From 41449c00a096e5c1773ee4a6a3ed6fddeef7b927 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Wed, 28 Sep 2022 17:36:30 -0400
Subject: [PATCH 01/11] fix: ensure no linebreak between async and do

---
 packages/babel-generator/src/generators/expressions.ts       | 5 ++++-
 .../fixtures/async-do-expressions/inner-comments/input.js    | 1 +
 .../fixtures/async-do-expressions/inner-comments/output.js   | 5 +++++
 3 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/input.js
 create mode 100644 packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js

diff --git a/packages/babel-generator/src/generators/expressions.ts b/packages/babel-generator/src/generators/expressions.ts
index 82680bca7868..5a7f690efc63 100644
--- a/packages/babel-generator/src/generators/expressions.ts
+++ b/packages/babel-generator/src/generators/expressions.ts
@@ -28,7 +28,10 @@ export function UnaryExpression(this: Printer, node: t.UnaryExpression) {
 export function DoExpression(this: Printer, node: t.DoExpression) {
   if (node.async) {
     this.word("async");
-    this.space();
+    this.ensureNoLineTerminator(() => {
+      this.printInnerComments(node);
+      this.space();
+    });
   }
   this.word("do");
   this.space();
diff --git a/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/input.js b/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/input.js
new file mode 100644
index 000000000000..6f070e80c4a6
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/input.js
@@ -0,0 +1 @@
+async /* 1 */ do /* 2 */ { /* 3 */ }
diff --git a/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js b/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js
new file mode 100644
index 000000000000..10ced6cf6aac
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js
@@ -0,0 +1,5 @@
+async /* 1 */ do
+/* 2 */
+{
+  /* 3 */
+};
\ No newline at end of file

From 390dadf9f10afd6cf95054e35f08a9e898ed3f37 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Thu, 29 Sep 2022 15:04:28 -0400
Subject: [PATCH 02/11] fix: ensure no linebreak before import assertion

---
 .../babel-generator/src/generators/modules.ts | 39 +++++++++++++++----
 packages/babel-generator/src/printer.ts       | 18 ++++-----
 .../import-assertion-inner-comment/input.js   |  1 +
 .../options.json                              |  3 ++
 .../import-assertion-inner-comment/output.js  |  3 ++
 5 files changed, 46 insertions(+), 18 deletions(-)
 create mode 100644 packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/options.json
 create mode 100644 packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js

diff --git a/packages/babel-generator/src/generators/modules.ts b/packages/babel-generator/src/generators/modules.ts
index 08c47bc17d9f..aed9cf13b593 100644
--- a/packages/babel-generator/src/generators/modules.ts
+++ b/packages/babel-generator/src/generators/modules.ts
@@ -80,9 +80,19 @@ export function ExportAllDeclaration(
   this.space();
   this.word("from");
   this.space();
-  this.print(node.source, node);
   // @ts-expect-error Fixme: assertions is not defined in DeclareExportAllDeclaration
-  this.printAssertions(node);
+  if (node.assertions?.length) {
+    this.ensureNoLineTerminator(() => {
+      this.print(node.source, node);
+      this.space();
+      this.word("assert");
+    });
+    // @ts-expect-error Fixme: assertions is not defined in DeclareExportAllDeclaration
+    this.printAssertions(node);
+  } else {
+    this.print(node.source, node);
+  }
+
   this.semicolon();
 }
 
@@ -146,8 +156,16 @@ export function ExportNamedDeclaration(
       this.space();
       this.word("from");
       this.space();
-      this.print(node.source, node);
-      this.printAssertions(node);
+      if (node.assertions?.length) {
+        this.ensureNoLineTerminator(() => {
+          this.print(node.source, node);
+          this.space();
+          this.word("assert");
+        });
+        this.printAssertions(node);
+      } else {
+        this.print(node.source, node);
+      }
     }
 
     this.semicolon();
@@ -220,9 +238,16 @@ export function ImportDeclaration(this: Printer, node: t.ImportDeclaration) {
     this.space();
   }
 
