feat: add better diagnostic rendering

src/frontend/token.rs

@@ -1,4 +1,4 @@
-use std::fmt::Display;
+use std::{fmt::Display, ops::Range};
 
 /// A half-open interval `[start, end)` representing a location in the source text.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -23,6 +23,12 @@ impl Span {
     }
 }
 
+impl From<Span> for Range<usize> {
+    fn from(value: Span) -> Self {
+        value.start..value.end
+    }
+}
+
 /// A fundamental, categorized unit of source code produced during lexical analysis.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Token<'src> {

src/main.rs

@@ -1,12 +1,16 @@
 use std::{fs::read_to_string, path::PathBuf, process::exit};
 
-use clap::Parser as ClapParser;
+use codespan_reporting::diagnostic::{Diagnostic, Label};
+use codespan_reporting::files::SimpleFile;
+use codespan_reporting::term;
+use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
 
 use crate::frontend::parser::Parser;
 use crate::frontend::sema::Sema;
 use crate::middle::builder::MirBuilder;
 use crate::middle::dce::eliminate_dead_code;
 use crate::middle::fold::fold_constants;
+use clap::Parser as ClapParser;
 
 pub mod backend;
 pub mod frontend;
@@ -37,12 +41,20 @@ fn main() {
         exit(1);
     });
 
+    let writer = StandardStream::stderr(ColorChoice::Always);
+    let config = term::Config::default();
+    let file = SimpleFile::new(&cli.input, &content);
+
     let mut parser = Parser::new(&content);
     let module = parser.parse_module();
 
     if let Some(errors) = parser.errors() {
         for error in errors {
-            eprintln!("{:?}", error);
+            let diagnostic = Diagnostic::error()
+                .with_message(error.message)
+                .with_label(Label::primary((), error.span));
+
+            term::emit_to_write_style(&mut writer.lock(), &config, &file, &diagnostic).unwrap();
         }
 
         exit(1);
@@ -53,7 +65,11 @@ fn main() {
 
     if let Some(errors) = sema.errors() {
         for error in errors {
-            eprintln!("{:?}", error);
+            let diagnostic = Diagnostic::error()
+                .with_message(error.message)
+                .with_label(Label::primary((), error.span));
+
+            term::emit_to_write_style(&mut writer.lock(), &config, &file, &diagnostic).unwrap();
         }
 
         exit(1);
@@ -64,7 +80,11 @@ fn main() {
     let warnings = eliminate_dead_code(&mut mir_module);
 
     for warning in warnings {
-        eprintln!("Warning: {} at {:?}", warning.message, warning.span);
+        let diagnostic = Diagnostic::warning()
+            .with_message(warning.message)
+            .with_label(Label::primary((), warning.span));
+
+        term::emit_to_write_style(&mut writer.lock(), &config, &file, &diagnostic).unwrap();
     }
 
     let backend = CraneliftBackend::new();