429 lines
17 KiB
Rust
429 lines
17 KiB
Rust
use crate::ImplTraitPosition;
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use super::errors::{GenericTypeWithParentheses, UseAngleBrackets};
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use super::ResolverAstLoweringExt;
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use super::{GenericArgsCtor, LifetimeRes, ParenthesizedGenericArgs};
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use super::{ImplTraitContext, LoweringContext, ParamMode};
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use rustc_ast::{self as ast, *};
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use rustc_hir as hir;
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use rustc_hir::def::{DefKind, PartialRes, Res};
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use rustc_hir::GenericArg;
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use rustc_span::symbol::{kw, sym, Ident};
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use rustc_span::{BytePos, Span, DUMMY_SP};
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use smallvec::{smallvec, SmallVec};
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impl<'a, 'hir> LoweringContext<'a, 'hir> {
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#[instrument(level = "trace", skip(self))]
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pub(crate) fn lower_qpath(
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&mut self,
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id: NodeId,
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qself: &Option<ptr::P<QSelf>>,
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p: &Path,
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param_mode: ParamMode,
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itctx: &ImplTraitContext,
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// constness of the impl/bound if this is a trait path
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constness: Option<ast::Const>,
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) -> hir::QPath<'hir> {
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let qself_position = qself.as_ref().map(|q| q.position);
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let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
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let partial_res =
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self.resolver.get_partial_res(id).unwrap_or_else(|| PartialRes::new(Res::Err));
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let base_res = partial_res.base_res();
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let unresolved_segments = partial_res.unresolved_segments();
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let path_span_lo = p.span.shrink_to_lo();
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let proj_start = p.segments.len() - unresolved_segments;
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let path = self.arena.alloc(hir::Path {
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res: self.lower_res(base_res),
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segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
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|(i, segment)| {
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let param_mode = match (qself_position, param_mode) {
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(Some(j), ParamMode::Optional) if i < j => {
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// This segment is part of the trait path in a
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// qualified path - one of `a`, `b` or `Trait`
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// in `<X as a::b::Trait>::T::U::method`.
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ParamMode::Explicit
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}
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_ => param_mode,
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};
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let parenthesized_generic_args = match base_res {
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// `a::b::Trait(Args)`
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Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
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ParenthesizedGenericArgs::ParenSugar
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}
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// `a::b::Trait(Args)::TraitItem`
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Res::Def(DefKind::AssocFn, _)
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| Res::Def(DefKind::AssocConst, _)
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| Res::Def(DefKind::AssocTy, _)
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if i + 2 == proj_start =>
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{
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ParenthesizedGenericArgs::ParenSugar
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}
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// Avoid duplicated errors.
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Res::Err => ParenthesizedGenericArgs::ParenSugar,
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// An error
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_ => ParenthesizedGenericArgs::Err,
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};
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self.lower_path_segment(
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p.span,
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segment,
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param_mode,
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parenthesized_generic_args,
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itctx,
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// if this is the last segment, add constness to the trait path
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if i == proj_start - 1 { constness } else { None },
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)
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},
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)),
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span: self.lower_span(
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p.segments[..proj_start]
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.last()
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.map_or(path_span_lo, |segment| path_span_lo.to(segment.span())),
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),
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});
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// Simple case, either no projections, or only fully-qualified.
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// E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
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if unresolved_segments == 0 {
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return hir::QPath::Resolved(qself, path);
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}
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// Create the innermost type that we're projecting from.
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let mut ty = if path.segments.is_empty() {
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// If the base path is empty that means there exists a
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// syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
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qself.expect("missing QSelf for <T>::...")
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} else {
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// Otherwise, the base path is an implicit `Self` type path,
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// e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
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// `<I as Iterator>::Item::default`.
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let new_id = self.next_id();
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self.arena.alloc(self.ty_path(new_id, path.span, hir::QPath::Resolved(qself, path)))
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};
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// Anything after the base path are associated "extensions",
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// out of which all but the last one are associated types,
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// e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
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// * base path is `std::vec::Vec<T>`
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// * "extensions" are `IntoIter`, `Item` and `clone`
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// * type nodes are:
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// 1. `std::vec::Vec<T>` (created above)
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// 2. `<std::vec::Vec<T>>::IntoIter`
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// 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
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// * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
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for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
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let hir_segment = self.arena.alloc(self.lower_path_segment(
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p.span,
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segment,
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param_mode,
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ParenthesizedGenericArgs::Err,
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itctx,
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None,
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));
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let qpath = hir::QPath::TypeRelative(ty, hir_segment);
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// It's finished, return the extension of the right node type.
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if i == p.segments.len() - 1 {
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return qpath;
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}
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// Wrap the associated extension in another type node.
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let new_id = self.next_id();
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ty = self.arena.alloc(self.ty_path(new_id, path_span_lo.to(segment.span()), qpath));
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}
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// We should've returned in the for loop above.
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self.diagnostic().span_bug(
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p.span,
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format!(
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"lower_qpath: no final extension segment in {}..{}",
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proj_start,
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p.segments.len()
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),
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);
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}
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pub(crate) fn lower_use_path(
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&mut self,
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res: SmallVec<[Res; 3]>,
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p: &Path,
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param_mode: ParamMode,
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) -> &'hir hir::UsePath<'hir> {
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self.arena.alloc(hir::UsePath {
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res,
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segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
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self.lower_path_segment(
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p.span,
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segment,
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param_mode,
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ParenthesizedGenericArgs::Err,
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&ImplTraitContext::Disallowed(ImplTraitPosition::Path),
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None,
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)
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})),
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span: self.lower_span(p.span),
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})
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}
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pub(crate) fn lower_path_segment(
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&mut self,
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path_span: Span,
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segment: &PathSegment,
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param_mode: ParamMode,
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parenthesized_generic_args: ParenthesizedGenericArgs,
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itctx: &ImplTraitContext,
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constness: Option<ast::Const>,
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) -> hir::PathSegment<'hir> {
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debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment);
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let (mut generic_args, infer_args) = if let Some(generic_args) = segment.args.as_deref() {
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match generic_args {
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GenericArgs::AngleBracketed(data) => {
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self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
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}
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GenericArgs::Parenthesized(data) => match parenthesized_generic_args {
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ParenthesizedGenericArgs::ParenSugar => {
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self.lower_parenthesized_parameter_data(data, itctx)
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}
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ParenthesizedGenericArgs::Err => {
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// Suggest replacing parentheses with angle brackets `Trait(params...)` to `Trait<params...>`
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let sub = if !data.inputs.is_empty() {
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// Start of the span to the 1st character of 1st argument
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let open_param = data.inputs_span.shrink_to_lo().to(data
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.inputs
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.first()
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.unwrap()
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.span
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.shrink_to_lo());
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// Last character position of last argument to the end of the span
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let close_param = data
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.inputs
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.last()
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.unwrap()
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.span
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.shrink_to_hi()
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.to(data.inputs_span.shrink_to_hi());
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Some(UseAngleBrackets { open_param, close_param })
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} else {
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None
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};
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self.tcx.sess.emit_err(GenericTypeWithParentheses { span: data.span, sub });
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(
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self.lower_angle_bracketed_parameter_data(
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&data.as_angle_bracketed_args(),
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param_mode,
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itctx,
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)
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.0,
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false,
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)
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}
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},
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}
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} else {
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(
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GenericArgsCtor {
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args: Default::default(),
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bindings: &[],
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parenthesized: hir::GenericArgsParentheses::No,
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span: path_span.shrink_to_hi(),
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},
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param_mode == ParamMode::Optional,
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)
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};
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if let Some(constness) = constness {
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generic_args.push_constness(self, constness);
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}
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let has_lifetimes =
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generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
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// FIXME(return_type_notation): Is this correct? I think so.
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if generic_args.parenthesized != hir::GenericArgsParentheses::ParenSugar && !has_lifetimes {
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self.maybe_insert_elided_lifetimes_in_path(
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path_span,
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segment.id,
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segment.ident.span,
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&mut generic_args,
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);
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}
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let res = self.expect_full_res(segment.id);
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let hir_id = self.lower_node_id(segment.id);
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debug!(
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"lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
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segment.ident, segment.id, hir_id,
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);
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hir::PathSegment {
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ident: self.lower_ident(segment.ident),
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hir_id,
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res: self.lower_res(res),
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infer_args,
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args: if generic_args.is_empty() && generic_args.span.is_empty() {
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None
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} else {
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Some(generic_args.into_generic_args(self))
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},
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}
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}
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fn maybe_insert_elided_lifetimes_in_path(
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&mut self,
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path_span: Span,
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segment_id: NodeId,
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segment_ident_span: Span,
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generic_args: &mut GenericArgsCtor<'hir>,
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) {
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let (start, end) = match self.resolver.get_lifetime_res(segment_id) {
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Some(LifetimeRes::ElidedAnchor { start, end }) => (start, end),
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None => return,
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Some(_) => panic!(),
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};
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let expected_lifetimes = end.as_usize() - start.as_usize();
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debug!(expected_lifetimes);
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// Note: these spans are used for diagnostics when they can't be inferred.
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// See rustc_resolve::late::lifetimes::LifetimeContext::add_missing_lifetime_specifiers_label
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let elided_lifetime_span = if generic_args.span.is_empty() {
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// If there are no brackets, use the identifier span.
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// HACK: we use find_ancestor_inside to properly suggest elided spans in paths
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// originating from macros, since the segment's span might be from a macro arg.
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segment_ident_span.find_ancestor_inside(path_span).unwrap_or(path_span)
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} else if generic_args.is_empty() {
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// If there are brackets, but not generic arguments, then use the opening bracket
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generic_args.span.with_hi(generic_args.span.lo() + BytePos(1))
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} else {
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// Else use an empty span right after the opening bracket.
