Fix ICE when use tree appears in docs

compiler/rustc_resolve/src/check_unused.rs

@@ -250,6 +250,13 @@ impl<'a, 'ra, 'tcx> AsMut<Resolver<'ra, 'tcx>> for UnusedImportCheckVisitor<'a,
 }
 
 impl<'a, 'ra, 'tcx> Visitor<'a> for UnusedImportCheckVisitor<'a, 'ra, 'tcx> {
+    // Don't walk into attributes because imports can appear
+    // inside (e.g #[doc = {use std::{io,fmt};}]). They have
+    // a different owner, so they will cause an ICE if we visit
+    // them. Note that this doc attribute is not valid and will
+    // be rejected during AST lowering.
+    fn visit_attribute(&mut self, _: &'a rustc_ast::Attribute) {}
+
     fn visit_item(&mut self, item: &'a ast::Item) {
         self.item_span = item.span_with_attributes();
         match &item.kind {

tests/ui/attributes/use-tree-in-docs.rs

@@ -0,0 +1,7 @@
+// Don't ICE when use tree appears in docs. (#163355)
+#![feature(generic_assert)]
+#[doc = assert !(b)]
+//~^ ERROR attribute value must be a literal
+use std as x;
+
+fn main(){}

tests/ui/attributes/use-tree-in-docs.stderr

@@ -0,0 +1,8 @@
+error: attribute value must be a literal
+  --> $DIR/use-tree-in-docs.rs:3:9
+   |
+LL | #[doc = assert !(b)]
+   |         ^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+