bjoernager/rust
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Rollup merge of #134979 - estebank:default-lint-sugg, r=compiler-errors

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Provide structured suggestion for `impl Default` of type where all fields have defaults

```
error: `Default` impl doesn't use the declared default field values
  --> $DIR/manual-default-impl-could-be-derived.rs:28:1
   |
LL | / impl Default for B {
LL | |     fn default() -> Self {
LL | |         B {
LL | |             x: s(),
   | |                --- this field has a default value
LL | |             y: 0,
   | |                - this field has a default value
...  |
LL | | }
   | |_^
   |
help: to avoid divergence in behavior between `Struct { .. }` and `<Struct as Default>::default()`, derive the `Default`
   |
LL ~ #[derive(Default)] struct B {
   |
```

Note that above the structured suggestion also includes completely removing the manual `impl`, but the rendering doesn't.
This commit is contained in:
Stuart Cook 2025-01-01 16:35:32 +11:00 • committed by GitHub
commit 65cb7c66d0
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2 changed files with 30 additions and 9 deletions
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34
compiler/rustc_lint/src/default_could_be_derived.rs
View file

@ -1,9 +1,11 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::Diag;
use rustc_errors::{Applicability, Diag};
use rustc_hir as hir;
use rustc_middle::ty;
use rustc_middle::ty::TyCtxt;
use rustc_session::{declare_lint, impl_lint_pass};
use rustc_span::Symbol;
use rustc_span::def_id::DefId;
use rustc_span::symbol::sym;
use crate::{LateContext, LateLintPass};
@ -149,13 +151,16 @@ impl<'tcx> LateLintPass<'tcx> for DefaultCouldBeDerived {
let hir_id = cx.tcx.local_def_id_to_hir_id(local);
let hir::Node::Item(item) = cx.tcx.hir_node(hir_id) else { return };
cx.tcx.node_span_lint(DEFAULT_OVERRIDES_DEFAULT_FIELDS, hir_id, item.span, |diag| {
mk_lint(diag, orig_fields, fields);
mk_lint(cx.tcx, diag, type_def_id, parent, orig_fields, fields);
});
}
}
fn mk_lint(
tcx: TyCtxt<'_>,
diag: &mut Diag<'_, ()>,
type_def_id: DefId,
impl_def_id: DefId,
orig_fields: FxHashMap<Symbol, &hir::FieldDef<'_>>,
fields: &[hir::ExprField<'_>],
) {
@ -175,11 +180,24 @@ fn mk_lint(
}
}
diag.help(if removed_all_fields {
"to avoid divergence in behavior between `Struct { .. }` and \
`<Struct as Default>::default()`, derive the `Default`"
if removed_all_fields {
let msg = "to avoid divergence in behavior between `Struct { .. }` and \
`<Struct as Default>::default()`, derive the `Default`";
if let Some(hir::Node::Item(impl_)) = tcx.hir().get_if_local(impl_def_id) {
diag.multipart_suggestion_verbose(
msg,
vec![
(tcx.def_span(type_def_id).shrink_to_lo(), "#[derive(Default)] ".to_string()),
(impl_.span, String::new()),
],
Applicability::MachineApplicable,
);
} else {
diag.help(msg);
}
} else {
"use the default values in the `impl` with `Struct { mandatory_field, .. }` to avoid them \
diverging over time"
});
let msg = "use the default values in the `impl` with `Struct { mandatory_field, .. }` to \
avoid them diverging over time";
diag.help(msg);
}
}