proc-macro not distributed for target wasm32-unknown-unknown

[lukaslueg]

Coming over from koute/cargo-web#125

proc-macro is missing from the distribution for wasm32:

$ ls ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib | grep proc_macro
libproc_macro-1ea4ba9e4f6cdbc1.so

$ ls ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-unknown/lib | grep proc_macro

...which causes anything that depends on proc-macro2 somewhere down the tree to be unable to compile to wasm:

$ cargo new foobar
$ cd foobar
$ echo 'proc-macro2 = "*"' >> Cargo.toml
$ cargo build --target=wasm32-unknown-unknown
   Compiling unicode-xid v0.1.0                                                                                                                                                                                                              
   Compiling proc-macro2 v0.4.9
error[E0463]: can't find crate for `proc_macro`
  --> /home/kou/.cargo/registry/src/github.com-1ecc6299db9ec823/proc-macro2-0.4.9/src/lib.rs:50:1
   |
50 | extern crate proc_macro;
   | ^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

... which in turn is very sad because proc-macro2 is needed not just for procedural macros but also to "just" parse rust code and having anything depend on a crate which in turn depends on proc-macro2 effectively prohibits compiling for the web. May it be possible to include proc-macro in the wasm32-target ?

In fact, all I need is proc_macro2::{Delimiter, Ident, Literal, Punct, TokenStream}

[Boscop]

I want to use the interpolate crate (for string interpolation) in my yew frontend, but I'm getting:

error: cannot produce proc-macro for interpolate v0.1.1 as the target wasm32-unknown-unknown does not support these crate types

:(