Most base expressions work.

src/syntax/location.rs

@@ -0,0 +1,48 @@
+use codespan_reporting::diagnostic::Label;
+use std::cmp::{max, min};
+use std::ops::Range;
+
+pub trait Located {
+    fn location(&self) -> Location;
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Location {
+    file_id: usize,
+    span: Range<usize>,
+}
+
+impl Location {
+    pub fn new(file_id: usize, span: Range<usize>) -> Self {
+        Location { file_id, span }
+    }
+
+    pub fn extend_to(&self, other: &Location) -> Location {
+        assert_eq!(self.file_id, other.file_id);
+        Location {
+            file_id: self.file_id,
+            span: min(self.span.start, other.span.start)..max(self.span.end, other.span.end),
+        }
+    }
+
+    pub fn merge_span(mut self, span: Range<usize>) -> Location {
+        self.span = min(self.span.start, span.start)..max(self.span.end, span.end);
+        self
+    }
+
+    pub fn file_id(&self) -> usize {
+        self.file_id
+    }
+
+    pub fn span(&self) -> Range<usize> {
+        self.span.clone()
+    }
+
+    pub fn primary_label(&self) -> Label<usize> {
+        Label::primary(self.file_id, self.span.clone())
+    }
+
+    pub fn secondary_label(&self) -> Label<usize> {
+        Label::secondary(self.file_id, self.span.clone())
+    }
+}