[RFC] Implement constants in traits

Zend/Optimizer/pass1.c

@@ -164,7 +164,7 @@ void zend_optimizer_pass1(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 				if (ce) {
 					zend_class_constant *cc = zend_hash_find_ptr(
 						&ce->constants_table, Z_STR(ZEND_OP2_LITERAL(opline)));
-					if (cc && (ZEND_CLASS_CONST_FLAGS(cc) & ZEND_ACC_PPP_MASK) == ZEND_ACC_PUBLIC) {
+					if (cc && (ZEND_CLASS_CONST_FLAGS(cc) & ZEND_ACC_PPP_MASK) == ZEND_ACC_PUBLIC && !(ce->ce_flags & ZEND_ACC_TRAIT)) {
 						zval *c = &cc->value;
 						if (Z_TYPE_P(c) == IS_CONSTANT_AST) {
 							zend_ast *ast = Z_ASTVAL_P(c);

Zend/tests/enum/traits-constants.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Enum can use traits having constants
+--FILE--
+<?php
+
+trait Rectangle {
+    private const MESSAGE_RECTANGLE = 'Rectangle';
+
+    public function shape(): string {
+        return self::MESSAGE_RECTANGLE;
+    }
+}
+
+enum Suit {
+    use Rectangle;
+
+    case Hearts;
+    case Diamonds;
+    case Clubs;
+    case Spades;
+}
+
+echo Suit::Hearts->shape() . PHP_EOL;
+echo Suit::Diamonds->shape() . PHP_EOL;
+echo Suit::Clubs->shape() . PHP_EOL;
+echo Suit::Spades->shape() . PHP_EOL;
+
+?>
+--EXPECT--
+Rectangle
+Rectangle
+Rectangle
+Rectangle

Zend/tests/traits/constant_001.phpt

@@ -0,0 +1,55 @@
+--TEST--
+Trying to access a constant on Trait via a Class
+--FILE--
+<?php
+
+trait Foo {
+    public const PUBLIC = 'public';
+    protected const PROTECTED = 'protected';
+    private const PRIVATE = 'private';
+
+    public function f1(): void {
+        echo self::PUBLIC, ' via self', PHP_EOL;
+        echo static::PUBLIC, ' via static', PHP_EOL;
+        echo $this::PUBLIC, ' via $this', PHP_EOL;
+    }
+}
+
+class Base {
+    use Foo;
+
+    public function f2(): void {
+        echo self::PRIVATE, ' via self', PHP_EOL;
+        echo static::PRIVATE, ' via static', PHP_EOL;
+    }
+}
+
+class Derived extends Base {
+    public function f3(): void {
+        echo self::PROTECTED, ' via self', PHP_EOL;
+        echo static::PROTECTED, ' via static', PHP_EOL;
+        echo parent::PROTECTED, ' via parent', PHP_EOL;
+    }
+}
+
+echo Base::PUBLIC, ' via class name', PHP_EOL;
+echo (new Base)::PUBLIC, ' via object', PHP_EOL;
+(new Base)->f1();
+(new Base)->f2();
+echo Derived::PUBLIC, ' via derived class name', PHP_EOL;
+echo (new Derived)::PUBLIC, ' via derived class object', PHP_EOL;
+(new Derived)->f3();
+?>
+--EXPECTF--
+public via class name
+public via object
+public via self
+public via static
+public via $this
+private via self
+private via static
+public via derived class name
+public via derived class object
+protected via self
+protected via static
+protected via parent

Zend/tests/traits/constant_002.phpt

@@ -0,0 +1,42 @@
+--TEST--
+Defining a constant in both trait and its composing class with the same name, visibility, finality and value is allowed
+--FILE--
+<?php
+
+trait TestTrait1 {
+    public const A = 42;
+}
+
+trait TestTrait2 {
+    public const A = 42;
+}
+
+trait TestTrait3 {
+    use TestTrait2;
+    public const A = 42;
+}
+
+class ComposingClass1 {
+    use TestTrait1;
+    use TestTrait2;
+}
+
+class ComposingClass2 {
+    use TestTrait1;
+    use TestTrait3;
+}
+
+class ComposingClass3 {
+    use TestTrait1;
+    use TestTrait3;
+    public const A = 42;
+}
+
+echo ComposingClass1::A, PHP_EOL;
+echo ComposingClass2::A, PHP_EOL;
+echo ComposingClass3::A, PHP_EOL;
+?>
+--EXPECTF--
+42
+42
+42

Zend/tests/traits/constant_003.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Non-final Constants in traits can be overridden in derived classes
+--FILE--
+<?php
+
+trait Foo {
+    public const A = 123;
+}
+
+class Base {
+    use Foo;
+}
+
+class Derived extends Base {
+    public const A = 456;
+}
+
+echo Derived::A, PHP_EOL;
+?>
+--EXPECTF--
+456

