Handle local.definition-value captures in queries

This lets you indicate, when matching a variable definition, that
another later syntax node represents the value of the variable definition,
and so any references to the same variable name within that value node
must be referring to some earlier definition.

highlight/src/lib.rs

@@ -46,6 +46,7 @@ pub struct HighlightConfiguration {
     injection_language_capture_index: Option<u32>,
     local_scope_capture_index: Option<u32>,
     local_def_capture_index: Option<u32>,
+    local_def_value_capture_index: Option<u32>,
     local_ref_capture_index: Option<u32>,
 }
 
@@ -84,11 +85,18 @@ pub struct HtmlRenderer {
     pub line_offsets: Vec<u32>,
 }
 
+#[derive(Debug)]
+struct LocalDef<'a> {
+    name: &'a str,
+    value_range: ops::Range<usize>,
+    highlight: Option<Highlight>,
+}
+
 #[derive(Debug)]
 struct LocalScope<'a> {
     inherits: bool,
     range: ops::Range<usize>,
-    local_defs: Vec<(&'a str, Option<Highlight>)>,
+    local_defs: Vec<LocalDef<'a>>,
 }
 
 struct HighlightIter<'a, F>
@@ -237,6 +245,7 @@ impl Highlighter {
         let mut injection_language_capture_index = None;
         let mut injection_site_capture_index = None;
         let mut local_def_capture_index = None;
+        let mut local_def_value_capture_index = None;
         let mut local_ref_capture_index = None;
         let mut local_scope_capture_index = None;
         for (i, name) in query.capture_names().iter().enumerate() {
@@ -246,6 +255,7 @@ impl Highlighter {
                 "injection.language" => injection_language_capture_index = i,
                 "injection.site" => injection_site_capture_index = i,
                 "local.definition" => local_def_capture_index = i,
+                "local.definition-value" => local_def_value_capture_index = i,
                 "local.reference" => local_ref_capture_index = i,
                 "local.scope" => local_scope_capture_index = i,
                 _ => {}
@@ -264,6 +274,7 @@ impl Highlighter {
             injection_language_capture_index,
             injection_site_capture_index,
             local_def_capture_index,
+            local_def_value_capture_index,
             local_ref_capture_index,
             local_scope_capture_index,
         })
@@ -573,13 +584,15 @@ where
             // Get the next capture. If there are no more captures, then emit the rest of the
             // source code.
             let match_;
+            let mut captures;
             let mut capture;
             let mut pattern_index;
             let layer = &mut self.layers[0];
             if let Some((m, capture_index)) = layer.captures.peek() {
                 match_ = m;
+                captures = match_.captures;
                 pattern_index = match_.pattern_index;
-                capture = match_.captures[*capture_index];
+                capture = captures[*capture_index];
             } else if let Some(end_byte) = layer.highlight_end_stack.last().cloned() {
                 layer.highlight_end_stack.pop();
                 return self.emit_event(end_byte, Some(HighlightEvent::HighlightEnd));
@@ -754,9 +767,22 @@ where
                     reference_highlight = None;
                     definition_highlight = None;
                     let scope = layer.scope_stack.last_mut().unwrap();
+
+                    let mut value_range = 0..0;
+                    for capture in captures {
+                        if Some(capture.index) == layer.config.local_def_value_capture_index {
+                            value_range = capture.node.byte_range();
+                        }
+                    }
+
                     if let Ok(name) = str::from_utf8(&self.source[range.clone()]) {
-                        scope.local_defs.push((name, None));
-                        definition_highlight = scope.local_defs.last_mut().map(|s| &mut s.1);
+                        scope.local_defs.push(LocalDef {
+                            name,
+                            value_range,
+                            highlight: None,
+                        });
+                        definition_highlight =
+                            scope.local_defs.last_mut().map(|s| &mut s.highlight);
                     }
                 }
                 // If the node represents a reference, then try to find the corresponding
@@ -767,9 +793,9 @@ where
                         if let Ok(name) = str::from_utf8(&self.source[range.clone()]) {
                             for scope in layer.scope_stack.iter().rev() {
                                 if let Some(highlight) =
-                                    scope.local_defs.iter().rev().find_map(|i| {
-                                        if i.0 == name {
-                                            Some(i.1)
+                                    scope.local_defs.iter().rev().find_map(|def| {
+                                        if def.name == name && range.start >= def.value_range.end {
+                                            Some(def.highlight)
                                         } else {
                                             None
                                         }
@@ -792,6 +818,7 @@ where
                     let next_capture = next_match.captures[*next_capture_index];
                     if next_capture.node == capture.node {
                         pattern_index = next_match.pattern_index;
+                        captures = next_match.captures;
                         capture = next_capture;
                         layer.captures.next();
                         continue;