bjoernager/rust
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introduce #![feature(move_ref_pattern)]

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This commit is contained in:
Mazdak Farrokhzad 2020-01-19 02:14:51 +01:00
parent cef6894572
commit 7af9ff3e69
4 changed files with 126 additions and 74 deletions
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16
src/librustc_errors/diagnostic_builder.rs
View file

@ -186,11 +186,25 @@ impl<'a> DiagnosticBuilder<'a> {
/// all, and you just supplied a `Span` to create the diagnostic,
/// then the snippet will just include that `Span`, which is
/// called the primary span.
pub fn span_label<T: Into<String>>(&mut self, span: Span, label: T) -> &mut Self {
pub fn span_label(&mut self, span: Span, label: impl Into<String>) -> &mut Self {
self.0.diagnostic.span_label(span, label);
self
}
/// Labels all the given spans with the provided label.
/// See `span_label` for more information.
pub fn span_labels(
&mut self,
spans: impl IntoIterator<Item = Span>,
label: impl AsRef<str>,
) -> &mut Self {
let label = label.as_ref();
for span in spans {
self.0.diagnostic.span_label(span, label);
}
self
}
forward!(pub fn note_expected_found(
&mut self,
expected_label: &dyn fmt::Display,

4
src/librustc_feature/active.rs
View file

@ -538,6 +538,10 @@ declare_features! (
/// For example, you can write `x @ Some(y)`.
(active, bindings_after_at, "1.41.0", Some(65490), None),
/// Allows patterns with concurrent by-move and by-ref bindings.
/// For example, you can write `Foo(a, ref b)` where `a` is by-move and `b` is by-ref.
(active, move_ref_pattern, "1.42.0", Some(68354), None),
/// Allows `impl const Trait for T` syntax.
(active, const_trait_impl, "1.42.0", Some(67792), None),

