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More let_else adoptions #93590

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Feb 2, 2022
Merged

More let_else adoptions #93590

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4 changes: 1 addition & 3 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -471,9 +471,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
// two imports.
for new_node_id in [id1, id2] {
let new_id = self.resolver.local_def_id(new_node_id);
let res = if let Some(res) = resolutions.next() {
res
} else {
let Some(res) = resolutions.next() else {
// Associate an HirId to both ids even if there is no resolution.
let _old = self
.node_id_to_hir_id
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1 change: 1 addition & 0 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@

#![feature(crate_visibility_modifier)]
#![feature(box_patterns)]
#![feature(let_else)]
#![feature(never_type)]
#![recursion_limit = "256"]
#![cfg_attr(not(bootstrap), allow(rustc::potential_query_instability))]
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138 changes: 67 additions & 71 deletions compiler/rustc_attr/src/builtin.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -217,85 +217,81 @@ where
let mut issue_num = None;
let mut is_soft = false;
for meta in metas {
if let Some(mi) = meta.meta_item() {
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This code is being refactored in #93017. Does c271373db4a58920c2a9629cebaab321b3e2ca57 need to use more let-else?

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It still has a diverging block in the else case, so your refactored code can still benefit from let else adoption. But I can remove it here so that it doesn't cause conflicts. Does that sound like a plan to you?

match mi.name_or_empty() {
sym::feature => {
if !get(mi, &mut feature) {
continue 'outer;
}
let Some(mi) = meta.meta_item() else {
handle_errors(
&sess.parse_sess,
meta.span(),
AttrError::UnsupportedLiteral("unsupported literal", false),
);
continue 'outer;
};
match mi.name_or_empty() {
sym::feature => {
if !get(mi, &mut feature) {
continue 'outer;
}
sym::reason => {
if !get(mi, &mut reason) {
continue 'outer;
}
}
sym::reason => {
if !get(mi, &mut reason) {
continue 'outer;
}
}
sym::issue => {
if !get(mi, &mut issue) {
continue 'outer;
}
sym::issue => {
if !get(mi, &mut issue) {
continue 'outer;
}

// These unwraps are safe because `get` ensures the meta item
// is a name/value pair string literal.
issue_num = match issue.unwrap().as_str() {
"none" => None,
issue => {
let emit_diag = |msg: &str| {
struct_span_err!(
diagnostic,
mi.span,
E0545,
"`issue` must be a non-zero numeric string \
or \"none\"",
)
.span_label(
mi.name_value_literal_span().unwrap(),
msg,
)
.emit();
};
match issue.parse() {
Ok(0) => {
emit_diag(
"`issue` must not be \"0\", \
use \"none\" instead",
);
continue 'outer;
}
Ok(num) => NonZeroU32::new(num),
Err(err) => {
emit_diag(&err.to_string());
continue 'outer;
}
// These unwraps are safe because `get` ensures the meta item
// is a name/value pair string literal.
issue_num = match issue.unwrap().as_str() {
"none" => None,
issue => {
let emit_diag = |msg: &str| {
struct_span_err!(
diagnostic,
mi.span,
E0545,
"`issue` must be a non-zero numeric string \
or \"none\"",
)
.span_label(mi.name_value_literal_span().unwrap(), msg)
.emit();
};
match issue.parse() {
Ok(0) => {
emit_diag(
"`issue` must not be \"0\", \
use \"none\" instead",
);
continue 'outer;
}
Ok(num) => NonZeroU32::new(num),
Err(err) => {
emit_diag(&err.to_string());
continue 'outer;
}
}
};
}
sym::soft => {
if !mi.is_word() {
let msg = "`soft` should not have any arguments";
sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
}
is_soft = true;
}
_ => {
handle_errors(
&sess.parse_sess,
meta.span(),
AttrError::UnknownMetaItem(
pprust::path_to_string(&mi.path),
&["feature", "reason", "issue", "soft"],
),
);
continue 'outer;
};
}
sym::soft => {
if !mi.is_word() {
let msg = "`soft` should not have any arguments";
sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
}
is_soft = true;
}
_ => {
handle_errors(
&sess.parse_sess,
meta.span(),
AttrError::UnknownMetaItem(
pprust::path_to_string(&mi.path),
&["feature", "reason", "issue", "soft"],
),
);
continue 'outer;
}
} else {
handle_errors(
&sess.parse_sess,
meta.span(),
AttrError::UnsupportedLiteral("unsupported literal", false),
);
continue 'outer;
}
}

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2 changes: 2 additions & 0 deletions compiler/rustc_attr/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@
//! The goal is to move the definition of `MetaItem` and things that don't need to be in `syntax`
//! to this crate.

