Language: trait abstract residuals fatal at DECLARE after prior stmts (#25912)

lib/Compiler.php

@@ -2170,7 +2170,8 @@ protected function compileOps(array $ops, Block $block): void {
         // Interfaces before classes so same-file `class C implements I` / later `interface I`
         // resolves at DECLARE_CLASS like Zend early-binding (#25624).
         // Enums stay in source order so enum_exists() before declaration matches Zend (#5013).
-        // Serializable / forbidden-implements stay in source order for DECLARE side effects (#18781, #25109).
+        // Serializable / forbidden-implements / trait-use stay in source order for DECLARE
+        // side effects (#18781, #25109, #25912).
         foreach ($ops as $child) {
             if ($child instanceof Op\Stmt\Interface_) {
                 $block->addOpCode($this->compileInterface($child, $block));
@@ -6926,6 +6927,7 @@ protected function defersRuntimeInterfaceImplementationCheck(Op\Stmt\ClassLike $
      * - Forbidden implements (DateTimeInterface / reserved): fatals at DECLARE (#18781)
      * - Serializable: E_DEPRECATED + class_exists timing match Zend (#22000, #25109)
      * - Any implements: DECLARE must run after prior spl_autoload_register (#25624)
+     * - Trait use: abstract residuals / trait bind fatals at DECLARE after prior stmts (#25912)
      */
     protected function requiresSourceOrderClassRegistration(Op\Stmt\ClassLike $class): bool
     {
@@ -6937,11 +6939,31 @@ protected function requiresSourceOrderClassRegistration(Op\Stmt\ClassLike $class
             return true;
         }
 
+        // Keep trait-using classes in source order so preceding opcodes (echo, etc.) run
+        // before zend_verify_abstract_class / trait bind fatals (#25912).
+        if ($class instanceof Op\Stmt\Class_ && $this->classDeclaresTraitUse($class)) {
+            return true;
+        }
+
         // Keep implements classes in source order so autoload callbacks registered above
         // the declaration are visible (Zend early-binds types, not user autoload timing).
         return $class instanceof Op\Stmt\Class_ && [] !== $class->implements;
     }
 
+    /**
+     * True when the class body contains a `use Trait` statement (#25912).
+     */
+    protected function classDeclaresTraitUse(Op\Stmt\Class_ $class): bool
+    {
+        foreach ($class->stmts->children as $member) {
+            if ($member instanceof Op\Stmt\TraitUse) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     protected function staticNameFromOperand(Operand $op): ?string
     {
         if ($op instanceof Operand\Literal && is_string($op->value)) {

lib/VM.php

@@ -7922,7 +7922,11 @@ function () use ($frame, $op, $arg1, $strict, $arraySpec, $vmContext): void {
                             'parentName' => $parentName,
                         ];
                     }
-                    $this->flushDeferredParentInheritance();
+                    try {
+                        $this->flushDeferredParentInheritance($frame);
+                    } catch (\CompileError $e) {
+                        $this->raiseClassDeclareCompileFatal($e, $frame);
+                    }
                     $this->flushDeferredTraitUses($frame);
                     $this->flushDeferredClassConstants();
                     break;
@@ -9702,7 +9706,9 @@ function () use ($frame, $op, $arg1, $strict, $arraySpec, $vmContext): void {
         }
         if ([] !== $this->context->deferredParentInheritance) {
             try {
-                $this->finalizeDeferredParentInheritance();
+                $this->finalizeDeferredParentInheritance($frame);
+            } catch (\CompileError $deferredCompileError) {
+                $this->raiseClassDeclareCompileFatal($deferredCompileError, $frame);
             } catch (\Error $deferredParentError) {
                 $catchFrame = $this->dispatchVmError($deferredParentError->getMessage(), $frame);
                 if (null !== $catchFrame) {
@@ -17605,7 +17611,7 @@ protected function flushDeferredTraitUses(?Frame $warningFrame = null): void
         $this->context->deferredTraitUses = $remaining;
     }
 
-    protected function flushDeferredParentInheritance(): void
+    protected function flushDeferredParentInheritance(?Frame $frame = null): void
     {
         if ([] === $this->context->deferredParentInheritance) {
             return;
@@ -17627,14 +17633,14 @@ protected function flushDeferredParentInheritance(): void
             $this->assertAllowedBySealedParents($entry->name, $entry->parentLc, $entry->interfaces);
             $this->inheritFromParent($entry);
             $this->linkStaticPropertyHooks($entry);
-            VM\ClassValidator::finalizeClassDefinition($entry, $this->context);
+            VM\ClassValidator::finalizeClassDefinition($entry, $this->context, $frame);
         }
         $this->context->deferredParentInheritance = $remaining;
     }
 
-    protected function finalizeDeferredParentInheritance(): void
+    protected function finalizeDeferredParentInheritance(?Frame $frame = null): void
     {
-        $this->flushDeferredParentInheritance();
+        $this->flushDeferredParentInheritance($frame);
         if ([] === $this->context->deferredParentInheritance) {
             return;
         }

lib/VM/ClassValidator.php

@@ -137,7 +137,8 @@ private static function validateInterfaceImplementation(ClassEntry $entry, Conte
         [$ifaceLc, $method] = $missing[0];
         $ifaceName = $context->classes[$ifaceLc]->name ?? $ifaceLc;
 
