Make InstallMethod::Dist safer to work with

There are enough fields that using a struct type is going to avoid some
eventual typo, and readability is aided.

Author: rbtcollins

src/install.rs

@@ -19,25 +19,25 @@ pub enum InstallMethod<'a> {
     Link(&'a Path, &'a CustomToolchain<'a>),
     Installer(&'a Path, &'a temp::Cfg, &'a CustomToolchain<'a>),
     // bool is whether to force an update
-    Dist(
-        &'a dist::ToolchainDesc,
-        dist::Profile,
-        Option<&'a Path>,
-        DownloadCfg<'a>,
+    Dist {
+        desc: &'a dist::ToolchainDesc,
+        profile: dist::Profile,
+        update_hash: Option<&'a Path>,
+        dl_cfg: DownloadCfg<'a>,
         // --force
-        bool,
+        force_update: bool,
         // --allow-downgrade
-        bool,
+        allow_downgrade: bool,
         // toolchain already exists
-        bool,
+        exists: bool,
         // currently installed date
-        Option<&'a str>,
+        old_date: Option<&'a str>,
         // Extra components to install from dist
-        &'a [&'a str],
+        components: &'a [&'a str],
         // Extra targets to install from dist
-        &'a [&'a str],
-        &'a DistributableToolchain<'a>,
-    ),
+        targets: &'a [&'a str],
+        distributable: &'a DistributableToolchain<'a>,
+    },
 }
 
 impl<'a> InstallMethod<'a> {
@@ -86,7 +86,7 @@ impl<'a> InstallMethod<'a> {
         if path.exists() {
             // Don't uninstall first for Dist method
             match self {
-                InstallMethod::Dist(..) | InstallMethod::Installer(..) => {}
+                InstallMethod::Dist { .. } | InstallMethod::Installer(..) => {}
                 _ => {
                     uninstall(path, notify_handler)?;
                 }
@@ -106,8 +106,8 @@ impl<'a> InstallMethod<'a> {
                 InstallMethod::tar_gz(src, path, &temp_cfg, notify_handler)?;
                 Ok(true)
             }
-            InstallMethod::Dist(
-                toolchain,
+            InstallMethod::Dist {
+                desc,
                 profile,
                 update_hash,
                 dl_cfg,
@@ -117,13 +117,13 @@ impl<'a> InstallMethod<'a> {
                 old_date,
                 components,
                 targets,
-                ..,
-            ) => {
+                ..
+            } => {
                 let prefix = &InstallPrefix::from(path.to_owned());
                 let maybe_new_hash = dist::update_from_dist(
                     dl_cfg,
                     update_hash,
-                    toolchain,
+                    desc,
                     if exists { None } else { Some(profile) },
                     prefix,
                     force_update,

src/toolchain.rs

@@ -713,19 +713,19 @@ impl<'a> DistributableToolchain<'a> {
     ) -> Result<UpdateStatus> {
         let update_hash = self.update_hash()?;
         let old_date = self.get_manifest().ok().and_then(|m| m.map(|m| m.date));
-        InstallMethod::Dist(
-            &self.desc()?,
-            self.0.cfg.get_profile()?,
-            Some(&update_hash),
-            self.0.download_cfg(),
+        InstallMethod::Dist {
+            desc: &self.desc()?,
+            profile: self.0.cfg.get_profile()?,
+            update_hash: Some(&update_hash),
+            dl_cfg: self.0.download_cfg(),
             force_update,
             allow_downgrade,
-            self.0.exists(),
-            old_date.as_ref().map(|s| &**s),
+            exists: self.0.exists(),
+            old_date: old_date.as_ref().map(|s| &**s),
             components,
             targets,
-            &self,
-        )
+            distributable: &self,
+        }
         .install(&self.0)
     }
 
@@ -734,19 +734,19 @@ impl<'a> DistributableToolchain<'a> {
         let update_hash = self.update_hash()?;
         (self.0.cfg.notify_handler)(Notification::LookingForToolchain(&self.0.name));
         if !self.0.exists() {
-            Ok(InstallMethod::Dist(
-                &self.desc()?,
-                self.0.cfg.get_profile()?,
-                Some(&update_hash),
-                self.0.download_cfg(),
-                false,
-                false,
-                false,
-                None,
-                &[],
-                &[],
-                &self,
-            )
+            Ok(InstallMethod::Dist {
+                desc: &self.desc()?,
+                profile: self.0.cfg.get_profile()?,
+                update_hash: Some(&update_hash),
+                dl_cfg: self.0.download_cfg(),
+                force_update: false,
+                allow_downgrade: false,
+                exists: false,
+                old_date: None,
+                components: &[],
+                targets: &[],
+                distributable: &self,
+            }
             .install(&self.0)?)
         } else {
             (self.0.cfg.notify_handler)(Notification::UsingExistingToolchain(&self.0.name));