From 114e88c9d0b8bbc16027e0c10d34c73e15381d7b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Le=C3=B3n=20Orell=20Valerian=20Liehr?= <me@fmease.dev>
Date: Mon, 8 Apr 2024 20:37:48 +0200
Subject: [PATCH] rustdoc: synthetic auto: filter out clauses from the
 implementor's ParamEnv

not just the ones from the elaborated clauses.
---
 src/librustdoc/clean/auto_trait.rs                |  2 +-
 tests/rustdoc/synthetic_auto/supertrait-bounds.rs | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 tests/rustdoc/synthetic_auto/supertrait-bounds.rs

diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index 217f6bb550bca..daf63998461ee 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -168,7 +168,7 @@ fn clean_param_env<'tcx>(
 
     // FIXME(#111101): Incorporate the explicit predicates of the item here...
     let item_predicates: FxIndexSet<_> =
-        tcx.predicates_of(item_def_id).predicates.iter().map(|(pred, _)| pred).collect();
+        tcx.param_env(item_def_id).caller_bounds().iter().collect();
     let where_predicates = param_env
         .caller_bounds()
         .iter()
diff --git a/tests/rustdoc/synthetic_auto/supertrait-bounds.rs b/tests/rustdoc/synthetic_auto/supertrait-bounds.rs
new file mode 100644
index 0000000000000..503e65d0f4fa2
--- /dev/null
+++ b/tests/rustdoc/synthetic_auto/supertrait-bounds.rs
@@ -0,0 +1,14 @@
+// Check that we don't add bounds to synthetic auto trait impls that are
+// already implied by the item (like supertrait bounds).
+
+// In this case we don't want to add the bounds `T: Copy` and `T: 'static`
+// to the auto trait impl because they're implied by the bound `T: Bound`
+// on the implementor `Type`.
+
+pub struct Type<T: Bound>(T);
+
+// @has supertrait_bounds/struct.Type.html
+// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
+// "impl<T> Send for Type<T>where T: Send,"
+
+pub trait Bound: Copy + 'static {}