Fix attribute order implementation

Author: JonathanBrouwer

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -161,9 +161,9 @@ impl<T: SingleAttributeParser<S>, S: Stage> AttributeParser<S> for Single<T, S>
             if let Some(pa) = T::convert(cx, args) {
                 if let Some((_, used)) = group.1 {
                     T::ON_DUPLICATE.exec::<T>(cx, used, cx.attr_span);
+                } else {
+                    group.1 = Some((pa, cx.attr_span));
                 }
-
-                group.1 = Some((pa, cx.attr_span));
             }
         },
     )];

tests/ui/attributes/malformed-no-std.stderr

@@ -131,10 +131,10 @@ LL | #![no_std(foo = "bar")]
    | ^^^^^^^^^^^^^^^^^^^^^^^ help: remove this attribute
    |
 note: attribute also specified here
-  --> $DIR/malformed-no-std.rs:5:1
+  --> $DIR/malformed-no-std.rs:3:1
    |
-LL | #![no_std("bar")]
-   | ^^^^^^^^^^^^^^^^^
+LL | #![no_std = "foo"]
+   | ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
   --> $DIR/malformed-no-std.rs:13:1
@@ -155,10 +155,10 @@ LL | #![no_core(foo = "bar")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^ help: remove this attribute
    |
 note: attribute also specified here
-  --> $DIR/malformed-no-std.rs:13:1
+  --> $DIR/malformed-no-std.rs:11:1
    |
-LL | #![no_core("bar")]
-   | ^^^^^^^^^^^^^^^^^^
+LL | #![no_core = "foo"]
+   | ^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 8 previous errors; 4 warnings emitted