🎨 Overhaul syntax highlighting colors and add parser-based function detection

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: timfennis

Cargo.lock

@@ -15,6 +15,7 @@ itertools.workspace = true
 strsim.workspace = true
 codespan-reporting = "0.11.1"
 ndc_lexer.workspace = true
+ndc_parser.workspace = true
 ndc_interpreter.workspace = true
 ndc_stdlib.workspace = true
 ndc_core.workspace = true

ndc_bin/Cargo.toml

@@ -1,11 +1,35 @@
 use itertools::Itertools;
-use ndc_lexer::{Lexer, Token};
+use ndc_lexer::{Lexer, Token, TokenLocation};
+use ndc_parser::{Expression, ExpressionLocation, ForBody, ForIteration};
+use std::collections::HashSet;
 use yansi::{Paint, Painted};
 
 pub(crate) struct AndycppHighlighter;
 
 impl AndycppHighlighter {
-    pub fn highlight_line(line: &str) -> Vec<Painted<&str>> {
+    /// Parser-enhanced highlighting that correctly identifies function names
+    /// even in method-call syntax like `foo.len`.
+    pub fn highlight_parsed(line: &str) -> Vec<Painted<&str>> {
+        let mut function_spans = HashSet::new();
+
+        let expressions = Lexer::new(line)
+            .collect::<Result<Vec<TokenLocation>, _>>()
+            .ok()
+            .and_then(|tokens| ndc_parser::Parser::from_tokens(tokens).parse().ok());
+
+        if let Some(expressions) = expressions {
+            for expr in &expressions {
+                collect_function_spans(expr, &mut function_spans);
+            }
+        }
+
+        Self::highlight_tokens(line, &function_spans)
+    }
+
+    fn highlight_tokens<'a>(
+        line: &'a str,
+        function_spans: &HashSet<usize>,
+    ) -> Vec<Painted<&'a str>> {
         let Ok(tokens) = Lexer::new(line).collect::<Result<Vec<_>, _>>() else {
             return vec![line.red()];
         };
@@ -22,26 +46,67 @@ impl AndycppHighlighter {
         }
 
         let mut out = Vec::new();
-        for (range, token) in ranges.into_iter().zip(tokens.into_iter()) {
+        let pairs: Vec<_> = ranges.into_iter().zip(tokens).collect();
+        for (i, (range, token)) in pairs.iter().enumerate() {
             let substring = &line[range.start..(range.start + range.len())];
+            let next_token = pairs.get(i + 1).map(|(_, t)| &t.token);
 
             let colored = match &token.token {
-                Token::String(_) => substring.rgb(70, 200, 128),
+                // Strings — green
+                Token::String(_) => substring.rgb(152, 195, 121),
+                // Numeric literals and booleans — orange
                 Token::BigInt(_)
                 | Token::Int64(_)
                 | Token::Float64(_)
                 | Token::Complex(_)
+                | Token::Infinity
                 | Token::True
-                | Token::False => substring.rgb(253, 151, 31),
+                | Token::False => substring.rgb(209, 154, 102),
+                // Keywords — coral red
+                Token::Let
+                | Token::Fn
+                | Token::If
+                | Token::Else
+                | Token::Return
+                | Token::Break
+                | Token::Continue
+                | Token::For
+                | Token::In
+                | Token::While
+                | Token::Pure
+                | Token::LogicAnd
+                | Token::LogicOr
+                | Token::LogicNot => substring.rgb(224, 108, 117),
+                // Function identifiers — yellow/gold
+                // Detected by parser (dot-calls, etc.) or by token heuristics as fallback
+                Token::Identifier(_) if function_spans.contains(&token.span.offset()) => {
+                    substring.rgb(229, 192, 123)
+                }
+                Token::Identifier(_) if matches!(next_token, Some(Token::LeftParentheses)) => {
+                    substring.rgb(229, 192, 123)
+                }
+                Token::Identifier(_) if i > 0 && matches!(pairs[i - 1].1.token, Token::Fn) => {
+                    substring.rgb(229, 192, 123)
+                }
+                // Variable identifiers — blue
+                Token::Identifier(_) => substring.rgb(97, 175, 239),
+                // Arrows, fat arrows, and assignment — cyan
+                Token::RightArrow | Token::FatArrow | Token::EqualsSign | Token::OpAssign(_) => {
+                    substring.rgb(86, 182, 194)
+                }
+                // Brackets and delimiters — light gray (neutral)
                 Token::LeftSquareBracket
                 | Token::RightSquareBracket
                 | Token::LeftCurlyBracket
                 | Token::RightCurlyBracket
                 | Token::LeftParentheses
                 | Token::RightParentheses
-                | Token::MapOpen => substring.rgb(229, 181, 103),
-                Token::Identifier(_) => substring.rgb(51, 177, 255),
-                _ => substring.rgb(140, 182, 255).bold(),
+                | Token::MapOpen
+                | Token::Semicolon
+                | Token::Comma
+                | Token::Colon => substring.rgb(171, 178, 191),
+                // Operators — purple
+                _ => substring.rgb(198, 120, 221),
             };
 
