feat: add @syms syntax to specify type of symbolic function

Author: AayushSabharwal

src/types.jl

@@ -1021,8 +1021,16 @@ function _name_type(x)
         lhs, rhs = x.args[1:2]
         if lhs isa Expr && lhs.head === :call
             # e.g. f(::Real)::Unreal
+            if lhs.args[1] isa Expr
+                func_name_and_type = _name_type(lhs.args[1])
+                name = func_name_and_type.name
+                functype = func_name_and_type.type
+            else
+                name = lhs.args[1]
+                functype = Nothing
+            end
             type = map(x->_name_type(x).type, lhs.args[2:end])
-            return (name=lhs.args[1], type=:($FnType{Tuple{$(type...)}, $rhs}))
+            return (name=name, type=:($FnType{Tuple{$(type...)}, $rhs, $functype}))
         else
             return (name=lhs, type=rhs)
         end