Fix false positive with isset() and empty()

src/Analyser/EnsuredNonNullabilityResultExpression.php

@@ -12,10 +12,17 @@ class EnsuredNonNullabilityResultExpression
 
 	private Type $originalType;
 
-	public function __construct(Expr $expression, Type $originalType)
+	private Type $originalNativeType;
+
+	public function __construct(
+		Expr $expression,
+		Type $originalType,
+		Type $originalNativeType
+	)
 	{
 		$this->expression = $expression;
 		$this->originalType = $originalType;
+		$this->originalNativeType = $originalNativeType;
 	}
 
 	public function getExpression(): Expr
@@ -28,4 +35,9 @@ public function getOriginalType(): Type
 		return $this->originalType;
 	}
 
+	public function getOriginalNativeType(): Type
+	{
+		return $this->originalNativeType;
+	}
+
 }

src/Analyser/MutatingScope.php

@@ -2958,7 +2958,7 @@ public function unsetExpression(Expr $expr): self
 		return $this;
 	}
 
-	public function specifyExpressionType(Expr $expr, Type $type): self
+	public function specifyExpressionType(Expr $expr, Type $type, ?Type $nativeType = null): self
 	{
 		if ($expr instanceof Node\Scalar || $expr instanceof Array_) {
 			return $this;
@@ -2998,8 +2998,12 @@ public function specifyExpressionType(Expr $expr, Type $type): self
 			$variableTypes = $this->getVariableTypes();
 			$variableTypes[$variableName] = VariableTypeHolder::createYes($type);
 
+			if ($nativeType === null) {
+				$nativeType = $type;
+			}
+
 			$nativeTypes = $this->nativeExpressionTypes;
-			$nativeTypes[sprintf('$%s', $variableName)] = $type;
+			$nativeTypes[sprintf('$%s', $variableName)] = $nativeType;
 
 			return $this->scopeFactory->create(
 				$this->context,

src/Analyser/NodeScopeResolver.php

@@ -1231,8 +1231,13 @@ private function ensureNonNullability(MutatingScope $scope, Expr $expr, bool $fi
 			$exprType = $scope->getType($exprToSpecify);
 			$exprTypeWithoutNull = TypeCombinator::removeNull($exprType);
 			if (!$exprType->equals($exprTypeWithoutNull)) {
-				$specifiedExpressions[] = new EnsuredNonNullabilityResultExpression($exprToSpecify, $exprType);
-				$scope = $scope->specifyExpressionType($exprToSpecify, $exprTypeWithoutNull);
+				$nativeType = $scope->getNativeType($exprToSpecify);
+				$specifiedExpressions[] = new EnsuredNonNullabilityResultExpression($exprToSpecify, $exprType, $nativeType);
+				$scope = $scope->specifyExpressionType(
+					$exprToSpecify,
+					$exprTypeWithoutNull,
+					TypeCombinator::removeNull($nativeType)
+				);
 			}
 
 			if ($exprToSpecify instanceof PropertyFetch) {
@@ -1259,7 +1264,11 @@ private function ensureNonNullability(MutatingScope $scope, Expr $expr, bool $fi
 	private function revertNonNullability(MutatingScope $scope, array $specifiedExpressions): MutatingScope
 	{
 		foreach ($specifiedExpressions as $specifiedExpressionResult) {
-			$scope = $scope->specifyExpressionType($specifiedExpressionResult->getExpression(), $specifiedExpressionResult->getOriginalType());
+			$scope = $scope->specifyExpressionType(
+				$specifiedExpressionResult->getExpression(),
+				$specifiedExpressionResult->getOriginalType(),
+				$specifiedExpressionResult->getOriginalNativeType()
+			);
 		}
 
 		return $scope;

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10235,6 +10235,11 @@ public function dataBug3990(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3990.php');
 	}
 
+	public function dataBug3991(): array
+	{
+		return $this->gatherAssertTypes(__DIR__ . '/data/bug-3991.php');
+	}
+
 	/**
 	 * @dataProvider dataBug2574
 	 * @dataProvider dataBug2577
@@ -10324,6 +10329,7 @@ public function dataBug3990(): array
 	 * @dataProvider dataBug3985
 	 * @dataProvider dataArraySliceNonEmpty
 	 * @dataProvider dataBug3990
+	 * @dataProvider dataBug3991
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args

tests/PHPStan/Analyser/data/bug-3991.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Bug3991;
+
+use function PHPStan\Analyser\assertNativeType;
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+	/**
+	 * @param \stdClass|array|null $config
+	 *
+	 * @return \stdClass
+	 */
+	public static function email($config = null)
+	{
+		assertNativeType('mixed', $config);
+		assertType('array|stdClass|null', $config);
+		if (empty($config))
+		{
+			assertNativeType('mixed', $config);
+			assertType('array|stdClass|null', $config);
+			$config = new \stdClass();
+		} elseif (! (is_array($config) || $config instanceof \stdClass)) {
+			assertNativeType('mixed~array|stdClass|false|null', $config);
+			assertType('*NEVER*', $config);
+		}
+
+		return new \stdClass($config);
+	}
+}