Fixup comments

7 files changed, 38 insertions, 26 deletions

diff --git a/crates/mbe/src/syntax_bridge.rs b/crates/mbe/src/syntax_bridge.rs
index a4e3efaeb52..fb531340108 100644
--- a/crates/mbe/src/syntax_bridge.rs
+++ b/crates/mbe/src/syntax_bridge.rs
@@ -95,7 +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 { has_pseudo_dot } => tree_sink.float_split(has_pseudo_dot),
+            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()),
@@ -797,6 +799,8 @@ 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), _)) => {
diff --git a/crates/mbe/src/to_parser_input.rs b/crates/mbe/src/to_parser_input.rs
index 6d20998bb4d..051e20b3a3f 100644
--- a/crates/mbe/src/to_parser_input.rs
+++ b/crates/mbe/src/to_parser_input.rs
@@ -47,6 +47,9 @@ pub(crate) fn to_parser_input(buffer: &TokenBuffer<'_>) -> parser::Input {
                         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();
                         }
                     }
diff --git a/crates/parser/src/event.rs b/crates/parser/src/event.rs
index fb2616cf013..577eb0967b4 100644
--- a/crates/parser/src/event.rs
+++ b/crates/parser/src/event.rs
@@ -72,11 +72,14 @@ pub(crate) enum Event {
     /// `n_raw_tokens = 2` is used to produced a single `>>`.
     Token {
         kind: SyntaxKind,
-        // Consider custom enum here?
         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 {
-        has_pseudo_dot: bool,
+        ends_in_dot: bool,
     },
     Error {
         msg: String,
@@ -128,8 +131,8 @@ pub(super) fn process(mut events: Vec<Event>) -> Output {
             Event::Token { kind, n_raw_tokens } => {
                 res.token(kind, n_raw_tokens);
             }
-            Event::FloatSplitHack { has_pseudo_dot } => {
-                res.float_split_hack(has_pseudo_dot);
+            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:?}");
             }
diff --git a/crates/parser/src/lib.rs b/crates/parser/src/lib.rs
index 9b895ff3ca6..8c5aed0232b 100644
--- a/crates/parser/src/lib.rs
+++ b/crates/parser/src/lib.rs
@@ -102,7 +102,9 @@ impl TopEntryPoint {
                 match step {
                     Step::Enter { .. } => depth += 1,
                     Step::Exit => depth -= 1,
-                    Step::FloatSplit { has_pseudo_dot } => depth -= 1 + !has_pseudo_dot as usize,
+                    Step::FloatSplit { ends_in_dot: has_pseudo_dot } => {
+                        depth -= 1 + !has_pseudo_dot as usize
+                    }
                     Step::Token { .. } | Step::Error { .. } => (),
                 }
             }
diff --git a/crates/parser/src/output.rs b/crates/parser/src/output.rs
index 9587c8cb1ba..41d4c68b2d7 100644
--- a/crates/parser/src/output.rs
+++ b/crates/parser/src/output.rs
@@ -25,7 +25,7 @@ pub struct Output {
 #[derive(Debug)]
 pub enum Step<'a> {
     Token { kind: SyntaxKind, n_input_tokens: u8 },
-    FloatSplit { has_pseudo_dot: bool },
+    FloatSplit { ends_in_dot: bool },
     Enter { kind: SyntaxKind },
     Exit,
     Error { msg: &'a str },
@@ -70,7 +70,7 @@ impl Output {
                 }
                 Self::EXIT_EVENT => Step::Exit,
                 Self::SPLIT_EVENT => {
-                    Step::FloatSplit { has_pseudo_dot: event & Self::N_INPUT_TOKEN_MASK != 0 }
+                    Step::FloatSplit { ends_in_dot: event & Self::N_INPUT_TOKEN_MASK != 0 }
                 }
                 _ => unreachable!(),
             }
@@ -84,9 +84,9 @@ impl Output {
         self.event.push(e)
     }
 
-    pub(crate) fn float_split_hack(&mut self, has_pseudo_dot: bool) {
+    pub(crate) fn float_split_hack(&mut self, ends_in_dot: bool) {
         let e = (Self::SPLIT_EVENT as u32) << Self::TAG_SHIFT
-            | ((has_pseudo_dot as u32) << Self::N_INPUT_TOKEN_SHIFT)
+            | ((ends_in_dot as u32) << Self::N_INPUT_TOKEN_SHIFT)
             | Self::EVENT_MASK;
         self.event.push(e);
     }
diff --git a/crates/parser/src/parser.rs b/crates/parser/src/parser.rs
index 0f4fa602291..280416ae7c9 100644
--- a/crates/parser/src/parser.rs
+++ b/crates/parser/src/parser.rs
@@ -182,7 +182,7 @@ impl<'t> Parser<'t> {
     }
 
     /// Advances the parser by one token
-    pub(crate) fn split_float(&mut self, marker: Marker) -> (bool, Marker) {
+    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
@@ -191,26 +191,23 @@ impl<'t> Parser<'t> {
         // `<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 has_pseudo_dot = !self.inp.is_joint(self.pos);
-        let marker = if !has_pseudo_dot {
-            let new_pos = self.start();
+        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_pos.pos - marker.pos);
+                    *forward_parent = Some(new_marker.pos - marker.pos);
                 }
                 _ => unreachable!(),
             }
-            // NOTE: This brings the start / finish pairs out of balance!
-            std::mem::forget(marker);
-            new_pos
-        } else {
-            marker
+            marker.bomb.defuse();
+            marker = new_marker;
         };
         self.pos += 1 as usize;
-        self.push_event(Event::FloatSplitHack { has_pseudo_dot });
-        (has_pseudo_dot, marker)
+        self.push_event(Event::FloatSplitHack { ends_in_dot });
+        (ends_in_dot, marker)
     }
 
     /// Advances the parser by one token, remapping its kind.
diff --git a/crates/parser/src/shortcuts.rs b/crates/parser/src/shortcuts.rs
index 21939c34943..47e4adcbbe6 100644
--- a/crates/parser/src/shortcuts.rs
+++ b/crates/parser/src/shortcuts.rs
@@ -43,10 +43,11 @@ impl<'a> LexedStr<'a> {
                         res.was_joint();
                     }
                     res.push(kind);
-                    // we set jointness for floating point numbers as a hack to inform the
-                    // parser about whether we have a `0.` or `0.1` style float
+                    // 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).split_once('.').map_or(true, |(_, it)| it.is_empty()) {
+                        if !self.text(i).ends_with('.') {
                             res.was_joint();
                         }
                     }
@@ -71,7 +72,9 @@ impl<'a> LexedStr<'a> {
                 Step::Token { kind, n_input_tokens: n_raw_tokens } => {
                     builder.token(kind, n_raw_tokens)
                 }
-                Step::FloatSplit { has_pseudo_dot } => builder.float_split(has_pseudo_dot),
+                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 } => {