-  this.print(node.source, node);
-
-  this.printAssertions(node);
+  if (node.assertions?.length) {
+    this.ensureNoLineTerminator(() => {
+      this.print(node.source, node);
+      this.space();
+      this.word("assert");
+    });
+    this.printAssertions(node);
+  } else {
+    this.print(node.source, node);
+  }
   if (!process.env.BABEL_8_BREAKING) {
     // @ts-ignore(Babel 7 vs Babel 8) Babel 7 supports module attributes
     if (node.attributes?.length) {
diff --git a/packages/babel-generator/src/printer.ts b/packages/babel-generator/src/printer.ts
index 1d1c30c33712..7d39d5c7e7c3 100644
--- a/packages/babel-generator/src/printer.ts
+++ b/packages/babel-generator/src/printer.ts
@@ -1070,18 +1070,14 @@ class Printer {
       }
     }
   }
-  // todo(flow->ts): was Node
   printAssertions(node: Extract<t.Node, { assertions?: t.ImportAttribute[] }>) {
-    if (node.assertions?.length) {
-      this.space();
-      this.word("assert");
-      this.space();
-      this.token("{");
-      this.space();
-      this.printList(node.assertions, node);
-      this.space();
-      this.token("}");
-    }
+    this.space();
+    this.printInnerComments(node);
+    this.token("{");
+    this.space();
+    this.printList(node.assertions, node);
+    this.space();
+    this.token("}");
   }
 }
 
diff --git a/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/input.js b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/input.js
new file mode 100644
index 000000000000..a682899803dd
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/input.js
@@ -0,0 +1 @@
+import "foo" /* 1 */ assert /* 2 */ { type: "json" }
diff --git a/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/options.json b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/options.json
new file mode 100644
index 000000000000..a3a80a8b1511
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["importAssertions"]
+}
diff --git a/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js
new file mode 100644
index 000000000000..aa93403ae9c2
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js
@@ -0,0 +1,3 @@
+import "foo" /* 1 */ assert
+  /* 2 */
+{ type: "json" };
\ No newline at end of file

From c3b1abb03d886ab4adec1fb6261df91b5f3c0cf8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Thu, 29 Sep 2022 15:15:24 -0400
Subject: [PATCH 03/11] fix: ensure no linebreak between yield and *

---
 .../src/generators/expressions.ts              | 18 +++++++++++++-----
 .../comments/yield-star-inner-comment/input.js |  3 +++
 .../yield-star-inner-comment/output.js         |  5 +++++
 3 files changed, 21 insertions(+), 5 deletions(-)
 create mode 100644 packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js

diff --git a/packages/babel-generator/src/generators/expressions.ts b/packages/babel-generator/src/generators/expressions.ts
index 5a7f690efc63..be0779be5f7d 100644
--- a/packages/babel-generator/src/generators/expressions.ts
+++ b/packages/babel-generator/src/generators/expressions.ts
@@ -233,12 +233,20 @@ export function YieldExpression(this: Printer, node: t.YieldExpression) {
   this.word("yield");
 
   if (node.delegate) {
+    this.ensureNoLineTerminator(() => {
+      this.printInnerComments(node);
+    });
     this.token("*");
-  }
-
-  if (node.argument) {
-    this.space();
-    this.printTerminatorless(node.argument, node, false);
+    if (node.argument) {
+      this.space();
+      // line terminators are allowed after yield*
+      this.print(node.argument, node);
+    }
+  } else {
+    if (node.argument) {
+      this.space();
+      this.printTerminatorless(node.argument, node, false);
+    }
   }
 }
 
diff --git a/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/input.js b/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/input.js
new file mode 100644
index 000000000000..2da4cbddc5c2
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/input.js
@@ -0,0 +1,3 @@
+function * loop() {
+  yield /* 1 */ * /* 2 */ loop();
+}
diff --git a/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js b/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js
new file mode 100644
index 000000000000..127b2ad57717
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js
@@ -0,0 +1,5 @@
+function* loop() {
+  yield /* 1 */*
+  /* 2 */
+  loop();
+}
\ No newline at end of file

From 1d1ad27d572b914318ea03e1d3f932a9cf0eaba9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Fri, 30 Sep 2022 09:13:49 -0400
Subject: [PATCH 04/11] fixup import assertion

