Unconditionally capture tokens for attributes.

This allows us to avoid synthesizing tokens in `prepend_attr`, since we
have the original tokens available.

We still need to synthesize tokens when expanding `cfg_attr`,
but this is an unavoidable consequence of the syntax of `cfg_attr` -
the user does not supply the `#` and `[]` tokens that a `cfg_attr`
expands to.

2 files changed, 8 insertions, 5 deletions

diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index c49fd76a313..a6ac056b93b 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -210,9 +210,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         ex.span = e.span;
                     }
                     // Merge attributes into the inner expression.
-                    let mut attrs = e.attrs.clone();
+                    let mut attrs: Vec<_> = e.attrs.iter().map(|a| self.lower_attr(a)).collect();
                     attrs.extend::<Vec<_>>(ex.attrs.into());
-                    ex.attrs = attrs;
+                    ex.attrs = attrs.into();
                     return ex;
                 }
 
@@ -1471,13 +1471,15 @@ impl<'hir> LoweringContext<'_, 'hir> {
             hir::MatchSource::ForLoopDesugar,
         ));
 
+        let attrs: Vec<_> = e.attrs.iter().map(|a| self.lower_attr(a)).collect();
+
         // This is effectively `{ let _result = ...; _result }`.
         // The construct was introduced in #21984 and is necessary to make sure that
         // temporaries in the `head` expression are dropped and do not leak to the
         // surrounding scope of the `match` since the `match` is not a terminating scope.
         //
         // Also, add the attributes to the outer returned expr node.
-        self.expr_drop_temps_mut(desugared_span, match_expr, e.attrs.clone())
+        self.expr_drop_temps_mut(desugared_span, match_expr, attrs.into())
     }
 
     /// Desugar `ExprKind::Try` from: `<expr>?` into:
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index a28d022c661..361bccd7a25 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -972,7 +972,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             AttrKind::DocComment(comment_kind, data) => AttrKind::DocComment(comment_kind, data),
         };
 
-        Attribute { kind, id: attr.id, style: attr.style, span: attr.span }
+        // Tokens aren't needed after macro expansion and parsing
+        Attribute { kind, id: attr.id, style: attr.style, span: attr.span, tokens: None }
     }
 
     fn lower_mac_args(&mut self, args: &MacArgs) -> MacArgs {
@@ -1713,7 +1714,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 pat: self.lower_pat(&l.pat),
                 init,
                 span: l.span,
-                attrs: l.attrs.clone(),
+                attrs: l.attrs.iter().map(|a| self.lower_attr(a)).collect::<Vec<_>>().into(),
                 source: hir::LocalSource::Normal,
             },
             ids,