Auto merge of #14084 - Veykril:float-parse, r=Veykril

fix: Fix parsing of nested tuple field accesses in a cursed way

This is absolutely terrible but seems to work. Macro fragment parsing comes next.

crates/hir-def/src/item_tree.rs

@@ -111,7 +111,8 @@ impl ItemTree {
             Some(node) => node,
             None => return Default::default(),
         };
-        if never!(syntax.kind() == SyntaxKind::ERROR) {
+        if never!(syntax.kind() == SyntaxKind::ERROR, "{:?} from {:?} {}", file_id, syntax, syntax)
+        {
             // FIXME: not 100% sure why these crop up, but return an empty tree to avoid a panic
             return Default::default();
         }
@@ -133,7 +134,7 @@ impl ItemTree {
                     ctx.lower_macro_stmts(stmts)
                 },
                 _ => {
-                    panic!("cannot create item tree from {syntax:?} {syntax}");
+                    panic!("cannot create item tree for file {file_id:?} from {syntax:?} {syntax}");
                 },
             }
         };

crates/hir-def/src/macro_expansion_tests/mbe.rs

@@ -97,6 +97,41 @@ fn#19 main#20(#21)#21 {#22
 "##]],
     );
 }
+#[test]
+fn float_field_acces_macro_input() {
+    check(
+        r#"
+macro_rules! foo {
+    ($expr:expr) => {
+        fn foo() {
+            $expr;
+        }
+    };
+}
+foo!(x .0.1);
+foo!(x .2. 3);
+foo!(x .4 .5);
+"#,
+        expect![[r#"
+macro_rules! foo {
+    ($expr:expr) => {
+        fn foo() {
+            $expr;
+        }
+    };
+}
+fn foo() {
+    (x.0.1);
+}
+fn foo() {
+    (x.2.3);
+}
+fn foo() {
+    (x.4.5);
+}
+"#]],
+    );
+}
 
 #[test]
 fn mbe_smoke_test() {

crates/hir-def/src/macro_expansion_tests/proc_macros.rs

@@ -104,7 +104,7 @@ macro_rules! id {
         $($t)*
     };
 }
-id /*+errors*/! {
+id! {
     #[proc_macros::identity]
     impl Foo for WrapBj {
         async fn foo(&self) {
@@ -113,18 +113,17 @@ id /*+errors*/! {
     }
 }
 "#,
-        expect![[r##"
+        expect![[r#"
 macro_rules! id {
     ($($t:tt)*) => {
         $($t)*
     };
 }
-/* parse error: expected SEMICOLON */
 #[proc_macros::identity] impl Foo for WrapBj {
     async fn foo(&self ) {
         self .0.id().await ;
     }
 }
-"##]],
+"#]],
     );
 }

crates/mbe/src/syntax_bridge.rs

@@ -95,6 +95,9 @@ pub fn token_tree_to_syntax_node(
             parser::Step::Token { kind, n_input_tokens: n_raw_tokens } => {
                 tree_sink.token(kind, n_raw_tokens)
             }
+            parser::Step::FloatSplit { ends_in_dot: has_pseudo_dot } => {
+                tree_sink.float_split(has_pseudo_dot)
+            }
             parser::Step::Enter { kind } => tree_sink.start_node(kind),
             parser::Step::Exit => tree_sink.finish_node(),
             parser::Step::Error { msg } => tree_sink.error(msg.to_string()),
@@ -796,6 +799,43 @@ fn delim_to_str(d: tt::DelimiterKind, closing: bool) -> Option<&'static str> {
 }
 
