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Reorder cases in parse_tt_inner.

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I find the new order easier to read: within a matcher; past the end of a
repetition; at end of input. It also reduces the indentation level by
one for
This commit is contained in:
Nicholas Nethercote 2022-03-18 14:16:45 +11:00
parent 83044714a1
commit 14875a5564
1 changed files with 55 additions and 61 deletions
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116
compiler/rustc_expand/src/mbe/macro_parser.rs
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@ -540,67 +540,7 @@ fn parse_tt_inner<'root, 'tt>(
let idx = item.idx;
let len = item.top_elts.len();
// If `idx >= len`, then we are at or past the end of the matcher of `item`.
if idx >= len {
// We are repeating iff there is a parent. If the matcher is inside of a repetition,
// then we could be at the end of a sequence or at the beginning of the next
// repetition.
if let Some(repetition) = &item.repetition {
debug_assert!(idx <= len + 1);
debug_assert!(matches!(item.top_elts, Tt(TokenTree::Sequence(..))));
// At this point, regardless of whether there is a separator, we should add all
// matches from the complete repetition of the sequence to the shared, top-level
// `matches` list (actually, `up.matches`, which could itself not be the top-level,
// but anyway...). Moreover, we add another item to `cur_items` in which the "dot"
// is at the end of the `up` matcher. This ensures that the "dot" in the `up`
// matcher is also advanced sufficiently.
//
// NOTE: removing the condition `idx == len` allows trailing separators.
if idx == len {
// Get the `up` matcher
let mut new_pos = repetition.up.clone();
// Add matches from this repetition to the `matches` of `up`
for idx in item.match_lo..item.match_hi {
let sub = item.matches[idx].clone();
new_pos.push_match(idx, MatchedSeq(sub));
}
// Move the "dot" past the repetition in `up`
new_pos.match_cur = item.match_hi;
new_pos.idx += 1;
cur_items.push(new_pos);
}
// Check if we need a separator.
if idx == len && repetition.sep.is_some() {
// We have a separator, and it is the current token. We can advance past the
// separator token.
if repetition.sep.as_ref().map_or(false, |sep| token_name_eq(token, sep)) {
item.idx += 1;
next_items.push(item);
}
} else if repetition.seq_op != mbe::KleeneOp::ZeroOrOne {
// We don't need a separator. Move the "dot" back to the beginning of the
// matcher and try to match again UNLESS we are only allowed to have _one_
// repetition.
item.match_cur = item.match_lo;
item.idx = 0;
cur_items.push(item);
}
} else {
// If we are not in a repetition, then being at the end of a matcher means that we
// have reached the potential end of the input.
debug_assert_eq!(idx, len);
if *token == token::Eof {
eof_items = match eof_items {
EofItems::None => EofItems::One(item),
EofItems::One(_) | EofItems::Multiple => EofItems::Multiple,
}
}
}
} else {
if idx < len {
// We are in the middle of a matcher. Look at what token in the matcher we are trying
// to match the current token (`token`) against. Depending on that, we may generate new
// items.
@ -677,6 +617,60 @@ fn parse_tt_inner<'root, 'tt>(
TokenTree::MetaVar(..) | TokenTree::MetaVarExpr(..) => unreachable!(),
}
} else if let Some(repetition) = &item.repetition {
// We are past the end of a repetition.
debug_assert!(idx <= len + 1);
debug_assert!(matches!(item.top_elts, Tt(TokenTree::Sequence(..))));
// At this point, regardless of whether there is a separator, we should add all
// matches from the complete repetition of the sequence to the shared, top-level
// `matches` list (actually, `up.matches`, which could itself not be the top-level,
// but anyway...). Moreover, we add another item to `cur_items` in which the "dot"
// is at the end of the `up` matcher. This ensures that the "dot" in the `up`
// matcher is also advanced sufficiently.
//
// NOTE: removing the condition `idx == len` allows trailing separators.
if idx == len {
// Get the `up` matcher
let mut new_pos = repetition.up.clone();
// Add matches from this repetition to the `matches` of `up`
for idx in item.match_lo..item.match_hi {
let sub = item.matches[idx].clone();
new_pos.push_match(idx, MatchedSeq(sub));
}
// Move the "dot" past the repetition in `up`
new_pos.match_cur = item.match_hi;
new_pos.idx += 1;
cur_items.push(new_pos);
}
// Check if we need a separator.
if idx == len && repetition.sep.is_some() {
// We have a separator, and it is the current token. We can advance past the
// separator token.
if repetition.sep.as_ref().map_or(false, |sep| token_name_eq(token, sep)) {
item.idx += 1;
next_items.push(item);
}
} else if repetition.seq_op != mbe::KleeneOp::ZeroOrOne {
// We don't need a separator. Move the "dot" back to the beginning of the
// matcher and try to match again UNLESS we are only allowed to have _one_
// repetition.
item.match_cur = item.match_lo;
item.idx = 0;
cur_items.push(item);
}
} else {
// We are past the end of the matcher, and not in a repetition. Look for end of input.
debug_assert_eq!(idx, len);
if *token == token::Eof {
eof_items = match eof_items {
EofItems::None => EofItems::One(item),
EofItems::One(_) | EofItems::Multiple => EofItems::Multiple,
}
}
}
}