minor clean-ups (#5300)

Author: alexlamsl

lib/compress.js

@@ -2530,7 +2530,7 @@ Compressor.prototype.compress = function(node) {
                         }
                         if (names.has(sym.name)) continue;
                         names.set(sym.name, true);
-                        if (value) arg = !arg || is_undefined(arg) ? value : null;
+                        if (value) arg = is_undefined(arg) ? value : null;
                         if (!arg && !value) {
                             arg = make_node(AST_Undefined, sym).transform(compressor);
                         } else if (arg instanceof AST_Lambda && arg.pinned()) {
@@ -3423,18 +3423,14 @@ Compressor.prototype.compress = function(node) {
                 return false;
             }
 
-            function is_return_void(value) {
-                return !value || value instanceof AST_UnaryPrefix && value.operator == "void";
-            }
-
             function match_target(target) {
                 return last_of(compressor, function(node) {
                     return node === target;
                 });
             }
 
             function can_drop_abort(ab) {
-                if (ab instanceof AST_Return) return in_lambda && is_return_void(ab.value);
+                if (ab instanceof AST_Return) return in_lambda && is_undefined(ab.value);
                 if (!(ab instanceof AST_LoopControl)) return false;
                 var lct = compressor.loopcontrol_target(ab);
                 if (ab instanceof AST_Continue) return match_target(loop_body(lct));
@@ -3481,9 +3477,7 @@ Compressor.prototype.compress = function(node) {
                     block = last.body;
                 }
                 block.pop();
-                if (ab.value) block.push(make_node(AST_SimpleStatement, ab.value, {
-                    body: ab.value.expression
-                }));
+                if (ab.value) block.push(make_node(AST_SimpleStatement, ab.value, { body: ab.value }));
                 return body;
             }
 
@@ -4000,7 +3994,8 @@ Compressor.prototype.compress = function(node) {
     }
 
     function is_undefined(node, compressor) {
-        return node.is_undefined
+        return node == null
+            || node.is_undefined
             || node instanceof AST_Undefined
             || node instanceof AST_UnaryPrefix
                 && node.operator == "void"
@@ -9915,7 +9910,7 @@ Compressor.prototype.compress = function(node) {
             if (argname instanceof AST_DefaultValue) {
                 if (!has_default) has_default = 1;
                 var arg = has_default == 1 && self.args[index];
-                if (arg && !is_undefined(arg)) has_default = 2;
+                if (!is_undefined(arg)) has_default = 2;
                 if (has_arg_refs(fn, argname.value)) return false;
                 argname = argname.name;
             }
@@ -13176,7 +13171,6 @@ Compressor.prototype.compress = function(node) {
             if (!no_return) {
                 if (async) scan_local_returns(inlined, function(node) {
                     var value = node.value;
-                    if (!value) return;
                     if (is_undefined(value)) return;
                     node.value = make_node(AST_Await, call, { expression: value });
                 });
@@ -13320,10 +13314,7 @@ Compressor.prototype.compress = function(node) {
             if (!no_return) scan_local_returns(inlined, function(node) {
                 node.in_bool = false;
                 var value = node.value;
-                if (op == "void") {
-                    if (!value) return;
-                    if (is_undefined(value)) return;
-                }
+                if (op == "void" && is_undefined(value)) return;
                 node.value = make_node(AST_UnaryPrefix, self, {
                     operator: op,
                     expression: value || make_node(AST_Undefined, node).transform(compressor),
@@ -13371,8 +13362,7 @@ Compressor.prototype.compress = function(node) {
 
     OPT(AST_Return, function(self, compressor) {
         var value = self.value;
-        if (compressor.option("side_effects")
-            && value
+        if (value && compressor.option("side_effects")
             && is_undefined(value, compressor)
             && !in_async_generator(compressor.find_parent(AST_Scope))) {
             self.value = null;

test/compress/let.js

@@ -1639,7 +1639,7 @@ issue_4438: {
                 ;
             else {
                 let a = console.log;
-                a("PASS");
+                void a("PASS");
             }
         }
         f();