Type visibility

[thekid]

Suggestion

Support visibility modifiers on types:

• public - type can be used anywhere
• protected - type can only be used inside the same namespace and sub-namespaces
• private - type can only be used inside the same namespace

See https://externals.io/message/127341

POC (syntactical support)

Diff for xp-framework/ast:

diff --git a/src/main/php/lang/ast/syntax/PHP.class.php b/src/main/php/lang/ast/syntax/PHP.class.php
index 80186a6..9fcbd16 100755
--- a/src/main/php/lang/ast/syntax/PHP.class.php
+++ b/src/main/php/lang/ast/syntax/PHP.class.php
@@ -863,6 +863,24 @@ class PHP extends Language {
       return $type;
     });
 
+    $this->stmt('public', function($parse, $token) {
+      $type= $this->statement($parse);
+      $type->modifiers[]= 'public';
+      return $type;
+    });
+
+    $this->stmt('protected', function($parse, $token) {
+      $type= $this->statement($parse);
+      $type->modifiers[]= 'protected';
+      return $type;
+    });
+
+    $this->stmt('private', function($parse, $token) {
+      $type= $this->statement($parse);
+      $type->modifiers[]= 'private';
+      return $type;
+    });
+
     $this->stmt('#[', function($parse, $token) {
       $annotations= $this->annotations($parse, 'annotations');
       return $this->statement($parse)->annotate($annotations);
diff --git a/src/test/php/lang/ast/unittest/parse/TypesTest.class.php b/src/test/php/lang/ast/unittest/parse/TypesTest.class.php
index cafb2cb..7277e73 100755
--- a/src/test/php/lang/ast/unittest/parse/TypesTest.class.php
+++ b/src/test/php/lang/ast/unittest/parse/TypesTest.class.php
@@ -12,7 +12,7 @@ use lang\ast\nodes\{
   Literal
 };
 use lang\ast\types\IsValue;
-use test\{Assert, Expect, Test};
+use test\{Assert, Expect, Test, Values};
 
 class TypesTest extends ParseTest {
 
@@ -64,6 +64,22 @@ class TypesTest extends ParseTest {
     );
   }
 
+  #[Test, Values(['public', 'private', 'protected'])]
+  public function class_with_visibility($modifier) {
+    $this->assertParsed(
+      [new ClassDeclaration([$modifier], new IsValue('\\A'), null, [], [], null, null, self::LINE)],
+      $modifier.' class A { }'
+    );
+  }
+
+  #[Test]
+  public function public_abstract_class() {
+    $this->assertParsed(
+      [new ClassDeclaration(['abstract', 'public'], new IsValue('\\A'), null, [], [], null, null, self::LINE)],
+      'public abstract class A { }'
+    );
+  }
+
   #[Test]
   public function empty_interface() {
     $this->assertParsed(

Implemetation idea: Name mangling

Emit non-public classes with namespace name so they aren't "visible" to the outside:

namespace com\example;

// Emit this as `__com_example_Parser`
private class Parser { }

When encountering type names, check for private and protected names if the type doesn't exist:

namespace com\example;

class Subject {

  public function parse($input) {
    return new Parser($input); // Emitted as __com_example_Parser
  }
}

This would need some further adjustments to the reflection API, though!

Implemetation idea: Compiler checks

When encountering type names, check xp::$meta for class visibility, and yield errors accordingly:

namespace de\thekid;

use com\example\Parser;

class Subject {

  public function parse($input) {
    return new Parser($input);  // Error: Cannot use private class "com.example.Parser" in "de.thekid"
  }
}

Implemetation idea: Unchecked

Only store visibility modifiers inside xp::$meta but do not check it during compilation.