Split the `dec2flt::RawFloat` trait for easier reuse by tgross35 · Pull Request #151905 · rust-lang/rust

tgross35 · 2026-01-31T11:33:17Z

RawFloat is an internal trait with quite a few useful float properties. It currently resides in the dec2flt module but is also used in parsing, and would be nice to reuse other places. Unfortunately it cannot be implemented on f128 because of limitations with how the parsing API is implemented (mantissa must fit into a u64).

To make the trait easier to work with, split it into the following:

Float: Anything that is reasonably applicable to all floating point types.
FloatExt: Items that should be part of Float but don't work for all float types. This will eventually be merged back into Float once it can be implemented on f128.
Lemire: Items that are specific to the Lemire dec2flt algorithm.

These traits are then moved to places that make sense.

Builds on top of #151900

rustbot · 2026-01-31T11:33:20Z

triagebot.toml has been modified, there may have been changes to the review queue.

cc @davidtwco, @wesleywiser

rustbot · 2026-01-31T11:33:22Z

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tgross35 · 2026-01-31T11:33:47Z

The first two commits can be ignored since they are part of #151900

Currently we have a single `core::num` module that contains both thin wrapper API and higher-complexity numeric routines. Restructure this by moving implementation details to a new `imp` module. This results in a more clean separation of what is actually user-facing compared to items that have a stability attribute because they are public for testing.

rustbot · 2026-02-11T23:33:04Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

Follow up to the previous commit refactoring `core::num` by moving the user-facing error types and trait implementations back out of `imp` and into a new module under `core::num`.

This is more consistent with what the trait is called elsewhere in tree (specifically compiler-builtins and test-float-parse).

`RawFloat` is currently used specifically for the implementation of the lemire algorithm, but it is useful for more than that. Split it into three different traits: * `Float`: Anything that is reasonably applicable to all floating point types. * `FloatExt`: Items that should be part of `Float` but don't work for all float types. This will eventually be merged back into `Float`. * `Lemire`: Items that are specific to the Lemire algorithm.

`Float` and `FloatExt` are already used by both parsing and printing, so move them out of `dec2flt` to a new module in `num::imp`. `Int` `Cast` have the potential to be used more places in the future, so move them there as well. `Lemire` is the only remaining trait; since it is small, move it into the `dec2flt` root. The `fmt::LowerExp` bound is removed from `Float` here since the trait is moving into a module without `#[cfg(not(no_fp_fmt_parse))]` and it isn't implemented with that config (it's not easily possible to add `cfg` attributes to a single supertrait, unfortunately). This isn't a problem since it isn't actually being used.

tgross35 · 2026-02-13T13:12:43Z

Yay, this one is ready too

@rustbot ready

This is stacked on on #151900 so the last few (smaller) commits are the relevant bit here.

rustbot added A-meta Area: Issues & PRs about the rust-lang/rust repository itself S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jan 31, 2026

rustbot assigned scottmcm Jan 31, 2026

tgross35 force-pushed the dec2flt-traits branch from 9837f1e to ec32d31 Compare January 31, 2026 11:36