Yeast: use child locations instead of rule target

Previously, when a node was synthesized it would always take the
location from the node that matched the current rule. This resulted
in overly broad locations however.

For (foo #{bar}) we now take the location of the 'bar' node.

For non-leaf nodes we merge all its child node locations.

shared/yeast-macros/src/parse.rs

@@ -396,8 +396,10 @@ fn parse_direct_node_inner(tokens: &mut Tokens, ctx: &Ident) -> Result<TokenStre
         let expr = group.stream();
         return Ok(quote! {
             {
-                let __value = yeast::YeastDisplay::yeast_to_string(&(#expr), &*#ctx.ast);
-                #ctx.literal(#kind_str, &__value)
+                let __expr = (#expr);
+                let __value = yeast::YeastDisplay::yeast_to_string(&__expr, &*#ctx.ast);
+                let __source_range = yeast::YeastSourceRange::yeast_source_range(&__expr, &*#ctx.ast);
+                #ctx.literal_with_source_range(#kind_str, &__value, __source_range)
             }
         });
     }

shared/yeast/src/build.rs

@@ -82,6 +82,21 @@ impl<'a> BuildCtx<'a> {
             .create_named_token_with_range(kind, value.to_string(), self.source_range)
     }
 
+    /// Create a leaf node with fixed content and an optional preferred source range.
+    /// If `source_range` is `None`, falls back to this context's inherited range.
+    pub fn literal_with_source_range(
+        &mut self,
+        kind: &'static str,
+        value: &str,
+        source_range: Option<tree_sitter::Range>,
+    ) -> Id {
+        self.ast.create_named_token_with_range(
+            kind,
+            value.to_string(),
+            source_range.or(self.source_range),
+        )
+    }
+
     /// Create a leaf node with an auto-generated unique name.
     pub fn fresh(&mut self, kind: &'static str, name: &str) -> Id {
         let generated = self.fresh.resolve(name);

shared/yeast/src/lib.rs

@@ -58,12 +58,30 @@ pub trait YeastDisplay {
     fn yeast_to_string(&self, ast: &Ast) -> String;
 }
 
+/// Optional source range for values used in `#{expr}` interpolations.
+///
+/// By default this returns `None`, so synthesized leaves inherit the matched
+/// rule's source range. `NodeRef` returns the referenced node's range, letting
+/// `(kind #{capture})` carry the captured node's location.
+pub trait YeastSourceRange {
+    fn yeast_source_range(&self, ast: &Ast) -> Option<tree_sitter::Range>;
+}
+
 impl YeastDisplay for NodeRef {
     fn yeast_to_string(&self, ast: &Ast) -> String {
         ast.source_text(self.0)
     }
 }
 
+impl YeastSourceRange for NodeRef {
+    fn yeast_source_range(&self, ast: &Ast) -> Option<tree_sitter::Range> {
+        ast.get_node(self.0).and_then(|n| match &n.content {
+            NodeContent::Range(r) => Some(r.clone()),
+            _ => n.source_range,
+        })
+    }
+}
+
 macro_rules! impl_yeast_display_via_display {
     ($($t:ty),* $(,)?) => {
         $(
@@ -72,6 +90,12 @@ macro_rules! impl_yeast_display_via_display {
                     ::std::string::ToString::to_string(self)
                 }
             }
+
+            impl YeastSourceRange for $t {
+                fn yeast_source_range(&self, _ast: &Ast) -> Option<tree_sitter::Range> {
+                    None
+                }
+            }
         )*
     };
 }
@@ -90,6 +114,12 @@ impl<T: YeastDisplay + ?Sized> YeastDisplay for &T {
     }
 }
 
+impl<T: YeastSourceRange + ?Sized> YeastSourceRange for &T {
+    fn yeast_source_range(&self, ast: &Ast) -> Option<tree_sitter::Range> {
+        (**self).yeast_source_range(ast)
+    }
+}
+
 pub const CHILD_FIELD: u16 = u16::MAX;
 
 #[derive(Debug)]
@@ -368,6 +398,15 @@ impl Ast {
         is_named: bool,
         source_range: Option<tree_sitter::Range>,
     ) -> Id {
+        let source_range = match &content {
+            // Parsed nodes already carry an exact source range in their content.
+            NodeContent::Range(_) => source_range,
+            // Synthesized nodes derive location from children when possible,
+            // and fall back to the inherited rule-match range otherwise.
+            _ => self
+                .union_source_range_of_children(&fields)
+                .or(source_range),
+        };
         let id = self.nodes.len();
         self.nodes.push(Node {
             kind,
@@ -383,6 +422,66 @@ impl Ast {
         id
     }
 
