core: implement float conversion methods by valentynkit · Pull Request #159954 · rust-lang/rust

valentynkit · 2026-07-26T09:00:53Z

Implements the accepted ACP rust-lang/libs-team#810, adding float conversion methods on f16, f32, f64, and f128:

cast converts to the target float type (self as Flt, IEEE rounding).
to_int_saturating converts to an integer with as semantics: saturating, and NaN to 0.
to_int_checked truncates toward zero and returns None on NaN, infinity, or out of range.
to_int_strict is to_int_checked().unwrap().

Per the libs-api meetings on the ACP, to_float is named cast and to_int_saturating maps NaN to 0 rather than panicking (which the team noted makes rust-lang/libs-team#831 redundant).

The integer-to-float cast from the ACP is left out: it shares the cast method name on integer types with the integer-to-integer cast in rust-lang/libs-team#811 (being unified with the other integer cast methods in rust-lang/libs-team#833), so it needs a decision on how those fit together. Happy to follow up once that settles.

Tracking issue: #159913

r? libs

valentynkit · 2026-07-28T19:08:29Z

The Codegen Cranelift failure was a pre-existing cg_clif bug in f128 as {i8,i16,u8,u16}, unrelated to this PR.
Reported in #1680 fixed by rust-lang/rustc_codegen_cranelift@29b920534.
Probably need time to sync the fix from latest changes in rustc codegen cranelift?..

JohnTitor · 2026-08-15T10:47:04Z

Seems still failed, is it synced yet or any other issues happen?

valentynkit · 2026-08-15T11:10:54Z

Seems still failed, is it synced yet or any other issues happen?

Not synced yet. The fix is rust-lang/rustc_codegen_cranelift@29b9205 and the last subtree sync was #159712.
So current CI failures, are still because of this bug, when it will be synced it should pass.
I re triggered the CI and expected it to be already synced, but it is not.

JohnTitor · 2026-08-17T09:45:43Z

Alright, cc @bjorn3 for awareness
marking as blocked until it gets synced.

rustbot · 2026-08-21T10:23:03Z

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.

valentynkit · 2026-08-21T15:00:03Z

@rustbot ready
Unblocked

JohnTitor

LGTM, @bors r+

View changes since this review

rust-bors · 2026-08-21T22:35:20Z

📌 Commit 3c55beb has been approved by JohnTitor

It is now in the queue for this repository.

…ohnTitor core: implement float conversion methods Implements the accepted ACP rust-lang/libs-team#810, adding float conversion methods on `f16`, `f32`, `f64`, and `f128`: - `cast` converts to the target float type (`self as Flt`, IEEE rounding). - `to_int_saturating` converts to an integer with `as` semantics: saturating, and `NaN` to 0. - `to_int_checked` truncates toward zero and returns `None` on `NaN`, infinity, or out of range. - `to_int_strict` is `to_int_checked().unwrap()`. Per the libs-api meetings on the ACP, `to_float` is named `cast` and `to_int_saturating` maps `NaN` to 0 rather than panicking (which the team noted makes rust-lang/libs-team#831 redundant). The integer-to-float `cast` from the ACP is left out: it shares the `cast` method name on integer types with the integer-to-integer `cast` in rust-lang/libs-team#811 (being unified with the other integer cast methods in rust-lang/libs-team#833), so it needs a decision on how those fit together. Happy to follow up once that settles. Tracking issue: rust-lang#159913 r? libs

…uwer Rollup of 18 pull requests Successful merges: - #151061 (Build rustc and codegen backends with -Zembed-metadata=no) - #157949 (Allow self in const generics) - #158588 (trait_selection: fix assumptions-on-binders diagnostics) - #159954 (core: implement float conversion methods) - #160136 (Add `Default` implementation for `std::sync::Once`) - #160835 (resolver diagnostics: don't swallow labels and point out similar items as a note, not a label) - #161048 (Improve the ABI between the panic runtime and libstd) - #161292 (Add safety comments in alloc::Wtf8) - #161444 (Add some `rustc_type_ir` comments) - #161465 (Remove leftover immediate creation) - #152433 (Use `symlink_dir` to create junctions on Windows instead of trying to use symbolic links in `copy_link_internal`) - #159098 (Add Arc/Rc::strong_count_from_raw) - #159282 (Update documentation for `-Zdump-dep-graph`) - #161401 (Remove fields from TypeKind: Bool, Char, Float and Int) - #161431 (bootstrap: (offload) be stricter about selected compiler and paths) - #161451 (Avoid arming the Windows TLS destructor guard in fibers) - #161463 (Add myself to mailmap) - #161476 (Use bitset for locals_with_use_data) Failed merges: - #161443 (add internal DSL for testing binders)

