use rustc shim instead of rustc

closes #435

Cargo.toml

@@ -19,6 +19,7 @@ log = "0.3"
 racer = "2.0.6"
 rls-analysis = "0.6.5"
 rls-data = { version = "0.10", features = ["serialize-serde"] }
+rls-rustc = "0.1"
 rls-span = { version = "0.4", features = ["serialize-serde"] }
 rls-vfs = { version = "0.4", features = ["racer-impls"] }
 rustfmt-nightly = "0.2"

src/build/cargo.rs

@@ -294,8 +294,9 @@ impl Executor for RlsExecutor {
             }
         }
 
-        let rustc_exe = env::var("RUSTC").unwrap_or("rustc".to_owned());
+        let rustc_exe = env::var("RUSTC").unwrap_or(env::args().next().unwrap());
         let mut cmd = Command::new(&rustc_exe);
+        cmd.env(::RUSTC_SHIM_ENV_VAR_NAME, "1");
 
         // We only want to intercept rustc call targeting current crate to cache
         // args/envs generated by cargo so we can run only rustc later ourselves

src/main.rs

@@ -23,9 +23,10 @@ extern crate lazy_static;
 extern crate log;
 extern crate racer;
 extern crate rls_analysis as analysis;
-extern crate rls_vfs as vfs;
-extern crate rls_span as span;
 extern crate rls_data as data;
+extern crate rls_rustc as rustc_shim;
+extern crate rls_span as span;
+extern crate rls_vfs as vfs;
 extern crate rustfmt_nightly as rustfmt;
 extern crate serde;
 #[macro_use]
@@ -39,6 +40,7 @@ extern crate url;
 extern crate url_serde;
 extern crate jsonrpc_core;
 
+use std::env;
 use std::sync::Arc;
 
 mod actions;
@@ -59,11 +61,17 @@ const CRATE_BLACKLIST: [&'static str; 10] = [
     "serde_json", "librustc_serialize", "libunicode_segmentation",
 ];
 
+const RUSTC_SHIM_ENV_VAR_NAME: &'static str = "RLS_RUSTC_SHIM";
+
 type Span = span::Span<span::ZeroIndexed>;
 
 pub fn main() {
     env_logger::init().unwrap();
 
+    if env::var(RUSTC_SHIM_ENV_VAR_NAME).map(|v| v != "0").unwrap_or(false) {
+        rustc_shim::run();
+    }
+
     if let Some(first_arg) = ::std::env::args().skip(1).next() {
         match first_arg.as_str() {
             "--version" | "-V" => println!("rls {}", version()),

src/test/harness.rs

@@ -166,6 +166,7 @@ pub fn expect_messages(results: LsResultList, expected: &[&ExpectedMessage]) {
 // Initialise the environment for a test.
 pub fn init_env(project_dir: &str) -> (Cache, TestCleanup) {
     let _ = env_logger::init();
+    env::set_var("RUSTC", "rustc");
 
     let path = &Path::new("test_data").join(project_dir);
     let tc = TestCleanup { path: path.to_owned() };