Implement partial function application

See https://wiki.php.net/rfc/partial_function_application_v2

Author: thekid

composer.json

@@ -8,7 +8,7 @@
   "require" : {
     "xp-framework/core": "^12.0 | ^11.6 | ^10.16",
     "xp-framework/reflection": "^3.2 | ^2.15",
-    "xp-framework/ast": "^11.7",
+    "xp-framework/ast": "dev-feature/pfa as 11.8.0",
     "php" : ">=7.4.0"
   },
   "require-dev" : {

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

@@ -1,32 +1,35 @@
 <?php namespace lang\ast\emit;
 
 use lang\ast\Node;
-use lang\ast\nodes\{Expression, InstanceExpression, ScopeExpression, Literal};
+use lang\ast\nodes\{Expression, InstanceExpression, ScopeExpression, Literal, Placeholder};
 
 /**
  * Rewrites callable expressions to `Callable::fromClosure()`
  *
  * @see  https://www.php.net/manual/de/closure.fromcallable.php
+ * @see  https://wiki.php.net/rfc/clone_with_v2
  * @see  https://wiki.php.net/rfc/first_class_callable_syntax
+ * @see  https://wiki.php.net/rfc/partial_function_application_v2
  */
 trait CallablesAsClosures {
+  use RewritePartialFunctionApplications { emitCallable as emitPartial; }
 
   private function emitQuoted($result, $node) {
     if ($node instanceof Literal) {
 
-      // Rewrite f() => "f"
+      // Rewrite f(...) => "f"
       $result->out->write('"'.trim($node, '"\'').'"');
     } else if ($node instanceof InstanceExpression) {
 
-      // Rewrite $this->f => [$this, "f"]
+      // Rewrite $this->f(...) => [$this, "f"]
       $result->out->write('[');
       $this->emitOne($result, $node->expression);
       $result->out->write(',');
       $this->emitQuoted($result, $node->member);
       $result->out->write(']');
     } else if ($node instanceof ScopeExpression) {
 
-      // Rewrite T::f => [T::class, "f"]
+      // Rewrite T::f(...) => [T::class, "f"]
       $result->out->write('[');
       if ($node->type instanceof Node) {
         $this->emitOne($result, $node->type);
@@ -38,7 +41,7 @@ private function emitQuoted($result, $node) {
       $result->out->write(']');
     } else if ($node instanceof Expression) {
 
-      // Rewrite T::{<f>} => [T::class, <f>]
+      // Rewrite T::{<f>}(...) => [T::class, <f>]
       $this->emitOne($result, $node->inline);
     } else {
 
@@ -50,6 +53,8 @@ private function emitQuoted($result, $node) {
   protected function emitCallable($result, $callable) {
     if ($callable->expression instanceof Literal && 'clone' === $callable->expression->expression) {
       $result->out->write('fn($o) => clone $o');
+    } else if ([Placeholder::$VARIADIC] !== $callable->arguments) {
+      $this->emitPartial($result, $callable);
     } else {
       $result->out->write('\Closure::fromCallable(');
       $this->emitQuoted($result, $callable->expression);

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

@@ -12,6 +12,7 @@
   InstanceExpression,
   Literal,
   NewExpression,
+  Placeholder,
   Property,
   ScopeExpression,
   UnpackExpression,

src/main/php/lang/ast/emit/PHP81.class.php

@@ -22,7 +22,7 @@ class PHP81 extends PHP {
   use
     EmulatePipelines,
     RewriteBlockLambdaExpressions,
-    RewriteCallableClone,
+    RewriteCallables,
     RewriteCloneWith,
     RewriteDynamicClassConstants,
     RewriteStaticVariableInitializations,

src/main/php/lang/ast/emit/PHP82.class.php

@@ -22,7 +22,7 @@ class PHP82 extends PHP {
   use
     EmulatePipelines,
     RewriteBlockLambdaExpressions,
-    RewriteCallableClone,
+    RewriteCallables,
     RewriteCloneWith,
     RewriteDynamicClassConstants,
     RewriteStaticVariableInitializations,

src/main/php/lang/ast/emit/PHP83.class.php

@@ -19,7 +19,13 @@
  * @see  https://wiki.php.net/rfc#php_83
  */
 class PHP83 extends PHP {
-  use EmulatePipelines, RewriteCallableClone, RewriteCloneWith, RewriteBlockLambdaExpressions, RewriteProperties;
+  use 
+    EmulatePipelines,
+    RewriteCallables,
+    RewriteCloneWith,
+    RewriteBlockLambdaExpressions,
+    RewriteProperties
+  ;
 
   public $targetVersion= 80300;
 

src/main/php/lang/ast/emit/PHP84.class.php

@@ -19,7 +19,12 @@
  * @see  https://wiki.php.net/rfc#php_84
  */
 class PHP84 extends PHP {
-  use EmulatePipelines, RewriteCallableClone, RewriteCloneWith, RewriteBlockLambdaExpressions;
+  use
+    EmulatePipelines,
+    RewriteCallables,
+    RewriteCloneWith,
+    RewriteBlockLambdaExpressions
+  ;
 
   public $targetVersion= 80400;
 

src/main/php/lang/ast/emit/PHP85.class.php

@@ -19,7 +19,7 @@
  * @see  https://wiki.php.net/rfc#php_85
  */
 class PHP85 extends PHP {
-  use RewriteBlockLambdaExpressions, RewriteCallableClone, RewriteCloneWith; // TODO: Remove once PR is merged!
+  use RewriteBlockLambdaExpressions, RewriteCallables, RewriteCloneWith; // TODO: Remove once PR is merged!
 
   public $targetVersion= 80500;
 

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

@@ -0,0 +1,21 @@
+<?php namespace lang\ast\emit;
+
+use lang\ast\nodes\Literal;
+
+/**
+ * Rewrites `clone(...)` and partial function applications
+ *
+ * @see  https://wiki.php.net/rfc/clone_with_v2
+ * @see  https://wiki.php.net/rfc/partial_function_application_v2
+ */
+trait RewriteCallables {
+  use RewritePartialFunctionApplications { emitCallable as emitPartial; }
+
+  protected function emitCallable($result, $callable) {
+    if ($callable->expression instanceof Literal && 'clone' === $callable->expression->expression) {
+      $result->out->write('fn($o) => clone $o');
+    } else {
+      $this->emitPartial($result, $callable);
+    }
+  }
+}