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declare_tool_lint: allow use without default_field_values feature #164990

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declare_tool_lint: allow use without default_field_values feature #164990

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4 changes: 3 additions & 1 deletion compiler/rustc_hir_typeck/src/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2053,7 +2053,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}
}
if !self.tcx.features().default_field_values() {
if !(self.tcx.features().default_field_values()
|| span.allows_unstable(sym::default_field_values))
{
Comment on lines +2056 to +2058

@tiif tiif Nov 1, 2026

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The idea that I get from this diff is whenever we use #[allow_internal_unstable(default_field_values)]], we always execute the if path below that suggests adding #![feature(default_field_values)]? I feel I am missing something 🤔

let sugg = self.tcx.crate_level_attribute_injection_span();
self.dcx().emit_err(BaseExpressionDoubleDot {
span: span.shrink_to_hi(),
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3 changes: 3 additions & 0 deletions compiler/rustc_lint_defs/src/lib.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
// tidy-alphabetical-start
#![allow(internal_features)]
#![feature(allow_internal_unstable)]
#![feature(default_field_values)]
// tidy-alphabetical-end

Expand Down Expand Up @@ -698,6 +700,7 @@ macro_rules! declare_lint {
}

#[macro_export]
#[allow_internal_unstable(default_field_values)]
macro_rules! declare_tool_lint {
(
$(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level: ident, $desc: expr
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12 changes: 12 additions & 0 deletions tests/ui/structs/default-field-values/allow_internal_unstable.rs
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@tiif tiif Nov 1, 2026

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You will need to write a cross-crate test to test the behavior of using #[allow_internal_unstable(..)] across upstream and downstream crates.

In tests/ui/structs/default-field-values/auxiliary/, you can define the upstream crate, for example aux.rs with something like...

#![feature(default_field_values)]
#![feature(allow_internal_unstable)]
#[allow_internal_unstable(default_field_values)]
#[macro_export]
macro_rules! foo {
    () => { fn foo() { struct Foo {x: usize = 0, } Foo {..}; } };
}

In tests/ui/structs/default-field-values/allow_internal_unstable.rs, you can use the macro with...

//@ aux-build:aux.rs
//@check-pass

extern crate aux;
use aux::foo;

foo!();

fn main(){

You will see different behavior in downstream crate when allow_internal_unstable is used and when it is not used.

Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
//@check-pass

#![allow(internal_features)]
#![feature(allow_internal_unstable)]
#[allow_internal_unstable(default_field_values)]
macro_rules! foo {
() => { fn foo() { struct Foo {x: usize = 0, } Foo {..}; } };
}

foo!();

fn main(){}
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