type-checking

We provide the signatures of a very limited number of standard library classes. We will really appreciate if you write the signature of other classes.

(Note that we are currently working for standard library signatures.)

As noted here by @Ghost4Man: teal-language/tl#391 (comment)

Test case:

-- ice.tl
function get_foo(): string
   if true then
      return "foo";
      print("unreachable")
   end
end

fails with tl run ice.tl

Internal Compiler Error: Teal generator produced invalid Lua. Please report a bug at https://github.com/teal-languag