---
 packages/babel-generator/src/generators/modules.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/babel-generator/src/generators/modules.ts b/packages/babel-generator/src/generators/modules.ts
index aed9cf13b593..abffa0c1a1fc 100644
--- a/packages/babel-generator/src/generators/modules.ts
+++ b/packages/babel-generator/src/generators/modules.ts
@@ -239,8 +239,8 @@ export function ImportDeclaration(this: Printer, node: t.ImportDeclaration) {
   }
 
   if (node.assertions?.length) {
+    this.print(node.source, node, true);
     this.ensureNoLineTerminator(() => {
-      this.print(node.source, node);
       this.space();
       this.word("assert");
     });

From 1b3149f8c9a521e43a449b376bf0f35326bb628d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Fri, 30 Sep 2022 09:36:14 -0400
Subject: [PATCH 05/11] ensure no linebreak between async and */class key

---
 .../babel-generator/src/generators/methods.ts  | 18 +++++++++++++++---
 .../async-class-method-comment/input.js        |  3 +++
 .../async-class-method-comment/output.js       |  8 ++++++++
 .../input.js                                   |  3 +++
 .../output.js                                  | 14 ++++++++++++++
 .../input.js                                   |  3 +++
 .../output.js                                  |  8 ++++++++
 .../input.js                                   |  3 +++
 .../output.js                                  |  8 ++++++++
 9 files changed, 65 insertions(+), 3 deletions(-)
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-class-method-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js

diff --git a/packages/babel-generator/src/generators/methods.ts b/packages/babel-generator/src/generators/methods.ts
index 51bcdadcfae5..2015be425950 100644
--- a/packages/babel-generator/src/generators/methods.ts
+++ b/packages/babel-generator/src/generators/methods.ts
@@ -25,7 +25,8 @@ export function _parameters(
     | t.TSFunctionType
     | t.TSConstructorType,
 ) {
-  for (let i = 0; i < parameters.length; i++) {
+  const paramLength = parameters.length;
+  for (let i = 0; i < paramLength; i++) {
     this._param(parameters[i], parent);
 
     if (i < parameters.length - 1) {
@@ -33,6 +34,9 @@ export function _parameters(
       this.space();
     }
   }
+  if (paramLength === 0) {
+    this.printInnerComments(parent);
+  }
 }
 
 export function _param(
@@ -71,9 +75,10 @@ export function _methodHead(this: Printer, node: t.Method | t.TSDeclareMethod) {
     this.space();
   }
 
+  const { _noLineTerminator } = this;
   if (node.async) {
-    // ensure `async` is in the same line with property name
-    this._catchUp("start", key.loc);
+    // ensure no line terminator between async and class element name / *
+    this._noLineTerminator = true;
     this.word("async");
     this.space();
   }
@@ -84,16 +89,23 @@ export function _methodHead(this: Printer, node: t.Method | t.TSDeclareMethod) {
     kind === "init"
   ) {
     if (node.generator) {
+      if (node.async) {
+        this.printInnerComments(node);
+      }
       this.token("*");
+      this._noLineTerminator = _noLineTerminator;
     }
   }
 
   if (node.computed) {
     this.token("[");
+    this._noLineTerminator = _noLineTerminator;
     this.print(key, node);
     this.token("]");
+    this.printInnerComments(node);
   } else {
     this.print(key, node);
+    this._noLineTerminator = _noLineTerminator;
   }
 
