all lex errors have a position now

src/edit.rs

@@ -207,7 +207,7 @@ impl Editor {
 
     /// reads one command from the editor. This function blocks until the user has entered an
     /// entire command.
-    pub fn read_command(&mut self, _history: &mut History) -> Result<Option<String>> {
+    pub fn read_command(&mut self, history: &mut History) -> Result<Option<String>> {
         use input::Event::*;
 
         loop {
@@ -266,6 +266,7 @@ impl Editor {
         match esc {
             Left => self.back(1)?,
             Right => self.forward(1)?,
+            Up => self.prev_history()?,
             Home => self.seek_left()?,
             End => self.seek_right()?,
             esc => debug!("  Ignored escape: {esc:?}"),
@@ -422,4 +423,8 @@ impl Editor {
         self.display.reset()?;
         Ok(())
     }
+
+    fn prev_history(&mut self) -> Result<()> {
+        Ok(())
+    }
 }

src/error.rs

@@ -1,4 +1,7 @@
-use crate::{lex::Token, topo::Glyph};
+use crate::{
+    lex::Token,
+    topo::{Glyph, Position},
+};
 use std::io;
 use thiserror::Error;
 use windows::Win32::Foundation::{GetLastError, BOOL};
@@ -36,21 +39,32 @@ pub enum LexError {
     UnexpectedCharacterInGlob(Glyph),
 
     #[error("unexpected eof")]
-    UnexpectedEOF,
+    UnexpectedEOF(Position),
 
-    #[error("not yet supported: {0}")]
-    NotYetSupported(String),
+    #[error("not yet supported: {1}")]
+    NotYetSupported(Position, String),
 }
 
 impl LexError {
-    pub fn not_yet(msg: &str) -> Self {
-        LexError::NotYetSupported(msg.to_string())
+    pub fn not_yet(p: Position, msg: &str) -> Self {
+        LexError::NotYetSupported(p, msg.to_string())
+    }
+
+    fn position(&self) -> Position {
+        use LexError::*;
+        match self {
+            UnexpectedCharacter(g) => g.position,
+            UnexpectedCharacterInBareString(g) => g.position,
+            UnexpectedCharacterInGlob(g) => g.position,
+            UnexpectedEOF(p) => *p,
+            NotYetSupported(p, _) => *p,
+        }
     }
 }
 
 #[derive(Debug, Error)]
 pub enum ParseError {
-    #[error("lex error")]
+    #[error("lex error at line {line}, column {col}", line=.0.position().line, col=.0.position().column)]
     LexError(#[from] LexError),
 
     #[error("Unexpected Token: {0:?}")]

src/history.rs

@@ -1,7 +1,13 @@
-pub struct History {}
+pub struct History {
+    events: Vec<String>,
+}
 
 impl History {
     pub fn new() -> Self {
-        Self {}
+        Self { events: Vec::new() }
+    }
+
+    pub fn add<S: Into<String>>(&mut self, event: S) {
+        self.events.push(event.into());
     }
 }

src/lex.rs

@@ -154,7 +154,7 @@ impl<'text> Tokenizer<'text> {
         }
 
         if progress.is_empty() {
-            Err(LexError::UnexpectedEOF)
+            Err(LexError::UnexpectedEOF(self.source.next_position))
         } else {
             Ok(Token::Word(progress.into()))
         }
@@ -175,22 +175,31 @@ impl<'text> Tokenizer<'text> {
         }
 
         if progress.is_empty() {
-            Err(LexError::UnexpectedEOF)
+            Err(LexError::UnexpectedEOF(self.source.next_position))
         } else {
             Ok(Token::Glob(progress.into()))
         }
     }
 
     fn lex_raw_string(&mut self, _progress: Vec<Glyph>) -> Result<Token, LexError> {
-        Err(LexError::not_yet("raw strings not done yet"))
+        Err(LexError::not_yet(
+            self.source.next_position,
+            "raw strings not done yet",
+        ))
     }
 
     fn lex_interp_string(&mut self, _progress: Vec<Glyph>) -> Result<Token, LexError> {
-        Err(LexError::not_yet("interpreted strings not done yet"))
+        Err(LexError::not_yet(
+            self.source.next_position,
+            "interpreted strings not done yet",
+        ))
     }
 
     fn lex_var(&mut self, _progress: Vec<Glyph>) -> Result<Token, LexError> {
-        Err(LexError::not_yet("variables are not done yet"))
+        Err(LexError::not_yet(
+            self.source.next_position,
+            "variables are not done yet",
+        ))
     }
 }
 

src/topo.rs

@@ -47,6 +47,12 @@ impl fmt::Debug for Position {
     }
 }
 
+impl fmt::Display for Position {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        (self as &dyn fmt::Debug).fmt(f)
+    }
+}
+
 /// A Glyph represents a character occurring at some specific position in some input text.
 #[derive(PartialEq, Clone)]
 pub struct Glyph {
@@ -97,7 +103,7 @@ pub struct Glyphs<'text> {
     source: Chars<'text>,
 
     /// the position of the next character in the source text
-    next_position: Position,
+    pub(crate) next_position: Position,
 
     /// the number of bytes we've read from our input document so far
     bytes_read: u64,
@@ -153,7 +159,8 @@ impl<'text> Glyphs<'text> {
 
     /// takes the next character from our input text
     pub fn pop(&mut self) -> Result<Glyph, LexError> {
-        self.next().ok_or(LexError::UnexpectedEOF)
+        self.next()
+            .ok_or(LexError::UnexpectedEOF(self.next_position))
     }
 
     /// returns a reference to a character in our lookahead buffer at a given position. This allows