Infer non-falsy-string for the magic name property on the UnitEnum/BackedEnum interfaces

build/more-enum-adapter-errors.neon

@@ -36,3 +36,23 @@ parameters:
 			rawMessage: 'Parameter #2 $reflection of method PHPStan\Reflection\ClassReflectionFactory::create() expects ReflectionClass, PHPStan\BetterReflection\Reflection\Adapter\ReflectionClass|PHPStan\BetterReflection\Reflection\Adapter\ReflectionEnum given.'
 			count: 1
 			path: ../src/Analyser/NodeScopeResolver.php
+
+		-
+			rawMessage: 'Right side of || is always false.'
+			count: 1
+			path: ../src/Reflection/Php/PhpClassReflectionExtension.php
+
+		-
+			rawMessage: 'If condition is always true.'
+			count: 1
+			path: ../src/Reflection/Php/PhpClassReflectionExtension.php
+
+		-
+			rawMessage: 'Result of && is always false.'
+			count: 1
+			path: ../src/Reflection/Php/PhpClassReflectionExtension.php
+
+		-
+			rawMessage: 'Strict comparison using === between class-string and ''UnitEnum'' will always evaluate to false.'
+			count: 1
+			path: ../src/Reflection/Php/PhpClassReflectionExtension.php

src/Reflection/Php/PhpClassReflectionExtension.php

@@ -15,6 +15,7 @@
 use PHPStan\BetterReflection\Reflection\Adapter\ReflectionParameter;
 use PHPStan\BetterReflection\Reflection\Adapter\ReflectionProperty;
 use PHPStan\Parser\Parser;
+use PHPStan\Php\PhpVersion;
 use PHPStan\PhpDoc\PhpDocInheritanceResolver;
 use PHPStan\PhpDoc\ResolvedPhpDocBlock;
 use PHPStan\PhpDoc\StubPhpDocProvider;
@@ -38,6 +39,7 @@
 use PHPStan\Reflection\SignatureMap\SignatureMapProvider;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
+use PHPStan\Type\Accessory\AccessoryNonFalsyStringType;
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\Constant\ConstantArrayTypeBuilder;
 use PHPStan\Type\Constant\ConstantStringType;
@@ -51,6 +53,7 @@
 use PHPStan\Type\Generic\TemplateTypeVariance;
 use PHPStan\Type\MixedType;
 use PHPStan\Type\NeverType;
+use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
 use PHPStan\Type\TypehintHelper;
@@ -103,6 +106,7 @@ public function __construct(
 		private AttributeReflectionFactory $attributeReflectionFactory,
 		private ParameterAllowedConstantsMapProvider $allowedConstantsMapProvider,
 		private bool $inferPrivatePropertyTypeFromConstructor,
+		private PhpVersion $phpVersion,
 	)
 	{
 	}
@@ -202,32 +206,42 @@ private function createProperty(
 			));
 		}
 
-		if ($declaringClassReflection->isEnum()) {
+		$isUnitEnumInterfaceNameProperty = $this->phpVersion->supportsEnums()
+			&& $propertyName === 'name'
+			&& $declaringClassName === 'UnitEnum';
+
+		if ($declaringClassReflection->isEnum() || $isUnitEnumInterfaceNameProperty) {
 			if (
 				$propertyName === 'name'
 				|| ($declaringClassReflection->isBackedEnum() && $propertyName === 'value')
 			) {
-				$types = [];
-				foreach ($classReflection->getEnumCases() as $name => $case) {
-					if ($propertyName === 'name') {
-						$types[] = new ConstantStringType($name);
-						continue;
-					}
+				if ($declaringClassReflection->isEnum()) {
+					$types = [];
+					foreach ($classReflection->getEnumCases() as $name => $case) {
+						if ($propertyName === 'name') {
+							$types[] = new ConstantStringType($name);
+							continue;
+						}
+
+						$value = $case->getBackingValueType();
+						if ($value === null) {
+							throw new ShouldNotHappenException();
+						}
 
-					$value = $case->getBackingValueType();
-					if ($value === null) {
-						throw new ShouldNotHappenException();
+						$types[] = $value;
 					}
 
-					$types[] = $value;
+					$phpDocType = TypeCombinator::union(...$types);
+					$nativeType = new MixedType();
+				} else {
+					$phpDocType = TypeCombinator::intersect(new StringType(), new AccessoryNonFalsyStringType());
+					$nativeType = new StringType();
 				}
 
-				$phpDocType = TypeCombinator::union(...$types);
-
 				return new PhpPropertyReflection(
 					$declaringClassReflection,
 					null,
-					new MixedType(),
+					$nativeType,
 					$phpDocType,
 					$phpDocType,
 					$classReflection->getNativeReflection()->getProperty($propertyName),

tests/PHPStan/Analyser/nsrt/bug-14839.php

@@ -0,0 +1,43 @@
+<?php // lint >= 8.1
+
+declare(strict_types=1);
+
+namespace Bug14839;
+
+use function PHPStan\Testing\assertType;
+
+enum Foo
+{
+
+	case A;
+	case B;
+
+}
+
+enum Bar: string
+{
+
+	case A = 'a';
+	case B = 'b';
+
+}
+
+function test(Foo $foo, Bar $bar, \UnitEnum $u, \BackedEnum $b): void
+{
+	assertType("'A'|'B'", $foo->name);
+	assertType("'A'|'B'", $bar->name);
+	assertType("'a'|'b'", $bar->value);
+	assertType('non-falsy-string', $u->name);
+	assertType('non-falsy-string', $b->name);
+	// `value` stays as its native `int|string`: unlike a case name, a backing value may legitimately be "" or "0".
+	assertType('int|string', $b->value);
+}
+
+/**
+ * @template T of \UnitEnum
+ * @param T $enum
+ */
+function testTemplate($enum): void
+{
+	assertType('non-falsy-string', $enum->name);
+}