 impl<'a> TtTreeSink<'a> {
+    /// Parses a float literal as if it was a one to two name ref nodes with a dot inbetween.
+    /// This occurs when a float literal is used as a field access.
+    fn float_split(&mut self, has_pseudo_dot: bool) {
+        let (text, _span) = match self.cursor.token_tree() {
+            Some(tt::buffer::TokenTreeRef::Leaf(tt::Leaf::Literal(lit), _)) => {
+                (lit.text.as_str(), lit.span)
+            }
+            _ => unreachable!(),
+        };
+        match text.split_once('.') {
+            Some((left, right)) => {
+                assert!(!left.is_empty());
+                self.inner.start_node(SyntaxKind::NAME_REF);
+                self.inner.token(SyntaxKind::INT_NUMBER, left);
+                self.inner.finish_node();
+
+                // here we move the exit up, the original exit has been deleted in process
+                self.inner.finish_node();
+
+                self.inner.token(SyntaxKind::DOT, ".");
+
+                if has_pseudo_dot {
+                    assert!(right.is_empty(), "{left}.{right}");
+                } else {
+                    self.inner.start_node(SyntaxKind::NAME_REF);
+                    self.inner.token(SyntaxKind::INT_NUMBER, right);
+                    self.inner.finish_node();
+
+                    // the parser creates an unbalanced start node, we are required to close it here
+                    self.inner.finish_node();
+                }
+            }
+            None => unreachable!(),
+        }
+        self.cursor = self.cursor.bump();
+    }
+
     fn token(&mut self, kind: SyntaxKind, mut n_tokens: u8) {
         if kind == LIFETIME_IDENT {
             n_tokens = 2;

crates/mbe/src/to_parser_input.rs

@@ -45,6 +45,13 @@ pub(crate) fn to_parser_input(buffer: &TokenBuffer<'_>) -> parser::Input {
                             .unwrap_or_else(|| panic!("Fail to convert given literal {:#?}", &lit));
 
                         res.push(kind);
+
+                        if kind == FLOAT_NUMBER && !inner_text.ends_with('.') {
+                            // Tag the token as joint if it is float with a fractional part
+                            // we use this jointness to inform the parser about what token split
+                            // event to emit when we encounter a float literal in a field access
+                            res.was_joint();
+                        }
                     }
                     tt::Leaf::Ident(ident) => match ident.text.as_ref() {
                         "_" => res.push(T![_]),

crates/mbe/src/tt_iter.rs

@@ -150,6 +150,11 @@ impl<'a> TtIter<'a> {
                         cursor = cursor.bump_subtree();
                     }
                 }
+                parser::Step::FloatSplit { .. } => {
+                    // FIXME: We need to split the tree properly here, but mutating the token trees
+                    // in the buffer is somewhat tricky to pull off.
+                    cursor = cursor.bump_subtree();
+                }
                 parser::Step::Enter { .. } | parser::Step::Exit => (),
                 parser::Step::Error { .. } => error = true,
             }
@@ -166,19 +171,18 @@ impl<'a> TtIter<'a> {
 
         if cursor.is_root() {
             while curr != cursor {
-                if let Some(token) = curr.token_tree() {
+                let Some(token) = curr.token_tree() else { break };
-                    res.push(token);
+                res.push(token.cloned());
-                }
                 curr = curr.bump();
             }
         }
+
         self.inner = self.inner.as_slice()[res.len()..].iter();
         let res = match res.len() {
-            1 => Some(res[0].cloned()),
+            0 | 1 => res.pop(),
-            0 => None,
             _ => Some(tt::TokenTree::Subtree(tt::Subtree {
                 delimiter: tt::Delimiter::unspecified(),
-                token_trees: res.into_iter().map(|it| it.cloned()).collect(),
+                token_trees: res,
             })),
         };
         ExpandResult { value: res, err }

