enhance `reduce_vars` (#3843)

1 files changed, 45 insertions, 25 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 394184bc..8b6c38dd 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -607,7 +607,13 @@ merge(Compressor.prototype, {
         def(AST_Call, function(tw, descend) {
             tw.find_parent(AST_Scope).may_call_this();
             var exp = this.expression;
-            if (exp instanceof AST_SymbolRef) {
+            if (exp instanceof AST_Function) {
+                this.args.forEach(function(arg) {
+                    arg.walk(tw);
+                });
+                exp.walk(tw);
+                return true;
+            } else if (exp instanceof AST_SymbolRef) {
                 var def = exp.definition();
                 if (this.TYPE == "Call" && tw.in_boolean_context()) def.bool_fn++;
                 if (!(def.fixed instanceof AST_Defun)) return;
@@ -706,23 +712,20 @@ merge(Compressor.prototype, {
             return true;
         });
         def(AST_Function, function(tw, descend, compressor) {
-            var node = this;
-            node.inlined = false;
-            push(tw);
-            reset_variables(tw, compressor, node);
+            var fn = this;
+            fn.inlined = false;
             var iife;
-            if (!node.name
-                && (iife = tw.parent()) instanceof AST_Call
-                && iife.expression === node) {
+            if (!fn.name && (iife = tw.parent()) instanceof AST_Call && iife.expression === fn) {
+                reset_variables(tw, compressor, fn);
                 // Virtually turn IIFE parameters into variable definitions:
                 //   (function(a,b) {...})(c,d) => (function() {var a=c,b=d; ...})()
                 // So existing transformation rules can work on them.
-                node.argnames.forEach(function(arg, i) {
+                fn.argnames.forEach(function(arg, i) {
                     var d = arg.definition();
-                    if (d.fixed === undefined && (!node.uses_arguments || tw.has_directive("use strict"))) {
+                    if (d.fixed === undefined && (!fn.uses_arguments || tw.has_directive("use strict"))) {
                         var value = iife.args[i];
                         d.fixed = function() {
-                            var j = node.argnames.indexOf(arg);
+                            var j = fn.argnames.indexOf(arg);
                             if (j < 0) return value;
                             return iife.args[j] || make_node(AST_Undefined, iife);
                         };
@@ -732,10 +735,29 @@ merge(Compressor.prototype, {
                         d.fixed = false;
                     }
                 });
+                var has_return = false;
+                var visit = tw.visit;
+                tw.visit = function(node, descend) {
+                    var ret = visit.call(tw, node, descend);
+                    if (!has_return && node instanceof AST_Return && tw.find_parent(AST_Scope) === fn) {
+                        has_return = true;
+                        push(tw);
+                    }
+                    return ret;
+                };
+                descend();
+                tw.visit = visit;
+                var safe_ids = tw.safe_ids;
+                pop(tw);
+                walk_defuns(tw, fn);
+                if (!has_return) tw.safe_ids = safe_ids;
+            } else {
+                push(tw);
+                reset_variables(tw, compressor, fn);
+                descend();
+                pop(tw);
+                walk_defuns(tw, fn);
             }
-            descend();
-            pop(tw);
-            walk_defuns(tw, node);
             return true;
         });
         def(AST_If, function(tw) {
@@ -4512,17 +4534,15 @@ merge(Compressor.prototype, {
         }
 
         function scan_ref_scoped(node, descend, init) {
-            if (scope === self) {
-                if (node instanceof AST_Assign && node.left instanceof AST_SymbolRef) {
-                    var node_def = node.left.definition();
-                    if (node.operator != "=") chained[node_def.id] = true;
-                    match_assigns(node_def, node);
-                }
-                if (node instanceof AST_Unary && node.expression instanceof AST_SymbolRef) {
-                    var node_def = node.expression.definition();
-                    chained[node_def.id] = true;
-                    match_assigns(node_def, node);
-                }
+            if (node instanceof AST_Assign && node.left instanceof AST_SymbolRef) {
+                var node_def = node.left.definition();
+                if (node.operator != "=") chained[node_def.id] = true;
+                match_assigns(node_def, node);
+            }
+            if (node instanceof AST_Unary && node.expression instanceof AST_SymbolRef) {
+                var node_def = node.expression.definition();
+                chained[node_def.id] = true;
+                match_assigns(node_def, node);
             }
             var node_def, props = [], sym = assign_as_unused(node, props);
             if (sym && self.variables.get(sym.name) === (node_def = sym.definition())) {