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3 - Make more use of let_chains #94420

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Feb 28, 2022
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3 - Make more use of let_chains #94420

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21 changes: 10 additions & 11 deletions compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1921,17 +1921,16 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
err.span_label(assigned_span, format!("first assignment to {}", place_description));
}
}
if let Some(decl) = local_decl {
if let Some(name) = local_name {
if decl.can_be_made_mutable() {
err.span_suggestion(
decl.source_info.span,
"consider making this binding mutable",
format!("mut {}", name),
Applicability::MachineApplicable,
);
}
}
if let Some(decl) = local_decl
&& let Some(name) = local_name
&& decl.can_be_made_mutable()
{
err.span_suggestion(
decl.source_info.span,
"consider making this binding mutable",
format!("mut {}", name),
Applicability::MachineApplicable,
);
}
err.span_label(span, msg);
self.buffer_error(err);
Expand Down
15 changes: 6 additions & 9 deletions compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -375,15 +375,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {

Some(Cause::DropVar(local, location)) => {
let mut should_note_order = false;
if self.local_names[local].is_some() {
if let Some((WriteKind::StorageDeadOrDrop, place)) = kind_place {
if let Some(borrowed_local) = place.as_local() {
if self.local_names[borrowed_local].is_some() && local != borrowed_local
{
should_note_order = true;
}
}
}
if self.local_names[local].is_some()
&& let Some((WriteKind::StorageDeadOrDrop, place)) = kind_place
&& let Some(borrowed_local) = place.as_local()
&& self.local_names[borrowed_local].is_some() && local != borrowed_local
{
should_note_order = true;
}

BorrowExplanation::UsedLaterWhenDropped {
Expand Down
26 changes: 11 additions & 15 deletions compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1086,21 +1086,17 @@ fn get_mut_span_in_struct_field<'tcx>(
field: &mir::Field,
) -> Option<Span> {
// Expect our local to be a reference to a struct of some kind.
if let ty::Ref(_, ty, _) = ty.kind() {
if let ty::Adt(def, _) = ty.kind() {
let field = def.all_fields().nth(field.index())?;
// Use the HIR types to construct the diagnostic message.
let node = tcx.hir().find_by_def_id(field.did.as_local()?)?;
// Now we're dealing with the actual struct that we're going to suggest a change to,
// we can expect a field that is an immutable reference to a type.
if let hir::Node::Field(field) = node {
if let hir::TyKind::Rptr(lifetime, hir::MutTy { mutbl: hir::Mutability::Not, ty }) =
field.ty.kind
{
return Some(lifetime.span.between(ty.span));
}
}
}
if let ty::Ref(_, ty, _) = ty.kind()
&& let ty::Adt(def, _) = ty.kind()
&& let field = def.all_fields().nth(field.index())?
// Use the HIR types to construct the diagnostic message.
&& let node = tcx.hir().find_by_def_id(field.did.as_local()?)?
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This assignment could be inlined below, right?

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Yes, the same way the old

let node = tcx.hir().find_by_def_id(field.did.as_local()?)?;
// Now we're dealing with the actual struct that we're going to suggest a change to,
// we can expect a field that is an immutable reference to a type.
if let hir::Node::Field(field) = node {

could be inlined to

// Now we're dealing with the actual struct that we're going to suggest a change to,
// we can expect a field that is an immutable reference to a type.
if let hir::Node::Field(field) = tcx.hir().find_by_def_id(field.did.as_local()?)? {

I am trying to transpose everything verbatim

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If you are curious, assembly output is the same for both optimized and un-optimized

// Now we're dealing with the actual struct that we're going to suggest a change to,
// we can expect a field that is an immutable reference to a type.
&& let hir::Node::Field(field) = node
&& let hir::TyKind::Rptr(lt, hir::MutTy { mutbl: hir::Mutability::Not, ty }) = field.ty.kind
{
return Some(lt.span.between(ty.span));
}

None
Expand Down
13 changes: 5 additions & 8 deletions compiler/rustc_borrowck/src/diagnostics/region_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -140,14 +140,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {

/// Returns `true` if a closure is inferred to be an `FnMut` closure.
fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
if let Some(ty::ReFree(free_region)) = self.to_error_region(fr).as_deref() {
if let ty::BoundRegionKind::BrEnv = free_region.bound_region {
if let DefiningTy::Closure(_, substs) =
self.regioncx.universal_regions().defining_ty
{
return substs.as_closure().kind() == ty::ClosureKind::FnMut;
}
}
if let Some(ty::ReFree(free_region)) = self.to_error_region(fr).as_deref()
&& let ty::BoundRegionKind::BrEnv = free_region.bound_region
&& let DefiningTy::Closure(_, substs) = self.regioncx.universal_regions().defining_ty
{
return substs.as_closure().kind() == ty::ClosureKind::FnMut;
}

false
Expand Down
21 changes: 10 additions & 11 deletions compiler/rustc_borrowck/src/lib.rs
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Original file line number Diff line number Diff line change
@@ -1,15 +1,16 @@
//! This query borrow-checks the MIR to (further) ensure it is not broken.

#![allow(rustc::potential_query_instability)]
#![feature(bool_to_option)]
#![feature(box_patterns)]
#![feature(crate_visibility_modifier)]
#![feature(let_chains)]
#![feature(let_else)]
#![feature(min_specialization)]
#![feature(stmt_expr_attributes)]
#![feature(trusted_step)]
#![feature(try_blocks)]
#![recursion_limit = "256"]
#![allow(rustc::potential_query_instability)]

#[macro_use]
extern crate rustc_middle;
Expand Down Expand Up @@ -159,16 +160,14 @@ fn do_mir_borrowck<'a, 'tcx>(
for var_debug_info in &input_body.var_debug_info {
if let VarDebugInfoContents::Place(place) = var_debug_info.value {
if let Some(local) = place.as_local() {
if let Some(prev_name) = local_names[local] {
if var_debug_info.name != prev_name {
span_bug!(
var_debug_info.source_info.span,
"local {:?} has many names (`{}` vs `{}`)",
local,
prev_name,
var_debug_info.name
);
}
if let Some(prev_name) = local_names[local] && var_debug_info.name != prev_name {
span_bug!(
var_debug_info.source_info.span,
"local {:?} has many names (`{}` vs `{}`)",
local,
prev_name,
var_debug_info.name
);
}
local_names[local] = Some(var_debug_info.name);
}
Expand Down
6 changes: 2 additions & 4 deletions compiler/rustc_borrowck/src/places_conflict.rs
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Expand Up @@ -60,10 +60,8 @@ pub(super) fn borrow_conflicts_with_place<'tcx>(

// This Local/Local case is handled by the more general code below, but
// it's so common that it's a speed win to check for it first.
if let Some(l1) = borrow_place.as_local() {
if let Some(l2) = access_place.as_local() {
return l1 == l2;
}
if let Some(l1) = borrow_place.as_local() && let Some(l2) = access_place.as_local() {
return l1 == l2;
}

place_components_conflict(tcx, body, borrow_place, borrow_kind, access_place, access, bias)
Expand Down