feat(parser): implement runtime constant resolution with namespace fallback

- Remove static constant lookup logic from parseConstFetch method
- Add support for unqualified constants in namespaces with runtime fallback mechanism
- Implement UnqualifiedInNamespace constant lookup strategy for proper PHP behavior
- Update test cases to verify runtime constant resolution works correctly
- Add comprehensive test coverage for namespace constant fallback scenarios
- Remove isValidDefineName validation in favor of direct string checking
- Support define() calls with namespaced and non-identifier constant names
- Add proper error handling for undefined constants in namespaces

phpunit/src/CompilerBaseApiTest.php

@@ -248,10 +248,40 @@ class CompilerBaseApiTest extends TestCase
             new \PhpParser\Node\Expr\ConstFetch(new \PhpParser\Node\Name('ROOT_PATH'))
         );
 
-        $this->assertStringStartsWith('php::constant(nullptr, ', $code);
+        $this->assertStringStartsWith('php::constant(', $code);
         $this->assertStringNotContainsString(ROOT_PATH, $code);
     }
 
+    public function testUnqualifiedRuntimeConstantUsesNamespaceFallback(): void
+    {
+        $this->setPropertyValue('namespace', 'App\\Worker');
+        $this->setPropertyValue('noLiteralStrings', true);
+
+        $code = $this->invokeMethod(
+            'parseConstFetch',
+            new \PhpParser\Node\Expr\ConstFetch(new \PhpParser\Node\Name('COMPOSER_PATH'))
+        );
+
+        $this->assertStringNotContainsString('php::fn::defined(', $code);
+        $this->assertStringContainsString('App\\\\Worker\\\\COMPOSER_PATH', $code);
+        $this->assertStringEndsWith(', php::ConstantLookup::UnqualifiedInNamespace)', $code);
+        $this->assertStringNotContainsString('php::constant(nullptr,', $code);
+    }
+
+    public function testQualifiedRuntimeConstantDoesNotUseGlobalFallback(): void
+    {
+        $this->setPropertyValue('namespace', 'App\\Worker');
+        $this->setPropertyValue('noLiteralStrings', true);
+
+        $code = $this->invokeMethod(
+            'parseConstFetch',
+            new \PhpParser\Node\Expr\ConstFetch(new \PhpParser\Node\Name('Config\\PATH'))
+        );
+
+        $this->assertStringNotContainsString('php::fn::defined(', $code);
+        $this->assertStringContainsString('App\\\\Worker\\\\Config\\\\PATH', $code);
+    }
+
     public function testDynamicallyDefinedConstantsAreNotInternalConstants(): void
     {
         $name = 'AOT_USER_DEFINE_' . str_replace('.', '_', uniqid('', true));

src/Optimizer/FuncCallOptimizer.php

@@ -724,7 +724,7 @@ trait FuncCallOptimizer
     protected function genDefine(string $n, Node\Expr\FuncCall $e, array $c): string|false
     {
         $arg = $e->args[0]->value;
-        if ($this->isScalarString($arg) && !$this->isValidDefineName($arg->value)) {
+        if ($this->isScalarString($arg) && str_contains($arg->value, '::')) {
             $this->fatalError($e, 'Invalid define name `' . $arg->value . '`');
         }
         $args = count($e->args) >= 3 ? 3 : 2;
@@ -844,8 +844,4 @@ trait FuncCallOptimizer
     // Utility
     // =========================================================================
 
