Add DesugaringKind::FormatLiteral by mejrs · Pull Request #142594 · rust-lang/rust

mejrs · 2025-06-16T19:31:55Z

Implements DesugaringKind::FormatLiteral to mark the FormatArgs desugaring of format literals. The main use for this is to stop yapping about about formatting parameters if we're not anywhere near a format literal. The other use case is to fix suggestions such as #141350. It might also be useful for new or existing diagnostics that check whether they're in a format-like macro.

cc @xizheyin @fmease

rustbot · 2025-06-16T19:31:59Z

r? @SparrowLii

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rustbot · 2025-06-16T19:32:01Z

Some changes occurred in compiler/rustc_ast_lowering/src/format.rs

cc @m-ou-se

fmease · 2025-06-16T19:33:43Z

We might want to block this on #140748, I'm relatively sure. Just FYI

mejrs · 2025-06-16T19:43:45Z

Why is that?

fmease · 2025-06-16T19:53:59Z

Idk, if it's not conflicting according to git and if it's not stepping on each other's toes in other ways, I guess it's fine — I only skimmed boths diffs. Mara's PR will likely get approved soon anyway.

xizheyin

Great, #141633 can be refactored after this.

compiler/rustc_span/src/hygiene.rs

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

compiler/rustc_ast/src/format.rs

SparrowLii

This is very meaningful and the impl looks fine. But adding a new desugaringKind for diagnostics needs some opinions IMO
r? diagnostics

chenyukang · 2025-06-20T00:32:09Z

tests/ui/on-unimplemented/no-debug.stderr

   |
 LL |     println!("{:?} {:?}", Foo, Bar);
-   |                                ^^^ `Bar` cannot be formatted using `{:?}` because it doesn't implement `Debug`
+   |                    ----        ^^^ `Bar` cannot be formatted using `{:?}` because it doesn't implement `Debug`


This change on diagnostic reminds me of this issue:
#140578

while we had a PR for it, but seems it's stalled.

Will this PR also resolve #140578? If so, we can link with it, add a unit test, and close that one too.

It doesn't, but it does make that PR easier to implement; they can simply replace all of the diagnostic item stuff with a matches!(span.desugaring_kind(), Some(rustc_span::DesugaringKind::FormatLiteral {..}))

tests/ui/rfcs/rfc-2361-dbg-macro/dbg-macro-requires-debug.stderr

chenyukang · 2025-06-20T00:35:46Z

tests/ui/suggestions/derive-macro-missing-bounds.stderr

   |              ----- in this derive macro expansion
 LL |     struct Outer<T>(Inner<T>);
-   |                     ^^^^^^^^ `a::Inner<T>` cannot be formatted using `{:?}`
+   |                     ^^^^^^^^ the trait `Debug` is not implemented for `a::Inner<T>`


I'm neutral about this change. Maybe some beginners need to know the relationship between Debug and {:?}. I am not sure about this.

chenyukang · 2025-06-20T00:41:46Z

Looks ok for me.

@bors delegate+

bors · 2025-06-20T00:41:49Z

✌️ @mejrs, you can now approve this pull request!

If @chenyukang told you to "r=me" after making some further change, please make that change, then do @bors r=@chenyukang

mejrs · 2025-06-21T22:21:30Z

@bors r=@chenyukang

bors · 2025-06-21T22:21:33Z

📌 Commit 3858b2c has been approved by chenyukang

It is now in the queue for this repository.

Add DesugaringKind::FormatLiteral Implements `DesugaringKind::FormatLiteral` to mark the FormatArgs desugaring of format literals. The main use for this is to stop yapping about about formatting parameters if we're not anywhere near a format literal. The other use case is to fix suggestions such as rust-lang#141350. It might also be useful for new or existing diagnostics that check whether they're in a format-like macro. cc `@xizheyin` `@fmease`

Rollup of 10 pull requests Successful merges: - #140254 (Pass -Cpanic=abort for the panic_abort crate) - #142594 (Add DesugaringKind::FormatLiteral) - #142600 (Port `#[rustc_pub_transparent]` to the new attribute system) - #142617 (improve search graph docs, reset `encountered_overflow` between reruns) - #142641 (Generate symbols.o for proc-macros too) - #142747 (rustdoc_json: conversion cleanups) - #142776 (All HIR attributes are outer) - #142800 (integer docs: remove extraneous text) - #142850 (remove asm_goto feature annotation, for it is now stabilized) - #142860 (Notify me on tidy changes) r? `@ghost` `@rustbot` modify labels: rollup

jhpratt · 2025-06-22T02:24:05Z

@bors r-

#142861 (comment)

mejrs · 2025-06-22T12:25:22Z

@bors r=@chenyukang

bors · 2025-06-22T12:25:24Z

📌 Commit 29ce695 has been approved by chenyukang

It is now in the queue for this repository.

