Fixup tests for new unknown derive error

Author: keeperofdakeys

src/libsyntax_ext/deriving/mod.rs

@@ -247,14 +247,11 @@ pub fn expand_derive(cx: &mut ExtCtxt,
             ..mitem.span
         };
 
-        match cx.resolver.resolve_macro(cx.current_expansion.mark, &path, false) {
-            Ok(ext) => match *ext {
-                SyntaxExtension::CustomDerive(ref ext) =>
-                    return ext.expand(cx, span, &mitem, item),
-                _ => {},
-            },
-            _ => {},
-        };
+        if let Ok(ext) = cx.resolver.resolve_macro(cx.current_expansion.mark, &path, false) {
+            if let SyntaxExtension::CustomDerive(ref ext) = *ext {
+                return ext.expand(cx, span, &mitem, item),
+            }
+        }
 
         cx.span_err(span, &format!("cannot find derive macro `{}` in this scope", tname));
         return vec![item];

src/test/compile-fail/deriving-meta-unknown-trait.rs

@@ -11,7 +11,7 @@
 // ignore-tidy-linelength
 
 #[derive(Eqr)]
-//~^ ERROR `#[derive]` for custom traits is not stable enough for use. It is deprecated and will be removed in v1.15 (see issue #29644)
+//~^ ERROR cannot find derive macro `Eqr` in this scope
 struct Foo;
 
 pub fn main() {}

src/test/compile-fail/deriving-primitive.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[derive(FromPrimitive)] //~ERROR `#[derive]` for custom traits is not stable
+#[derive(FromPrimitive)] //~ERROR cannot find derive macro `FromPrimitive` in this scope
 enum Foo {}
 
 fn main() {}