crates/parser/src/event.rs

@@ -74,7 +74,13 @@ pub(crate) enum Event {
         kind: SyntaxKind,
         n_raw_tokens: u8,
     },
-
+    /// When we parse `foo.0.0` or `foo. 0. 0` the lexer will hand us a float literal
+    /// instead of an integer literal followed by a dot as the lexer has no contextual knowledge.
+    /// This event instructs whatever consumes the events to split the float literal into
+    /// the corresponding parts.
+    FloatSplitHack {
+        ends_in_dot: bool,
+    },
     Error {
         msg: String,
     },
@@ -125,6 +131,11 @@ pub(super) fn process(mut events: Vec<Event>) -> Output {
             Event::Token { kind, n_raw_tokens } => {
                 res.token(kind, n_raw_tokens);
             }
+            Event::FloatSplitHack { ends_in_dot } => {
+                res.float_split_hack(ends_in_dot);
+                let ev = mem::replace(&mut events[i + 1], Event::tombstone());
+                assert!(matches!(ev, Event::Finish), "{ev:?}");
+            }
             Event::Error { msg } => res.error(msg),
         }
     }

crates/parser/src/grammar/expressions.rs

@@ -379,7 +379,7 @@ fn postfix_expr(
             // }
             T!['('] if allow_calls => call_expr(p, lhs),
             T!['['] if allow_calls => index_expr(p, lhs),
-            T![.] => match postfix_dot_expr(p, lhs) {
+            T![.] => match postfix_dot_expr::<false>(p, lhs) {
                 Ok(it) => it,
                 Err(it) => {
                     lhs = it;
@@ -393,14 +393,20 @@ fn postfix_expr(
         block_like = BlockLike::NotBlock;
     }
     return (lhs, block_like);
+}
 
-    fn postfix_dot_expr(
+fn postfix_dot_expr<const FLOAT_RECOVERY: bool>(
     p: &mut Parser<'_>,
     lhs: CompletedMarker,
 ) -> Result<CompletedMarker, CompletedMarker> {
+    if !FLOAT_RECOVERY {
         assert!(p.at(T![.]));
-        if p.nth(1) == IDENT && (p.nth(2) == T!['('] || p.nth_at(2, T![::])) {
+    }
-            return Ok(method_call_expr(p, lhs));
+    let nth1 = if FLOAT_RECOVERY { 0 } else { 1 };
+    let nth2 = if FLOAT_RECOVERY { 1 } else { 2 };
+
+    if p.nth(nth1) == IDENT && (p.nth(nth2) == T!['('] || p.nth_at(nth2, T![::])) {
+        return Ok(method_call_expr::<FLOAT_RECOVERY>(p, lhs));
     }
 
     // test await_expr
@@ -408,10 +414,14 @@ fn postfix_expr(
     //     x.await;
     //     x.0.await;
     //     x.0().await?.hello();
+    //     x.0.0.await;
+    //     x.0. await;
     // }
-        if p.nth(1) == T![await] {
+    if p.nth(nth1) == T![await] {
         let m = lhs.precede(p);
+        if !FLOAT_RECOVERY {
             p.bump(T![.]);
+        }
         p.bump(T![await]);
         return Ok(m.complete(p, AWAIT_EXPR));
     }
@@ -420,8 +430,7 @@ fn postfix_expr(
         return Err(lhs);
     }
 
-        Ok(field_expr(p, lhs))
+    field_expr::<FLOAT_RECOVERY>(p, lhs)
-    }
 }
 