Zend/tests/traits/constant_004.phpt

@@ -0,0 +1,19 @@
+--TEST--
+Trying to access a constant on trait via the name of trait causes a Fatal error
+--FILE--
+<?php
+trait Foo {
+    const A = 42;
+}
+
+class Bar {
+    use Foo;
+}
+
+echo Foo::A, PHP_EOL;
+?>
+--EXPECTF--
+Fatal error: Uncaught Error: Cannot access trait constant Foo::A directly in %s:%d
+Stack trace:
+#0 {main}
+  thrown in %s on line %d

Zend/tests/traits/constant_005.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Conflicting constants in composing classes with different visibility modifiers should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait TestTrait {
+  public const Constant = 42;
+}
+
+echo "PRE-CLASS-GUARD\n";
+
+class ComposingClass {
+    use TestTrait;
+    private const Constant = 42;
+}
+
+echo "POST-CLASS-GUARD\n";
+?>
+--EXPECTF--
+PRE-CLASS-GUARD
+
+Fatal error: ComposingClass and TestTrait define the same constant (Constant) in the composition of ComposingClass. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_006.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Conflicting constants in composing classes with different values should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait TestTrait {
+  public const Constant = 123;
+}
+
+echo "PRE-CLASS-GUARD\n";
+
+class ComposingClass {
+    use TestTrait;
+    public const Constant = 456;
+}
+
+echo "POST-CLASS-GUARD\n";
+?>
+--EXPECTF--
+PRE-CLASS-GUARD
+
+Fatal error: ComposingClass and TestTrait define the same constant (Constant) in the composition of ComposingClass. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_007.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Conflicting constants in composing classes with different finality should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait TestTrait {
+  public const Constant = 42;
+}
+
+echo "PRE-CLASS-GUARD\n";
+
+class ComposingClass {
+    use TestTrait;
+    public final const Constant = 42;
+}
+
+echo "POST-CLASS-GUARD\n";
+?>
+--EXPECTF--
+PRE-CLASS-GUARD
+
+Fatal error: ComposingClass and TestTrait define the same constant (Constant) in the composition of ComposingClass. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_008.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Conflicting constants in another traits in same composing classes with different visibility modifiers should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait Trait1 {
+  public const Constant = 42;
+}
+
+trait Trait2 {
+  private const Constant = 42;
+}
+
+echo "PRE-CLASS-GUARD\n";
+
+class TraitsTest {
+    use Trait1;
+    use Trait2;
+}
+
+echo "POST-CLASS-GUARD\n";
+?>
+--EXPECTF--
+PRE-CLASS-GUARD
+
+Fatal error: Trait1 and Trait2 define the same constant (Constant) in the composition of TraitsTest. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_009.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Conflicting constants in another traits in same composing classes with different values should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait Trait1 {
+  public const Constant = 123;
+}
+
+trait Trait2 {
+  public const Constant = 456;
+}
+
+echo "PRE-CLASS-GUARD\n";
+
+class TraitsTest {
+    use Trait1;
+    use Trait2;
+}
+
+echo "POST-CLASS-GUARD\n";
+?>
+--EXPECTF--
+PRE-CLASS-GUARD
+
+Fatal error: Trait1 and Trait2 define the same constant (Constant) in the composition of TraitsTest. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_010.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Conflicting constants in another traits in same composing classes with different finality should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait TestTrait {
+  public const Constant = 42;
+}
+
+echo "PRE-CLASS-GUARD\n";
+
+class ComposingClass {
+    use TestTrait;
+    public final const Constant = 42;
+}
+
+echo "POST-CLASS-GUARD\n";
+?>
+--EXPECTF--
+PRE-CLASS-GUARD
+
+Fatal error: ComposingClass and TestTrait define the same constant (Constant) in the composition of ComposingClass. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_011.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Conflicting constants in a trait and another trait using it with different visibility modifiers should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait Trait1 {
+    public const Constant = 42;
+}
+
+trait Trait2 {
+    use Trait1;
+    private const Constant = 42;
+}
+?>
+--EXPECTF--
+Fatal error: Trait2 and Trait1 define the same constant (Constant) in the composition of Trait2. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_012.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Conflicting constants in a trait and another trait using it with different values should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait Trait1 {
+    public const Constant = 123;
+}
+
+trait Trait2 {
+    use Trait1;
+    public const Constant = 456;
+}
+?>
+--EXPECTF--
+Fatal error: Trait2 and Trait1 define the same constant (Constant) in the composition of Trait2. However, the definition differs and is considered incompatible. Class was composed in %s on line %d

Zend/tests/traits/constant_013.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Conflicting constants in a trait and another trait using it with different finality should result in a fatal error, since this indicates that the code is incompatible.
+--FILE--
+<?php
+
+trait Trait1 {
+    public const Constant = 123;
+}
+
+trait Trait2 {
+    use Trait1;
+    public const Constant = 456;
+}
+?>
+--EXPECTF--
+Fatal error: Trait2 and Trait1 define the same constant (Constant) in the composition of Trait2. However, the definition differs and is considered incompatible. Class was composed in %s on line %d