When compiling without a specified `--edition`, emit a note by estebank · Pull Request #158102 · rust-lang/rust

estebank · 2026-06-18T20:28:57Z

estebank · 2026-06-18T20:39:23Z

I'll try to write an MCP later (unless someone does it for me). This change was motivated after seeing https://internals.rust-lang.org/t/code-compiles-on-playground-but-fails-when-passed-via-stdin-to-rustc/24393 where the different defaults between cargo, playground and rustc caused people to get confused.

rustbot · 2026-07-21T02:25:26Z

Some changes occurred in src/tools/compiletest

cc @jieyouxu

rustbot · 2026-07-21T02:25:29Z

r? @jieyouxu

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jieyouxu

Thanks
@bors r+ rollup

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jieyouxu · 2026-08-04T01:02:33Z


 fn main() {
-    rustc().input("foo-prev.rs").run();
+    rustc().edition("2015").input("foo-prev.rs").run();


Remark: we could consider default setting edition but allow overriding, but explicit is fine

rust-bors · 2026-08-04T01:05:18Z

📌 Commit a1d6de2 has been approved by jieyouxu

It is now in the queue for this repository.

jieyouxu

Thanks, re. the run-make-cargo test. You can r=me after fixing it or just dropping it, I realize it doesn't add much if a successful run hides the note anyway.

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Use same wording as cargo does when `package.edition` is unspecified. Do not suggest `--edition=future` on stable.

estebank · 2026-09-20T04:18:38Z

+    /// We should not be emitting notes during compiles, with the *only* exception of missing
+    /// `--edition` when calling `rustc` directly.
+    pub fn early_note_for_missing_crate_edition(&self, msg: impl Into<DiagMessage>) {
+        self.dcx.handle().note(msg)
+    }


Heads up @nnethercote, who's been removing weird diagnostics APIs. I'm re-adding this because the complaing about --edition not being set for rustc must be a note. Let me know if there's an alternative to doing this that I should pursue instead. We might want to just use eprintln!() instead 🤔

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Or a warning?

More generally, what exactly is a note? I see it as some additional information about a top-level error or warning, which is why it makes sense as a subdiagnostic but not as a top-level diagnostic.

I generally agree, it's just that this case in particular we want to provide feedback to users but not make it seem like it is a bug of some kind (which is what both errors and warnings communicate). Regardless, I think that using eprintln for this makes sense. We don't need a header for the message, we don't want colors in it. It just has to be somewhere visible for a naïve use of rustc.

This is a case where it's not an error, but also probably doesn't do what you expect. That seems to me like a good fit for a warning.

Won't eprintln! then also mix into --message-format=json output¹? I guess cargo / dev tools already parse json lines so this might not be a problem? I'm also fine with either a note or a warning, both seem sensible.

Footnotes

In unrelated note, we currently paper over rustc eprintln! issues re. failing to write out stderr, like broken pipes, with -Zon-broken-pipe=kill ↩

@jieyouxu just tested and cargo swallows the eprintln (as expected) the same way as the note.

@nnethercote I know what you mean, but I'm trying to navigate making this something very lightweight. It's not only a semantic/technical issue, this will be visible to a lot of people and the more annoying we make it (which having bright yellow on every compile would accomplish for some) the more likely it is people will come in my general direction with pitchforks :)

estebank · 2026-09-20T17:54:20Z

@bors r=jieyouxu

I'll merge with the eprintln approach, and we can iterate on it afterwards.

rust-bors · 2026-09-20T17:54:23Z

📌 Commit 2784d28 has been approved by jieyouxu

It is now in the queue for this repository.

…ieyouxu When compiling without a specified `--edition`, emit a note Implement rust-lang/compiler-team#1019.

Rollup of 15 pull requests Successful merges: - #161051 (When error from local macro, include macro def span) - #162750 (add case mapping fast paths for Latin-1) - #162831 (Do not continue past `rustc_resolve` when encountering duplicated items) - #162835 (rustdoc: account for nested parens and split text events in bare urls lint) - #163044 (Report runtime range endpoints for runtime values) - #163062 (Use x30 register name with LLVM 23+) - #158102 (When compiling without a specified `--edition`, emit a note) - #162984 (Windows: don't error if `access_mode` is set on `OpenOptions`) - #163005 (Avoid unreachable integer underflow check in `CStr::count_bytes()`) - #163019 (Prepare for the introduction of forced keywords (`k#`)) - #163020 (Dir: fix fallback impl for remove_dir) - #163047 (Use verbose suggestion for `mut binding` instead of `&mut binding`) - #163075 (Fix ArgAttributes mismatches in ABI UI tests for LoongArch64 and RiscV64) - #163079 (enable `f128` from `u64`/`i64` test) - #163082 (Remove `TypeChecker::root_cx`)

…ieyouxu When compiling without a specified `--edition`, emit a note Implement rust-lang/compiler-team#1019.

