Handle projection predicates in the param env for auto-trait docs
Fixes #72213 Any predicates in the param env are guaranteed to hold, so we don't need to do any additional processing of them if we come across them as sub-obligations of a different predicate. This allows us to avoid adding the same predicate to the computed ParamEnv multiple times (but with different regions each time), which causes an ambiguity error during fulfillment.
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@ -270,6 +270,13 @@ impl AutoTraitFinder<'tcx> {
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) -> Option<(ty::ParamEnv<'tcx>, ty::ParamEnv<'tcx>)> {
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let tcx = infcx.tcx;
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// Don't try to proess any nested obligations involving predicates
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// that are already in the `ParamEnv` (modulo regions): we already
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// know that they must hold.
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for predicate in param_env.caller_bounds() {
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fresh_preds.insert(self.clean_pred(infcx, predicate));
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}
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let mut select = SelectionContext::with_negative(&infcx, true);
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let mut already_visited = FxHashSet::default();
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@ -0,0 +1,25 @@
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// Regression test for issue #72213
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// Tests that we don't ICE when we have projection predicates
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// in our initial ParamEnv
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pub struct Lines<'a, L>
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where
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L: Iterator<Item = &'a ()>,
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{
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words: std::iter::Peekable<Words<'a, L>>,
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}
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pub struct Words<'a, L> {
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_m: std::marker::PhantomData<&'a L>,
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}
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impl<'a, L> Iterator for Words<'a, L>
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where
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L: Iterator<Item = &'a ()>,
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{
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type Item = ();
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fn next(&mut self) -> Option<Self::Item> {
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unimplemented!()
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}
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}
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