Cleanup

crates/hir-expand/src/db.rs

@@ -3,7 +3,7 @@
 use base_db::{salsa, CrateId, FileId, SourceDatabase};
 use either::Either;
 use limit::Limit;
-use mbe::syntax_node_to_token_tree;
+use mbe::{syntax_node_to_token_tree, MatchedArmIndex};
 use rustc_hash::FxHashSet;
 use span::{AstIdMap, Span, SyntaxContextData, SyntaxContextId};
 use syntax::{ast, AstNode, Parse, SyntaxElement, SyntaxError, SyntaxNode, SyntaxToken, T};
@@ -546,7 +546,7 @@ fn macro_expand(
     db: &dyn ExpandDatabase,
     macro_call_id: MacroCallId,
     loc: MacroCallLoc,
-) -> ExpandResult<(CowArc<tt::Subtree>, Option<u32>)> {
+) -> ExpandResult<(CowArc<tt::Subtree>, MatchedArmIndex)> {
     let _p = tracing::span!(tracing::Level::INFO, "macro_expand").entered();
 
     let (ExpandResult { value: (tt, matched_arm), err }, span) = match loc.def.kind {

crates/mbe/src/expander.rs

@@ -9,7 +9,7 @@ use rustc_hash::FxHashMap;
 use span::{Edition, Span};
 use syntax::SmolStr;
 
-use crate::{parser::MetaVarKind, ExpandError, ExpandResult};
+use crate::{parser::MetaVarKind, ExpandError, ExpandResult, MatchedArmIndex};
 
 pub(crate) fn expand_rules(
     rules: &[crate::Rule],
@@ -18,7 +18,7 @@ pub(crate) fn expand_rules(
     new_meta_vars: bool,
     call_site: Span,
     def_site_edition: Edition,
-) -> ExpandResult<(tt::Subtree<Span>, Option<u32>)> {
+) -> ExpandResult<(tt::Subtree<Span>, MatchedArmIndex)> {
     let mut match_: Option<(matcher::Match, &crate::Rule, usize)> = None;
     for (idx, rule) in rules.iter().enumerate() {
         let new_match = matcher::match_(&rule.lhs, input, def_site_edition);
@@ -53,7 +53,7 @@ pub(crate) fn expand_rules(
         // if we got here, there was no match without errors
         let ExpandResult { value, err: transcribe_err } =
             transcriber::transcribe(&rule.rhs, &match_.bindings, marker, new_meta_vars, call_site);
-        ExpandResult { value: (value, Some(idx as u32)), err: match_.err.or(transcribe_err) }
+        ExpandResult { value: (value, idx.try_into().ok()), err: match_.err.or(transcribe_err) }
     } else {
         ExpandResult::new(
             (

crates/mbe/src/lib.rs

@@ -122,6 +122,9 @@ impl fmt::Display for CountError {
     }
 }
 
+/// Index of the matched macro arm on successful expansion.
+pub type MatchedArmIndex = Option<u32>;
+
 /// This struct contains AST for a single `macro_rules` definition. What might
 /// be very confusing is that AST has almost exactly the same shape as
 /// `tt::TokenTree`, but there's a crucial difference: in macro rules, `$ident`
@@ -251,7 +254,7 @@ impl DeclarativeMacro {
         new_meta_vars: bool,
         call_site: Span,
         def_site_edition: Edition,
-    ) -> ExpandResult<(tt::Subtree<Span>, Option<u32>)> {
+    ) -> ExpandResult<(tt::Subtree<Span>, MatchedArmIndex)> {
         expander::expand_rules(&self.rules, tt, marker, new_meta_vars, call_site, def_site_edition)
     }
 }

crates/span/src/map.rs

@@ -15,6 +15,8 @@ use crate::{
 #[derive(Debug, PartialEq, Eq, Clone, Hash)]
 pub struct SpanMap<S> {
     spans: Vec<(TextSize, SpanData<S>)>,
+    /// Index of the matched macro arm on successful expansion for declarative macros.
+    // FIXME: Does it make sense to have this here?
     pub matched_arm: Option<u32>,
 }