enhance unused (#4858)

test/compress/classes.js

@@ -1541,3 +1541,23 @@ issue_4848: {
     expect_stdout: "PASS"
     node_version: ">=4"
 }
+
+drop_unused_self_reference: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        class A {}
+        (A.p = A).q = console.log("PASS");
+    }
+    expect: {
+        "use strict";
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}

test/compress/functions.js

@@ -6021,3 +6021,20 @@ issue_4823: {
     }
     expect_stdout: "function"
 }
+
+drop_unused_self_reference: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {}
+        (f.p = f).q = console.log("PASS");
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}

test/ufuzz/index.js

@@ -1796,7 +1796,7 @@ function createClassLiteral(recurmax, stmtDepth, canThrow, name) {
         if (SUPPORT.class_field && rng(2)) {
             s += internal || createObjectKey(recurmax, stmtDepth, canThrow);
             if (rng(5)) {
-                async = bug_async_class_await && fixed;
+                async = bug_async_class_await && fixed && 0;
                 generator = false;
                 s += " = " + createExpression(recurmax, NO_COMMA, stmtDepth, fixed ? canThrow : CANNOT_THROW);
                 generator = save_generator;
@@ -2000,7 +2000,7 @@ function isBannedKeyword(name) {
       case "arguments":
         return in_class;
       case "await":
-        return async;
+        return async !== false;
       case "yield":
         return generator || in_class;
     }