…ohnTitor core: implement float conversion methods Implements the accepted ACP rust-lang/libs-team#810, adding float conversion methods on `f16`, `f32`, `f64`, and `f128`: - `cast` converts to the target float type (`self as Flt`, IEEE rounding). - `to_int_saturating` converts to an integer with `as` semantics: saturating, and `NaN` to 0. - `to_int_checked` truncates toward zero and returns `None` on `NaN`, infinity, or out of range. - `to_int_strict` is `to_int_checked().unwrap()`. Per the libs-api meetings on the ACP, `to_float` is named `cast` and `to_int_saturating` maps `NaN` to 0 rather than panicking (which the team noted makes rust-lang/libs-team#831 redundant). The integer-to-float `cast` from the ACP is left out: it shares the `cast` method name on integer types with the integer-to-integer `cast` in rust-lang/libs-team#811 (being unified with the other integer cast methods in rust-lang/libs-team#833), so it needs a decision on how those fit together. Happy to follow up once that settles. Tracking issue: rust-lang#159913 r? libs

…uwer Rollup of 19 pull requests Successful merges: - #151061 (Build rustc and codegen backends with -Zembed-metadata=no) - #154992 (Error on projection of dyn noncompat type in old trait solver) - #157949 (Allow self in const generics) - #158588 (trait_selection: fix assumptions-on-binders diagnostics) - #159954 (core: implement float conversion methods) - #160136 (Add `Default` implementation for `std::sync::Once`) - #160835 (resolver diagnostics: don't swallow labels and point out similar items as a note, not a label) - #161048 (Improve the ABI between the panic runtime and libstd) - #161292 (Add safety comments in alloc::Wtf8) - #161444 (Add some `rustc_type_ir` comments) - #161465 (Remove leftover immediate creation) - #159098 (Add Arc/Rc::strong_count_from_raw) - #159282 (Update documentation for `-Zdump-dep-graph`) - #161401 (Remove fields from TypeKind: Bool, Char, Float and Int) - #161431 (bootstrap: (offload) be stricter about selected compiler and paths) - #161451 (Avoid arming the Windows TLS destructor guard in fibers) - #161463 (Add myself to mailmap) - #161476 (Use bitset for locals_with_use_data) - #161483 (Warn about running ui-fulldeps tests in stage 1) Failed merges: - #161443 (add internal DSL for testing binders)

Rollup merge of #159954 - valentynkit:float-conversions, r=JohnTitor core: implement float conversion methods Implements the accepted ACP rust-lang/libs-team#810, adding float conversion methods on `f16`, `f32`, `f64`, and `f128`: - `cast` converts to the target float type (`self as Flt`, IEEE rounding). - `to_int_saturating` converts to an integer with `as` semantics: saturating, and `NaN` to 0. - `to_int_checked` truncates toward zero and returns `None` on `NaN`, infinity, or out of range. - `to_int_strict` is `to_int_checked().unwrap()`. Per the libs-api meetings on the ACP, `to_float` is named `cast` and `to_int_saturating` maps `NaN` to 0 rather than panicking (which the team noted makes rust-lang/libs-team#831 redundant). The integer-to-float `cast` from the ACP is left out: it shares the `cast` method name on integer types with the integer-to-integer `cast` in rust-lang/libs-team#811 (being unified with the other integer cast methods in rust-lang/libs-team#833), so it needs a decision on how those fit together. Happy to follow up once that settles. Tracking issue: #159913 r? libs

rustbot assigned JohnTitor Jul 26, 2026

rustbot added 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 Jul 26, 2026

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valentynkit mentioned this pull request Jul 27, 2026

Cranelift backend miscompiles f128 casts to i8/i16/u8/u16 rust-lang/rustc_codegen_cranelift#1680

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valentynkit force-pushed the float-conversions branch from 1706b22 to 95876c9 Compare August 12, 2026 16:15

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JohnTitor added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 17, 2026

core: implement float conversion methods

3c55beb

valentynkit force-pushed the float-conversions branch from 95876c9 to 3c55beb Compare August 21, 2026 10:23

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-blocked Status: Blocked on something else such as an RFC or other implementation work. labels Aug 21, 2026

valentynkit mentioned this pull request Aug 21, 2026

Tracking Issue for float conversion methods (float_conversions) #159913

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JohnTitor approved these changes Aug 21, 2026

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rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 21, 2026

JonathanBrouwer mentioned this pull request Aug 21, 2026

Rollup of 19 pull requests #161489

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JonathanBrouwer mentioned this pull request Aug 22, 2026

Rollup of 18 pull requests #161494

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jhpratt mentioned this pull request Aug 22, 2026

Rollup of 19 pull requests #161497

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JonathanBrouwer mentioned this pull request Aug 22, 2026

Rollup of 18 pull requests #161498

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This was referenced Aug 22, 2026

Rollup of 18 pull requests #161501

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Rollup of 19 pull requests #161505

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rust-bors Bot merged commit f5ca205 into rust-lang:main Aug 22, 2026
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rustbot added this to the 1.100.0 milestone Aug 22, 2026

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core: implement float conversion methods - #159954

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