Implement the unsafe-fields RFC.

Co-Authored-By: Jacob Pratt <jacob@jhpratt.dev>

1 files changed, 20 insertions, 2 deletions

diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index fddbf5896ad..26e81b7676b 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1791,6 +1791,17 @@ impl<'a> Parser<'a> {
         Ok((fields, recovered))
     }
 
+    fn parse_unsafe_field(&mut self) -> Safety {
+        // not using parse_safety as that also accepts `safe`.
+        if self.eat_keyword(kw::Unsafe) {
+            let span = self.prev_token.span;
+            self.psess.gated_spans.gate(sym::unsafe_fields, span);
+            Safety::Unsafe(span)
+        } else {
+            Safety::Default
+        }
+    }
+
     pub(super) fn parse_tuple_struct_body(&mut self) -> PResult<'a, ThinVec<FieldDef>> {
         // This is the case where we find `struct Foo<T>(T) where T: Copy;`
         // Unit like structs are handled in parse_item_struct function
@@ -1814,6 +1825,8 @@ impl<'a> Parser<'a> {
                         return Err(err);
                     }
                 };
+                // Unsafe fields are not supported in tuple structs, as doing so would result in a
+                // parsing ambiguity for `struct X(unsafe fn())`.
                 let ty = match p.parse_ty() {
                     Ok(ty) => ty,
                     Err(err) => {
@@ -1828,6 +1841,7 @@ impl<'a> Parser<'a> {
                     FieldDef {
                         span: lo.to(ty.span),
                         vis,
+                        safety: Safety::Default,
                         ident: None,
                         id: DUMMY_NODE_ID,
                         ty,
@@ -1850,7 +1864,8 @@ impl<'a> Parser<'a> {
         self.collect_tokens(None, attrs, ForceCollect::No, |this, attrs| {
             let lo = this.token.span;
             let vis = this.parse_visibility(FollowedByType::No)?;
-            this.parse_single_struct_field(adt_ty, lo, vis, attrs)
+            let safety = this.parse_unsafe_field();
+            this.parse_single_struct_field(adt_ty, lo, vis, safety, attrs)
                 .map(|field| (field, Trailing::No, UsePreAttrPos::No))
         })
     }
@@ -1861,10 +1876,11 @@ impl<'a> Parser<'a> {
         adt_ty: &str,
         lo: Span,
         vis: Visibility,
+        safety: Safety,
         attrs: AttrVec,
     ) -> PResult<'a, FieldDef> {
         let mut seen_comma: bool = false;
-        let a_var = self.parse_name_and_ty(adt_ty, lo, vis, attrs)?;
+        let a_var = self.parse_name_and_ty(adt_ty, lo, vis, safety, attrs)?;
         if self.token == token::Comma {
             seen_comma = true;
         }
@@ -1992,6 +2008,7 @@ impl<'a> Parser<'a> {
         adt_ty: &str,
         lo: Span,
         vis: Visibility,
+        safety: Safety,
         attrs: AttrVec,
     ) -> PResult<'a, FieldDef> {
         let name = self.parse_field_ident(adt_ty, lo)?;
@@ -2017,6 +2034,7 @@ impl<'a> Parser<'a> {
             span: lo.to(self.prev_token.span),
             ident: Some(name),
             vis,
+            safety,
             id: DUMMY_NODE_ID,
             ty,
             attrs,