[fine] Type testing with probes and reporting

I'm proud of the test harness here actually. Also fix a bug in
checking!

fine/src/parser.rs

@@ -1,6 +1,7 @@
 // NOTE: much of this parser structure derived from
 // https://matklad.github.io/2023/05/21/resilient-ll-parsing-tutorial.html
 use crate::tokens::{Lines, Token, TokenKind, Tokens};
+use std::fmt::Write as _;
 use std::{cell::Cell, num::NonZeroU32};
 
 pub mod old; // Until I decide to delete it.
@@ -22,10 +23,22 @@ impl<'a> SyntaxTree<'a> {
         self.root
     }
 
-    pub fn add_tree(&mut self, t: Tree<'a>) -> TreeRef {
+    pub fn add_tree(&mut self, mut t: Tree<'a>) -> TreeRef {
         assert!(t.parent.is_none());
         let tr = TreeRef::from_index(self.trees.len());
 
+        t.start_pos = t
+            .children
+            .first()
+            .map(|c| c.start_position(&self))
+            .unwrap_or(0);
+
+        t.end_pos = t
+            .children
+            .last()
+            .map(|c| c.end_position(&self))
+            .unwrap_or(t.start_pos);
+
         // NOTE: Because of the difficulty of holding multiple mutable
         //       references it's this is our best chance to patch up parent
         //       pointers.
@@ -34,23 +47,52 @@ impl<'a> SyntaxTree<'a> {
                 self[*ct].parent = Some(tr);
             }
         }
+
         self.trees.push(t);
         tr
     }
 
-    pub fn dump(&self) -> String {
-        match self.root {
-            Some(r) => self[r].dump(self),
-            None => String::new(),
+    pub fn dump(&self, with_positions: bool) -> String {
+        let mut output = String::new();
+        if let Some(r) = self.root {
+            self[r].dump(self, with_positions, &mut output);
         }
+        output
     }
 
-    pub fn start_position(&self, t: TreeRef) -> Option<usize> {
-        self[t].start_position(&self)
+    pub fn start_position(&self, t: TreeRef) -> usize {
+        self[t].start_pos
     }
 
-    pub fn end_position(&self, t: TreeRef) -> Option<usize> {
-        self[t].end_position(&self)
+    pub fn end_position(&self, t: TreeRef) -> usize {
+        self[t].end_pos
+    }
+
+    pub fn find_tree_at(&self, pos: usize) -> Option<TreeRef> {
+        let mut current = self.root?;
+        let mut tree = &self[current];
+        if pos < tree.start_pos || pos >= tree.end_pos {
+            return None;
+        }
+
+        loop {
+            let mut found = false;
+            for child in &tree.children {
+                if let Child::Tree(next) = child {
+                    let next_tree = &self[*next];
+                    if pos >= next_tree.start_pos && pos < next_tree.end_pos {
+                        found = true;
+                        current = *next;
+                        tree = next_tree;
+                        break;
+                    }
+                }
+            }
+
+            if !found {
+                return Some(current);
+            }
+        }
     }
 }
 
@@ -95,6 +137,8 @@ pub enum TreeKind {
 pub struct Tree<'a> {
     pub kind: TreeKind,
     pub parent: Option<TreeRef>,
+    pub start_pos: usize,
+    pub end_pos: usize,
     pub children: Vec<Child<'a>>,
 }
 
@@ -118,41 +162,9 @@ impl<'a> Tree<'a> {
             })
             .flatten()
     }
-
-    pub fn start_position(&self, tree: &SyntaxTree<'a>) -> Option<usize> {
-        for child in &self.children {
-            let start = match child {
-                Child::Tree(tr) => tree.start_position(*tr),
-                Child::Token(tok) => Some(tok.start),
-            };
-
-            if let Some(start) = start {
-                return Some(start);
-            }
-        }
-
-        // Fundamentally no tokens in this tree. This seems *broken*.
-        None
-    }
-
-    pub fn end_position(&self, tree: &SyntaxTree<'a>) -> Option<usize> {
-        for child in self.children.iter().rev() {
-            let end = match child {
-                Child::Tree(tr) => tree.end_position(*tr),
-                Child::Token(tok) => Some(tok.start + tok.as_str().len()),
-            };
-
-            if let Some(start) = end {
-                return Some(start);
-            }
-        }
-
-        // Fundamentally no tokens in this tree. This seems *broken*.
-        None
-    }
 }
 
