Render prefix ~ operator with a space

[LucaCappelletti94]

Fuzz round-trip found SELECT ~ -1 rendering as SELECT ~-1, which PostgreSQL retokenizes as the single ~- custom operator and fails to re-parse. SELECT ~ ~1 renders SELECT ~~1 and fails in every dialect, ~ @2 renders ~@2 and ~ #x renders ~# x in PostgreSQL.

Expr::UnaryOp display concatenates operator and operand in its final arm. BitwiseNot joins the spaced arm beside Not and Hash, the same remedy #2531 applies to @. Canonical output for SELECT ~expr becomes SELECT ~ expr, pinned with one_statement_parses_to in parse_generic_unary_ops.

[alamb]

Thanks @LucaCappelletti94

[alamb]

As a stylistic suggestion here to avoid issues in the future, I suggest changing the structure of this code to a sigle match so we can explicitly see which operators are handled in what form

like

match op {
  UnaryOperator::PGPostfixFactorial =>   write!(f, "{expr}{op}"),
  UnaryOperator::Not
                        | UnaryOperator::BitwiseNot
                        | UnaryOperator::Hash
                        | UnaryOperator::AtDashAt
                        | UnaryOperator::DoubleAt
                        | UnaryOperator::QuestionDash
                        | UnaryOperator::QuestionPipe =>  write!(f, "{op} {expr}"
  // TODO explcitly list out the other operators here so the list is explicitl
}

Also when I was typing that it seems like UnaryOperator::PGPostfixFactorial is the same as the else match 🤔

[alamb]

❤️

[alamb]

Nice -- thank you @LucaCappelletti94