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Auto merge of #84767 - scottmcm:try_trait_actual, r=lcnr
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Implement the new desugaring from `try_trait_v2`

~~Currently blocked on #84782, which has a PR in #84811 Rebased atop that fix.

`try_trait_v2` tracking issue: #84277

Unfortunately this is already touching a ton of things, so if you have suggestions for good ways to split it up, I'd be happy to hear them.  (The combination between the use in the library, the compiler changes, the corresponding diagnostic differences, even MIR tests mean that I don't really have a great plan for it other than trying to have decently-readable commits.

r? `@ghost`

~~(This probably shouldn't go in during the last week before the fork anyway.)~~ Fork happened.
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bors committed May 18, 2021
2 parents 491cf55 + e2edee4 commit 4e3e6db
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Showing 91 changed files with 1,176 additions and 798 deletions.
58 changes: 26 additions & 32 deletions compiler/rustc_ast_lowering/src/expr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -560,8 +560,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
)
}

/// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_ok(<expr>) }`,
/// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_ok(()) }`
/// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_output(<expr>) }`,
/// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }`
/// and save the block id to use it as a break target for desugaring of the `?` operator.
fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> {
self.with_catch_scope(body.id, |this| {
Expand Down Expand Up @@ -590,9 +590,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
let ok_wrapped_span =
this.mark_span_with_reason(DesugaringKind::TryBlock, tail_expr.span, None);

// `::std::ops::Try::from_ok($tail_expr)`
// `::std::ops::Try::from_output($tail_expr)`
block.expr = Some(this.wrap_in_try_constructor(
hir::LangItem::TryFromOk,
hir::LangItem::TryTraitFromOutput,
try_span,
tail_expr,
ok_wrapped_span,
Expand Down Expand Up @@ -1579,14 +1579,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
self.allow_try_trait.clone(),
);

// `Try::into_result(<expr>)`
// `Try::branch(<expr>)`
let scrutinee = {
// expand <expr>
let sub_expr = self.lower_expr_mut(sub_expr);

self.expr_call_lang_item_fn(
unstable_span,
hir::LangItem::TryIntoResult,
hir::LangItem::TryTraitBranch,
arena_vec![self; sub_expr],
)
};
Expand All @@ -1604,8 +1604,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
};
let attrs = vec![attr];

// `Ok(val) => #[allow(unreachable_code)] val,`
let ok_arm = {
// `ControlFlow::Continue(val) => #[allow(unreachable_code)] val,`
let continue_arm = {
let val_ident = Ident::with_dummy_span(sym::val);
let (val_pat, val_pat_nid) = self.pat_ident(span, val_ident);
let val_expr = self.arena.alloc(self.expr_ident_with_attrs(
Expand All @@ -1614,27 +1614,21 @@ impl<'hir> LoweringContext<'_, 'hir> {
val_pat_nid,
ThinVec::from(attrs.clone()),
));
let ok_pat = self.pat_ok(span, val_pat);
self.arm(ok_pat, val_expr)
let continue_pat = self.pat_cf_continue(unstable_span, val_pat);
self.arm(continue_pat, val_expr)
};

// `Err(err) => #[allow(unreachable_code)]
// return Try::from_error(From::from(err)),`
let err_arm = {
let err_ident = Ident::with_dummy_span(sym::err);
let (err_local, err_local_nid) = self.pat_ident(try_span, err_ident);
let from_expr = {
let err_expr = self.expr_ident_mut(try_span, err_ident, err_local_nid);
self.expr_call_lang_item_fn(
try_span,
hir::LangItem::FromFrom,
arena_vec![self; err_expr],
)
};
let from_err_expr = self.wrap_in_try_constructor(
hir::LangItem::TryFromError,
unstable_span,
from_expr,
// `ControlFlow::Break(residual) =>
// #[allow(unreachable_code)]
// return Try::from_residual(residual),`
let break_arm = {
let residual_ident = Ident::with_dummy_span(sym::residual);
let (residual_local, residual_local_nid) = self.pat_ident(try_span, residual_ident);
let residual_expr = self.expr_ident_mut(try_span, residual_ident, residual_local_nid);
let from_residual_expr = self.wrap_in_try_constructor(
hir::LangItem::TryTraitFromResidual,
try_span,
self.arena.alloc(residual_expr),
unstable_span,
);
let thin_attrs = ThinVec::from(attrs);
Expand All @@ -1645,25 +1639,25 @@ impl<'hir> LoweringContext<'_, 'hir> {
try_span,
hir::ExprKind::Break(
hir::Destination { label: None, target_id },
Some(from_err_expr),
Some(from_residual_expr),
),
thin_attrs,
))
} else {
self.arena.alloc(self.expr(
try_span,
hir::ExprKind::Ret(Some(from_err_expr)),
hir::ExprKind::Ret(Some(from_residual_expr)),
thin_attrs,
))
};

