Disallow unsafe in derive

2 files changed, 18 insertions, 1 deletions

diff --git a/compiler/rustc_builtin_macros/src/derive.rs b/compiler/rustc_builtin_macros/src/derive.rs
index d14858e5c1d..d70eaa617ca 100644
--- a/compiler/rustc_builtin_macros/src/derive.rs
+++ b/compiler/rustc_builtin_macros/src/derive.rs
@@ -2,7 +2,7 @@ use crate::cfg_eval::cfg_eval;
 use crate::errors;
 
 use rustc_ast as ast;
-use rustc_ast::{GenericParamKind, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
+use rustc_ast::{GenericParamKind, ItemKind, MetaItemKind, NestedMetaItem, StmtKind, Unsafe};
 use rustc_expand::base::{
     Annotatable, DeriveResolution, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier,
 };
@@ -60,6 +60,7 @@ impl MultiItemModifier for Expander {
                                 // Reject `#[derive(Debug = "value", Debug(abc))]`, but recover the
                                 // paths.
                                 report_path_args(sess, meta);
+                                report_unsafe_args(sess, meta);
                                 meta.path.clone()
                             })
                             .map(|path| DeriveResolution {
@@ -159,3 +160,12 @@ fn report_path_args(sess: &Session, meta: &ast::MetaItem) {
         }
     }
 }
+
+fn report_unsafe_args(sess: &Session, meta: &ast::MetaItem) {
+    match meta.unsafety {
+        Unsafe::Yes(span) => {
+            sess.dcx().emit_err(errors::DeriveUnsafePath { span });
+        }
+        Unsafe::No => {}
+    }
+}
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index d157703723b..b14eb2b5ee6 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -296,6 +296,13 @@ pub(crate) struct DerivePathArgsValue {
 }
 
 #[derive(Diagnostic)]
+#[diag(builtin_macros_derive_unsafe_path)]
+pub(crate) struct DeriveUnsafePath {
+    #[primary_span]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(builtin_macros_no_default_variant)]
 #[help]
 pub(crate) struct NoDefaultVariant {