1 files changed, 147 insertions, 0 deletions
diff --git a/compiler/rustc_ast_lowering/src/stability.rs b/compiler/rustc_ast_lowering/src/stability.rs
new file mode 100644
index 00000000000..e7c166850a4
--- /dev/null
+++ b/compiler/rustc_ast_lowering/src/stability.rs
@@ -0,0 +1,147 @@
+use std::fmt;
+
+use rustc_abi::ExternAbi;
+use rustc_feature::Features;
+use rustc_session::Session;
+use rustc_session::parse::feature_err;
+use rustc_span::symbol::sym;
+use rustc_span::{Span, Symbol};
+
+pub(crate) fn enabled_names(features: &rustc_feature::Features, span: Span) -> Vec<&'static str> {
+    rustc_abi::AbiDatas
+        .iter()
+        .filter(|data| extern_abi_enabled(features, span, data.abi).is_ok())
+        .map(|d| d.name)
+        .collect()
+}
+
+pub(crate) fn extern_abi_enabled(
+    features: &rustc_feature::Features,
+    span: Span,
+    abi: ExternAbi,
+) -> Result<(), UnstableAbi> {
+    extern_abi_stability(abi).or_else(|unstable @ UnstableAbi { feature, .. }| {
+        if features.enabled(feature) || span.allows_unstable(feature) {
+            Ok(())
+        } else {
+            Err(unstable)
+        }
+    })
+}
+
+#[allow(rustc::untranslatable_diagnostic)]
+pub(crate) fn gate_unstable_abi(sess: &Session, features: &Features, span: Span, abi: ExternAbi) {
+    match extern_abi_enabled(features, span, abi) {
+        Ok(_) => (),
+        Err(unstable_abi) => {
+            let explain = unstable_abi.to_string();
+            feature_err(sess, unstable_abi.feature, span, explain).emit();
+        }
+    }
+}
+
+pub struct UnstableAbi {
+    abi: ExternAbi,
+    feature: Symbol,
+    explain: GateReason,
+}
+
+enum GateReason {
+    Experimental,
+    ImplDetail,
+}
+
+impl fmt::Display for UnstableAbi {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self { abi, .. } = self;
+        let name = abi.to_string();
+        let name = name.trim_matches('"');
+        match self.explain {
+            GateReason::Experimental => {
+                write!(f, r#"the extern "{name}" ABI is experimental and subject to change"#)
+            }
+            GateReason::ImplDetail => {
+                write!(
+                    f,
+                    r#"the extern "{name}" ABI is an implementation detail and perma-unstable"#
+                )
+            }
+        }
+    }
+}
+
+pub fn extern_abi_stability(abi: ExternAbi) -> Result<(), UnstableAbi> {
+    match abi {
+        // stable ABIs
+        ExternAbi::Rust
+        | ExternAbi::C { .. }
+        | ExternAbi::Cdecl { .. }
+        | ExternAbi::Stdcall { .. }
+        | ExternAbi::Fastcall { .. }
+        | ExternAbi::Thiscall { .. }
+        | ExternAbi::Aapcs { .. }
+        | ExternAbi::Win64 { .. }
+        | ExternAbi::SysV64 { .. }
+        | ExternAbi::System { .. }
+        | ExternAbi::EfiApi => Ok(()),
+        // implementation details
+        ExternAbi::RustIntrinsic => {
+            Err(UnstableAbi { abi, feature: sym::intrinsics, explain: GateReason::ImplDetail })
+        }
+        ExternAbi::Unadjusted => {
+            Err(UnstableAbi { abi, feature: sym::abi_unadjusted, explain: GateReason::ImplDetail })
+        }
+        // experimental
+        ExternAbi::Vectorcall { .. } => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_vectorcall,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::RustCall => Err(UnstableAbi {
+            abi,
+            feature: sym::unboxed_closures,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::RustCold => {
+            Err(UnstableAbi { abi, feature: sym::rust_cold_cc, explain: GateReason::Experimental })
+        }
+        ExternAbi::GpuKernel => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_gpu_kernel,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::PtxKernel => {
+            Err(UnstableAbi { abi, feature: sym::abi_ptx, explain: GateReason::Experimental })
+        }
+        ExternAbi::Msp430Interrupt => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_msp430_interrupt,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::X86Interrupt => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_x86_interrupt,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::AvrInterrupt | ExternAbi::AvrNonBlockingInterrupt => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_avr_interrupt,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::RiscvInterruptM | ExternAbi::RiscvInterruptS => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_riscv_interrupt,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::CCmseNonSecureCall => Err(UnstableAbi {
+            abi,
+            feature: sym::abi_c_cmse_nonsecure_call,
+            explain: GateReason::Experimental,
+        }),
+        ExternAbi::CCmseNonSecureEntry => Err(UnstableAbi {
+            abi,
+            feature: sym::cmse_nonsecure_entry,
+            explain: GateReason::Experimental,
+        }),
+    }
+}