PHP does not cache is_dir() and similar function values for nonexistent files

Author: ondrejmirtes

src/Analyser/MutatingScope.php

@@ -3477,6 +3477,17 @@ public function specifyExpressionType(Expr $expr, Type $type, ?Type $nativeType
 			}
 		}
 
+		if ($expr instanceof FuncCall && $expr->name instanceof Name && $type instanceof ConstantBooleanType && !$type->getValue()) {
+			$functionName = $this->reflectionProvider->resolveFunctionName($expr->name, $this);
+			if ($functionName !== null && in_array(strtolower($functionName), [
+				'is_dir',
+				'is_file',
+				'file_exists',
+			], true)) {
+				return $this;
+			}
+		}
+
 		return $scope->addMoreSpecificTypes([
 			$exprString => $type,
 		]);

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -388,6 +388,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4879.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4820.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4822.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4816.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-4816.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Bug4816;
+
+use function PHPStan\Testing\assertType;
+
+function (): void {
+	if (is_dir('foo')) {
+		assertType('true', is_dir('foo'));
+		assertType('bool', is_dir('bar'));
+
+		clearstatcache();
+
+		assertType('bool', is_dir('foo'));
+		assertType('bool', is_dir('bar'));
+	}
+};
+
+function (): void {
+	if (!is_dir('foo')) {
+		assertType('bool', is_dir('foo'));
+		assertType('bool', is_dir('bar'));
+	}
+};
+
+function (): void {
+	if (!is_dir('foo')) {
+		return;
+	}
+
+	assertType('true', is_dir('foo'));
+	assertType('bool', is_dir('bar'));
+
+	clearstatcache();
+
+	assertType('bool', is_dir('foo'));
+	assertType('bool', is_dir('bar'));
+};
+
+function (): void {
+	if (is_dir('foo')) {
+		return;
+	}
+
+	assertType('bool', is_dir('foo'));
+	assertType('bool', is_dir('bar'));
+};