fix `delete` corner cases (#1799)

- assignment
- boolean
- conditional
- sequence

1 files changed, 39 insertions, 23 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 03b1fefb..de0ff387 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -481,15 +481,15 @@ merge(Compressor.prototype, {
     // func(something) because that changes the meaning of
     // the func (becomes lexical instead of global).
     function maintain_this_binding(parent, orig, val) {
-        if (parent instanceof AST_Call && parent.expression === orig) {
-            if (val instanceof AST_PropAccess || val instanceof AST_SymbolRef && val.name === "eval") {
-                return make_node(AST_Seq, orig, {
-                    car: make_node(AST_Number, orig, {
-                        value: 0
-                    }),
-                    cdr: val
-                });
-            }
+        if (parent instanceof AST_UnaryPrefix && parent.operator == "delete"
+            || parent instanceof AST_Call && parent.expression === orig
+                && (val instanceof AST_PropAccess || val instanceof AST_SymbolRef && val.name == "eval")) {
+            return make_node(AST_Seq, orig, {
+                car: make_node(AST_Number, orig, {
+                    value: 0
+                }),
+                cdr: val
+            });
         }
         return val;
     }
@@ -3103,11 +3103,27 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_UnaryPrefix, function(self, compressor){
+        var e = self.expression;
+        if (self.operator == "delete"
+            && !(e instanceof AST_SymbolRef
+                || e instanceof AST_PropAccess
+                || e instanceof AST_NaN
+                || e instanceof AST_Infinity
+                || e instanceof AST_Undefined)) {
+            if (e instanceof AST_Seq) {
+                e = e.to_array();
+                e.push(make_node(AST_True, self));
+                return AST_Seq.from_array(e).optimize(compressor);
+            }
+            return make_node(AST_Seq, self, {
+                car: e,
+                cdr: make_node(AST_True, self)
+            }).optimize(compressor);
+        }
         var seq = self.lift_sequences(compressor);
         if (seq !== self) {
             return seq;
         }
-        var e = self.expression;
         if (compressor.option("side_effects") && self.operator == "void") {
             e = e.drop_side_effect_free(compressor);
             if (e) {
@@ -3606,6 +3622,14 @@ merge(Compressor.prototype, {
         return self;
     });
 
+    function in_delete(parent) {
+        return parent instanceof AST_UnaryPrefix && parent.operator == "delete";
+    }
+
+    function is_atomic(parent, self) {
+        return parent.expression instanceof AST_SymbolRef || parent.expression.TYPE === self.TYPE;
+    }
+
     OPT(AST_Undefined, function(self, compressor){
         if (compressor.option("unsafe")) {
             var undef = find_variable(compressor, "undefined");
@@ -3620,10 +3644,7 @@ merge(Compressor.prototype, {
             }
         }
         var parent = compressor.parent();
-        if (parent instanceof AST_UnaryPrefix
-            && parent.operator == "delete"
-            && (parent.expression instanceof AST_SymbolRef
-                || parent.expression.TYPE === self.TYPE)) return self;
+        if (in_delete(parent) && is_atomic(parent, self)) return self;
         return make_node(AST_UnaryPrefix, self, {
             operator: "void",
             expression: make_node(AST_Number, self, {
@@ -3634,12 +3655,10 @@ merge(Compressor.prototype, {
 
     OPT(AST_Infinity, function(self, compressor){
         var parent = compressor.parent();
-        if (parent instanceof AST_UnaryPrefix
-            && parent.operator == "delete"
-            && (parent.expression instanceof AST_SymbolRef
-                || parent.expression.TYPE === self.TYPE))
-            return self;
+        var del = in_delete(parent);
+        if (del && is_atomic(parent, self)) return self;
         if (compressor.option("keep_infinity")
+            && !(del && !is_atomic(parent, self))
             && !find_variable(compressor, "Infinity"))
             return self;
         return make_node(AST_Binary, self, {
@@ -3655,10 +3674,7 @@ merge(Compressor.prototype, {
 
     OPT(AST_NaN, function(self, compressor){
         var parent = compressor.parent();
-        if (parent instanceof AST_UnaryPrefix
-                && parent.operator == "delete"
-                && !(parent.expression instanceof AST_SymbolRef
-                    || parent.expression.TYPE === self.TYPE)
+        if (in_delete(parent) && !is_atomic(parent, self)
             || find_variable(compressor, "NaN")) {
             return make_node(AST_Binary, self, {
                 operator: "/",