Implement complex numbers and basic arithmetic

[scimind2460]

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Related to #154023
This PR adds complex numbers as a lang item behind a libs feature gate and adds simple implementations for arithmetic.

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Some changes occurred in src/tools/cargo

cc @ehuss

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[tgross35]

I'd recommend that the first PR only add Complex and do the compiler ABI portion. Do math in a followup.

A test in tests/codegen-llvm is needed for sure, also in tests/assembly-llvm would be ideal.

Or only do addition+subtraction first, add compiler support later

[scimind2460]

Or only do addition+subtraction first, add compiler support later

I'll do that. I'm not entirely sure how to add support for calling conventions that exactly match up with _Complex.

[bjorn3]

You can probably make it a lang item and check for it in the target specific call conv impls of rustc_target::callconv and handle it as necessary. Also make sure to annotate it with #[repr(C)] to ensure the correct memory layout. And finally is it intentional that Complex accepts arbitrary types rather than just float types? Presumably there is no standard ABI for non-float types here.

[scimind2460]

You can probably make it a lang item and check for it in the target specific call conv impls of rustc_target::callconv and handle it as necessary. Also make sure to annotate it with #[repr(C)] to ensure the correct memory layout. And finally is it intentional that Complex accepts arbitrary types rather than just float types? Presumably there is no standard ABI for non-float types here.

Thanks for the tip @bjorn3! I was planning to go with the lang item approach and #[repr(c)]. It is intentional as AFAIK libs didn't want the overhead of a full trait, and I'm not sure how we could implement it for non-float types.

[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.

[rustbot]

⚠️ Warning ⚠️

• The following commits have merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

  • 480619f

  You can start a rebase with the following commands:

  $ # rebase
  $ git pull --rebase https://github.com/rust-lang/rust.git main
  $ git push --force-with-lease
  

[rust-log-analyzer]

The job aarch64-gnu-llvm-21-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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

+ /scripts/stage_2_test_set2.sh
+ '[' 1 == 1 ']'
+ echo 'PR_CI_JOB set; skipping tidy'
PR_CI_JOB set; skipping tidy
+ SKIP_TIDY='--skip tidy'
+ ../x.py --stage 2 test --skip tidy --skip tests --skip coverage-map --skip coverage-run --skip library --skip tidyselftest
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.04s
##[endgroup]
downloading https://static.rust-lang.org/dist/2026-03-05/rustfmt-nightly-aarch64-unknown-linux-gnu.tar.xz
---
[RUSTC-TIMING] corebenches test:true 9.390
[RUSTC-TIMING] alloctests test:true 18.611
[RUSTC-TIMING] alloctests test:true 18.422
[RUSTC-TIMING] coretests test:true 66.620
error: could not compile `coretests` (test "coretests") due to 2 previous errors
env -u RUSTC_WRAPPER CARGO_ENCODED_RUSTDOCFLAGS="-Csymbol-mangling-version=v0\u{1f}-Zannotate-moves\u{1f}-Zrandomize-layout\u{1f}-Zunstable-options\u{1f}--check-cfg=cfg(bootstrap)\u{1f}-Wrustdoc::invalid_codeblock_attributes\u{1f}--crate-version\u{1f}1.96.0-nightly\t(6b29b849c\t2026-03-22)" CARGO_ENCODED_RUSTFLAGS="-Csymbol-mangling-version=v0\u{1f}-Zannotate-moves\u{1f}-Zrandomize-layout\u{1f}-Zunstable-options\u{1f}--check-cfg=cfg(bootstrap)\u{1f}-Zmacro-backtrace\u{1f}-Csplit-debuginfo=off\u{1f}-Clink-arg=-L/usr/lib/llvm-21/lib\u{1f}-Cllvm-args=-import-instr-limit=10\u{1f}-Clink-args=-Wl,-z,origin\u{1f}-Clink-args=-Wl,-rpath,$ORIGIN/../lib\u{1f}--cap-lints=allow\u{1f}--cfg\u{1f}randomized_layouts" RUSTC="/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/dist/rustc-clif" RUSTDOC="/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/dist/rustdoc-clif" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage0/bin/cargo" "test" "--manifest-path" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/build/sysroot_tests/Cargo.toml" "--target-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/build/sysroot_tests_target" "--locked" "--target" "aarch64-unknown-linux-gnu" "-p" "coretests" "-p" "alloctests" "--tests" "--" "-q" exited with status ExitStatus(unix_wait_status(25856))
Command `/checkout/obj/build/aarch64-unknown-linux-gnu/stage0/bin/cargo run -Zwarnings --target aarch64-unknown-linux-gnu -Zbinary-dep-depinfo -j 4 -Zroot-dir=/checkout --locked --color=always --profile=release --manifest-path /checkout/compiler/rustc_codegen_cranelift/build_system/Cargo.toml -- test --download-dir /checkout/obj/build/cg_clif_download --out-dir /checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif --no-unstable-features --use-backend cranelift --sysroot llvm --skip-test testsuite.extended_sysroot [workdir=/checkout/compiler/rustc_codegen_cranelift]` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/test.rs:3909:25
Executed at: src/bootstrap/src/core/build_steps/test.rs:3954:26

