apply smart guess to rustup update/uninstall self

Use original error instead of rewriting

avoid duplicate `.to_string()`

remove unnecessary `.as_str()`

Author: Xerxes-2

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
                 }
             }