Document #![register_tool]

tests/ui/tool-attributes/crate-attr.rs

@@ -0,0 +1,5 @@
+//@ check-pass
+//@ compile-flags: -Z crate-attr=feature(register_tool) -Z crate-attr=register_tool(foo)
+
+#[allow(foo::bar)]
+fn main() {}

tests/ui/tool-attributes/multiple-registered.rs

@@ -0,0 +1,7 @@
+//@ check-pass
+
+#![feature(register_tool)]
+#![register_tool(foo, bar, baz)]
+
+#[allow(foo::a, bar::b, baz::c)]
+fn main() {}

tests/ui/tool-attributes/nested-disallowed.rs

@@ -0,0 +1,4 @@
+#![feature(register_tool)]
+#![register_tool(foo::bar)] //~ ERROR only accepts identifiers
+
+fn main() {}

tests/ui/tool-attributes/nested-disallowed.stderr

@@ -0,0 +1,8 @@
+error: `register_tool` only accepts identifiers
+  --> $DIR/nested-disallowed.rs:2:18
+   |
+LL | #![register_tool(foo::bar)]
+   |                  ^^^^^^^^ not an identifier
+
+error: aborting due to 1 previous error
+