Fix GH-16643: Improve incompatible trait property error message

When a class and a trait (or two traits) define the same property in an
incompatible way, the error message now states why the definitions are
considered incompatible: differing visibility, static or readonly
modifiers, types, or default values, including the case where only one
of them has a default value (e.g. a constructor promoted property).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: glbessa

Zend/tests/readonly_props/readonly_trait_mismatch.phpt

@@ -15,4 +15,4 @@ class C {
 
 ?>
 --EXPECTF--
-Fatal error: T1 and T2 define the same property ($prop) in the composition of C. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: T1 and T2 define the same property ($prop) in the composition of C. However, the definition differs and is considered incompatible: only one of them is readonly. Class was composed in %s on line %d

Zend/tests/readonly_props/readonly_with_default_trait_mismatch.phpt

@@ -17,4 +17,4 @@ class C {
 
 ?>
 --EXPECTF--
-Fatal error: T1 and T2 define the same property ($prop) in the composition of C. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: T1 and T2 define the same property ($prop) in the composition of C. However, the definition differs and is considered incompatible: the default values differ. Class was composed in %s on line %d

Zend/tests/traits/bug60369.phpt

@@ -14,4 +14,4 @@ class Properties {
 
 ?>
 --EXPECTF--
-Fatal error: Properties and PropertiesTrait define the same property ($same) in the composition of Properties. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: Properties and PropertiesTrait define the same property ($same) in the composition of Properties. However, the definition differs and is considered incompatible: only one of them is static. Class was composed in %s on line %d

Zend/tests/traits/bug60536_002.phpt

@@ -34,4 +34,4 @@ $t->hello = "foo";
 PRE-CLASS-GUARD
 POST-CLASS-GUARD
 
-Fatal error: TraitsTest and THello1 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: TraitsTest and THello1 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible: the visibility differs. Class was composed in %s on line %d

Zend/tests/traits/bug74269.phpt

@@ -14,4 +14,4 @@ class PropertiesExample
 }
 ?>
 --EXPECTF--
-Fatal error: PropertiesExample and PropertiesTrait define the same property ($same) in the composition of PropertiesExample. However, the definition differs and is considered incompatible. Class was composed in %s
+Fatal error: PropertiesExample and PropertiesTrait define the same property ($same) in the composition of PropertiesExample. However, the definition differs and is considered incompatible: the default values differ. Class was composed in %s

Zend/tests/traits/bugs/overridding-conflicting-property-initializer.phpt

@@ -20,4 +20,4 @@ $obj = new baz();
 echo $obj->zoo, "\n";
 ?>
 --EXPECTF--
-Fatal error: baz and foo define the same property ($zoo) in the composition of baz. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: baz and foo define the same property ($zoo) in the composition of baz. However, the definition differs and is considered incompatible: the default values differ. Class was composed in %s on line %d

Zend/tests/traits/gh16643.phpt

@@ -0,0 +1,18 @@
+--TEST--
+GH-16643: Incompatible trait property error message states the reason
+--FILE--
+<?php
+
+trait FooTrait {
+    private array $options = [];
+}
+
+class Foo {
+    use FooTrait;
+
+    public function __construct(private array $options = []) {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Foo and FooTrait define the same property ($options) in the composition of Foo. However, the definition differs and is considered incompatible: only one of them has a default value. Class was composed in %s on line %d

Zend/tests/traits/property003.phpt

@@ -26,4 +26,4 @@ $t->hello = "foo";
 --EXPECTF--
 PRE-CLASS-GUARD
 
-Fatal error: THello1 and THello2 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: THello1 and THello2 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible: the visibility differs. Class was composed in %s on line %d

Zend/tests/traits/property004.phpt

@@ -26,4 +26,4 @@ $t = new TraitsTest;
 --EXPECTF--
 PRE-CLASS-GUARD
 
-Fatal error: THello1 and THello2 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: THello1 and THello2 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible: the visibility differs. Class was composed in %s on line %d

Zend/tests/traits/property005.phpt

@@ -34,4 +34,4 @@ $t->hello = "foo";
 PRE-CLASS-GUARD
 POST-CLASS-GUARD
 
-Fatal error: TraitsTest and THello1 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible. Class was composed in %s on line %d
+Fatal error: TraitsTest and THello1 define the same property ($hello) in the composition of TraitsTest. However, the definition differs and is considered incompatible: the visibility differs. Class was composed in %s on line %d