 // test call_expr
@@ -455,11 +464,22 @@ fn index_expr(p: &mut Parser<'_>, lhs: CompletedMarker) -> CompletedMarker {
 // fn foo() {
 //     x.foo();
 //     y.bar::<T>(1, 2,);
+//     x.0.0.call();
+//     x.0. call();
 // }
-fn method_call_expr(p: &mut Parser<'_>, lhs: CompletedMarker) -> CompletedMarker {
+fn method_call_expr<const FLOAT_RECOVERY: bool>(
+    p: &mut Parser<'_>,
+    lhs: CompletedMarker,
+) -> CompletedMarker {
+    if FLOAT_RECOVERY {
+        assert!(p.nth(0) == IDENT && (p.nth(1) == T!['('] || p.nth_at(1, T![::])));
+    } else {
         assert!(p.at(T![.]) && p.nth(1) == IDENT && (p.nth(2) == T!['('] || p.nth_at(2, T![::])));
+    }
     let m = lhs.precede(p);
-    p.bump_any();
+    if !FLOAT_RECOVERY {
+        p.bump(T![.]);
+    }
     name_ref(p);
     generic_args::opt_generic_arg_list(p, true);
     if p.at(T!['(']) {
@@ -472,21 +492,35 @@ fn method_call_expr(p: &mut Parser<'_>, lhs: CompletedMarker) -> CompletedMarker
 // fn foo() {
 //     x.foo;
 //     x.0.bar;
+//     x.0.1;
+//     x.0. bar;
 //     x.0();
 // }
-fn field_expr(p: &mut Parser<'_>, lhs: CompletedMarker) -> CompletedMarker {
+fn field_expr<const FLOAT_RECOVERY: bool>(
+    p: &mut Parser<'_>,
+    lhs: CompletedMarker,
+) -> Result<CompletedMarker, CompletedMarker> {
+    if !FLOAT_RECOVERY {
         assert!(p.at(T![.]));
+    }
     let m = lhs.precede(p);
+    if !FLOAT_RECOVERY {
         p.bump(T![.]);
+    }
     if p.at(IDENT) || p.at(INT_NUMBER) {
         name_ref_or_index(p);
     } else if p.at(FLOAT_NUMBER) {
-        // FIXME: How to recover and instead parse INT + T![.]?
+        return match p.split_float(m) {
-        p.bump_any();
+            (true, m) => {
+                let lhs = m.complete(p, FIELD_EXPR);
+                postfix_dot_expr::<true>(p, lhs)
+            }
+            (false, m) => Ok(m.complete(p, FIELD_EXPR)),
+        };
     } else {
         p.error("expected field name or number");
     }
-    m.complete(p, FIELD_EXPR)
+    Ok(m.complete(p, FIELD_EXPR))
 }
 
 // test try_expr

crates/parser/src/lib.rs

@@ -102,10 +102,14 @@ impl TopEntryPoint {
                 match step {
                     Step::Enter { .. } => depth += 1,
                     Step::Exit => depth -= 1,
+                    Step::FloatSplit { ends_in_dot: has_pseudo_dot } => {
+                        depth -= 1 + !has_pseudo_dot as usize
+                    }
                     Step::Token { .. } | Step::Error { .. } => (),
                 }
             }
             assert!(!first, "no tree at all");
+            assert_eq!(depth, 0, "unbalanced tree");
         }
 
         res

crates/parser/src/output.rs

@@ -25,53 +25,88 @@ pub struct Output {
 #[derive(Debug)]
 pub enum Step<'a> {
     Token { kind: SyntaxKind, n_input_tokens: u8 },
+    FloatSplit { ends_in_dot: bool },
     Enter { kind: SyntaxKind },
     Exit,
     Error { msg: &'a str },
 }
 
