[fine] Bindings in if remain in scope!

fine/src/semantics.rs

@@ -433,6 +433,34 @@ fn set_logical_parents(
                 set_logical_parents(parents, syntax_tree, rhs, Some(t));
             }
         }
+        TreeKind::ConditionalExpression => {
+            // Special case! If the condition expression is a `is` expression
+            // then it is the parent for the body of the `then` clause so
+            // that any variable bindings it makes remain in scope. The
+            // `else` clause and the condition itself do not have the
+            // bindings in scope, obviously.
+            let body_parent = if let Some(is_condition) =
+                tree.child_of_kind(syntax_tree, TreeKind::IsExpression)
+            {
+                Some(is_condition)
+            } else {
+                Some(t)
+            };
+
+            let then_body = tree.nth_tree(2);
+            for child in &tree.children {
+                match child {
+                    Child::Token(_) => (),
+                    Child::Tree(ct) => {
+                        if Some(*ct) == then_body {
+                            set_logical_parents(parents, syntax_tree, *ct, body_parent);
+                        } else {
+                            set_logical_parents(parents, syntax_tree, *ct, Some(t));
+                        }
+                    }
+                }
+            }
+        }
         _ => {
             // By default, the parent for each child is current tree.
             for child in &tree.children {