Optimize pipelines

See https://github.com/xp-framework/compiler/pull/188/files#r2203236350

Author: thekid

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

@@ -1,49 +1,78 @@
 <?php namespace lang\ast\emit;
 
-use lang\ast\nodes\{CallableExpression, CallableNewExpression, Variable};
+use lang\ast\nodes\{CallableExpression, CallableNewExpression, Literal, Variable};
 
 /**
  * Emulates pipelines / the pipe operator, including a null-safe version.
  *
+ * ```php
+ * // Enclose expressions as follows:
+ * $in |> $expr;
+ * ($expr)($in);
+ *
+ * // Optimize for string literals:
+ * $in |> 'strlen';
+ * strlen($in);
+ *
+ * // Optimize for first-class callables:
+ * $in |> strlen(...);
+ * strlen($in);
+ * ```
+ *
  * @see  https://wiki.php.net/rfc/pipe-operator-v3
  * @see  https://externals.io/message/107661#107670
+ * @test lang.ast.unittest.emit.EmulatePipelinesTest
  * @test lang.ast.unittest.emit.PipelinesTest
  */
 trait EmulatePipelines {
 
   protected function emitPipeTarget($result, $target, $arg) {
     if ($target instanceof CallableNewExpression) {
-      $target->type->arguments= [new Variable(substr($arg, 1))];
+      $target->type->arguments= [$arg];
       $this->emitOne($result, $target->type);
       $target->type->arguments= null;
     } else if ($target instanceof CallableExpression) {
       $this->emitOne($result, $target->expression);
-      $result->out->write('('.$arg.')');
+      $result->out->write('(');
+      $this->emitOne($result, $arg);
+      $result->out->write(')');
+    } else if ($target instanceof Literal) {
+      $result->out->write(trim($target->expression, '"\''));
+      $result->out->write('(');
+      $this->emitOne($result, $arg);
+      $result->out->write(')');
     } else {
       $result->out->write('(');
       $this->emitOne($result, $target);
-      $result->out->write(')('.$arg.')');
+      $result->out->write(')(');
+      $this->emitOne($result, $arg);
+      $result->out->write(')');
     }
   }
 
   protected function emitPipe($result, $pipe) {
 
-    // $expr |> strtoupper(...) => [$arg= $expr, strtoupper($arg)][1]
-    $t= $result->temp();
-    $result->out->write('['.$t.'=');
-    $this->emitOne($result, $pipe->expression);
-    $result->out->write(',');
-    $this->emitPipeTarget($result, $pipe->target, $t);
-    $result->out->write('][1]');
+    // <const> |> strtoupper(...) => strtoupper(<const>)
+    // <expr> |> strtoupper(...) => [$arg= <expr>, strtoupper($arg)][1]
+    if ($this->isConstant($result, $pipe->expression)) {
+      $this->emitPipeTarget($result, $pipe->target, $pipe->expression);
+    } else {
+      $t= $result->temp();
+      $result->out->write('['.$t.'=');
+      $this->emitOne($result, $pipe->expression);
+      $result->out->write(',');
+      $this->emitPipeTarget($result, $pipe->target, new Variable(substr($t, 1)));
+      $result->out->write('][1]');
+    }
   }
 
   protected function emitNullsafePipe($result, $pipe) {
 
-    // $expr ?|> strtoupper(...) => null === ($arg= $expr) ? null : strtoupper($arg)
+    // <expr> ?|> strtoupper(...) => null === ($arg= <expr>) ? null : strtoupper($arg)
     $t= $result->temp();
     $result->out->write('null===('.$t.'=');
     $this->emitOne($result, $pipe->expression);
     $result->out->write(')?null:');
-    $this->emitPipeTarget($result, $pipe->target, $t);
+    $this->emitPipeTarget($result, $pipe->target, new Variable(substr($t, 1)));
   }
 }

src/test/php/lang/ast/unittest/emit/EmulatePipelinesTest.class.php

@@ -0,0 +1,57 @@
+<?php namespace lang\ast\unittest\emit;
+
+use test\{Assert, Test, Values};
+
+class EmulatePipelinesTest extends EmittingTest {
+
+  /** @return string */
+  protected function runtime() { return 'php:8.4.0'; }
+
+  #[Test]
+  public function lhs_evaluation_order() {
+    Assert::equals(
+      '[$_0=result(),($expr)($_0)][1];',
+      $this->emit('result() |> $expr;')
+    );
+  }
+
+  #[Test]
+  public function to_expression() {
+    Assert::equals(
+      '($expr)("hi");',
+      $this->emit('"hi" |> $expr;')
+    );
+  }
+
+  #[Test, Values(['"strlen"', "'strlen'"])]
+  public function to_string_literal($notation) {
+    Assert::equals(
+      'strlen("hi");',
+      $this->emit('"hi" |> '.$notation.';')
+    );
+  }
+
+  #[Test]
+  public function to_array_literal() {
+    Assert::equals(
+      '([$this,"func",])("hi");',
+      $this->emit('"hi" |> [$this, "func"];')
+    );
+  }
+
+  #[Test]
+  public function to_first_class_callable() {
+    Assert::equals(
+      'strlen("hi");',
+      $this->emit('"hi" |> strlen(...);')
+    );
+  }
+
+  #[Test]
+  public function to_callable_new() {
+    Assert::equals(
+      'new \\util\\Date("2025-07-12");',
+      $this->emit('"2025-07-12" |> new \\util\\Date(...);')
+    );
+  }
+}