1 files changed, 85 insertions, 0 deletions

diff --git a/crates/mbe/src/token_map.rs b/crates/mbe/src/token_map.rs
new file mode 100644
index 000000000..6df3de3b3
--- /dev/null
+++ b/crates/mbe/src/token_map.rs
@@ -0,0 +1,85 @@
+//! Mapping between `TokenId`s and the token's position in macro definitions or inputs.
+
+use parser::{SyntaxKind, T};
+use syntax::{TextRange, TextSize};
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+enum TokenTextRange {
+    Token(TextRange),
+    Delimiter(TextRange),
+}
+
+impl TokenTextRange {
+    fn by_kind(self, kind: SyntaxKind) -> Option<TextRange> {
+        match self {
+            TokenTextRange::Token(it) => Some(it),
+            TokenTextRange::Delimiter(it) => match kind {
+                T!['{'] | T!['('] | T!['['] => Some(TextRange::at(it.start(), 1.into())),
+                T!['}'] | T![')'] | T![']'] => {
+                    Some(TextRange::at(it.end() - TextSize::of('}'), 1.into()))
+                }
+                _ => None,
+            },
+        }
+    }
+}
+
+/// Maps `tt::TokenId` to the relative range of the original token.
+#[derive(Debug, PartialEq, Eq, Clone, Default)]
+pub struct TokenMap {
+    /// Maps `tt::TokenId` to the *relative* source range.
+    entries: Vec<(tt::TokenId, TokenTextRange)>,
+}
+
+impl TokenMap {
+    pub fn token_by_range(&self, relative_range: TextRange) -> Option<tt::TokenId> {
+        let &(token_id, _) = self.entries.iter().find(|(_, range)| match range {
+            TokenTextRange::Token(it) => *it == relative_range,
+            TokenTextRange::Delimiter(it) => {
+                let open = TextRange::at(it.start(), 1.into());
+                let close = TextRange::at(it.end() - TextSize::of('}'), 1.into());
+                open == relative_range || close == relative_range
+            }
+        })?;
+        Some(token_id)
+    }
+
+    pub fn range_by_token(&self, token_id: tt::TokenId, kind: SyntaxKind) -> Option<TextRange> {
+        let &(_, range) = self.entries.iter().find(|(tid, _)| *tid == token_id)?;
+        range.by_kind(kind)
+    }
+
+    pub(crate) fn shrink_to_fit(&mut self) {
+        self.entries.shrink_to_fit();
+    }
+
+    pub(crate) fn insert(&mut self, token_id: tt::TokenId, relative_range: TextRange) {
+        self.entries.push((token_id, TokenTextRange::Token(relative_range)));
+    }
+
+    pub(crate) fn insert_delim(
+        &mut self,
+        token_id: tt::TokenId,
+        open_relative_range: TextRange,
+        close_relative_range: TextRange,
+    ) -> usize {
+        let res = self.entries.len();
+        let cover = open_relative_range.cover(close_relative_range);
+
+        self.entries.push((token_id, TokenTextRange::Delimiter(cover)));
+        res
+    }
+
+    pub(crate) fn update_close_delim(&mut self, idx: usize, close_relative_range: TextRange) {
+        let (_, token_text_range) = &mut self.entries[idx];
+        if let TokenTextRange::Delimiter(dim) = token_text_range {
+            let cover = dim.cover(close_relative_range);
+            *token_text_range = TokenTextRange::Delimiter(cover);
+        }
+    }
+
+    pub(crate) fn remove_delim(&mut self, idx: usize) {
+        // FIXME: This could be accidentally quadratic
+        self.entries.remove(idx);
+    }
+}