-#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
 pub struct TreeRef(NonZeroU32);
 
 impl TreeRef {
@@ -168,13 +180,15 @@ impl TreeRef {
 }
 
 impl<'a> Tree<'a> {
-    pub fn dump(&self, tree: &SyntaxTree<'a>) -> String {
-        let mut output = String::new();
-        output.push_str(&format!("{:?}\n", self.kind));
-        for child in self.children.iter() {
-            child.dump_rec(2, tree, &mut output);
+    pub fn dump(&self, tree: &SyntaxTree<'a>, with_positions: bool, output: &mut String) {
+        let _ = write!(output, "{:?}", self.kind);
+        if with_positions {
+            let _ = write!(output, " [{}, {})", self.start_pos, self.end_pos);
+        }
+        let _ = write!(output, "\n");
+        for child in self.children.iter() {
+            child.dump_rec(2, tree, with_positions, output);
         }
-        output
     }
 }
 
@@ -184,21 +198,52 @@ pub enum Child<'a> {
 }
 
 impl<'a> Child<'a> {
-    fn dump_rec(&self, indent: usize, tree: &SyntaxTree<'a>, output: &mut String) {
+    fn dump_rec(
+        &self,
+        indent: usize,
+        tree: &SyntaxTree<'a>,
+        with_positions: bool,
+        output: &mut String,
+    ) {
         for _ in 0..indent {
-            output.push(' ');
+            let _ = write!(output, " ");
         }
         match self {
-            Child::Token(t) => output.push_str(&format!("{:?}:'{:?}'\n", t.kind, t.as_str())),
+            Child::Token(t) => {
+                let _ = write!(output, "{:?}:'{:?}'", t.kind, t.as_str());
+                if with_positions {
+                    let _ = write!(output, " [{}, {})", t.start, t.start + t.as_str().len());
+                }
+                let _ = write!(output, "\n");
+            }
             Child::Tree(t) => {
                 let t = &tree[*t];
-                output.push_str(&format!("{:?}\n", t.kind));
+                let _ = write!(output, "{:?}", t.kind);
+                if with_positions {
+                    let _ = write!(output, " [{}, {})", t.start_pos, t.end_pos);
+                }
+                let _ = write!(output, "\n");
+
                 for child in t.children.iter() {
-                    child.dump_rec(indent + 2, tree, output);
+                    child.dump_rec(indent + 2, tree, with_positions, output);
                 }
             }
         }
     }
+
+    pub fn start_position(&self, syntax_tree: &SyntaxTree) -> usize {
+        match &self {
+            Child::Token(t) => t.start,
+            Child::Tree(t) => syntax_tree[*t].start_pos,
+        }
+    }
+
+    pub fn end_position(&self, syntax_tree: &SyntaxTree) -> usize {
+        match &self {
+            Child::Token(t) => t.start + t.as_str().len(),
+            Child::Tree(t) => syntax_tree[*t].end_pos,
+        }
+    }
 }
 
 enum ParseEvent<'a> {
@@ -373,6 +418,8 @@ impl<'a> CParser<'a> {
                 ParseEvent::Start { kind } => stack.push(Tree {
                     kind,
                     parent: None,
+                    start_pos: 0,
+                    end_pos: 0,
                     children: Vec::new(),
                 }),
 
