Add _value API for number literals in proc-macro

[GuillaumeGomez]

View all comments

Part of #136652.

This PR adds the *_value for numbers (integers and floats). However, f16 and f128 are voluntarily left out as they're still unstable. Adding support for them is just a matter of uncommenting two lines, so should be fine.

Setting same reviewer as last time.

r? @Urgau

[GuillaumeGomez]

My favourite kind of failure: works locally but not in CI. T_T

Updated the value in the tests to see which one exactly is failing.

[GuillaumeGomez]

Bug comes from an issue with GCC proc-macro ABI. Ignoring this test on GCC backend for now.

[GuillaumeGomez]

CI fixed. :)

[Urgau]

A libs (or maybe even libs-api) reviewer seems more appropriate to review this PR.

r? Amanieu (since you reviewed #136355)

[Urgau]

I missed it already has an accepted ACP. The PR can be reviewed by libs reviewer.

r? libs

[Mark-Simulacrum]

Is this exactly in sync with what the rustc parser permits?

I guess that would be a mix of https://doc.rust-lang.org/nightly/reference/tokens.html#grammar-INTEGER_LITERAL and whatever we then tokenize from it?

Perhaps this should go over the bridge and ask rustc to parse the string for us?

[GuillaumeGomez]

There is no code in rustc currently which would allow this conversion without including a lot of other things. My code is a simplified version of integer_lit (from rustc_ast/src/util/literal.rs) which parses both the number, its base and its suffix (which we already have) and returns a LitKind, which is also unnecessary here since we already know the end type.

[Mark-Simulacrum]

I think my question is not about specific code in rustc but rather whether the implementation here parses exactly the same literals that rustc would from the given token(s). Is that the case? Essentially, can we document these functions as being bug-for-bug compatible with what rustc would do, or do we need a separate grammar for this?

[GuillaumeGomez]

At this point, the compiler already ran on the literal so all errors have been checked already. The remaining potential errors mostly come from trying to convert a int/float not fitting the expected output.

[GuillaumeGomez]

Added the method for f16, renamed the function only_digits into strip_underscores and improve the code of parse_number a bit to remove allocations.

[GuillaumeGomez]

Forgot to change the status.

@rustbot ready

cc @Mark-Simulacrum

[Mark-Simulacrum]

Can you reply to my comment here? #154608 (comment)

@rustbot author

[GuillaumeGomez]

Forgot to do so. Answered it.

@rustbot ready

[Mark-Simulacrum]

I added an unresolved question to follow up on the equivalency, for now this can go in since it's unstable. I think we want a stronger guarantee than I think you're saying this has right now (as noted in the question on the tracking issue).

@bors r+

[rust-bors]

📌 Commit ebb3161 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[JonathanBrouwer]

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #157536 (comment)

[rust-bors]

This pull request was unapproved.

This PR was contained in a rollup (#157536), which was unapproved.

View changes since this unapproval

[rustbot]

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.

[GuillaumeGomez]

Ah I see, #![feature(f16)] is not enough. I added an extra cfg check on the assert calls to ensure it's only run when it can actually work.

Also rebased on main because of the bot's message.

@bors try x86_64-mingw-1

[rust-bors]

Unknown argument "x86_64-mingw-1". Did you mean to use @bors jobs=<jobs>|parent=<parent>? Run @bors help to see available commands.

[GuillaumeGomez]

@bors try jobs=x86_64-mingw-1

[rust-log-analyzer]

The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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

---- [ui] tests/ui/proc-macro/test.rs stdout ----

error: auxiliary build of /checkout/tests/ui/proc-macro/auxiliary/api/proc_macro_api_tests.rs failed to compile: 
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/proc-macro/auxiliary/api/proc_macro_api_tests.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/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-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" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/proc-macro/test/auxiliary" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "--edition=2021" "--crate-type" "proc-macro" "--extern" "proc_macro" "-L" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/proc-macro/test/auxiliary"
stdout: none
--- stderr -------------------------------
error[E0658]: `cfg(target_has_reliable_f16)` is experimental and subject to change
##[error]  --> /checkout/tests/ui/proc-macro/auxiliary/api/literal.rs:105:13
   |
LL |     if cfg!(target_has_reliable_f16) {
   |             ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(cfg_target_has_reliable_f16_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]: `cfg(target_has_reliable_f16)` is experimental and subject to change
##[error]  --> /checkout/tests/ui/proc-macro/auxiliary/api/literal.rs:111:13
   |
LL |     if cfg!(target_has_reliable_f16) {
   |             ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(cfg_target_has_reliable_f16_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

