fix

crates/swc_ecma_minifier/src/compress/pure/dead_code.rs

@@ -6,7 +6,11 @@ use swc_ecma_utils::{extract_var_ids, ExprExt, StmtExt, StmtLike, Value};
 use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
 
 use super::Pure;
-use crate::{compress::util::is_fine_for_if_cons, maybe_par, util::ModuleItemExt};
+use crate::{
+    compress::util::is_fine_for_if_cons,
+    maybe_par,
+    util::{contains_await_or_yield, ModuleItemExt},
+};
 
 /// Methods related to option `dead_code`.
 impl Pure<'_> {
@@ -285,6 +289,10 @@ impl Pure<'_> {
             _ => return,
         };
 
+        if contains_await_or_yield(last) {
+            return;
+        }
+
         fn drop<T: StmtLike>(stmt: &mut T, last: &Stmt, need_break: bool) -> bool {
             match stmt.as_stmt_mut() {
                 Some(s) if s.eq_ignore_span(last) => {

crates/swc_ecma_minifier/src/util/mod.rs

@@ -249,6 +249,50 @@ impl Visit for LeapFinder {
     }
 }
 
+#[allow(unused)]
+pub(crate) fn contains_await_or_yield<N>(n: &N) -> bool
+where
+    N: VisitWith<YieldOrAwaitFinder>,
+{
+    let mut v = YieldOrAwaitFinder::default();
+    n.visit_with(&mut v);
+    v.found_yield || v.found_await
+}
+
+#[derive(Default)]
+pub(crate) struct YieldOrAwaitFinder {
+    found_await: bool,
+    found_yield: bool,
+}
+
+impl Visit for YieldOrAwaitFinder {
+    noop_visit_type!();
+
+    fn visit_arrow_expr(&mut self, _: &ArrowExpr) {}
+
+    fn visit_await_expr(&mut self, n: &AwaitExpr) {
+        n.visit_children_with(self);
+
+        self.found_await = true;
+    }
+
+    fn visit_class_method(&mut self, _: &ClassMethod) {}
+
+    fn visit_constructor(&mut self, _: &Constructor) {}
+
+    fn visit_function(&mut self, _: &Function) {}
+
+    fn visit_getter_prop(&mut self, _: &GetterProp) {}
+
+    fn visit_setter_prop(&mut self, _: &SetterProp) {}
+
+    fn visit_yield_expr(&mut self, n: &YieldExpr) {
+        n.visit_children_with(self);
+
+        self.found_yield = true;
+    }
+}
+
 /// This method returns true only if `T` is `var`. (Not `const` or `let`)
 pub(crate) fn is_hoisted_var_decl_without_init<T>(t: &T) -> bool
 where