Fix pattern field completions not working for unions

crates/ide-completion/src/context.rs

@@ -134,6 +134,7 @@ pub(crate) struct ExprCtx {
     pub(crate) in_condition: bool,
     pub(crate) incomplete_let: bool,
     pub(crate) ref_expr_parent: Option<ast::RefExpr>,
+    /// The surrounding RecordExpression we are completing a functional update
     pub(crate) is_func_update: Option<ast::RecordExpr>,
     pub(crate) self_param: Option<hir::SelfParam>,
     pub(crate) innermost_ret_ty: Option<hir::Type>,