output optimal representations of NaN & Infinity (#1723)

- move these optimisations out from `Compressor` to `OutputStream`
- fixes behaviour inconsistency when running uglified code from global or module levels due to redefinition

2 files changed, 30 insertions, 22 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 3c0fc452..66a6a18b 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -413,18 +413,17 @@ merge(Compressor.prototype, {
                 value: val
             });
           case "number":
-            if (isNaN(val)) {
-                return make_node(AST_NaN, orig);
-            }
-
-            if ((1 / val) < 0) {
-                return make_node(AST_UnaryPrefix, orig, {
+            if (isNaN(val)) return make_node(AST_NaN, orig);
+            if (isFinite(val)) {
+                return 1 / val < 0 ? make_node(AST_UnaryPrefix, orig, {
                     operator: "-",
                     expression: make_node(AST_Number, orig, { value: -val })
-                });
+                }) : make_node(AST_Number, orig, { value: val });
             }
-
-            return make_node(AST_Number, orig, { value: val });
+            return val < 0 ? make_node(AST_UnaryPrefix, orig, {
+                operator: "-",
+                expression: make_node(AST_Infinity, orig)
+            }) : make_node(AST_Infinity, orig);
           case "boolean":
             return make_node(val ? AST_True : AST_False, orig);
           case "undefined":
@@ -3023,7 +3022,9 @@ merge(Compressor.prototype, {
             }
         }
         // avoids infinite recursion of numerals
-        if (self.operator != "-" || !(self.expression instanceof AST_Number)) {
+        if (self.operator != "-"
+            || !(self.expression instanceof AST_Number
+                || self.expression instanceof AST_Infinity)) {
             var ev = self.evaluate(compressor);
             if (ev !== self) {
                 ev = make_node_from_constant(ev, self).optimize(compressor);
@@ -3455,9 +3456,9 @@ merge(Compressor.prototype, {
               case "undefined":
                 return make_node(AST_Undefined, self).optimize(compressor);
               case "NaN":
-                return make_node(AST_NaN, self).optimize(compressor);
+                return make_node(AST_NaN, self);
               case "Infinity":
-                return make_node(AST_Infinity, self).optimize(compressor);
+                return make_node(AST_Infinity, self);
             }
         }
         if (compressor.option("evaluate") && compressor.option("reduce_vars")) {
@@ -3485,14 +3486,6 @@ merge(Compressor.prototype, {
         return self;
     });
 
-    OPT(AST_Infinity, function (self, compressor) {
-        return make_node(AST_Binary, self, {
-            operator : '/',
-            left     : make_node(AST_Number, self, {value: 1}),
-            right    : make_node(AST_Number, self, {value: 0})
-        });
-    });
-
     OPT(AST_Undefined, function(self, compressor){
         if (compressor.option("unsafe")) {
             var scope = compressor.find_parent(AST_Scope);
diff --git a/lib/output.js b/lib/output.js
index 5c11088b..d71f6aac 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -592,6 +592,13 @@ function OutputStream(options) {
             || p instanceof AST_Call && p.expression === this;
     });
 
+    PARENS([ AST_Infinity, AST_NaN ], function(output){
+        var p = output.parent();
+        return p instanceof AST_PropAccess && p.expression === this
+            || p instanceof AST_Call && p.expression === this
+            || p instanceof AST_Unary && p.operator != "+" && p.operator != "-";
+    });
+
     PARENS(AST_Seq, function(output){
         var p = output.parent();
         return p instanceof AST_Call             // (foo, bar)() or foo(1, (2, 3), 4)
@@ -1254,10 +1261,18 @@ function OutputStream(options) {
     });
     DEFPRINT(AST_Hole, noop);
     DEFPRINT(AST_Infinity, function(self, output){
-        output.print("Infinity");
+        output.print("1");
+        output.space();
+        output.print("/");
+        output.space();
+        output.print("0");
     });
     DEFPRINT(AST_NaN, function(self, output){
-        output.print("NaN");
+        output.print("0");
+        output.space();
+        output.print("/");
+        output.space();
+        output.print("0");
     });
     DEFPRINT(AST_This, function(self, output){
         output.print("this");