Early errors for CaseBlock with a default clause are not defined

[nanto]

[JP22] In 13.12.1, early errors for CaseBlock : { CaseClauses } are defined but those for CaseBlock : { CaseClauses_opt DefaultClause CaseClauses_opt } are not. To cover CaseBlock with a default clause, it can be:

SwitchStatement : switch ( Expression ) CaseBlock

• It is a Syntax Error if the LexicallyDeclaredNames of CaseBlock contains any duplicate entries.
• It is a Syntax Error if any element of the LexicallyDeclaredNames of CaseBlock also occurs in the VarDeclaredNames of CaseBlock.