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Rollup merge of #74991 - JulianKnodt:74199, r=lcnr
Fix Const-Generic Cycle ICE #74199 This PR intends to fix the bug in Issue #74199 by following the suggestion provided of ignoring the error that causes the ICE. This does not fix the underlying cycle detection issue, but fixes the ICE. Also adds a test to check that it doesn't causes an ICE but returns a valid error for now. r? @lcnr Edit: Also it's funny how this PR number is an anagram of the issue number
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‎src/librustc_typeck/variance/constraints.rs

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@@ -161,6 +161,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
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self.add_constraints_from_sig(current_item, tcx.fn_sig(def_id), self.covariant);
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}
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ty::Error(_) => {}
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_ => {
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span_bug!(
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tcx.def_span(def_id),

‎src/test/ui/const-generics/nested-type.rs

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#![feature(const_generics)]
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#![allow(incomplete_features)]
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struct Foo<const N: [u8; {
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//~^ ERROR cycle detected
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//~| ERROR cycle detected
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struct Foo<const N: usize>;
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impl<const N: usize> Foo<N> {
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fn value() -> usize {
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N
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}
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}
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Foo::<17>::value()
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}]>;
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fn main() {}

‎src/test/ui/const-generics/nested-type.stderr

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error[E0391]: cycle detected when computing type of `Foo`
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--> $DIR/nested-type.rs:4:1
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|
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LL | struct Foo<const N: [u8; {
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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|
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note: ...which requires computing type of `Foo::N`...
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--> $DIR/nested-type.rs:4:18
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|
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LL | struct Foo<const N: [u8; {
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| ^
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note: ...which requires const-evaluating + checking `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires const-evaluating + checking `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires const-evaluating `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires type-checking `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires computing the variances of `Foo::{{constant}}#0::Foo`...
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--> $DIR/nested-type.rs:7:5
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|
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LL | struct Foo<const N: usize>;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: ...which requires computing the variances for items in this crate...
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= note: ...which again requires computing type of `Foo`, completing the cycle
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note: cycle used when collecting item types in top-level module
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--> $DIR/nested-type.rs:1:1
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|
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LL | / #![feature(const_generics)]
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LL | | #![allow(incomplete_features)]
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LL | |
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LL | | struct Foo<const N: [u8; {
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... |
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LL | |
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LL | | fn main() {}
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| |____________^
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error[E0391]: cycle detected when computing type of `Foo`
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--> $DIR/nested-type.rs:4:1
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|
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LL | struct Foo<const N: [u8; {
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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|
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note: ...which requires computing type of `Foo::N`...
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--> $DIR/nested-type.rs:4:18
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|
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LL | struct Foo<const N: [u8; {
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| ^
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note: ...which requires const-evaluating + checking `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires const-evaluating + checking `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires const-evaluating `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires type-checking `Foo::{{constant}}#0`...
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--> $DIR/nested-type.rs:4:26
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|
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LL | struct Foo<const N: [u8; {
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| __________________________^
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LL | |
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LL | |
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LL | | struct Foo<const N: usize>;
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... |
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LL | | Foo::<17>::value()
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LL | | }]>;
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| |_^
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note: ...which requires computing the variances of `Foo::{{constant}}#0::Foo`...
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--> $DIR/nested-type.rs:7:5
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|
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LL | struct Foo<const N: usize>;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: ...which requires computing the variances for items in this crate...
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= note: ...which again requires computing type of `Foo`, completing the cycle
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note: cycle used when collecting item types in top-level module
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--> $DIR/nested-type.rs:1:1
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|
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LL | / #![feature(const_generics)]
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LL | | #![allow(incomplete_features)]
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LL | |
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LL | | struct Foo<const N: [u8; {
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... |
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LL | |
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LL | | fn main() {}
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| |____________^
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0391`.

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