From c88ba28d9a0261f448471255bd913e673858abaa Mon Sep 17 00:00:00 2001
From: mejrs <59372212+mejrs@users.noreply.github.com>
Date: Mon, 4 Nov 2024 18:08:30 +0100
Subject: [PATCH] document `type_implements_trait`
---
compiler/rustc_trait_selection/src/infer.rs | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
index bacb3b1b1b8..e91574fa1af 100644
--- a/compiler/rustc_trait_selection/src/infer.rs
+++ b/compiler/rustc_trait_selection/src/infer.rs
@@ -60,6 +60,18 @@ 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](traits::Obligation)
+ /// and check whether it holds, because it properly handles higher ranked traits
+ /// and it is more convenient and safer when your `params` are inside a `Binder`.
#[instrument(level = "debug", skip(self, params), ret)]
fn type_implements_trait(
&self,