#![feature(let_else)]

#[macro_use]
extern crate rustc_macros;

Expand Down
137 changes: 65 additions & 72 deletions compiler/rustc_borrowck/src/diagnostics/region_name.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -311,43 +311,39 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
ty::BoundRegionKind::BrEnv => {
let def_ty = self.regioncx.universal_regions().defining_ty;

if let DefiningTy::Closure(_, substs) = def_ty {
let args_span = if let hir::ExprKind::Closure(_, _, _, span, _) =
tcx.hir().expect_expr(self.mir_hir_id()).kind
{
span
} else {
bug!("Closure is not defined by a closure expr");
};
let region_name = self.synthesize_region_name();

let closure_kind_ty = substs.as_closure().kind_ty();
let note = match closure_kind_ty.to_opt_closure_kind() {
Some(ty::ClosureKind::Fn) => {
"closure implements `Fn`, so references to captured variables \
can't escape the closure"
}
Some(ty::ClosureKind::FnMut) => {
"closure implements `FnMut`, so references to captured variables \
can't escape the closure"
}
Some(ty::ClosureKind::FnOnce) => {
bug!("BrEnv in a `FnOnce` closure");
}
None => bug!("Closure kind not inferred in borrow check"),
};

Some(RegionName {
name: region_name,
source: RegionNameSource::SynthesizedFreeEnvRegion(
args_span,
note.to_string(),
),
})
} else {
let DefiningTy::Closure(_, substs) = def_ty else {
// Can't have BrEnv in functions, constants or generators.
bug!("BrEnv outside of closure.");
}
};
let hir::ExprKind::Closure(_, _, _, args_span, _) =
tcx.hir().expect_expr(self.mir_hir_id()).kind else {
bug!("Closure is not defined by a closure expr");
};
let region_name = self.synthesize_region_name();

let closure_kind_ty = substs.as_closure().kind_ty();
let note = match closure_kind_ty.to_opt_closure_kind() {
Some(ty::ClosureKind::Fn) => {
"closure implements `Fn`, so references to captured variables \
can't escape the closure"
}
Some(ty::ClosureKind::FnMut) => {
"closure implements `FnMut`, so references to captured variables \
can't escape the closure"
}
Some(ty::ClosureKind::FnOnce) => {
bug!("BrEnv in a `FnOnce` closure");
}
None => bug!("Closure kind not inferred in borrow check"),
};

Some(RegionName {
name: region_name,
source: RegionNameSource::SynthesizedFreeEnvRegion(
args_span,
note.to_string(),
),
})
}

ty::BoundRegionKind::BrAnon(_) => None,
Expand Down Expand Up @@ -765,48 +761,45 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
fn get_future_inner_return_ty(&self, hir_ty: &'tcx hir::Ty<'tcx>) -> &'tcx hir::Ty<'tcx> {
let hir = self.infcx.tcx.hir();

if let hir::TyKind::OpaqueDef(id, _) = hir_ty.kind {
let opaque_ty = hir.item(id);
if let hir::ItemKind::OpaqueTy(hir::OpaqueTy {
bounds:
[
hir::GenericBound::LangItemTrait(
hir::LangItem::Future,
_,
_,
hir::GenericArgs {
bindings:
[
hir::TypeBinding {
ident: Ident { name: sym::Output, .. },
kind:
hir::TypeBindingKind::Equality {
term: hir::Term::Ty(ty),
},
..
},
],
..
},
),
],
..
}) = opaque_ty.kind
{
ty
} else {
span_bug!(
hir_ty.span,
"bounds from lowered return type of async fn did not match expected format: {:?}",
opaque_ty
);
}
} else {
let hir::TyKind::OpaqueDef(id, _) = hir_ty.kind else {
span_bug!(
hir_ty.span,
"lowered return type of async fn is not OpaqueDef: {:?}",
hir_ty
);
};
let opaque_ty = hir.item(id);
if let hir::ItemKind::OpaqueTy(hir::OpaqueTy {
bounds:
[
hir::GenericBound::LangItemTrait(
hir::LangItem::Future,
_,
_,
hir::GenericArgs {
bindings:
[
hir::TypeBinding {
ident: Ident { name: sym::Output, .. },
kind:
hir::TypeBindingKind::Equality { term: hir::Term::Ty(ty) },
..
},
],
..
},
),
],
..
}) = opaque_ty.kind
{
ty
} else {
span_bug!(
hir_ty.span,
"bounds from lowered return type of async fn did not match expected format: {:?}",
opaque_ty
);
}
}

Expand Down
5 changes: 2 additions & 3 deletions compiler/rustc_borrowck/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1427,9 +1427,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
bug!("temporary should be initialized exactly once")
};

let loc = match init.location {
InitLocation::Statement(stmt) => stmt,
_ => bug!("temporary initialized in arguments"),
let InitLocation::Statement(loc) = init.location else {
bug!("temporary initialized in arguments")
};

let body = self.body;
Expand Down
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