Handle anon lifetime arg being returned with named lifetime return type#45751

estebank · 2017-11-04T00:36:18Z

When there's a lifetime mismatch between an argument with an anonymous
lifetime being returned in a method with a return type that has a named
lifetime, show specialized lifetime error pointing at argument with a
hint to give it an explicit lifetime matching the return type.

error[E0621]: explicit lifetime required in the type of `other`
  --> file2.rs:21:21
   |
17 |     fn bar(&self, other: Foo) -> Foo<'a> {
   |                   ----- consider changing the type of `other` to `Foo<'a>`
...
21 |                     other
   |                     ^^^^^ lifetime `'a` required

Follow up to #44124 and #42669. Fix #44684.

rust-highfive · 2017-11-04T00:36:22Z

r? @eddyb

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eddyb · 2017-11-04T09:55:49Z

r? @nikomatsakis

When there's a lifetime mismatch between an argument with an anonymous lifetime being returned in a method with a return type that has a named lifetime, show specialized lifetime error pointing at argument with a hint to give it an explicit lifetime matching the return type. ``` error[E0621]: explicit lifetime required in the type of `other` --> file2.rs:21:21 | 17 | fn bar(&self, other: Foo) -> Foo<'a> { | ----- consider changing the type of `other` to `Foo<'a>` ... 21 | other | ^^^^^ lifetime `'a` required ``` Follow up to rust-lang#44124 and rust-lang#42669.

nikomatsakis

Lookin' good. I left a few comments regarding the names of the tests but r=me otherwise.

nikomatsakis · 2017-11-06T18:53:01Z

src/librustc/infer/error_reporting/different_lifetimes.rs

+    /// It has been extended for the case of structs too.
+    ///
+    /// Consider the example
+    ///


nikomatsakis · 2017-11-06T18:53:20Z

src/librustc/infer/error_reporting/named_anon_conflict.rs

-    // the function arguments consist of a named region and an anonymous
-    // region and corresponds to `ConcreteFailure(..)`
+    /// Generate an error message for when the function arguments consist of a named region and
+    /// an anonymous region and corresponds to `ConcreteFailure(..)`


Improved, but could be better still =)

nikomatsakis · 2017-11-06T19:00:13Z

src/test/ui/lifetime-errors/ex3-both-anon-regions-earlybound-regions.stderr

   |
 13 | fn baz<'a, 'b, T>(x: &mut Vec<&'a T>, y: &T)
-   |                               -----      -- these two types are declared with different lifetimes...
+   |                                       - consider changing the type of `y` to `&'a T`


It seems to me that this test is misnamed. It is called "both-anon-regions", but, in fact, one of the regions is not anomymous. Maybe rename to something like ex2a-push-one-existing-name-early-bound.rs? (To be honest, the exN- naming scheme is not doing it for me, since it's not clear what list of tests these numbers derive from.)

nikomatsakis · 2017-11-06T19:01:12Z

src/test/ui/lifetime-errors/ex4-anon-named-regions.rs

+}
+
+impl<'a> Foo<'a> {
+    fn bar(&self, other: Foo) -> Foo<'a> {


maybe rename to ex1-return-one-existing-name-early-bound-in-struct or something?

estebank · 2017-11-07T05:22:12Z

@nikomatsakis updated

@bors r=nikomatsakis rollup

bors · 2017-11-07T05:22:15Z

📌 Commit 805333b has been approved by nikomatsakis

Handle anon lifetime arg being returned with named lifetime return type When there's a lifetime mismatch between an argument with an anonymous lifetime being returned in a method with a return type that has a named lifetime, show specialized lifetime error pointing at argument with a hint to give it an explicit lifetime matching the return type. ``` error[E0621]: explicit lifetime required in the type of `other` --> file2.rs:21:21 | 17 | fn bar(&self, other: Foo) -> Foo<'a> { | ----- consider changing the type of `other` to `Foo<'a>` ... 21 | other | ^^^^^ lifetime `'a` required ``` Follow up to rust-lang#44124 and rust-lang#42669. Fix rust-lang#44684.

Rollup of 9 pull requests - Successful merges: #45470, #45588, #45682, #45714, #45751, #45764, #45778, #45782, #45784 - Failed merges:

rust-highfive assigned eddyb Nov 4, 2017

estebank force-pushed the issue-44684 branch from dca3457 to 44191d0 Compare November 4, 2017 00:46

kennytm added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Nov 4, 2017

rust-highfive assigned nikomatsakis and unassigned eddyb Nov 4, 2017

estebank force-pushed the issue-44684 branch 2 times, most recently from cfc9c2f to d3edb01 Compare November 5, 2017 03:38

estebank force-pushed the issue-44684 branch from d3edb01 to de959af Compare November 5, 2017 17:55

nikomatsakis requested changes Nov 6, 2017

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review comments

805333b

kennytm mentioned this pull request Nov 7, 2017

Rollup of 9 pull requests #45822

Merged

bors added a commit that referenced this pull request Nov 7, 2017

Auto merge of #45822 - kennytm:rollup, r=kennytm

7f6417e

Rollup of 9 pull requests - Successful merges: #45470, #45588, #45682, #45714, #45751, #45764, #45778, #45782, #45784 - Failed merges:

bors merged commit 805333b into rust-lang:master Nov 7, 2017

estebank deleted the issue-44684 branch November 9, 2023 05:25

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Handle anon lifetime arg being returned with named lifetime return type#45751