 impl Output {
+    const EVENT_MASK: u32 = 0b1;
+    const TAG_MASK: u32 = 0x0000_00F0;
+    const N_INPUT_TOKEN_MASK: u32 = 0x0000_FF00;
+    const KIND_MASK: u32 = 0xFFFF_0000;
+
+    const ERROR_SHIFT: u32 = Self::EVENT_MASK.trailing_ones();
+    const TAG_SHIFT: u32 = Self::TAG_MASK.trailing_zeros();
+    const N_INPUT_TOKEN_SHIFT: u32 = Self::N_INPUT_TOKEN_MASK.trailing_zeros();
+    const KIND_SHIFT: u32 = Self::KIND_MASK.trailing_zeros();
+
+    const TOKEN_EVENT: u8 = 0;
+    const ENTER_EVENT: u8 = 1;
+    const EXIT_EVENT: u8 = 2;
+    const SPLIT_EVENT: u8 = 3;
+
     pub fn iter(&self) -> impl Iterator<Item = Step<'_>> {
         self.event.iter().map(|&event| {
-            if event & 0b1 == 0 {
+            if event & Self::EVENT_MASK == 0 {
-                return Step::Error { msg: self.error[(event as usize) >> 1].as_str() };
+                return Step::Error {
+                    msg: self.error[(event as usize) >> Self::ERROR_SHIFT].as_str(),
+                };
             }
-            let tag = ((event & 0x0000_00F0) >> 4) as u8;
+            let tag = ((event & Self::TAG_MASK) >> Self::TAG_SHIFT) as u8;
             match tag {
-                0 => {
+                Self::TOKEN_EVENT => {
-                    let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into();
+                    let kind: SyntaxKind =
-                    let n_input_tokens = ((event & 0x0000_FF00) >> 8) as u8;
+                        (((event & Self::KIND_MASK) >> Self::KIND_SHIFT) as u16).into();
+                    let n_input_tokens =
+                        ((event & Self::N_INPUT_TOKEN_MASK) >> Self::N_INPUT_TOKEN_SHIFT) as u8;
                     Step::Token { kind, n_input_tokens }
                 }
-                1 => {
+                Self::ENTER_EVENT => {
-                    let kind: SyntaxKind = (((event & 0xFFFF_0000) >> 16) as u16).into();
+                    let kind: SyntaxKind =
+                        (((event & Self::KIND_MASK) >> Self::KIND_SHIFT) as u16).into();
                     Step::Enter { kind }
                 }
-                2 => Step::Exit,
+                Self::EXIT_EVENT => Step::Exit,
+                Self::SPLIT_EVENT => {
+                    Step::FloatSplit { ends_in_dot: event & Self::N_INPUT_TOKEN_MASK != 0 }
+                }
                 _ => unreachable!(),
             }
         })
     }
 
     pub(crate) fn token(&mut self, kind: SyntaxKind, n_tokens: u8) {
-        let e = ((kind as u16 as u32) << 16) | ((n_tokens as u32) << 8) | 1;
+        let e = ((kind as u16 as u32) << Self::KIND_SHIFT)
+            | ((n_tokens as u32) << Self::N_INPUT_TOKEN_SHIFT)
+            | Self::EVENT_MASK;
         self.event.push(e)
     }
 
+    pub(crate) fn float_split_hack(&mut self, ends_in_dot: bool) {
+        let e = (Self::SPLIT_EVENT as u32) << Self::TAG_SHIFT
+            | ((ends_in_dot as u32) << Self::N_INPUT_TOKEN_SHIFT)
+            | Self::EVENT_MASK;
+        self.event.push(e);
+    }
+
     pub(crate) fn enter_node(&mut self, kind: SyntaxKind) {
-        let e = ((kind as u16 as u32) << 16) | (1 << 4) | 1;
+        let e = ((kind as u16 as u32) << Self::KIND_SHIFT)
+            | ((Self::ENTER_EVENT as u32) << Self::TAG_SHIFT)
+            | Self::EVENT_MASK;
         self.event.push(e)
     }
 
     pub(crate) fn leave_node(&mut self) {
-        let e = 2 << 4 | 1;
+        let e = (Self::EXIT_EVENT as u32) << Self::TAG_SHIFT | Self::EVENT_MASK;
         self.event.push(e)
     }
 
     pub(crate) fn error(&mut self, error: String) {
         let idx = self.error.len();
         self.error.push(error);
-        let e = (idx as u32) << 1;
+        let e = (idx as u32) << Self::ERROR_SHIFT;
         self.event.push(e);
     }
 }

crates/parser/src/parser.rs

@@ -181,6 +181,35 @@ impl<'t> Parser<'t> {
         self.do_bump(kind, 1);
     }
 