   if (
diff --git a/packages/babel-generator/test/fixtures/comments/async-class-method-comment/input.js b/packages/babel-generator/test/fixtures/comments/async-class-method-comment/input.js
new file mode 100644
index 000000000000..41537f60553c
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-class-method-comment/input.js
@@ -0,0 +1,3 @@
+class C {
+  async /* 1 */ foo(/* 2 */) /* 3 */ {}
+}
diff --git a/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js
new file mode 100644
index 000000000000..63a2f2a565d0
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js
@@ -0,0 +1,8 @@
+class C {
+  async /* 1 */foo(
+    /* 2 */
+  )
+  /* 3 */
+  {}
+
+}
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/input.js b/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/input.js
new file mode 100644
index 000000000000..08504fa88eb9
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/input.js
@@ -0,0 +1,3 @@
+class C {
+  async /* 1 */ [ /* 2 */ foo /* 3 */] /* 4 */ (/* 5 */) {}
+}
diff --git a/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js
new file mode 100644
index 000000000000..0cbc3e2a3adc
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js
@@ -0,0 +1,14 @@
+class C {
+  async [
+  /* 2 */
+  foo
+  /* 3 */
+  ]
+    /* 1 */
+
+    /* 4 */
+
+    /* 5 */
+  () {}
+
+}
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js
new file mode 100644
index 000000000000..3ff717f026b7
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js
@@ -0,0 +1,3 @@
+class C {
+  async /* 1 */ * /* 2 */ foo(/* 3 */) /* 4 */ {}
+}
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
new file mode 100644
index 000000000000..53d406e37190
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
@@ -0,0 +1,8 @@
+class C {
+  async /* 1 */ /* 3 */*
+  /* 2 */
+  foo()
+  /* 4 */
+  {}
+
+}
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/input.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/input.js
new file mode 100644
index 000000000000..8d4ee08883c1
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/input.js
@@ -0,0 +1,3 @@
+class C {
+  async /* 1 */ * /* 2 */ [ /* 3 */ foo /* 4 */] /* 5 */ (/* 6 */) {}
+}
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js
new file mode 100644
index 000000000000..a883c47fcb24
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js
@@ -0,0 +1,8 @@
+class C {
+  async /* 1 */ /* 2 */ /* 5 */ /* 6 */*[
+  /* 3 */
+  foo
+  /* 4 */
+  ]() {}
+
+}
\ No newline at end of file

From 94ec62492103f4512b8b216ea3081509748f41fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Fri, 30 Sep 2022 10:20:59 -0400
Subject: [PATCH 06/11] ensure no line terminator before =>

---
 packages/babel-generator/src/generators/methods.ts         | 7 +++++--
 .../fixtures/comments/arrow-single-param-comment/input.js  | 1 +
 .../fixtures/comments/arrow-single-param-comment/output.js | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)
 create mode 100644 packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/input.js
 create mode 100644 packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/output.js

diff --git a/packages/babel-generator/src/generators/methods.ts b/packages/babel-generator/src/generators/methods.ts
index 2015be425950..2556aa1c425b 100644
--- a/packages/babel-generator/src/generators/methods.ts
+++ b/packages/babel-generator/src/generators/methods.ts
@@ -194,9 +194,12 @@ export function ArrowFunctionExpression(
   }
 
   this._predicate(node);
+  this.ensureNoLineTerminator(() => {
+    this.space();
+    this.printInnerComments(node);
+    this.token("=>");
+  });
 
-  this.space();
-  this.token("=>");
   this.space();
 
   this.print(node.body, node);
diff --git a/packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/input.js b/packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/input.js
new file mode 100644
index 000000000000..3429c0b66900
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/input.js
@@ -0,0 +1 @@
+(x)/* 1 */=>{}
diff --git a/packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/output.js b/packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/output.js
new file mode 100644
index 000000000000..286aeba5d144
--- /dev/null
+++ b/packages/babel-generator/test/fixtures/comments/arrow-single-param-comment/output.js
@@ -0,0 +1 @@
+x /* 1 */=> {};
\ No newline at end of file

From d47d8ad9745970972772c412e7ba2fd5c3ce4b7f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Fri, 30 Sep 2022 11:07:55 -0400
Subject: [PATCH 07/11] polish: allow comments when printing single-binding
 arrow

---
 .../babel-generator/src/generators/methods.ts | 20 +++++++++----------
 .../babel-generator/test/arrow-functions.js   | 15 ++++----------
 .../output.js                                 |  6 +++---
 .../async-arrow-function/output.js            |  6 +++---
 4 files changed, 19 insertions(+), 28 deletions(-)

diff --git a/packages/babel-generator/src/generators/methods.ts b/packages/babel-generator/src/generators/methods.ts
index 2556aa1c425b..5efd17a53582 100644
--- a/packages/babel-generator/src/generators/methods.ts
+++ b/packages/babel-generator/src/generators/methods.ts
@@ -170,26 +170,26 @@ export function ArrowFunctionExpression(
   this: Printer,
   node: t.ArrowFunctionExpression,
 ) {
+  const { _noLineTerminator } = this;
   if (node.async) {
+    this._noLineTerminator = true;
     this.word("async");
     this.space();
   }
 
