Closed
Description
I tried this code:
//! Stripped-down repro case for a strange bug, wherein adding a new struct or enum variant can
//! surface type inference errors in completely unrelated code, even in different modules.
mod pb {
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
#[repr(i32)]
pub enum DataClass {
Unknown = 0,
Scalar = 1,
Tensor = 2,
BlobSequence = 3,
}
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct SummaryMetadata {
#[prost(enumeration = "DataClass", tag = "4")]
pub data_class: i32,
}
}
pub fn test() {
let md = pb::SummaryMetadata::default();
assert_eq!(md.data_class, pb::DataClass::BlobSequence.into());
}
// Uncomment this line to create an inference error at line 19:
//pub struct Foo(serde_json::Error);I expected it to compile, and it does. But when I uncomment the final
line, a new inference error appears on the assert_eq! line:
error[E0282]: type annotations needed
--> src/lib.rs:22:59
|
22 | assert_eq!(md.data_class, pb::DataClass::BlobSequence.into());
| ----------------------------^^^^--
| | |
| | cannot infer type for type parameter `T` declared on the trait `Into`
| this method call resolves to `T`
By itself, the inference error seems reasonable enough, and I can just
add type annotations. But the change has nothing to do with the error.
This is a stripped-down example. In my real code, I’m adding a variant
to an existing error enum, and I see two inference errors in entirely
unrelated modules:
$ git diff -U1
diff --git a/tensorboard/data/server/lib.rs b/tensorboard/data/server/lib.rs
index f1def3891..357693441 100644
--- a/tensorboard/data/server/lib.rs
+++ b/tensorboard/data/server/lib.rs
@@ -19,2 +19,4 @@ limitations under the License.
+pub struct Foo(serde_json::Error);
+
pub mod cli;
$ cargo check --tests
error[E0282]: type annotations needed
--> data_compat.rs:456:67
|
456 | assert_eq!(md.data_class, pb::DataClass::BlobSequence.into());
| ----------------------------^^^^--
| | |
| | cannot infer type for type parameter `T` declared on the trait `Into`
| this method call resolves to `T`
error[E0282]: type annotations needed
--> server.rs:629:37
|
629 | assert_eq!(xent_data.value, Vec::new());
| ^^^^^^^^ cannot infer type for type parameter `T`
Cloneable example:
https://github.com/wchargin/rust-inference-action-at-a-distance
Meta
Can repro in 1.48.0, 1.49.0-beta, and 2021-01-06 nightly.
cargo/rustc versions
$ cargo --version --verbose
cargo 1.48.0 (65cbdd2dc 2020-10-14)
release: 1.48.0
commit-hash: 65cbdd2dc0b7e877577474b98b7d071308d0bb6f
commit-date: 2020-10-14
$ cargo +beta --version --verbose
cargo 1.49.0-beta (8662ab427 2020-11-12)
release: 1.49.0
commit-hash: 8662ab427a8d6ad8047811cc4d78dbd20dd07699
commit-date: 2020-11-12
$ cargo +nightly --version --verbose
cargo 1.51.0-nightly (329895f5b 2021-01-06)
release: 1.51.0
commit-hash: 329895f5b52a358e5d9ecb26215708b5cb31d906
commit-date: 2021-01-06
Cargo.toml
[package]
name = "inference-action-at-a-distance"
version = "0.1.0"
edition = "2018"
[dependencies]
prost = "0.6.1"
serde_json = "1.0.59"Cargo.lock
# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
[[package]]
name = "anyhow"
version = "1.0.38"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "afddf7f520a80dbf76e6f50a35bca42a2331ef227a28b3b6dc5c2e2338d114b1"
[[package]]
name = "bytes"
version = "0.5.6"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0e4cec68f03f32e44924783795810fa50a7035d8c8ebe78580ad7e6c703fba38"
[[package]]
name = "either"
version = "1.6.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
[[package]]
name = "inference-action-at-a-distance"
version = "0.1.0"
dependencies = [
"prost",
"serde_json",
]
[[package]]
name = "itertools"
version = "0.8.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "f56a2d0bc861f9165be4eb3442afd3c236d8a98afd426f65d92324ae1091a484"
dependencies = [
"either",
]
[[package]]
name = "itoa"
version = "0.4.7"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "dd25036021b0de88a0aff6b850051563c6516d0bf53f8638938edbb9de732736"
[[package]]
name = "proc-macro2"
version = "1.0.24"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "1e0704ee1a7e00d7bb417d0770ea303c1bccbabf0ef1667dae92b5967f5f8a71"
dependencies = [
"unicode-xid",
]
[[package]]
name = "prost"
version = "0.6.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "ce49aefe0a6144a45de32927c77bd2859a5f7677b55f220ae5b744e87389c212"
dependencies = [
"bytes",
"prost-derive",
]
[[package]]
name = "prost-derive"
version = "0.6.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "537aa19b95acde10a12fec4301466386f757403de4cd4e5b4fa78fb5ecb18f72"
dependencies = [
"anyhow",
"itertools",
"proc-macro2",
"quote",
"syn",
]
[[package]]
name = "quote"
version = "1.0.8"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "991431c3519a3f36861882da93630ce66b52918dcf1b8e2fd66b397fc96f28df"
dependencies = [
"proc-macro2",
]
[[package]]
name = "ryu"
version = "1.0.5"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "71d301d4193d031abdd79ff7e3dd721168a9572ef3fe51a1517aba235bd8f86e"
[[package]]
name = "serde"
version = "1.0.119"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "9bdd36f49e35b61d49efd8aa7fc068fd295961fd2286d0b2ee9a4c7a14e99cc3"
[[package]]
name = "serde_json"
version = "1.0.61"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "4fceb2595057b6891a4ee808f70054bd2d12f0e97f1cbb78689b59f676df325a"
dependencies = [
"itoa",
"ryu",
"serde",
]
[[package]]
name = "syn"
version = "1.0.58"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "cc60a3d73ea6594cd712d830cc1f0390fd71542d8c8cd24e70cc54cdfd5e05d5"
dependencies = [
"proc-macro2",
"quote",
"unicode-xid",
]
[[package]]
name = "unicode-xid"
version = "0.2.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"