+    fn union_source_range_of_children(
+        &self,
+        fields: &BTreeMap<FieldId, Vec<Id>>,
+    ) -> Option<tree_sitter::Range> {
+        let mut start_byte: Option<usize> = None;
+        let mut end_byte: Option<usize> = None;
+        let mut start_point = tree_sitter::Point { row: 0, column: 0 };
+        let mut end_point = tree_sitter::Point { row: 0, column: 0 };
+
+        for child_ids in fields.values() {
+            for &child_id in child_ids {
+                let Some(child) = self.get_node(child_id) else {
+                    continue;
+                };
+
+                let child_start_byte = child.start_byte();
+                let child_end_byte = child.end_byte();
+
+                // Skip children that carry no usable location.
+                if child_start_byte == 0 && child_end_byte == 0 {
+                    continue;
+                }
+
+                match start_byte {
+                    None => {
+                        start_byte = Some(child_start_byte);
+                        start_point = child.start_position();
+                    }
+                    Some(current_start) if child_start_byte < current_start => {
+                        start_byte = Some(child_start_byte);
+                        start_point = child.start_position();
+                    }
+                    _ => {}
+                }
+
+                match end_byte {
+                    None => {
+                        end_byte = Some(child_end_byte);
+                        end_point = child.end_position();
+                    }
+                    Some(current_end) if child_end_byte > current_end => {
+                        end_byte = Some(child_end_byte);
+                        end_point = child.end_position();
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        match (start_byte, end_byte) {
+            (Some(start_byte), Some(end_byte)) => Some(tree_sitter::Range {
+                start_byte,
+                end_byte,
+                start_point,
+                end_point,
+            }),
+            _ => None,
+        }
+    }
+
     pub fn create_named_token(&mut self, kind: &'static str, content: String) -> Id {
         self.create_named_token_with_range(kind, content, None)
     }

shared/yeast/tests/test.rs

@@ -18,6 +18,16 @@ fn run_and_dump(input: &str, rules: Vec<Rule>) -> String {
     run_phased_and_dump(input, vec![Phase::new("test", PhaseKind::Repeating, rules)])
 }
 
+/// Helper: parse Ruby source with custom rules and return the transformed AST.
+fn run_and_ast(input: &str, rules: Vec<Rule>) -> Ast {
+    let lang: tree_sitter::Language = tree_sitter_ruby::LANGUAGE.into();
+    let schema =
+        yeast::node_types_yaml::schema_from_yaml_with_language(OUTPUT_SCHEMA_YAML, &lang).unwrap();
+    let phases = vec![Phase::new("test", PhaseKind::Repeating, rules)];
+    let runner = Runner::with_schema(lang, &schema, &phases);
+    runner.run(input).unwrap()
+}
+
 /// Helper: parse Ruby source with a custom output schema and multiple
 /// rule phases, return dump.
 fn run_phased_and_dump(input: &str, phases: Vec<Phase>) -> String {
@@ -1172,3 +1182,37 @@ fn test_hash_brace_renders_integer_expression() {
     "#,
     );
 }
+
+/// Regression test: `(kind #{capture})` should inherit the captured node's
+/// source location, not the full source range of the matched rule root.
+#[test]
+fn test_hash_brace_uses_capture_location_for_leaf() {
+    let rule = rule!(
+        (call
+            method: (identifier) @name
+            receiver: (identifier) @recv
+        )
+        =>
+        (call
+            method: (identifier #{name})
+            receiver: (identifier #{recv})
+            arguments: (argument_list)
+        )
+    );
+
+    let ast = run_and_ast("foo.bar()", vec![rule]);
+
+    let mut bar_ids: Vec<usize> = Vec::new();
+    for id in ast.reachable_node_ids() {
+        let Some(node) = ast.get_node(id) else { continue; };
+        if node.kind() == "identifier" && ast.source_text(id) == "bar" {
+            bar_ids.push(id);
+        }
+    }
+
+    assert_eq!(bar_ids.len(), 1, "expected exactly one identifier 'bar'");
+    let bar = ast.get_node(bar_ids[0]).unwrap();
+
+    assert_eq!(bar.start_byte(), 4);
+    assert_eq!(bar.end_byte(), 7);
+}