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/Analyser/ExprHandler/MethodCallHandler.php b/src/Analyser/ExprHandler/MethodCallHandler.php
index 77f5969ae7..1f661f5a98 100644
--- a/src/Analyser/ExprHandler/MethodCallHandler.php
+++ b/src/Analyser/ExprHandler/MethodCallHandler.php
@@ -328,7 +328,9 @@ 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/Analyser/ExprHandler/StaticCallHandler.php b/src/Analyser/ExprHandler/StaticCallHandler.php
index e24683ac8f..872fac5c79 100644
--- a/src/Analyser/ExprHandler/StaticCallHandler.php
+++ b/src/Analyser/ExprHandler/StaticCallHandler.php
@@ -429,7 +429,9 @@ 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..99fcc8c4f4
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14829.php
@@ -0,0 +1,52 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14829;
+
+use function PHPStan\Testing\assertType;
+
+class Checker
+{
+
+	/** @phpstan-assert-if-true =non-empty-string $path */
+	public function isReadable(string $path): bool
+	{
+		return $path !== '';
+	}
+
+	/** @phpstan-assert-if-true =non-empty-string $path */
+	public static function staticIsReadable(string $path): bool
+	{
+		return $path !== '';
+	}
+
+}
+
+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));
+}
+
+function testMethod(Checker $c, string $path): void
+{
+	if ($c->isReadable($path)) {
+		assertType('true', $c->isReadable($path));
+		assertType('non-empty-string', $path);
+	}
+}
+
+function testStaticMethod(string $path): void
+{
+	if (Checker::staticIsReadable($path)) {
+		assertType('true', Checker::staticIsReadable($path));
+		assertType('non-empty-string', $path);
+	}
+}
diff --git a/tests/PHPStan/Rules/Comparison/BooleanAndConstantConditionRuleTest.php b/tests/PHPStan/Rules/Comparison/BooleanAndConstantConditionRuleTest.php
index caaaf53050..6514f8619f 100644
--- a/tests/PHPStan/Rules/Comparison/BooleanAndConstantConditionRuleTest.php
+++ b/tests/PHPStan/Rules/Comparison/BooleanAndConstantConditionRuleTest.php
@@ -452,6 +452,17 @@ public function testBug8555(): void
 		$this->analyse([__DIR__ . '/data/bug-8555.php'], []);
 	}
 
+	public function testSelfContradiction(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/self-contradiction.php'], [
+			[
+				'Result of && is always false.',
+				25,
+			],
+		]);
+	}
+
 	#[RequiresPhp('>= 8.1.0')]
 	public function testBug14807(): void
 	{
diff --git a/tests/PHPStan/Rules/Comparison/data/self-contradiction.php b/tests/PHPStan/Rules/Comparison/data/self-contradiction.php
new file mode 100644
index 0000000000..47a56712ab
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/self-contradiction.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace SelfContradiction;
+
+use PhpParser\Node\Expr;
+use PhpParser\Node\Expr\BinaryOp\Identical;
+use PhpParser\Node\Expr\ClassConstFetch;
+use PhpParser\Node\Expr\ConstFetch;
+use PhpParser\Node\Scalar;
+
+class Foo {
+	/**
+	 * @phpstan-assert-if-true Scalar|ClassConstFetch|ConstFetch $node
+	 */
+	private static function isSubjectNode(Expr $node): bool
+	{
+		return $node instanceof Scalar || $node instanceof ClassConstFetch || $node instanceof ConstFetch;
+	}
+
+	/**
+	 * @return array{subject: Expr, value: Scalar|ClassConstFetch|ConstFetch}|null
+	 */
+	private function getSubjectAndValue(Identical $comparison): ?array
+	{
+		if (self::isSubjectNode($comparison->left) && !self::isSubjectNode($comparison->left)) {
+			return ['subject' => $comparison->right, 'value' => $comparison->left];
+		}
+
+		if (!self::isSubjectNode($comparison->left) && self::isSubjectNode($comparison->right)) {
+			return ['subject' => $comparison->left, 'value' => $comparison->right];
+		}
+
+		return null;
+	}
+}
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;