Show (short) list of possible enum values when an invalid value is encountered (resolves #1318)

All enum errors have (hopefully) been changed to a luax_enumerror, which has a
fixed error message. If additionally a list of valid options is passed, it
lists that in the error message. For every enum error with few options I've
implemented this using a getConstants call.

This solution has been designed specifically to reduce the number of template
instantiations (as I've been told that was a concern). All new template code
happens in places where there already was an instantiation of the relevant
StringMap. Of course there is still std::vector<std::string>...

--HG--
branch : minor

src/common/runtime.cpp

@@ -31,6 +31,7 @@
 #include <algorithm>
 #include <iostream>
 #include <cstdio>
+#include <sstream>
 
 namespace love
 {
@@ -832,6 +833,25 @@ extern "C" int luax_typerror(lua_State *L, int narg, const char *tname)
 	return luaL_argerror(L, narg, msg);
 }
 
+int luax_enumerror(lua_State *L, const char *enumName, const char *value)
+{
+	return luaL_error(L, "Invalid %s: %s", enumName, value);
+}
+
+int luax_enumerror(lua_State *L, const char *enumName, const std::vector<std::string> &values, const char *value)
+{
+	std::stringstream valueStream;
+	bool first = true;
+	for (auto value : values)
+	{
+		valueStream << (first ? "'" : ", '") << value << "'";
+		first = false;
+	}
+
+	std::string valueString = valueStream.str();
+	return luaL_error(L, "Invalid %s '%s', expected one of: %s", enumName, value, valueString.c_str());
+}
+
 size_t luax_objlen(lua_State *L, int ndx)
 {
 #if LUA_VERSION_NUM == 501