Add ui tests for test harness item walk and proc macro input gating

tests/ui/proc-macro/auxiliary/identity-attr.rs

@@ -0,0 +1,11 @@
+//@ force-host
+//@ no-prefer-dynamic
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::TokenStream;
+
+#[proc_macro_attribute]
+pub fn id(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    item
+}

tests/ui/proc-macro/macro-def-in-attr-input.rs

@@ -0,0 +1,18 @@
+//@ proc-macro: identity-attr.rs
+//@ edition: 2021
+//@ check-pass
+
+// `gate_proc_macro_input` walks attribute-macro input with the
+// `GateProcMacroInput` visitor; a `macro_rules!` definition inside the
+// annotated item makes that walk hit `visit_macro_def`, which nothing
+// else in the suite exercises.
+
+#[identity_attr::id]
+pub fn f() {
+    macro_rules! m {
+        () => {};
+    }
+    m!();
+}
+
+fn main() {}

tests/ui/unpretty/exhaustive.expanded.stdout

@@ -1,13 +1,19 @@
 #![feature(prelude_import)]
-//@ revisions: expanded hir
+//@ revisions: expanded hir harness
 //@[expanded]compile-flags: -Zunpretty=expanded
 //@[expanded]check-pass
 //@[hir]compile-flags: -Zunpretty=hir
 //@[hir]check-fail
+//@[harness]compile-flags: -Zunpretty=expanded --test
+//@[harness]check-pass
 //@ edition:2024
 
 // Note: the HIR revision includes a `.stderr` file because there are some
 // errors that only occur once we get past the AST.
+// The `harness` revision runs test-harness expansion (`--test`) over this
+// file, so the `InnerItemLinter` and `EntryPointCleaner` visitors in
+// rustc_builtin_macros walk the complete AST. `-Zunpretty=expanded` stops
+// before the analyses that make the `hir` revision fail.
 
 #![feature(auto_traits)]
 #![feature(box_patterns)]