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use std::iter::Enumerate;
use rustc_span::{Ident, Span};
use crate::def::{CtorOf, DefKind, Res};
use crate::def_id::{DefId, DefIdSet};
use crate::hir::{self, BindingMode, ByRef, HirId, PatKind};
pub struct EnumerateAndAdjust<I> {
enumerate: Enumerate<I>,
gap_pos: usize,
gap_len: usize,
}
impl<I> Iterator for EnumerateAndAdjust<I>
where
I: Iterator,
{
type Item = (usize, <I as Iterator>::Item);
fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
self.enumerate
.next()
.map(|(i, elem)| (if i < self.gap_pos { i } else { i + self.gap_len }, elem))
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.enumerate.size_hint()
}
}
pub trait EnumerateAndAdjustIterator {
fn enumerate_and_adjust(
self,
expected_len: usize,
gap_pos: hir::DotDotPos,
) -> EnumerateAndAdjust<Self>
where
Self: Sized;
}
impl<T: ExactSizeIterator> EnumerateAndAdjustIterator for T {
fn enumerate_and_adjust(
self,
expected_len: usize,
gap_pos: hir::DotDotPos,
) -> EnumerateAndAdjust<Self>
where
Self: Sized,
{
let actual_len = self.len();
EnumerateAndAdjust {
enumerate: self.enumerate(),
gap_pos: gap_pos.as_opt_usize().unwrap_or(expected_len),
gap_len: expected_len - actual_len,
}
}
}
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(&self, mut f: impl FnMut(hir::BindingMode, HirId, Span, Ident)) {
self.walk_always(|p| {
if let PatKind::Binding(binding_mode, _, ident, _) = p.kind {
f(binding_mode, p.hir_id, p.span, ident);
}
});
}
/// Call `f` on every "binding" in a pattern, e.g., on `a` in
/// `match foo() { Some(a) => (), None => () }`.
///
/// When encountering an or-pattern `p_0 | ... | p_n` only the first non-never pattern will be
/// visited. If they're all never patterns we visit nothing, which is ok since a never pattern
/// cannot have bindings.
pub fn each_binding_or_first(&self, f: &mut impl FnMut(hir::BindingMode, HirId, Span, Ident)) {
self.walk(|p| match &p.kind {
PatKind::Or(ps) => {
for p in *ps {
if !p.is_never_pattern() {
p.each_binding_or_first(f);
break;
}
}
false
}
PatKind::Binding(bm, _, ident, _) => {
f(*bm, p.hir_id, p.span, *ident);
true
}
_ => true,
})
}
pub fn simple_ident(&self) -> Option<Ident> {
match self.kind {
PatKind::Binding(BindingMode(ByRef::No, _), _, ident, None) => Some(ident),
_ => None,
}
}
/// 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.kind {
PatKind::Or(_) => false,
PatKind::Expr(hir::PatExpr {
kind: hir::PatExprKind::Path(hir::QPath::Resolved(_, path)),
..
})
| PatKind::TupleStruct(hir::QPath::Resolved(_, path), ..)
| PatKind::Struct(hir::QPath::Resolved(_, path), ..) => {
if let Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Variant, ..), id) =
path.res
{
variants.push(id);
}
true
}
_ => true,
});
// We remove duplicates by inserting into a hash set to avoid re-ordering
// the bounds
let mut duplicates = DefIdSet::default();
variants.retain(|def_id| duplicates.insert(*def_id));
variants
}
/// Checks if the pattern contains any `ref` or `ref mut` bindings, and if
/// yes whether it contains mutable or just immutables ones.
//
// FIXME(tschottdorf): this is problematic as the HIR is being scraped, but
// ref bindings are be implicit after #42640 (default match binding modes). See issue #44848.
pub fn contains_explicit_ref_binding(&self) -> Option<hir::Mutability> {
let mut result = None;
self.each_binding(|annotation, _, _, _| match annotation {
hir::BindingMode::REF if result.is_none() => result = Some(hir::Mutability::Not),
hir::BindingMode::REF_MUT => result = Some(hir::Mutability::Mut),
_ => {}
});
result
}
}
|
