fix corner case

add test

lib/compress.js

@@ -1677,10 +1677,9 @@ merge(Compressor.prototype, {
                 } else if (stat instanceof AST_For) {
                     if (prev instanceof AST_Var && (!stat.init || stat.init.TYPE == prev.TYPE)) {
                         if (stat.init) {
-                            stat.init.definitions = prev.definitions.concat(stat.init.definitions);
+                            prev.definitions = prev.definitions.concat(stat.init.definitions);
-                        } else {
-                            stat.init = prev;
                         }
+                        stat.init = prev;
                         statements[j] = stat;
                         CHANGED = true;
                     } else if (defs && stat.init && defs.TYPE == stat.init.TYPE && declarations_only(stat.init)) {

test/compress/sequences.js

@@ -833,3 +833,29 @@ hoist_decl: {
         for (y(); 0;) z();
     }
 }
+
+for_init_var: {
+    options = {
+        join_vars: true,
+        unused: false,
+    }
+    input: {
+        var a = "PASS";
+        (function() {
+            var b = 42;
+            for (var c = 5; c > 0;) c--;
+            a = "FAIL";
+            var a;
+        })();
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        (function() {
+            for (var b = 42, c = 5, a; c > 0;) c--;
+            a = "FAIL";
+        })();
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+}