Fix condition of fall-through case not used for exhaustive checks

Author: rvanvelzen

src/Analyser/NodeScopeResolver.php

@@ -1449,9 +1449,11 @@ private function processStmtNode(
 			$exitPointsForOuterLoop = [];
 			$throwPoints = $condResult->getThrowPoints();
 			$impurePoints = $condResult->getImpurePoints();
+			$fullCondExpr = null;
 			foreach ($stmt->cases as $caseNode) {
 				if ($caseNode->cond !== null) {
 					$condExpr = new BinaryOp\Equal($stmt->cond, $caseNode->cond);
+					$fullCondExpr = $fullCondExpr === null ? $condExpr : new BooleanOr($fullCondExpr, $condExpr);
 					$caseResult = $this->processExprNode($stmt, $caseNode->cond, $scopeForBranches, $nodeCallback, ExpressionContext::createDeep());
 					$scopeForBranches = $caseResult->getScope();
 					$hasYield = $hasYield || $caseResult->hasYield();
@@ -1460,6 +1462,7 @@ private function processStmtNode(
 					$branchScope = $caseResult->getTruthyScope()->filterByTruthyValue($condExpr);
 				} else {
 					$hasDefaultCase = true;
+					$fullCondExpr = null;
 					$branchScope = $scopeForBranches;
 				}
 
@@ -1481,8 +1484,9 @@ private function processStmtNode(
 				if ($branchScopeResult->isAlwaysTerminating()) {
 					$alwaysTerminating = $alwaysTerminating && $branchFinalScopeResult->isAlwaysTerminating();
 					$prevScope = null;
-					if (isset($condExpr)) {
-						$scopeForBranches = $scopeForBranches->filterByFalseyValue($condExpr);
+					if (isset($fullCondExpr)) {
+						$scopeForBranches = $scopeForBranches->filterByFalseyValue($fullCondExpr);
+						$fullCondExpr = null;
 					}
 					if (!$branchFinalScopeResult->isAlwaysTerminating()) {
 						$finalScope = $branchScope->mergeWith($finalScope);

tests/PHPStan/Analyser/nsrt/bug-11064.php

@@ -0,0 +1,30 @@
+<?php declare(strict_types = 1);
+
+namespace Bug11064;
+
+use function PHPStan\Testing\assertType;
+
+interface IClass {}
+class ClassA implements IClass {}
+class ClassB implements IClass {}
+
+/**
+ * @param null|'nil'|IClass $val
+ */
+function test($val): string {
+	switch (true) {
+		case $val === null:
+		case $val === 'nil':
+			assertType("'nil'|null", $val);
+			return 'null';
+
+		case $val instanceof ClassA:
+			assertType('Bug11064\\ClassA', $val);
+			return 'class a';
+
+		default:
+			assertType('Bug11064\\IClass~Bug11064\\ClassA', $val);
+			throw new RuntimeException('unsupported class: ' . get_class($val));
+	}
+}
+

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -277,10 +277,12 @@ public function testVariableCertaintyInIsset(): void
 				112,
 			],
 			[
-				'Variable $variableInFirstCase in isset() always exists and is not nullable.',
+				// could be Variable $variableInFirstCase in isset() always exists and is not nullable.
+				'Variable $variableInFirstCase in isset() is never defined.',
 				116,
 			],
 			[
+				// could be Variable $variableInSecondCase in isset() always exists and is not nullable.
 				'Variable $variableInSecondCase in isset() is never defined.',
 				117,
 			],