133
src/librustc_mir_build/hair/pattern/check_match.rs
View file

@ -16,8 +16,7 @@ use rustc_session::lint::builtin::BINDINGS_WITH_VARIANT_NAME;
use rustc_session::lint::builtin::{IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS};
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_span::{MultiSpan, Span};
use rustc_span::{sym, Span};
use syntax::ast::Mutability;
use std::slice;
@ -114,8 +113,10 @@ impl PatCtxt<'_, '_> {
impl<'tcx> MatchVisitor<'_, 'tcx> {
fn check_patterns(&mut self, has_guard: bool, pat: &Pat<'_>) {
if !self.tcx.features().move_ref_pattern {
check_legality_of_move_bindings(self, has_guard, pat);
check_borrow_conflicts_in_at_patterns(self, pat);
}
pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
if !self.tcx.features().bindings_after_at {
check_legality_of_bindings_in_at_patterns(self, pat);
}
@ -559,6 +560,11 @@ fn maybe_point_at_variant(ty: Ty<'_>, patterns: &[super::Pat<'_>]) -> Vec<Span>
covered
}
/// Check if a by-value binding is by-value. That is, check if the binding's type is not `Copy`.
fn is_binding_by_move(cx: &MatchVisitor<'_, '_>, hir_id: HirId, span: Span) -> bool {
!cx.tables.node_type(hir_id).is_copy_modulo_regions(cx.tcx, cx.param_env, span)
}
/// Check the legality of legality of by-move bindings.
fn check_legality_of_move_bindings(cx: &mut MatchVisitor<'_, '_>, has_guard: bool, pat: &Pat<'_>) {
let sess = cx.tcx.sess;
@ -589,8 +595,7 @@ fn check_legality_of_move_bindings(cx: &mut MatchVisitor<'_, '_>, has_guard: boo
pat.walk_always(|p| {
if let hir::PatKind::Binding(.., sub) = &p.kind {
if let Some(ty::BindByValue(_)) = tables.extract_binding_mode(sess, p.hir_id, p.span) {
let pat_ty = tables.node_type(p.hir_id);
if !pat_ty.is_copy_modulo_regions(cx.tcx, cx.param_env, pat.span) {
if is_binding_by_move(cx, p.hir_id, p.span) {
check_move(p, sub.as_deref());
}
}
@ -599,11 +604,11 @@ fn check_legality_of_move_bindings(cx: &mut MatchVisitor<'_, '_>, has_guard: boo
// Found some bad by-move spans, error!
if !by_move_spans.is_empty() {
let mut err = struct_span_err!(
sess,
MultiSpan::from_spans(by_move_spans.clone()),
E0009,
"cannot bind by-move and by-ref in the same pattern",
let mut err = feature_err(
&sess.parse_sess,
sym::move_ref_pattern,
by_move_spans.clone(),
"binding by-move and by-ref in the same pattern is unstable",
);
for span in by_ref_spans.iter() {
err.span_label(*span, "by-ref pattern here");
@ -615,63 +620,86 @@ fn check_legality_of_move_bindings(cx: &mut MatchVisitor<'_, '_>, has_guard: boo
}
}
/// Check that there are no borrow conflicts in `binding @ subpat` patterns.
/// Check that there are no borrow or move conflicts in `binding @ subpat` patterns.
///
/// For example, this would reject:
/// - `ref x @ Some(ref mut y)`,
/// - `ref mut x @ Some(ref y)`
/// - `ref mut x @ Some(ref mut y)`.
/// - `ref mut x @ Some(ref y)`,
/// - `ref mut x @ Some(ref mut y)`,
/// - `ref mut? x @ Some(y)`, and
/// - `x @ Some(ref mut? y)`.
///
/// This analysis is *not* subsumed by NLL.
fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_>) {
let tab = cx.tables;
let sess = cx.tcx.sess;
// Get the mutability of `p` if it's by-ref.
let extract_binding_mut = |hir_id, span| match tab.extract_binding_mode(sess, hir_id, span)? {
ty::BindByValue(_) => None,
ty::BindByReference(m) => Some(m),
};
pat.walk_always(|pat| {
// Extract `sub` in `binding @ sub`.
let (name, sub) = match &pat.kind {
hir::PatKind::Binding(.., name, Some(sub)) => (*name, sub),
_ => return,
};
let binding_span = pat.span.with_hi(name.span.hi());
// Extract the mutability.
let mut_outer = match extract_binding_mut(pat.hir_id, pat.span) {
None => return,
Some(m) => m,
let tables = cx.tables;
let sess = cx.tcx.sess;
// Get the binding move, extract the mutability if by-ref.
let mut_outer = match tables.extract_binding_mode(sess, pat.hir_id, pat.span) {
Some(ty::BindByValue(_)) if is_binding_by_move(cx, pat.hir_id, pat.span) => {
// We have `x @ pat` where `x` is by-move. Reject all borrows in `pat`.
let mut conflicts_ref = Vec::new();
sub.each_binding(|_, hir_id, span, _| {
match tables.extract_binding_mode(sess, hir_id, span) {
Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id, span) => {
sess.delay_span_bug(span, "by-move in subpat unchecked by borrowck");
}
Some(ty::BindByValue(_)) | None => {}
Some(ty::BindByReference(_)) => conflicts_ref.push(span),
}
});
if !conflicts_ref.is_empty() {
let occurs_because = format!(
"move occurs because `{}` has type `{}` which does implement the `Copy` trait",
name,
tables.node_type(pat.hir_id),
);
sess.struct_span_err(pat.span, &format!("borrow of moved value: `{}`", name))
.span_label(binding_span, "value moved here")
.span_label(binding_span, occurs_because)
.span_labels(conflicts_ref, "value borrowed here after move")
.emit();
}
return;
}
Some(ty::BindByValue(_)) | None => return,
Some(ty::BindByReference(m)) => m,
};
// We now have `ref $mut_outer binding @ sub` (semantically).
// Recurse into each binding in `sub` and find mutability conflicts.
// Recurse into each binding in `sub` and find mutability or move conflicts.
let mut conflicts_move = Vec::new();
let mut conflicts_mut_mut = Vec::new();
let mut conflicts_mut_ref = Vec::new();
sub.each_binding(|_, hir_id, span, _| {
if let Some(mut_inner) = extract_binding_mut(hir_id, span) {
match (mut_outer, mut_inner) {
(Mutability::Not, Mutability::Not) => {}
(Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push(span),
_ => conflicts_mut_ref.push(span),
}
sub.each_binding(|_, hir_id, span, _| match tables.extract_binding_mode(sess, hir_id, span) {
Some(ty::BindByReference(mut_inner)) => match (mut_outer, mut_inner) {
(Mutability::Not, Mutability::Not) => {} // Both sides are `ref`.
(Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push(span), // 2x `ref mut`.
_ => conflicts_mut_ref.push(span), // `ref` + `ref mut` in either direction.
},
Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id, span) => {
conflicts_move.push(span) // `ref mut?` + by-move conflict.
}
Some(ty::BindByValue(_)) | None => {} // `ref mut?` + by-copy is fine.
});
// Report errors if any.
let binding_span = pat.span.with_hi(name.span.hi());
if !conflicts_mut_mut.is_empty() {
// Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`.
let msg = &format!("cannot borrow `{}` as mutable more than once at a time", name);
let mut err = sess.struct_span_err(pat.span, msg);
err.span_label(binding_span, "first mutable borrow occurs here");
for sp in conflicts_mut_mut {
err.span_label(sp, "another mutable borrow occurs here");
}
for sp in conflicts_mut_ref {
err.span_label(sp, "also borrowed as immutable here");
}
err.emit();
sess.struct_span_err(pat.span, msg)
.span_label(binding_span, "first mutable borrow occurs here")
.span_labels(conflicts_mut_mut, "another mutable borrow occurs here")
.span_labels(conflicts_mut_ref, "also borrowed as immutable here")
.span_labels(conflicts_move, "also moved here")
.emit();
} else if !conflicts_mut_ref.is_empty() {
// Report mutability conflicts for e.g. `ref x @ Some(ref mut y)` or the converse.
let (primary, also) = match mut_outer {
@ -682,14 +710,19 @@ fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_
"cannot borrow `{}` as {} because it is also borrowed as {}",
name, also, primary,
);
let mut err = sess.struct_span_err(pat.span, msg);
err.span_label(binding_span, &format!("{} borrow occurs here", primary));
for sp in conflicts_mut_ref {
err.span_label(sp, &format!("{} borrow occurs here", also));
sess.struct_span_err(pat.span, msg)
.span_label(binding_span, format!("{} borrow occurs here", primary))
.span_labels(conflicts_mut_ref, format!("{} borrow occurs here", also))
.span_labels(conflicts_move, "also moved here")
.emit();
} else if !conflicts_move.is_empty() {
// Report by-ref and by-move conflicts, e.g. `ref x @ y`.
let msg = &format!("cannot move out of `{}` because it is borrowed", name);
sess.struct_span_err(pat.span, msg)
.span_label(binding_span, format!("borrow of `{}` occurs here", name))
.span_labels(conflicts_move, format!("move out of `{}` occurs here", name))
.emit();
}
err.emit();
}
});
}
/// Forbids bindings in `@` patterns. This used to be is necessary for memory safety,

1
src/librustc_span/symbol.rs
View file

@ -455,6 +455,7 @@ symbols! {
module,
module_path,
more_struct_aliases,
move_ref_pattern,
move_val_init,
movbe_target_feature,
mul_with_overflow,