Fix range used for flow merging in Expr::If

Summary: We need to use a range that isn't used by anything else that calls merge_flow.

Reviewed By: migeed-z

Differential Revision: D68248102

fbshipit-source-id: ac498767c888ab563eb7bfc81b182069e6df79ab

pyre2/pyre2/bin/binding/bindings.rs

@@ -652,7 +652,7 @@ impl<'a> BindingsBuilder<'a> {
                 let narrow_ops = NarrowOps::from_expr(Some((*x.test).clone()));
                 self.bind_narrow_ops(&narrow_ops, x.body.range());
                 self.ensure_expr(&x.body);
-                self.negate_and_merge_flow(base, &narrow_ops, Some(&x.orelse), x.orelse.range());
+                self.negate_and_merge_flow(base, &narrow_ops, Some(&x.orelse), x.range());
                 return;
             }
             Expr::BoolOp(ExprBoolOp { range, op, values }) => {

pyre2/pyre2/bin/test/flow.rs

@@ -858,3 +858,12 @@ def f(x: None):
         pass
     "#,
 );
+
+// Regression test for a crash
+testcase!(
+    test_ternary_and_or,
+    r#"
+def f(x: bool, y: int):
+    return 0 if x else (y or 1)
+    "#,
+);