isConstantArray()->no()) {
+			$newArrayType = new ArrayType(
+				$keysArray->getIterableKeyType()->generalize(GeneralizePrecision::lessSpecific()),
+				$keysArray->getIterableValueType()->generalize(GeneralizePrecision::lessSpecific()),
+			);
+		}
+		if ($keysArray->isList()->yes()) {
+			$newArrayType = TypeCombinator::intersect($newArrayType, new AccessoryArrayListType());
+		}
+		return $newArrayType;
 	}
 
 }

tests/PHPStan/Analyser/nsrt/bug-11928.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace Bug11928;
+
+use function PHPStan\Testing\assertType;
+
+function doFoo()
+{
+	$a = [2 => 1, 3 => 2, 4 => 1];
+
+	$keys = array_keys($a, 1); // returns [2, 4]
+	assertType('list<int>', $keys);
+
+	$keys = array_keys($a); // returns [2, 3, 4]
+	assertType('array{2, 3, 4}', $keys);
+}
+
+function doFooStrings() {
+	$a = [2 => 'hi', 3 => '123', 'xy' => 5];
+	$keys = array_keys($a, 1);
+	assertType('list<int|string>', $keys);
+
+	$keys = array_keys($a);
+	assertType("array{2, 3, 'xy'}", $keys);
+}
+
+/**
+ * @param array<int, int> $array
+ * @param list<int> $list
+ * @param array<string, string> $strings
+ * @return void
+ */
+function doFooBar(array $array, array $list, array $strings) {
+	$keys = array_keys($strings, "a", true);
+	assertType('list<string>', $keys);
+
+	$keys = array_keys($strings, "a", false);
+	assertType('list<string>', $keys);
+
+	$keys = array_keys($array, 1, true);
+	assertType('list<int>', $keys);
+
+	$keys = array_keys($array, 1, false);
+	assertType('list<int>', $keys);
+
+	$keys = array_keys($list, 1, true);
+	assertType('list<int<0, max>>', $keys);
+
+	$keys = array_keys($list, 1, true);
+	assertType('list<int<0, max>>', $keys);
+}