Rollup of 10 pull requests Successful merges: - #142458 (Merge unboxed trait object error suggestion into regular dyn incompat error) - #142593 (Add a warning to LateContext::get_def_path) - #142594 (Add DesugaringKind::FormatLiteral) - #142740 (Clean-up `FnCtxt::is_destruct_assignment_desugaring`) - #142780 (Port `#[must_use]` to new attribute parsing infrastructure) - #142798 (Don't fail to parse a struct if a semicolon is used to separate fields) - #142856 (Add a few inline directives in rustc_serialize.) - #142868 (remove few allow(dead_code)) - #142874 (cranelift: fix target feature name typo: "fxsr") - #142877 (Document why tidy checks if `eslint` is installed via `npm`) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #142594 - mejrs:new_desugaring, r=chenyukang Add DesugaringKind::FormatLiteral Implements `DesugaringKind::FormatLiteral` to mark the FormatArgs desugaring of format literals. The main use for this is to stop yapping about about formatting parameters if we're not anywhere near a format literal. The other use case is to fix suggestions such as #141350. It might also be useful for new or existing diagnostics that check whether they're in a format-like macro. cc `@xizheyin` `@fmease`

xizheyin · 2025-06-29T09:53:56Z

I've found that #141350 can't be solved directly using PR, as the ast lowering phase comes after name resolving, and I'm now not quite sure where I should mark span using desugaring_kind. For example, I might need to add a visit_format_args somewhere. I'm trying to mark span when creating the format_args in rustc_builtin_macros, however some relevant context is missing, such as tcx, or untracked... Anyone have any suggestions?

Add DesugaringKind::FormatLiteral Implements `DesugaringKind::FormatLiteral` to mark the FormatArgs desugaring of format literals. The main use for this is to stop yapping about about formatting parameters if we're not anywhere near a format literal. The other use case is to fix suggestions such as rust-lang#141350. It might also be useful for new or existing diagnostics that check whether they're in a format-like macro. cc `@xizheyin` `@fmease`

Rollup of 10 pull requests Successful merges: - rust-lang/rust#142458 (Merge unboxed trait object error suggestion into regular dyn incompat error) - rust-lang/rust#142593 (Add a warning to LateContext::get_def_path) - rust-lang/rust#142594 (Add DesugaringKind::FormatLiteral) - rust-lang/rust#142740 (Clean-up `FnCtxt::is_destruct_assignment_desugaring`) - rust-lang/rust#142780 (Port `#[must_use]` to new attribute parsing infrastructure) - rust-lang/rust#142798 (Don't fail to parse a struct if a semicolon is used to separate fields) - rust-lang/rust#142856 (Add a few inline directives in rustc_serialize.) - rust-lang/rust#142868 (remove few allow(dead_code)) - rust-lang/rust#142874 (cranelift: fix target feature name typo: "fxsr") - rust-lang/rust#142877 (Document why tidy checks if `eslint` is installed via `npm`) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned SparrowLii Jun 16, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 16, 2025

xizheyin reviewed Jun 17, 2025

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m-ou-se reviewed Jun 17, 2025

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mejrs force-pushed the new_desugaring branch 2 times, most recently from 0cd0b91 to 3858b2c Compare June 17, 2025 17:37

SparrowLii reviewed Jun 18, 2025

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bors 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 Jun 21, 2025

mejrs mentioned this pull request Jun 21, 2025

Fix unuseful span in type error in some format_args!() invocations #140916

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jhpratt mentioned this pull request Jun 22, 2025

Rollup of 10 pull requests #142861

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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 22, 2025

mejrs force-pushed the new_desugaring branch from 3858b2c to 1c5f423 Compare June 22, 2025 08:47

mejrs added 2 commits June 22, 2025 10:58

Implement DesugaringKind::FormatLiteral

b1d1812

Stop dbg! macro yapping about format modifiers

29ce695

mejrs force-pushed the new_desugaring branch from 1c5f423 to 29ce695 Compare June 22, 2025 09:04

bors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 22, 2025

GuillaumeGomez mentioned this pull request Jun 22, 2025

Rollup of 10 pull requests #142878

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bors merged commit 7bed341 into rust-lang:master Jun 22, 2025
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rustbot added this to the 1.89.0 milestone Jun 22, 2025

apiraino mentioned this pull request Oct 9, 2025

Suggest to bind self.x to x when field x may be in format string #141633

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