Merge #7494

7494: Simpilfy mbe parsing r=edwin0cheng a=edwin0cheng

bors r+

Co-authored-by: Edwin Cheng <[email protected]>

4 files changed, 71 insertions, 74 deletions

diff --git a/crates/mbe/src/expander/matcher.rs b/crates/mbe/src/expander/matcher.rs
index 987a4f676..800931cd1 100644
--- a/crates/mbe/src/expander/matcher.rs
+++ b/crates/mbe/src/expander/matcher.rs
@@ -70,7 +70,7 @@ pub(super) struct Match {
 }
 
 impl Match {
-    pub(super) fn add_err(&mut self, err: ExpandError) {
+    fn add_err(&mut self, err: ExpandError) {
         let prev_err = self.err.take();
         self.err = prev_err.or(Some(err));
         self.err_count += 1;
@@ -79,12 +79,10 @@ impl Match {
 
 /// Matching errors are added to the `Match`.
 pub(super) fn match_(pattern: &MetaTemplate, src: &tt::Subtree) -> Match {
-    assert!(pattern.delimiter == None);
-
     let mut res = Match::default();
     let mut src = TtIter::new(src);
 
-    match_subtree(&mut res, pattern, &mut src);
+    match_tokens(&mut res, pattern, &mut src);
 
     if src.len() > 0 {
         res.unmatched_tts += src.len();
@@ -94,36 +92,16 @@ pub(super) fn match_(pattern: &MetaTemplate, src: &tt::Subtree) -> Match {
     res
 }
 
-fn match_subtree(res: &mut Match, pattern: &MetaTemplate, src: &mut TtIter) {
+fn match_tokens(res: &mut Match, pattern: &MetaTemplate, src: &mut TtIter) {
     for op in pattern.iter() {
         match op {
             Op::Leaf(lhs) => {
-                let rhs = match src.expect_leaf() {
-                    Ok(l) => l,
-                    Err(()) => {
-                        res.add_err(err!("expected leaf: `{}`", lhs));
-                        continue;
-                    }
-                };
-                match (lhs, rhs) {
-                    (
-                        tt::Leaf::Punct(tt::Punct { char: lhs, .. }),
-                        tt::Leaf::Punct(tt::Punct { char: rhs, .. }),
-                    ) if lhs == rhs => (),
-                    (
-                        tt::Leaf::Ident(tt::Ident { text: lhs, .. }),
-                        tt::Leaf::Ident(tt::Ident { text: rhs, .. }),
-                    ) if lhs == rhs => (),
-                    (
-                        tt::Leaf::Literal(tt::Literal { text: lhs, .. }),
-                        tt::Leaf::Literal(tt::Literal { text: rhs, .. }),
-                    ) if lhs == rhs => (),
-                    _ => {
-                        res.add_err(ExpandError::UnexpectedToken);
-                    }
+                if let Err(err) = match_leaf(lhs, src) {
+                    res.add_err(err);
+                    continue;
                 }
             }
-            Op::Subtree(lhs) => {
+            Op::Subtree { tokens, delimiter: delim } => {
                 let rhs = match src.expect_subtree() {
                     Ok(s) => s,
                     Err(()) => {
@@ -131,12 +109,12 @@ fn match_subtree(res: &mut Match, pattern: &MetaTemplate, src: &mut TtIter) {
                         continue;
                     }
                 };
-                if lhs.delimiter_kind() != rhs.delimiter_kind() {
+                if delim.map(|it| it.kind) != rhs.delimiter_kind() {
                     res.add_err(err!("mismatched delimiter"));
                     continue;
                 }
                 let mut src = TtIter::new(rhs);
-                match_subtree(res, lhs, &mut src);
+                match_tokens(res, tokens, &mut src);
                 if src.len() > 0 {
                     res.add_err(err!("leftover tokens"));
                 }
@@ -162,14 +140,42 @@ fn match_subtree(res: &mut Match, pattern: &MetaTemplate, src: &mut TtIter) {
                     res.add_err(err);
                 }
             }
-            Op::Repeat { subtree, kind, separator } => {
+            Op::Repeat { tokens: subtree, kind, separator } => {
                 match_repeat(res, subtree, *kind, separator, src);
             }
         }
     }
 }
 
