Add 'static lifetime suggestion when GAT implied 'static requirement from HRTB #106747

yanchen4791 · 2023-01-11T22:11:14Z

Fix for issue #105507

The problem:
When generic associated types (GATs) are from higher-ranked trait bounds (HRTB), they are implied 'static requirement (see
Implied 'static requirement from higher-ranked trait bounds for more details). If the user did not explicitly specify the 'static lifetime when using the GAT, the current error message will only point out the type does not live long enough where the type is used, but not where the GAT is specified and how to fix the problem.

The solution:
Add notes at the span where the problematic GATs are specified and suggestions of how to fix the problem by adding 'static lifetime at the right spans.

rustbot · 2023-01-11T22:11:50Z

r? @petrochenkov

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yanchen4791 · 2023-01-11T22:26:22Z

r? @estebank Need to change existing src/test/ui/generic-associated-types/collectivity-regression.stderr in order to pass the tests. But I seemed not having write access the to file (see the message above). How to fix the problem?

compiler-errors · 2023-01-11T22:37:56Z

@yanchen please rebase onto current master and move the test from ./src/test/ui to the new directory ./tests/ui

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

estebank · 2023-01-17T01:41:35Z

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

+                    None
+                }
+            })
+            .collect::<Vec<_>>();


Seeing that you're only using it once afterwards, I don't think you need to collect this first, right? It can remain an iterator. Collecting has a marginal perf cost, but we can avoid it with confidence thanks to the type ownership system :)

Yes, agreed. The reason for keeping the code this way I thought was for more readability and ease of debugging.

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

compiler/rustc_middle/src/ty/sty.rs

…from HRTB

estebank · 2023-01-17T21:44:34Z

@bors r+

bors · 2023-01-17T21:44:36Z

📌 Commit aadd58e has been approved by estebank

It is now in the queue for this repository.

…tebank Add 'static lifetime suggestion when GAT implied 'static requirement from HRTB Fix for issue rust-lang#105507 The problem: When generic associated types (GATs) are from higher-ranked trait bounds (HRTB), they are implied 'static requirement (see [Implied 'static requirement from higher-ranked trait bounds](https://blog.rust-lang.org/2022/10/28/gats-stabilization.html#implied-static-requirement-from-higher-ranked-trait-bounds) for more details). If the user did not explicitly specify the `'static` lifetime when using the GAT, the current error message will only point out the type `does not live long enough` where the type is used, but not where the GAT is specified and how to fix the problem. The solution: Add notes at the span where the problematic GATs are specified and suggestions of how to fix the problem by adding `'static` lifetime at the right spans.

…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#106244 (Improve Markdown styling in README) - rust-lang#106747 (Add 'static lifetime suggestion when GAT implied 'static requirement from HRTB) - rust-lang#106873 (dont randomly use `_` to print out const generic arguments) - rust-lang#106992 (Remove unused `#![feature(box_syntax)]` in `alloc`) - rust-lang#106995 (bump failing assembly & codegen tests from LLVM 14 to LLVM 15) - rust-lang#106996 (rustdoc: instead of `.setting-name { width: 100% }`, use default div CSS) - rust-lang#106997 (Add heapsort fallback in `select_nth_unstable`) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned petrochenkov Jan 11, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jan 11, 2023

rustbot assigned estebank and unassigned petrochenkov Jan 11, 2023

yanchen4791 force-pushed the issue-105507-fix branch from b2fe495 to aaf1e98 Compare January 11, 2023 22:31

yanchen4791 force-pushed the issue-105507-fix branch 2 times, most recently from ee8c86d to 9a90b5a Compare January 12, 2023 02:49