Narrow ReflectionEnum::getBackingType() after ReflectionEnum::isBacked()

Author: staabm

src/Reflection/ClassReflection.php

@@ -660,12 +660,7 @@ public function getBackedEnumType(): ?Type
 			return null;
 		}
 
-		$reflectionType = $this->reflection->getBackingType();
-		if ($reflectionType === null) {
-			return null;
-		}
-
-		return TypehintHelper::decideTypeFromReflection($reflectionType);
+		return TypehintHelper::decideTypeFromReflection($this->reflection->getBackingType());
 	}
 
 	public function hasEnumCase(string $name): bool

stubs/ReflectionEnum.stub

@@ -20,6 +20,7 @@ class ReflectionEnum extends ReflectionClass
 
 	/**
 	 * @phpstan-assert-if-true self<BackedEnum> $this
+	 * @phpstan-assert-if-true !null $this->getBackingType()
 	 */
 	public function isBacked(): bool {}
 

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -256,6 +256,11 @@ public function dataFileAsserts(): iterable
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-9734.php');
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/enum-reflection.php');
 		}
+		if (PHP_VERSION_ID >= 80200) {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/enum-reflection-php82.php');
+		} elseif (PHP_VERSION_ID >= 80100) {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/enum-reflection-php81.php');
+		}
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/match-expr.php');
 

tests/PHPStan/Analyser/data/enum-reflection-php81.php

@@ -0,0 +1,23 @@
+<?php // lint >= 8.1
+
+namespace EnumReflection81;
+
+use ReflectionEnum;
+use ReflectionEnumBackedCase;
+use ReflectionEnumUnitCase;
+use function PHPStan\Testing\assertType;
+
+enum Foo: int
+{
+
+	case FOO = 1;
+	case BAR = 2;
+}
+
+function testNarrowGetBackingTypeAfterIsBacked() {
+	$r = new ReflectionEnum(Foo::class);
+	assertType('ReflectionType|null', $r->getBackingType());
+	if ($r->isBacked()) {
+		assertType('ReflectionType', $r->getBackingType());
+	}
+}

tests/PHPStan/Analyser/data/enum-reflection-php82.php

@@ -0,0 +1,23 @@
+<?php // lint >= 8.1
+
+namespace EnumReflection82;
+
+use ReflectionEnum;
+use ReflectionEnumBackedCase;
+use ReflectionEnumUnitCase;
+use function PHPStan\Testing\assertType;
+
+enum Foo: int
+{
+
+	case FOO = 1;
+	case BAR = 2;
+}
+
+function testNarrowGetBackingTypeAfterIsBacked() {
+	$r = new ReflectionEnum(Foo::class);
+	assertType('ReflectionNamedType|null', $r->getBackingType());
+	if ($r->isBacked()) {
+		assertType('ReflectionNamedType', $r->getBackingType());
+	}
+}