Store process name in error variant directly

Author: djc

src/config.rs

@@ -165,9 +165,7 @@ impl OverrideCfg {
                     path.display()
                 )
             }
-            (None, None) => cfg
-                .get_default()?
-                .ok_or(RustupError::ToolchainNotSelected)?,
+            (None, None) => cfg.get_default()?.ok_or_else(no_toolchain_error)?,
         };
         Ok(match toolchain_name {
             ToolchainName::Official(desc) => {
@@ -692,7 +690,7 @@ impl Cfg {
     ) -> Result<(Toolchain<'_>, ActiveReason)> {
         self.maybe_find_or_install_active_toolchain(&self.current_dir)
             .await?
-            .ok_or(RustupError::ToolchainNotSelected.into())
+            .ok_or_else(no_toolchain_error)
     }
 
     #[cfg_attr(feature = "otel", tracing::instrument(skip_all))]
@@ -957,6 +955,10 @@ fn get_default_host_triple(s: &Settings) -> dist::TargetTriple {
         .unwrap_or_else(dist::TargetTriple::from_host_or_build)
 }
 
+fn no_toolchain_error() -> anyhow::Error {
+    RustupError::ToolchainNotSelected(process().name().unwrap_or_else(|| "Rust".into())).into()
+}
+
 /// Specifies how a `rust-toolchain`/`rust-toolchain.toml` configuration file should be parsed.
 enum ParseMode {
     /// Only permit TOML format in a configuration file.

src/errors.rs

@@ -10,10 +10,7 @@ use std::path::PathBuf;
 use thiserror::Error as ThisError;
 use url::Url;
 
-use crate::{
-    currentprocess::process,
-    dist::dist::{TargetTriple, ToolchainDesc},
-};
+use crate::dist::dist::{TargetTriple, ToolchainDesc};
 use crate::{
     dist::manifest::{Component, Manifest},
     toolchain::names::{PathBasedToolchainName, ToolchainName},
@@ -92,11 +89,10 @@ pub enum RustupError {
     #[error("path '{0}' not found")]
     PathToolchainNotInstalled(PathBasedToolchainName),
     #[error(
-        "rustup could not choose a version of {} to run, because one wasn't specified explicitly, and no default is configured.\n{}",
-        process().name().unwrap_or_else(|| "Rust".into()),
+        "rustup could not choose a version of {0} to run, because one wasn't specified explicitly, and no default is configured.\n{}",
         "help: run 'rustup default stable' to download the latest stable release of Rust and set it as your default toolchain."
     )]
-    ToolchainNotSelected,
+    ToolchainNotSelected(String),
     #[error("toolchain '{}' does not contain component {}{}{}", .desc, .component, suggest_message(.suggestion), if .component.contains("rust-std") {
         format!("\nnote: not all platforms have the standard library pre-compiled: https://doc.rust-lang.org/nightly/rustc/platform-support.html{}",
             if desc.channel == "nightly" { "\nhelp: consider using `cargo build -Z build-std` instead" } else { "" }