fix trait import name resolution

src/Resolver/NameResolutionTrait.php

@@ -104,6 +104,15 @@ trait NameResolutionTrait
             if (isset($this->zendTypeMap[strtolower($typeName)]) || in_array(strtolower($typeName), ['self', 'static', 'parent'], true)) {
                 return $type;
             }
+            // NameResolver has already applied the declaring file's namespace
+            // imports. Keep that canonical identity when a trait signature is
+            // copied into its consuming class. In particular, after
+            // `use X\X; use X\Y;`, resolving Y produces X\Y; feeding that string
+            // through the import table again would incorrectly produce X\X\Y.
+            $resolvedName = $type->getAttribute('resolvedName');
+            if ($resolvedName instanceof Node\Name\FullyQualified) {
+                return new Node\Name\FullyQualified($resolvedName->toString(), $type->getAttributes());
+            }
             $resolved = $typeName;
             $firstSegment = explode('\\', $typeName, 2)[0];
             $hasImportedPrefix = $this->getClassImportAlias($firstSegment) !== null;

tests/compiler/namespace/use-import-root-semantics.phpt

@@ -0,0 +1,40 @@
+--TEST--
+Namespace imports are rooted while qualified name uses still expand their first alias segment
+--FILE--
+<?php
+namespace Carbon {
+    interface CarbonInterface {}
+
+    class Carbon implements CarbonInterface {}
+}
+
+namespace App {
+    use Carbon\Carbon;
+    use Carbon\CarbonInterface;
+    use Carbon\{Carbon as GroupedCarbon, CarbonInterface as GroupedInterface};
+
+    function importedNames(): array {
+        return [
+            Carbon::class,
+            CarbonInterface::class,
+            GroupedCarbon::class,
+            GroupedInterface::class,
+            Carbon\CarbonInterface::class,
+        ];
+    }
+}
+
+namespace {
+    function main(): void {
+        foreach (App\importedNames() as $name) {
+            echo $name, "\n";
+        }
+    }
+}
+?>
+--EXPECT--
+Carbon\Carbon
+Carbon\CarbonInterface
+Carbon\Carbon
+Carbon\CarbonInterface
+Carbon\Carbon\CarbonInterface

tests/compiler/trait/trait-import-same-as-namespace.phpt

@@ -0,0 +1,88 @@
+--TEST--
+Trait types retain rooted imports when an imported class has the same short name as its namespace
+--FILE--
+<?php
+namespace App {
+    use Carbon\Carbon;
+    use Carbon\CarbonInterface;
+
+    trait Checker {
+        public CarbonInterface $value;
+
+        public function accept(CarbonInterface $value): CarbonInterface {
+            $this->value = $value;
+            return $value;
+        }
+
+        public function acceptNullable(?CarbonInterface $value): ?CarbonInterface {
+            return $value;
+        }
+
+        public function check(mixed $value): bool {
+            return $value instanceof CarbonInterface;
+        }
+
+        public function make(): CarbonInterface {
+            return Carbon::parse('value');
+        }
+
+        public function importedNames(): array {
+            return [
+                Carbon::class,
+                CarbonInterface::class,
+                Carbon\CarbonInterface::class,
+            ];
+        }
+    }
+
+    class Example {
+        use Checker;
+    }
+}
+
+namespace {
+    function main(): void {
+        eval(<<<'PHP'
+namespace Carbon;
+interface CarbonInterface {}
+class Carbon implements CarbonInterface {
+    public static function parse(string $value): CarbonInterface {
+        return new self();
+    }
+}
+PHP);
+
+        $example = new App\Example();
+        $value = new Carbon\Carbon();
+
+        var_dump($example->accept($value) === $value);
+        var_dump($example->acceptNullable($value) === $value);
+        var_dump($example->acceptNullable(null));
+        var_dump($example->check($value));
+        var_dump($example->make() instanceof Carbon\CarbonInterface);
+
+        $method = new ReflectionMethod(App\Example::class, 'accept');
+        echo $method->getParameters()[0]->getType()->getName(), "\n";
+        echo $method->getReturnType()->getName(), "\n";
+
+        $property = new ReflectionProperty(App\Example::class, 'value');
+        echo $property->getType()->getName(), "\n";
+
+        foreach ($example->importedNames() as $name) {
+            echo $name, "\n";
+        }
+    }
+}
+?>
+--EXPECT--
+bool(true)
+bool(true)
+NULL
+bool(true)
+bool(true)
+Carbon\CarbonInterface
+Carbon\CarbonInterface
+Carbon\CarbonInterface
+Carbon\Carbon
+Carbon\CarbonInterface
+Carbon\Carbon\CarbonInterface