proc-macro derive panicked

[alanhkarp]

The following compiles without the Serialize or Deserialize in derive. Note that all variables are Copy. I am running macOS Sierra Version 10.12.16 on a MacBook Pro with a 2.2 Ghz Intel Core i7.

cargo run
Compiling multicell v0.1.0 (file:///Users/alan/Documents/Eclipse/multicell)
error: proc-macro derive panicked
--> src/routing_table_entry.rs:9:41
|
9 | #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
| ^^^^^^^^^^^
|
= help: message: called Result::unwrap() on an Err value: "failed to parse derive input: "pub struct RoutingTableEntry {\n index: TableIndex,\n uuid: Uuid,\n may_send: bool,\n inuse: bool,\n parent: PortNo,\n mask: Mask,\n other_indices: [TableIndex; MAX_PORTS.v as usize],\n}""

error: Could not compile multicell.

To learn more, run the command again with --verbose.

rustc --version --verbose routing_table_entry.rs
rustc 1.15.1 (021bd29 2017-02-08)
binary: rustc
commit-hash: 021bd29
commit-date: 2017-02-08
host: x86_64-apple-darwin
release: 1.15.1
LLVM version: 3.9

cargo run --verbose
Fresh cfg-if v0.1.1
Fresh itoa v0.3.1
Fresh unicode-xid v0.0.4
Fresh serde v0.9.11
Fresh dtoa v0.4.1
Fresh num-traits v0.1.37
Fresh libc v0.2.21
Fresh rustc-demangle v0.1.4
Fresh crossbeam v0.2.10
Fresh quick-error v1.2.0
Fresh quote v0.3.15
Fresh synom v0.11.3
Fresh serde_json v0.9.9
Fresh rand v0.3.15
Fresh backtrace v0.3.2
Fresh syn v0.11.9
Fresh eval v0.4.0
Fresh uuid v0.4.0
Fresh error-chain v0.10.0
Fresh serde_codegen_internals v0.14.1
Fresh serde_derive v0.9.11
Compiling multicell v0.1.0 (file:///Users/alan/Documents/Eclipse/multicell)
Running rustc --crate-name multicell src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=c3754c3b59b444a8 -C extra-filename=-c3754c3b59b444a8 --out-dir /Users/alan/Documents/Eclipse/multicell/target/debug/deps -L dependency=/Users/alan/Documents/Eclipse/multicell/target/debug/deps --extern serde_json=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libserde_json-3d75a8ee8aa27a6a.rlib --extern eval=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libeval-19007993aba8ae97.rlib --extern error_chain=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/liberror_chain-dc31d088e7e1eb1e.rlib --extern crossbeam=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libcrossbeam-49604b5af8766723.rlib --extern serde_derive=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libserde_derive-c205a175c33019f9.dylib --extern rand=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/librand-e7e80d6f8d47bbec.rlib --extern uuid=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libuuid-461871f5c8ab3856.rlib --extern serde=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libserde-0dc9e96503d8d5e9.rlib --extern multicell=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libmulticell-cd67f32b1d3caf8c.rlib
error: proc-macro derive panicked
--> src/routing_table_entry.rs:9:41
|
9 | #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
| ^^^^^^^^^^^
|
= help: message: called Result::unwrap() on an Err value: "failed to parse derive input: "pub struct RoutingTableEntry {\n index: TableIndex,\n uuid: Uuid,\n may_send: bool,\n inuse: bool,\n parent: PortNo,\n mask: Mask,\n other_indices: [TableIndex; MAX_PORTS.v as usize],\n}""

error: Could not compile multicell.

Caused by:
process didn't exit successfully: rustc --crate-name multicell src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=c3754c3b59b444a8 -C extra-filename=-c3754c3b59b444a8 --out-dir /Users/alan/Documents/Eclipse/multicell/target/debug/deps -L dependency=/Users/alan/Documents/Eclipse/multicell/target/debug/deps --extern serde_json=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libserde_json-3d75a8ee8aa27a6a.rlib --extern eval=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libeval-19007993aba8ae97.rlib --extern error_chain=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/liberror_chain-dc31d088e7e1eb1e.rlib --extern crossbeam=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libcrossbeam-49604b5af8766723.rlib --extern serde_derive=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libserde_derive-c205a175c33019f9.dylib --extern rand=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/librand-e7e80d6f8d47bbec.rlib --extern uuid=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libuuid-461871f5c8ab3856.rlib --extern serde=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libserde-0dc9e96503d8d5e9.rlib --extern multicell=/Users/alan/Documents/Eclipse/multicell/target/debug/deps/libmulticell-cd67f32b1d3caf8c.rlib (exit code: 101)

[est31]

cc @dtolnay -- maybe a serde bug?

[alanhkarp]

I have no idea how to tell. On 11/17/2016 serde-rs/serde#623 says that "This is #37788 for which a fix has merged into Rust and will be in tomorrow's nightly." I am using stable, but a change from last November should have made it into stable by now.

[dtolnay]

pub struct RoutingTableEntry {
    index: TableIndex,
    uuid: Uuid,
    may_send: bool,
    inuse: bool,
    parent: PortNo,
    mask: Mask,
    other_indices: [TableIndex; MAX_PORTS.v as usize],
}

The array length expression here requires you to enable the full feature of syn. See https://github.com/dtolnay/syn#optional-features. By default it will only parse very basic length expressions because the full expression grammar is so complicated that it would take 3 times longer to compile for something that almost nobody ever uses.

You can get this to work as is by enabling the relevant feature in Cargo.toml:

syn = { version = "0.11", features = ["full"] }

Or without that, you can factor the length expression into a standalone constant:

const OTHER_INDICES_LEN: usize = MAX_PORTS.v as usize;

pub struct RoutingTableEntry {
    other_indices: [TableIndex; OTHER_INDICES_LEN],
}

Or factor out the entire array type:

type OtherIndices = [TableIndex; MAX_PORTS.v as usize];

pub struct RoutingTableEntry {
    other_indices: OtherIndices,
}

[alanhkarp]

Thanks for the prompt response. I never would have figured that out.

In the spirit of Rust's excellent compiler errors, I wonder if the error message include something like

  Try syn = { version = "0.11", features = ["full"] } in Cargo.toml

[Mark-Simulacrum]

I don't believe this is a rust compiler bug; I don't think we can make that suggestion on our side (since this is a failure on serde's side). Closing. It's possible Serde can make that suggestion in the panic! call, but that's something you'd have to request on their issue tracker.

[nidhinmahesh]

Facing a similar issue as above but I am not using this package. Issue might be caused by some other package but I am finding it difficult to find the error:

[dependencies]
actix = "0.10.0"
actix-web = "3.3.2"
actix-cors = "0.5.3"
actix-service = "1.0.6"
actix-http = "2.2.0"
blob-uuid = "0.4.0"
chrono = "0.4.6"
diesel = { version = "1.4.5", features = ["chrono", "postgres", "r2d2", "uuidv07", "serde_json"] }
uuid = { version = "0.8.1", features = ["serde", "v4"] }
dotenv = "0.15.0"
env_logger = "0.8.2"
failure = "0.1.8"
futures = "0.3.8"
http = "0.2.2"
jsonwebtoken = "7.2.0"
lazy_static = "1.4.0"
libreauth = "0.14.0"
log = "0.4.11"
num_cpus = "1.13.0"
regex = "1.4.2"
serde = "1.0.118"
serde_derive = "1.0.118"
serde_json = "1.0.60"
slug = "0.1.4"
validator = { version = "0.12", features = ["derive"] }
validator_derive = "0.12.0"

Error messsage : Same as @alanhkarp