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Nov 5, 2024
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document type_implements_trait #132608

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c88ba28
document `type_implements_trait`
mejrs Nov 4, 2024
e37a3a8
Explain how to evaluate an obligation
mejrs Nov 5, 2024
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18 changes: 18 additions & 0 deletions compiler/rustc_trait_selection/src/infer.rs
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Expand Up @@ -60,6 +60,24 @@ impl<'tcx> InferCtxt<'tcx> {
///
/// Invokes `evaluate_obligation`, so in the event that evaluating
/// `Ty: Trait` causes overflow, EvaluatedToAmbigStackDependent will be returned.
///
/// `type_implements_trait` is a convenience function for simple cases like
///
/// ```ignore (illustrative)
/// let copy_trait = infcx.tcx.require_lang_item(LangItem::Copy, span);
/// let implements_copy = infcx.type_implements_trait(copy_trait, [ty], param_env)
/// .must_apply_modulo_regions();
/// ```
///
/// In most cases you should instead create an [Obligation] and check whether
/// it holds via [`evaluate_obligation`] or one of its helper functions like
/// [`predicate_must_hold_modulo_regions`], because it properly handles higher ranked traits
/// and it is more convenient and safer when your `params` are inside a [`Binder`].
///
/// [Obligation]: traits::Obligation
/// [`evaluate_obligation`]: crate::traits::query::evaluate_obligation::InferCtxtExt::evaluate_obligation
/// [`predicate_must_hold_modulo_regions`]: crate::traits::query::evaluate_obligation::InferCtxtExt::predicate_must_hold_modulo_regions
/// [`Binder`]: ty::Binder
#[instrument(level = "debug", skip(self, params), ret)]
fn type_implements_trait(
&self,
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