Rollup merge of #48752 - alexcrichton:fix-target-feature, r=michaelwoerister

rustc: Fix ICE with `#[target_feature]` on module

This commit fixes an ICE in rustc when `#[target_feature]` was applied to items
other than functions due to the way the feature was validated.

src/test/ui/target-feature-wrong.rs

@@ -29,6 +29,10 @@ unsafe fn foo() {}
 //~^ ERROR: can only be applied to `unsafe` function
 fn bar() {}
 
+#[target_feature(enable = "sse2")]
+//~^ ERROR: should be applied to a function
+mod another {}
+
 fn main() {
     unsafe {
         foo();

src/test/ui/target-feature-wrong.stderr

@@ -28,5 +28,14 @@ error: #[target_feature(..)] can only be applied to `unsafe` function
 LL | #[target_feature(enable = "sse2")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: attribute should be applied to a function
+  --> $DIR/target-feature-wrong.rs:32:1
+   |
+LL | #[target_feature(enable = "sse2")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | //~^ ERROR: should be applied to a function
+LL | mod another {}
+   | -------------- not a function
+
+error: aborting due to 5 previous errors