Implement RFC 3525.

2 files changed, 37 insertions, 5 deletions

diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index d1dac9ca6da..9b3de24e1a6 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -746,12 +746,35 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             Target::Field | Target::Arm | Target::MacroDef => {
                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "target_feature");
             }
+            Target::Struct if self.tcx.features().struct_target_features => {
+                let ty = self.tcx.hir_node(hir_id).expect_item();
+                match ty.kind {
+                    ItemKind::Struct(data, _) => {
+                        if data.fields().len() != 0 {
+                            self.dcx().emit_err(errors::AttrShouldBeAppliedToFnOrUnitStruct {
+                                attr_span: attr.span,
+                                defn_span: span,
+                            });
+                        }
+                    }
+                    _ => {
+                        panic!("Target::Struct for a non-struct");
+                    }
+                }
+            }
             _ => {
-                self.dcx().emit_err(errors::AttrShouldBeAppliedToFn {
-                    attr_span: attr.span,
-                    defn_span: span,
-                    on_crate: hir_id == CRATE_HIR_ID,
-                });
+                if self.tcx.features().struct_target_features {
+                    self.dcx().emit_err(errors::AttrShouldBeAppliedToFnOrUnitStruct {
+                        attr_span: attr.span,
+                        defn_span: span,
+                    });
+                } else {
+                    self.dcx().emit_err(errors::AttrShouldBeAppliedToFn {
+                        attr_span: attr.span,
+                        defn_span: span,
+                        on_crate: hir_id == CRATE_HIR_ID,
+                    });
+                }
             }
         }
     }
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 1202351bdcd..32db0823cf7 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -83,6 +83,15 @@ pub struct AttrShouldBeAppliedToFn {
 }
 
 #[derive(Diagnostic)]
+#[diag(passes_should_be_applied_to_fn_or_unit_struct)]
+pub struct AttrShouldBeAppliedToFnOrUnitStruct {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(passes_should_be_applied_to_fn, code = E0739)]
 pub struct TrackedCallerWrongLocation {
     #[primary_span]