rustdoc: Prevent infinite recursion when inlining

Cyclic pub-use chains triggered infinite recursion, and this commit adds a hash
set to guard against cyclic recursion. This will cause one of the reexports to
render as a `pub use` instead of inlining the documentation.

Closes #16274

Author: alexcrichton

src/librustdoc/visit_ast.rs

@@ -11,6 +11,8 @@
 //! Rust AST Visitor. Extracts useful information and massages it into a form
 //! usable for clean
 
+use std::collections::HashSet;
+
 use syntax::abi;
 use syntax::ast;
 use syntax::ast_util;
@@ -38,6 +40,7 @@ pub struct RustdocVisitor<'a, 'tcx: 'a> {
     pub attrs: Vec<ast::Attribute>,
     pub cx: &'a core::DocContext<'tcx>,
     pub analysis: Option<&'a core::CrateAnalysis>,
+    view_item_stack: HashSet<ast::NodeId>,
 }
 
 impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
@@ -48,6 +51,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
             attrs: Vec::new(),
             cx: cx,
             analysis: analysis,
+            view_item_stack: HashSet::new(),
         }
     }
 
@@ -228,8 +232,9 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
         if !please_inline && analysis.public_items.contains(&def.node) {
             return false
         }
+        if !self.view_item_stack.insert(id) { return false }
 
-        match tcx.map.get(def.node) {
+        let ret = match tcx.map.get(def.node) {
             ast_map::NodeItem(it) => {
                 if glob {
                     match it.node {
@@ -249,7 +254,9 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
                 true
             }
             _ => false,
-        }
+        };
+        self.view_item_stack.remove(&id);
+        return ret;
     }
 
     pub fn visit_item(&mut self, item: &ast::Item,

src/test/run-make/rustdoc-recursion/Makefile

@@ -0,0 +1,10 @@
+-include ../tools.mk
+
+# FIXME ignore windows
+ifndef IS_WINDOWS
+all:
+	$(HOST_RPATH_ENV) $(RUSTDOC) -w html -o $(TMPDIR)/doc foo.rs
+else
+all:
+endif
+

src/test/run-make/rustdoc-recursion/foo.rs

@@ -0,0 +1,25 @@
+// Copyright 2012-2013 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.
+
+#![crate_type = "lib"]
+#![feature(globs)]
+
+mod m {
+    pub use self::a::Foo;
+
+    mod a {
+        pub struct Foo;
+    }
+
+    mod b {
+        pub use super::*;
+    }
+}
+