fix(trait): preserve nested namespace context, fix gh-38

src/Translator.php

@@ -3107,8 +3107,12 @@ CODE;
                 /** @var Node\Stmt\Trait_ $traitAst */
                 $traitAst = $this->cloneAstNode($traitDef->trait);
                 // Recursively flatten traits used by this trait before copying
-                // its members into the final class.
-                $this->composeTraitAst($traitAst, new Node\Name($traitFullName));
+                // its members into the final class. The nested TraitUse nodes
+                // must be resolved in the lexical context of the trait being
+                // expanded, not in the context of its eventual consumer.
+                $this->withTraitNameContext($traitFullName, function () use ($traitAst, $traitFullName): void {
+                    $this->composeTraitAst($traitAst, new Node\Name($traitFullName));
+                });
                 $traitStmts = $traitAst->stmts;
                 $aliasStmts = [];
                 foreach ($traitStmts as $k1 => $traitStmt) {

tests/compiler/trait/nested-trait-import-context.phpt

@@ -0,0 +1,49 @@
+--TEST--
+Nested trait uses retain import aliases through multiple composition levels
+--FILE--
+<?php
+namespace Issue38\Library {
+    trait Greeting {
+        public function hello(): string {
+            return 'imported';
+        }
+    }
+}
+
+namespace Issue38\Template {
+    use Issue38\Library\Greeting as ImportedGreeting;
+
+    trait InnerWrapper {
+        use ImportedGreeting {
+            hello as protected importedHello;
+        }
+
+        public function wrapped(): string {
+            return '[' . $this->importedHello() . ']';
+        }
+    }
+
+    trait OuterWrapper {
+        use InnerWrapper;
+    }
+}
+
+namespace Issue38\Consumer {
+    use Issue38\Template\OuterWrapper as ImportedWrapper;
+
+    class Example {
+        use ImportedWrapper;
+    }
+}
+
+namespace {
+    function main(): void {
+        $example = new Issue38\Consumer\Example();
+        echo $example->hello(), "\n";
+        echo $example->wrapped(), "\n";
+    }
+}
+?>
+--EXPECT--
+imported
+[imported]

tests/compiler/trait/nested-trait-namespace-context.phpt

@@ -0,0 +1,28 @@
+--TEST--
+Nested trait uses resolve unqualified names in the declaring namespace
+--FILE--
+<?php
+namespace Issue38\SameNamespace {
+    trait Greeting {
+        public function hello(): string {
+            return 'hi';
+        }
+    }
+
+    trait GreetingWrapper {
+        use Greeting;
+    }
+
+    class Example {
+        use GreetingWrapper;
+    }
+}
+
+namespace {
+    function main(): void {
+        echo (new Issue38\SameNamespace\Example())->hello(), "\n";
+    }
+}
+?>
+--EXPECT--
+hi