[list_begin definitions][comment {-- modes --}]

[def [const value]]

The semantic value of the nonterminal symbol is an abstract syntax
tree consisting of a single node node for the nonterminal itself,
which has the ASTs of the symbol's right hand side as its children.

[def [const leaf]]

The semantic value of the nonterminal symbol is an abstract syntax
tree consisting of a single node node for the nonterminal, without any
children. Any ASTs generated by the symbol's right hand side are
discarded.

[def [const void]]

The nonterminal has no semantic value. Any ASTs generated by the
symbol's right hand side are discarded (as well).

[list_end][comment {-- modes --}]