-  const firstParam = node.params[0];
-
   // Try to avoid printing parens in simple cases, but only if we're pretty
   // sure that they aren't needed by type annotations or potential newlines.
+  let firstParam;
   if (
     !this.format.retainLines &&
-    // Auxiliary comments can introduce unexpected newlines
-    !this.format.auxiliaryCommentBefore &&
-    !this.format.auxiliaryCommentAfter &&
     node.params.length === 1 &&
-    isIdentifier(firstParam) &&
-    !hasTypesOrComments(node, firstParam)
+    isIdentifier((firstParam = node.params[0])) &&
+    !hasTypes(node, firstParam)
   ) {
     this.print(firstParam, node);
+    this._noLineTerminator = _noLineTerminator;
   } else {
+    this._noLineTerminator = _noLineTerminator;
     this._params(node);
   }
 
@@ -205,7 +205,7 @@ export function ArrowFunctionExpression(
   this.print(node.body, node);
 }
 
-function hasTypesOrComments(
+function hasTypes(
   node: t.ArrowFunctionExpression,
   param: t.Identifier,
 ): boolean {
@@ -214,8 +214,6 @@ function hasTypesOrComments(
     node.returnType ||
     node.predicate ||
     param.typeAnnotation ||
-    param.optional ||
-    param.leadingComments?.length ||
-    param.trailingComments?.length
+    param.optional
   );
 }
diff --git a/packages/babel-generator/test/arrow-functions.js b/packages/babel-generator/test/arrow-functions.js
index ec9cdc3c4b2b..537ca0c8da59 100644
--- a/packages/babel-generator/test/arrow-functions.js
+++ b/packages/babel-generator/test/arrow-functions.js
@@ -28,18 +28,15 @@ describe("parameter parentheses", () => {
     const output = generate(ast, { auxiliaryCommentBefore: "BEFORE" }).code;
     expect(output).toMatchInlineSnapshot(`
       "() => {};
-      (
       /*BEFORE*/
-      a) => {};
+      a => {};
       (
       /*BEFORE*/
       a,
       /*BEFORE*/
       b) => {};
       async () => {};
-      async (
-      /*BEFORE*/
-      a) => {};
+      async /*BEFORE*/a => {};
       async (
       /*BEFORE*/
       a,
@@ -53,18 +50,14 @@ describe("parameter parentheses", () => {
     const output = generate(ast, { auxiliaryCommentAfter: "AFTER" }).code;
     expect(output).toMatchInlineSnapshot(`
       "() => {};
-      (a
-      /*AFTER*/
-      ) => {};
+      a /*AFTER*/=> {};
       (a
       /*AFTER*/
       , b
       /*AFTER*/
       ) => {};
       async () => {};
-      async (a
-      /*AFTER*/
-      ) => {};
+      async a /*AFTER*/=> {};
       async (a
       /*AFTER*/
       , b
diff --git a/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js b/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js
index addc834ee0ed..a1e62b4e986f 100644
--- a/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js
@@ -1,3 +1,3 @@
-async ( /** @type {any} */arg) => {};
-async (arg /* trailing */) => {};
-async ( /** @type {any} */arg /* trailing */) => {};
\ No newline at end of file
+async /** @type {any} */arg => {};
+async arg /* trailing */ => {};
+async /** @type {any} */arg /* trailing */ => {};
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js b/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js
index bf33d2ca48fc..f718e264aefc 100644
--- a/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js
+++ b/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js
@@ -1,6 +1,6 @@
-const x = async (
-// some comment
-a) => {
+const x = async
+/* some comment*/
+a => {
   return foo(await a);
 };
 function foo(a) {

From 1306527a2720867a9912f969f498c33555f1a22b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Mon, 3 Oct 2022 20:31:26 -0400
Subject: [PATCH 08/11] review comment

