Use different parse errors for NaN and INF double values.

Summary: To facilitate debugging of T88337980

Reviewed By: rdavies

Differential Revision: D27610329

fbshipit-source-id: 6b01af24e2cfdda9afcbef10d2951ac071d2fd10

folly/json.cpp

@@ -61,11 +61,15 @@ struct Printer {
   void operator()(dynamic const& v) const {
     switch (v.type()) {
       case dynamic::DOUBLE:
-        if (!opts_.allow_nan_inf &&
-            (std::isnan(v.asDouble()) || std::isinf(v.asDouble()))) {
-          throw json::parse_error(
-              "folly::toJson: JSON object value was a "
-              "NaN or INF");
+        if (!opts_.allow_nan_inf) {
+          if (std::isnan(v.asDouble())) {
+            throw json::parse_error(
+                "folly::toJson: JSON object value was a NaN");
+          }
+          if (std::isinf(v.asDouble())) {
+            throw json::parse_error(
+                "folly::toJson: JSON object value was an INF");
+          }
         }
         toAppend(
             v.asDouble(), &out_, opts_.double_mode, opts_.double_num_digits);