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Rollup merge of #136577 - dianne:simple-pat-migration-simplification, r=Nadrieril

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Pattern Migration 2024: try to suggest eliding redundant binding modifiers

This is based on #136475. Only the last commit is new.

This is a simpler, more restrictive alternative to #136496, meant to partially address #136047. If a pattern can be migrated to Rust 2024 solely by removing redundant binding modifiers, this will make that suggestion; otherwise, it uses the old suggestion of making the pattern fully explicit.

Relevant tracking issue: #131414

``@rustbot`` label A-diagnostics A-patterns A-edition-2024

r? ``@Nadrieril``
This commit is contained in:
Matthias Krüger 2025-02-07 18:26:27 +01:00 • committed by GitHub
commit 20f9e973d9
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15 changed files with 1043 additions and 262 deletions
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11
compiler/rustc_mir_build/messages.ftl
View file

@ -285,7 +285,16 @@ mir_build_pointer_pattern = function pointers and raw pointers not derived from
mir_build_privately_uninhabited = pattern `{$witness_1}` is currently uninhabited, but this variant contains private fields which may become inhabited in the future
mir_build_rust_2024_incompatible_pat = this pattern relies on behavior which may change in edition 2024
mir_build_rust_2024_incompatible_pat = {$bad_modifiers ->
*[true] binding modifiers{$bad_ref_pats ->
*[true] {" "}and reference patterns
[false] {""}
}
[false] reference patterns
} may only be written when the default binding mode is `move`{$is_hard_error ->
*[true] {""}
[false] {" "}in Rust 2024
}
mir_build_static_in_pattern = statics cannot be referenced in patterns
.label = can't be used in patterns

60
compiler/rustc_mir_build/src/errors.rs
View file

@ -1,3 +1,4 @@
use rustc_data_structures::fx::FxIndexMap;
use rustc_errors::codes::*;
use rustc_errors::{
Applicability, Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level,
@ -1097,41 +1098,70 @@ pub(crate) enum MiscPatternSuggestion {
#[derive(LintDiagnostic)]
#[diag(mir_build_rust_2024_incompatible_pat)]
pub(crate) struct Rust2024IncompatiblePat<'a> {
pub(crate) struct Rust2024IncompatiblePat {
#[subdiagnostic]
pub(crate) sugg: Rust2024IncompatiblePatSugg<'a>,
pub(crate) sugg: Rust2024IncompatiblePatSugg,
pub(crate) bad_modifiers: bool,
pub(crate) bad_ref_pats: bool,
pub(crate) is_hard_error: bool,
}
pub(crate) struct Rust2024IncompatiblePatSugg<'a> {
pub(crate) struct Rust2024IncompatiblePatSugg {
/// If true, our suggestion is to elide explicit binding modifiers.
/// If false, our suggestion is to make the pattern fully explicit.
pub(crate) suggest_eliding_modes: bool,
pub(crate) suggestion: Vec<(Span, String)>,
pub(crate) ref_pattern_count: usize,
pub(crate) binding_mode_count: usize,
/// Labeled spans for subpatterns invalid in Rust 2024.
pub(crate) labels: &'a [(Span, String)],
/// Internal state: the ref-mutability of the default binding mode at the subpattern being
/// lowered, with the span where it was introduced. `None` for a by-value default mode.
pub(crate) default_mode_span: Option<(Span, ty::Mutability)>,
/// Labels for where incompatibility-causing by-ref default binding modes were introduced.
pub(crate) default_mode_labels: FxIndexMap<Span, ty::Mutability>,
}
impl<'a> Subdiagnostic for Rust2024IncompatiblePatSugg<'a> {
impl Subdiagnostic for Rust2024IncompatiblePatSugg {
fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
self,
diag: &mut Diag<'_, G>,
_f: &F,
) {
// Format and emit explanatory notes about default binding modes. Reversing the spans' order
// means if we have nested spans, the innermost ones will be visited first.
for (span, def_br_mutbl) in self.default_mode_labels.into_iter().rev() {
// Don't point to a macro call site.
if !span.from_expansion() {
let note_msg = "matching on a reference type with a non-reference pattern changes the default binding mode";
let label_msg =
format!("this matches on type `{}_`", def_br_mutbl.ref_prefix_str());
let mut label = MultiSpan::from(span);
label.push_span_label(span, label_msg);
diag.span_note(label, note_msg);
}
}
// Format and emit the suggestion.
let applicability =
if self.suggestion.iter().all(|(span, _)| span.can_be_used_for_suggestions()) {
Applicability::MachineApplicable
} else {
Applicability::MaybeIncorrect
};
let plural_derefs = pluralize!(self.ref_pattern_count);
let and_modes = if self.binding_mode_count > 0 {
format!(" and variable binding mode{}", pluralize!(self.binding_mode_count))
let msg = if self.suggest_eliding_modes {
let plural_modes = pluralize!(self.binding_mode_count);
format!("remove the unnecessary binding modifier{plural_modes}")
} else {
String::new()
let plural_derefs = pluralize!(self.ref_pattern_count);
let and_modes = if self.binding_mode_count > 0 {
format!(" and variable binding mode{}", pluralize!(self.binding_mode_count))
} else {
String::new()
};
format!("make the implied reference pattern{plural_derefs}{and_modes} explicit")
};
diag.multipart_suggestion_verbose(
format!("make the implied reference pattern{plural_derefs}{and_modes} explicit"),
self.suggestion,
applicability,
);
// FIXME(dianne): for peace of mind, don't risk emitting a 0-part suggestion (that panics!)
if !self.suggestion.is_empty() {
diag.multipart_suggestion_verbose(msg, self.suggestion, applicability);
}
}
}

