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Implement impl Trait lifetime elision

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This commit is contained in:
Taylor Cramer 2017-12-09 21:54:58 -08:00
parent 4c2819d326
commit 018c4038c7
3 changed files with 134 additions and 55 deletions
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26
src/test/run-pass/impl-trait/lifetimes.rs
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@ -8,7 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![feature(conservative_impl_trait)]
#![feature(conservative_impl_trait, underscore_lifetimes, universal_impl_trait)]
#![allow(warnings)]
use std::fmt::Debug;
@ -32,12 +32,36 @@ fn no_params_or_lifetimes_is_static() -> impl Debug + 'static {
fn static_input_type_is_static<T: Debug + 'static>(x: T) -> impl Debug + 'static { x }
fn type_outlives_reference_lifetime<'a, T: Debug>(x: &'a T) -> impl Debug + 'a { x }
fn type_outlives_reference_lifetime_elided<T: Debug>(x: &T) -> impl Debug + '_ { x }
trait SingleRegionTrait<'a> {}
impl<'a> SingleRegionTrait<'a> for u32 {}
impl<'a> SingleRegionTrait<'a> for &'a u32 {}
struct SingleRegionStruct<'a>(&'a u32);
fn simple_type_hrtb<'b>() -> impl for<'a> SingleRegionTrait<'a> { 5 }
// FIXME(cramertj) add test after #45992 lands to ensure lint is triggered
fn elision_single_region_trait(x: &u32) -> impl SingleRegionTrait { x }
fn elision_single_region_struct(x: SingleRegionStruct) -> impl Into<SingleRegionStruct> { x }
fn closure_hrtb() -> impl for<'a> Fn(&'a u32) { |_| () }
fn closure_hr_elided() -> impl Fn(&u32) { |_| () }
fn closure_hr_elided_return() -> impl Fn(&u32) -> &u32 { |x| x }
fn closure_pass_through_elided_return(x: impl Fn(&u32) -> &u32) -> impl Fn(&u32) -> &u32 { x }
fn closure_pass_through_reference_elided(x: &impl Fn(&u32) -> &u32) -> &impl Fn(&u32) -> &u32 { x }
fn pass_through_elision(x: &u32) -> impl Into<&u32> { x }
fn pass_through_elision_with_fn_ptr(x: &fn(&u32) -> &u32) -> impl Into<&fn(&u32) -> &u32> { x }
fn pass_through_elision_with_fn_path<T: Fn(&u32) -> &u32>(
x: &T
) -> impl Into<&impl Fn(&u32) -> &u32> { x }
// FIXME(cramertj) Currently ICEing, part of issue #46685:
// fn foo(x: &impl Debug) -> impl Into<&impl Debug> { x }
// Works:
fn foo_no_outer_impl(x: &impl Debug) -> &impl Debug { x }
fn foo_explicit_arg<T: Debug>(x: &T) -> impl Into<&impl Debug> { x }
fn mixed_lifetimes<'a>() -> impl for<'b: 'a> Fn(&'b u32) { |_| () }
fn mixed_as_static() -> impl Fn(&'static u32) { mixed_lifetimes() }