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use rustc_ast::ptr::P;
use rustc_ast::*;
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir as hir;
use rustc_hir::def::Res;
use rustc_span::source_map::Spanned;
use rustc_span::symbol::Ident;
use rustc_span::Span;
use super::errors::{
ArbitraryExpressionInPattern, ExtraDoubleDot, MisplacedDoubleDot, SubTupleBinding,
};
use super::{ImplTraitContext, LoweringContext, ParamMode, ResolverAstLoweringExt};
use crate::ImplTraitPosition;
impl<'a, 'hir> LoweringContext<'a, 'hir> {
pub(crate) fn lower_pat(&mut self, pattern: &Pat) -> &'hir hir::Pat<'hir> {
self.arena.alloc(self.lower_pat_mut(pattern))
}
fn lower_pat_mut(&mut self, mut pattern: &Pat) -> hir::Pat<'hir> {
ensure_sufficient_stack(|| {
// loop here to avoid recursion
let node = loop {
match &pattern.kind {
PatKind::Wild => break hir::PatKind::Wild,
PatKind::Never => break hir::PatKind::Never,
PatKind::Ident(binding_mode, ident, sub) => {
let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(s));
break self.lower_pat_ident(pattern, *binding_mode, *ident, lower_sub);
}
PatKind::Lit(e) => {
break hir::PatKind::Lit(self.lower_expr_within_pat(e, false));
}
PatKind::TupleStruct(qself, path, pats) => {
let qpath = self.lower_qpath(
pattern.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
break hir::PatKind::TupleStruct(qpath, pats, ddpos);
}
PatKind::Or(pats) => {
break hir::PatKind::Or(
self.arena.alloc_from_iter(pats.iter().map(|x| self.lower_pat_mut(x))),
);
}
PatKind::Path(qself, path) => {
let qpath = self.lower_qpath(
pattern.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
break hir::PatKind::Path(qpath);
}
PatKind::Struct(qself, path, fields, etc) => {
let qpath = self.lower_qpath(
pattern.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
let fs = self.arena.alloc_from_iter(fields.iter().map(|f| {
let hir_id = self.lower_node_id(f.id);
self.lower_attrs(hir_id, &f.attrs);
hir::PatField {
hir_id,
ident: self.lower_ident(f.ident),
pat: self.lower_pat(&f.pat),
is_shorthand: f.is_shorthand,
span: self.lower_span(f.span),
}
}));
break hir::PatKind::Struct(qpath, fs, *etc == ast::PatFieldsRest::Rest);
}
PatKind::Tuple(pats) => {
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
break hir::PatKind::Tuple(pats, ddpos);
}
PatKind::Box(inner) => {
break hir::PatKind::Box(self.lower_pat(inner));
}
PatKind::Deref(inner) => {
break hir::PatKind::Deref(self.lower_pat(inner));
}
PatKind::Ref(inner, mutbl) => {
break hir::PatKind::Ref(self.lower_pat(inner), *mutbl);
}
PatKind::Range(e1, e2, Spanned { node: end, .. }) => {
break hir::PatKind::Range(
e1.as_deref().map(|e| self.lower_expr_within_pat(e, true)),
e2.as_deref().map(|e| self.lower_expr_within_pat(e, true)),
self.lower_range_end(end, e2.is_some()),
);
}
PatKind::Slice(pats) => break self.lower_pat_slice(pats),
PatKind::Rest => {
// If we reach here the `..` pattern is not semantically allowed.
break self.ban_illegal_rest_pat(pattern.span);
}
// return inner to be processed in next loop
PatKind::Paren(inner) => pattern = inner,
PatKind::MacCall(_) => panic!("{:?} shouldn't exist here", pattern.span),
PatKind::Err(guar) => break hir::PatKind::Err(*guar),
}
};
self.pat_with_node_id_of(pattern, node)
})
}
fn lower_pat_tuple(
&mut self,
pats: &[P<Pat>],
ctx: &str,
) -> (&'hir [hir::Pat<'hir>], hir::DotDotPos) {
let mut elems = Vec::with_capacity(pats.len());
let mut rest = None;
let mut iter = pats.iter().enumerate();
for (idx, pat) in iter.by_ref() {
// Interpret the first `..` pattern as a sub-tuple pattern.
// Note that unlike for slice patterns,
// where `xs @ ..` is a legal sub-slice pattern,
// it is not a legal sub-tuple pattern.
match &pat.kind {
// Found a sub-tuple rest pattern
PatKind::Rest => {
rest = Some((idx, pat.span));
break;
}
// Found a sub-tuple pattern `$binding_mode $ident @ ..`.
// This is not allowed as a sub-tuple pattern
PatKind::Ident(_, ident, Some(sub)) if sub.is_rest() => {
let sp = pat.span;
self.dcx().emit_err(SubTupleBinding {
span: sp,
ident_name: ident.name,
ident: *ident,
ctx,
});
}
_ => {}
}
// It was not a sub-tuple pattern so lower it normally.
elems.push(self.lower_pat_mut(pat));
}
for (_, pat) in iter {
// There was a previous sub-tuple pattern; make sure we don't allow more...
if pat.is_rest() {
// ...but there was one again, so error.
self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
} else {
elems.push(self.lower_pat_mut(pat));
}
}
(self.arena.alloc_from_iter(elems), hir::DotDotPos::new(rest.map(|(ddpos, _)| ddpos)))
}
/// Lower a slice pattern of form `[pat_0, ..., pat_n]` into
/// `hir::PatKind::Slice(before, slice, after)`.
///
/// When encountering `($binding_mode $ident @)? ..` (`slice`),
/// this is interpreted as a sub-slice pattern semantically.
/// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`.
fn lower_pat_slice(&mut self, pats: &[P<Pat>]) -> hir::PatKind<'hir> {
let mut before = Vec::new();
let mut after = Vec::new();
let mut slice = None;
let mut prev_rest_span = None;
// Lowers `$bm $ident @ ..` to `$bm $ident @ _`.
let lower_rest_sub = |this: &mut Self, pat, &ann, &ident, sub| {
let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
let node = this.lower_pat_ident(pat, ann, ident, lower_sub);
this.pat_with_node_id_of(pat, node)
};
let mut iter = pats.iter();
// Lower all the patterns until the first occurrence of a sub-slice pattern.
for pat in iter.by_ref() {
match &pat.kind {
// Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
PatKind::Rest => {
prev_rest_span = Some(pat.span);
slice = Some(self.pat_wild_with_node_id_of(pat));
break;
}
// Found a sub-slice pattern `$binding_mode $ident @ ..`.
// Record, lower it to `$binding_mode $ident @ _`, and stop here.
PatKind::Ident(ann, ident, Some(sub)) if sub.is_rest() => {
prev_rest_span = Some(sub.span);
slice = Some(self.arena.alloc(lower_rest_sub(self, pat, ann, ident, sub)));
break;
}
// It was not a subslice pattern so lower it normally.
_ => before.push(self.lower_pat_mut(pat)),
}
}
// Lower all the patterns after the first sub-slice pattern.
for pat in iter {
// There was a previous subslice pattern; make sure we don't allow more.
let rest_span = match &pat.kind {
PatKind::Rest => Some(pat.span),
PatKind::Ident(ann, ident, Some(sub)) if sub.is_rest() => {
// #69103: Lower into `binding @ _` as above to avoid ICEs.
after.push(lower_rest_sub(self, pat, ann, ident, sub));
Some(sub.span)
}
_ => None,
};
if let Some(rest_span) = rest_span {
// We have e.g., `[a, .., b, ..]`. That's no good, error!
self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
} else {
// Lower the pattern normally.
after.push(self.lower_pat_mut(pat));
}
}
hir::PatKind::Slice(
self.arena.alloc_from_iter(before),
slice,
self.arena.alloc_from_iter(after),
)
}
fn lower_pat_ident(
&mut self,
p: &Pat,
annotation: BindingMode,
ident: Ident,
lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>,
) -> hir::PatKind<'hir> {
match self.resolver.get_partial_res(p.id).map(|d| d.expect_full_res()) {
// `None` can occur in body-less function signatures
res @ (None | Some(Res::Local(_))) => {
let canonical_id = match res {
Some(Res::Local(id)) => id,
_ => p.id,
};
hir::PatKind::Binding(
annotation,
self.lower_node_id(canonical_id),
self.lower_ident(ident),
lower_sub(self),
)
}
Some(res) => {
let hir_id = self.next_id();
let res = self.lower_res(res);
hir::PatKind::Path(hir::QPath::Resolved(
None,
self.arena.alloc(hir::Path {
span: self.lower_span(ident.span),
res,
segments: arena_vec![self; hir::PathSegment::new(self.lower_ident(ident), hir_id, res)],
}),
))
}
}
}
fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
self.arena.alloc(self.pat_with_node_id_of(p, hir::PatKind::Wild))
}
/// Construct a `Pat` with the `HirId` of `p.id` lowered.
fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> hir::Pat<'hir> {
hir::Pat {
hir_id: self.lower_node_id(p.id),
kind,
span: self.lower_span(p.span),
default_binding_modes: true,
}
}
/// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
pub(crate) fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
self.dcx().emit_err(ExtraDoubleDot { span: sp, prev_span: prev_sp, ctx });
}
/// Used to ban the `..` pattern in places it shouldn't be semantically.
fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind<'hir> {
self.dcx().emit_err(MisplacedDoubleDot { span: sp });
// We're not in a list context so `..` can be reasonably treated
// as `_` because it should always be valid and roughly matches the
// intent of `..` (notice that the rest of a single slot is that slot).
hir::PatKind::Wild
}
fn lower_range_end(&mut self, e: &RangeEnd, has_end: bool) -> hir::RangeEnd {
match *e {
RangeEnd::Excluded if has_end => hir::RangeEnd::Excluded,
// No end; so `X..` behaves like `RangeFrom`.
RangeEnd::Excluded | RangeEnd::Included(_) => hir::RangeEnd::Included,
}
}
/// Matches `'-' lit | lit (cf. parser::Parser::parse_literal_maybe_minus)`,
/// or paths for ranges.
//
// FIXME: do we want to allow `expr -> pattern` conversion to create path expressions?
// That means making this work:
//
// ```rust,ignore (FIXME)
// struct S;
// macro_rules! m {
// ($a:expr) => {
// let $a = S;
// }
// }
// m!(S);
// ```
fn lower_expr_within_pat(&mut self, expr: &Expr, allow_paths: bool) -> &'hir hir::Expr<'hir> {
match &expr.kind {
ExprKind::Lit(..)
| ExprKind::ConstBlock(..)
| ExprKind::IncludedBytes(..)
| ExprKind::Err(_)
| ExprKind::Dummy => {}
ExprKind::Path(..) if allow_paths => {}
ExprKind::Unary(UnOp::Neg, inner) if matches!(inner.kind, ExprKind::Lit(_)) => {}
_ => {
let pattern_from_macro = expr.is_approximately_pattern();
let guar = self.dcx().emit_err(ArbitraryExpressionInPattern {
span: expr.span,
pattern_from_macro_note: pattern_from_macro,
});
return self.arena.alloc(self.expr_err(expr.span, guar));
}
}
self.lower_expr(expr)
}
}