-    protected function isValidDefineName(string $name): bool
-    {
-        return preg_match('/^(?!\d)[\p{L}_][\p{L}\p{N}_]*$/u', $name) === 1;
-    }
 }

src/Parser/ConstantExpressionTrait.php

@@ -24,21 +24,6 @@ trait ConstantExpressionTrait
         }
         $name = $this->parseIdentifier($expr->name);
         $name = ltrim($name, '\\');
-        if ($this->isNameExpr($expr->name) and $this->hasConstant($name)) {
-            return $this->getConstant($name);
-        }
-        if ($this->namespace and $this->isNameExpr($expr->name) and !$expr->name instanceof Node\Name\FullyQualified) {
-            $nsName = $this->namespace . '\\' . $name;
-            if ($this->hasConstant($nsName)) {
-                return $this->getConstant($nsName);
-            }
-        }
-        if ($this->isNameExpr($expr->name) and isset($this->useConstants[$name])) {
-            $importedName = $this->useConstants[$name];
-            if ($this->hasConstant($importedName)) {
-                return $this->getConstant($importedName);
-            }
-        }
         if (strcasecmp($name, 'null') === 0) {
             return self::VALUE_NULL;
         }
@@ -48,15 +33,6 @@ trait ConstantExpressionTrait
         if (strcasecmp($name, 'false') === 0) {
             return 'false';
         }
-        if ($name === 'PHP_EOL') {
-            return '"' . $this->escapeString(PHP_EOL) . '"';
-        }
-        if ($this->isInternalScalarConstant($name)) {
-            return $this->getInternalScalarConstantValue($name);
-        }
-        if ($scalar) {
-            return constant($expr->name);
-        }
         if ($this->isNameExpr($expr->name)) {
             if (str_contains($name, '::')) {
                 $ns = explode('::', $name)[0];
@@ -64,20 +40,49 @@ trait ConstantExpressionTrait
                 $ce = $this->getClassEntryPtr($fullName);
                 return Symbol::constant() . '(' . $ce . ', ' . $this->getLiteralString($ns[1]) . ')';
             }
-            if ($this->isInternalConstant($name)) {
-                return Symbol::constant() . '(' . $this->getLiteralString($name) . ')';
-            }
-            if (isset($this->useAliases[$name])) {
-                $name = $this->useAliases[$name];
-            } elseif (isset($this->useConstants[$name])) {
+
+            if (isset($this->useConstants[$name])) {
                 $name = $this->useConstants[$name];
+            } elseif ($expr->name->isUnqualified()) {
+                if ($this->namespace) {
+                    $namespacedName = $this->namespace . '\\' . $name;
+                    if ($this->hasConstant($namespacedName)) {
+                        return $this->getConstant($namespacedName);
+                    }
+
+                    // PHP resolves an unqualified constant in a namespace at
+                    // runtime: first Namespace\NAME, then the global NAME. AOT
+                    // cannot select only the namespaced spelling because a
+                    // define() call may execute before this fetch.
+                    return Symbol::constant() . '('
+                        . $this->getLiteralString($namespacedName)
+                        . ', php::ConstantLookup::UnqualifiedInNamespace)';
+                }
+                // A class import with the same alias does not affect a bare
+                // constant fetch. Only `use const` participates here.
+            } elseif ($expr->name instanceof Node\Name\FullyQualified) {
+                // parseIdentifier() has already removed the leading slash.
             } else {
                 $fullName = $this->getNamespacedClassName($name);
                 if ($fullName) {
                     $name = $fullName;
                 }
             }
-            return Symbol::constant() . '(nullptr, ' . $this->getLiteralString($name) . ')';
+
+            if ($this->hasConstant($name)) {
+                return $this->getConstant($name);
+            }
+            if ($name === 'PHP_EOL') {
+                return '"' . $this->escapeString(PHP_EOL) . '"';
+            }
+            if ($this->isInternalScalarConstant($name)) {
+                return $this->getInternalScalarConstantValue($name);
+            }
+            if ($this->isInternalConstant($name)) {
+                return Symbol::constant() . '(' . $this->getLiteralString($name) . ')';
+            }
+
+            return Symbol::constant() . '(' . $this->getLiteralString($name) . ')';
         }
         return Symbol::constant() . '("' . $this->escapeString($name) . '")';
     }

