From 8156fcb53559afc5a784494d24398f6950fa15a1 Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Thu, 31 Aug 2023 08:55:36 -0500
Subject: [PATCH] fix(cli): Help people find possible --target values

---
 src/cargo/util/command_prelude.rs  | 12 +++++++++++-
 tests/testsuite/list_availables.rs |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/cargo/util/command_prelude.rs b/src/cargo/util/command_prelude.rs
index 6ed1b8ed862f..aef8d0289afe 100644
--- a/src/cargo/util/command_prelude.rs
+++ b/src/cargo/util/command_prelude.rs
@@ -4,6 +4,7 @@ use crate::core::{Edition, Workspace};
 use crate::ops::{CompileFilter, CompileOptions, NewOptions, Packages, VersionControl};
 use crate::util::important_paths::find_root_manifest_for_wd;
 use crate::util::interning::InternedString;
+use crate::util::is_rustup;
 use crate::util::restricted_names::is_glob_pattern;
 use crate::util::toml::{StringOrVec, TomlProfile};
 use crate::util::validate_package_name;
@@ -445,7 +446,16 @@ pub trait ArgMatchesExt {
 
     fn targets(&self) -> CargoResult<Vec<String>> {
         if self.is_present_with_zero_values("target") {
-            bail!("\"--target\" takes an argument.");
+            let cmd = if is_rustup() {
+                "rustup target list"
+            } else {
+                "ustc --print target-list"
+            };
+            bail!(
+                "\"--target\" takes an argument.
+
+Run `{cmd}` to see possible targets."
+            );
         }
         Ok(self._values_of("target"))
     }
diff --git a/tests/testsuite/list_availables.rs b/tests/testsuite/list_availables.rs
index ec2f9bfabb3b..add90a7da8ac 100644
--- a/tests/testsuite/list_availables.rs
+++ b/tests/testsuite/list_availables.rs
@@ -167,6 +167,8 @@ No tests available.
             .with_stderr(
                 "\
 error: \"--target\" takes an argument.
+
+Run `[..]` to see possible targets.
 ",
             )
             .with_status(101)