make sure 'computed_props' creates string keys. Closes #1500

lib/compress/index.js

@@ -3924,21 +3924,23 @@ function lift_key(self, compressor) {
     if (!(self.key instanceof AST_Constant)) return self;
     // allow certain acceptable props as not all AST_Constants are true constants
     if (self.key instanceof AST_String || self.key instanceof AST_Number) {
-        if (self.key.value === "__proto__") return self;
-        if (self.key.value == "constructor"
+        const key = self.key.value.toString();
+
+        if (key === "__proto__") return self;
+        if (key == "constructor"
             && compressor.parent() instanceof AST_Class) return self;
         if (self instanceof AST_ObjectKeyVal) {
             self.quote = self.key.quote;
-            self.key = self.key.value;
+            self.key = key;
         } else if (self instanceof AST_ClassProperty) {
             self.quote = self.key.quote;
             self.key = make_node(AST_SymbolClassProperty, self.key, {
-                name: self.key.value
+                name: key,
             });
         } else {
             self.quote = self.key.quote;
             self.key = make_node(AST_SymbolMethod, self.key, {
-                name: self.key.value
+                name: key,
             });
         }
     }

test/compress/object.js

@@ -186,6 +186,20 @@ convert_computed_props_to_regular_ones: {
     ]
 }
 
+convert_computed_props_and_keep_quotes: {
+    options = {
+        booleans: true,
+        computed_props: true,
+        evaluate: true,
+    }
+    format = { quote_keys: true }
+    input: {
+        console.log({ [11]: 22, 33: 44 });
+    }
+    expect_exact: 'console.log({"11":22,"33":44});'
+    expect_stdout: "{ '11': 22, '33': 44 }"
+}
+
 computed_property_names_evaluated_1: {
     options = {
         evaluate: true