Fix cycle error

Author: JohnTitor

compiler/rustc_typeck/src/collect.rs

@@ -2588,30 +2588,22 @@ fn simd_ffi_feature_check(
     }
 }
 
-fn simd_ffi_check<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    def_id: DefId,
-    ast_ty: &hir::Ty<'_>,
-    ty: Ty<'tcx>,
-) {
+fn simd_ffi_check<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ast_ty: &hir::Ty<'_>, ty: Ty<'tcx>) {
     if !ty.is_simd() {
         return;
     }
 
     // The use of SIMD types in FFI is feature-gated:
     if !tcx.features().simd_ffi {
         let snip = tcx
-                    .sess
-                    .source_map()
-                    .span_to_snippet(ast_ty.span)
-                    .map_or_else(|_| String::new(), |s| format!("{}", s));
+            .sess
+            .source_map()
+            .span_to_snippet(ast_ty.span)
+            .map_or_else(|_| String::new(), |s| format!("{}", s));
         tcx.sess
             .struct_span_err(
                 ast_ty.span,
-                &format!(
-                    "use of SIMD type `{}` in FFI is unstable",
-                    snip
-                ),
+                &format!("use of SIMD type `{}` in FFI is unstable", snip),
             )
             .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
             .emit();
@@ -2646,12 +2638,14 @@ fn simd_ffi_check<'tcx>(
     let target: &str = &tcx.sess.target.arch;
 
     for f in features {
-        if let Err(v) = simd_ffi_feature_check(target, simd_len, simd_elem_width, f.to_ident_string()) {
+        if let Err(v) =
+            simd_ffi_feature_check(target, simd_len, simd_elem_width, f.to_ident_string())
+        {
             let type_str = tcx
-                    .sess
-                    .source_map()
-                    .span_to_snippet(ast_ty.span)
-                    .map_or_else(|_| String::new(), |s| format!("{}", s));
+                .sess
+                .source_map()
+                .span_to_snippet(ast_ty.span)
+                .map_or_else(|_| String::new(), |s| format!("{}", s));
             let msg = if let Some(f) = v {
                 format!(
                     "use of SIMD type `{}` in FFI requires `#[target_feature(enable = \"{}\")]`",
@@ -2952,7 +2946,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
                 codegen_fn_attrs.export_name = Some(s);
             }
         } else if tcx.sess.check_name(attr, sym::target_feature) {
-            if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
+            if !tcx.is_closure(id)
+                && !tcx.is_foreign_item(id)
+                && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal
+            {
                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
                     // The `#[target_feature]` attribute is allowed on
                     // WebAssembly targets on all functions, including safe

src/test/ui/rfcs/rfc-2574-simd-ffi/simd-ffi-x86.rs

@@ -3,7 +3,7 @@
 #![feature(repr_simd)]
 #![feature(simd_ffi)]
 #![feature(avx512_target_feature)]
-#![allow(non_camel_case_types)]
+#![allow(non_camel_case_types, improper_ctypes)]
 #![cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 
 #[repr(simd)]

src/test/ui/rfcs/rfc-2574-simd-ffi/simd-ffi-x86.stderr

@@ -1,27 +1,20 @@
-error[E0391]: cycle detected when computing codegen attributes of `qux`
-  --> $DIR/simd-ffi-x86.rs:19:5
+error: use of SIMD type `v256` in FFI requires `#[target_feature(enable = "avx")]`
+  --> $DIR/simd-ffi-x86.rs:33:22
    |
-LL |     fn qux(x: v128);
-   |     ^^^^^^^^^^^^^^^^
-   |
-note: ...which requires computing function signature of `qux`...
-  --> $DIR/simd-ffi-x86.rs:19:5
+LL |     fn quux_fail2(x: v256);
+   |                      ^^^^
+
+error: use of SIMD type `v512` in FFI requires `#[target_feature(enable = "acx512")]`
+  --> $DIR/simd-ffi-x86.rs:43:23
    |
-LL |     fn qux(x: v128);
-   |     ^^^^^^^^^^^^^^^^
-   = note: ...which again requires computing codegen attributes of `qux`, completing the cycle
-note: cycle used when checking attributes in top-level module
-  --> $DIR/simd-ffi-x86.rs:3:1
+LL |     fn quuux_fail2(x: v512);
+   |                       ^^^^
+
+error: use of SIMD type `v512` in FFI requires `#[target_feature(enable = "acx512")]`
+  --> $DIR/simd-ffi-x86.rs:45:23
    |
-LL | / #![feature(repr_simd)]
-LL | | #![feature(simd_ffi)]
-LL | | #![feature(avx512_target_feature)]
-LL | | #![allow(non_camel_case_types)]
-...  |
-LL | | #[repr(simd)]
-LL | | struct v512(i128, i128, i128, i128);
-   | |____________________________________^
+LL |     fn quuux_fail3(x: v512);
+   |                       ^^^^
 
-error: aborting due to previous error
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0391`.