Move error mapping out of validation function

Author: djc

src/cli/self_update.rs

@@ -140,32 +140,19 @@ impl<'a> InstallOpts<'a> {
     fn validate(&self) -> Result<()> {
         common::warn_if_host_is_emulated();
 
-        // Verify that the installation options are vaguely sane
-        (|| {
-            let host_triple = self
-                .default_host_triple
-                .as_ref()
-                .map(dist::TargetTriple::new)
-                .unwrap_or_else(TargetTriple::from_host_or_build);
-            let partial_channel = match &self.default_toolchain {
-                None | Some(MaybeOfficialToolchainName::None) => {
-                    ResolvableToolchainName::try_from("stable")?
-                }
-                Some(MaybeOfficialToolchainName::Some(s)) => s.into(),
-            };
-            let resolved = partial_channel.resolve(&host_triple)?;
-            debug!("Successfully resolved installation toolchain as: {resolved}");
-            Ok(())
-        })()
-        .map_err(|e: Box<dyn std::error::Error>| {
-            anyhow!(
-                "Pre-checks for host and toolchain failed: {}\n\
-             If you are unsure of suitable values, the 'stable' toolchain is the default.\n\
-             Valid host triples look something like: {}",
-                e,
-                TargetTriple::from_host_or_build()
-            )
-        })?;
+        let host_triple = self
+            .default_host_triple
+            .as_ref()
+            .map(dist::TargetTriple::new)
+            .unwrap_or_else(TargetTriple::from_host_or_build);
+        let partial_channel = match &self.default_toolchain {
+            None | Some(MaybeOfficialToolchainName::None) => {
+                ResolvableToolchainName::try_from("stable")?
+            }
+            Some(MaybeOfficialToolchainName::Some(s)) => s.into(),
+        };
+        let resolved = partial_channel.resolve(&host_triple)?;
+        debug!("Successfully resolved installation toolchain as: {resolved}");
         Ok(())
     }
 }
@@ -456,7 +443,14 @@ pub(crate) async fn install(
         do_pre_install_sanity_checks(no_prompt)?;
     }
 
-    opts.validate()?;
+    opts.validate().map_err(|e| {
+        anyhow!(
+            "Pre-checks for host and toolchain failed: {e}\n\
+            If you are unsure of suitable values, the 'stable' toolchain is the default.\n\
+            Valid host triples look something like: {}",
+            TargetTriple::from_host_or_build()
+        )
+    })?;
 
     if !process()
         .var_os("RUSTUP_INIT_SKIP_EXISTENCE_CHECKS")