Fix ClassConstantAccessType to return mixed for untyped constants on non-final classes

When static::CONST is used and the constant has no native type or PHPDoc type,
and neither the class nor the constant is final, return mixed instead of the
literal value — since a subclass could override the constant with any value.

Also unified the logic to use getObjectClassReflections() instead of
instanceof StaticType, so it works for both unresolved StaticType and
resolved ObjectType (e.g., FooBar $foo where $foo could be a subclass).

Co-authored-by: Ondřej Mirtes <ondrejmirtes@users.noreply.github.com>

Author: github-actions[bot]

src/Type/ClassConstantAccessType.php

@@ -57,16 +57,15 @@ protected function getResult(): Type
 
 		$constantReflection = $this->type->getConstant($this->constantName);
 
-		if (
-			$this->type instanceof StaticType
-			&& !$this->type->getClassReflection()->isFinal()
-			&& !$constantReflection->isFinal()
-		) {
-			if ($constantReflection->hasNativeType() || $constantReflection->hasPhpDocType()) {
-				return $constantReflection->getValueType();
+		if (!$constantReflection->isFinal()) {
+			$classReflections = $this->type->getObjectClassReflections();
+			if (count($classReflections) === 1 && !$classReflections[0]->isFinal()) {
+				if ($constantReflection->hasNativeType() || $constantReflection->hasPhpDocType()) {
+					return $constantReflection->getValueType();
+				}
+
+				return new MixedType();
 			}
-
-			return new MixedType();
 		}
 
 		return $constantReflection->getValueType();

tests/PHPStan/Analyser/nsrt/bug-13828.php

@@ -22,8 +22,8 @@ class BarBaz extends FooBar
 
 function test(FooBar $foo, BarBaz $bar): void
 {
-	assertType("'foo'", $foo->test());
-	assertType("'bar'", $bar->test());
+	assertType('mixed', $foo->test());
+	assertType('mixed', $bar->test());
 }
 
 final class FinalFoo
@@ -146,5 +146,5 @@ public function test(): string
 
 function testUntypedConstant(WithUntypedConstant $foo): void
 {
-	assertType("'foo'", $foo->test());
+	assertType('mixed', $foo->test());
 }