Account for type alias projections in E0308 "expected/found" shortening logic by estebank · Pull Request #159189 · rust-lang/rust

estebank · 2026-07-12T19:14:51Z

When encountering a E0308 error involving ty::Projections, highlight only the sub-parts that are actually relevant:

error[E0308]: mismatched types
  --> tests/ui/associated-types/long-type-E0308.rs:19:5
   |
16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> {
   |                                    ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type
...
19 |     value.assoc().assoc().assoc().wrap(value.assoc().assoc())
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
   |
   = note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
              found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>`
   = note: an associated type was expected, but a different one was found
   = note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt'
   = note: consider using `--verbose` to print the full type name to the console

Fix #159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals:

error[E0308]: mismatched types
  --> $DIR/long-type-E0308.rs:30:5
   |
LL |   ) -> <
   |  ______-
LL | |     <
LL | |         <T::Wrapper<T> as FooBar>::Assoc as FooBar
LL | |     >::Assoc as FooBar
LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc>
   | |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type
...
LL |       value...oc())
   |       ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc`
   |
   = note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>`
              found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>`
   = note: an associated type was expected, but a different one was found
   = note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt'
   = note: consider using `--verbose` to print the full type name to the console

r? @chenyukang

…ng logic When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant: ``` error[E0308]: mismatched types --> tests/ui/associated-types/long-type-E0308.rs:19:5 | 16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> { | ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type ... 19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc()) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt' = note: consider using `--verbose` to print the full type name to the console ``` Deduplicate param highlighting logic. Account for type param difference in trait in E0308 highlighting.

rustbot · 2026-07-17T23:53:54Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

chenyukang · 2026-07-18T01:50:02Z

No other issues except two trivial one.
r=me after resolve it.

estebank · 2026-07-18T04:16:02Z

@bors r=chenyukang

rust-bors · 2026-07-18T04:16:05Z

📌 Commit 068c52f has been approved by chenyukang

It is now in the queue for this repository.

@chenyukang

Account for type alias projections in E0308 "expected/found" shortening logic When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant: ``` error[E0308]: mismatched types --> tests/ui/associated-types/long-type-E0308.rs:19:5 | 16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> { | ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type ... 19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc()) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt' = note: consider using `--verbose` to print the full type name to the console ``` Fix rust-lang#159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals: ``` error[E0308]: mismatched types --> $DIR/long-type-E0308.rs:30:5 | LL | ) -> < | ______- LL | | < LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar LL | | >::Assoc as FooBar LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc> | |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type ... LL | value...oc()) | ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>` found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt' = note: consider using `--verbose` to print the full type name to the console ``` r? @chenyukang

…uwer Rollup of 5 pull requests Successful merges: - #159189 (Account for type alias projections in E0308 "expected/found" shortening logic) - #158545 (Move `std::io::read_to_string` to `alloc::io`) - #159328 (tests/assembly-llvm: pin frame pointer in issue-141649 aarch64 test) - #159470 (Fix string indexing in diagnostic format strings) - #159500 (Move compiletest CLI parsing to `cli.rs`)

@chenyukang

Account for type alias projections in E0308 "expected/found" shortening logic When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant: ``` error[E0308]: mismatched types --> tests/ui/associated-types/long-type-E0308.rs:19:5 | 16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> { | ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type ... 19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc()) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt' = note: consider using `--verbose` to print the full type name to the console ``` Fix #159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals: ``` error[E0308]: mismatched types --> $DIR/long-type-E0308.rs:30:5 | LL | ) -> < | ______- LL | | < LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar LL | | >::Assoc as FooBar LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc> | |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type ... LL | value...oc()) | ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>` found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt' = note: consider using `--verbose` to print the full type name to the console ``` r? @chenyukang

rust-bors · 2026-07-18T11:02:52Z

💔 Test for b356d7c failed: CI. Failed job:

auto - aarch64-msvc-1 (web logs, enhanced plaintext logs)

JonathanBrouwer · 2026-07-18T11:16:56Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #159501 (comment)

rust-bors · 2026-07-18T11:17:03Z

This PR was contained in a rollup (#159501), which was unapproved.

