indexing: reword help #146585

hkBst · 2025-09-15T11:37:25Z

After looking at #40850, I thought I'd try to improve wording around error E0608 a bit. Hopefully I've succeeded.

rustbot · 2025-09-15T11:37:28Z

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

rustbot · 2025-09-15T11:37:31Z

r? @fee1-dead

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compiler/rustc_error_codes/src/error_codes/E0608.md

fee1-dead · 2025-09-16T02:51:36Z

compiler/rustc_hir_typeck/src/expr.rs

-                        // fixed expression:
+                        err.help(
+                            "tuples are indexed (like structs) with dot (`._`) not with brackets (`[_]`), \
+                             element names are their positions: tuple = (tuple.0, tuple.1, ...)",


I feel like this line ("element names..") is a bit too extraneous. People trying to do x[0] might not really be very confused on which indices each field ends up (and it is probably better to leave this role to some other place teaching tuples)

I've removed this bit, and also the reference to structs.

@rustbot ready

jdonszelmann · 2025-09-18T07:43:36Z

tests/ui/issues/issue-27842.stderr

   |                ^^^
   |
-   = help: to access tuple elements, use tuple indexing syntax (e.g., `tuple.0`)
+   = help: tuples are indexed with dot (`._`): tuple = (tuple.0, tuple.1, ...)


I still don't think this message is better than the original. I like your changes to the error code docs, but the ._ confuses me and tuple = in the example too. I'd approve this if the error message and help stayed the same as it was.
Your changes to the case where you provide an integer as index is improved though, I like the "to access element 0, use .0" :)

@rustbot author

Thanks for reviewing!

I've made some small changes to address your comments. Let me know if it is any better!

@rustbot ready

The basic idea is to use the fact that a tuple is equal to its elements as a harness for the tuple index syntax...

well I get that that's what it's trying to convey, I just don't think it's any clearer than giving a single example like before

@rustbot author

again, I think your change to the message when providing an integer as index is good! I just really don't think this part is very clear while I think the way it was was perfectly clear

Alright I took out that idea, and now it's much closer to what was there before.

@rustbot ready

jdonszelmann

see above

View changes since this review

jdonszelmann · 2025-09-25T11:55:49Z

@hkBst I think this is a cool change, still feel like fixing it up?

hkBst · 2025-09-25T14:48:32Z

@jdonszelmann I'll get back to it in a bit. Just giving it some time, so I can look at it fresh. :)

jdonszelmann · 2025-09-25T16:47:55Z

Very good! No rush, just saw it in my review queue hehe

jdonszelmann · 2025-09-30T20:07:35Z

tests/ui/issues/issue-27842.stderr

   |
-   = help: to access tuple elements, use tuple indexing syntax (e.g., `tuple.0`)
+   = help: tuples are indexed with a dot and a constant index, e.g.: `tuple.0`


https://english.stackexchange.com/questions/16172/should-i-always-use-a-comma-after-e-g-or-i-e

last nit: @rustbot author

i.e. I prefer the comma

also it's not a constant. i.e. it can't be replaced by tuple.const{3 + 3} or whatever (though that'd be cool). Genuinely, it was pretty good as it was! like, it is tuple indexing syntax, that's fundamentally what it is, and in the compiler it acts much more like an identifier than a constant. For example, it's perfectly valid to initialize a tuple struct like this:

struct Foo(u32); fn main() { let x = Foo {0: 3} }

You're right that "constant" is perhaps not quite right. Perhaps "literal" or "literal integer"? Indexing a tuple may use "tuple indexing syntax", but that name does not seem to have much (any?) explanatory power, which is why I am trying to describe it instead of naming it.

My usage of "e.g.:" seems indeed to be unusual, but the colon can stand on its own I think.

Genuinely, it was pretty good as it was!

It is adequate, but I think we can do better. Perhaps "tuple elements are accessed" is better than "tuples are indexed" though?

I've pushed another version of this...

@rustbot ready

Co-authored-by: beef <[email protected]>

rustbot · 2025-10-01T07:39:49Z

This PR was rebased onto a different master 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.

jdonszelmann · 2025-10-01T20:48:27Z

@bors r+ rollup

bors · 2025-10-01T20:48:30Z

📌 Commit 86f2d42 has been approved by jdonszelmann

It is now in the queue for this repository.

indexing: reword help After looking at rust-lang#40850, I thought I'd try to improve wording around error E0608 a bit. Hopefully I've succeeded.

Rollup of 10 pull requests Successful merges: - #146281 (Support `#[rustc_align_static]` inside `thread_local!`) - #146535 (mbe: Implement `unsafe` attribute rules) - #146585 (indexing: reword help) - #147004 (Tweak handling of "struct like start" where a struct isn't supported) - #147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - #147225 (Don't enable shared memory by default with Wasm atomics) - #147227 (implement `Box::take`) - #147231 (Extending `#[rustc_force_inline]` to be applicable to inherent methods) - #147233 (Initialize llvm submodule if not already the case to run citool) - #147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

indexing: reword help After looking at rust-lang#40850, I thought I'd try to improve wording around error E0608 a bit. Hopefully I've succeeded.

Rollup of 9 pull requests Successful merges: - #146281 (Support `#[rustc_align_static]` inside `thread_local!`) - #146535 (mbe: Implement `unsafe` attribute rules) - #146585 (indexing: reword help) - #147004 (Tweak handling of "struct like start" where a struct isn't supported) - #147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - #147225 (Don't enable shared memory by default with Wasm atomics) - #147227 (implement `Box::take`) - #147233 (Initialize llvm submodule if not already the case to run citool) - #147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #146585 - hkBst:indexing-1, r=jdonszelmann indexing: reword help After looking at #40850, I thought I'd try to improve wording around error E0608 a bit. Hopefully I've succeeded.

Rollup of 9 pull requests Successful merges: - rust-lang/rust#146281 (Support `#[rustc_align_static]` inside `thread_local!`) - rust-lang/rust#146535 (mbe: Implement `unsafe` attribute rules) - rust-lang/rust#146585 (indexing: reword help) - rust-lang/rust#147004 (Tweak handling of "struct like start" where a struct isn't supported) - rust-lang/rust#147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - rust-lang/rust#147225 (Don't enable shared memory by default with Wasm atomics) - rust-lang/rust#147227 (implement `Box::take`) - rust-lang/rust#147233 (Initialize llvm submodule if not already the case to run citool) - rust-lang/rust#147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

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indexing: reword help

86f2d42

Co-authored-by: beef <[email protected]>

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indexing: reword help #146585

indexing: reword help #146585

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hkBst commented Sep 15, 2025

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jdonszelmann commented Sep 25, 2025

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