Duplicated Names

This checks duplicated identifiers in their same scope:

(module
  (func $f)
  (func $f))

Same identifier in different scopes is allowed:

(module
  (func (param $p i32))
  (func (param $p i32)))

Though in the same scope, if two identifiers have same name but different kinds, it is allowed:

(module
  (func $f)
  (type $f (func)))

In the example above, the first $f is funcidx while the second $f is typeidx.