rustdoc: don't crash when an external trait's docs needs to import another trait

src/librustdoc/clean/inline.rs

@@ -494,7 +494,16 @@ fn separate_supertrait_bounds(mut g: clean::Generics)
 }
 
 pub fn record_extern_trait(cx: &DocContext, did: DefId) {
-    cx.external_traits.borrow_mut().entry(did).or_insert_with(|| {
-        build_external_trait(cx, did)
-    });
+    if cx.external_traits.borrow().contains_key(&did) ||
+        cx.active_extern_traits.borrow().contains(&did)
+    {
+        return;
+    }
+
+    cx.active_extern_traits.borrow_mut().push(did);
+
+    let trait_ = build_external_trait(cx, did);
+
+    cx.external_traits.borrow_mut().insert(did, trait_);
+    cx.active_extern_traits.borrow_mut().remove_item(&did);
 }

src/librustdoc/core.rs

@@ -58,6 +58,9 @@ pub struct DocContext<'a, 'tcx: 'a, 'rcx: 'a> {
     pub renderinfo: RefCell<RenderInfo>,
     /// Later on moved through `clean::Crate` into `html::render::CACHE_KEY`
     pub external_traits: RefCell<FxHashMap<DefId, clean::Trait>>,
+    /// Used while populating `external_traits` to ensure we don't process the same trait twice at
+    /// the same time.
+    pub active_extern_traits: RefCell<Vec<DefId>>,
     // The current set of type and lifetime substitutions,
     // for expanding type aliases at the HIR level:
 
@@ -236,6 +239,7 @@ pub fn run_core(search_paths: SearchPaths,
             populated_all_crate_impls: Cell::new(false),
             access_levels: RefCell::new(access_levels),
             external_traits: Default::default(),
+            active_extern_traits: Default::default(),
             renderinfo: Default::default(),
             ty_substs: Default::default(),
             lt_substs: Default::default(),

src/test/rustdoc/auxiliary/issue-48414.rs

@@ -0,0 +1,15 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Woah, this trait links to [OtherTrait](OtherTrait)!
+pub trait SomeTrait {}
+
+/// Woah, this trait links to [SomeTrait](SomeTrait)!
+pub trait OtherTrait {}

src/test/rustdoc/issue-48414.rs

@@ -0,0 +1,21 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:issue-48414.rs
+
+// ICE when resolving paths for a trait that linked to another trait, when both were in an external
+// crate
+
+#![crate_name = "base"]
+
+extern crate issue_48414;
+
+#[doc(inline)]
+pub use issue_48414::{SomeTrait, OtherTrait};