Handle short closures with blocks vs. single-expression form

[thekid]

This PR implements an extension of the Arrow Function syntax supporting multiple statements proposed by https://wiki.php.net/rfc/auto-capture-closure.

Example

$key= new Secret('...');

// Single expression form
$encrypt= fn($value, $nonce) => sodium_crypto_secretbox($value, $nonce, $key->reveal());

// Short closure with block
$decrypt= fn($cipher, $nonce) {
  if (false === ($r= sodium_crypto_secretbox_open($cipher, $nonce, $key->reveal()))) {
    throw new FormatException('Decryption failed');
  }
  return $r;
};

Diff for XP Compiler

No additional changes are required except for a couple of integration tests.

diff --git a/src/test/php/lang/ast/unittest/emit/LambdasTest.class.php b/src/test/php/lang/ast/unittest/emit/LambdasTest.class.php
index 92e1999..94b3718 100755
--- a/src/test/php/lang/ast/unittest/emit/LambdasTest.class.php
+++ b/src/test/php/lang/ast/unittest/emit/LambdasTest.class.php
@@ -189,8 +189,9 @@ class LambdasTest extends EmittingTest {
     Assert::equals('IIFE', $r);
   }
 
+  /** @deprecated */
   #[Test]
-  public function with_block() {
+  public function with_arrow_and_block() {
     $r= $this->run('class <T> {
       public function run() {
         return fn() => {
@@ -199,6 +200,21 @@ class LambdasTest extends EmittingTest {
         };
       }
     }');
+    \xp::gc(); // Clear deprecation notice
+
+    Assert::equals(2, $r());
+  }
+
+  #[Test]
+  public function with_block() {
+    $r= $this->run('class <T> {
+      public function run() {
+        return fn() {
+          $a= 1;
+          return $a + 1;
+        };
+      }
+    }');
 
     Assert::equals(2, $r());
   }
@@ -208,7 +224,7 @@ class LambdasTest extends EmittingTest {
     $r= $this->run('class <T> {
       public function run() {
         $a= 1;
-        return fn() => {
+        return fn() {
           return $a + 1;
         };
       }

See also

• Implement short functions with auto capture php/php-src#8330
• Auto-capturing multi-statement closures php/php-src#6246 (comment)

[thekid]

The RFC has been declined with a vote of 27 in favor and 16 against.

https://externals.io/message/118154#118270