warning: trait `B` is never used --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:2:7 | 2 | trait B { | ^ | = note: `#[warn(dead_code)]` on by default warning: trait `A` is never used --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:5:7 | 5 | trait A { | ^ warning: 2 warnings emitted note: no errors encountered even though delayed bugs were created note: those delayed bugs will now be shown as internal compiler errors error: internal compiler error[E0391]: cycle detected when computing function signature of `B::f` --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:3:5 | 3 | fn f(a: A) -> A; | ^^^^^^^^^^^^^^^^ | note: ...which requires checking if trait `A` is object safe... --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:5:1 | 5 | trait A { | ^^^^^^^ note: ...which requires determining object safety of trait `A`... --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:5:1 | 5 | trait A { | ^^^^^^^ note: ...which requires computing function signature of `A::concrete`... --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:6:5 | 6 | fn concrete(b: B) -> B; | ^^^^^^^^^^^^^^^^^^^^^^^ note: ...which requires checking if trait `B` is object safe... --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:2:1 | 2 | trait B { | ^^^^^^^ note: ...which requires determining object safety of trait `B`... --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:2:1 | 2 | trait B { | ^^^^^^^ = note: ...which again requires computing function signature of `B::f`, completing the cycle note: cycle used when checking that `B` is well-formed --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:2:1 | 2 | trait B { | ^^^^^^^ = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information note: delayed at compiler/rustc_query_system/src/query/job.rs:597:16 - disabled backtrace --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:3:5 | 3 | fn f(a: A) -> A; | ^^^^^^^^^^^^^^^^ error: internal compiler error[E0782]: trait objects must include the `dyn` keyword --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:6:20 | 6 | fn concrete(b: B) -> B; | ^ | = note: `B` it is not object safe, so it can't be `dyn` note: delayed at compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs:63:17 - disabled backtrace --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:6:20 | 6 | fn concrete(b: B) -> B; | ^ help: use a new generic type parameter, constrained by `B` | 6 | fn concrete<T: B>(b: T) -> B; | ++++++ ~ help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | 6 | fn concrete(b: impl B) -> B; | ++++ error: internal compiler error[E0782]: trait objects must include the `dyn` keyword --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:6:26 | 6 | fn concrete(b: B) -> B; | ^ | note: delayed at compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs:63:17 - disabled backtrace --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:6:26 | 6 | fn concrete(b: B) -> B; | ^ help: `B` is not object safe, use `impl B` to return an opaque type, as long as you return a single underlying type | 6 | fn concrete(b: B) -> impl B; | ++++ error: internal compiler error[E0782]: trait objects must include the `dyn` keyword --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:3:13 | 3 | fn f(a: A) -> A; | ^ | = note: `A` it is not object safe, so it can't be `dyn` note: delayed at compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs:63:17 - disabled backtrace --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:3:13 | 3 | fn f(a: A) -> A; | ^ help: use a new generic type parameter, constrained by `A` | 3 | fn f<T: A>(a: T) -> A; | ++++++ ~ help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference | 3 | fn f(a: impl A) -> A; | ++++ error: internal compiler error[E0782]: trait objects must include the `dyn` keyword --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:3:19 | 3 | fn f(a: A) -> A; | ^ | note: delayed at compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs:63:17 - disabled backtrace --> /tmp/icemaker_global_tempdir.Y2ZB7VqiZYxB/rustc_testrunner_tmpdir_reporting.n6c2niMcV32C/mvce.rs:3:19 | 3 | fn f(a: A) -> A; | ^ help: `A` is not object safe, use `impl A` to return an opaque type, as long as you return a single underlying type | 3 | fn f(a: A) -> impl A; | ++++ note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md note: please make sure that you have updated to the latest nightly note: rustc 1.80.0-nightly (9e297bf54 2024-05-24) running on x86_64-unknown-linux-gnu note: compiler flags: -Z unstable-options -Z dump-mir-dir=dir query stack during panic: end of query stack