Narrow variable type in switch cases

Author: dmytro-dymarchuk

src/Analyser/NodeScopeResolver.php

@@ -206,6 +206,7 @@
 use function array_merge;
 use function array_pop;
 use function array_reverse;
+use function array_shift;
 use function array_slice;
 use function array_values;
 use function base64_decode;
@@ -1566,10 +1567,12 @@ private function processStmtNode(
 			$throwPoints = $condResult->getThrowPoints();
 			$impurePoints = $condResult->getImpurePoints();
 			$fullCondExpr = null;
+			$defaultCondExprs = [];
 			foreach ($stmt->cases as $caseNode) {
 				if ($caseNode->cond !== null) {
 					$condExpr = new BinaryOp\Equal($stmt->cond, $caseNode->cond);
 					$fullCondExpr = $fullCondExpr === null ? $condExpr : new BooleanOr($fullCondExpr, $condExpr);
+					$defaultCondExprs[] = new BinaryOp\NotEqual($stmt->cond, $caseNode->cond);
 					$caseResult = $this->processExprNode($stmt, $caseNode->cond, $scopeForBranches, $nodeCallback, ExpressionContext::createDeep());
 					$scopeForBranches = $caseResult->getScope();
 					$hasYield = $hasYield || $caseResult->hasYield();
@@ -1580,6 +1583,11 @@ private function processStmtNode(
 					$hasDefaultCase = true;
 					$fullCondExpr = null;
 					$branchScope = $scopeForBranches;
+					$defaultConditions = $this->createBooleanAndFromExpressions($defaultCondExprs);
+					if ($defaultConditions !== null) {
+						$branchScope = $this->processExprNode($stmt, $defaultConditions, $scope, static function (): void {
+						}, ExpressionContext::createDeep())->getTruthyScope()->filterByTruthyValue($defaultConditions);
+					}
 				}
 
 				$branchScope = $branchScope->mergeWith($prevScope);
@@ -6701,6 +6709,29 @@ private function getPhpDocReturnType(ResolvedPhpDocBlock $resolvedPhpDoc, Type $
 		return null;
 	}
 
+	/**
+	 * @param list<Expr> $expressions
+	 */
+	private function createBooleanAndFromExpressions(array $expressions): ?Expr
+	{
+		if (count($expressions) === 0) {
+			return null;
+		}
+
+		if (count($expressions) === 1) {
+			return $expressions[0];
+		}
+
+		$left = array_shift($expressions);
+		$right = $this->createBooleanAndFromExpressions($expressions);
+
+		if ($right === null) {
+			throw new ShouldNotHappenException();
+		}
+
+		return new BooleanAnd($left, $right);
+	}
+
 	/**
 	 * @param array<Node> $nodes
 	 * @return list<Node\Stmt>

src/Analyser/TypeSpecifier.php

@@ -1643,15 +1643,8 @@ private function findTypeExpressionsFromBinaryOperation(Scope $scope, Node\Expr\
 		$leftType = $scope->getType($binaryOperation->left);
 		$rightType = $scope->getType($binaryOperation->right);
 
-		$rightExpr = $binaryOperation->right;
-		if ($rightExpr instanceof AlwaysRememberedExpr) {
-			$rightExpr = $rightExpr->getExpr();
-		}
-
-		$leftExpr = $binaryOperation->left;
-		if ($leftExpr instanceof AlwaysRememberedExpr) {
-			$leftExpr = $leftExpr->getExpr();
-		}
+		$rightExpr = $this->extractExpression($binaryOperation->right);
+		$leftExpr = $this->extractExpression($binaryOperation->left);
 
 		if (
 			$leftType instanceof ConstantScalarType
@@ -1670,6 +1663,39 @@ private function findTypeExpressionsFromBinaryOperation(Scope $scope, Node\Expr\
 		return null;
 	}
 
