1 files changed, 59 insertions, 0 deletions
diff --git a/src/chomp/check/spanning.rs b/src/chomp/check/spanning.rs
new file mode 100644
index 0000000..91e593b
--- /dev/null
+++ b/src/chomp/check/spanning.rs
@@ -0,0 +1,59 @@
+use proc_macro2::{Ident, Span};
+
+use super::super::{
+    ast::{Alt, Call, Cat, Epsilon, Fix, Literal, Parameter, Variable},
+    visit::{Visitable, Visitor},
+};
+
+#[derive(Clone, Copy, Debug)]
+pub struct Spanning;
+
+impl Visitor for Spanning {
+    type Out = Option<Span>;
+
+    fn visit_epsilon(&mut self, eps: &Epsilon) -> Self::Out {
+        eps.map(|e| e.span)
+    }
+
+    fn visit_literal(&mut self, lit: &Literal) -> Self::Out {
+        lit.span()
+    }
+
+    fn visit_cat(&mut self, cat: &Cat) -> Self::Out {
+        let fst = cat.first().visit(self);
+        let snd = cat.second().visit(self);
+
+        match (fst, snd) {
+            (None, snd) => snd,
+            (Some(fst), None) => Some(fst),
+            (Some(fst), Some(snd)) => fst.join(snd),
+        }
+    }
+
+    fn visit_alt(&mut self, alt: &Alt) -> Self::Out {
+        let left = alt.left().visit(self);
+        let right = alt.right().visit(self);
+
+        match (left, right) {
+            (None, right) => right,
+            (Some(left), None) => Some(left),
+            (Some(left), Some(right)) => left.join(right),
+        }
+    }
+
+    fn visit_fix(&mut self, fix: &Fix) -> Self::Out {
+        fix.span()
+    }
+
+    fn visit_variable(&mut self, var: &Variable) -> Self::Out {
+        var.name().span()
+    }
+
+    fn visit_parameter(&mut self, param: &Parameter) -> Self::Out {
+        param.name().span()
+    }
+
+    fn visit_call(&mut self, call: &Call) -> Self::Out {
+        call.span()
+    }
+}