D110833: [clang-format] Refactor SpaceBeforeParens to add options regressed behavior of spaces before parentheses for operators, this revision reverts that so that operators are handled as they were before.
I think in hindsight it was a mistake to try and consume operator behaviour in with the function behaviour, I think Operators can be considered a special style. Its seems the code is getting confused as to if this is a function declaration or definition.
I think latterly we can consider adding an operator parentheses specific custom option but this should have been explicitly called out as it can impact projects.