fix corner case in `unused` (#4993)

fixes #4992

2 files changed, 33 insertions, 17 deletions

diff --git a/lib/compress.js b/lib/compress.js
index b20a41e5..73cc2df5 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1029,12 +1029,12 @@ merge(Compressor.prototype, {
                 if (prop.key instanceof AST_Node) prop.key.walk(tw);
                 return prop.value;
             }).forEach(function(prop) {
-                if (prop.static && (prop.value instanceof AST_Lambda || !prop.value.contains_this())) {
-                    prop.value.walk(tw);
-                } else {
+                if (!prop.static || prop instanceof AST_ClassField && prop.value.contains_this()) {
                     push(tw);
                     prop.value.walk(tw);
                     pop(tw);
+                } else {
+                    prop.value.walk(tw);
                 }
             });
             return true;
@@ -6185,12 +6185,6 @@ merge(Compressor.prototype, {
                     }
                     return true;
                 }
-            } else if (node instanceof AST_This && scope instanceof AST_DefClass) {
-                var def = scope.name.definition();
-                if (!(def.id in in_use_ids)) {
-                    in_use_ids[def.id] = true;
-                    in_use.push(def);
-                }
             }
             return scan_ref_scoped(node, descend, true);
         });
@@ -7703,10 +7697,9 @@ merge(Compressor.prototype, {
             for (var i = 0; i < props.length; i++) {
                 var prop = props[i];
                 if (prop.key instanceof AST_Node) exprs.push(prop.key);
-                if (prop instanceof AST_ClassField
-                    && prop.static
-                    && prop.value
-                    && !(prop.value instanceof AST_Lambda)) {
+                if (prop.static && prop.value
+                    && prop instanceof AST_ClassField
+                    && prop.value.has_side_effects(compressor)) {
                     if (prop.value.contains_this()) return this;
                     values.push(prop.value);
                 }
diff --git a/test/compress/classes.js b/test/compress/classes.js
index cbecf669..f9797022 100644
--- a/test/compress/classes.js
+++ b/test/compress/classes.js
@@ -973,9 +973,9 @@ issue_4681: {
     }
     expect: {
         console.log(function(a) {
-            class A {
+            (class {
                 static p = a = this;
-            }
+            });
             return typeof a;
         }());
     }
@@ -1399,9 +1399,9 @@ issue_4821_1: {
     }
     expect: {
         var a;
-        class A {
+        (class {
             static p = void (a = this);
-        }
+        });
         console.log(typeof a);
     }
     expect_stdout: "function"
@@ -1725,3 +1725,26 @@ issue_4982_2: {
     expect_stdout: "PASS"
     node_version: ">=12"
 }
+
+issue_4992: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        class A {
+            static P = this;
+            get p() {}
+        }
+        console.log(typeof A.P);
+    }
+    expect: {
+        console.log(typeof class {
+            static P = this;
+            get p() {}
+        }.P);
+    }
+    expect_stdout: "function"
+    node_version: ">=12"
+}