(debugger) in expression position not rejected at parse time

[Oichkatzelesfrettschen]

debugger is a Statement production, not an expression. Using it where an expression is required must be a parse-time SyntaxError. Boa accepts it and executes without error.

Repro:

(debugger);

Expected: SyntaxError at parse time
Got: executes silently

Spec: https://tc39.es/ecma262/#sec-debugger-statement

Failing test262: language/statements/debugger/expression.js

[jedel1043]

This was fixed in #4510.