fix typeof side effects (#1696)

`statement_to_expression()` drops `typeof` even if it operates on undeclared variables.

Since we now have `drop_side_effect_free()`, replace and remove this deprecated functionality.

1 files changed, 11 insertions, 20 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 9ed368c7..03c8d5dd 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -482,15 +482,6 @@ merge(Compressor.prototype, {
         return x;
     };
 
-    var readOnlyPrefix = makePredicate("! ~ + - void typeof");
-    function statement_to_expression(stat) {
-        if (stat.body instanceof AST_UnaryPrefix && readOnlyPrefix(stat.body.operator)) {
-            return stat.body.expression;
-        } else {
-            return stat.body;
-        }
-    }
-
     function is_iife_call(node) {
         if (node instanceof AST_Call && !(node instanceof AST_New)) {
             return node.expression instanceof AST_Function || is_iife_call(node.expression);
@@ -984,10 +975,10 @@ merge(Compressor.prototype, {
             };
             statements.forEach(function(stat){
                 if (stat instanceof AST_SimpleStatement) {
-                    if (seqLength(seq) >= compressor.sequences_limit) {
-                        push_seq();
-                    }
-                    seq.push(seq.length > 0 ? statement_to_expression(stat) : stat.body);
+                    if (seqLength(seq) >= compressor.sequences_limit) push_seq();
+                    var body = stat.body;
+                    if (seq.length > 0) body = body.drop_side_effect_free(compressor);
+                    if (body) seq.push(body);
                 } else {
                     push_seq();
                     ret.push(stat);
@@ -1036,7 +1027,7 @@ merge(Compressor.prototype, {
                                 stat.init = cons_seq(stat.init);
                             }
                             else if (!stat.init) {
-                                stat.init = statement_to_expression(prev);
+                                stat.init = prev.body.drop_side_effect_free(compressor);
                                 ret.pop();
                             }
                         } catch(ex) {
@@ -2170,6 +2161,7 @@ merge(Compressor.prototype, {
             switch (this.operator) {
               case "&&":
               case "||":
+                if (right === this.right) return this;
                 var node = this.clone();
                 node.right = right;
                 return node;
@@ -2423,8 +2415,8 @@ merge(Compressor.prototype, {
             return make_node(AST_SimpleStatement, self, {
                 body: make_node(AST_Conditional, self, {
                     condition   : self.condition,
-                    consequent  : statement_to_expression(self.body),
-                    alternative : statement_to_expression(self.alternative)
+                    consequent  : self.body.body,
+                    alternative : self.alternative.body
                 })
             }).optimize(compressor);
         }
@@ -2440,25 +2432,24 @@ merge(Compressor.prototype, {
                 body: make_node(AST_Binary, self, {
                     operator : "||",
                     left     : negated,
-                    right    : statement_to_expression(self.body)
+                    right    : self.body.body
                 })
             }).optimize(compressor);
             return make_node(AST_SimpleStatement, self, {
                 body: make_node(AST_Binary, self, {
                     operator : "&&",
                     left     : self.condition,
-                    right    : statement_to_expression(self.body)
+                    right    : self.body.body
                 })
             }).optimize(compressor);
         }
         if (self.body instanceof AST_EmptyStatement
-            && self.alternative
             && self.alternative instanceof AST_SimpleStatement) {
             return make_node(AST_SimpleStatement, self, {
                 body: make_node(AST_Binary, self, {
                     operator : "||",
                     left     : self.condition,
-                    right    : statement_to_expression(self.alternative)
+                    right    : self.alternative.body
                 })
             }).optimize(compressor);
         }