From 4285d5fad81839bdcfe62906f83bef5def5c9623 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Tue, 8 Nov 2022 17:45:06 +0100
Subject: [PATCH] Fix printing of comments before `=>` (#15160)

Fixes https://github.com/babel/babel/issues/15161
---
 .../babel-generator/src/generators/methods.ts |  5 ++++-
 .../test/fixtures/regression/15161/input.js   |  3 +++
 .../fixtures/regression/15161/options.json    |  3 +++
 .../test/fixtures/regression/15161/output.js  |  3 +++
 packages/babel-generator/test/index.js        | 19 ++++++++++++++++++-
 5 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 packages/babel-generator/test/fixtures/regression/15161/input.js
 create mode 100644 packages/babel-generator/test/fixtures/regression/15161/options.json
 create mode 100644 packages/babel-generator/test/fixtures/regression/15161/output.js

diff --git a/packages/babel-generator/src/generators/methods.ts b/packages/babel-generator/src/generators/methods.ts
index 5d30ac98453d..e8a94da32898 100644
--- a/packages/babel-generator/src/generators/methods.ts
+++ b/packages/babel-generator/src/generators/methods.ts
@@ -11,7 +11,10 @@ export function _params(
   this._parameters(node.params, node);
   this.token(")");
 
-  this.print(node.returnType, node, node.type === "ArrowFunctionExpression");
+  const noLineTerminator = node.type === "ArrowFunctionExpression";
+  this.print(node.returnType, node, noLineTerminator);
+
+  this._noLineTerminator = noLineTerminator;
 }
 
 export function _parameters(
diff --git a/packages/babel-generator/test/fixtures/regression/15161/input.js b/packages/babel-generator/test/fixtures/regression/15161/input.js
new file mode 100644
index 000000000000..7e0951ac0169
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/regression/15161/input.js
@@ -0,0 +1,3 @@
+var test = (/* placeholder */) => {
+  /* Unused */
+}
diff --git a/packages/babel-generator/test/fixtures/regression/15161/options.json b/packages/babel-generator/test/fixtures/regression/15161/options.json
new file mode 100644
index 000000000000..893844304ade
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/regression/15161/options.json
@@ -0,0 +1,3 @@
+{
+  "comments": false
+}
diff --git a/packages/babel-generator/test/fixtures/regression/15161/output.js b/packages/babel-generator/test/fixtures/regression/15161/output.js
new file mode 100644
index 000000000000..ef5f61e62396
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/regression/15161/output.js
@@ -0,0 +1,3 @@
+var test = (
+) => {
+};
\ No newline at end of file
diff --git a/packages/babel-generator/test/index.js b/packages/babel-generator/test/index.js
index 913325f21df5..a5493e1ee858 100644
--- a/packages/babel-generator/test/index.js
+++ b/packages/babel-generator/test/index.js
@@ -1151,7 +1151,7 @@ describe("programmatic generation", function () {
       expect(generate(expr).code).toMatchInlineSnapshot(`"1 + 2 /*foo*/"`);
     });
 
-    it("comment skipped because of newlines", () => {
+    it("comment skipped in arrow function because of newlines", () => {
       const arrow = t.arrowFunctionExpression(
         [t.identifier("x"), t.identifier("y")],
         t.identifier("z"),
@@ -1166,6 +1166,23 @@ describe("programmatic generation", function () {
         line*/"
       `);
     });
+
+    it("comment in arrow function with return type", () => {
+      const arrow = t.arrowFunctionExpression(
+        [t.identifier("x"), t.identifier("y")],
+        t.identifier("z"),
+      );
+      arrow.returnType = t.tsTypeAnnotation(t.tsAnyKeyword());
+      arrow.returnType.trailingComments = [
+        { type: "CommentBlock", value: "foo" },
+        // This comment is dropped. There is no way to safely print it
+        // as a trailingComment of the return type.
+        { type: "CommentBlock", value: "new\nline" },
+      ];
+      expect(generate(arrow).code).toMatchInlineSnapshot(
+        `"(x, y): any /*foo*/ => z"`,
+      );
+    });
   });
 });