add test

test/compress/issue-1656.js

@@ -0,0 +1,45 @@
+f7: {
+    options = {
+        booleans: true,
+        cascade: true,
+        collapse_vars: true,
+        comparisons: true,
+        conditionals: true,
+        dead_code: true,
+        drop_debugger: true,
+        evaluate: true,
+        hoist_funs: true,
+        if_return: true,
+        join_vars: true,
+        loops: true,
+        negate_iife: true,
+        passes: 3,
+        properties: true,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    beautify = {
+        beautify: true,
+    }
+    input: {
+        var a = 100, b = 10;
+        function f22464() {
+            var brake146670 = 5;
+            while (((b = a) ? !a : ~a ? null : b += a) && --brake146670 > 0) {
+            }
+        }
+        f22464();
+        console.log(a, b);
+    }
+    expect_exact: [
+        "var a = 100, b = 10;",
+        "",
+        "!function() {",
+        "    for (;b = a, !1; ) ;",
+        "}(), console.log(a, b);",
+    ]
+    expect_stdout: true
+}