Change ll_convert<TOTYPE>(string) to just ll_convert(string).

As a function parameter, an assignment expression or a `return` expression,
`ll_convert()` can infer its target type.

When it's important to specify the TOTYPE explicitly, rename the old
`ll_convert()` function template to `ll_convert_to()`. Fix existing usage.

2 files changed, 36 insertions, 9 deletions

diff --git a/indra/llcommon/llstring.h b/indra/llcommon/llstring.h
index b43093fbfc..dbd60bc9c7 100644
--- a/indra/llcommon/llstring.h
+++ b/indra/llcommon/llstring.h
@@ -516,9 +516,36 @@ struct ll_convert_impl
     TO operator()(const FROM& in) const;
 };
 
-// Use a function template to get the nice ll_convert<TO>(from_value) API.
+/**
+ * somefunction(ll_convert(data))
+ * target = ll_convert(data)
+ * totype otherfunc(const fromtype& data)
+ * {
+ *     // ...
+ *     return ll_convert(data);
+ * }
+ * all infer both the FROM type and the TO type.
+ */
+template <typename FROM>
+class ll_convert
+{
+private:
+    const FROM& mRef;
+
+public:
+    ll_convert(const FROM& ref): mRef(ref) {}
+
+    template <typename TO>
+    inline operator TO() const
+    {
+        return ll_convert_impl<TO, FROM>()(mRef);
+    }
+};
+
+// When the TO type must be explicit, use a function template to get
+// ll_convert_to<TO>(from_value) API.
 template<typename TO, typename FROM>
-TO ll_convert(const FROM& in)
+TO ll_convert_to(const FROM& in)
 {
     return ll_convert_impl<TO, FROM>()(in);
 }
@@ -574,8 +601,8 @@ inline size_t ll_convert_length<char>   (const char*    zstr) { return std::strl
 // and longname(const string&, len) so calls written pre-ll_convert() will
 // work. Most of these overloads will be unified once we turn on C++17 and can
 // use std::string_view.
-// It also uses aliasmacro to ensure that both ll_convert<OUTSTR>(const char*)
-// and ll_convert<OUTSTR>(const string&) will work.
+// It also uses aliasmacro to ensure that both ll_convert(const char*)
+// and ll_convert(const string&) will work.
 #define ll_convert_forms(aliasmacro, OUTSTR, INSTR, longname)           \
 LL_COMMON_API OUTSTR longname(const INSTR::value_type* in, size_t len); \
 inline auto longname(const INSTR& in, size_t len)                       \
@@ -807,7 +834,7 @@ LL_COMMON_API std::string ll_convert_string_to_utf8_string(const std::string& in
 template<typename STRING>
 STRING windows_message(unsigned long error)
 {
-    return ll_convert<STRING>(windows_message<std::wstring>(error));
+    return ll_convert(windows_message<std::wstring>(error));
 }
 
 /// There's only one real implementation
@@ -1780,7 +1807,7 @@ auto LLStringUtilBase<T>::getoptenv(const std::string& key) -> boost::optional<s
     if (found)
     {
         // return populated boost::optional
-        return { ll_convert<string_type>(*found) };
+        return { ll_convert_to<string_type>(*found) };
     }
     else
     {
diff --git a/indra/llcommon/stringize.h b/indra/llcommon/stringize.h
index c0b13135f9..63d44a7272 100644
--- a/indra/llcommon/stringize.h
+++ b/indra/llcommon/stringize.h
@@ -88,13 +88,13 @@ struct gstringize_impl
 };
 
 // partially specialize for a single STRING argument -
-// note that ll_convert<T>(T) already handles the trivial case
+// note that ll_convert_to<T>(T) already handles the trivial case
 template <typename OUTCHAR, typename INCHAR>
 struct gstringize_impl<OUTCHAR, std::basic_string<INCHAR>>
 {
     auto operator()(const std::basic_string<INCHAR>& arg)
     {
-        return ll_convert<std::basic_string<OUTCHAR>>(arg);
+        return ll_convert_to<std::basic_string<OUTCHAR>>(arg);
     }
 };
 
@@ -105,7 +105,7 @@ struct gstringize_impl<OUTCHAR, INCHAR*>
 {
     auto operator()(const INCHAR* arg)
     {
-        return ll_convert<std::basic_string<OUTCHAR>>(arg);
+        return ll_convert_to<std::basic_string<OUTCHAR>>(arg);
     }
 };