From f00b9e22e75bb0a4812a6adade8df5a5537df0f2 Mon Sep 17 00:00:00 2001
From: John Doty <john@d0ty.me>
Date: Sat, 3 Feb 2024 09:54:46 -0800
Subject: [PATCH] [fine] Bindings in if remain in scope!

---
 fine/src/semantics.rs         | 28 ++++++++++++++++++++++++++++
 fine/tests/expression/is.fine |  9 ++++++---
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/fine/src/semantics.rs b/fine/src/semantics.rs
index 2722463d..0c3e726f 100644
--- a/fine/src/semantics.rs
+++ b/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 {
diff --git a/fine/tests/expression/is.fine b/fine/tests/expression/is.fine
index 7003ab47..ade0ecd6 100644
--- a/fine/tests/expression/is.fine
+++ b/fine/tests/expression/is.fine
@@ -3,17 +3,20 @@ class Foo {
 }
 
 fun test() -> f64 {
-  let b = new Foo { a : 23 };
+  let b = new Foo { a : 1000 };
 
   let result = 0;
-  if b is c:Foo and c.a == 23 {
+  if b is c:Foo and c.a == 1000 {
     result = result + 1;
   }
   if b is c:Foo and c.a == 24 {
     result = result + 10;
   }
+  if b is c:Foo {
+    result = result + c.a; // c should still be in scope!
+  }
   result
 }
 
 // @no-errors
-// @eval: Float(1.0)
\ No newline at end of file
+// @eval: Float(1001.0)
\ No newline at end of file