Internal improvements to Parser::next_token/prev_token #86
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- Avoid cloning whitespace tokens in `peek_nth_token()` by using a &Token from `tokens.get()` instead of a cloned `Token` from `token_at()` - Similarly avoid cloning in `next_token_no_skip`, and clone the non-whitespace tokens in `next_token` instead. - Remove `token_at`, which was only used in `peek_token` and `peek_nth_token` - Fold `prev_token_no_skip()` into `prev_token()` and make `prev_token` return nothing, as the return value isn't used anyway.
Before this `next_token()` would only increment the index when returning `Some(token)`. This means that the caller wishing to rewind must be careful not to call `prev_token()` on EOF (`None`), while not forgetting to call it for `Some`. Not doing this resulted in bugs in the undertested code that does error handling. After making this mistake several times, I'm changing `next_token()` / `prev_token()` so that calling `next_token(); prev_token(); next_token()` returns the same token in the first and the last invocation.
Pull Request Test Coverage Report for Build 233
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This reduces the number of helper functions used by
next_token()/prev_token()while slightly improving performance and reducing the chances of errors when usingprev_token()after hitting end-of-file.