The scope name for the { at open, or null when the brace is a value.
Two shapes qualify: <name>={ with name in the closed set (or head-scoped
under the right leading directive), and a brace body directly following a
body-taking directive (:do {, :retry {, :onerror Err {).
The scope name for the
{atopen, or null when the brace is a value. Two shapes qualify:<name>={with name in the closed set (or head-scoped under the right leading directive), and a brace body directly following a body-taking directive (:do {,:retry {,:onerror Err {).