Add rust-invalid ABI

compiler/rustc_abi/src/extern_abi.rs

@@ -36,6 +36,10 @@ pub enum ExternAbi {
     /// Stronger than just `#[cold]` because `fn` pointers might be incompatible.
     RustCold,
 
+    /// An always-invalid ABI that's used to test "this ABI is not supported by this platform"
+    /// in a platform-agnostic way.
+    RustInvalid,
+
     /// Unstable impl detail that directly uses Rust types to describe the ABI to LLVM.
     /// Even normally-compatible Rust types can become ABI-incompatible with this ABI!
     Unadjusted,
@@ -157,6 +161,7 @@ fn from_str(s: &str) -> Result<$e_name, Self::Err> {
             RiscvInterruptS =><= "riscv-interrupt-s",
             RustCall =><= "rust-call",
             RustCold =><= "rust-cold",
+            RustInvalid =><= "rust-invalid",
             Stdcall { unwind: false } =><= "stdcall",
             Stdcall { unwind: true } =><= "stdcall-unwind",
             System { unwind: false } =><= "system",

compiler/rustc_ast_lowering/src/stability.rs

@@ -96,6 +96,9 @@ pub fn extern_abi_stability(abi: ExternAbi) -> Result<(), UnstableAbi> {
         ExternAbi::RustCold => {
             Err(UnstableAbi { abi, feature: sym::rust_cold_cc, explain: GateReason::Experimental })
         }
+        ExternAbi::RustInvalid => {
+            Err(UnstableAbi { abi, feature: sym::rustc_attrs, explain: GateReason::ImplDetail })
+        }
         ExternAbi::GpuKernel => Err(UnstableAbi {
             abi,
             feature: sym::abi_gpu_kernel,

compiler/rustc_middle/src/ty/layout.rs

@@ -1253,7 +1253,8 @@ pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: ExternAbi)
         | CCmseNonSecureCall
         | CCmseNonSecureEntry
         | Custom
-        | Unadjusted => false,
+        | Unadjusted
+        | RustInvalid => false,
         Rust | RustCall | RustCold => tcx.sess.panic_strategy() == PanicStrategy::Unwind,
     }
 }

compiler/rustc_smir/src/rustc_internal/internal.rs

@@ -494,6 +494,7 @@ fn internal<'tcx>(&self, _tables: &mut Tables<'_>, _tcx: TyCtxt<'tcx>) -> Self::
             Abi::RustCall => rustc_abi::ExternAbi::RustCall,
             Abi::Unadjusted => rustc_abi::ExternAbi::Unadjusted,
             Abi::RustCold => rustc_abi::ExternAbi::RustCold,
+            Abi::RustInvalid => rustc_abi::ExternAbi::RustInvalid,
             Abi::RiscvInterruptM => rustc_abi::ExternAbi::RiscvInterruptM,
             Abi::RiscvInterruptS => rustc_abi::ExternAbi::RiscvInterruptS,
             Abi::Custom => rustc_abi::ExternAbi::Custom,

compiler/rustc_smir/src/rustc_smir/convert/ty.rs

@@ -877,6 +877,7 @@ fn stable(&self, _: &mut Tables<'_>) -> Self::T {
             ExternAbi::RustCall => Abi::RustCall,
             ExternAbi::Unadjusted => Abi::Unadjusted,
             ExternAbi::RustCold => Abi::RustCold,
+            ExternAbi::RustInvalid => Abi::RustInvalid,
             ExternAbi::RiscvInterruptM => Abi::RiscvInterruptM,
             ExternAbi::RiscvInterruptS => Abi::RiscvInterruptS,
             ExternAbi::Custom => Abi::Custom,

compiler/rustc_smir/src/stable_mir/ty.rs

@@ -1126,6 +1126,7 @@ pub enum Abi {
     RustCold,
     RiscvInterruptM,
     RiscvInterruptS,
+    RustInvalid,
     Custom,
 }
 

compiler/rustc_target/src/spec/abi_map.rs

@@ -156,7 +156,8 @@ pub fn canonize_abi(&self, extern_abi: ExternAbi, has_c_varargs: bool) -> AbiMap
                 | ExternAbi::Msp430Interrupt
                 | ExternAbi::RiscvInterruptM
                 | ExternAbi::RiscvInterruptS
-                | ExternAbi::X86Interrupt,
+                | ExternAbi::X86Interrupt
+                | ExternAbi::RustInvalid,
                 _,
             ) => return AbiMapping::Invalid,
         };

tests/ui/abi/invalid-call-abi.rs

@@ -0,0 +1,12 @@
+// Tests the `"rustc-invalid"` ABI, which is never canonizable.
+
+#![feature(rustc_attrs)]
+
+const extern "rust-invalid" fn foo() {
+    //~^ ERROR "rust-invalid" is not a supported ABI for the current target
+    panic!()
+}
+
+fn main() {
+    foo();
+}

tests/ui/abi/invalid-call-abi.stderr

@@ -0,0 +1,9 @@
+error[E0570]: "rust-invalid" is not a supported ABI for the current target
+  --> $DIR/invalid-call-abi.rs:5:14
+   |
+LL | const extern "rust-invalid" fn foo() {
+   |              ^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0570`.

tests/ui/print-calling-conventions.stdout

@@ -20,6 +20,7 @@ riscv-interrupt-m
 riscv-interrupt-s
 rust-call
 rust-cold
+rust-invalid
 stdcall
 stdcall-unwind
 system