Building serde deps with bazel rules_rust fails with syn compile

[ttiurani]

Hi! I am very new to Rust and trying to get Bazel's rules_rust to work. With these deps:

[dependencies]
serde = "=1.0.116"
serde_derive = "=1.0.116"
serde_json = "=1.0.58"

I am trying to do this:

rust_library(
    name = "my_lib",
    srcs = ["src/lib.rs"],
    deps = ["//third_party/cargo:serde", "//third_party/cargo:serde_json"],
    proc_macro_deps = ["//third_party/cargo:serde_derive"],
)

but I keep on bumping into the following kind of exception. I'm probably doing something very wrong, so might someone right off the bat be able to say what's wrong? With cargo build this works, so it's probably something else.

INFO: From Compiling Rust lib syn v1.0.42 (88 files):
error[E0277]: the trait bound `proc_macro2::TokenStream: std::convert::From<proc_macro::TokenStream>` is not satisfied
   --> external/raze__syn__1_0_42/src/buffer.rs:106:20
    |
106 |         Self::new2(stream.into())
    |                    ^^^^^^^^^^^^^ the trait `std::convert::From<proc_macro::TokenStream>` is not implemented for `proc_macro2::TokenStream`
    |
    = help: the following implementations were found:
              <proc_macro2::TokenStream as std::convert::From<proc_macro2::TokenTree>>
    = note: required because of the requirements on the impl of `std::convert::Into<proc_macro2::TokenStream>` for `proc_macro::TokenStream`

error[E0277]: the trait bound `proc_macro2::TokenStream: std::convert::From<proc_macro::TokenStream>` is not satisfied
    --> external/raze__syn__1_0_42/src/parse.rs:1138:21
     |
1138 |         self.parse2(proc_macro2::TokenStream::from(tokens))
     |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::convert::From<proc_macro::TokenStream>` is not implemented for `proc_macro2::TokenStream`
     |
     = help: the following implementations were found:
               <proc_macro2::TokenStream as std::convert::From<proc_macro2::TokenTree>>
     = note: required by `std::convert::From::from`

cargo raze outputted this:

Loaded override settings: RazeSettings {
    workspace_path: "//third_party/cargo",
    incompatible_relative_workspace_path: false,
    target: "x86_64-unknown-linux-gnu",
    crates: {},
    gen_workspace_prefix: "raze",
    genmode: Remote,
    output_buildfile_suffix: "BUILD.bazel",
    default_gen_buildrs: false,
}
Generated ./remote/BUILD.bazel successfully
Generated ./remote/itoa-0.4.6.BUILD.bazel successfully
Generated ./remote/proc-macro2-1.0.24.BUILD.bazel successfully
Generated ./remote/quote-1.0.7.BUILD.bazel successfully
Generated ./remote/ryu-1.0.5.BUILD.bazel successfully
Generated ./remote/serde-1.0.116.BUILD.bazel successfully
Generated ./remote/serde_derive-1.0.116.BUILD.bazel successfully
Generated ./remote/serde_json-1.0.58.BUILD.bazel successfully
Generated ./remote/syn-1.0.42.BUILD.bazel successfully
Generated ./remote/unicode-xid-0.2.1.BUILD.bazel successfully
Generated ./BUILD.bazel successfully
Generated ./crates.bzl successfully

Any ideas?

[ttiurani]

To leave a trace on the internet in case anyone else bumps into this, I fixed this by following this advice and setting:

[raze]
...
default_gen_buildrs = true

and then building again. That got me further but caused an ld: library not found for -lstdc++ on my Catalina OSX, but I fixed that by downloading XCode 9.4.1 from:

https://developer.apple.com/download/more/?q=xcode

running xip -x Xcode_9.4.1.xip to unpack it and copying the older libstdc++ files to the current XCode (inspiration):

cp Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/libstdc++.*  /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/lib/

after which bazel build succeeded.