feat: add hint to run rustup self when err desc is 'self'

Author: Xerxes-2

src/dist/mod.rs

@@ -10,6 +10,7 @@ use once_cell::sync::Lazy;
 use regex::Regex;
 use serde::{Deserialize, Serialize};
 use thiserror::Error as ThisError;
+use tracing::info;
 
 use crate::{
     config::Cfg, currentprocess::Process, errors::RustupError, toolchain::ToolchainName,
@@ -319,7 +320,11 @@ impl FromStr for ParsedToolchainDesc {
         if let Some(d) = d {
             Ok(d)
         } else {
-            Err(RustupError::InvalidToolchainName(desc.to_string()).into())
+            let desc_string = desc.to_string();
+            if desc_string.as_str() == "self" {
+                info!("If you meant to modify rustup itself, try run `rustup self`");
+            }
+            Err(RustupError::InvalidToolchainName(desc_string).into())
         }
     }
 }