---
 .../async-generator-class-method-comment/input.js         | 2 +-
 .../async-generator-class-method-comment/output.js        | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js
index 3ff717f026b7..0dd6805e1e51 100644
--- a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/input.js
@@ -1,3 +1,3 @@
 class C {
-  async /* 1 */ * /* 2 */ foo(/* 3 */) /* 4 */ {}
+  async /* 1 */ * /* 2 */ foo /* 3 */ (/* 4 */) /* 5 */ {}
 }
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
index 53d406e37190..2d9af81a4609 100644
--- a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
@@ -1,8 +1,10 @@
 class C {
-  async /* 1 */ /* 3 */*
+  async /* 1 */ /* 4 */*
   /* 2 */
-  foo()
-  /* 4 */
+  foo
+  /* 3 */
+  ()
+  /* 5 */
   {}
 
 }
\ No newline at end of file

From 43f826fc0ed0f34dcd6e41002a3d502933df7490 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Thu, 6 Oct 2022 17:48:27 +0200
Subject: [PATCH 09/11] Update fixtures

---
 .../async-do-expressions/inner-comments/output.js   |  6 +-----
 .../comments/async-class-method-comment/output.js   |  7 +------
 .../output.js                                       | 13 +------------
 .../async-generator-class-method-comment/output.js  |  9 +--------
 .../output.js                                       |  7 +------
 .../import-assertion-inner-comment/output.js        |  4 +---
 .../comments/yield-star-inner-comment/output.js     |  4 +---
 .../arrow-single-optional-param/output.js           |  2 +-
 .../flow-comments/arrow-single-param-type/output.js |  2 +-
 9 files changed, 9 insertions(+), 45 deletions(-)

diff --git a/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js b/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js
index 10ced6cf6aac..a9654126b38b 100644
--- a/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js
+++ b/packages/babel-generator/test/fixtures/async-do-expressions/inner-comments/output.js
@@ -1,5 +1 @@
-async /* 1 */ do
-/* 2 */
-{
-  /* 3 */
-};
\ No newline at end of file
+async /* 1 */ do /* 2 */{/* 3 */};
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js
index 63a2f2a565d0..8302e190cd10 100644
--- a/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-class-method-comment/output.js
@@ -1,8 +1,3 @@
 class C {
-  async /* 1 */foo(
-    /* 2 */
-  )
-  /* 3 */
-  {}
-
+  async /* 1 */foo( /* 2 */) /* 3 */{}
 }
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js
index 0cbc3e2a3adc..dbca0b9748d5 100644
--- a/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-class-method-computed-key-comment/output.js
@@ -1,14 +1,3 @@
 class C {
-  async [
-  /* 2 */
-  foo
-  /* 3 */
-  ]
-    /* 1 */
-
-    /* 4 */
-
-    /* 5 */
-  () {}
-
+  async [/* 2 */foo /* 3 */] /* 1 */ /* 4 */ /* 5 */() {}
 }
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
index 2d9af81a4609..89f3e529357b 100644
--- a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-comment/output.js
@@ -1,10 +1,3 @@
 class C {
-  async /* 1 */ /* 4 */*
-  /* 2 */
-  foo
-  /* 3 */
-  ()
-  /* 5 */
-  {}
-
+  async /* 1 */ /* 4 */* /* 2 */foo /* 3 */() /* 5 */{}
 }
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js
index a883c47fcb24..46783d555037 100644
--- a/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-generator-class-method-computed-key-comment/output.js
@@ -1,8 +1,3 @@
 class C {
-  async /* 1 */ /* 2 */ /* 5 */ /* 6 */*[
-  /* 3 */
-  foo
-  /* 4 */
-  ]() {}
-
+  async /* 1 */ /* 2 */ /* 5 */ /* 6 */*[/* 3 */foo /* 4 */]() {}
 }
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js
index aa93403ae9c2..15516625752a 100644
--- a/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/import-assertion-inner-comment/output.js
@@ -1,3 +1 @@
-import "foo" /* 1 */ assert
-  /* 2 */
-{ type: "json" };
\ No newline at end of file
+import "foo" /* 1 */ assert /* 2 */{ type: "json" };
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js b/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js
index 127b2ad57717..81c6fdfccdcf 100644
--- a/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js
+++ b/packages/babel-generator/test/fixtures/comments/yield-star-inner-comment/output.js
@@ -1,5 +1,3 @@
 function* loop() {
-  yield /* 1 */*
-  /* 2 */
-  loop();
+  yield /* 1 */* /* 2 */loop();
 }
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js
index b4c55a034047..97404c5ed653 100644
--- a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js
+++ b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js
@@ -1 +1 @@
-const x = (foo /*:: ?*/) => {};
+const x = foo /*:: ?*/ => {};
diff --git a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js
index e29c6196f0b9..fd89f9501670 100644
--- a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js
+++ b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js
@@ -1 +1 @@
-const x = (foo /*: string*/) => {};
+const x = foo /*: string*/ => {};

