Treat cycle errors as bug by default #145611
Description
We should treat unexpected query cycles as bugs, not user-facing errors. Ideally we'd add an attribute to queries to indicate that they are expected to cycle and otherwise ICE on cycles.
Affected queries are crate_variances or effective_visibilities.
original issue:
when fetching effective_visibilities for Adt self types of a local trait while proving a where-clause.
rust/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
Lines 2871 to 2889 in 8c32e31
This query fetches the hidden type of all opaque types
rust/compiler/rustc_privacy/src/lib.rs
Lines 1841 to 1846 in 8c32e31
introduced in #143431, cc @xizheyin @compiler-errors
trait LocalTrait {} struct SomeType; fn impls_trait<T: LocalTrait>() {} fn foo() -> impl Sized { impls_trait::<SomeType>(); }results in
error[E0391]: cycle detected when computing type of `foo::{opaque#0}` --> src/lib.rs:4:13 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^ | note: ...which requires computing type of opaque `foo::{opaque#0}`... --> src/lib.rs:4:13 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^ note: ...which requires borrow-checking `foo`... --> src/lib.rs:4:1 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^^^^^^^^^^^^^ note: ...which requires promoting constants in MIR for `foo`... --> src/lib.rs:4:1 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^^^^^^^^^^^^^ note: ...which requires checking if `foo` contains FFI-unwind calls... --> src/lib.rs:4:1 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^^^^^^^^^^^^^ note: ...which requires building MIR for `foo`... --> src/lib.rs:4:1 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^^^^^^^^^^^^^ note: ...which requires match-checking `foo`... --> src/lib.rs:4:1 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^^^^^^^^^^^^^ note: ...which requires type-checking `foo`... --> src/lib.rs:4:1 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^^^^^^^^^^^^^ = note: ...which requires checking effective visibilities... = note: ...which again requires computing type of `foo::{opaque#0}`, completing the cycle note: cycle used when checking that `foo::{opaque#0}` is well-formed --> src/lib.rs:4:13 | 4 | fn foo() -> impl Sized { | ^^^^^^^^^^ = 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 error[E0277]: the trait bound `SomeType: LocalTrait` is not satisfied --> src/lib.rs:5:19 | 5 | impls_trait::<SomeType>(); | ^^^^^^^^ the trait `LocalTrait` is not implemented for `SomeType` | help: this trait has no implementations, consider adding one --> src/lib.rs:1:1 | 1 | trait LocalTrait {} | ^^^^^^^^^^^^^^^^ note: required by a bound in `impls_trait` --> src/lib.rs:3:19 | 3 | fn impls_trait<T: LocalTrait>() {} | ^^^^^^^^^^ required by this bound in `impls_trait` note the query cycle before the actually desired error