146
compiler/rustc_mir_build/src/thir/pattern/mod.rs
View file

@ -35,7 +35,7 @@ struct PatCtxt<'a, 'tcx> {
typeck_results: &'a ty::TypeckResults<'tcx>,
/// Used by the Rust 2024 migration lint.
rust_2024_migration_suggestion: Option<Rust2024IncompatiblePatSugg<'a>>,
rust_2024_migration_suggestion: Option<Rust2024IncompatiblePatSugg>,
}
pub(super) fn pat_from_hir<'a, 'tcx>(
@ -44,25 +44,30 @@ pub(super) fn pat_from_hir<'a, 'tcx>(
typeck_results: &'a ty::TypeckResults<'tcx>,
pat: &'tcx hir::Pat<'tcx>,
) -> Box<Pat<'tcx>> {
let migration_info = typeck_results.rust_2024_migration_desugared_pats().get(pat.hir_id);
let mut pcx = PatCtxt {
tcx,
typing_env,
typeck_results,
rust_2024_migration_suggestion: typeck_results
.rust_2024_migration_desugared_pats()
.get(pat.hir_id)
.map(|labels| Rust2024IncompatiblePatSugg {
rust_2024_migration_suggestion: migration_info.and_then(|info| {
Some(Rust2024IncompatiblePatSugg {
suggest_eliding_modes: info.suggest_eliding_modes,
suggestion: Vec::new(),
ref_pattern_count: 0,
binding_mode_count: 0,
labels: labels.as_slice(),
}),
default_mode_span: None,
default_mode_labels: Default::default(),
})
}),
};
let result = pcx.lower_pattern(pat);
debug!("pat_from_hir({:?}) = {:?}", pat, result);
if let Some(sugg) = pcx.rust_2024_migration_suggestion {
let mut spans = MultiSpan::from_spans(sugg.labels.iter().map(|(span, _)| *span).collect());
for (span, label) in sugg.labels {
if let Some(info) = migration_info
&& let Some(sugg) = pcx.rust_2024_migration_suggestion
{
let mut spans =
MultiSpan::from_spans(info.primary_labels.iter().map(|(span, _)| *span).collect());
for (span, label) in &info.primary_labels {
spans.push_span_label(*span, label.clone());
}
// If a relevant span is from at least edition 2024, this is a hard error.
@ -70,10 +75,13 @@ pub(super) fn pat_from_hir<'a, 'tcx>(
if is_hard_error {
let mut err =
tcx.dcx().struct_span_err(spans, fluent::mir_build_rust_2024_incompatible_pat);
if let Some(info) = lint::builtin::RUST_2024_INCOMPATIBLE_PAT.future_incompatible {
if let Some(lint_info) = lint::builtin::RUST_2024_INCOMPATIBLE_PAT.future_incompatible {
// provide the same reference link as the lint
err.note(format!("for more information, see {}", info.reference));
err.note(format!("for more information, see {}", lint_info.reference));
}
err.arg("bad_modifiers", info.bad_modifiers);
err.arg("bad_ref_pats", info.bad_ref_pats);
err.arg("is_hard_error", true);
err.subdiagnostic(sugg);
err.emit();
} else {
@ -81,7 +89,12 @@ pub(super) fn pat_from_hir<'a, 'tcx>(
lint::builtin::RUST_2024_INCOMPATIBLE_PAT,
pat.hir_id,
spans,
Rust2024IncompatiblePat { sugg },
Rust2024IncompatiblePat {
sugg,
bad_modifiers: info.bad_modifiers,
bad_ref_pats: info.bad_ref_pats,
is_hard_error,
},
);
}
}
@ -90,6 +103,35 @@ pub(super) fn pat_from_hir<'a, 'tcx>(
impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
fn lower_pattern(&mut self, pat: &'tcx hir::Pat<'tcx>) -> Box<Pat<'tcx>> {
let adjustments: &[Ty<'tcx>] =
self.typeck_results.pat_adjustments().get(pat.hir_id).map_or(&[], |v| &**v);
let mut opt_old_mode_span = None;
if let Some(s) = &mut self.rust_2024_migration_suggestion
&& !adjustments.is_empty()
{
let implicit_deref_mutbls = adjustments.iter().map(|ref_ty| {
let &ty::Ref(_, _, mutbl) = ref_ty.kind() else {
span_bug!(pat.span, "pattern implicitly dereferences a non-ref type");
};
mutbl
});
if !s.suggest_eliding_modes {
let suggestion_str: String =
implicit_deref_mutbls.clone().map(|mutbl| mutbl.ref_prefix_str()).collect();
s.suggestion.push((pat.span.shrink_to_lo(), suggestion_str));
s.ref_pattern_count += adjustments.len();
}
// Remember if this changed the default binding mode, in case we want to label it.
let min_mutbl = implicit_deref_mutbls.min().unwrap();