From bf8294441dd3f7834e08ef1a5742726a9d0de2c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Mon, 24 Oct 2022 10:40:18 -0400
Subject: [PATCH 10/11] address review comments

---
 packages/babel-generator/src/generators/methods.ts       | 9 ++++++---
 .../async-arrow-single-param-with-comments/output.js     | 6 +++---
 .../fixtures/parentheses/async-arrow-function/output.js  | 6 +++---
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/packages/babel-generator/src/generators/methods.ts b/packages/babel-generator/src/generators/methods.ts
index 5efd17a53582..4cfeaf151c16 100644
--- a/packages/babel-generator/src/generators/methods.ts
+++ b/packages/babel-generator/src/generators/methods.ts
@@ -184,7 +184,7 @@ export function ArrowFunctionExpression(
     !this.format.retainLines &&
     node.params.length === 1 &&
     isIdentifier((firstParam = node.params[0])) &&
-    !hasTypes(node, firstParam)
+    !hasTypesOrComments(node, firstParam)
   ) {
     this.print(firstParam, node);
     this._noLineTerminator = _noLineTerminator;
@@ -205,7 +205,7 @@ export function ArrowFunctionExpression(
   this.print(node.body, node);
 }
 
-function hasTypes(
+function hasTypesOrComments(
   node: t.ArrowFunctionExpression,
   param: t.Identifier,
 ): boolean {
@@ -214,6 +214,9 @@ function hasTypes(
     node.returnType ||
     node.predicate ||
     param.typeAnnotation ||
-    param.optional
+    param.optional ||
+    // Flow does not support `foo /*: string*/ => {};`
+    param.leadingComments?.length ||
+    param.trailingComments?.length
   );
 }
diff --git a/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js b/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js
index a1e62b4e986f..addc834ee0ed 100644
--- a/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js
+++ b/packages/babel-generator/test/fixtures/comments/async-arrow-single-param-with-comments/output.js
@@ -1,3 +1,3 @@
-async /** @type {any} */arg => {};
-async arg /* trailing */ => {};
-async /** @type {any} */arg /* trailing */ => {};
\ No newline at end of file
+async ( /** @type {any} */arg) => {};
+async (arg /* trailing */) => {};
+async ( /** @type {any} */arg /* trailing */) => {};
\ No newline at end of file
diff --git a/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js b/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js
index f718e264aefc..bf33d2ca48fc 100644
--- a/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js
+++ b/packages/babel-generator/test/fixtures/parentheses/async-arrow-function/output.js
@@ -1,6 +1,6 @@
-const x = async
-/* some comment*/
-a => {
+const x = async (
+// some comment
+a) => {
   return foo(await a);
 };
 function foo(a) {

From b5b0132fb65a87aa7ebdcc52827cb1daca36a321 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Mon, 24 Oct 2022 10:54:05 -0400
Subject: [PATCH 11/11] update test fixtures

---
 .../flow-comments/arrow-single-optional-param/output.js         | 2 +-
 .../fixtures/flow-comments/arrow-single-param-type/output.js    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js
index 97404c5ed653..b4c55a034047 100644
--- a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js
+++ b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-optional-param/output.js
@@ -1 +1 @@
-const x = foo /*:: ?*/ => {};
+const x = (foo /*:: ?*/) => {};
diff --git a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js
index fd89f9501670..e29c6196f0b9 100644
--- a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js
+++ b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/arrow-single-param-type/output.js
@@ -1 +1 @@
-const x = foo /*: string*/ => {};
+const x = (foo /*: string*/) => {};