cl-ast: Move loop expression into unary exprs (with lowest priority)

compiler/cl-ast/src/desugar/while_else.rs

@@ -26,8 +26,8 @@ fn desugar_while(extents: Span, kind: ExprKind) -> ExprKind {
             let break_expr = Expr { extents: fail_span, kind: ExprKind::Break(Break { body }) };
 
             let loop_body = If { cond, pass, fail: Else { body: Some(Box::new(break_expr)) } };
-            let loop_body = Expr { extents, kind: ExprKind::If(loop_body) };
-            ExprKind::Loop(Loop { body: Box::new(loop_body) })
+            let loop_body = ExprKind::If(loop_body);
+            ExprKind::Unary(Unary { kind: UnaryKind::Loop, tail: Box::new(loop_body) })
         }
         _ => kind,
     }