Cargo doc failing on serde as dependency [v1.0.66]

[Lakier15]

Cargo doc seems to fail on 1.0.66.

Steps to reproduce:

• Run

cargo new serde_doc_fail

• Add to Cargo.toml

[dependencies]
serde = "1.0.66"

• Run

cargo doc

Output:

Updating registry `https://github.com/rust-lang/crates.io-index`
   Compiling serde v1.0.66
 Documenting serde v1.0.66
error: unused import: `SeqAccess`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/value.rs:41:44
   |
41 | use de::{self, Expected, IntoDeserializer, SeqAccess};
   |                                            ^^^^^^^^^
   |
note: lint level defined here
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/lib.rs:129:23
   |
129| #![deny(missing_docs, unused_imports)]
   |                       ^^^^^^^^^^^^^^

error: unused import: `private::de::size_hint`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/value.rs:42:5
   |
42 | use private::de::size_hint;
   |     ^^^^^^^^^^^^^^^^^^^^^^

error: unused import: `Unexpected`
    --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/value.rs:1316:20
     |
1316 |     use de::{self, Unexpected};
     |                    ^^^^^^^^^^

error: unused imports: `Unexpected`, `VariantAccess`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/impls.rs:12:62
   |
12 |     Deserialize, Deserializer, EnumAccess, Error, SeqAccess, Unexpected, VariantAccess, Visitor,
   |                                                              ^^^^^^^^^^  ^^^^^^^^^^^^^

error: unused import: `de::MapAccess`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/impls.rs:16:5
   |
16 | use de::MapAccess;
   |     ^^^^^^^^^^^^^

error: unused import: `de::from_primitive::FromPrimitive`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/impls.rs:18:5
   |
18 | use de::from_primitive::FromPrimitive;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: unused import: `private::de::InPlaceSeed`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/impls.rs:19:5
   |
19 | use private::de::InPlaceSeed;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^

error: unused import: `private::de::size_hint`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/de/impls.rs:22:5
   |
22 | use private::de::size_hint;
   |     ^^^^^^^^^^^^^^^^^^^^^^

error: unused imports: `Error`, `SerializeTuple`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/ser/impls.rs:11:11
   |
11 | use ser::{Error, Serialize, SerializeTuple, Serializer};
   |           ^^^^^             ^^^^^^^^^^^^^^

error: unused import: `Unexpected`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/private/de.rs:14:21
   |
14 | use de::{MapAccess, Unexpected};
   |                     ^^^^^^^^^^

error: unused import: `super::size_hint`
   --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/private/de.rs:232:9
    |
232 |     use super::size_hint;
    |         ^^^^^^^^^^^^^^^^

error: unused import: `SerializeStruct`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/private/ser.rs:11:54
   |
11 | use ser::{self, Impossible, Serialize, SerializeMap, SerializeStruct, Serializer};
   |                                                      ^^^^^^^^^^^^^^^

error: unused import: `ContentSerializer`
  --> /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/private/ser.rs:15:14
   |
15 |     Content, ContentSerializer, SerializeStructVariantAsMapValue, SerializeTupleVariantAsMapValue,
   |              ^^^^^^^^^^^^^^^^^

error: Compilation failed, aborting rustdoc

error: Could not document `serde`.

Caused by:
  process didn't exit successfully: `rustdoc --crate-name serde /home/CL/alex.gasbarroni/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.66/src/lib.rs -o /home/CL/alex.gasbarroni/git/ser/target/doc --cfg feature="default" --cfg feature="std" -L dependency=/home/CL/alex.gasbarroni/git/ser/target/debug/deps --cfg de_boxed_c_str --cfg de_rc_dst --cfg core_duration --cfg integer128 --cfg num_nonzero` (exit code: 101)
warning: build failed, waiting for other jobs to finish...
error: build failed

[dtolnay]

Thanks! This is a compiler bug. I filed rust-lang/rust#51661 to follow up.