-pub(super) fn match_repeat(
+fn match_leaf(lhs: &tt::Leaf, src: &mut TtIter) -> Result<(), ExpandError> {
+    let rhs = match src.expect_leaf() {
+        Ok(l) => l,
+        Err(()) => {
+            return Err(err!("expected leaf: `{}`", lhs));
+        }
+    };
+    match (lhs, rhs) {
+        (
+            tt::Leaf::Punct(tt::Punct { char: lhs, .. }),
+            tt::Leaf::Punct(tt::Punct { char: rhs, .. }),
+        ) if lhs == rhs => (),
+        (
+            tt::Leaf::Ident(tt::Ident { text: lhs, .. }),
+            tt::Leaf::Ident(tt::Ident { text: rhs, .. }),
+        ) if lhs == rhs => (),
+        (
+            tt::Leaf::Literal(tt::Literal { text: lhs, .. }),
+            tt::Leaf::Literal(tt::Literal { text: rhs, .. }),
+        ) if lhs == rhs => (),
+        _ => {
+            return Err(ExpandError::UnexpectedToken);
+        }
+    }
+
+    Ok(())
+}
+
+fn match_repeat(
     res: &mut Match,
     pattern: &MetaTemplate,
     kind: RepeatKind,
@@ -191,7 +197,7 @@ pub(super) fn match_repeat(
         }
 
         let mut nested = Match::default();
-        match_subtree(&mut nested, pattern, &mut fork);
+        match_tokens(&mut nested, pattern, &mut fork);
         if nested.err.is_none() {
             limit -= 1;
             if limit == 0 {
@@ -292,8 +298,8 @@ fn collect_vars(buf: &mut Vec<SmolStr>, pattern: &MetaTemplate) {
         match op {
             Op::Var { name, .. } => buf.push(name.clone()),
             Op::Leaf(_) => (),
-            Op::Subtree(subtree) => collect_vars(buf, subtree),
-            Op::Repeat { subtree, .. } => collect_vars(buf, subtree),
+            Op::Subtree { tokens, .. } => collect_vars(buf, tokens),
+            Op::Repeat { tokens, .. } => collect_vars(buf, tokens),
         }
     }
 }
@@ -325,7 +331,7 @@ impl<'a> TtIter<'a> {
         ok
     }
 
-    pub(crate) fn expect_tt(&mut self) -> Result<tt::TokenTree, ()> {
+    fn expect_tt(&mut self) -> Result<tt::TokenTree, ()> {
         match self.peek_n(0) {
             Some(tt::TokenTree::Leaf(tt::Leaf::Punct(punct))) if punct.char == '\'' => {
                 return self.expect_lifetime();
@@ -386,7 +392,7 @@ impl<'a> TtIter<'a> {
         }
     }
 
-    pub(crate) fn expect_lifetime(&mut self) -> Result<tt::TokenTree, ()> {
+    fn expect_lifetime(&mut self) -> Result<tt::TokenTree, ()> {
         let punct = self.expect_punct()?;
         if punct.char != '\'' {
             return Err(());
@@ -403,13 +409,13 @@ impl<'a> TtIter<'a> {
         .into())
     }
 
-    pub(crate) fn expect_fragment(
+    fn expect_fragment(
         &mut self,
         fragment_kind: parser::FragmentKind,
     ) -> ExpandResult<Option<tt::TokenTree>> {
-        pub(crate) struct OffsetTokenSink<'a> {
-            pub(crate) cursor: Cursor<'a>,
-            pub(crate) error: bool,
+        struct OffsetTokenSink<'a> {
+            cursor: Cursor<'a>,
+            error: bool,
         }
 
         impl<'a> TreeSink for OffsetTokenSink<'a> {
@@ -465,7 +471,7 @@ impl<'a> TtIter<'a> {
         ExpandResult { value: res, err }
     }
 
-    pub(crate) fn eat_vis(&mut self) -> Option<tt::TokenTree> {
+    fn eat_vis(&mut self) -> Option<tt::TokenTree> {
         let mut fork = self.clone();
         match fork.expect_fragment(Visibility) {
             ExpandResult { value: tt, err: None } => {
@@ -476,7 +482,7 @@ impl<'a> TtIter<'a> {
         }
     }
 
