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unstable impl of From<{i64, u64}> for f128 #154012

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rust-bors merged 1 commit into from
Mar 18, 2026
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unstable impl of From<{i64, u64}> for f128 #154012

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10 changes: 4 additions & 6 deletions library/core/src/convert/num.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -70,8 +70,8 @@ impl_from_bool!(i8 i16 i32 i64 i128 isize);

/// Implement `From<$small>` for `$large`
macro_rules! impl_from {
($small:ty => $large:ty, #[$attr:meta]) => {
#[$attr]
($small:ty => $large:ty, $(#[$attrs:meta]),+) => {
$(#[$attrs])+
#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
impl const From<$small> for $large {
#[doc = concat!("Converts from [`", stringify!($small), "`] to [`", stringify!($large), "`] losslessly.")]
Expand Down Expand Up @@ -157,8 +157,7 @@ impl_from!(i16 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0"
impl_from!(i16 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i32 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i32 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
// FIXME(f128): This impl would allow using `f128` on stable before it is stabilised.
// impl_from!(i64 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(i64 => f128, #[unstable(feature = "f128", issue = "116909")], #[unstable_feature_bound(f128)]);

// unsigned integer -> float
impl_from!(u8 => f16, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
Expand All @@ -170,8 +169,7 @@ impl_from!(u16 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0"
impl_from!(u16 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u32 => f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u32 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
// FIXME(f128): This impl would allow using `f128` on stable before it is stabilised.
// impl_from!(u64 => f128, #[stable(feature = "lossless_float_conv", since = "1.6.0")]);
impl_from!(u64 => f128, #[unstable(feature = "f128", issue = "116909")], #[unstable_feature_bound(f128)]);

// float -> float
// FIXME(f16,f128): adding additional `From<{float}>` impls to `f32` breaks inference. See
Expand Down
37 changes: 34 additions & 3 deletions tests/ui/feature-gates/feature-gate-f128.e2015.stderr
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Expand Up @@ -19,7 +19,27 @@ LL | let a: f128 = 100.0;
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:16:11
--> $DIR/feature-gate-f128.rs:13:12
|
LL | let d: f128 = 1i64.into();
| ^^^^
|
= note: see issue #116909 <https://github.com/rust-lang/rust/issues/116909> for more information
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:16:12
|
LL | let e: f128 = 1u64.into();
| ^^^^
|
= note: see issue #116909 <https://github.com/rust-lang/rust/issues/116909> for more information
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:21:11
|
LL | fn foo(a: f128) {}
| ^^^^
Expand All @@ -29,7 +49,7 @@ LL | fn foo(a: f128) {}
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:19:8
--> $DIR/feature-gate-f128.rs:24:8
|
LL | a: f128,
| ^^^^
Expand Down Expand Up @@ -58,6 +78,17 @@ LL | let c = 0f128;
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 6 previous errors
error[E0658]: use of unstable library feature `f128`
--> $DIR/feature-gate-f128.rs:13:24
|
LL | let d: f128 = 1i64.into();
| ^^^^
|
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: required for `f128` to implement `From<i64>`
= note: required for `i64` to implement `Into<f128>`

error: aborting due to 9 previous errors

For more information about this error, try `rustc --explain E0658`.
37 changes: 34 additions & 3 deletions tests/ui/feature-gates/feature-gate-f128.e2018.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,27 @@ LL | let a: f128 = 100.0;
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:16:11
--> $DIR/feature-gate-f128.rs:13:12
|
LL | let d: f128 = 1i64.into();
| ^^^^
|
= note: see issue #116909 <https://github.com/rust-lang/rust/issues/116909> for more information
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:16:12
|
LL | let e: f128 = 1u64.into();
| ^^^^
|
= note: see issue #116909 <https://github.com/rust-lang/rust/issues/116909> for more information
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:21:11
|
LL | fn foo(a: f128) {}
| ^^^^
Expand All @@ -29,7 +49,7 @@ LL | fn foo(a: f128) {}
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the type `f128` is unstable
--> $DIR/feature-gate-f128.rs:19:8
--> $DIR/feature-gate-f128.rs:24:8
|
LL | a: f128,
| ^^^^
Expand Down Expand Up @@ -58,6 +78,17 @@ LL | let c = 0f128;
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 6 previous errors
error[E0658]: use of unstable library feature `f128`
--> $DIR/feature-gate-f128.rs:13:24
|
LL | let d: f128 = 1i64.into();
| ^^^^
|
= help: add `#![feature(f128)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= note: required for `f128` to implement `From<i64>`
= note: required for `i64` to implement `Into<f128>`

error: aborting due to 9 previous errors

For more information about this error, try `rustc --explain E0658`.
5 changes: 5 additions & 0 deletions tests/ui/feature-gates/feature-gate-f128.rs
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Expand Up @@ -10,6 +10,11 @@ pub fn main() {
let a: f128 = 100.0; //~ ERROR the type `f128` is unstable
let b = 0.0f128; //~ ERROR the type `f128` is unstable
let c = 0f128; //~ ERROR the type `f128` is unstable
let d: f128 = 1i64.into();
//~^ ERROR the type `f128` is unstable
//~| ERROR use of unstable library feature `f128`
let e: f128 = 1u64.into();
//~^ ERROR the type `f128` is unstable
foo(1.23);
}

Expand Down
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