--- BACKTRACE vvv
   0: std::backtrace_rs::backtrace::libunwind::trace
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1: std::backtrace_rs::backtrace::trace_unsynchronized::<<std::backtrace::Backtrace>::create::{closure#0}>
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2: <std::backtrace::Backtrace>::create
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/backtrace.rs:331:13
   3: <bootstrap::utils::exec::DeferredCommand>::finish_process
             at /checkout/src/bootstrap/src/utils/exec.rs:939:17
   4: <bootstrap::utils::exec::DeferredCommand>::wait_for_output::<&bootstrap::utils::exec::ExecutionContext>
             at /checkout/src/bootstrap/src/utils/exec.rs:831:21
   5: <bootstrap::utils::exec::ExecutionContext>::run
             at /checkout/src/bootstrap/src/utils/exec.rs:741:45
   6: <bootstrap::utils::exec::BootstrapCommand>::run::<&bootstrap::core::builder::Builder>
             at /checkout/src/bootstrap/src/utils/exec.rs:339:27
   7: <bootstrap::core::build_steps::test::CodegenCranelift as bootstrap::core::builder::Step>::run
             at /checkout/src/bootstrap/src/core/build_steps/test.rs:3954:26
   8: <bootstrap::core::builder::Builder>::ensure::<bootstrap::core::build_steps::test::CodegenCranelift>
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1579:36
   9: <bootstrap::core::build_steps::test::CodegenCranelift as bootstrap::core::builder::Step>::make_run
             at /checkout/src/bootstrap/src/core/build_steps/test.rs:3895:17
  10: <bootstrap::core::builder::StepDescription>::maybe_run
             at /checkout/src/bootstrap/src/core/builder/mod.rs:476:13
  11: bootstrap::core::builder::cli_paths::match_paths_to_steps_and_run
             at /checkout/src/bootstrap/src/core/builder/cli_paths.rs:141:22
  12: <bootstrap::core::builder::Builder>::run_step_descriptions
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1122:9
  13: <bootstrap::core::builder::Builder>::execute_cli
             at /checkout/src/bootstrap/src/core/builder/mod.rs:1101:14
  14: <bootstrap::Build>::build
             at /checkout/src/bootstrap/src/lib.rs:799:25
  15: bootstrap::main
             at /checkout/src/bootstrap/src/bin/main.rs:130:11
  16: <fn() as core::ops::function::FnOnce<()>>::call_once
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/core/src/ops/function.rs:250:5
  17: std::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()>
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/sys/backtrace.rs:166:18
  18: std::rt::lang_start::<()>::{closure#0}
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/rt.rs:206:18
  19: <&dyn core::ops::function::Fn<(), Output = i32> + core::panic::unwind_safe::RefUnwindSafe + core::marker::Sync as core::ops::function::FnOnce<()>>::call_once
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/core/src/ops/function.rs:287:21
  20: std::panicking::catch_unwind::do_call::<&dyn core::ops::function::Fn<(), Output = i32> + core::panic::unwind_safe::RefUnwindSafe + core::marker::Sync, i32>
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/panicking.rs:581:40
  21: std::panicking::catch_unwind::<i32, &dyn core::ops::function::Fn<(), Output = i32> + core::panic::unwind_safe::RefUnwindSafe + core::marker::Sync>
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/panicking.rs:544:19
  22: std::panic::catch_unwind::<&dyn core::ops::function::Fn<(), Output = i32> + core::panic::unwind_safe::RefUnwindSafe + core::marker::Sync, i32>
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/panic.rs:359:14
  23: std::rt::lang_start_internal::{closure#0}
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/rt.rs:175:24
  24: std::panicking::catch_unwind::do_call::<std::rt::lang_start_internal::{closure#0}, isize>
             at /rustc/ad726b5063362ec9897ef3d67452fc5606ee70fa/library/std/src/panicking.rs:581:40
---
  31: __libc_start_main
  32: _start


Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `--stage 2 test --skip tidy --skip tests --skip coverage-map --skip coverage-run --skip library --skip tidyselftest`
Build completed unsuccessfully in 0:21:02
  local time: Sun Mar 22 13:08:53 UTC 2026
  network time: Sun, 22 Mar 2026 13:08:54 GMT
##[error]Process completed with exit code 1.

[tgross35]

Two small things and please squash (i.e. rebase rather than merge from main), think this should be good after that

View changes since this review

[tgross35]

Suggested change

	/// The complex number type in Cartesian form.
	/// Supports simple addition and subtraction.
	/// ```
	/// The complex number type in Cartesian form.
	///
	/// ```

In the future it will support more :) Also note that consecutive doc lines without a blank line get turned into a single paragraph.

[tgross35]

You need to actually import crate::num::float_test (CI failure)

[GrigorenkoPV]

Not sure if this was discussed before, but maybe

Suggested change

	#[derive(Debug, PartialEq)]
	#[derive(Clone, Copy, Debug, PartialEq)]

?

[GrigorenkoPV]

Not sure if this was discussed before, but maybe

Suggested change

	pub fn new(re: T, im: T) -> Self {
	#[must_use]
	pub const fn new(re: T, im: T) -> Self {

?

[tgross35]

Need some git help if it's the same as #154656?