if s.default_mode_span.is_none_or(|(_, old_mutbl)| min_mutbl < old_mutbl) {
opt_old_mode_span = Some(s.default_mode_span);
s.default_mode_span = Some((pat.span, min_mutbl));
}
};
// When implicit dereferences have been inserted in this pattern, the unadjusted lowered
// pattern has the type that results *after* dereferencing. For example, in this code:
//
@ -118,8 +160,6 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
_ => self.lower_pattern_unadjusted(pat),
};
let adjustments: &[Ty<'tcx>] =
self.typeck_results.pat_adjustments().get(pat.hir_id).map_or(&[], |v| &**v);
let adjusted_pat = adjustments.iter().rev().fold(unadjusted_pat, |thir_pat, ref_ty| {
debug!("{:?}: wrapping pattern with type {:?}", thir_pat, ref_ty);
Box::new(Pat {
@ -130,24 +170,10 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
});
if let Some(s) = &mut self.rust_2024_migration_suggestion
&& !adjustments.is_empty()
&& let Some(old_mode_span) = opt_old_mode_span
{
let suggestion_str: String = adjustments
.iter()
.map(|ref_ty| {
let &ty::Ref(_, _, mutbl) = ref_ty.kind() else {
span_bug!(pat.span, "pattern implicitly dereferences a non-ref type");
};
match mutbl {
ty::Mutability::Not => "&",
ty::Mutability::Mut => "&mut ",
}
})
.collect();
s.suggestion.push((pat.span.shrink_to_lo(), suggestion_str));
s.ref_pattern_count += adjustments.len();
};
s.default_mode_span = old_mode_span;
}
adjusted_pat
}
@ -340,7 +366,22 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
let mutability = if mutable { hir::Mutability::Mut } else { hir::Mutability::Not };
PatKind::DerefPattern { subpattern: self.lower_pattern(subpattern), mutability }
}
hir::PatKind::Ref(subpattern, _) | hir::PatKind::Box(subpattern) => {
hir::PatKind::Ref(subpattern, _) => {
// Track the default binding mode for the Rust 2024 migration suggestion.
let old_mode_span = self.rust_2024_migration_suggestion.as_mut().and_then(|s| {
if let Some((default_mode_span, default_ref_mutbl)) = s.default_mode_span {
// If this eats a by-ref default binding mode, label the binding mode.
s.default_mode_labels.insert(default_mode_span, default_ref_mutbl);
}
s.default_mode_span.take()
});
let subpattern = self.lower_pattern(subpattern);
if let Some(s) = &mut self.rust_2024_migration_suggestion {
s.default_mode_span = old_mode_span;
}
PatKind::Deref { subpattern }
}
hir::PatKind::Box(subpattern) => {
PatKind::Deref { subpattern: self.lower_pattern(subpattern) }
}
@ -367,19 +408,32 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
.get(pat.hir_id)
.expect("missing binding mode");
if let Some(s) = &mut self.rust_2024_migration_suggestion
&& explicit_ba.0 == ByRef::No
&& let ByRef::Yes(mutbl) = mode.0
{
let sugg_str = match mutbl {
Mutability::Not => "ref ",
Mutability::Mut => "ref mut ",
};
s.suggestion.push((
pat.span.with_lo(ident.span.lo()).shrink_to_lo(),
sugg_str.to_owned(),
));
s.binding_mode_count += 1;
if let Some(s) = &mut self.rust_2024_migration_suggestion {
if explicit_ba != hir::BindingMode::NONE
&& let Some((default_mode_span, default_ref_mutbl)) = s.default_mode_span
{
// If this overrides a by-ref default binding mode, label the binding mode.
s.default_mode_labels.insert(default_mode_span, default_ref_mutbl);
// If our suggestion is to elide redundnt modes, this will be one of them.
if s.suggest_eliding_modes {
s.suggestion.push((pat.span.with_hi(ident.span.lo()), String::new()));
s.binding_mode_count += 1;
}
}
if !s.suggest_eliding_modes
&& explicit_ba.0 == ByRef::No
&& let ByRef::Yes(mutbl) = mode.0
{
let sugg_str = match mutbl {
Mutability::Not => "ref ",
Mutability::Mut => "ref mut ",
};
s.suggestion.push((
pat.span.with_lo(ident.span.lo()).shrink_to_lo(),
sugg_str.to_owned(),
));
s.binding_mode_count += 1;
}
}
// A ref x pattern is the same node used for x, and as such it has