Rollup merge of rust-lang#133721 - aDotInTheVoid:rdj-dyn-link, r=GuillaumeGomez

rustdoc-json: Add test for `impl Trait for dyn Trait`

Found while investigating rust-lang#133719

Helps with rust-lang#81359

r? `@GuillaumeGomez`

Author: GuillaumeGomez

tests/rustdoc-json/impls/trait-for-dyn-trait.rs

@@ -0,0 +1,15 @@
+//@ set t1 = '$.index[*][?(@.name=="T1")].id'
+pub trait T1 {}
+
+//@ set t2 = '$.index[*][?(@.name=="T2")].id'
+pub trait T2 {}
+
+/// Fun impl
+impl T1 for dyn T2 {}
+
+//@ set impl = '$.index[*][?(@.docs=="Fun impl")].id'
+//@ is '$.index[*][?(@.name=="T1")].inner.trait.implementations[*]' $impl
+//@ is '$.index[*][?(@.name=="T2")].inner.trait.implementations' []
+
+//@ is '$.index[*][?(@.docs=="Fun impl")].inner.impl.trait.id' $t1
+//@ is '$.index[*][?(@.docs=="Fun impl")].inner.impl.for.dyn_trait.traits[*].trait.id' $t2