Rollup merge of #138160 - jdonszelmann:move-find-attr2, r=oli-obk

depend more on attr_data_structures and move find_attr! there

r?  ``@oli-obk``

This should be an easy one. It just moves some imports around. This is necessary for other changes that I'm working on not to have import cycles. However, it's an easy one to just merge on its own.

1 files changed, 44 insertions, 0 deletions

diff --git a/compiler/rustc_attr_data_structures/src/lib.rs b/compiler/rustc_attr_data_structures/src/lib.rs
index d90be4bd5fe..be00d1c10e0 100644
--- a/compiler/rustc_attr_data_structures/src/lib.rs
+++ b/compiler/rustc_attr_data_structures/src/lib.rs
@@ -148,3 +148,47 @@ print_tup!(A B C D E F G H);
 print_skip!(Span, ());
 print_disp!(Symbol, u16, bool, NonZero<u32>);
 print_debug!(UintTy, IntTy, Align, AttrStyle, CommentKind, Transparency);
+
+/// Finds attributes in sequences of attributes by pattern matching.
+///
+/// A little like `matches` but for attributes.
+///
+/// ```rust,ignore (illustrative)
+/// // finds the repr attribute
+/// if let Some(r) = find_attr!(attrs, AttributeKind::Repr(r) => r) {
+///
+/// }
+///
+/// // checks if one has matched
+/// if find_attr!(attrs, AttributeKind::Repr(_)) {
+///
+/// }
+/// ```
+///
+/// Often this requires you to first end up with a list of attributes.
+/// A common way to get those is through `tcx.get_all_attrs(did)`
+#[macro_export]
+macro_rules! find_attr {
+    ($attributes_list: expr, $pattern: pat $(if $guard: expr)?) => {{
+        $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
+    }};
+
+    ($attributes_list: expr, $pattern: pat $(if $guard: expr)? => $e: expr) => {{
+        fn check_attribute_iterator<'a>(_: &'_ impl IntoIterator<Item = &'a rustc_hir::Attribute>) {}
+        check_attribute_iterator(&$attributes_list);
+
+        let find_attribute = |iter| {
+            for i in $attributes_list {
+                match i {
+                    rustc_hir::Attribute::Parsed($pattern) $(if $guard)? => {
+                        return Some($e);
+                    }
+                    _ => {}
+                }
+            }
+
+            None
+        };
+        find_attribute($attributes_list)
+    }};
+}