enhance `reduce_vars` (#4392)

1 files changed, 56 insertions, 59 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 8fe0ad62..fa59ef5e 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -672,6 +672,53 @@ merge(Compressor.prototype, {
             return true;
         }
 
+        function reduce_iife(tw, descend, compressor) {
+            var fn = this;
+            fn.inlined = false;
+            var iife = tw.parent();
+            var hit = fn instanceof AST_AsyncFunction;
+            var aborts = false;
+            fn.walk(new TreeWalker(function(node) {
+                if (hit) return aborts = true;
+                if (node instanceof AST_Return) return hit = true;
+                if (node instanceof AST_Scope && node !== fn) return true;
+            }));
+            if (aborts) push(tw);
+            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.
+            var safe = !fn.uses_arguments || tw.has_directive("use strict");
+            fn.argnames.forEach(function(arg, i) {
+                var value = iife.args[i];
+                scan_declaration(tw, arg, function() {
+                    var j = fn.argnames.indexOf(arg);
+                    return (j < 0 ? value : iife.args[j]) || make_node(AST_Undefined, iife);
+                }, function(node, fixed) {
+                    var d = node.definition();
+                    if (safe && d.fixed === undefined) {
+                        mark(tw, d);
+                        tw.loop_ids[d.id] = tw.in_loop;
+                        var value = iife.args[i];
+                        d.fixed = fixed;
+                        d.fixed.assigns = [ arg ];
+                    } else {
+                        d.fixed = false;
+                    }
+                });
+            });
+            if (fn instanceof AST_Arrow && fn.value) {
+                fn.value.walk(tw);
+            } else {
+                walk_body(fn, tw);
+            }
+            var safe_ids = tw.safe_ids;
+            pop(tw);
+            walk_defuns(tw, fn);
+            if (!aborts) tw.safe_ids = safe_ids;
+            return true;
+        }
+
         def(AST_Assign, function(tw, descend, compressor) {
             var node = this;
             var left = node.left;
@@ -771,10 +818,14 @@ merge(Compressor.prototype, {
             tw.find_parent(AST_Scope).may_call_this();
             var exp = this.expression;
             if (is_function(exp)) {
+                var iife = !exp.name;
                 this.args.forEach(function(arg) {
                     arg.walk(tw);
+                    if (arg instanceof AST_Spread) iife = false;
                 });
+                if (iife) exp.reduce_vars = reduce_iife;
                 exp.walk(tw);
+                if (iife) delete exp.reduce_vars;
                 return true;
             } else if (exp instanceof AST_SymbolRef) {
                 var def = exp.definition();
@@ -861,62 +912,6 @@ merge(Compressor.prototype, {
             tw.in_loop = saved_loop;
             return true;
         });
-        def(AST_Function, function(tw, descend, compressor) {
-            var fn = this;
-            fn.inlined = false;
-            var iife;
-            if (!fn.name
-                && (iife = tw.parent()) instanceof AST_Call
-                && iife.expression === fn
-                && all(iife.args, function(arg) {
-                    return !(arg instanceof AST_Spread);
-                })) {
-                var hit = false;
-                var aborts = false;
-                fn.walk(new TreeWalker(function(node) {
-                    if (hit) return aborts = true;
-                    if (node instanceof AST_Return) return hit = true;
-                    if (node instanceof AST_Scope && node !== fn) return true;
-                }));
-                if (aborts) push(tw);
-                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.
-                var safe = !fn.uses_arguments || tw.has_directive("use strict");
-                fn.argnames.forEach(function(arg, i) {
-                    var value = iife.args[i];
-                    scan_declaration(tw, arg, function() {
-                        var j = fn.argnames.indexOf(arg);
-                        return (j < 0 ? value : iife.args[j]) || make_node(AST_Undefined, iife);
-                    }, function(node, fixed) {
-                        var d = node.definition();
-                        if (safe && d.fixed === undefined) {
-                            mark(tw, d);
-                            tw.loop_ids[d.id] = tw.in_loop;
-                            var value = iife.args[i];
-                            d.fixed = fixed;
-                            d.fixed.assigns = [ arg ];
-                        } else {
-                            d.fixed = false;
-                        }
-                    });
-                });
-                walk_body(fn, tw);
-                var safe_ids = tw.safe_ids;
-                pop(tw);
-                walk_defuns(tw, fn);
-                if (!aborts) tw.safe_ids = safe_ids;
-            } else {
-                push(tw);
-                reset_variables(tw, compressor, fn);
-                descend();
-                pop(tw);
-                if (fn.name) mark_escaped(tw, fn.name.definition(), fn, fn.name, fn, 0, 1);
-                walk_defuns(tw, fn);
-            }
-            return true;
-        });
         def(AST_If, function(tw) {
             this.condition.walk(tw);
             push(tw);
@@ -936,12 +931,14 @@ merge(Compressor.prototype, {
             return true;
         });
         def(AST_Lambda, function(tw, descend, compressor) {
-            this.inlined = false;
+            var fn = this;
+            fn.inlined = false;
             push(tw);
-            reset_variables(tw, compressor, this);
+            reset_variables(tw, compressor, fn);
             descend();
             pop(tw);
-            walk_defuns(tw, this);
+            if (fn.name) mark_escaped(tw, fn.name.definition(), fn, fn.name, fn, 0, 1);
+            walk_defuns(tw, fn);
             return true;
         });
         def(AST_Switch, function(tw, descend, compressor) {