keep currying when compiling curried closures

src/Utils/index.php

@@ -71,6 +71,9 @@ function memoize(callable $callable)
  * Flattens a callable into a plain closure. Compilable objects (decorators, pipelines, predicates) are compiled, so
  * calling the result does not go through them, also when given as a closure of their `__invoke` (e.g. `$pipe(...)`);
  * any other callable is converted with closure().
+ *
+ * A closure of a curried function's `__invoke` (`$curried(...)`) is kept as it is, so it keeps currying; the compiled
+ * curried function itself calls its target and does not curry further.
  */
 function compile(callable $callable): \Closure
 {
@@ -78,7 +81,9 @@ function compile(callable $callable): \Closure
         $reflection = new \ReflectionFunction($callable);
         $bound      = $reflection->getClosureThis();
 
-        return $bound instanceof Compilable && $reflection->getName() === '__invoke' ? $bound->compile() : $callable;
+        return $bound instanceof Compilable && !$bound instanceof CurriedFunction && $reflection->getName() === '__invoke'
+            ? $bound->compile()
+            : $callable;
     }
 
     return $callable instanceof Compilable ? $callable->compile() : closure($callable);

tests/CompileTest.php

@@ -243,6 +243,23 @@ class CompileTest extends \PHPUnit\Framework\TestCase
         $this->assertSame($pipeline('a')('b'), f\compile($pipeline)('a')('b'));
     }
 
+    public function testCompiledClosureOfCurriedKeepsCurrying()
+    {
+        $curried = f\curry(fn ($a, $b) => "$a$b");
+
+        $this->assertSame('ab', f\compile($curried(...))('a')('b'));
+        $this->assertSame('ab', f\compile($curried(...))('a', 'b'));
+    }
+
+    public function testCompiledPipelineOfCurriedClosureKeepsCurrying()
+    {
+        $curried  = f\curry(fn ($a, $b) => "$a$b");
+        $pipeline = f\pipe(strtoupper(...), $curried(...));
+
+        $this->assertSame($pipeline('a')('b'), f\compile($pipeline)('a')('b'));
+        $this->assertSame('ab', f\compile(f\pipe($curried(...), fn ($rest) => $rest('b')))('a'));
+    }
+
     public function testCompileUnwrapsClosureOfCompilable()
     {
         $spy = new class(strtoupper(...)) extends FunctionPipeline {