Error is used to cache parse errors encountered during the execution of the parse method.
A StatusGuard manages a tentative parse.
If true, > is interpreted as ther greater-than operator.
Record whether the current scope is valid.
RuleSet defines non-standard optional rules that can be chosen at runtime.
compound-statement:
function-body:
[gram.dcl.decl]
Return the origin of the given pointer (filename and line number)
parameter-declaration:
template-parameter-list: