Add inherent constructors on str

[robertbastian]

#131114

Unresolved questions

Do we mark the core::str functions as future-deprecation? This will causes warnings when core::str is imported and str::from_utf8 is used, because the compiler decides to interpret that as the module, not the type.

[rustbot]

r? @Amanieu

rustbot has assigned @Amanieu.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[bors]

☔ The latest upstream changes (presumably #131269) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #131767) made this pull request unmergeable. Please resolve the merge conflicts.

[scottmcm]

Do we mark the core::str functions as future-deprecation?

I think it'll make your life much easier to do it in different PRs. Add the new ones first, then you can do separate PRs to update different parts of things to use the new ones, then once you're through that you can PR the future-deprecation.

(Keeping it locally will help you make those other PRs, but no need to check it in for a while.)

[alex-semenyuk]

@robertbastian
From wg-triage. Do you have any updates on this PR?

[robertbastian]

Sorry I'm afk until January 🙃

[alex-semenyuk]

@robertbastian
Thanks for your contribution

Sorry I'm afk until January 🙃

Do you have plans to proceed with this soon?

[robertbastian]

Thanks for the bump, will try to get to this today.

[tgross35]

There are a lot of places in this PR that change from std:str::* to the new inherent methods. Is there a reason for this? It would be much cleaner to add the inherent methods now, but don't replace any existing uses until a follow up PR (and once the feature is closer to stable).

[robertbastian]

because I've tried to future-deprecation-warning them, so I already cleaned up all usages

[tgross35]

Don't do that in the same PR. Add the unstable API first, we can consider encouraging the newer APIs somehow once this is closer to stabilization - but certainly not while it is unstable.

[robertbastian]

So that's basically undoing the whole PR.

[tgross35]

Don't move the existing diagnostic items. This feature will be unstable for a while, we don't want to break everything that relies on these in the meantime.

[robertbastian]

restored

[tgross35]

Can't this block be str::from_utf8_mut, rather than matching and calling str::from_utf8_unchecked_mut?

[robertbastian]

maybe, I feel like there's a reason why it isn't but that's lost to time

[tgross35]

This test shouldn't be needed once the compiler feature is removed.

[robertbastian]

removed

[tgross35]

Regarding the most recent test failure, it would be easiest for the new methods in this file to call the core::str::* functions rather than moving the implementations here.

[robertbastian]

I'd like these to be the canonical implementations

[tgross35]

That shouldn't matter, and can change in a future PR if there is a reason. For now it is cleanest to touch the existing methods as little as possible.

[tgross35]

rustc_const_unstable shouldn't be needed anymore for functions that are #[unstable(...)] and const

[robertbastian]

removed

[rust-log-analyzer]

The job x86_64-gnu-llvm-18 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#22 exporting to docker image format
#22 sending tarball 28.3s done
#22 DONE 32.3s
##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-18]
debug: `DISABLE_CI_RUSTC_IF_INCOMPATIBLE` configured.
---
sccache: Starting the server...
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-18', '--enable-llvm-link-shared', '--set', 'rust.randomize-layout=true', '--set', 'rust.thin-lto-import-instr-limit=10', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--set', 'rust.lld=false', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--enable-new-symbol-mangling']
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-18/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.randomize-layout := True
configure: rust.thin-lto-import-instr-limit := 10
---
-    |
- LL |         std::str::from_utf8_unchecked_mut(&mut [99, 108, 130, 105, 112, 112, 121]);
-    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^----------------------------------^
-    |                                                |
-    |                                                the literal was valid UTF-8 up to the 2 bytes
- note: the lint level is defined here
-   --> $DIR/invalid_from_utf8.rs:5:9
-    |
- LL | #![warn(invalid_from_utf8_unchecked)]
- LL | #![warn(invalid_from_utf8_unchecked)]
-    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
- 
- warning: calls to `std::str::from_utf8_unchecked_mut` with a invalid literal are undefined behavior
-   --> $DIR/invalid_from_utf8.rs:22:9
-    |
- LL |         std::str::from_utf8_unchecked_mut(&mut [b'c', b'l', b'\x82', b'i', b'p', b'p', b'y']);
-    |                                                |
-    |                                                |
-    |                                                the literal was valid UTF-8 up to the 2 bytes
- warning: calls to `std::str::from_utf8_unchecked` with a invalid literal are undefined behavior
-   --> $DIR/invalid_from_utf8.rs:40:9
-    |
- LL |         std::str::from_utf8_unchecked(&[99, 108, 130, 105, 112, 112, 121]);
- LL |         std::str::from_utf8_unchecked(&[99, 108, 130, 105, 112, 112, 121]);
-    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^----------------------------------^
-    |                                        |
-    |                                        the literal was valid UTF-8 up to the 2 bytes
- warning: calls to `std::str::from_utf8_unchecked` with a invalid literal are undefined behavior
-   --> $DIR/invalid_from_utf8.rs:42:9
-    |
-    |
- LL |         std::str::from_utf8_unchecked(&[b'c', b'l', b'\x82', b'i', b'p', b'p', b'y']);
-    |                                        |
-    |                                        |
-    |                                        the literal was valid UTF-8 up to the 2 bytes
- warning: calls to `std::str::from_utf8_unchecked` with a invalid literal are undefined behavior
-   --> $DIR/invalid_from_utf8.rs:44:9
-    |
-    |
- LL |         std::str::from_utf8_unchecked(b"cl\x82ippy");
-    |                                       |
-    |                                       |
-    |                                       the literal was valid UTF-8 up to the 2 bytes
- warning: calls to `std::str::from_utf8_unchecked` with a invalid literal are undefined behavior
-   --> $DIR/invalid_from_utf8.rs:46:9
-    |
-    |
- LL |         std::str::from_utf8_unchecked(concat_bytes!(b"cl", b"\x82ippy"));
-    |                                       |
-    |                                       |
-    |                                       the literal was valid UTF-8 up to the 2 bytes
55 warning: calls to `std::str::from_utf8_mut` with a invalid literal always return an error
56   --> $DIR/invalid_from_utf8.rs:63:9
57    |

