From 66d8440bf27854345fb29f67634d92e8d3ee9ef2 Mon Sep 17 00:00:00 2001
From: Erik Demaine <edemaine@mit.edu>
Date: Sun, 5 Jan 2025 12:15:15 -0500
Subject: [PATCH] Fix immediately called `(op)` in pipeline context

Fixes #1672
---
 source/parser/lib.civet             | 16 +++++++++++-----
 test/function-block-shorthand.civet |  8 ++++++++
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/source/parser/lib.civet b/source/parser/lib.civet
index 21e2c49d..806be8ee 100644
--- a/source/parser/lib.civet
+++ b/source/parser/lib.civet
@@ -562,12 +562,18 @@ function processCallMemberExpression(node: CallExpression | MemberExpression): A
         (isComma(arg) as ASTLeaf).token = `)${op.token}(`
         commaCount++
     // Don't mess with (+)()
-    if args.length
-      children.splice 0, 2,
-        commaCount ?
+    if args#
+      if commaCount
+        children.splice 0, 2,
           type: "ParenthesizedExpression"
-          children: ["(", ...call.children, ")"]
-        : { ...call, type: "ParenthesizedExpression" }
+          children: ["(", call.children, ")"]
+          expression: call.children
+      else // already parenthesized by argument parens
+        middle := call.children[<..<]
+        children.splice 0, 2,
+          type: "ParenthesizedExpression"
+          expression: middle
+          children: [ call.children.0, middle, call.children.-1 ]
       // If nothing left to this CallExpression, remove the wrapper
       if children# is 1
         return children[0]
diff --git a/test/function-block-shorthand.civet b/test/function-block-shorthand.civet
index 82ad2a24..c0fc7ac6 100644
--- a/test/function-block-shorthand.civet
+++ b/test/function-block-shorthand.civet
@@ -920,6 +920,14 @@ describe "(op) shorthand", ->
     (1)
   """
 
+  testCase """
+    apply binary op with one argument in pipeline
+    ---
+    foo |> (+) x
+    ---
+    (x)(foo)
+  """
+
   testCase """
     apply binary op with no arguments
     ---