             out.push(colored);
@@ -50,3 +115,107 @@ impl AndycppHighlighter {
         out
     }
 }
+
+/// Walk the parsed AST and collect the byte offsets of identifiers used as function names.
+fn collect_function_spans(expr: &ExpressionLocation, spans: &mut HashSet<usize>) {
+    match &expr.expression {
+        Expression::Call {
+            function,
+            arguments,
+        } => {
+            if let Expression::Identifier { .. } = &function.expression {
+                spans.insert(function.span.offset());
+            }
+            collect_function_spans(function, spans);
+            for arg in arguments {
+                collect_function_spans(arg, spans);
+            }
+        }
+        Expression::FunctionDeclaration { body, .. } => {
+            collect_function_spans(body, spans);
+        }
+        Expression::VariableDeclaration { value, .. }
+        | Expression::Assignment { r_value: value, .. }
+        | Expression::OpAssignment { r_value: value, .. }
+        | Expression::Return { value } => {
+            collect_function_spans(value, spans);
+        }
+        Expression::Statement(inner) | Expression::Grouping(inner) => {
+            collect_function_spans(inner, spans);
+        }
+        Expression::Block { statements } => {
+            for s in statements {
+                collect_function_spans(s, spans);
+            }
+        }
+        Expression::If {
+            condition,
+            on_true,
+            on_false,
+        } => {
+            collect_function_spans(condition, spans);
+            collect_function_spans(on_true, spans);
+            if let Some(f) = on_false {
+                collect_function_spans(f, spans);
+            }
+        }
+        Expression::While {
+            expression,
+            loop_body,
+        } => {
+            collect_function_spans(expression, spans);
+            collect_function_spans(loop_body, spans);
+        }
+        Expression::For { iterations, body } => {
+            for iteration in iterations {
+                match iteration {
+                    ForIteration::Iteration { sequence, .. } => {
+                        collect_function_spans(sequence, spans);
+                    }
+                    ForIteration::Guard(expr) => collect_function_spans(expr, spans),
+                }
+            }
+            match body.as_ref() {
+                ForBody::Block(e) | ForBody::List { expr: e, .. } => {
+                    collect_function_spans(e, spans);
+                }
+                ForBody::Map {
+                    key,
+                    value,
+                    default,
+                    ..
+                } => {
+                    collect_function_spans(key, spans);
+                    if let Some(v) = value {
+                        collect_function_spans(v, spans);
+                    }
+                    if let Some(d) = default {
+                        collect_function_spans(d, spans);
+                    }
+                }
+            }
+        }
+        Expression::Logical { left, right, .. } => {
+            collect_function_spans(left, spans);
+            collect_function_spans(right, spans);
+        }
+        Expression::Tuple { values } | Expression::List { values } => {
+            for v in values {
+                collect_function_spans(v, spans);
+            }
+        }
+        Expression::Map { values, default } => {
+            for (k, v) in values {
+                collect_function_spans(k, spans);
+                if let Some(v) = v {
+                    collect_function_spans(v, spans);
+                }
+            }
+            if let Some(d) = default {
+                collect_function_spans(d, spans);
+            }
+        }
+        // Literals, identifiers (non-call), etc. — nothing to collect
+        _ => {}
+    }
+}

ndc_bin/src/highlighter.rs

@@ -143,7 +143,7 @@ fn main() -> anyhow::Result<()> {
         Action::HighlightFile(path) => {
             let string = fs::read_to_string(path)?;
 
-            let out = AndycppHighlighter::highlight_line(&string);
+            let out = AndycppHighlighter::highlight_parsed(&string);
             for styled in out {
                 print!("{}", styled);
             }

ndc_bin/src/main.rs

@@ -15,7 +15,7 @@ struct RustylineHelper {}
 
 impl rustyline::highlight::Highlighter for RustylineHelper {
     fn highlight<'l>(&self, line: &'l str, _pos: usize) -> Cow<'l, str> {
-        let out = AndycppHighlighter::highlight_line(line);
+        let out = AndycppHighlighter::highlight_parsed(line);
 
         Cow::Owned(out.into_iter().join(""))
     }