Add explanation for E0116 and update the error message.

Also updates the reference on this point.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/doc/reference.md b/src/doc/reference.md
index 8d57238dc17..2a0f7b659d1 100644
--- a/src/doc/reference.md
+++ b/src/doc/reference.md
@@ -1550,7 +1550,7 @@ methods in such an implementation can only be used as direct calls on the
 values of the type that the implementation targets. In such an implementation,
 the trait type and `for` after `impl` are omitted. Such implementations are
 limited to nominal types (enums, structs), and the implementation must appear
-in the same module or a sub-module as the `self` type:
+in the same crate as the `self` type:
 
 ```
 struct Point {x: i32, y: i32}