pub fn do_expand_partially<T: Into<Tokens>>(tokens: T) -> Result<Tokens>Expand description
As do_expand, but stopping at the first unexpandable token of each
branch (ExpansionLevel::Partial) instead of expanding to the bitter end.
What a binding wants when it needs to look at what a macro produces —
resolving a \newcommand alias, say — without forcing the primitives
underneath it, whose expansion has side effects the caller is not ready for.