+    /// Advances the parser by one token
+    pub(crate) fn split_float(&mut self, mut marker: Marker) -> (bool, Marker) {
+        assert!(self.at(SyntaxKind::FLOAT_NUMBER));
+        // we have parse `<something>.`
+        // `<something>`.0.1
+        // here we need to insert an extra event
+        //
+        // `<something>`. 0. 1;
+        // here we need to change the follow up parse, the return value will cause us to emulate a dot
+        // the actual splitting happens later
+        let ends_in_dot = !self.inp.is_joint(self.pos);
+        if !ends_in_dot {
+            let new_marker = self.start();
+            let idx = marker.pos as usize;
+            match &mut self.events[idx] {
+                Event::Start { forward_parent, kind } => {
+                    *kind = SyntaxKind::FIELD_EXPR;
+                    *forward_parent = Some(new_marker.pos - marker.pos);
+                }
+                _ => unreachable!(),
+            }
+            marker.bomb.defuse();
+            marker = new_marker;
+        };
+        self.pos += 1 as usize;
+        self.push_event(Event::FloatSplitHack { ends_in_dot });
+        (ends_in_dot, marker)
+    }
+
     /// Advances the parser by one token, remapping its kind.
     /// This is useful to create contextual keywords from
     /// identifiers. For example, the lexer creates a `union`

crates/parser/src/shortcuts.rs

@@ -43,7 +43,16 @@ impl<'a> LexedStr<'a> {
                         res.was_joint();
                     }
                     res.push(kind);
+                    // Tag the token as joint if it is float with a fractional part
+                    // we use this jointness to inform the parser about what token split
+                    // event to emit when we encounter a float literal in a field access
+                    if kind == SyntaxKind::FLOAT_NUMBER {
+                        if !self.text(i).ends_with('.') {
+                            res.was_joint();
                         }
+                    }
+                }
+
                 was_joint = true;
             }
         }
@@ -63,6 +72,9 @@ impl<'a> LexedStr<'a> {
                 Step::Token { kind, n_input_tokens: n_raw_tokens } => {
                     builder.token(kind, n_raw_tokens)
                 }
+                Step::FloatSplit { ends_in_dot: has_pseudo_dot } => {
+                    builder.float_split(has_pseudo_dot)
+                }
                 Step::Enter { kind } => builder.enter(kind),
                 Step::Exit => builder.exit(),
                 Step::Error { msg } => {
@@ -109,6 +121,16 @@ impl Builder<'_, '_> {
         self.do_token(kind, n_tokens as usize);
     }
 
+    fn float_split(&mut self, has_pseudo_dot: bool) {
+        match mem::replace(&mut self.state, State::Normal) {
+            State::PendingEnter => unreachable!(),
+            State::PendingExit => (self.sink)(StrStep::Exit),
+            State::Normal => (),
+        }
+        self.eat_trivias();
+        self.do_float_split(has_pseudo_dot);
+    }
+
     fn enter(&mut self, kind: SyntaxKind) {
         match mem::replace(&mut self.state, State::Normal) {
             State::PendingEnter => {
@@ -164,6 +186,37 @@ impl Builder<'_, '_> {
         self.pos += n_tokens;
         (self.sink)(StrStep::Token { kind, text });
     }
+
+    fn do_float_split(&mut self, has_pseudo_dot: bool) {
+        let text = &self.lexed.range_text(self.pos..self.pos + 1);
+        self.pos += 1;
+        match text.split_once('.') {
+            Some((left, right)) => {
+                assert!(!left.is_empty());
+                (self.sink)(StrStep::Enter { kind: SyntaxKind::NAME_REF });
+                (self.sink)(StrStep::Token { kind: SyntaxKind::INT_NUMBER, text: left });
+                (self.sink)(StrStep::Exit);
+
+                // here we move the exit up, the original exit has been deleted in process
+                (self.sink)(StrStep::Exit);
+
+                (self.sink)(StrStep::Token { kind: SyntaxKind::DOT, text: "." });
+
+                if has_pseudo_dot {
+                    assert!(right.is_empty(), "{left}.{right}");
+                    self.state = State::Normal;
+                } else {
+                    (self.sink)(StrStep::Enter { kind: SyntaxKind::NAME_REF });
+                    (self.sink)(StrStep::Token { kind: SyntaxKind::INT_NUMBER, text: right });
+                    (self.sink)(StrStep::Exit);
+
+                    // the parser creates an unbalanced start node, we are required to close it here
+                    self.state = State::PendingExit;
+                }
+            }
+            None => unreachable!(),
+        }
+    }
 }
 
