From 632d4ab219715cd3a4bc012f4d4fa71f7a2deb31 Mon Sep 17 00:00:00 2001
From: Jonas Maier <jonas@x77.dev>
Date: Mon, 1 Jun 2026 20:50:42 +0200
Subject: syntax highlighting for variable interpolation and escape codes

---
 src/parse/mod.rs           | 39 +++++++++++++++++++++++++++++++++++++--
 src/syntax_highlighting.rs |  2 ++
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 4cba0fd..449df98 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -972,11 +972,13 @@ impl Parse for ExpString {
                     }
                 }
 
+                let begin = b.loc();
                 let x = b.adv();
 
                 if x == b'\\' && !delim.is_strict() {
                     if let Some(x) = parse_escape_code(b)? {
                         add_char(p, x);
+                        b.highlight_from(begin, OtherHighlights::Escapes);
                     }
                 } else if x == b'$' && !delim.is_strict() {
                     if !b.has() {
@@ -989,13 +991,17 @@ impl Parse for ExpString {
                     if is_var_begin(x) {
                         let v = VarName::parse(b)?;
                         p.push(StringPart::Var(Var::new(v)));
+                        b.highlight_from(begin, OtherHighlights::Variable);
                         continue;
                     }
 
                     b.adv();
 
                     match x {
-                        b'?' | b'!' => p.push(StringPart::Var(Var::new(VarName { name: vec![x] }))),
+                        b'?' | b'!' => {
+                            b.highlight_from(begin, OtherHighlights::Variable);
+                            p.push(StringPart::Var(Var::new(VarName { name: vec![x] })))
+                        }
                         b'{' => {
                             let v = VarName::parse(b)?;
                             let mut default = None;
@@ -1031,6 +1037,7 @@ impl Parse for ExpString {
                                 b.adv();
                             }
 
+                            b.highlight_from(begin, OtherHighlights::Variable);
                             p.push(StringPart::Var(Var {
                                 name: v,
                                 default,
@@ -1077,6 +1084,7 @@ impl Parse for ExpString {
                         default: None,
                         already_complete: true,
                     }));
+                    b.highlight_from(begin, OtherHighlights::Variable);
                 } else {
                     add_char(p, x);
                 }
@@ -1348,15 +1356,31 @@ pub enum HighlightKind {
     Other(OtherHighlights),
 }
 
+impl From<Keyword> for HighlightKind {
+    fn from(value: Keyword) -> Self {
+        Self::Keyword(value)
+    }
+}
+
+impl From<OtherHighlights> for HighlightKind {
+    fn from(value: OtherHighlights) -> Self {
+        Self::Other(value)
+    }
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Variants)]
 pub enum OtherHighlights {
     String,
+    Variable,
+    Escapes,
 }
 
 impl OtherHighlights {
     pub fn identifier(&self) -> &bstr {
         match self {
             OtherHighlights::String => b"string",
+            OtherHighlights::Variable => b"var",
+            OtherHighlights::Escapes => b"escape",
         }
     }
 }
@@ -1574,6 +1598,17 @@ impl<'a> Cursor<'a> {
         self.file.from(self.loc_u32())
     }
 
+    fn highlight_from(&mut self, from: span::SpanFrom, kind: impl Into<HighlightKind>) {
+        self.highlight(from.to(self.loc_u32()), kind)
+    }
+
+    fn highlight(&mut self, span: span::Span, kind: impl Into<HighlightKind>) {
+        self.highlights.push(Highlight {
+            span,
+            kind: kind.into(),
+        });
+    }
+
     fn spaces_stats(&mut self) -> SpaceStats {
         let mut stats = SpaceStats::default();
         while self.has() && b" \t\n\r".contains(&self.buf[0]) {
@@ -1623,7 +1658,7 @@ impl<'a> Cursor<'a> {
                     self.spaces();
                     Ok(())
                 } else {
-                    if self.is_completion() {
+                    if self.is_completion() && self.buf.len() == bytes.len() {
                         self.buf = &self.buf[bytes.len()..];
                         Ok(())
                     } else {
diff --git a/src/syntax_highlighting.rs b/src/syntax_highlighting.rs
index 19f44ab..22a8c3e 100644
--- a/src/syntax_highlighting.rs
+++ b/src/syntax_highlighting.rs
@@ -28,6 +28,8 @@ impl Highlighter {
         sc("keywords", GREEN_FG);
         sc("braces", CYAN_FG);
         sc("string", MAGENTA_FG);
+        sc("var", CYAN_FG);
+        sc("escape", RED_FG);
         this
     }
 
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