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Auto merge of #53124 - davidtwco:issue-52742, r=nikomatsakis
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region error messages involving impls are confusing

Part of #52742.

r? @nikomatsakis
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@bors
bors committed Aug 10, 2018
2 parents db1acaa + 31657c9 commit f6d43ed
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Showing 14 changed files with 95 additions and 58 deletions.
2 changes: 1 addition & 1 deletion src/librustc/infer/error_reporting/nice_region_error/named_anon_conflict.rs
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Expand Up @@ -129,7 +129,7 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
ty::BrNamed(..) => true,
_ => false,
},
ty::ReEarlyBound(_) => true,
ty::ReEarlyBound(ebr) => ebr.has_name(),
_ => false,
}
}
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8 changes: 7 additions & 1 deletion src/librustc/ty/mod.rs
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Expand Up @@ -52,7 +52,7 @@ use std::{mem, ptr};
use syntax::ast::{self, DUMMY_NODE_ID, Name, Ident, NodeId};
use syntax::attr;
use syntax::ext::hygiene::Mark;
use syntax::symbol::{Symbol, LocalInternedString, InternedString};
use syntax::symbol::{keywords, Symbol, LocalInternedString, InternedString};
use syntax_pos::{DUMMY_SP, Span};

use rustc_data_structures::accumulate_vec::IntoIter as AccIntoIter;
Expand Down Expand Up @@ -825,6 +825,12 @@ impl ty::EarlyBoundRegion {
pub fn to_bound_region(&self) -> ty::BoundRegion {
ty::BoundRegion::BrNamed(self.def_id, self.name)
}

/// Does this early bound region have a name? Early bound regions normally
/// always have names except when using anonymous lifetimes (`'_`).
pub fn has_name(&self) -> bool {
self.name != keywords::UnderscoreLifetime.name().as_interned_str()
}
}

#[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
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42 changes: 15 additions & 27 deletions src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs
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Expand Up @@ -95,8 +95,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
debug!("give_region_a_name: error_region = {:?}", error_region);
match error_region {
ty::ReEarlyBound(ebr) => {
self.highlight_named_span(tcx, error_region, &ebr.name, diag);
Some(ebr.name)
if ebr.has_name() {
self.highlight_named_span(tcx, error_region, &ebr.name, diag);
Some(ebr.name)
} else {
None
}
},

ty::ReStatic => Some(keywords::StaticLifetime.name().as_interned_str()),
Expand Down Expand Up @@ -238,17 +242,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
return Some(region_name);
}

let (_argument_name, argument_span) = self.get_argument_name_and_span_for_region(
mir, argument_index);

let region_name = self.synthesize_region_name(counter);

diag.span_label(
argument_span,
format!("lifetime `{}` appears in this argument", region_name,),
);

Some(region_name)
self.give_name_if_we_cannot_match_hir_ty(
infcx,
mir,
fr,
arg_ty,
counter,
diag,
)
}

fn give_name_if_we_can_match_hir_ty_from_argument(
Expand Down Expand Up @@ -366,14 +367,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {

search_stack.push((argument_ty, argument_hir_ty));

let mut closest_match: &hir::Ty = argument_hir_ty;

while let Some((ty, hir_ty)) = search_stack.pop() {
// While we search, also track the closet match.
if tcx.any_free_region_meets(&ty, |r| r.to_region_vid() == needle_fr) {
closest_match = hir_ty;
}

match (&ty.sty, &hir_ty.node) {
// Check if the `argument_ty` is `&'X ..` where `'X`
// is the region we are looking for -- if so, and we have a `&T`
Expand Down Expand Up @@ -448,13 +442,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
}
}

let region_name = self.synthesize_region_name(counter);
diag.span_label(
closest_match.span,
format!("lifetime `{}` appears in this type", region_name),
);

return Some(region_name);
return None;
}

/// We've found an enum/struct/union type with the substitutions
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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex2b-push-no-existing-names.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex2b-push-no-existing-names.rs:16:5
|
LL | fn foo(x: &mut Vec<Ref<i32>>, y: Ref<i32>) {
| -------- -------- lifetime `'1` appears in this type
| |
| lifetime `'2` appears in this type
| - - has type `Ref<'1, i32>`
| |
| has type `&mut std::vec::Vec<Ref<'2, i32>>`
LL | x.push(y); //~ ERROR lifetime mismatch
| ^^^^^^^^^ argument requires that `'1` must outlive `'2`

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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-both-are-structs-2.rs:16:5
|
LL | fn foo(mut x: Ref, y: Ref) {
| --- --- lifetime `'1` appears in this type
| |
| lifetime `'2` appears in this type
| ----- - has type `Ref<'_, '1>`
| |
| has type `Ref<'_, '2>`
LL | x.b = y.b; //~ ERROR lifetime mismatch
| ^^^^^^^^^ requires that `'1` must outlive `'2`