warning: unexpected `cfg` condition name: `target_has_reliable_f16`
##[warning]  --> /checkout/tests/ui/proc-macro/auxiliary/api/literal.rs:105:13
   |
LL |     if cfg!(target_has_reliable_f16) {

[rust-bors]

💔 Test for 1d1d12a failed: CI. Failed job:

• try - x86_64-mingw-1 (web logs, enhanced plaintext logs)

[rust-log-analyzer]

The job x86_64-mingw-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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

failures:

---- [ui] tests\ui\proc-macro\test.rs stdout ----

error: auxiliary build of D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api/proc_macro_api_tests.rs failed to compile: 
status: exit code: 1
command: PATH="D:\a\rust\rust\build\x86_64-pc-windows-gnu\stage2\bin;D:\a\rust\rust\build\x86_64-pc-windows-gnu\bootstrap-tools\x86_64-pc-windows-gnu\release\deps;D:\a\rust\rust\ninja;D:\a\rust\rust\mingw64\bin;C:\msys64\usr\bin;D:\a\rust\rust\sccache;C:\Program Files\MongoDB\Server\7.0\bin;C:\vcpkg;C:\tools\zstd;C:\hostedtoolcache\windows\stack\3.9.3\x64;C:\cabal\bin;C:\ghcup\bin;C:\mingw64\bin;C:\Program Files\dotnet;C:\Program Files\MySQL\MySQL Server 8.0\bin;C:\Program Files\R\R-4.6.0\bin\x64;C:\SeleniumWebDrivers\GeckoDriver;C:\SeleniumWebDrivers\EdgeDriver;C:\SeleniumWebDrivers\ChromeDriver;C:\Program Files (x86)\sbt\bin;C:\Program Files (x86)\GitHub CLI;C:\Program Files\Git\bin;C:\Program Files (x86)\pipx_bin;C:\npm\prefix;C:\hostedtoolcache\windows\go\1.24.13\x64\bin;C:\hostedtoolcache\windows\Python\3.12.10\x64\Scripts;C:\hostedtoolcache\windows\Python\3.12.10\x64;C:\hostedtoolcache\windows\Ruby\3.3.11\x64\bin;C:\Program Files\OpenSSL\bin;C:\tools\kotlinc\bin;C:\hostedtoolcache\windows\Java_Temurin-Hotspot_jdk\17.0.19-10\x64\bin;C:\Program Files\ImageMagick-7.1.2-Q16-HDRI;C:\Program Files\Microsoft SDKs\Azure\CLI2\wbin;C:\ProgramData\kind;C:\ProgramData\Chocolatey\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0;C:\Windows\System32\OpenSSH;C:\Program Files\PowerShell\7;C:\Program Files\Microsoft\Web Platform Installer;C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\170\Tools\Binn;C:\Program Files\Microsoft SQL Server\150\Tools\Binn;C:\Program Files\dotnet;C:\Program Files (x86)\Windows Kits\10\Windows Performance Toolkit;C:\Program Files (x86)\WiX Toolset v3.14\bin;C:\Program Files\Microsoft SQL Server\130\DTS\Binn;C:\Program Files\Microsoft SQL Server\140\DTS\Binn;C:\Program Files\Microsoft SQL Server\150\DTS\Binn;C:\Program Files\Microsoft SQL Server\160\DTS\Binn;C:\Program Files\Microsoft SQL Server\170\DTS\Binn;C:\ProgramData\chocolatey\lib\pulumi\tools\Pulumi\bin;C:\Program Files\CMake\bin;C:\Strawberry\c\bin;C:\Strawberry\perl\site\bin;C:\Strawberry\perl\bin;C:\ProgramData\chocolatey\lib\maven\apache-maven-3.9.16\bin;C:\Program Files\Microsoft Service Fabric\bin\Fabric\Fabric.Code;C:\Program Files\Microsoft SDKs\Service Fabric\Tools\ServiceFabricLocalClusterManager;C:\Program Files\nodejs;C:\Program Files\Git\cmd;C:\Program Files\Git\mingw64\bin;C:\Program Files\Git\usr\bin;C:\Program Files\GitHub CLI;C:\tools\php;C:\Program Files (x86)\sbt\bin;C:\Program Files\Amazon\AWSCLIV2;C:\Program Files\Amazon\SessionManagerPlugin\bin;C:\Program Files\Amazon\AWSSAMCLI\bin;C:\Program Files\Microsoft SQL Server\130\Tools\Binn;C:\Program Files\mongosh;C:\Program Files\LLVM\bin;C:\Program Files (x86)\LLVM\bin;C:\Users\runneradmin\.dotnet\tools;C:\Users\runneradmin\.cargo\bin;C:\Users\runneradmin\AppData\Local\Microsoft\WindowsApps" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\stage2\\bin\\rustc.exe" "D:\\a\\rust\\rust\\tests\\ui\\proc-macro\\auxiliary\\api/proc_macro_api_tests.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=C:\\Users\\runneradmin\\.cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=D:\\a\\rust\\rust\\vendor" "--sysroot" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\stage2" "--target=x86_64-pc-windows-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" "-C" "prefer-dynamic" "--out-dir" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\ui\\proc-macro\\test\\auxiliary" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\native\\rust-test-helpers" "--edition=2021" "--crate-type" "proc-macro" "--extern" "proc_macro" "-L" "D:\\a\\rust\\rust\\build\\x86_64-pc-windows-gnu\\test\\ui\\proc-macro\\test\\auxiliary"
stdout: none
--- stderr -------------------------------
error[E0658]: `cfg(target_has_reliable_f16)` is experimental and subject to change
##[error]  --> D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api\literal.rs:105:13
   |
LL |     if cfg!(target_has_reliable_f16) {
   |             ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(cfg_target_has_reliable_f16_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]: `cfg(target_has_reliable_f16)` is experimental and subject to change
##[error]  --> D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api\literal.rs:111:13
   |
LL |     if cfg!(target_has_reliable_f16) {
   |             ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(cfg_target_has_reliable_f16_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

