only stabilize -Clinker-features=-lld on x64 linux

Some combinations of opt-ins and other flags need more work to be
stabilized, so we can only stabilize the opt-outs.

Author: lqd

compiler/rustc_session/src/config.rs

@@ -474,22 +474,17 @@ impl LinkerFeaturesCli {
     /// The caller should ensure that e.g. `nightly_options::is_unstable_enabled()`
     /// returns false.
     pub(crate) fn check_unstable_variants(&self, target_tuple: &TargetTuple) -> Result<(), String> {
-        // `-C linker-features=[-+]lld` is only stable on x64 linux.
-        let check_lld = |features: LinkerFeatures, polarity: &str| {
-            let has_lld = features.is_lld_enabled();
-            if has_lld && target_tuple.tuple() != "x86_64-unknown-linux-gnu" {
-                return Err(format!(
-                    "`-C linker-features={polarity}lld` is unstable on the `{target_tuple}` \
+        // `-C linker-features=-lld` is only stable on x64 linux.
+        let has_minus_lld = self.disabled.is_lld_enabled();
+        if has_minus_lld && target_tuple.tuple() != "x86_64-unknown-linux-gnu" {
+            return Err(format!(
+                "`-C linker-features=-lld` is unstable on the `{target_tuple}` \
                     target. The `-Z unstable-options` flag must also be passed to use it on this target",
-                ));
-            }
-            Ok(())
-        };
-        check_lld(self.enabled, "+")?;
-        check_lld(self.disabled, "-")?;
+            ));
+        }
 
-        // Since only lld is stable, any non-lld feature used is unstable, and that's an error.
-        let unstable_enabled = self.enabled - LinkerFeatures::LLD;
+        // Any `+lld` or non-lld feature used is unstable, and that's an error.
+        let unstable_enabled = self.enabled;
         let unstable_disabled = self.disabled - LinkerFeatures::LLD;
         if !unstable_enabled.union(unstable_disabled).is_empty() {
             let unstable_features: Vec<_> = unstable_enabled
@@ -498,8 +493,8 @@ impl LinkerFeaturesCli {
                 .chain(unstable_disabled.iter().map(|f| format!("-{}", f.as_str().unwrap())))
                 .collect();
             return Err(format!(
-                "the requested `-C linker-features={}` are unstable, and also require the \
-                `-Z unstable-options` flag to be usable",
+                "`-C linker-features={}` is unstable, and also requires the \
+                `-Z unstable-options` flag to be used",
                 unstable_features.join(","),
             ));
         }

tests/run-make/rust-lld-link-script-provide/rmake.rs

@@ -12,6 +12,7 @@ fn main() {
         .input("main.rs")
         .arg("-Clinker-features=+lld")
         .arg("-Clink-self-contained=+linker")
+        .arg("-Zunstable-options")
         .link_arg("-Tscript.t")
         .run();
 }

tests/ui/linking/linker-features-lld-disallowed-target.positive.stderr

@@ -0,0 +1,20 @@
+// Check that only `-C linker-features=-lld` is stable on x64 linux. Any other value or target,
+// needs `-Z unstable-options`.
+
+// ignore-tidy-linelength
+
+//@ revisions: unstable_target_positive unstable_target_negative unstable_positive
+//@ [unstable_target_negative] compile-flags: --target=x86_64-unknown-linux-musl -C linker-features=-lld --crate-type=rlib
+//@ [unstable_target_negative] needs-llvm-components: x86
+//@ [unstable_target_positive] compile-flags: --target=x86_64-unknown-linux-musl -C linker-features=+lld --crate-type=rlib
+//@ [unstable_target_positive] needs-llvm-components: x86
+//@ [unstable_positive] compile-flags: --target=x86_64-unknown-linux-gnu -C linker-features=+lld --crate-type=rlib
+//@ [unstable_positive] needs-llvm-components: x86
+
+
+#![feature(no_core)]
+#![no_core]
+
+//[unstable_target_negative]~? ERROR `-C linker-features=-lld` is unstable on the `x86_64-unknown-linux-musl` target
+//[unstable_target_positive]~? ERROR `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options`
+//[unstable_positive]~? ERROR `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options`

tests/ui/linking/linker-features-lld-disallowed-target.rs

@@ -0,0 +1,2 @@
+error: `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options` flag to be used
+

tests/ui/linking/linker-features-lld-disallowed.rs

@@ -0,0 +1,2 @@
+error: `-C linker-features=+lld` is unstable, and also requires the `-Z unstable-options` flag to be used
+

tests/ui/linking/linker-features-lld-disallowed.unstable_positive.stderr

@@ -1,5 +1,4 @@
-// Check that only `-C linker-features=[+-]lld` is stable on x64 linux, and that other linker
-// features require using `-Z unstable-options`.
+// Check that non-lld linker features require using `-Z unstable-options`.
 //
 // Note that, currently, only `lld` is parsed on the CLI, but that other linker features can exist
 // internally (`cc`).