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or-patterns: middle/dead: remove top_pats_hack.
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Also tweak walkers on `Pat`.
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@Centril
Centril committed Sep 21, 2019
1 parent 370fbcc commit 0918dc4
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Showing 3 changed files with 100 additions and 95 deletions.
62 changes: 42 additions & 20 deletions src/librustc/hir/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -882,39 +882,61 @@ impl fmt::Debug for Pat {

impl Pat {
// FIXME(#19596) this is a workaround, but there should be a better way
fn walk_<G>(&self, it: &mut G) -> bool
where G: FnMut(&Pat) -> bool
{
fn walk_short_(&self, it: &mut impl FnMut(&Pat) -> bool) -> bool {
if !it(self) {
return false;
}

use PatKind::*;
match &self.node {
PatKind::Binding(.., Some(p)) => p.walk_(it),
PatKind::Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_(it)),
PatKind::TupleStruct(_, s, _) | PatKind::Tuple(s, _) | PatKind::Or(s) => {
s.iter().all(|p| p.walk_(it))
}
PatKind::Box(s) | PatKind::Ref(s, _) => s.walk_(it),
PatKind::Slice(before, slice, after) => {
Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
Slice(before, slice, after) => {
before.iter()
.chain(slice.iter())
.chain(after.iter())
.all(|p| p.walk_(it))
.all(|p| p.walk_short_(it))
}
PatKind::Wild |
PatKind::Lit(_) |
PatKind::Range(..) |
PatKind::Binding(..) |
PatKind::Path(_) => {
true
}
}

/// Walk the pattern in left-to-right order,
/// short circuiting (with `.all(..)`) if `false` is returned.
///
/// Note that when visiting e.g. `Tuple(ps)`,
/// if visiting `ps[0]` returns `false`,
/// then `ps[1]` will not be visited.
pub fn walk_short(&self, mut it: impl FnMut(&Pat) -> bool) -> bool {
self.walk_short_(&mut it)
}

// FIXME(#19596) this is a workaround, but there should be a better way
fn walk_(&self, it: &mut impl FnMut(&Pat) -> bool) {
if !it(self) {
return;
}

use PatKind::*;
match &self.node {
Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {},
Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
Slice(before, slice, after) => {
before.iter()
.chain(slice.iter())
.chain(after.iter())
.for_each(|p| p.walk_(it))
}
}
}

pub fn walk<F>(&self, mut it: F) -> bool
where F: FnMut(&Pat) -> bool
{
/// Walk the pattern in left-to-right order.
///
/// If `it(pat)` returns `false`, the children are not visited.
pub fn walk(&self, mut it: impl FnMut(&Pat) -> bool) {
self.walk_(&mut it)
}
}
Expand Down
112 changes: 51 additions & 61 deletions src/librustc/hir/pat_util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,9 +66,7 @@ impl hir::Pat {

/// Call `f` on every "binding" in a pattern, e.g., on `a` in
/// `match foo() { Some(a) => (), None => () }`
pub fn each_binding<F>(&self, mut f: F)
where F: FnMut(hir::BindingAnnotation, HirId, Span, ast::Ident),
{
pub fn each_binding(&self, mut f: impl FnMut(hir::BindingAnnotation, HirId, Span, ast::Ident)) {
self.walk(|p| {
if let PatKind::Binding(binding_mode, _, ident, _) = p.node {
f(binding_mode, p.hir_id, p.span, ident);
Expand All @@ -81,59 +79,53 @@ impl hir::Pat {
/// `match foo() { Some(a) => (), None => () }`.
///
/// When encountering an or-pattern `p_0 | ... | p_n` only `p_0` will be visited.
pub fn each_binding_or_first<F>(&self, c: &mut F)
where F: FnMut(hir::BindingAnnotation, HirId, Span, ast::Ident),
{
match &self.node {
PatKind::Binding(bm, _, ident, sub) => {
c(*bm, self.hir_id, self.span, *ident);
sub.iter().for_each(|p| p.each_binding_or_first(c));
}
PatKind::Or(ps) => ps[0].each_binding_or_first(c),
PatKind::Struct(_, fs, _) => fs.iter().for_each(|f| f.pat.each_binding_or_first(c)),
PatKind::TupleStruct(_, ps, _) | PatKind::Tuple(ps, _) => {
ps.iter().for_each(|p| p.each_binding_or_first(c));
}
PatKind::Box(p) | PatKind::Ref(p, _) => p.each_binding_or_first(c),
PatKind::Slice(before, slice, after) => {
before.iter()
.chain(slice.iter())
.chain(after.iter())
.for_each(|p| p.each_binding_or_first(c));
pub fn each_binding_or_first(
&self,
f: &mut impl FnMut(hir::BindingAnnotation, HirId, Span, ast::Ident),
) {
self.walk(|p| match &p.node {
PatKind::Or(ps) => {
ps[0].each_binding_or_first(f);
false
},
PatKind::Binding(bm, _, ident, _) => {
f(*bm, p.hir_id, p.span, *ident);
true
}
PatKind::Wild | PatKind::Lit(_) | PatKind::Range(..) | PatKind::Path(_) => {}
}
_ => true,
})
}

