Clarify why target_feature is not allowed on the implementation of safe trait methods.

gnzlbg · gnzlbg · commit 6b9a16f56a24 · 2019-11-27T17:18:18.000+01:00
diff --git a/text/0000-target-feature-1.1.md b/text/0000-target-feature-1.1.md
@@ -128,7 +128,8 @@ The `#[target_feature]` attribute continues to be allowed on inherent methods -
 this RFC does not change that.
 
 The `#[target_feature]` attribute continues to not be allowed on safe trait
-method implementations:
+method implementations because that would require an `unsafe` trait method
+declaration:
 
 ```rust
 // Example 2:
