Allow both explicit and elided lifetimes in the same impl header
(While still prohibiting explicit and in-band in the same header.)
This commit is contained in:
parent
ed45f9cbf4
commit
003c4ffa83
5 changed files with 83 additions and 29 deletions
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@ -683,9 +683,15 @@ impl<'a> LoweringContext<'a> {
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// Get the name we'll use to make the def-path. Note
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// that collisions are ok here and this shouldn't
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// really show up for end-user.
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let str_name = match hir_name {
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ParamName::Plain(ident) => ident.as_interned_str(),
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ParamName::Fresh(_) => keywords::UnderscoreLifetime.name().as_interned_str(),
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let (str_name, kind) = match hir_name {
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ParamName::Plain(ident) => (
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ident.as_interned_str(),
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hir::LifetimeParamKind::InBand,
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),
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ParamName::Fresh(_) => (
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keywords::UnderscoreLifetime.name().as_interned_str(),
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hir::LifetimeParamKind::Elided,
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),
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};
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// Add a definition for the in-band lifetime def
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@ -705,7 +711,7 @@ impl<'a> LoweringContext<'a> {
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bounds: hir_vec![],
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span,
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pure_wrt_drop: false,
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kind: hir::GenericParamKind::Lifetime { in_band: true }
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kind: hir::GenericParamKind::Lifetime { kind }
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}
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})
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.chain(in_band_ty_params.into_iter())
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@ -1452,11 +1458,15 @@ impl<'a> LoweringContext<'a> {
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lifetime.span,
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);
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let name = match name {
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hir::LifetimeName::Underscore => {
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hir::ParamName::Plain(keywords::UnderscoreLifetime.ident())
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}
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hir::LifetimeName::Param(param_name) => param_name,
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let (name, kind) = match name {
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hir::LifetimeName::Underscore => (
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hir::ParamName::Plain(keywords::UnderscoreLifetime.ident()),
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hir::LifetimeParamKind::Elided,
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),
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hir::LifetimeName::Param(param_name) => (
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param_name,
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hir::LifetimeParamKind::Explicit,
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),
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_ => bug!("expected LifetimeName::Param or ParamName::Plain"),
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};
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@ -1467,9 +1477,7 @@ impl<'a> LoweringContext<'a> {
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pure_wrt_drop: false,
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attrs: hir_vec![],
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bounds: hir_vec![],
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kind: hir::GenericParamKind::Lifetime {
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in_band: false,
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}
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kind: hir::GenericParamKind::Lifetime { kind }
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});
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}
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}
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@ -2283,7 +2291,9 @@ impl<'a> LoweringContext<'a> {
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pure_wrt_drop: attr::contains_name(¶m.attrs, "may_dangle"),
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attrs: self.lower_attrs(¶m.attrs),
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bounds,
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kind: hir::GenericParamKind::Lifetime { in_band: false }
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kind: hir::GenericParamKind::Lifetime {
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kind: hir::LifetimeParamKind::Explicit,
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}
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};
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self.is_collecting_in_band_lifetimes = was_collecting_in_band;
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@ -499,14 +499,27 @@ impl GenericBound {
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pub type GenericBounds = HirVec<GenericBound>;
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#[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
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pub enum LifetimeParamKind {
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// Indicates that the lifetime definition was explicitly declared, like:
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// `fn foo<'a>(x: &'a u8) -> &'a u8 { x }`
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Explicit,
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// Indicates that the lifetime definition was synthetically added
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// as a result of an in-band lifetime usage like:
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// `fn foo(x: &'a u8) -> &'a u8 { x }`
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InBand,
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// Indication that the lifetime was elided like both cases here:
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// `fn foo(x: &u8) -> &'_ u8 { x }`
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Elided,
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}
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#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
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pub enum GenericParamKind {
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/// A lifetime definition, eg `'a: 'b + 'c + 'd`.
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Lifetime {
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// Indicates that the lifetime definition was synthetically added
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// as a result of an in-band lifetime usage like:
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// `fn foo(x: &'a u8) -> &'a u8 { x }`
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in_band: bool,
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kind: LifetimeParamKind,
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},
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Type {
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default: Option<P<Ty>>,
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@ -207,14 +207,20 @@ impl_stable_hash_for!(struct hir::GenericParam {
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kind
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});
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impl_stable_hash_for!(enum hir::LifetimeParamKind {
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Explicit,
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InBand,
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Elided
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});
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impl<'a> HashStable<StableHashingContext<'a>> for hir::GenericParamKind {
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fn hash_stable<W: StableHasherResult>(&self,
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hcx: &mut StableHashingContext<'a>,
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hasher: &mut StableHasher<W>) {
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mem::discriminant(self).hash_stable(hcx, hasher);
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match self {
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hir::GenericParamKind::Lifetime { in_band } => {
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in_band.hash_stable(hcx, hasher);
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hir::GenericParamKind::Lifetime { kind } => {
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kind.hash_stable(hcx, hasher);
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}
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hir::GenericParamKind::Type { ref default, synthetic } => {
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default.hash_stable(hcx, hasher);
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@ -35,7 +35,7 @@ use syntax_pos::Span;
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use util::nodemap::{DefIdMap, FxHashMap, FxHashSet, NodeMap, NodeSet};
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use hir::intravisit::{self, NestedVisitorMap, Visitor};
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use hir::{self, GenericParamKind};
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use hir::{self, GenericParamKind, LifetimeParamKind};
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/// The origin of a named lifetime definition.
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///
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@ -51,8 +51,8 @@ pub enum LifetimeDefOrigin {
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impl LifetimeDefOrigin {
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fn from_param(param: &GenericParam) -> Self {
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match param.kind {
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GenericParamKind::Lifetime { in_band } => {
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if in_band {
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GenericParamKind::Lifetime { kind } => {
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if kind == LifetimeParamKind::InBand {
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LifetimeDefOrigin::InBand
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} else {
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LifetimeDefOrigin::Explicit
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@ -1087,15 +1087,15 @@ fn check_mixed_explicit_and_in_band_defs(
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tcx: TyCtxt<'_, '_, '_>,
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params: &P<[hir::GenericParam]>,
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) {
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let in_bands: Vec<_> = params.iter().filter_map(|param| match param.kind {
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GenericParamKind::Lifetime { in_band, .. } => Some((in_band, param.span)),
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let lifetime_params: Vec<_> = params.iter().filter_map(|param| match param.kind {
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GenericParamKind::Lifetime { kind, .. } => Some((kind, param.span)),
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_ => None,
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}).collect();
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let out_of_band = in_bands.iter().find(|(in_band, _)| !in_band);
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let in_band = in_bands.iter().find(|(in_band, _)| *in_band);
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let explicit = lifetime_params.iter().find(|(kind, _)| *kind == LifetimeParamKind::Explicit);
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let in_band = lifetime_params.iter().find(|(kind, _)| *kind == LifetimeParamKind::InBand);
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if let (Some((_, out_of_band_span)), Some((_, in_band_span)))
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= (out_of_band, in_band) {
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if let (Some((_, explicit_span)), Some((_, in_band_span)))
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= (explicit, in_band) {
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struct_span_err!(
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tcx.sess,
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*in_band_span,
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@ -1104,7 +1104,7 @@ fn check_mixed_explicit_and_in_band_defs(
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).span_label(
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*in_band_span,
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"in-band lifetime definition here",
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).span_label(*out_of_band_span, "explicit lifetime definition here")
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).span_label(*explicit_span, "explicit lifetime definition here")
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.emit();
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}
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}
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@ -0,0 +1,25 @@
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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// run-pass
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#![allow(warnings)]
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#![feature(impl_header_lifetime_elision)]
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// This works for functions...
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fn foo<'a>(x: &str, y: &'a str) {}
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// ...so this should work for impls
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impl<'a> Foo<&str> for &'a str {}
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trait Foo<T> {}
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fn main() {
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}
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