//! Converts a flat collection of matches into a nested form suitable for replacement. When there
//! are multiple matches for a node, or that overlap, priority is given to the earlier rule. Nested
//! matches are only permitted if the inner match is contained entirely within a placeholder of an
//! outer match.
//!
//! For example, if our search pattern is `foo(foo($a))` and the code had `foo(foo(foo(foo(42))))`,
//! then we'll get 3 matches, however only the outermost and innermost matches can be accepted. The
//! middle match would take the second `foo` from the outer match.
use crate::{Match, SsrMatches};
use rustc_hash::FxHashMap;
use syntax::SyntaxNode;
pub(crate) fn nest_and_remove_collisions(
mut matches: Vec<Match>,
sema: &hir::Semantics<ide_db::RootDatabase>,
) -> SsrMatches {
// We sort the matches by depth then by rule index. Sorting by depth means that by the time we
// see a match, any parent matches or conflicting matches will have already been seen. Sorting
// by rule_index means that if there are two matches for the same node, the rule added first
// will take precedence.
matches.sort_by(|a, b| a.depth.cmp(&b.depth).then_with(|| a.rule_index.cmp(&b.rule_index)));
let mut collector = MatchCollector::default();
for m in matches {
collector.add_match(m, sema);
}
collector.into()
}
#[derive(Default)]
struct MatchCollector {
matches_by_node: FxHashMap<SyntaxNode, Match>,
}
impl MatchCollector {
/// Attempts to add `m` to matches. If it conflicts with an existing match, it is discarded. If
/// it is entirely within the a placeholder of an existing match, then it is added as a child
/// match of the existing match.
fn add_match(&mut self, m: Match, sema: &hir::Semantics<ide_db::RootDatabase>) {
let matched_node = m.matched_node.clone();
if let Some(existing) = self.matches_by_node.get_mut(&matched_node) {
try_add_sub_match(m, existing, sema);
return;
}
for ancestor in sema.ancestors_with_macros(m.matched_node.clone()) {
if let Some(existing) = self.matches_by_node.get_mut(&ancestor) {
try_add_sub_match(m, existing, sema);
return;
}
}
self.matches_by_node.insert(matched_node, m);
}
}
/// Attempts to add `m` as a sub-match of `existing`.
fn try_add_sub_match(m: Match, existing: &mut Match, sema: &hir::Semantics<ide_db::RootDatabase>) {
for p in existing.placeholder_values.values_mut() {
// Note, no need to check if p.range.file is equal to m.range.file, since we
// already know we're within `existing`.
if p.range.range.contains_range(m.range.range) {
// Convert the inner matches in `p` into a temporary MatchCollector. When
// we're done, we then convert it back into an SsrMatches. If we expected
// lots of inner matches, it might be worthwhile keeping a MatchCollector
// around for each placeholder match. However we expect most placeholder
// will have 0 and a few will have 1. More than that should hopefully be
// exceptional.
let mut collector = MatchCollector::default();
for m in std::mem::replace(&mut p.inner_matches.matches, Vec::new()) {
collector.matches_by_node.insert(m.matched_node.clone(), m);
}
collector.add_match(m, sema);
p.inner_matches = collector.into();
break;
}
}
}
impl From<MatchCollector> for SsrMatches {
fn from(mut match_collector: MatchCollector) -> Self {
let mut matches = SsrMatches::default();
for (_, m) in match_collector.matches_by_node.drain() {
matches.matches.push(m);
}
matches.matches.sort_by(|a, b| {
// Order matches by file_id then by start range. This should be sufficient since ranges
// shouldn't be overlapping.
a.range
.file_id
.cmp(&b.range.file_id)
.then_with(|| a.range.range.start().cmp(&b.range.range.start()))
});
matches
}
}