close #524: convert predicate sets into Maps instead of objects

lib/compress/index.js

@@ -2695,17 +2695,19 @@ function best_of(compressor, ast1, ast2) {
 }
 
 function convert_to_predicate(obj) {
+    const out = new Map();
     for (var key of Object.keys(obj)) {
-        obj[key] = makePredicate(obj[key]);
+        out.set(key, makePredicate(obj[key]));
     }
+    return out;
 }
 
 var object_fns = [
     "constructor",
     "toString",
     "valueOf",
 ];
-var native_fns = {
+var native_fns = convert_to_predicate({
     Array: [
         "indexOf",
         "join",
@@ -2741,9 +2743,8 @@ var native_fns = {
         "toUpperCase",
         "trim",
     ].concat(object_fns),
-};
-convert_to_predicate(native_fns);
-var static_fns = {
+});
+var static_fns = convert_to_predicate({
     Array: [
         "isArray",
     ],
@@ -2783,8 +2784,7 @@ var static_fns = {
     String: [
         "fromCharCode",
     ],
-};
-convert_to_predicate(static_fns);
+});
 
 // methods to evaluate a constant expression
 (function(def_eval) {
@@ -2989,7 +2989,7 @@ convert_to_predicate(static_fns);
         Object: Object,
         String: String,
     };
-    var static_values = {
+    var static_values = convert_to_predicate({
         Math: [
             "E",
             "LN10",
@@ -3007,8 +3007,7 @@ convert_to_predicate(static_fns);
             "NEGATIVE_INFINITY",
             "POSITIVE_INFINITY",
         ],
-    };
-    convert_to_predicate(static_values);
+    });
     def_eval(AST_PropAccess, function(compressor, depth) {
         if (compressor.option("unsafe")) {
             var key = this.property;
@@ -3032,7 +3031,7 @@ convert_to_predicate(static_fns);
                 if (first_arg == null || first_arg.thedef && first_arg.thedef.undeclared) {
                     return this.clone();
                 }
-                var static_value = static_values[exp.name];
+                var static_value = static_values.get(exp.name);
                 if (!static_value || !static_value.has(key)) return this;
                 val = global_objs[exp.name];
             } else {
@@ -3072,13 +3071,13 @@ convert_to_predicate(static_fns);
                 if ((first_arg == null || first_arg.thedef && first_arg.thedef.undeclared)) {
                     return this.clone();
                 }
-                var static_fn = static_fns[e.name];
+                var static_fn = static_fns.get(e.name);
                 if (!static_fn || !static_fn.has(key)) return this;
                 val = global_objs[e.name];
             } else {
                 val = e._eval(compressor, depth + 1);
                 if (val === e || !val) return this;
-                var native_fn = native_fns[val.constructor.name];
+                var native_fn = native_fns.get(val.constructor.name);
                 if (!native_fn || !native_fn.has(key)) return this;
             }
             var args = [];
@@ -3198,10 +3197,11 @@ AST_Call.DEFMETHOD("is_expr_pure", function(compressor) {
             return false;
         }
         if (is_undeclared_ref(expr) && global_pure_fns.has(expr.name)) return true;
+        let static_fn;
         if (expr instanceof AST_Dot
             && is_undeclared_ref(expr.expression)
-            && static_fns.hasOwnProperty(expr.expression.name)
-            && static_fns[expr.expression.name].has(expr.property)) {
+            && (static_fn = static_fns.get(expr.expression.name))
+            && static_fn.has(expr.property)) {
             return true;
         }
     }
@@ -3213,17 +3213,17 @@ AST_Dot.DEFMETHOD("is_call_pure", function(compressor) {
     const expr = this.expression;
     let map;
     if (expr instanceof AST_Array) {
-        map = native_fns.Array;
+        map = native_fns.get("Array");
     } else if (expr.is_boolean()) {
-        map = native_fns.Boolean;
+        map = native_fns.get("Boolean");
     } else if (expr.is_number(compressor)) {
-        map = native_fns.Number;
+        map = native_fns.get("Number");
     } else if (expr instanceof AST_RegExp) {
-        map = native_fns.RegExp;
+        map = native_fns.get("RegExp");
     } else if (expr.is_string(compressor)) {
-        map = native_fns.String;
+        map = native_fns.get("String");
     } else if (!this.may_throw_on_access(compressor)) {
-        map = native_fns.Object;
+        map = native_fns.get("Object");
     }
     return map && map.has(this.property);
 });