apply smart guess to rustup update/uninstall self

Use original error instead of rewriting

avoid duplicate `.to_string()`

remove unnecessary `.as_str()`

src/cli/rustup_mode.rs

@@ -3,6 +3,7 @@ use std::fmt;
 use std::io::Write;
 use std::path::{Path, PathBuf};
 use std::process::ExitStatus;
+use std::str::FromStr;
 
 use anyhow::{anyhow, Error, Result};
 use clap::{builder::PossibleValue, Args, CommandFactory, Parser, Subcommand, ValueEnum};
@@ -135,7 +136,7 @@ enum RustupSubcmd {
  )]
  Update {
  /// Toolchain name, such as 'stable', 'nightly', or '1.8.0'. For more information see `rustup help toolchain`
- #[arg(num_args = 1..)]
+ #[arg(num_args = 1.., value_parser = update_toolchain_value_parser)]
  toolchain: Vec<PartialToolchainDesc>,
 
  /// Don't perform self update when running the `rustup update` command
@@ -258,6 +259,14 @@ enum RustupSubcmd {
  },
 }
 
+fn update_toolchain_value_parser(s: &str) -> Result<PartialToolchainDesc> {
+ PartialToolchainDesc::from_str(s).inspect_err(|_| {
+ if s == "self" {
+ info!("if you meant to update rustup itself, use `rustup self update`");
+ }
+ })
+}
+
 #[derive(Debug, Subcommand)]
 enum ShowSubcmd {
  /// Show the active toolchain

src/toolchain.rs

@@ -457,7 +457,13 @@ impl<'a> Toolchain<'a> {
  fs::remove_dir_all(&path)?;
  true
  } else {
+ let name = name.to_string();
  info!("no toolchain installed for '{name}'");
+ if name == "self" {
+ info!(
+ "if you meant to uninstall rustup itself, use `rustup self uninstall`"
+ );
+ }
  false
  }
  }