+	/**
+	 * @return array{Expr, Type, Type}|null
+	 */
+	private function findEnumTypeExpressionsFromBinaryOperation(Scope $scope, Node\Expr\BinaryOp $binaryOperation): ?array
+	{
+		$leftType = $scope->getType($binaryOperation->left);
+		$rightType = $scope->getType($binaryOperation->right);
+
+		$rightExpr = $this->extractExpression($binaryOperation->right);
+		$leftExpr = $this->extractExpression($binaryOperation->left);
+
+		if (
+			$leftType->getEnumCases() === [$leftType]
+			&& !$rightExpr instanceof ConstFetch
+			&& !$rightExpr instanceof ClassConstFetch
+		) {
+			return [$binaryOperation->right, $leftType, $rightType];
+		} elseif (
+			$rightType->getEnumCases() === [$rightType]
+			&& !$leftExpr instanceof ConstFetch
+			&& !$leftExpr instanceof ClassConstFetch
+		) {
+			return [$binaryOperation->left, $rightType, $leftType];
+		}
+
+		return null;
+	}
+
+	private function extractExpression(Expr $expr): Expr
+	{
+		return $expr instanceof AlwaysRememberedExpr ? $expr->getExpr() : $expr;
+	}
+
 	/** @api */
 	public function create(
 		Expr $expr,
@@ -2061,6 +2087,27 @@ public function resolveEqual(Expr\BinaryOp\Equal $expr, Scope $scope, TypeSpecif
 			) {
 				return $this->specifyTypesInCondition($scope, new Expr\BinaryOp\Identical($expr->left, $expr->right), $context)->setRootExpr($expr);
 			}
+
+			if (!$context->null() && TypeCombinator::containsNull($otherType)) {
+				if ($constantType->toBoolean()->isTrue()->yes()) {
+					$otherType = TypeCombinator::remove($otherType, new NullType());
+				}
+
+				if (!$otherType->isSuperTypeOf($constantType)->no()) {
+					return $this->create($exprNode, TypeCombinator::intersect($constantType, $otherType), $context, $scope)->setRootExpr($expr);
+				}
+			}
+		}
+
+		$expressions = $this->findEnumTypeExpressionsFromBinaryOperation($scope, $expr);
+		if ($expressions !== null) {
+			$exprNode = $expressions[0];
+			$enumCaseObjectType = $expressions[1];
+			$otherType = $expressions[2];
+
+			if (!$context->null()) {
+				return $this->create($exprNode, TypeCombinator::intersect($enumCaseObjectType, $otherType), $context, $scope)->setRootExpr($expr);
+			}
 		}
 
 		$leftType = $scope->getType($expr->left);

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -101,10 +101,13 @@ private static function findTestFiles(): iterable
 			define('TEST_FALSE_CONSTANT', false);
 			define('TEST_ARRAY_CONSTANT', [true, false, null]);
 			define('TEST_ENUM_CONSTANT', Foo::ONE);
+			yield __DIR__ . '/data/bug-12432-nullable-enum.php';
 			yield __DIR__ . '/data/new-in-initializers-runtime.php';
 			yield __DIR__ . '/data/scope-in-enum-match-arm-body.php';
 		}
 
+		yield __DIR__ . '/data/bug-12432-nullable-int.php';
+
 		yield __DIR__ . '/../Rules/Comparison/data/bug-6473.php';
 
 		yield __DIR__ . '/../Rules/Methods/data/filter-iterator-child-class.php';

tests/PHPStan/Analyser/data/bug-12432-nullable-enum.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace Bug12432;
+
+use function PHPStan\Testing\assertType;
+
+enum Foo: int
+{
+	case BAR = 1;
+	case BAZ = 2;
+	case QUX = 3;
+}
+
+function requireNullableEnum(?Foo $nullable): ?Foo
+{
+	switch ($nullable) {
+		case Foo::BAR:
+			assertType('Bug12432\Foo::BAR', $nullable);
+		case Foo::BAZ:
+			assertType('Bug12432\Foo::BAR|Bug12432\Foo::BAZ', $nullable);
+			break;
+		case '':
+			assertType('null', $nullable);
+		case null:
+			assertType('null', $nullable);
+			break;
+		case 0:
+			assertType('*NEVER*', $nullable);
+		default:
+			assertType('Bug12432\Foo::QUX', $nullable);
+			break;
+	}
+
+	return $nullable;
+}

tests/PHPStan/Analyser/data/bug-12432-nullable-int.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace Bug12432;
+
+use function PHPStan\Testing\assertType;
+
+function requireNullableInt(?int $nullable): ?int
+{
+	switch ($nullable) {
+		case 1:
+			assertType('1', $nullable);
+		case 2:
+			assertType('1|2', $nullable);
+			break;
+		case '':
+			assertType('0|null', $nullable);
+		case 0:
+			assertType('0|null', $nullable);
+			break;
+		default:
+			assertType('int<min, -1>|int<3, max>', $nullable);
+			break;
+	}
+
+	return $nullable;
+}

tests/PHPStan/Analyser/nsrt/in_array_loose.php

@@ -42,7 +42,7 @@ public function looseComparison(
 			assertType('int|string', $stringOrInt); // could be '1'|'2'|1|2
 		}
 		if (in_array($stringOrNull, ['1', 'a'])) {
-			assertType('string|null', $stringOrNull); // could be '1'|'a'
+			assertType("'1'|'a'", $stringOrNull);
 		}
 	}
 }