Require passing an `AttrWrapper` to `collect_tokens_trailing_token`

This is a pure refactoring split out from #80689.
It represents the most invasive part of that PR, requiring changes in
every caller of `parse_outer_attributes`

In order to eagerly expand `#[cfg]` attributes while preserving the
original `TokenStream`, we need to know the range of tokens that
corresponds to every attribute target. This is accomplished by making
`parse_outer_attributes` return an opaque `AttrWrapper` struct. An
`AttrWrapper` must be converted to a plain `AttrVec` by passing it to
`collect_tokens_trailing_token`. This makes it difficult to accidentally
construct an AST node with attributes without calling `collect_tokens_trailing_token`,
since AST nodes store an `AttrVec`, not an `AttrWrapper`.

As a result, we now call `collect_tokens_trailing_token` for attribute
targets which only support inert attributes, such as generic arguments
and struct fields. Currently, the constructed `LazyTokenStream` is
simply discarded. Future PRs will record the token range corresponding
to the attribute target, allowing those tokens to be removed from an
enclosing `collect_tokens_trailing_token` call if necessary.

1 files changed, 15 insertions, 0 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 2ddcb9ef844..cd0ad2b0150 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -2975,3 +2975,18 @@ macro_rules! derive_has_tokens {
 derive_has_tokens! {
     Item, Expr, Ty, AttrItem, Visibility, Path, Block, Pat
 }
+
+macro_rules! derive_has_attrs_no_tokens {
+    ($($ty:path),*) => { $(
+        impl HasTokens for $ty {
+            fn finalize_tokens(&mut self, _tokens: LazyTokenStream) {}
+        }
+    )* }
+}
+
+// These ast nodes only support inert attributes, so they don't
+// store tokens (since nothing can observe them)
+derive_has_attrs_no_tokens! {
+    StructField, Arm,
+    Field, FieldPat, Variant, Param, GenericParam
+}