Avoid creating useless projection predicate
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27534b3932
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@ -1205,7 +1205,17 @@ pub fn check_type_bounds<'tcx>(
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// ParamEnv for normalization specifically.
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// ParamEnv for normalization specifically.
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let normalize_param_env = {
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let normalize_param_env = {
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let mut predicates = param_env.caller_bounds().iter().collect::<Vec<_>>();
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let mut predicates = param_env.caller_bounds().iter().collect::<Vec<_>>();
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predicates.push(
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match impl_ty_value.kind() {
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ty::Projection(proj)
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if proj.item_def_id == trait_ty.def_id && proj.substs == rebased_substs =>
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{
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// Don't include this predicate if the projected type is
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// exactly the same as the projection. This can occur in
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// (somewhat dubious) code like this:
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//
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// impl<T> X for T where T: X { type Y = <T as X>::Y; }
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}
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_ => predicates.push(
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ty::Binder::dummy(ty::ProjectionPredicate {
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ty::Binder::dummy(ty::ProjectionPredicate {
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projection_ty: ty::ProjectionTy {
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projection_ty: ty::ProjectionTy {
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item_def_id: trait_ty.def_id,
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item_def_id: trait_ty.def_id,
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@ -1214,7 +1224,8 @@ pub fn check_type_bounds<'tcx>(
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ty: impl_ty_value,
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ty: impl_ty_value,
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})
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})
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.to_predicate(tcx),
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.to_predicate(tcx),
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);
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),
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};
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ty::ParamEnv::new(tcx.intern_predicates(&predicates), Reveal::UserFacing)
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ty::ParamEnv::new(tcx.intern_predicates(&predicates), Reveal::UserFacing)
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};
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};
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