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generic_args.span.with_lo(generic_args.span.lo() + BytePos(1)).shrink_to_lo()
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};
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generic_args.args.insert_many(
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0,
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(start.as_u32()..end.as_u32()).map(|i| {
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let id = NodeId::from_u32(i);
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let l = self.lower_lifetime(&Lifetime {
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id,
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ident: Ident::new(kw::Empty, elided_lifetime_span),
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});
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GenericArg::Lifetime(l)
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}),
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);
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}
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pub(crate) fn lower_angle_bracketed_parameter_data(
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&mut self,
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data: &AngleBracketedArgs,
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param_mode: ParamMode,
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itctx: &ImplTraitContext,
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) -> (GenericArgsCtor<'hir>, bool) {
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let has_non_lt_args = data.args.iter().any(|arg| match arg {
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AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))
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| AngleBracketedArg::Constraint(_) => false,
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AngleBracketedArg::Arg(ast::GenericArg::Type(_) | ast::GenericArg::Const(_)) => true,
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});
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let args = data
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.args
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.iter()
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.filter_map(|arg| match arg {
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AngleBracketedArg::Arg(arg) => Some(self.lower_generic_arg(arg, itctx)),
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AngleBracketedArg::Constraint(_) => None,
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})
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.collect();
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let bindings = self.arena.alloc_from_iter(data.args.iter().filter_map(|arg| match arg {
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AngleBracketedArg::Constraint(c) => Some(self.lower_assoc_ty_constraint(c, itctx)),
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AngleBracketedArg::Arg(_) => None,
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}));
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let ctor = GenericArgsCtor {
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args,
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bindings,
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parenthesized: hir::GenericArgsParentheses::No,
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span: data.span,
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};
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(ctor, !has_non_lt_args && param_mode == ParamMode::Optional)
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}
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fn lower_parenthesized_parameter_data(
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&mut self,
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data: &ParenthesizedArgs,
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itctx: &ImplTraitContext,
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) -> (GenericArgsCtor<'hir>, bool) {
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// Switch to `PassThrough` mode for anonymous lifetimes; this
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// means that we permit things like `&Ref<T>`, where `Ref` has
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// a hidden lifetime parameter. This is needed for backwards
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// compatibility, even in contexts like an impl header where
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// we generally don't permit such things (see #51008).
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let ParenthesizedArgs { span, inputs, inputs_span, output } = data;
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let inputs = self.arena.alloc_from_iter(inputs.iter().map(|ty| {
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self.lower_ty_direct(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitParam))
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}));
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let output_ty = match output {
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// Only allow `impl Trait` in return position. i.e.:
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// ```rust
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// fn f(_: impl Fn() -> impl Debug) -> impl Fn() -> impl Debug
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// // disallowed --^^^^^^^^^^ allowed --^^^^^^^^^^
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// ```
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FnRetTy::Ty(ty) if matches!(itctx, ImplTraitContext::ReturnPositionOpaqueTy { .. }) => {
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if self.tcx.features().impl_trait_in_fn_trait_return {
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self.lower_ty(&ty, itctx)
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} else {
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self.lower_ty(
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&ty,
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&ImplTraitContext::FeatureGated(
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ImplTraitPosition::FnTraitReturn,
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sym::impl_trait_in_fn_trait_return,
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),
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)
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}
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}
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FnRetTy::Ty(ty) => {
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self.lower_ty(&ty, &ImplTraitContext::Disallowed(ImplTraitPosition::FnTraitReturn))
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}
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FnRetTy::Default(_) => self.arena.alloc(self.ty_tup(*span, &[])),
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};
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let args = smallvec![GenericArg::Type(self.arena.alloc(self.ty_tup(*inputs_span, inputs)))];
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let binding = self.output_ty_binding(output_ty.span, output_ty);
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(
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GenericArgsCtor {
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args,
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bindings: arena_vec![self; binding],
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parenthesized: hir::GenericArgsParentheses::ParenSugar,
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span: data.inputs_span,
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},
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false,
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)
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}
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/// An associated type binding `Output = $ty`.
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pub(crate) fn output_ty_binding(
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&mut self,
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span: Span,
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ty: &'hir hir::Ty<'hir>,
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) -> hir::TypeBinding<'hir> {
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let ident = Ident::with_dummy_span(hir::FN_OUTPUT_NAME);
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let kind = hir::TypeBindingKind::Equality { term: ty.into() };
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let args = arena_vec![self;];
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let bindings = arena_vec![self;];
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let gen_args = self.arena.alloc(hir::GenericArgs {
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args,
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bindings,
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parenthesized: hir::GenericArgsParentheses::No,
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span_ext: DUMMY_SP,
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});
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hir::TypeBinding {
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hir_id: self.next_id(),
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gen_args,
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span: self.lower_span(span),
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ident,
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kind,
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}
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}
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}
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