From 13ac7fadc031039aa3661054161c3b1b5e3b1564 Mon Sep 17 00:00:00 2001
From: Spotandjake <40705786+spotandjake@users.noreply.github.com>
Date: Thu, 16 Jan 2025 21:35:32 -0500
Subject: [PATCH] fix(grainfmt): Fix formatting of function types with a single
 tuple arg (#2230)

---
 compiler/src/formatting/fmt.re            | 13 ++++++++++++-
 compiler/test/grainfmt/lambda.expected.gr |  3 +++
 compiler/test/grainfmt/lambda.input.gr    |  3 +++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/compiler/src/formatting/fmt.re b/compiler/src/formatting/fmt.re
index d384c0b823..adf8bb919a 100644
--- a/compiler/src/formatting/fmt.re
+++ b/compiler/src/formatting/fmt.re
@@ -2696,7 +2696,18 @@ let print_type = (fmt, {ptyp_desc, ptyp_loc}) => {
       )
       ++ break,
     )
-  | PTyArrow([{ptyp_arg_label: Unlabeled} as param], return) =>
+  | PTyArrow(
+      [
+        {
+          ptyp_arg_label: Unlabeled,
+          ptyp_arg_type: {
+            ptyp_desc:
+              PTyAny | PTyVar(_) | PTyArrow(_, _) | PTyConstr(_, []),
+          },
+        } as param,
+      ],
+      return,
+    ) =>
     fmt.print_parsed_type_argument(fmt, param)
     ++ string(" =>")
     ++ fmt.print_comment_range(
diff --git a/compiler/test/grainfmt/lambda.expected.gr b/compiler/test/grainfmt/lambda.expected.gr
index 1953857e98..56c9067299 100644
--- a/compiler/test/grainfmt/lambda.expected.gr
+++ b/compiler/test/grainfmt/lambda.expected.gr
@@ -9,6 +9,9 @@ y => {
   let z = 2
 }
 
+// Regression #2229
+let foo: ((a, b)) => Void = a => void
+
 let testfna = forEachCodePoint(c => /* arg */ void)
 
 let testfn = forEachCodePoint(c => /* arg */ {
diff --git a/compiler/test/grainfmt/lambda.input.gr b/compiler/test/grainfmt/lambda.input.gr
index aa1e62f751..9b0e172f16 100644
--- a/compiler/test/grainfmt/lambda.input.gr
+++ b/compiler/test/grainfmt/lambda.input.gr
@@ -7,6 +7,9 @@ y => {
   let z = 2
 }
 
+// Regression #2229
+let foo: ((a, b)) => Void = a => void
+
 let testfna = forEachCodePoint(c /* arg */ => void)
 
 let testfn = forEachCodePoint(c /* arg */ => {