From 94e6e466f44a0dbbcb6182b32628d97a80109305 Mon Sep 17 00:00:00 2001
From: Ondrej Mirtes <ondrej@mirtes.cz>
Date: Tue, 10 Jan 2023 15:09:16 +0100
Subject: [PATCH] Last elseif can be exhaustive and no else branch is not
 needed

---
 src/Analyser/NodeScopeResolver.php            |  2 +-
 .../Analyser/NodeScopeResolverTest.php        |  1 +
 .../Analyser/data/always-true-elseif.php      | 28 +++++++++++++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 tests/PHPStan/Analyser/data/always-true-elseif.php

diff --git a/src/Analyser/NodeScopeResolver.php b/src/Analyser/NodeScopeResolver.php
index 739fe702a1..172fce03d8 100644
--- a/src/Analyser/NodeScopeResolver.php
+++ b/src/Analyser/NodeScopeResolver.php
@@ -784,7 +784,7 @@ private function processStmtNode(
 			}
 
 			if ($stmt->else === null) {
-				if (!$ifAlwaysTrue) {
+				if (!$ifAlwaysTrue && !$lastElseIfConditionIsTrue) {
 					$finalScope = $scope->mergeWith($finalScope);
 					$alwaysTerminating = false;
 				}
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
index 34798c2deb..6fb2ec882e 100644
--- a/tests/PHPStan/Analyser/NodeScopeResolverTest.php
+++ b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -1165,6 +1165,7 @@ public function dataFileAsserts(): iterable
 		if (PHP_VERSION_ID >= 80000) {
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/pathinfo-php8.php');
 		}
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/always-true-elseif.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/pathinfo.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8568.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/../Rules/DeadCode/data/bug-8620.php');
diff --git a/tests/PHPStan/Analyser/data/always-true-elseif.php b/tests/PHPStan/Analyser/data/always-true-elseif.php
new file mode 100644
index 0000000000..66b0788bf6
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/always-true-elseif.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace AlwaysTrueElseif;
+
+use PHPStan\TrinaryLogic;
+use function PHPStan\Testing\assertVariableCertainty;
+
+class Foo
+{
+
+	/**
+	 * @param 'a'|'b'|'c' $s
+	 * @return void
+	 */
+	public function doFoo(string $s): void
+	{
+		if ($s === 'a') {
+			$a = true;
+		} elseif ($s === 'b') {
+			$a = false;
+		} elseif ($s === 'c') {
+			$a = true;
+		}
+
+		assertVariableCertainty(TrinaryLogic::createYes(), $a);
+	}
+
+}