Implement first-class callable syntax

See https://wiki.php.net/rfc/first_class_callable_syntax

Author: thekid

composer.json

@@ -7,7 +7,7 @@
   "keywords": ["module", "xp"],
   "require" : {
     "xp-framework/core": "^10.0 | ^9.0 | ^8.0 | ^7.0",
-    "xp-framework/ast": "^7.3",
+    "xp-framework/ast": "dev-feature/first_class_callable_syntax as 7.4.0",
     "php" : ">=7.0.0"
   },
   "require-dev" : {

src/main/php/lang/ast/emit/PHP.class.php

@@ -988,6 +988,13 @@ protected function emitNewClass($result, $new) {
     array_shift($result->type);
   }
 
+  protected function emitCallable($result, $callable) {
+    $t= $result->temp();
+    $result->out->write('fn(...'.$t.') => ');
+    $this->emitOne($result, $callable->expression);
+    $result->out->write('(... '.$t.')');
+  }
+
   protected function emitInvoke($result, $invoke) {
     $this->emitOne($result, $invoke->expression);
     $result->out->write('(');

src/main/php/lang/ast/emit/PHP70.class.php

@@ -8,7 +8,7 @@
  * @see  https://wiki.php.net/rfc#php_70
  */
 class PHP70 extends PHP {
-  use OmitPropertyTypes, OmitConstModifiers;
+  use OmitPropertyTypes, OmitConstModifiers, CallablesAsClosures;
   use RewriteNullCoalesceAssignment, RewriteLambdaExpressions, RewriteMultiCatch, RewriteClassOnObjects, RewriteExplicitOctals;
 
   /** Sets up type => literal mappings */

src/main/php/lang/ast/emit/PHP71.class.php

@@ -8,7 +8,7 @@
  * @see  https://wiki.php.net/rfc#php_71
  */
 class PHP71 extends PHP {
-  use OmitPropertyTypes;
+  use OmitPropertyTypes, CallablesAsClosures;
   use RewriteNullCoalesceAssignment, RewriteLambdaExpressions, RewriteClassOnObjects, RewriteExplicitOctals;
 
   /** Sets up type => literal mappings */

src/main/php/lang/ast/emit/PHP72.class.php

@@ -8,7 +8,7 @@
  * @see  https://wiki.php.net/rfc#php_72
  */
 class PHP72 extends PHP {
-  use OmitPropertyTypes;
+  use OmitPropertyTypes, CallablesAsClosures;
   use RewriteNullCoalesceAssignment, RewriteLambdaExpressions, RewriteClassOnObjects, RewriteExplicitOctals;
 
   /** Sets up type => literal mappings */