CI: Check intra-doc links

Credit: https://twitter.com/tomaka17/status/1176017851410526208

.github/workflows/rust.yml

@@ -39,3 +39,18 @@ jobs:
       run: $HOME/.cargo/bin/cargo test --verbose --release --all
     - name: Run slow tests
       run: $HOME/.cargo/bin/cargo test --verbose --release --all -- --ignored
+
+  doc-links:
+    name: Check intra-doc links
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: doc
+          args: --document-private-items

bellman/src/lib.rs

@@ -1,3 +1,6 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
 #[cfg(feature = "multicore")]
 extern crate crossbeam;
 

ff/src/lib.rs

@@ -1,3 +1,5 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
 #![allow(unused_imports)]
 
 #[cfg(feature = "derive")]

group/src/lib.rs

@@ -1,3 +1,6 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
 use ff::{PrimeField, PrimeFieldDecodingError, ScalarEngine, SqrtField};
 use rand::RngCore;
 use std::error::Error;

librustzcash/src/rustzcash.rs

@@ -1,3 +1,6 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
 use lazy_static;
 
 use ff::{PrimeField, PrimeFieldRepr};

pairing/src/lib.rs

@@ -8,6 +8,8 @@
 #![cfg_attr(feature = "cargo-clippy", allow(clippy::many_single_char_names))]
 #![cfg_attr(feature = "cargo-clippy", allow(clippy::new_without_default))]
 #![cfg_attr(feature = "cargo-clippy", allow(clippy::write_literal))]
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
 // Force public structures to implement Debug
 #![deny(missing_debug_implementations)]
 

zcash_client_backend/src/lib.rs

@@ -3,6 +3,9 @@
 //! `zcash_client_backend` contains Rust structs and traits for creating shielded Zcash
 //! light clients.
 
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
 pub mod constants;
 pub mod encoding;
 pub mod keys;

zcash_primitives/src/lib.rs

@@ -1,3 +1,6 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
 #[macro_use]
 extern crate lazy_static;
 

zcash_proofs/src/lib.rs

@@ -1,3 +1,6 @@
+// Catch documentation errors caused by code changes.
+#![deny(intra_doc_link_resolution_failure)]
+
 use bellman::groth16::{prepare_verifying_key, Parameters, PreparedVerifyingKey, VerifyingKey};
 use pairing::bls12_381::Bls12;
 use std::fs::File;