warning: unexpected `cfg` condition name: `target_has_reliable_f16`
##[warning]  --> D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api\literal.rs:105:13
   |
LL |     if cfg!(target_has_reliable_f16) {
   |             ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: expected names are: `FALSE` and `test` and 32 more
   = help: to expect this configuration use `--check-cfg=cfg(target_has_reliable_f16)`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
   = note: `#[warn(unexpected_cfgs)]` on by default

warning: unexpected `cfg` condition name: `target_has_reliable_f16`
##[warning]  --> D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api\literal.rs:111:13
   |
LL |     if cfg!(target_has_reliable_f16) {
   |             ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: to expect this configuration use `--check-cfg=cfg(target_has_reliable_f16)`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration

warning: the `#![feature]` attribute can only be used at the crate root
##[warning]  --> D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api\literal.rs:3:1
   |
LL | #![feature(f16)]
   | ^^^^^^^^^^^^^^^^
   |
   = help: the crate root is at `D:\a\rust\rust\tests\ui\proc-macro\auxiliary\api/proc_macro_api_tests.rs`
   = note: `#[warn(unused_attributes)]` (part of `#[warn(unused)]`) on by default

error: aborting due to 2 previous errors; 3 warnings emitted

For more information about this error, try `rustc --explain E0658`.
---

Some tests failed in compiletest suite=ui mode=ui host=x86_64-pc-windows-gnu target=x86_64-pc-windows-gnu
Bootstrap failed while executing `test --stage 2 --skip=compiler --skip=src`
Build completed unsuccessfully in 1:24:59
make: *** [Makefile:126: ci-mingw-x] Error 1
  local time: Sun Jun  7 00:13:39 CUT 2026
  network time: Sun, 07 Jun 2026 00:13:39 GMT
##[error]Process completed with exit code 2.
##[group]Run echo "disk usage:"
echo "disk usage:"