 fn n_attached_trivias<'a>(

crates/parser/src/tests/prefix_entries.rs

@@ -51,6 +51,9 @@ fn expr() {
     check(PrefixEntryPoint::Expr, "-1", "-1");
     check(PrefixEntryPoint::Expr, "fn foo() {}", "fn");
     check(PrefixEntryPoint::Expr, "#[attr] ()", "#[attr] ()");
+    check(PrefixEntryPoint::Expr, "foo.0", "foo.0");
+    check(PrefixEntryPoint::Expr, "foo.0.1", "foo.0.1");
+    check(PrefixEntryPoint::Expr, "foo.0. foo", "foo.0. foo");
 }
 
 #[test]
@@ -88,6 +91,7 @@ fn check(entry: PrefixEntryPoint, input: &str, prefix: &str) {
     for step in entry.parse(&input).iter() {
         match step {
             Step::Token { n_input_tokens, .. } => n_tokens += n_input_tokens as usize,
+            Step::FloatSplit { .. } => n_tokens += 1,
             Step::Enter { .. } | Step::Exit | Step::Error { .. } => (),
         }
     }

crates/parser/test_data/parser/inline/ok/0011_field_expr.rast

@@ -40,6 +40,39 @@ SOURCE_FILE
               IDENT "bar"
           SEMICOLON ";"
         WHITESPACE "\n    "
+        EXPR_STMT
+          FIELD_EXPR
+            FIELD_EXPR
+              PATH_EXPR
+                PATH
+                  PATH_SEGMENT
+                    NAME_REF
+                      IDENT "x"
+              DOT "."
+              NAME_REF
+                INT_NUMBER "0"
+            DOT "."
+            NAME_REF
+              INT_NUMBER "1"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          FIELD_EXPR
+            FIELD_EXPR
+              PATH_EXPR
+                PATH
+                  PATH_SEGMENT
+                    NAME_REF
+                      IDENT "x"
+              DOT "."
+              NAME_REF
+                INT_NUMBER "0"
+            DOT "."
+            WHITESPACE " "
+            NAME_REF
+              IDENT "bar"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
         EXPR_STMT
           CALL_EXPR
             FIELD_EXPR

crates/parser/test_data/parser/inline/ok/0011_field_expr.rs

@@ -1,5 +1,7 @@
 fn foo() {
     x.foo;
     x.0.bar;
+    x.0.1;
+    x.0. bar;
     x.0();
 }

crates/parser/test_data/parser/inline/ok/0107_method_call_expr.rast

@@ -59,5 +59,48 @@ SOURCE_FILE
               R_PAREN ")"
           SEMICOLON ";"
         WHITESPACE "\n    "
+        EXPR_STMT
+          METHOD_CALL_EXPR
+            FIELD_EXPR
+              FIELD_EXPR
+                PATH_EXPR
+                  PATH
+                    PATH_SEGMENT
+                      NAME_REF
+                        IDENT "x"
+                DOT "."
+                NAME_REF
+                  INT_NUMBER "0"
+              DOT "."
+              NAME_REF
+                INT_NUMBER "0"
+            DOT "."
+            NAME_REF
+              IDENT "call"
+            ARG_LIST
+              L_PAREN "("
+              R_PAREN ")"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          METHOD_CALL_EXPR
+            FIELD_EXPR
+              PATH_EXPR
+                PATH
+                  PATH_SEGMENT
+                    NAME_REF
+                      IDENT "x"
+              DOT "."
+              NAME_REF
+                INT_NUMBER "0"
+            DOT "."
+            WHITESPACE " "
+            NAME_REF
+              IDENT "call"
+            ARG_LIST
+              L_PAREN "("
+              R_PAREN ")"
+          SEMICOLON ";"
+        WHITESPACE "\n"
         R_CURLY "}"
   WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0107_method_call_expr.rs