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8 changes: 4 additions & 4 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.nll.stderr
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Expand Up @@ -8,10 +8,10 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-both-are-structs-3.rs:16:5
|
LL | fn foo(mut x: Ref) {
| ---
| |
| lifetime `'1` appears in this type
| lifetime `'2` appears in this type
| -----
| |
| has type `Ref<'_, '1>`
| has type `Ref<'2, '_>`
LL | x.a = x.b; //~ ERROR lifetime mismatch
| ^^^^^^^^^ requires that `'1` must outlive `'2`

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8 changes: 4 additions & 4 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.nll.stderr
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Expand Up @@ -8,10 +8,10 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-both-are-structs-4.rs:16:5
|
LL | fn foo(mut x: Ref) {
| ---
| |
| lifetime `'1` appears in this type
| lifetime `'2` appears in this type
| -----
| |
| has type `Ref<'_, '1>`
| has type `Ref<'2, '_>`
LL | x.a = x.b; //~ ERROR lifetime mismatch
| ^^^^^^^^^ requires that `'1` must outlive `'2`

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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-both-are-structs.rs:15:5
|
LL | fn foo(mut x: Vec<Ref>, y: Ref) {
| --- --- lifetime `'1` appears in this type
| |
| lifetime `'2` appears in this type
| ----- - has type `Ref<'1>`
| |
| has type `std::vec::Vec<Ref<'2>>`
LL | x.push(y); //~ ERROR lifetime mismatch
| ^^^^^^^^^ argument requires that `'1` must outlive `'2`

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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-one-is-struct-2.rs:14:5
|
LL | fn foo(mut x: Ref, y: &u32) {
| --- - let's call the lifetime of this reference `'2`
| |
| lifetime `'1` appears in this type
| ----- - let's call the lifetime of this reference `'2`
| |
| has type `Ref<'_, '1>`
LL | y = x.b; //~ ERROR lifetime mismatch
| ^^^^^^^ requires that `'1` must outlive `'2`

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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-one-is-struct-3.rs:14:5
|
LL | fn foo(mut y: Ref, x: &u32) {
| --- - let's call the lifetime of this reference `'1`
| |
| lifetime `'2` appears in this type
| ----- - let's call the lifetime of this reference `'1`
| |
| has type `Ref<'_, '2>`
LL | y.b = x; //~ ERROR lifetime mismatch
| ^^^^^^^ requires that `'1` must outlive `'2`

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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-one-is-struct-4.rs:14:5
|
LL | fn foo(mut y: Ref, x: &u32) {
| --- - let's call the lifetime of this reference `'1`
| |
| lifetime `'2` appears in this type
| ----- - let's call the lifetime of this reference `'1`
| |
| has type `Ref<'_, '2>`
LL | y.b = x; //~ ERROR lifetime mismatch
| ^^^^^^^ requires that `'1` must outlive `'2`

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6 changes: 3 additions & 3 deletions src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct.nll.stderr
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Expand Up @@ -8,9 +8,9 @@ error: unsatisfied lifetime constraints
--> $DIR/ex3-both-anon-regions-one-is-struct.rs:17:5
|
LL | fn foo(mut x: Ref, y: &u32) {
| --- - let's call the lifetime of this reference `'1`
| |
| lifetime `'2` appears in this type
| ----- - let's call the lifetime of this reference `'1`
| |
| has type `Ref<'_, '2>`
LL | x.b = y; //~ ERROR lifetime mismatch
| ^^^^^^^ requires that `'1` must outlive `'2`

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31 changes: 31 additions & 0 deletions src/test/ui/nll/issue-52742.rs
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@@ -0,0 +1,31 @@
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![feature(nll)]
#![feature(in_band_lifetimes)]
#![feature(impl_header_lifetime_elision)]

struct Foo<'a, 'b> {
x: &'a u32,
y: &'b u32,
}

struct Bar<'b> {
z: &'b u32
}

impl Foo<'_, '_> {
fn take_bar(&mut self, b: Bar<'_>) {
self.y = b.z
//~^ ERROR unsatisfied lifetime constraints
}
}

fn main() { }
12 changes: 12 additions & 0 deletions src/test/ui/nll/issue-52742.stderr
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@@ -0,0 +1,12 @@
error: unsatisfied lifetime constraints
--> $DIR/issue-52742.rs:26:9
|
LL | fn take_bar(&mut self, b: Bar<'_>) {
| --------- -- let's call this `'1`
| |
| has type `&mut Foo<'_, '2>`
LL | self.y = b.z
| ^^^^^^^^^^^^ requires that `'1` must outlive `'2`

error: aborting due to previous error

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