Use codespan for *much* prettier error reporting.

src/bin.rs

@@ -1,5 +1,11 @@
 use clap::Parser;
-use ngr::syntax::{ParserError, Program};
+use codespan_reporting::diagnostic::Diagnostic;
+use codespan_reporting::files::SimpleFiles;
+use codespan_reporting::term;
+use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
+use ngr::error::Error;
+use ngr::syntax::Program;
+use std::fs;
 
 #[derive(Parser, Debug)]
 #[clap(author, version, about, long_about = None)]
@@ -9,21 +15,30 @@ struct CommandLineArguments {
     output: Option<String>,
 
     /// The file to parse
-    file: String
+    file: String,
 }
 
-fn real_main() -> Result<(), ParserError> {
-    let args = CommandLineArguments::parse();
-
-    let program = Program::from_file(&args.file)?;
-    println!("args: {:?}", args);
-    println!("program: {:?}", program);
-
-    Ok(())
+fn compile_file(
+    file_database: &mut SimpleFiles<String, String>,
+    initial_file_name: &str,
+) -> Result<Program, Error> {
+    let initial_file_contents = fs::read_to_string(initial_file_name)?;
+    let initial_file = file_database.add(initial_file_name.to_string(), initial_file_contents);
+    let db_version = file_database.get(initial_file)?;
+    let db_version_source = db_version.source();
+    Ok(Program::parse(initial_file, db_version_source)?)
 }
 
 fn main() {
-    if let Err(e) = real_main() {
-        println!("{}", e);
+    let args = CommandLineArguments::parse();
+    let mut file_database = SimpleFiles::new();
+    let initial_file_name = &args.file;
+
+    if let Err(e) = compile_file(&mut file_database, initial_file_name) {
+        let diagnostic = Diagnostic::from(e);
+        let writer = StandardStream::stderr(ColorChoice::Auto);
+        let config = codespan_reporting::term::Config::default();
+
+        term::emit(&mut writer.lock(), &config, &file_database, &diagnostic).unwrap();
     }
 }