Error state information

src/main.rs

@@ -1,8 +1,40 @@
-use std::{env, fs, io::{self, Write}};
+use std::{env, fs, io::{self, Write}, process::ExitCode};
+
+/// Error handler. Can be used to print error messages; will also retain the
+/// current error status.
+#[derive(Default, Debug)]
+struct ErrorHandler {
+    had_error: bool
+}
+
+impl ErrorHandler {
+    /// Check whether this handler reported an error.
+    pub fn had_error(&self) -> bool {
+        self.had_error
+    }
+
+    /// Report an error.
+    pub fn error(&mut self, line: usize, message: &str) {
+        self.report(line, "", message)
+    }
+
+    fn report(&mut self, line: usize, pos: &str, message: &str) {
+        self.had_error = true;
+        println!("[line {line}] Error{pos}: {message}")
+    }
+}
 
 /// Execute a script.
-fn run(_source: String) {
-    todo!();
+fn run(_source: String) -> ErrorHandler {
+    let error_handler = ErrorHandler::default();
+    /*
+    let scanner = Scanner::new(source);
+    let tokens = scanner.scan_tokens();
+    for token in tokens {
+        println!("{}", token);
+    }
+    */
+    error_handler
 }
 
 /// Run the REPL.
@@ -14,28 +46,31 @@ fn run_prompt() {
         print!("slox> ");
         stdout.flush().unwrap();
         let n_read = stdin.read_line(&mut buffer).expect("Failed to read from stdin");
-        match n_read {
+        let _ = match n_read {
             0 => return,
             _ => run(buffer.clone()),
-        }
+        };
     }
 }
 
 /// Load a file and run the script it contains.
-fn run_file(file: &str) {
+fn run_file(file: &str) -> ErrorHandler {
     let contents = fs::read_to_string(file).expect(&format!("Could not load {}", file));
     run(contents)
 }
 
 /// Main program. Either load a script from a file, or start the REPL.
-fn main() {
+fn main() -> Result<(), ExitCode> {
     let args: Vec<String> = env::args().skip(1).collect();
     let n_args = args.len();
     if n_args == 0 {
         run_prompt()
     } else if n_args == 1 {
-        run_file(&args[0]);
+        if run_file(&args[0]).had_error() {
+            return Err(ExitCode::from(65));
+        }
     } else {
         println!("Usage: slox [script]");
     }
+    Ok(())
 }