extend `join_vars` & `sequences` (#2798)

1 files changed, 49 insertions, 39 deletions

diff --git a/lib/compress.js b/lib/compress.js
index cd5651a2..5fd49cf1 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1662,37 +1662,34 @@ merge(Compressor.prototype, {
             for (var i = 0; i < statements.length; i++) {
                 var stat = statements[i];
                 if (prev) {
-                    if (stat instanceof AST_For && !(stat.init instanceof AST_Definitions)) {
-                        var abort = false;
-                        prev.body.walk(new TreeWalker(function(node) {
-                            if (abort || node instanceof AST_Scope) return true;
-                            if (node instanceof AST_Binary && node.operator == "in") {
-                                abort = true;
-                                return true;
-                            }
-                        }));
-                        if (!abort) {
-                            if (stat.init) stat.init = cons_seq(stat.init);
-                            else {
-                                stat.init = prev.body;
-                                n--;
-                                CHANGED = true;
+                    if (stat instanceof AST_Exit) {
+                        stat.value = cons_seq(stat.value || make_node(AST_Undefined, stat).transform(compressor));
+                    } else if (stat instanceof AST_For) {
+                        if (!(stat.init instanceof AST_Definitions)) {
+                            var abort = false;
+                            prev.body.walk(new TreeWalker(function(node) {
+                                if (abort || node instanceof AST_Scope) return true;
+                                if (node instanceof AST_Binary && node.operator == "in") {
+                                    abort = true;
+                                    return true;
+                                }
+                            }));
+                            if (!abort) {
+                                if (stat.init) stat.init = cons_seq(stat.init);
+                                else {
+                                    stat.init = prev.body;
+                                    n--;
+                                    CHANGED = true;
+                                }
                             }
                         }
-                    }
-                    else if (stat instanceof AST_If) {
+                    } else if (stat instanceof AST_ForIn) {
+                        stat.object = cons_seq(stat.object);
+                    } else if (stat instanceof AST_If) {
                         stat.condition = cons_seq(stat.condition);
-                    }
-                    else if (stat instanceof AST_With) {
+                    } else if (stat instanceof AST_Switch) {
                         stat.expression = cons_seq(stat.expression);
-                    }
-                    else if (stat instanceof AST_Exit && stat.value) {
-                        stat.value = cons_seq(stat.value);
-                    }
-                    else if (stat instanceof AST_Exit) {
-                        stat.value = cons_seq(make_node(AST_Undefined, stat).transform(compressor));
-                    }
-                    else if (stat instanceof AST_Switch) {
+                    } else if (stat instanceof AST_With) {
                         stat.expression = cons_seq(stat.expression);
                     }
                 }
@@ -1775,18 +1772,7 @@ merge(Compressor.prototype, {
                         defs = stat;
                     }
                 } else if (stat instanceof AST_Exit) {
-                    var exprs = join_object_assignments(prev, stat.value);
-                    if (exprs) {
-                        CHANGED = true;
-                        if (exprs.length) {
-                            stat.value = make_sequence(stat.value, exprs);
-                        } else if (stat.value instanceof AST_Sequence) {
-                            stat.value = stat.value.tail_node().left;
-                        } else {
-                            stat.value = stat.value.left;
-                        }
-                    }
-                    statements[++j] = stat;
+                    stat.value = extract_object_assignments(stat.value);
                 } else if (stat instanceof AST_For) {
                     var exprs = join_object_assignments(prev, stat.init);
                     if (exprs) {
@@ -1808,6 +1794,10 @@ merge(Compressor.prototype, {
                     } else {
                         statements[++j] = stat;
                     }
+                } else if (stat instanceof AST_ForIn) {
+                    stat.object = extract_object_assignments(stat.object);
+                } else if (stat instanceof AST_If) {
+                    stat.condition = extract_object_assignments(stat.condition);
                 } else if (stat instanceof AST_SimpleStatement) {
                     var exprs = join_object_assignments(prev, stat.body);
                     if (exprs) {
@@ -1816,11 +1806,31 @@ merge(Compressor.prototype, {
                         stat.body = make_sequence(stat.body, exprs);
                     }
                     statements[++j] = stat;
+                } else if (stat instanceof AST_Switch) {
+                    stat.expression = extract_object_assignments(stat.expression);
+                } else if (stat instanceof AST_With) {
+                    stat.expression = extract_object_assignments(stat.expression);
                 } else {
                     statements[++j] = stat;
                 }
             }
             statements.length = j + 1;
+
+            function extract_object_assignments(value) {
+                statements[++j] = stat;
+                var exprs = join_object_assignments(prev, value);
+                if (exprs) {
+                    CHANGED = true;
+                    if (exprs.length) {
+                        return make_sequence(value, exprs);
+                    } else if (value instanceof AST_Sequence) {
+                        return value.tail_node().left;
+                    } else {
+                        return value.left;
+                    }
+                }
+                return value;
+            }
         }
     }