http://cui.unige.ch/isi/bnf/Ada95/index_subtype_definition.html
のバグを発見、修正:

<index_subtype_definition> ::= <subtype_mark> <range> "<>"
と書いてあるが、仕様を見ると
<index_subtype_definition> ::= <subtype_mark> "range" "<>"
が正解
subtype_declaration
declarative_part subprogram_body
package_declaration