---
To only update this specific test, also pass `--test-args lint/invalid_from_utf8.rs`

error: 1 errors occurred comparing output.
status: exit status: 0
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/lint/invalid_from_utf8.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/lint/invalid_from_utf8" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers"
--- stderr -------------------------------
warning: calls to `std::str::from_utf8_mut` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:63:9
   |
   |
LL |         std::str::from_utf8_mut(&mut [99, 108, 130, 105, 112, 112, 121]);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^----------------------------------^
   |                                      |
   |                                      the literal was valid UTF-8 up to the 2 bytes
note: the lint level is defined here
  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:6:9
   |
LL | #![warn(invalid_from_utf8)]
LL | #![warn(invalid_from_utf8)]
   |         ^^^^^^^^^^^^^^^^^

warning: calls to `std::str::from_utf8_mut` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:65:9
   |
LL |         std::str::from_utf8_mut(&mut [b'c', b'l', b'\x82', b'i', b'p', b'p', b'y']);
   |                                      |
   |                                      |
   |                                      the literal was valid UTF-8 up to the 2 bytes
warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:83:9
   |
LL |         std::str::from_utf8(&[99, 108, 130, 105, 112, 112, 121]);
LL |         std::str::from_utf8(&[99, 108, 130, 105, 112, 112, 121]);
   |         ^^^^^^^^^^^^^^^^^^^^^----------------------------------^
   |                              |
   |                              the literal was valid UTF-8 up to the 2 bytes
warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:85:9
   |
   |
LL |         std::str::from_utf8(&[b'c', b'l', b'\x82', b'i', b'p', b'p', b'y']);
   |                              |
   |                              |
   |                              the literal was valid UTF-8 up to the 2 bytes
warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:87:9
   |
   |
LL |         std::str::from_utf8(b"cl\x82ippy");
   |                             |
   |                             |
   |                             the literal was valid UTF-8 up to the 2 bytes
warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:89:9
   |
   |
LL |         std::str::from_utf8(concat_bytes!(b"cl", b"\x82ippy"));
   |                             |
   |                             |
   |                             the literal was valid UTF-8 up to the 2 bytes
warning: calls to `std::str::from_utf8_mut` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:96:5
   |
LL |     let mut a = [99, 108, 130, 105, 112, 112, 121];
LL |     let mut a = [99, 108, 130, 105, 112, 112, 121];
   |                 ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8_mut(&mut a);

warning: calls to `std::str::from_utf8_mut` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:100:5
   |
   |
LL |     let mut a = [99, 108, 130, 105, 112, 112, 121];
   |                 ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8_mut(c);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: calls to `std::str::from_utf8` with a invalid literal always return an error
warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:103:5
   |
LL |     let mut c = &[99, 108, 130, 105, 112, 112, 121];
   |                  ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8(c);

warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:106:5
   |
   |
LL |     const INVALID_1: [u8; 7] = [99, 108, 130, 105, 112, 112, 121];
   |                                ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8(&INVALID_1);

warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:109:5
   |
   |
LL |     static INVALID_2: [u8; 7] = [99, 108, 130, 105, 112, 112, 121];
   |                                 ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8(&INVALID_2);

warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:112:5
   |
   |
LL |     const INVALID_3: &'static [u8; 7] = &[99, 108, 130, 105, 112, 112, 121];
   |                                          ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8(INVALID_3);

