Print a space between adjacent prefix unary operators - #2424
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`Expr::UnaryOp`'s `Display` writes `{op}{expr}` with no separator, so when
the operand is itself a `UnaryOp` the two operator glyphs are emitted glued
together and the output no longer round-trips:
SELECT ~ ~ 1 -> SELECT ~~1 -> "Expected: an expression, found: ~~"
`SELECT - -1` prints as `SELECT --1`, which is the same defect but only
breaks on dialects where `--` opens a line comment; MySQL requires
whitespace after `--` and reparses it unchanged.
The Postgres case is worse than a parse error, because `@@` is a distinct
operator: `SELECT @ @ 1` (abs of abs) prints as `SELECT @@1` and silently
reparses as `UnaryOperator::DoubleAt` applied to `1`.
Extend the existing "needs a space" condition so it also fires when the
operand is another `Expr::UnaryOp`. Operators already in that list and
non-unary operands are unaffected, so `-1` and `NOT a` are unchanged.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Expr::UnaryOp'sDisplaywrites{op}{expr}with no separator, so a nested unary operand is printed glued to the operator:prints as
SELECT ~~1, which no longer reparses on any dialect (Expected: an expression, found: ~~).SELECT - -1prints asSELECT --1the same way; that one only breaks where--opens a line comment, so MySQL is unaffected.On PostgreSQL it changes meaning rather than failing, because
@@is its own operator:SELECT @ @ 1(abs of abs) prints asSELECT @@1, which reparses asUnaryOperator::DoubleAtapplied to1.The fix extends the existing "needs a space" condition so it also fires when the operand is another
Expr::UnaryOp. Non-unary operands are unchanged, so-1andNOT aprint as before.Tests are
parse_nested_unary_opsintests/sqlparser_common.rsandparse_nested_pg_unary_opsintests/sqlparser_postgres.rs; I checked that both fail without the source change. TheAGENTS.mdpre-commit checks are clean locally.