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Error diagnostics for associated items are different with -Z unstable-options #82637

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@jyn514

I tried this code: https://github.com/rust-lang/rust/blob/573a697a6197abaad5a2d7208dbf1bbc77f4dcf3/src/test/ui/associated-types/defaults-cyclic-fail-1.rs

I expected to see this happen: The error output is the same with and without -Z unstable-options

Instead, this happened: -Z unstable-options reports more errors than without.

diff --git a/src/test/ui/associated-types/defaults-cyclic-fail-1.stderr b/src/test/ui/associated-types/defaults-cyclic-fail-1.stderr
index 5e98520b411..c2887ccac74 100644
--- a/src/test/ui/associated-types/defaults-cyclic-fail-1.stderr
+++ b/src/test/ui/associated-types/defaults-cyclic-fail-1.stderr
@@ -4,12 +4,6 @@ error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
 LL |     type A = Box<Self::B>;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
-  --> $DIR/defaults-cyclic-fail-1.rs:32:5
-   |
-LL |     type B = &'static Self::A;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error

There are similar issues with other errors related to associated items; see 3205303 for details.

cc @matthewjasper - do you have any idea what's going on here?

Activity

  1. added
    A-diagnosticsArea: Messages for errors, warnings, and lints
    T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
    C-bugCategory: This is a bug.
    requires-nightlyThis issue requires a nightly compiler in some way. When possible, use a F-* label instead.
    on Feb 28, 2021
  2. jyn514 commented on Jun 6, 2021

    @jyn514
    MemberAuthor

    cc @estebank, this also affects the "required by this bound" diagnostic I think you recently added.

    diff --git a/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.stderr b/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.stderr
    index 919b18632e6..ba5391dd803 100644
    --- a/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.stderr
    +++ b/src/test/ui/associated-type-bounds/bounds-on-assoc-in-trait.stderr
    @@ -1,13 +1,8 @@
     error[E0277]: `<<Self as Case1>::A as Iterator>::Item` doesn't implement `Debug`
       --> $DIR/bounds-on-assoc-in-trait.rs:18:28
        |
    -LL |     type A: Iterator<Item: Debug>;
    -   |                            ^^^^^ `<<Self as Case1>::A as Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    -   |
    -  ::: $SRC_DIR/core/src/fmt/mod.rs:LL:COL
    -   |
    -LL | pub trait Debug {
    -   | --------------- required by this bound in `Debug`
    +LL |       type A: Iterator<Item: Debug>;
    +   |                              ^^^^^ `<<Self as Case1>::A as Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `Debug`
        |
        = help: the trait `Debug` is not implemented for `<<Self as Case1>::A as Iterator>::Item`
     help: consider further restricting the associated type
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    A-diagnosticsArea: Messages for errors, warnings, and lintsC-bugCategory: This is a bug.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.requires-nightlyThis issue requires a nightly compiler in some way. When possible, use a F-* label instead.

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