Compute 'rustdoc --crate-type' support when Compilation is created

src/cargo/core/compiler/build_context/mod.rs

@@ -1,6 +1,5 @@
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
-use std::rc::Rc;
 use std::str;
 
 use log::debug;
@@ -34,7 +33,7 @@ pub struct BuildContext<'a, 'cfg> {
     pub packages: &'a PackageSet<'cfg>,
 
     /// Information about the compiler.
-    pub rustc: Rc<Rustc>,
+    pub rustc: Rustc,
     /// Build information for the host arch.
     pub host_config: TargetConfig,
     /// Build information for the target.
@@ -54,7 +53,7 @@ impl<'a, 'cfg> BuildContext<'a, 'cfg> {
         units: &'a UnitInterner<'a>,
         extra_compiler_args: HashMap<Unit<'a>, Vec<String>>,
     ) -> CargoResult<BuildContext<'a, 'cfg>> {
-        let rustc = Rc::new(config.load_global_rustc(Some(ws))?);
+        let rustc = config.load_global_rustc(Some(ws))?;
 
         let host_config = TargetConfig::new(config, &rustc.host)?;
         let target_config = match build_config.requested_target.as_ref() {

src/cargo/core/compiler/compilation.rs

@@ -2,7 +2,6 @@ use std::collections::{BTreeSet, HashMap, HashSet};
 use std::env;
 use std::ffi::OsStr;
 use std::path::PathBuf;
-use std::rc::Rc;
 
 use semver::Version;
 
@@ -76,7 +75,7 @@ pub struct Compilation<'cfg> {
     primary_unit_rustc_process: Option<ProcessBuilder>,
 
     target_runner: Option<(PathBuf, Vec<String>)>,
-    rustc: Rc<Rustc>,
+    supports_rustdoc_crate_type: bool,
 }
 
 impl<'cfg> Compilation<'cfg> {
@@ -113,7 +112,7 @@ impl<'cfg> Compilation<'cfg> {
             host: bcx.host_triple().to_string(),
             target: bcx.target_triple().to_string(),
             target_runner: target_runner(bcx)?,
-            rustc: bcx.rustc.clone(),
+            supports_rustdoc_crate_type: supports_rustdoc_crate_type(bcx.config, &bcx.rustc)?,
         })
     }
 
@@ -139,25 +138,14 @@ impl<'cfg> Compilation<'cfg> {
         Ok(p)
     }
 
-    fn supports_rustdoc_crate_type(&self) -> CargoResult<bool> {
-        // NOTE: Unconditionally return 'true' once support for
-        // rustdoc '--crate-type' rides to stable
-        let mut crate_type_test = process(self.config.rustdoc()?);
-        // If '--crate-type' is not supported by rustcoc, this command
-        // will exit with an error. Otherwise, it will print a help message,
-        // and exit successfully
-        crate_type_test.args(&["--crate-type", "proc-macro", "--help"]);
-        Ok(self.rustc.cached_output(&crate_type_test).is_ok())
-    }
-
     /// See `process`.
     pub fn rustdoc_process(&self, pkg: &Package, target: &Target) -> CargoResult<ProcessBuilder> {
         let mut p = self.fill_env(process(&*self.config.rustdoc()?), pkg, false)?;
         if target.edition() != Edition::Edition2015 {
             p.arg(format!("--edition={}", target.edition()));
         }
 
-        if self.supports_rustdoc_crate_type()? {
+        if self.supports_rustdoc_crate_type {
             for crate_type in target.rustc_crate_types() {
                 p.arg("--crate-type").arg(crate_type);
             }
@@ -331,3 +319,14 @@ fn target_runner(bcx: &BuildContext<'_, '_>) -> CargoResult<Option<(PathBuf, Vec
 
     Ok(None)
 }
+
+fn supports_rustdoc_crate_type(config: &Config, rustc: &Rustc) -> CargoResult<bool> {
+    // NOTE: Unconditionally return 'true' once support for
+    // rustdoc '--crate-type' rides to stable
+    let mut crate_type_test = process(config.rustdoc()?);
+    // If '--crate-type' is not supported by rustcoc, this command
+    // will exit with an error. Otherwise, it will print a help message,
+    // and exit successfully
+    crate_type_test.args(&["--crate-type", "proc-macro", "--help"]);
+    Ok(rustc.cached_output(&crate_type_test).is_ok())
+}