@@ -726,6 +773,10 @@ mod tests {
     fn tree_ref_size() {
         // What's the point of doing all that work if the tree ref isn't nice
         // and "small"?
+        //
+        // TODO: This is a dumb optimization because tokens are
+        //       huge so Child is huge no matter what we do. If we retain
+        //       tokens out of line then we can re-visit this optimization.
         assert_eq!(4, std::mem::size_of::<Option<TreeRef>>());
     }
 }

fine/src/semantics.rs

@@ -51,7 +51,7 @@ impl fmt::Debug for Error {
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}:{}: {}", self.start.0, self.end.0, self.message)
+        write!(f, "{}:{}: {}", self.start.0, self.start.1, self.message)
     }
 }
 
@@ -123,14 +123,14 @@ impl fmt::Display for Type {
 pub struct Semantics<'a> {
     // TODO: Do I really want my own copy here? Should we standardize on Arc
     //       or Rc or some other nice sharing mechanism?
-    syntax_tree: SyntaxTree<'a>,
-    lines: Lines,
+    syntax_tree: &'a SyntaxTree<'a>,
+    lines: &'a Lines,
     errors: RefCell<Vec<Error>>,
     types: RefCell<HashMap<TreeRef, Type>>,
 }
 
 impl<'a> Semantics<'a> {
-    pub fn new(tree: SyntaxTree<'a>, lines: Lines) -> Self {
+    pub fn new(tree: &'a SyntaxTree<'a>, lines: &'a Lines) -> Self {
         let mut semantics = Semantics {
             syntax_tree: tree,
             lines,
@@ -148,11 +148,7 @@ impl<'a> Semantics<'a> {
         semantics
     }
 
-    pub fn syntax(&self) -> &SyntaxTree<'a> {
-        &self.syntax_tree
-    }
-
-    pub fn errors(&self) -> Vec<Error> {
+    pub fn snapshot_errors(&self) -> Vec<Error> {
         (*self.errors.borrow()).clone()
     }
 
@@ -181,18 +177,15 @@ impl<'a> Semantics<'a> {
     where
         T: ToString,
     {
-        let start = tree.start_position(&self.syntax_tree).unwrap();
-        let end = tree.start_position(&self.syntax_tree).unwrap();
-        self.report_error_span(start, end, error)
+        self.report_error_span(tree.start_pos, tree.end_pos, error)
     }
 
     fn report_error_tree_ref<T>(&self, tree: TreeRef, error: T)
     where
         T: ToString,
     {
-        let start = self.syntax_tree.start_position(tree).unwrap();
-        let end = self.syntax_tree.end_position(tree).unwrap();
-        self.report_error_span(start, end, error)
+        let tree = &self.syntax_tree[tree];
+        self.report_error_span(tree.start_pos, tree.end_pos, error)
     }
 
     fn gather_errors(&mut self, tree: TreeRef) {
@@ -259,7 +252,7 @@ impl<'a> Semantics<'a> {
         match (op.kind, argument_type) {
             (TokenKind::Plus, Type::F64) => Some(Type::F64),
             (TokenKind::Minus, Type::F64) => Some(Type::F64),
-            (TokenKind::Bang, Type::Bool) => Some(Type::F64),
+            (TokenKind::Bang, Type::Bool) => Some(Type::Bool),
 
             // This is dumb and should be punished, probably.
             (_, Type::Unreachable) => {

fine/src/tokens.rs

@@ -429,7 +429,11 @@ impl<'a> Tokens<'a> {
         };
 
         match c {
-            ' ' | '\t' | '\r' | '\n' => self.whitespace(pos),
+            ' ' | '\t' | '\r' => self.whitespace(pos),
+            '\n' => {
+                self.lines.add_line(pos);
+                self.whitespace(pos)
+            }
             '{' => self.token(pos, TokenKind::LeftBrace),
             '}' => self.token(pos, TokenKind::RightBrace),
             '[' => self.token(pos, TokenKind::LeftBracket),