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Commit 870657c

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Rollup merge of #147180 - lcnr:forced_ambiguity-error, r=jdonszelmann
add tests fixes rust-lang/trait-system-refactor-initiative#105 the index test is for #146637 r? types
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‎compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs‎

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@@ -473,7 +473,10 @@ where
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// fails to reach a fixpoint but ends up getting an error after
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// running for some additional step.
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//
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// cc trait-system-refactor-initiative#105
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// FIXME(@lcnr): While I believe an error here to be possible, we
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// currently don't have any test which actually triggers it. @lqd
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// created a minimization for an ICE in typenum, but that one no
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// longer fails here. cc trait-system-refactor-initiative#105.
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let source = CandidateSource::BuiltinImpl(BuiltinImplSource::Misc);
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let certainty = Certainty::Maybe { cause, opaque_types_jank: OpaqueTypesJank::AllGood };
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self.probe_trait_candidate(source)
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// Regression test making sure that indexing fails with an ambiguity
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// error if one of the deref-steps encounters an inference variable.
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fn main() {
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let x = &Default::default();
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//~^ ERROR type annotations needed for `&_`
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x[1];
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let _: &Vec<()> = x;
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}
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error[E0282]: type annotations needed for `&_`
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--> $DIR/ambiguity-after-deref-step.rs:5:9
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|
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LL | let x = &Default::default();
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| ^
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LL |
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LL | x[1];
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| - type must be known at this point
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|
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help: consider giving `x` an explicit type, where the placeholders `_` are specified
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|
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LL | let x: &_ = &Default::default();
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| ++++
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error: aborting due to 1 previous error
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For more information about this error, try `rustc --explain E0282`.
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//@ compile-flags: -Znext-solver
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//@ check-pass
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// Regression test for trait-system-refactor-initiative#105. We previously encountered
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// an ICE in typenum as `forced_ambiguity` failed. While this test no longer causes
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// `forced_ambiguity` to error, we still want to use it as a regression test.
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pub struct UInt<U, B> {
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_msb: U,
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_lsb: B,
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}
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pub struct B1;
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pub trait Sub<Rhs> {
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type Output;
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}
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impl<U, B> Sub<B1> for UInt<UInt<U, B>, B1> {
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type Output = ();
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}
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impl<U> Sub<B1> for UInt<U, ()>
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where
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U: Sub<B1>,
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U::Output: Send,
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{
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type Output = ();
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}
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pub trait Op<N, R, I> {
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fn op(&self) {
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unimplemented!()
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}
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}
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trait OpIf<N, R, I> {}
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impl<N, Ur, Br, I> Op<N, UInt<Ur, Br>, I> for ()
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where
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N: Sub<I>,
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(): OpIf<N, UInt<UInt<Ur, Br>, N::Output>, I>,
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{
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}
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impl<N, R, Ui, Bi> OpIf<N, R, UInt<Ui, Bi>> for ()
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where
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UInt<Ui, Bi>: Sub<B1>,
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(): Op<N, R, <UInt<Ui, Bi> as Sub<B1>>::Output>,
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{
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}
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impl<N, R> OpIf<N, R, ()> for () where R: Sub<N> {}
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pub trait Compute {
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type Output;
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}
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pub fn repro<Ul, Bl>()
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where
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UInt<Ul, Bl>: Compute,
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<UInt<Ul, Bl> as Compute>::Output: Sub<B1>,
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(): Op<UInt<(), Bl>, (), ()>,
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{
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().op();
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}
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fn main() {}

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