@@ -1,4 +1,6 @@
 fn foo() {
     x.foo();
     y.bar::<T>(1, 2,);
+    x.0.0.call();
+    x.0. call();
 }

crates/parser/test_data/parser/inline/ok/0137_await_expr.rast

@@ -66,5 +66,40 @@ SOURCE_FILE
               R_PAREN ")"
           SEMICOLON ";"
         WHITESPACE "\n    "
+        EXPR_STMT
+          AWAIT_EXPR
+            FIELD_EXPR
+              FIELD_EXPR
+                PATH_EXPR
+                  PATH
+                    PATH_SEGMENT
+                      NAME_REF
+                        IDENT "x"
+                DOT "."
+                NAME_REF
+                  INT_NUMBER "0"
+              DOT "."
+              NAME_REF
+                INT_NUMBER "0"
+            DOT "."
+            AWAIT_KW "await"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          AWAIT_EXPR
+            FIELD_EXPR
+              PATH_EXPR
+                PATH
+                  PATH_SEGMENT
+                    NAME_REF
+                      IDENT "x"
+              DOT "."
+              NAME_REF
+                INT_NUMBER "0"
+            DOT "."
+            WHITESPACE " "
+            AWAIT_KW "await"
+          SEMICOLON ";"
+        WHITESPACE "\n"
         R_CURLY "}"
   WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0137_await_expr.rs

@@ -2,4 +2,6 @@ fn foo() {
     x.await;
     x.0.await;
     x.0().await?.hello();
+    x.0.0.await;
+    x.0. await;
 }

crates/tt/src/buffer.rs

@@ -7,7 +7,12 @@ use crate::{Leaf, Subtree, TokenTree};
 struct EntryId(usize);
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
-struct EntryPtr(EntryId, usize);
+struct EntryPtr(
+    /// The index of the buffer containing the entry.
+    EntryId,
+    /// The index of the entry within the buffer.
+    usize,
+);
 
 /// Internal type which is used instead of `TokenTree` to represent a token tree
 /// within a `TokenBuffer`.
@@ -16,8 +21,8 @@ enum Entry<'t, Span> {
     // Mimicking types from proc-macro.
     Subtree(Option<&'t TokenTree<Span>>, &'t Subtree<Span>, EntryId),
     Leaf(&'t TokenTree<Span>),
-    // End entries contain a pointer to the entry from the containing
+    /// End entries contain a pointer to the entry from the containing
-    // token tree, or None if this is the outermost level.
+    /// token tree, or [`None`] if this is the outermost level.
     End(Option<EntryPtr>),
 }
 
@@ -226,8 +231,14 @@ impl<'a, Span> Cursor<'a, Span> {
     /// a cursor into that subtree
     pub fn bump_subtree(self) -> Cursor<'a, Span> {
         match self.entry() {
-            Some(Entry::Subtree(_, _, _)) => self.subtree().unwrap(),
+            Some(&Entry::Subtree(_, _, entry_id)) => {
-            _ => self.bump(),
+                Cursor::create(self.buffer, EntryPtr(entry_id, 0))
+            }
+            Some(Entry::End(exit)) => match exit {
+                Some(exit) => Cursor::create(self.buffer, *exit),
+                None => self,
+            },
+            _ => Cursor::create(self.buffer, EntryPtr(self.ptr.0, self.ptr.1 + 1)),
         }
     }