Rollup merge of #67054 - RalfJung:set-discriminant-unreachable, r=oli-obk

codegen "unreachable" for invalid SetDiscriminant

Follow-up from https://github.com/rust-lang/rust/pull/66960. I also realized I don't understand our policy for using `abort` vs `unreachable`. AFAIK `abort` is safe to call and just aborts the process, while `unreachable` is UB. But sometimes we use both, like here

https://github.com/rust-lang/rust/blob/d825e35ee8325146e6c175a4c61bcb645b347d5e/src/librustc_codegen_ssa/mir/block.rs#L827-L828

and here

https://github.com/rust-lang/rust/blob/d825e35ee8325146e6c175a4c61bcb645b347d5e/src/librustc_codegen_ssa/mir/block.rs#L264-L265

The second case is even more confusing because that looks like an unreachable `return` to me, so why would we codegen a safe abort there?

r? @eddyb Cc @oli-obk

1 files changed, 43 insertions, 0 deletions

diff --git a/src/test/codegen/set-discriminant-invalid.rs b/src/test/codegen/set-discriminant-invalid.rs
new file mode 100644
index 00000000000..d9614f062b7
--- /dev/null
+++ b/src/test/codegen/set-discriminant-invalid.rs
@@ -0,0 +1,43 @@
+// compile-flags: -C opt-level=0
+#![crate_type = "lib"]
+
+pub enum ApiError {}
+#[allow(dead_code)]
+pub struct TokioError {
+    b: bool,
+}
+pub enum Error {
+    Api {
+        source: ApiError,
+    },
+    Ethereum,
+    Tokio {
+        source: TokioError,
+    },
+}
+struct Api;
+impl IntoError<Error> for Api
+{
+    type Source = ApiError;
+    // CHECK-LABEL: @into_error
+    // CHECK: llvm.trap()
+    // Also check the next two instructions to make sure we do not match against `trap`
+    // elsewhere in the code.
+    // CHECK-NEXT: load
+    // CHECK-NEXT: ret
+    #[no_mangle]
+    fn into_error(self, error: Self::Source) -> Error {
+        Error::Api {
+            source: (|v| v)(error),
+        }
+    }
+}
+
+pub trait IntoError<E>
+{
+    /// The underlying error
+    type Source;
+
+    /// Combine the information to produce the error
+    fn into_error(self, source: Self::Source) -> E;
+}