enhance `join_vars` (#3783)

1 files changed, 32 insertions, 5 deletions

diff --git a/lib/compress.js b/lib/compress.js
index e5b7bf09..18cbd05e 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2338,10 +2338,7 @@ merge(Compressor.prototype, {
                 exprs = body.expressions.slice();
             }
             if (!exprs) return;
-            if (defn instanceof AST_Definitions) {
-                var def = defn.definitions[defn.definitions.length - 1];
-                if (trim_assigns(def.name, def.value, exprs)) return exprs;
-            }
+            var trimmed = false;
             for (var i = exprs.length - 1; --i >= 0;) {
                 var expr = exprs[i];
                 if (!(expr instanceof AST_Assign)) continue;
@@ -2349,8 +2346,38 @@ merge(Compressor.prototype, {
                 if (!(expr.left instanceof AST_SymbolRef)) continue;
                 var tail = exprs.slice(i + 1);
                 if (!trim_assigns(expr.left, expr.right, tail)) continue;
-                return exprs.slice(0, i + 1).concat(tail);
+                trimmed = true;
+                exprs = exprs.slice(0, i + 1).concat(tail);
             }
+            if (defn instanceof AST_Definitions) {
+                var def = defn.definitions[defn.definitions.length - 1];
+                if (trim_assigns(def.name, def.value, exprs)) trimmed = true;
+                if (join_var_assign(defn.definitions, exprs)) trimmed = true;
+            }
+            return trimmed && exprs;
+        }
+
+        function join_var_assign(definitions, exprs) {
+            var trimmed = false;
+            while (exprs.length) {
+                var expr = exprs[0];
+                if (!(expr instanceof AST_Assign)) break;
+                if (expr.operator != "=") break;
+                var lhs = expr.left;
+                if (!(lhs instanceof AST_SymbolRef)) break;
+                var def = lhs.definition();
+                if (def.scope !== scope) break;
+                var name = make_node(AST_SymbolVar, lhs, lhs);
+                definitions.push(make_node(AST_VarDef, expr, {
+                    name: name,
+                    value: expr.right
+                }));
+                def.orig.push(name);
+                def.replaced++;
+                exprs.shift();
+                trimmed = true;
+            }
+            return trimmed;
         }
 
         function trim_assigns(name, value, exprs) {