Test for misusing attribute

compiler/rustc_middle/src/query/mod.rs

@@ -1137,7 +1137,7 @@ rustc_queries! {
     }
 
     query impl_constness(def_id: DefId) -> hir::Constness {
-        desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
+        desc { |tcx| "looking up whether `{}` is a const impl", tcx.def_path_str(def_id) }
     }
 
     query check_item_well_formed(key: LocalDefId) -> () {

src/test/ui/rfc-2632-const-trait-impl/attr-misuse.rs

@@ -0,0 +1,14 @@
+#![feature(const_trait_impl)]
+#![allow(incomplete_features)]
+
+#[default_method_body_is_const] //~ ERROR attribute should be applied
+trait A {
+    #[default_method_body_is_const] //~ ERROR attribute should be applied
+    fn no_body(self);
+
+    #[default_method_body_is_const]
+    fn correct_use(&self) {}
+}
+
+#[default_method_body_is_const] //~ ERROR attribute should be applied
+fn main() {}

src/test/ui/rfc-2632-const-trait-impl/attr-misuse.stderr

@@ -0,0 +1,32 @@
+error: attribute should be applied to a trait method with body
+  --> $DIR/attr-misuse.rs:4:1
+   |
+LL |   #[default_method_body_is_const]
+   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / trait A {
+LL | |     #[default_method_body_is_const]
+LL | |     fn no_body(self);
+LL | |
+LL | |     #[default_method_body_is_const]
+LL | |     fn correct_use(&self) {}
+LL | | }
+   | |_- not a trait method or missing a body
+
+error: attribute should be applied to a trait method with body
+  --> $DIR/attr-misuse.rs:13:1
+   |
+LL | #[default_method_body_is_const]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | fn main() {}
+   | ------------ not a trait method or missing a body
+
+error: attribute should be applied to a trait method with body
+  --> $DIR/attr-misuse.rs:6:5
+   |
+LL |     #[default_method_body_is_const]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     fn no_body(self);
+   |     ----------------- not a trait method or missing a body
+
+error: aborting due to 3 previous errors
+