let err_pat = self.pat_err(try_span, err_local);
self.arm(err_pat, ret_expr)
let break_pat = self.pat_cf_break(try_span, residual_local);
self.arm(break_pat, ret_expr)
};

hir::ExprKind::Match(
scrutinee,
arena_vec![self; err_arm, ok_arm],
arena_vec![self; break_arm, continue_arm],
hir::MatchSource::TryDesugar,
)
}
Expand Down
10 changes: 5 additions & 5 deletions compiler/rustc_ast_lowering/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -332,7 +332,7 @@ pub fn lower_crate<'a, 'hir>(
lifetimes_to_define: Vec::new(),
is_collecting_in_band_lifetimes: false,
in_scope_lifetimes: Vec::new(),
allow_try_trait: Some([sym::try_trait][..].into()),
allow_try_trait: Some([sym::control_flow_enum, sym::try_trait_v2][..].into()),
allow_gen_future: Some([sym::gen_future][..].into()),
}
.lower_crate(krate)
Expand Down Expand Up @@ -2490,14 +2490,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.pat(span, hir::PatKind::Lit(expr))
}

fn pat_ok(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
fn pat_cf_continue(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
let field = self.single_pat_field(span, pat);
self.pat_lang_item_variant(span, hir::LangItem::ResultOk, field)
self.pat_lang_item_variant(span, hir::LangItem::ControlFlowContinue, field)
}

fn pat_err(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
fn pat_cf_break(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
let field = self.single_pat_field(span, pat);
self.pat_lang_item_variant(span, hir::LangItem::ResultErr, field)
self.pat_lang_item_variant(span, hir::LangItem::ControlFlowBreak, field)
}

fn pat_some(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
Expand Down
11 changes: 7 additions & 4 deletions compiler/rustc_hir/src/lang_items.rs
Original file line number Diff line number Diff line change
Expand Up @@ -308,12 +308,12 @@ language_item_table! {

Termination, sym::termination, termination, Target::Trait;

Try, kw::Try, try_trait, Target::Trait;
Try, sym::Try, try_trait, Target::Trait;

// Language items from AST lowering
TryFromError, sym::from_error, from_error_fn, Target::Method(MethodKind::Trait { body: false });
TryFromOk, sym::from_ok, from_ok_fn, Target::Method(MethodKind::Trait { body: false });
TryIntoResult, sym::into_result, into_result_fn, Target::Method(MethodKind::Trait { body: false });
TryTraitFromResidual, sym::from_residual, from_residual_fn, Target::Method(MethodKind::Trait { body: false });
TryTraitFromOutput, sym::from_output, from_output_fn, Target::Method(MethodKind::Trait { body: false });
TryTraitBranch, sym::branch, branch_fn, Target::Method(MethodKind::Trait { body: false });

PollReady, sym::Ready, poll_ready_variant, Target::Variant;
PollPending, sym::Pending, poll_pending_variant, Target::Variant;
Expand All @@ -331,6 +331,9 @@ language_item_table! {
ResultOk, sym::Ok, result_ok_variant, Target::Variant;
ResultErr, sym::Err, result_err_variant, Target::Variant;

ControlFlowContinue, sym::Continue, cf_continue_variant, Target::Variant;
ControlFlowBreak, sym::Break, cf_break_variant, Target::Variant;

IntoIterIntoIter, sym::into_iter, into_iter_fn, Target::Method(MethodKind::Trait { body: false });
IteratorNext, sym::next, next_fn, Target::Method(MethodKind::Trait { body: false});