warning: calls to `std::str::from_utf8` with a invalid literal always return an error
##[warning]  --> /checkout/tests/ui/lint/invalid_from_utf8.rs:115:5
   |
   |
LL |     const INVALID_4: &'static [u8; 7] = { &[99, 108, 130, 105, 112, 112, 121] };
   |                                            ---------------------------------- the literal was valid UTF-8 up to the 2 bytes
LL |     std::str::from_utf8(INVALID_4);

warning: 13 warnings emitted
------------------------------------------



---- [ui] tests/ui/suggestions/suggest-std-when-using-type.rs stdout ----
Saved the actual stderr to "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/suggest-std-when-using-type/suggest-std-when-using-type.stderr"
diff of stderr:

9 LL |     let pi = std::f32::consts::PI;
11 
- error[E0599]: no function or associated item named `from_utf8` found for type `str` in the current scope
-   --> $DIR/suggest-std-when-using-type.rs:5:23
+ error[E0658]: use of unstable library feature `inherent_str_constructors`
+ error[E0658]: use of unstable library feature `inherent_str_constructors`
+   --> $DIR/suggest-std-when-using-type.rs:5:18
14    |
15 LL |     let string = str::from_utf8(bytes).unwrap();
+    |                  ^^^^^^^^^^^^^^
17    |
- help: you are looking for the module in `std`, not the primitive type
-    |
-    |
- LL |     let string = std::str::from_utf8(bytes).unwrap();
+    = note: see issue #131114 <https://github.com/rust-lang/rust/issues/131114> for more information
+    = help: add `#![feature(inherent_str_constructors)]` to the crate attributes to enable
+    = help: add `#![feature(inherent_str_constructors)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
23 error: aborting due to 2 previous errors
24 

- Some errors have detailed explanations: E0223, E0599.
---
+ error[E0658]: use of unstable library feature `inherent_str_constructors`
+   --> $DIR/suggest-std-when-using-type.rs:5:18
+    |                  ^^^^^^^^^^^^^^
+    = note: see issue #131114 <https://github.com/rust-lang/rust/issues/131114> for more information
+    = help: add `#![feature(inherent_str_constructors)]` to the crate attributes to enable
+    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date


The actual stderr differed from the expected stderr.
Saved the actual fixed to "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/suggest-std-when-using-type/suggest-std-when-using-type.fixed"
Saved the actual fixed to "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/suggest-std-when-using-type/suggest-std-when-using-type.fixed"
diff of fixed:

2 fn main() {
3     let pi = std::f32::consts::PI; //~ ERROR ambiguous associated type
4     let bytes = "hello world".as_bytes();
-     let string = std::str::from_utf8(bytes).unwrap();
+     let string = str::from_utf8(bytes).unwrap();
6     //~^ ERROR no function or associated item named `from_utf8` found
7     println!("{pi} {bytes:?} {string}");


The actual fixed differed from the expected fixed.
To update references, rerun the tests and pass the `--bless` flag
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args suggestions/suggest-std-when-using-type.rs`

error: 2 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/suggestions/suggest-std-when-using-type.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/suggestions/suggest-std-when-using-type" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers"
--- stderr -------------------------------
error[E0223]: ambiguous associated type
##[error]  --> /checkout/tests/ui/suggestions/suggest-std-when-using-type.rs:3:14
   |
   |
LL |     let pi = f32::consts::PI; //~ ERROR ambiguous associated type
   |
help: you are looking for the module in `std`, not the primitive type
   |
   |
LL |     let pi = std::f32::consts::PI; //~ ERROR ambiguous associated type

error[E0658]: use of unstable library feature `inherent_str_constructors`
##[error]  --> /checkout/tests/ui/suggestions/suggest-std-when-using-type.rs:5:18
   |
   |
LL |     let string = str::from_utf8(bytes).unwrap();
   |
   = note: see issue #131114 <https://github.com/rust-lang/rust/issues/131114> for more information
   = help: add `#![feature(inherent_str_constructors)]` to the crate attributes to enable
   = help: add `#![feature(inherent_str_constructors)]` 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 2 previous errors

Some errors have detailed explanations: E0223, E0658.
For more information about an error, try `rustc --explain E0223`.

[robertbastian]

I'm closing this because I cannot be bothered. This is way more work than it should be.

[tgross35]

The initial change should only be additions to library/core/src/str/mod.rs that call to the existing std::str methods - that should be reasonably straightforward if you are interested in putting only these changes into a new PR (only the one file needs to be updated).

We should not be deprecating, migrating, or changing diagnostics for anything at the same time, especially without a stable replacement (yet). Attempting to do this at once is part of why the changes seems more complex than needed (doing so requires updates to the compiler and tests).