No. First, understand what the language is for (if nothing, stop here...). Second, make the main design choices (expressiveness of type system, level of contr

No. First, understand what the language is for (if nothing, stop here...). Second, make the main design choices (expressiveness of type system, level of control of mutability or lack thereof, etc.). Third, design the type system, with a view to type inference. Fourth, design and define the semantics. Do those last two in a way that will let you test your implementation against these definitions automatically. Fifth, think about sufficiently efficient implementation strategies. Sixth, pick a syntactic style that will be familiar to most of your users. Seventh, design the actual syntax. Eighth, implement it. Ninth, try it out on users and go back to the start. Tenth, rest.