/// Checks if the pattern contains any patterns that bind something to
/// an ident, e.g., `foo`, or `Foo(foo)` or `foo @ Bar(..)`.
pub fn contains_bindings(&self) -> bool {
let mut contains_bindings = false;
self.walk(|p| {
if let PatKind::Binding(..) = p.node {
contains_bindings = true;
false // there's at least one binding, can short circuit now.
} else {
true
}
});
contains_bindings
self.satisfies(|p| match p.node {
PatKind::Binding(..) => true,
_ => false,
})
}

/// Checks if the pattern contains any patterns that bind something to
/// an ident or wildcard, e.g., `foo`, or `Foo(_)`, `foo @ Bar(..)`,
pub fn contains_bindings_or_wild(&self) -> bool {
let mut contains_bindings = false;
self.walk(|p| {
match p.node {
PatKind::Binding(..) | PatKind::Wild => {
contains_bindings = true;
false // there's at least one binding/wildcard, can short circuit now.
}
_ => true
self.satisfies(|p| match p.node {
PatKind::Binding(..) | PatKind::Wild => true,
_ => false,
})
}

/// Checks if the pattern satisfies the given predicate on some sub-pattern.
fn satisfies(&self, pred: impl Fn(&Self) -> bool) -> bool {
let mut satisfies = false;
self.walk_short(|p| {
if pred(p) {
satisfies = true;
false // Found one, can short circuit now.
} else {
true
}
});
contains_bindings
satisfies
}

pub fn simple_ident(&self) -> Option<ast::Ident> {
Expand All @@ -147,20 +139,20 @@ impl hir::Pat {
/// Returns variants that are necessary to exist for the pattern to match.
pub fn necessary_variants(&self) -> Vec<DefId> {
let mut variants = vec![];
self.walk(|p| {
match p.node {
PatKind::Path(hir::QPath::Resolved(_, ref path)) |
PatKind::TupleStruct(hir::QPath::Resolved(_, ref path), ..) |
PatKind::Struct(hir::QPath::Resolved(_, ref path), ..) => {
match path.res {
Res::Def(DefKind::Variant, id) => variants.push(id),
Res::Def(DefKind::Ctor(CtorOf::Variant, ..), id) => variants.push(id),
_ => ()
}
self.walk(|p| match &p.node {
PatKind::Or(_) => false,
PatKind::Path(hir::QPath::Resolved(_, path)) |
PatKind::TupleStruct(hir::QPath::Resolved(_, path), ..) |
PatKind::Struct(hir::QPath::Resolved(_, path), ..) => {
if let Res::Def(DefKind::Variant, id)
| Res::Def(DefKind::Ctor(CtorOf::Variant, ..), id)
= path.res
{
variants.push(id);
}
_ => ()
true
}
true
_ => true,
});
variants.sort();
variants.dedup();
Expand All @@ -176,14 +168,12 @@ impl hir::Pat {
let mut result = None;
self.each_binding(|annotation, _, _, _| {
match annotation {
hir::BindingAnnotation::Ref => {
match result {
None | Some(hir::MutImmutable) => result = Some(hir::MutImmutable),
_ => (),
}
hir::BindingAnnotation::Ref => match result {
None | Some(hir::MutImmutable) => result = Some(hir::MutImmutable),
_ => {}
}
hir::BindingAnnotation::RefMut => result = Some(hir::MutMutable),
_ => (),
_ => {}
}
});
result
Expand Down
21 changes: 7 additions & 14 deletions src/librustc/middle/dead.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -259,20 +259,13 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
}

fn visit_arm(&mut self, arm: &'tcx hir::Arm) {
let pats = arm.top_pats_hack();
if let [pat] = pats {
let variants = pat.necessary_variants();

// Inside the body, ignore constructions of variants
// necessary for the pattern to match. Those construction sites
// can't be reached unless the variant is constructed elsewhere.
let len = self.ignore_variant_stack.len();
self.ignore_variant_stack.extend_from_slice(&variants);
intravisit::walk_arm(self, arm);
self.ignore_variant_stack.truncate(len);
} else {
intravisit::walk_arm(self, arm);
}
// Inside the body, ignore constructions of variants
// necessary for the pattern to match. Those construction sites
// can't be reached unless the variant is constructed elsewhere.
let len = self.ignore_variant_stack.len();
self.ignore_variant_stack.extend(arm.pat.necessary_variants());
intravisit::walk_arm(self, arm);
self.ignore_variant_stack.truncate(len);
}

fn visit_pat(&mut self, pat: &'tcx hir::Pat) {
Expand Down

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