-    pub(crate) fn eat_char(&mut self, c: char) -> Option<tt::TokenTree> {
+    fn eat_char(&mut self, c: char) -> Option<tt::TokenTree> {
         let mut fork = self.clone();
         match fork.expect_char(c) {
             Ok(_) => {
diff --git a/crates/mbe/src/expander/transcriber.rs b/crates/mbe/src/expander/transcriber.rs
index 30c090f32..78368a33e 100644
--- a/crates/mbe/src/expander/transcriber.rs
+++ b/crates/mbe/src/expander/transcriber.rs
@@ -2,6 +2,7 @@
 //! `$ident => foo`, interpolates variables in the template, to get `fn foo() {}`
 
 use syntax::SmolStr;
+use tt::Delimiter;
 
 use super::ExpandResult;
 use crate::{
@@ -54,10 +55,9 @@ pub(super) fn transcribe(
     template: &MetaTemplate,
     bindings: &Bindings,
 ) -> ExpandResult<tt::Subtree> {
-    assert!(template.delimiter == None);
     let mut ctx = ExpandCtx { bindings: &bindings, nesting: Vec::new() };
     let mut arena: Vec<tt::TokenTree> = Vec::new();
-    expand_subtree(&mut ctx, template, &mut arena)
+    expand_subtree(&mut ctx, template, None, &mut arena)
 }
 
 #[derive(Debug)]
@@ -80,6 +80,7 @@ struct ExpandCtx<'a> {
 fn expand_subtree(
     ctx: &mut ExpandCtx,
     template: &MetaTemplate,
+    delimiter: Option<Delimiter>,
     arena: &mut Vec<tt::TokenTree>,
 ) -> ExpandResult<tt::Subtree> {
     // remember how many elements are in the arena now - when returning, we want to drain exactly how many elements we added. This way, the recursive uses of the arena get their own "view" of the arena, but will reuse the allocation
@@ -88,8 +89,9 @@ fn expand_subtree(
     for op in template.iter() {
         match op {
             Op::Leaf(tt) => arena.push(tt.clone().into()),
-            Op::Subtree(tt) => {
-                let ExpandResult { value: tt, err: e } = expand_subtree(ctx, &tt, arena);
+            Op::Subtree { tokens, delimiter } => {
+                let ExpandResult { value: tt, err: e } =
+                    expand_subtree(ctx, &tokens, *delimiter, arena);
                 err = err.or(e);
                 arena.push(tt.into());
             }
@@ -98,7 +100,7 @@ fn expand_subtree(
                 err = err.or(e);
                 push_fragment(arena, fragment);
             }
-            Op::Repeat { subtree, kind, separator } => {
+            Op::Repeat { tokens: subtree, kind, separator } => {
                 let ExpandResult { value: fragment, err: e } =
                     expand_repeat(ctx, subtree, *kind, separator, arena);
                 err = err.or(e);
@@ -108,7 +110,7 @@ fn expand_subtree(
     }
     // drain the elements added in this instance of expand_subtree
     let tts = arena.drain(start_elements..arena.len()).collect();
-    ExpandResult { value: tt::Subtree { delimiter: template.delimiter, token_trees: tts }, err }
+    ExpandResult { value: tt::Subtree { delimiter, token_trees: tts }, err }
 }
 
 fn expand_var(ctx: &mut ExpandCtx, v: &SmolStr, id: tt::TokenId) -> ExpandResult<Fragment> {
@@ -162,7 +164,7 @@ fn expand_repeat(
     let mut counter = 0;
 
     loop {
-        let ExpandResult { value: mut t, err: e } = expand_subtree(ctx, template, arena);
+        let ExpandResult { value: mut t, err: e } = expand_subtree(ctx, template, None, arena);
         let nesting_state = ctx.nesting.last_mut().unwrap();
         if nesting_state.at_end || !nesting_state.hit {
             break;
diff --git a/crates/mbe/src/lib.rs b/crates/mbe/src/lib.rs
index 56c632665..d80bd7a33 100644
--- a/crates/mbe/src/lib.rs
+++ b/crates/mbe/src/lib.rs
@@ -92,18 +92,11 @@ struct Rule {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-struct MetaTemplate {
-    delimiter: Option<Delimiter>,
-    tokens: Vec<Op>,
-}
+struct MetaTemplate(Vec<Op>);
 
 impl<'a> MetaTemplate {
     fn iter(&self) -> impl Iterator<Item = &Op> {
-        self.tokens.iter()
-    }
-
-    fn delimiter_kind(&self) -> Option<DelimiterKind> {
-        self.delimiter.map(|it| it.kind)
+        self.0.iter()
     }
 }
 
