makes most operators hidden friends #471
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This ensures that they're not placed in their function names' respecitve overload sets, which has a considerable impact on build times and on compiler diagnostics (as they're not listed as failed candidates when overload resolution fails).
Running an include tracer indicated that placing `size_hint_impl.h` in this header should prevent link-time errors when attempting to incidentally format `SizeHint`.
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| /// The `U` template type parameter allows `_sus_format_to_stream` to be a | ||
| /// hidden friend when `Type` is not a class template. Directly using `Type` | ||
| /// means that the function is immediately instantiated, and we'll get a | ||
| /// compile-time error unless `fmt::formatter` is specialised before `Type`'s | ||
| /// definition, since `fmt::is_formattable` doesn't know it's a formattable type | ||
| /// at this point in the code. This isn't a problem for primary class templates, | ||
| /// but it is problematic for regular classes and full specialisations. Using a | ||
| /// dependent type `U` defers instantiation until `operator<<` is first used. | ||
| /// We need to constrain `U` to be the same type as `Type`, otherwise it will | ||
| /// be ambiguous as to which overload we want. |
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This is some wild and wonderful compiler hijacking lol. Thanks for explaining it well.
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This ensures that they're not placed in their function names' respective overload sets, which has a considerable impact on build times and on compiler diagnostics (as they're not listed as failed candidates when overload resolution fails).