diff --git a/src/Analyser/ExprHandler/FuncCallHandler.php b/src/Analyser/ExprHandler/FuncCallHandler.php
index d28a3225de..fa39b3cd59 100644
--- a/src/Analyser/ExprHandler/FuncCallHandler.php
+++ b/src/Analyser/ExprHandler/FuncCallHandler.php
@@ -936,7 +936,9 @@ public function specifyTypes(TypeSpecifier $typeSpecifier, Scope $scope, Expr $e
 					));
 					$specifiedTypes = $typeSpecifier->specifyTypesFromAsserts($context, $expr, $asserts, $parametersAcceptor, $scope);
 					if ($specifiedTypes !== null) {
-						return $specifiedTypes;
+						return $specifiedTypes
+							->unionWith($typeSpecifier->handleDefaultTruthyOrFalseyContext($context, $expr, $scope))
+							->setRootExpr($specifiedTypes->getRootExpr());
 					}
 				}
 			}
diff --git a/src/Rules/Comparison/ImpossibleCheckTypeHelper.php b/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
index 55138f3de6..f5599c6394 100644
--- a/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
+++ b/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
@@ -350,6 +350,13 @@ private function getSpecifiedType(
 			}
 		}
 		foreach ($sureTypes as $sureType) {
+			if ($sureType[0] === $node) {
+				// The check's own truthiness carries no information about
+				// whether the check is redundant; the informative narrowing
+				// lives in the argument entries.
+				continue;
+			}
+
 			if (self::isSpecified($typeSpecifierScope, $node, $sureType[0])) {
 				$results[] = TrinaryLogic::createMaybe();
 				continue;
@@ -384,6 +391,13 @@ private function getSpecifiedType(
 		}
 
 		foreach ($sureNotTypes as $sureNotType) {
+			if ($sureNotType[0] === $node) {
+				// The check's own truthiness carries no information about
+				// whether the check is redundant; the informative narrowing
+				// lives in the argument entries.
+				continue;
+			}
+
 			if (self::isSpecified($typeSpecifierScope, $node, $sureNotType[0])) {
 				$results[] = TrinaryLogic::createMaybe();
 				continue;
diff --git a/src/Rules/Keywords/RequireFileExistsRule.php b/src/Rules/Keywords/RequireFileExistsRule.php
index 674fc815c1..9e5fa1eb57 100644
--- a/src/Rules/Keywords/RequireFileExistsRule.php
+++ b/src/Rules/Keywords/RequireFileExistsRule.php
@@ -33,6 +33,19 @@
 final class RequireFileExistsRule implements Rule
 {
 
+	/**
+	 * Functions that, when they return true, guarantee the path exists on the
+	 * filesystem, so guarding a require/include with them suppresses the error.
+	 */
+	private const FILE_EXISTENCE_FUNCTIONS = [
+		'file_exists',
+		'is_file',
+		'is_readable',
+		'is_writable',
+		'is_writeable',
+		'is_executable',
+	];
+
 	public function __construct(
 		#[AutowiredParameter]
 		private string $currentWorkingDirectory,
@@ -183,7 +196,7 @@ private function resolveFilePaths(Expr $expr, Scope $scope, bool &$magicDirFallb
 
 	private function isInFileExists(Include_ $node, Scope $scope): bool
 	{
-		foreach (['file_exists', 'is_file'] as $funcName) {
+		foreach (self::FILE_EXISTENCE_FUNCTIONS as $funcName) {
 			$expr = new FuncCall(new FullyQualified($funcName), [
 				new Arg($node->expr),
 			]);
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14829.php b/tests/PHPStan/Analyser/nsrt/bug-14829.php
new file mode 100644
index 0000000000..381a638272
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14829.php
@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14829;
+
+use function PHPStan\Testing\assertType;
+
+function testFunction(string $path): void
+{
+	// is_readable() has @phpstan-assert-if-true in stubs/file.stub
+	if (is_readable($path)) {
+		assertType('true', is_readable($path));
+		assertType('non-empty-string', $path);
+	}
+
+	if (!is_readable($path)) {
+		return;
+	}
+	assertType('true', is_readable($path));
+}
diff --git a/tests/PHPStan/Rules/Keywords/data/include-in-file-exists.php b/tests/PHPStan/Rules/Keywords/data/include-in-file-exists.php
index f3b1e22633..a650a42e63 100644
--- a/tests/PHPStan/Rules/Keywords/data/include-in-file-exists.php
+++ b/tests/PHPStan/Rules/Keywords/data/include-in-file-exists.php
@@ -8,6 +8,22 @@
 	require __DIR__ . '/../vendor/autoload.php';
 }
 
+if (is_readable(__DIR__ . '/../vendor/autoload.php')) {
+	require __DIR__ . '/../vendor/autoload.php';
+}
+
+if (is_writable(__DIR__ . '/../vendor/autoload.php')) {
+	require __DIR__ . '/../vendor/autoload.php';
+}
+
+if (is_writeable(__DIR__ . '/../vendor/autoload.php')) {
+	require __DIR__ . '/../vendor/autoload.php';
+}
+
+if (is_executable(__DIR__ . '/../vendor/autoload.php')) {
+	require __DIR__ . '/../vendor/autoload.php';
+}
+
 foreach ([__DIR__ . '/../../autoload.php', __DIR__ . '/../autoload.php', __DIR__ . '/vendor/autoload.php'] as $file) {
 	if (file_exists($file)) {
 		require $file;