View changes since this unapproval

chenyukang · 2026-07-19T01:05:21Z

ah, I got it, you need add these files for windows:

long-type-E0308.short-color.windows.svg
long-type-E0308.shortest-color.windows.svg

but if you don't have a windows dev machine, seems it's not easy to generate them 😅

…e highlighted string instead Introduce a mechanism to textually trim highlighted strings, so that we can print out "expected/found" note with shorter output while still keeping the highlighted inner parts. ``` error[E0308]: mismatched types --> $DIR/long-type-E0308.rs:30:5 | LL | ) -> < | ______- LL | | < LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar LL | | >::Assoc as FooBar LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc> | |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type ... LL | value...oc()) | ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>` found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt' = note: consider using `--verbose` to print the full type name to the console ```

estebank · 2026-07-20T14:44:49Z

@bors r=chenyukang

Restricted the color tests to linux-only. The textual ones still happen everywhere.

rust-bors · 2026-07-20T14:44:52Z

📌 Commit d0cfd66 has been approved by chenyukang

It is now in the queue for this repository.

…uwer Rollup of 18 pull requests Successful merges: - #159600 (`rust-analyzer` subtree update) - #158046 (proc_macro: preserve file module spans for inner attrs) - #159000 (Small cleanups to the incr comp session code) - #159189 (Account for type alias projections in E0308 "expected/found" shortening logic) - #159449 (Enable single Location to issue multiple borrows) - #159544 (Suggest valid command-line crate names) - #159587 (Improve `AttrItem::span`) - #159594 (feat(rustc_hir_typeck): suggest `impl Fn` return for capturing closures) - #159597 (std: use `arc4random_buf` from libc) - #159599 (Resolver: Record at least 1 ambiguous trait if main decl is not a trait.) - #158061 (Make `pin!()` more foolproof.) - #159460 (Do not mark unnormalized const aliases as rigid when normalizing param env) - #159529 (Add regression test for nested replacement ranges in `collect_tokens`) - #159571 (Remove unused bundled library lookup for the local crate) - #159585 (Minor `TokenStream` improvements) - #159586 (Separate `InterpCx` usage by `ConstAnalysis` phases) - #159602 (Remove `ItemLike`) - #159603 (Clarify `push_stream`/`push_tree`) Failed merges: - #159590 (Remove some dead code)

@chenyukang

Rollup merge of #159189 - estebank:issue-159043, r=chenyukang Account for type alias projections in E0308 "expected/found" shortening logic When encountering a E0308 error involving `ty::Projection`s, highlight only the sub-parts that are actually relevant: ``` error[E0308]: mismatched types --> tests/ui/associated-types/long-type-E0308.rs:19:5 | 16 | fn foo<'a, T: FooBar>(value: T) -> <<<T::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<<T::Assoc as FooBar>::Assoc> { | ----------------------------------------------------------------------------------------------------- expected `<<<... as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<...>` because of return type ... 19 | value.assoc().assoc().assoc().wrap(value.assoc().assoc()) | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<T> as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` found associated type `<<<<_ as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Assoc as FooBar>::Wrapper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to 'long-type-E0308.long-type-5396540309891820670.txt' = note: consider using `--verbose` to print the full type name to the console ``` Fix #159043, by including a textual type shortening logic that operates on the highlighted text on really narrow terminals: ``` error[E0308]: mismatched types --> $DIR/long-type-E0308.rs:30:5 | LL | ) -> < | ______- LL | | < LL | | <T::Wrapper<T> as FooBar>::Assoc as FooBar LL | | >::Assoc as FooBar LL | | >::Wrapper<<T::Assoc as FooBar>::Assoc> | |_______________________________________- expected `<_ as FooBar>::Wrapper<_>` because of return type ... LL | value...oc()) | ^^^^^...^^^^^ expected `really_really_really_long_module::FooBar::Wrapper`, found `really_really_really_long_module::FooBar::Assoc` | = note: expected associated type `<<<<_ as FooBar>::Wrapper<_> as...pper<_>` found associated type `<<<<_ as FooBar>::Assoc as Fo...pper<_>` = note: an associated type was expected, but a different one was found = note: the full name for the type has been written to '$TEST_BUILD_DIR/long-type-E0308.long-type-$LONG_TYPE_HASH.txt' = note: consider using `--verbose` to print the full type name to the console ``` r? @chenyukang

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Rollup of 18 pull requests #159610

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