Colourize examples in error output (#64)

Since we went to all the trouble of having fancy ANSI colour when
formatting code and printing to a terminal (something that Technique v0
did very nicely and we finally caught up with in #61), there's no reason
we couldn't use the same styles when rendering help text and examples in
compiler error messages.

This ended up extending into a fairly broad refactoring, moving the
formatting and display of error messages out of the library crate and
into the application layer, renaming a number of (internal) traits and
their methods.

Considerable revision of the examples in the errors also accompanied
this change.

Author: istathar

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "technique"
-version = "0.3.4"
+version = "0.3.5"
 edition = "2021"
 description = "A domain specific language for procedures."
 authors = [ "Andrew Cowie" ]

Cargo.toml

@@ -912,6 +912,7 @@ impl Formatter {
     }
 }
 
+
 impl ToString for Formatter {
     fn to_string(&self) -> String {
         let mut result = String::new();

src/error/display.rs

@@ -35,15 +35,15 @@ pub enum Syntax {
 /// Trait for different rendering backends (the no-op no-markup one, ANSI
 /// escapes for terminal colouring, Typst markup for documents)
 pub trait Render {
-    /// Render content with the specified type/style
-    fn render(&self, content_type: Syntax, content: &str) -> String;
+    /// Apply styling to content with the specified syntax type
+    fn style(&self, content_type: Syntax, content: &str) -> String;
 }
 
 /// Returns content unchanged, with no markup applied
 pub struct Identity;
 
 impl Render for Identity {
-    fn render(&self, _syntax: Syntax, content: &str) -> String {
+    fn style(&self, _syntax: Syntax, content: &str) -> String {
         content.to_string()
     }
 }
@@ -68,12 +68,12 @@ fn format_to_fragments(technique: &Document, width: u8) -> Vec<(Syntax, String)>
     crate::formatting::formatter::format_with_renderer(technique, width)
 }
 
-/// Pass 2: apply markup to fragments via render() and combine.
+/// Pass 2: apply markup to fragments via style() and combine.
 fn render_to_string(renderer: &impl Render, fragments: Vec<(Syntax, String)>) -> String {
     let mut output = String::new();
 
     for (syntax, content) in fragments {
-        let rendered = renderer.render(syntax, &content);
+        let rendered = renderer.style(syntax, &content);
         output.push_str(&rendered);
     }
 

src/error/mod.rs

@@ -0,0 +1,15 @@
+use std::{fmt, path::Path};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct LoadingError<'i> {
+    pub problem: String,
+    pub details: String,
+    pub filename: &'i Path,
+}
+
+
+impl<'i> fmt::Display for LoadingError<'i> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}: {}", self.problem, self.details)
+    }
+}

src/formatting/formatter.rs

@@ -1,8 +1,10 @@
 // Types representing the Technique procedures language
 
+mod error;
 mod quantity;
 mod types;
 
 // Re-export all public symbols
+pub use error::*;
 pub use quantity::*;
 pub use types::*;

src/formatting/renderer.rs

@@ -166,26 +166,6 @@ pub fn convert_superscript(input: &str) -> String {
         .collect()
 }
 
-fn to_superscript(num: i8) -> String {
-    num.to_string()
-        .chars()
-        .map(|c| match c {
-            '0' => '⁰',
-            '1' => '¹',
-            '2' => '²',
-            '3' => '³',
-            '4' => '⁴',
-            '5' => '⁵',
-            '6' => '⁶',
-            '7' => '⁷',
-            '8' => '⁸',
-            '9' => '⁹',
-            '-' => '⁻',
-            _ => c,
-        })
-        .collect()
-}
-
 impl Display for Decimal {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         if self.precision == 0 {
@@ -230,8 +210,28 @@ impl<'i> Display for Quantity<'i> {
     }
 }
 
+fn to_superscript(num: i8) -> String {
+    num.to_string()
+        .chars()
+        .map(|c| match c {
+            '0' => '⁰',
+            '1' => '¹',
+            '2' => '²',
+            '3' => '³',
+            '4' => '⁴',
+            '5' => '⁵',
+            '6' => '⁶',
+            '7' => '⁷',
+            '8' => '⁸',
+            '9' => '⁹',
+            '-' => '⁻',
+            _ => c,
+        })
+        .collect()
+}
+
 #[cfg(test)]
-mod tests {
+mod check {
     use super::*;
 
     #[test]

src/language/error.rs

@@ -1,5 +1,4 @@
-pub mod error;
+pub mod formatting;
 pub mod language;
 pub mod parsing;
 pub mod regex;
-pub mod formatting;