Auto merge of #131076 - lukas-code:doc-stab2, r=notriddle

rustdoc: rewrite stability inheritance as a doc pass

Since doc inlining can almost arbitrarily change the module hierarchy, we can't just use the HIR ancestors of an item to compute its effective stability. This PR moves the stability inheritance that I implemented in https://github.com/rust-lang/rust/pull/130798 into a new doc pass `propagate-stability` that runs after doc inlining and uses the post-inlining ancestors of an item to correctly compute its effective stability.

fixes https://github.com/rust-lang/rust/issues/131020

r? `@notriddle`

1 files changed, 10 insertions, 0 deletions

diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index 762ebc47ca9..28d73fbe9f3 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -80,6 +80,10 @@ impl Stability {
     pub fn is_stable(&self) -> bool {
         self.level.is_stable()
     }
+
+    pub fn stable_since(&self) -> Option<StableSince> {
+        self.level.stable_since()
+    }
 }
 
 /// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
@@ -170,6 +174,12 @@ impl StabilityLevel {
     pub fn is_stable(&self) -> bool {
         matches!(self, StabilityLevel::Stable { .. })
     }
+    pub fn stable_since(&self) -> Option<StableSince> {
+        match *self {
+            StabilityLevel::Stable { since, .. } => Some(since),
+            StabilityLevel::Unstable { .. } => None,
+        }
+    }
 }
 
 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]