-        throw new \LogicException(
+        // php-src: zend_verify_abstract_class — E_COMPILE_ERROR at DECLARE (#25912).
+        throw new \CompileError(
             "Class {$entry->name} contains {$count} abstract method"
             .(1 === $count ? '' : 's')
             ." and must therefore be declared abstract or implement the remaining methods ({$ifaceName}::{$method})"
@@ -153,7 +154,8 @@ private static function validateAbstractMethodsResolved(ClassEntry $entry): void
         $count = count($entry->abstractMethods);
         $first = array_key_first($entry->abstractMethods);
 
-        throw new \LogicException(
+        // php-src: zend_verify_abstract_class — E_COMPILE_ERROR at DECLARE (#25912).
+        throw new \CompileError(
             "Class {$entry->name} contains {$count} abstract method"
             .(1 === $count ? '' : 's')
             ." and must therefore be declared abstract or implement the remaining methods ({$entry->name}::{$first})"
@@ -173,7 +175,8 @@ private static function validateAbstractPropertyHooksResolved(ClassEntry $entry,
             $missing
         ));
 
-        throw new \LogicException(
+        // php-src: zend_verify_abstract_class — E_COMPILE_ERROR at DECLARE (#25912).
+        throw new \CompileError(
             "Class {$entry->name} contains {$count} abstract method"
             .(1 === $count ? '' : 's')
             ." and must therefore be declared abstract or implement the remaining methods ({$list})"

test/compliance/cases/language/trait_abstract_unimplemented_fatal.phpt

@@ -0,0 +1,20 @@
+--TEST--
+Language: trait abstract method unimplemented — DECLARE-time fatal after prior stmts (#25912, Zend/zend_inheritance.c)
+--INI--
+display_errors=1
+--FILE--
+<?php
+trait TAbs {
+    abstract public function f();
+}
+echo "before\n";
+class C {
+    use TAbs;
+}
+echo "accepted\n";
+--EXPECTF--
+before
+
+Fatal error: Class C contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (C::f) in %s on line %d
+--EXPECT_EXIT--
+255

test/repro/maintainer_gap_trait_abstract_unimplemented_fatal.php

@@ -0,0 +1,22 @@
+<?php
+/**
+ * Issue #25912 — concrete class using trait with unimplemented abstract method.
+ *
+ * Zend runs preceding statements, then E_COMPILE_ERROR at class DECLARE
+ * (Zend/zend_compile.c / zend_inheritance.c zend_verify_abstract_class).
+ *
+ * Expected (php-src-strict):
+ *   stdout: before
+ *   stderr: PHP Fatal error:  Class C contains 1 abstract method… (C::f)
+ *   exit 255; no "accepted"
+ */
+trait TAbs
+{
+    abstract public function f();
+}
+echo "before\n";
+class C
+{
+    use TAbs;
+}
+echo "accepted\n";

test/unit/TraitAbstractUnimplementedFatalTest.php

@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PHPCompiler\Test\Unit;
+
+use PHPCompiler\Runtime;
+use PHPCompiler\VM\ScriptExit;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers issue #25912
+ *
+ * php-src: Zend/zend_inheritance.c — zend_verify_abstract_class at class DECLARE.
+ */
+final class TraitAbstractUnimplementedFatalTest extends TestCase
+{
+    public function testPrecedingEchoRunsThenCompileFatal(): void
+    {
+        $runtime = new Runtime();
+        $code = <<<'PHP'
+<?php
+trait TAbs {
+    abstract public function f();
+}
+echo "before\n";
+class C {
+    use TAbs;
+}
+echo "accepted\n";
+PHP;
+        $block = $runtime->parseAndCompile($code, 'trait_abstract_unimpl.php');
+        $this->assertNotNull($block);
+
+        ob_start();
+        try {
+            // bubbleUncaught=false — ScriptExit like bin/vm.php CLI (#25912).
+            $runtime->run($block, false);
+            ob_end_clean();
+            $this->fail('Expected ScriptExit for unimplemented trait abstract method');
+        } catch (\CompileError $e) {
+            $out = ob_get_clean();
+            $this->assertStringContainsString('before', (string) $out);
+            $this->assertStringNotContainsString('accepted', (string) $out);
+            $this->assertStringContainsString('Class C contains 1 abstract method', $e->getMessage());
+            $this->assertStringContainsString('(C::f)', $e->getMessage());
+        } catch (ScriptExit $e) {
+            $out = ob_get_clean();
+            $this->assertSame(255, $e->status);
+            $this->assertStringContainsString('before', (string) $out);
+            $this->assertStringNotContainsString('accepted', (string) $out);
+            // Fatal body goes to stderr as "PHP Fatal error:" (display_errors=0); CLI repro covers that.
+        }
+    }
+
+    public function testImplementedTraitAbstractCompilesAndRuns(): void
+    {
+        $runtime = new Runtime();
+        $code = <<<'PHP'
+<?php
+trait TAbs {
+    abstract public function f(): int;
+}
+class C {
+    use TAbs;
+    public function f(): int { return 7; }
+}
+echo C::class, ":", (new C())->f(), "\n";
+PHP;
+        ob_start();
+        $runtime->run($runtime->parseAndCompile($code, 'trait_abstract_ok.php'));
+        $this->assertSame("C:7\n", ob_get_clean());
+    }
+}