From c5ed19c710fd32f5c23b2d85ff8f30cb09f58899 Mon Sep 17 00:00:00 2001
From: magic-akari <akari.ccino@gmail.com>
Date: Sat, 2 Nov 2024 09:10:57 +0800
Subject: [PATCH] fix(es/typescript): Handle multiline type parameters in async
 arrow functions (#9704)

**Related issue:**

- Closes https://github.com/swc-project/swc/issues/9698
---
 .changeset/swift-hairs-bow.md                 |  6 ++++
 crates/swc_fast_ts_strip/src/lib.rs           | 34 ++++++++++++++++---
 .../tests/fixture/issue-9698.js               |  9 +++++
 .../tests/fixture/issue-9698.transform.js     |  2 ++
 .../tests/fixture/issue-9698.ts               |  9 +++++
 5 files changed, 55 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/swift-hairs-bow.md
 create mode 100644 crates/swc_fast_ts_strip/tests/fixture/issue-9698.js
 create mode 100644 crates/swc_fast_ts_strip/tests/fixture/issue-9698.transform.js
 create mode 100644 crates/swc_fast_ts_strip/tests/fixture/issue-9698.ts

diff --git a/.changeset/swift-hairs-bow.md b/.changeset/swift-hairs-bow.md
new file mode 100644
index 00000000000..4213e24b041
--- /dev/null
+++ b/.changeset/swift-hairs-bow.md
@@ -0,0 +1,6 @@
+---
+swc_fast_ts_strip: patch
+swc_core: patch
+---
+
+fix(es/typescript): Handle multiline type parameters in async arrow functions
diff --git a/crates/swc_fast_ts_strip/src/lib.rs b/crates/swc_fast_ts_strip/src/lib.rs
index d7a7f6dfead..3d09d2bddd5 100644
--- a/crates/swc_fast_ts_strip/src/lib.rs
+++ b/crates/swc_fast_ts_strip/src/lib.rs
@@ -555,6 +555,34 @@ impl Visit for TsStrip {
     }
 
     fn visit_arrow_expr(&mut self, n: &ArrowExpr) {
+        #[inline(always)]
+        fn is_new_line(c: char) -> bool {
+            matches!(c, '\u{000A}' | '\u{000D}' | '\u{2028}' | '\u{2029}')
+        }
+
+        'type_params: {
+            if let Some(tp) = &n.type_params {
+                self.add_replacement(tp.span);
+
+                if !n.is_async {
+                    break 'type_params;
+                }
+
+                let slice = self.get_src_slice(tp.span);
+                if !slice.chars().any(is_new_line) {
+                    break 'type_params;
+                }
+
+                let l_paren = self.get_next_token(tp.span.hi);
+                debug_assert_eq!(l_paren.token, Token::LParen);
+                let l_paren_pos = l_paren.span.lo;
+                let l_lt_pos = tp.span.lo;
+
+                self.add_overwrite(l_paren_pos, b' ');
+                self.add_overwrite(l_lt_pos, b'(');
+            }
+        }
+
         if let Some(ret) = &n.return_type {
             self.add_replacement(ret.span);
 
@@ -565,10 +593,7 @@ impl Visit for TsStrip {
             let span = span(r_paren.span.lo, arrow.span.lo);
 
             let slice = self.get_src_slice(span);
-            if slice
-                .chars()
-                .any(|c| matches!(c, '\u{000A}' | '\u{000D}' | '\u{2028}' | '\u{2029}'))
-            {
+            if slice.chars().any(is_new_line) {
                 self.add_replacement(r_paren.span);
 
                 // Instead of moving the arrow mark, we shift the right parenthesis to the next
@@ -597,7 +622,6 @@ impl Visit for TsStrip {
             }
         }
 
-        n.type_params.visit_with(self);
         n.params.visit_with(self);
         n.body.visit_with(self);
     }
diff --git a/crates/swc_fast_ts_strip/tests/fixture/issue-9698.js b/crates/swc_fast_ts_strip/tests/fixture/issue-9698.js
new file mode 100644
index 00000000000..c59c0d0a427
--- /dev/null
+++ b/crates/swc_fast_ts_strip/tests/fixture/issue-9698.js
@@ -0,0 +1,9 @@
+let f = async (
+     
+  v   ) => v;
+
+let g = async (
+     
+  v    
+                 ) => 
+        v;
\ No newline at end of file
diff --git a/crates/swc_fast_ts_strip/tests/fixture/issue-9698.transform.js b/crates/swc_fast_ts_strip/tests/fixture/issue-9698.transform.js
new file mode 100644
index 00000000000..324e3286728
--- /dev/null
+++ b/crates/swc_fast_ts_strip/tests/fixture/issue-9698.transform.js
@@ -0,0 +1,2 @@
+let f = async (v)=>v;
+let g = async (v)=>v;
diff --git a/crates/swc_fast_ts_strip/tests/fixture/issue-9698.ts b/crates/swc_fast_ts_strip/tests/fixture/issue-9698.ts
new file mode 100644
index 00000000000..f544b2234e5
--- /dev/null
+++ b/crates/swc_fast_ts_strip/tests/fixture/issue-9698.ts
@@ -0,0 +1,9 @@
+let f = async <
+    T
+>(v: T) => v;
+
+let g = async <
+    T
+>(v: T)
+    : Promise<any> => 
+        v;
\ No newline at end of file