Expand Down
13 changes: 8 additions & 5 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -130,10 +130,12 @@ symbols! {
BTreeSet,
BinaryHeap,
Borrow,
Break,
C,
CString,
Center,
Clone,
Continue,
Copy,
Count,
Debug,
Expand Down Expand Up @@ -326,6 +328,7 @@ symbols! {
box_patterns,
box_syntax,
braced_empty_structs,
branch,
breakpoint,
bridge,
bswap,
Expand Down Expand Up @@ -411,6 +414,7 @@ symbols! {
constructor,
contents,
context,
control_flow_enum,
convert,
copy,
copy_closures,
Expand Down Expand Up @@ -511,7 +515,6 @@ symbols! {
env,
eq,
ermsb_target_feature,
err,
exact_div,
except,
exchange_malloc,
Expand Down Expand Up @@ -581,10 +584,10 @@ symbols! {
frem_fast,
from,
from_desugaring,
from_error,
from_generator,
from_method,
from_ok,
from_output,
from_residual,
from_size_align_unchecked,
from_trait,
from_usize,
Expand Down Expand Up @@ -653,7 +656,6 @@ symbols! {
instruction_set,
intel,
into_iter,
into_result,
into_trait,
intra_doc_pointers,
intrinsics,
Expand Down Expand Up @@ -965,6 +967,7 @@ symbols! {
repr_packed,
repr_simd,
repr_transparent,
residual,
result,
result_type,
rhs,
Expand Down Expand Up @@ -1232,7 +1235,7 @@ symbols! {
try_blocks,
try_from_trait,
try_into_trait,
try_trait,
try_trait_v2,
tt,
tuple,
tuple_from_req,
Expand Down
4 changes: 2 additions & 2 deletions library/alloc/src/collections/vec_deque/iter.rs
Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ impl<'a, T> Iterator for Iter<'a, T> {
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
R: Try<Output = B>,
{
let (mut iter, final_res);
if self.tail <= self.head {
Expand Down Expand Up @@ -140,7 +140,7 @@ impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
R: Try<Output = B>,
{
let (mut iter, final_res);
if self.tail <= self.head {
Expand Down
3 changes: 2 additions & 1 deletion library/alloc/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -140,7 +140,8 @@
#![feature(maybe_uninit_extra, maybe_uninit_slice, maybe_uninit_uninit_array)]
#![feature(alloc_layout_extra)]
#![feature(trusted_random_access)]
#![feature(try_trait)]
#![cfg_attr(bootstrap, feature(try_trait))]
#![cfg_attr(not(bootstrap), feature(try_trait_v2))]
#![feature(min_type_alias_impl_trait)]
#![feature(associated_type_bounds)]
#![feature(slice_group_by)]
Expand Down
4 changes: 2 additions & 2 deletions library/core/src/iter/adapters/chain.rs
Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,7 @@ where
where
Self: Sized,
F: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
if let Some(ref mut a) = self.a {
acc = a.try_fold(acc, &mut f)?;
Expand Down Expand Up @@ -281,7 +281,7 @@ where
where
Self: Sized,
F: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
if let Some(ref mut b) = self.b {
acc = b.try_rfold(acc, &mut f)?;
Expand Down
4 changes: 2 additions & 2 deletions library/core/src/iter/adapters/cloned.rs
Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ where
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
R: Try<Output = B>,
{
self.it.try_fold(init, clone_try_fold(f))
}
Expand Down Expand Up @@ -82,7 +82,7 @@ where
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
R: Try<Output = B>,
{
self.it.try_rfold(init, clone_try_fold(f))
}
Expand Down
4 changes: 2 additions & 2 deletions library/core/src/iter/adapters/copied.rs
Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ where
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
R: Try<Output = B>,
{
self.it.try_fold(init, copy_try_fold(f))
}
Expand Down Expand Up @@ -98,7 +98,7 @@ where
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
R: Try<Output = B>,
{
self.it.try_rfold(init, copy_try_fold(f))
}
Expand Down
2 changes: 1 addition & 1 deletion library/core/src/iter/adapters/cycle.rs
Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@ where
fn try_fold<Acc, F, R>(&mut self, mut acc: Acc, mut f: F) -> R
where
F: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
// fully iterate the current iterator. this is necessary because
// `self.iter` may be empty even when `self.orig` isn't
Expand Down
4 changes: 2 additions & 2 deletions library/core/src/iter/adapters/enumerate.rs
Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ where
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
#[inline]
fn enumerate<'a, T, Acc, R>(
Expand Down Expand Up @@ -150,7 +150,7 @@ where
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
// Can safely add and subtract the count, as `ExactSizeIterator` promises
// that the number of elements fits into a `usize`.
Expand Down
6 changes: 3 additions & 3 deletions library/core/src/iter/adapters/filter.rs
Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ fn filter_fold<T, Acc>(
move |acc, item| if predicate(&item) { fold(acc, item) } else { acc }
}

fn filter_try_fold<'a, T, Acc, R: Try<Ok = Acc>>(
fn filter_try_fold<'a, T, Acc, R: Try<Output = Acc>>(
predicate: &'a mut impl FnMut(&T) -> bool,
mut fold: impl FnMut(Acc, T) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
Expand Down Expand Up @@ -88,7 +88,7 @@ where
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
self.iter.try_fold(init, filter_try_fold(&mut self.predicate, fold))
}
Expand Down Expand Up @@ -117,7 +117,7 @@ where
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
R: Try<Output = Acc>,
{
self.iter.try_rfold(init, filter_try_fold(&mut self.predicate, fold))
}
Expand Down
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