Refactor error reports

dust-lang/src/context.rs

@@ -61,9 +61,13 @@ impl Context {
         &self,
         identifier: &Identifier,
     ) -> Result<Option<(ContextData, usize)>, ContextError> {
-        let associations = self.associations.read()?;
-
-        Ok(associations.get(identifier).cloned())
+        if let Some((variable_data, position)) = self.associations.read()?.get(identifier) {
+            Ok(Some((variable_data.clone(), *position)))
+        } else if let Some(parent) = &self.parent {
+            parent.get(identifier)
+        } else {
+            Ok(None)
+        }
     }
 
     /// Returns the type associated with the given identifier.
@@ -268,11 +272,9 @@ impl Context {
         let mut associations = self.associations.write()?;
 
         if let Some((_, last_position)) = associations.get_mut(identifier) {
-            if position > *last_position {
             log::trace!("Updating {identifier}'s last position to {position:?}");
 
             *last_position = position;
-            }
 
             Ok(true)
         } else {

dust-lang/src/dust_error.rs

@@ -1,8 +1,8 @@
 //! Top-level error handling for the Dust language.
-use annotate_snippets::{Level, Renderer, Snippet};
+use annotate_snippets::{Level, Message, Renderer, Snippet};
 use std::fmt::Display;
 
-use crate::{Span, AnalysisError, ContextError, LexError, ParseError, RuntimeError};
+use crate::{AnalysisError, ContextError, LexError, ParseError, RuntimeError, Span};
 
 /// An error that occurred during the execution of the Dust language and its
 /// corresponding source code.
@@ -79,14 +79,26 @@ impl<'src> DustError<'src> {
         }
     }
 
-    pub fn error_data(&self) -> Vec<(&'static str, Span, String)> {
+    fn footer(&self) -> Vec<(&'static str, Span, String)> {
         match self {
             DustError::ContextError(_) => vec![],
-            DustError::Runtime { runtime_error, .. } => vec![(
+            DustError::Runtime { runtime_error, .. } => {
+                let mut error_data = vec![(
                     "Runtime error",
                     runtime_error.position(),
                     runtime_error.to_string(),
-            )],
+                )];
+
+                if let RuntimeError::Expression { error, position } = runtime_error {
+                    error_data.push((
+                        "Error occured at this expression",
+                        *position,
+                        error.to_string(),
+                    ));
+                }
+
+                error_data
+            }
             DustError::Analysis {
                 analysis_errors, ..
             } => analysis_errors
@@ -108,13 +120,43 @@ impl<'src> DustError<'src> {
         let mut report = String::new();
         let renderer = Renderer::styled();
 
-        for (title, span, label) in self.error_data() {
-            let message = Level::Error.title(title).snippet(
-                Snippet::source(self.source())
-                    .annotation(Level::Info.span(span.0..span.1).label(&label)),
+        match self {
+            DustError::ContextError(_) => {
+                let message = Level::Error.title("Context error");
+
+                report.push_str(&renderer.render(message).to_string());
+            }
+            DustError::Runtime {
+                runtime_error,
+                source,
+            } => {
+                let error = runtime_error.root_error();
+                let position = error.position();
+                let label = error.to_string();
+                let message = Level::Error
+                    .title("Runtime error")
+                    .snippet(
+                        Snippet::source(source)
+                            .fold(true)
+                            .annotation(Level::Error.span(position.0..position.1).label(&label)),
+                    )
+                    .footer(
+                        Level::Error
+                            .title("This error occured during the execution of the Dust program."),
                     );
 
-            report.push_str(&format!("{}", renderer.render(message)));
+                report.push_str(&renderer.render(message).to_string());
+                report.push('\n');
+            }
+            DustError::Analysis {
+                analysis_errors,
+                source,
+            } => todo!(),
+            DustError::Parse {
+                parse_error,
+                source,
+            } => todo!(),
+            DustError::Lex { lex_error, source } => todo!(),
         }
 
         report

dust-lang/src/vm.rs

@@ -1236,6 +1236,14 @@ impl RuntimeError {
             Self::UndefinedField { field_position, .. } => *field_position,
         }
     }
+
+    pub fn root_error(&self) -> &Self {
+        match self {
+            Self::Expression { error, .. } => error.root_error(),
+            Self::Statement { error, .. } => error.root_error(),
+            error => error,
+        }
+    }
 }
 
 impl From<ParseError> for RuntimeError {
@@ -1264,12 +1272,8 @@ impl Display for RuntimeError {
                 write!(f, "Function call error at {:?}: {}", position, error)
             }
             Self::ParseError(parse_error) => write!(f, "{}", parse_error),
-            Self::Expression { error, position } => {
-                write!(
-                    f,
-                    "Error while running expression at {:?}: {}",
-                    position, error
-                )
+            Self::Expression { .. } => {
+                write!(f, "Error while running expression")
             }
             Self::Statement { error, position } => {
                 write!(