fix corner case in inline & module (#5492)

fixes #5491

lib/compress.js

@@ -9958,9 +9958,12 @@ Compressor.prototype.compress = function(node) {
         }) : arg);
     }
 
-    function avoid_await_yield(parent_scope) {
+    function avoid_await_yield(compressor, parent_scope) {
+        if (!parent_scope) parent_scope = compressor.find_parent(AST_Scope);
         var avoid = [];
-        if (is_async(parent_scope)) avoid.push("await");
+        if (is_async(parent_scope) || parent_scope instanceof AST_Toplevel && compressor.option("module")) {
+            avoid.push("await");
+        }
         if (is_generator(parent_scope)) avoid.push("yield");
         return avoid.length && makePredicate(avoid);
     }
@@ -10322,7 +10325,7 @@ Compressor.prototype.compress = function(node) {
             if (exp === fn
                 && !fn.name
                 && (!value || value.is_constant_expression())
-                && safe_from_await_yield(fn, avoid_await_yield(compressor.find_parent(AST_Scope)))) {
+                && safe_from_await_yield(fn, avoid_await_yield(compressor))) {
                 return make_sequence(self, convert_args(value)).optimize(compressor);
             }
         }
@@ -10400,7 +10403,7 @@ Compressor.prototype.compress = function(node) {
                 && all(fn.body, is_empty)
                 && (fn === exp ? fn_name_unused(fn, compressor) : !has_default && !has_destructured && !fn.rest)
                 && !(is_arrow(fn) && fn.value)
-                && safe_from_await_yield(fn, avoid_await_yield(compressor.find_parent(AST_Scope)))) {
+                && safe_from_await_yield(fn, avoid_await_yield(compressor))) {
                 return make_sequence(self, convert_args()).optimize(compressor);
             }
         }
@@ -10559,7 +10562,7 @@ Compressor.prototype.compress = function(node) {
             })) return;
             var scope = compressor.find_parent(AST_Scope);
             var abort = false;
-            var avoid = avoid_await_yield(scope);
+            var avoid = avoid_await_yield(compressor, scope);
             var begin;
             var in_order = [];
             var side_effects = false;
@@ -10674,7 +10677,7 @@ Compressor.prototype.compress = function(node) {
             } while (!(scope instanceof AST_Scope));
             insert = scope.body.indexOf(child) + 1;
             if (!insert) return false;
-            if (!safe_from_await_yield(fn, avoid_await_yield(scope))) return false;
+            if (!safe_from_await_yield(fn, avoid_await_yield(compressor, scope))) return false;
             var safe_to_inject = (exp !== fn || fn.parent_scope.resolve() === scope) && !scope.pinned();
             if (scope instanceof AST_Toplevel) {
                 if (compressor.toplevel.vars) {
@@ -13074,7 +13077,7 @@ Compressor.prototype.compress = function(node) {
                     var arrow = !(value.uses_arguments || is_generator(value) || value.contains_this());
                     if (arrow) {
                         if (!scope) scope = compressor.find_parent(AST_Scope);
-                        var avoid = avoid_await_yield(scope);
+                        var avoid = avoid_await_yield(compressor, scope);
                         value.each_argname(function(argname) {
                             if (avoid[argname.name]) arrow = false;
                         });
@@ -13491,7 +13494,7 @@ Compressor.prototype.compress = function(node) {
                 }));
                 return !abort;
             })) return;
-            if (!safe_from_await_yield(fn, avoid_await_yield(scope))) return;
+            if (!safe_from_await_yield(fn, avoid_await_yield(compressor, scope))) return;
             fn.functions.each(function(def, name) {
                 scope.functions.set(name, def);
             });

test/mocha/minify.js

@@ -1,6 +1,7 @@
 var assert = require("assert");
 var readFileSync = require("fs").readFileSync;
 var run_code = require("../sandbox").run_code;
+var semver = require("semver");
 var UglifyJS = require("../..");
 
 function read(path) {
@@ -320,6 +321,24 @@ describe("minify", function() {
         });
     });
 
+    describe("module", function() {
+        it("Should not inline `await` variables", function() {
+            if (semver.satisfies(process.version, "<8")) return;
+            var code = [
+                "console.log(function() {",
+                "    return typeof await;",
+                "}());",
+            ].join("\n");
+            assert.strictEqual(run_code("(async function(){" + code + "})();"), "undefined\n");
+            var result = UglifyJS.minify(code, {
+                module: true,
+            });
+            if (result.error) throw result.error;
+            assert.strictEqual(result.code, "console.log(function(){return typeof await}());");
+            assert.strictEqual(run_code("(async function(){" + result.code + "})();"), "undefined\n");
+        });
+    });
+
     describe("rename", function() {
         it("Should be repeatable", function() {
             var code = "!function(x){return x(x)}(y);";

test/reduce.js

@@ -760,9 +760,9 @@ function compare_run_code(code, minify_options, result_cache, max_timeout) {
     if (minified.error) return minified;
 
     var toplevel = sandbox.has_toplevel(minify_options);
-    var unminified = run_code(code, toplevel, result_cache, max_timeout);
+    var unminified = run(code, max_timeout);
     var timeout = Math.min(100 * unminified.elapsed, max_timeout);
-    var minified_result = run_code(minified.code, toplevel, result_cache, timeout).result;
+    var minified_result = run(minified.code, timeout).result;
 
     if (sandbox.same_stdout(unminified.result, minified_result)) {
         return is_timed_out(unminified.result) && is_timed_out(minified_result) && {
@@ -774,6 +774,11 @@ function compare_run_code(code, minify_options, result_cache, max_timeout) {
         minified_result: minified_result,
         elapsed: unminified.elapsed,
     };
+
+    function run(code, timeout) {
+        if (minify_options.module) code = "(async function(){\n" + code + "\n})();";
+        return run_code(code, toplevel, result_cache, timeout);
+    }
 }
 
 function test_minify(code, minify_options) {

test/ufuzz/index.js

@@ -2517,8 +2517,11 @@ for (var round = 1; round <= num_iterations; round++) {
     })) continue;
     minify_options.forEach(function(options) {
         var o = JSON.parse(options);
+        if (async && has_await) {
+            o.module = true;
+            options = JSON.stringify(o);
+        }
         var toplevel = sandbox.has_toplevel(o);
-        if (async && has_await) o.parse = { module: true };
         o.validate = true;
         uglify_code = UglifyJS.minify(original_code, o);
         original_result = orig_result[toplevel ? 1 : 0];