From 293413fe71bded44176c70721ec1b76f36bea295 Mon Sep 17 00:00:00 2001
From: Dunqing <29533304+Dunqing@users.noreply.github.com>
Date: Mon, 26 Aug 2024 03:30:16 +0000
Subject: [PATCH] fix(semantic): implicit return `UpdateExpression` in
 `ArrowFunctionExpression` does not as read reference (#5161)

close: #5158
close: #5156
---
 crates/oxc_semantic/src/builder.rs            | 14 ++++-
 .../oxc_semantic/tests/integration/symbols.rs | 54 +++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/crates/oxc_semantic/src/builder.rs b/crates/oxc_semantic/src/builder.rs
index 5c68400be..74f4fa777 100644
--- a/crates/oxc_semantic/src/builder.rs
+++ b/crates/oxc_semantic/src/builder.rs
@@ -2013,7 +2013,19 @@ impl<'a> SemanticBuilder<'a> {
         for node in self.nodes.iter_parents(self.current_node_id).skip(1) {
             return match node.kind() {
                 AstKind::ParenthesizedExpression(_) => continue,
-                AstKind::ExpressionStatement(_) => false,
+                AstKind::ExpressionStatement(_) => {
+                    if self.current_scope_flags().is_arrow() {
+                        if let Some(node) = self.nodes.iter_parents(node.id()).nth(2) {
+                            // (x) => x++
+                            //        ^^^ implicit return, we need to treat `x` as a read reference
+                            if matches!(node.kind(), AstKind::ArrowFunctionExpression(arrow) if arrow.expression)
+                            {
+                                return true;
+                            }
+                        }
+                    }
+                    false
+                }
                 _ => true,
             };
         }
diff --git a/crates/oxc_semantic/tests/integration/symbols.rs b/crates/oxc_semantic/tests/integration/symbols.rs
index baef2aa92..76a061b5f 100644
--- a/crates/oxc_semantic/tests/integration/symbols.rs
+++ b/crates/oxc_semantic/tests/integration/symbols.rs
@@ -372,3 +372,57 @@ fn test_ts_interface_heritage() {
     .has_number_of_references(1)
     .test();
 }
+
+#[test]
+fn test_arrow_implicit_return() {
+    SemanticTester::js("let i = 0; const x = () => i")
+        .has_root_symbol("i")
+        .has_number_of_reads(1)
+        .has_number_of_writes(0)
+        .test();
+
+    SemanticTester::js("let i = 0; const x = () => ++i")
+        .has_root_symbol("i")
+        .has_number_of_reads(1)
+        .has_number_of_writes(1)
+        .test();
+
+    SemanticTester::js("let i = 0; const x = () => { ++i }")
+        .has_root_symbol("i")
+        .has_number_of_reads(0)
+        .has_number_of_writes(1)
+        .test();
+
+    SemanticTester::js("let i = 0; const x = () => (0, ++i)")
+        .has_root_symbol("i")
+        .has_number_of_reads(1)
+        .has_number_of_writes(1)
+        .test();
+
+    SemanticTester::js("let i = 0; const x = () => (++i, 0)")
+        .has_root_symbol("i")
+        .has_number_of_reads(1)
+        .has_number_of_writes(1)
+        .test();
+
+    SemanticTester::js("let i = 1; const foo = () => () => { i++ }")
+        .has_root_symbol("i")
+        .has_number_of_reads(0)
+        .has_number_of_writes(1)
+        .test();
+}
+
+#[test]
+fn test_arrow_explicit_return() {
+    SemanticTester::js("let i = 0; const x = () => { return i }")
+        .has_root_symbol("i")
+        .has_number_of_reads(1)
+        .has_number_of_writes(0)
+        .test();
+
+    SemanticTester::js("let i = 0; const x = () => { return ++i }")
+        .has_root_symbol("i")
+        .has_number_of_reads(1)
+        .has_number_of_writes(1)
+        .test();
+}