bjoernager/rust
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Actually implement the feature in the compiler

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Including all the bootstrapping tweaks in the library.
This commit is contained in:
Scott McMurray 2021-04-15 00:33:55 -07:00
parent c10eec3a1c
commit ca92b5a23a
10 changed files with 144 additions and 51 deletions
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58
compiler/rustc_ast_lowering/src/expr.rs
View file

@ -562,8 +562,8 @@ 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| {
@ -592,9 +592,9 @@ 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,
@ -1896,14 +1896,14 @@ 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],
)
};
@ -1921,8 +1921,8 @@ 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(
@ -1931,27 +1931,21 @@ 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);
@ -1962,25 +1956,25 @@ 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,
)
}

10
compiler/rustc_ast_lowering/src/lib.rs
View file

@ -331,7 +331,7 @@ 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)
@ -2479,14 +2479,14 @@ 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> {