`debugger` is a statement, not an expression

[hpp2334]

Describe the bug
debugger is a statement, not an expression.

To Reproduce

Case	Actual	Expected (Test on firefox)
!debugger	true	Uncaught SyntaxError: expected expression, got keyword 'debugger'
let x = debugger;	undefined	Uncaught SyntaxError: expected expression, got keyword 'debugger'
debugger + debugger	NaN	Uncaught SyntaxError: unexpected token: '+'

Build environment

Run in playground