Add better error messaging

src/errors.rs

@@ -1,4 +1,6 @@
 use super::parser::Position;
+use std::fmt;
+use std::fmt::Display;
 use std::io;
 
 #[derive(Debug)]
@@ -15,10 +17,25 @@ impl From<io::Error> for GenericError {
 #[derive(Debug)]
 pub enum CompilerError {
     Fatal,
-    PeekFailed,
     ExpectedToken(Position, char),
     ExpectedExpression(Position, Box<CompilerError>),
     ExpectedIdent(Position),
     ExpectedStatement(Position),
     ExpectedPattern(Position),
 }
+
+impl Display for CompilerError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let text = match self {
+            CompilerError::Fatal => "Fatal error".to_string(),
+            CompilerError::ExpectedToken(pos, c) => format!("Expected token '{}' at {}", c, pos),
+            CompilerError::ExpectedExpression(pos, err) => {
+                format!("Expected expression at {}.\n  {}", pos, err)
+            }
+            CompilerError::ExpectedIdent(pos) => format!("Expected ident at {}", pos),
+            CompilerError::ExpectedStatement(pos) => format!("Expected statement at {}", pos),
+            CompilerError::ExpectedPattern(pos) => format!("Expected pattern at {}", pos),
+        };
+        write!(f, "{}", text)
+    }
+}

src/main.rs

@@ -9,5 +9,8 @@ use std::path::Path;
 fn main() {
     let path = Path::new("reid_src/test.reid");
     let reid = Parser::from(open_file(&path).ok().unwrap()).parse();
-    println!("Parsed: {:?}", reid);
+    if let Err(error) = reid {
+        eprintln!("Syntax error: {}", error);
+        std::process::exit(1);
+    }
 }

src/parser.rs

@@ -1,5 +1,8 @@
 use super::errors::CompilerError;
 
+use std::fmt;
+use std::fmt::Display;
+
 type Ident = String;
 
 const ALLOWED_IDENT_CHARS: [char; 38] = [
@@ -325,3 +328,9 @@ impl Expect<'_> {
 
 #[derive(Debug, Copy, Clone)]
 pub struct Position(usize, usize);
+
+impl Display for Position {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "line {}, column {}", self.0, self.1)
+    }
+}