reject invalid `for await` syntax (#4847)

3 files changed, 16 insertions, 1 deletions

diff --git a/lib/parse.js b/lib/parse.js
index bc13b60e..323769a2 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -1189,7 +1189,7 @@ function parse($TEXT, options) {
         var await = is("name", "await") && next();
         expect("(");
         var init = null;
-        if (!is("punc", ";")) {
+        if (await || !is("punc", ";")) {
             init = is("keyword", "const")
                 ? (next(), const_(true))
                 : is("keyword", "let")
diff --git a/test/input/invalid/for-await.js b/test/input/invalid/for-await.js
new file mode 100644
index 00000000..13e07607
--- /dev/null
+++ b/test/input/invalid/for-await.js
@@ -0,0 +1 @@
+for await (; console.log(42););
diff --git a/test/mocha/cli.js b/test/mocha/cli.js
index 4d4972ec..5b84eba6 100644
--- a/test/mocha/cli.js
+++ b/test/mocha/cli.js
@@ -679,6 +679,20 @@ describe("bin/uglifyjs", function() {
             done();
         });
     });
+    it("Should throw syntax error (for-await)", function(done) {
+        var command = uglifyjscmd + " test/input/invalid/for-await.js";
+        exec(command, function(err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(stdout, "");
+            assert.strictEqual(stderr.split(/\n/).slice(0, 4).join("\n"), [
+                "Parse error at test/input/invalid/for-await.js:1,11",
+                "for await (; console.log(42););",
+                "           ^",
+                "ERROR: Unexpected token: punc «;»",
+            ].join("\n"));
+            done();
+        });
+    });
     it("Should throw syntax error (switch defaults)", function(done) {
         var command = uglifyjscmd + " test/input/invalid/switch.js";
         exec(command, function(err, stdout, stderr) {