Zalathar · 2026-09-21T06:44:22Z

Checking whether this caused a weird failure in rollup: #163086 (comment)

@bors try jobs=test-x86_64-gnu-aux

When compiling without a specified `--edition`, emit a note try-job: test-x86_64-gnu-aux

rust-bors · 2026-09-21T07:32:29Z

💔 Test for a8946ca failed: CI. Failed job:

try - test-x86_64-gnu-aux (web logs, enhanced plaintext logs)

rust-log-analyzer · 2026-09-21T07:32:32Z

The job test-x86_64-gnu-aux failed! Check out the build log: (web) (plain enhanced) (plain)

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

jieyouxu · 2026-09-21T07:36:35Z

Huh?

…uwer Rollup of 18 pull requests Successful merges: - #161051 (When error from local macro, include macro def span) - #161629 (Streamline `StateDiffCollector`) - #162750 (add case mapping fast paths for Latin-1) - #162831 (Do not continue past `rustc_resolve` when encountering duplicated items) - #162835 (rustdoc: account for nested parens and split text events in bare urls lint) - #162952 (Depend on lockfiles to prevent GC of the current session) - #163044 (Report runtime range endpoints for runtime values) - #163062 (Use x30 register name with LLVM 23+) - #158102 (When compiling without a specified `--edition`, emit a note) - #162939 (Declare multi-kind constants for MacroKinds) - #162984 (Windows: don't error if `access_mode` is set on `OpenOptions`) - #163005 (Avoid unreachable integer underflow check in `CStr::count_bytes()`) - #163019 (Prepare for the introduction of forced keywords (`k#`)) - #163020 (Dir: fix fallback impl for remove_dir) - #163047 (Use verbose suggestion for `mut binding` instead of `&mut binding`) - #163075 (Fix ArgAttributes mismatches in ABI UI tests for LoongArch64 and RiscV64) - #163079 (enable `f128` from `u64`/`i64` test) - #163082 (Remove `TypeChecker::root_cx`)

JonathanBrouwer · 2026-09-21T08:13:43Z

@bors r-

rust-bors · 2026-09-21T08:15:32Z

This pull request was unapproved.

This PR was contained in the following rollups:

Rollup of 15 pull requests #163086 was unapproved
Rollup of 18 pull requests #163089 was unapproved

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estebank force-pushed the note-default-edition branch from b923a75 to 2a486d3 Compare June 18, 2026 20:41

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estebank force-pushed the note-default-edition branch from 4241536 to d71c2fa Compare July 21, 2026 02:17

estebank mentioned this pull request Jul 21, 2026

Emit note when calling rustc without specifying an edition rust-lang/compiler-team#1019

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estebank force-pushed the note-default-edition branch from d71c2fa to a1d6de2 Compare July 27, 2026 06:56

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estebank force-pushed the note-default-edition branch from fb94f61 to b4c367e Compare September 20, 2026 04:05

When compiling without a specified --edition, emit a note

5c0fee6

Use same wording as cargo does when `package.edition` is unspecified. Do not suggest `--edition=future` on stable.

estebank force-pushed the note-default-edition branch from b4c367e to 5c0fee6 Compare September 20, 2026 04:15

estebank commented Sep 20, 2026

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Use eprintln!() instead of a note for unspecified --edition

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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 Sep 20, 2026

Zalathar added a commit to Zalathar/rust that referenced this pull request Sep 21, 2026

Rollup merge of rust-lang#158102 - estebank:note-default-edition, r=j…

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…ieyouxu When compiling without a specified `--edition`, emit a note Implement rust-lang/compiler-team#1019.

Zalathar mentioned this pull request Sep 21, 2026

Rollup of 15 pull requests #163086

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Rollup merge of rust-lang#158102 - estebank:note-default-edition, r=j…

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…ieyouxu When compiling without a specified `--edition`, emit a note Implement rust-lang/compiler-team#1019.

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Rollup of 18 pull requests #163089

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Auto merge of #158102 - estebank:note-default-edition, r=<try>

a8946ca

When compiling without a specified `--edition`, emit a note try-job: test-x86_64-gnu-aux

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