Err trait

src/lib.rs

@@ -9,8 +9,16 @@ use codespan_reporting::{
 };
 use lalrpop_util::{lexer::Token, ParseError};
 
-pub fn report_error<T>(
-    tree: Result<T, ParseError<usize, Token, &str>>,
+pub trait SpannedErr {
+    // TODO: Give these a default, so that &str can be used as default.
+    fn lo(&self) -> usize;
+    fn hi(&self) -> usize;
+    // TODO: Allow more controll
+    fn message(&self) -> String;
+}
+
+pub fn report_error<T, E: SpannedErr>(
+    tree: Result<T, ParseError<usize, Token, E>>,
     file_name: &str,
     file_contents: &str,
 ) -> anyhow::Result<T> {
@@ -39,7 +47,9 @@ pub fn report_error<T>(
                 ParseError::ExtraToken { token } => Diagnostic::error()
                     .with_message("Extra token")
                     .with_labels(vec![Label::primary(main_file_id, token.0..token.2)]),
-                ParseError::User { error } => bail!("User parse error: {}", error),
+                ParseError::User { error } => Diagnostic::error()
+                    .with_message(error.message())
+                    .with_labels(vec![Label::primary(main_file_id, error.lo()..error.hi())]),
             };
 
             emit_err(&err)?;