Introduce str and c_str into the format namespace.

format.h

@@ -380,20 +380,24 @@ class ArgInserter {
     return Proxy(f);
   }
 
-  std::string str() const { return Format()->str(); }
+  // Performs formatting and returns a std::string with the output.
+  friend std::string str(Proxy p) {
+    return Format(p)->str();
+  }
 
   // Performs formatting and returns a C string with the output.
   friend const char *c_str(Proxy p) {
     return Format(p)->c_str();
   }
-
-  // Performs formatting and returns a std::string with the output.
-  friend std::string str(Proxy p) {
-    return Format(p)->str();
-  }
 };
+
+const char *c_str(ArgInserter::Proxy p);
+std::string str(ArgInserter::Proxy p);
 }
 
+using format::internal::c_str;
+using format::internal::str;
+
 // ArgFormatter provides access to the format buffer within custom
 // Format functions. It is not desirable to pass Formatter to these
 // functions because Formatter::operator() is not reentrant and

format_test.cc

@@ -729,6 +729,11 @@ TEST(FormatterTest, ArgInserter) {
   EXPECT_STREQ("12", c_str(format("{0}") << 2));
 }
 
+TEST(FormatterTest, StrNamespace) {
+  fmt::str(Format(""));
+  fmt::c_str(Format(""));
+}
+
 struct CountCalls {
   int &num_calls;
 
@@ -791,7 +796,7 @@ TEST(TempFormatterTest, Example) {
 
 template <typename T>
 std::string str(const T &value) {
-  return (fmt::Format("{0}") << value).str();
+  return fmt::str(fmt::Format("{0}") << value);
 }
 
 TEST(StrTest, Convert) {