tests/compiler/const/define-runtime-name-compatibility.phpt

@@ -0,0 +1,17 @@
+--TEST--
+define accepts namespaced and non-identifier constant names like PHP
+--FILE--
+<?php
+
+function main(): void
+{
+    define('Vendor\Package\VALUE', 42);
+    define('1 non identifier', 'supported');
+
+    var_dump(constant('Vendor\Package\VALUE'));
+    var_dump(constant('1 non identifier'));
+}
+?>
+--EXPECT--
+int(42)
+string(9) "supported"

tests/compiler/namespace/runtime-constant-global-fallback.phpt

@@ -0,0 +1,41 @@
+--TEST--
+Unqualified runtime constants in a namespace fall back to global constants
+--FILE--
+<?php
+
+namespace RuntimeConstantFallback {
+    function readGlobalOnly()
+    {
+        return GLOBAL_ONLY;
+    }
+
+    function readPreferred()
+    {
+        return PREFERRED;
+    }
+
+    function readInternalOverride()
+    {
+        return PHP_VERSION;
+    }
+}
+
+namespace {
+    function main(): void
+    {
+        define('GLOBAL_ONLY', 'global');
+        define('PREFERRED', 'global-preferred');
+        define('RuntimeConstantFallback\Preferred', 'wrong-case-name');
+        define('RuntimeConstantFallback\PREFERRED', 'namespaced');
+        define('RuntimeConstantFallback\PHP_VERSION', 'runtime-override');
+
+        var_dump(\RuntimeConstantFallback\readGlobalOnly());
+        var_dump(\RuntimeConstantFallback\readPreferred());
+        var_dump(\RuntimeConstantFallback\readInternalOverride());
+    }
+}
+?>
+--EXPECT--
+string(6) "global"
+string(10) "namespaced"
+string(16) "runtime-override"

tests/compiler/namespace/runtime-constant-qualified-import.phpt

@@ -0,0 +1,45 @@
+--TEST--
+Qualified and imported runtime constants use their exact resolved names
+--FILE--
+<?php
+
+namespace RuntimeConstantConsumer {
+    use const RuntimeConstantProvider\IMPORTED_VALUE as IMPORTED;
+    use RuntimeConstantProvider\CLASS_ALIAS_COLLISION;
+
+    function readImported()
+    {
+        return IMPORTED;
+    }
+
+    function readQualified()
+    {
+        return Config\PATH;
+    }
+
+    function readClassAliasCollision()
+    {
+        return CLASS_ALIAS_COLLISION;
+    }
+}
+
+namespace {
+    function main(): void
+    {
+        define('RuntimeConstantProvider\IMPORTED_VALUE', 'imported');
+        define('RuntimeConstantConsumer\Config\PATH', 'qualified');
+        define('CLASS_ALIAS_COLLISION', 'global-constant');
+        define('RuntimeConstantProvider\CLASS_ALIAS_COLLISION', 'wrong-provider');
+        define('IMPORTED', 'wrong-global');
+        define('Config\PATH', 'wrong-qualified');
+
+        var_dump(\RuntimeConstantConsumer\readImported());
+        var_dump(\RuntimeConstantConsumer\readQualified());
+        var_dump(\RuntimeConstantConsumer\readClassAliasCollision());
+    }
+}
+?>
+--EXPECT--
+string(8) "imported"
+string(9) "qualified"
+string(15) "global-constant"

tests/compiler/namespace/runtime-constant-undefined-error.phpt

@@ -0,0 +1,25 @@
+--TEST--
+Undefined runtime constants in a namespace throw Error after global fallback
+--FILE--
+<?php
+
+namespace RuntimeConstantUndefined {
+    function readMissing()
+    {
+        return MISSING_RUNTIME_CONSTANT;
+    }
+}
+
+namespace {
+    function main(): void
+    {
+        try {
+            \RuntimeConstantUndefined\readMissing();
+        } catch (\Error $error) {
+            echo $error->getMessage(), PHP_EOL;
+        }
+    }
+}
+?>
+--EXPECT--
+Undefined constant "RuntimeConstantUndefined\MISSING_RUNTIME_CONSTANT"