@@ -288,8 +281,8 @@ impl Rule {
             .expect_subtree()
             .map_err(|()| ParseError::Expected("expected subtree".to_string()))?;
 
-        let lhs = MetaTemplate { tokens: parse_pattern(&lhs)?, delimiter: None };
-        let rhs = MetaTemplate { tokens: parse_template(&rhs)?, delimiter: None };
+        let lhs = MetaTemplate(parse_pattern(&lhs)?);
+        let rhs = MetaTemplate(parse_template(&rhs)?);
 
         Ok(crate::Rule { lhs, rhs })
     }
@@ -298,8 +291,8 @@ impl Rule {
 fn validate(pattern: &MetaTemplate) -> Result<(), ParseError> {
     for op in pattern.iter() {
         match op {
-            Op::Subtree(subtree) => validate(&subtree)?,
-            Op::Repeat { subtree, separator, .. } => {
+            Op::Subtree { tokens, .. } => validate(&tokens)?,
+            Op::Repeat { tokens: subtree, separator, .. } => {
                 // Checks that no repetition which could match an empty token
                 // https://github.com/rust-lang/rust/blob/a58b1ed44f5e06976de2bdc4d7dc81c36a96934f/src/librustc_expand/mbe/macro_rules.rs#L558
 
@@ -319,7 +312,7 @@ fn validate(pattern: &MetaTemplate) -> Result<(), ParseError> {
                                 )
                             }
                             Op::Leaf(_) => {}
-                            Op::Subtree(_) => {}
+                            Op::Subtree { .. } => {}
                         }
                         false
                     }) {
diff --git a/crates/mbe/src/parser.rs b/crates/mbe/src/parser.rs
index b90ae7015..f891ec29c 100644
--- a/crates/mbe/src/parser.rs
+++ b/crates/mbe/src/parser.rs
@@ -3,15 +3,16 @@
 
 use smallvec::SmallVec;
 use syntax::SmolStr;
+use tt::Delimiter;
 
 use crate::{tt_iter::TtIter, MetaTemplate, ParseError};
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(crate) enum Op {
     Var { name: SmolStr, kind: Option<SmolStr>, id: tt::TokenId },
-    Repeat { subtree: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
+    Repeat { tokens: MetaTemplate, kind: RepeatKind, separator: Option<Separator> },
     Leaf(tt::Leaf),
-    Subtree(MetaTemplate),
+    Subtree { tokens: MetaTemplate, delimiter: Option<Delimiter> },
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -92,12 +93,10 @@ fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Resul
             match second {
                 tt::TokenTree::Subtree(subtree) => {
                     let (separator, kind) = parse_repeat(src)?;
-                    let delimiter = subtree.delimiter;
                     let tokens = parse_inner(&subtree, mode)
                         .into_iter()
                         .collect::<Result<Vec<Op>, ParseError>>()?;
-                    let subtree = MetaTemplate { tokens, delimiter };
-                    Op::Repeat { subtree, separator, kind }
+                    Op::Repeat { tokens: MetaTemplate(tokens), separator, kind }
                 }
                 tt::TokenTree::Leaf(leaf) => match leaf {
                     tt::Leaf::Punct(punct) => {
@@ -136,12 +135,9 @@ fn next_op<'a>(first: &tt::TokenTree, src: &mut TtIter<'a>, mode: Mode) -> Resul
         }
         tt::TokenTree::Leaf(tt) => Op::Leaf(tt.clone()),
         tt::TokenTree::Subtree(subtree) => {
-            let delimiter = subtree.delimiter;
             let tokens =
                 parse_inner(&subtree, mode).into_iter().collect::<Result<Vec<Op>, ParseError>>()?;
-
-            let subtree = MetaTemplate { tokens, delimiter };
-            Op::Subtree(subtree)
+            Op::Subtree { tokens: MetaTemplate(tokens), delimiter: subtree.delimiter }
         }
     };
     Ok(res)