Improve overall quality of compile_error! errors

Also updates UI tests.

test_suite/tests/ui/duplicate-attribute/rename-and-ser.stderr

@@ -1,8 +1,8 @@
 error: unknown serde field attribute `serialize`
- --> $DIR/rename-and-ser.rs:4:10
+ --> $DIR/rename-and-ser.rs:6:27
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+6 |     #[serde(rename = "x", serialize = "y")]
+  |                           ^^^^^^^^^
 
 error: aborting due to previous error
 

test_suite/tests/ui/duplicate-attribute/rename-rename-de.stderr

@@ -1,8 +1,8 @@
 error: duplicate serde attribute `rename`
- --> $DIR/rename-rename-de.rs:4:10
+ --> $DIR/rename-rename-de.rs:7:13
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+7 |     #[serde(rename(deserialize = "y"))]
+  |             ^^^^^^
 
 error: aborting due to previous error
 

test_suite/tests/ui/duplicate-attribute/rename-ser-rename-ser.stderr

@@ -1,8 +1,8 @@
 error: duplicate serde attribute `rename`
- --> $DIR/rename-ser-rename-ser.rs:4:10
+ --> $DIR/rename-ser-rename-ser.rs:6:38
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+6 |     #[serde(rename(serialize = "x"), rename(serialize = "y"))]
+  |                                      ^^^^^^
 
 error: aborting due to previous error
 

test_suite/tests/ui/duplicate-attribute/rename-ser-rename.stderr

@@ -1,8 +1,8 @@
 error: duplicate serde attribute `rename`
- --> $DIR/rename-ser-rename.rs:4:10
+ --> $DIR/rename-ser-rename.rs:7:13
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+7 |     #[serde(rename = "y")]
+  |             ^^^^^^
 
 error: aborting due to previous error
 

test_suite/tests/ui/duplicate-attribute/rename-ser-ser.stderr

@@ -1,8 +1,8 @@
 error: duplicate serde attribute `rename`
- --> $DIR/rename-ser-ser.rs:4:10
+ --> $DIR/rename-ser-ser.rs:6:37
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+6 |     #[serde(rename(serialize = "x", serialize = "y"))]
+  |                                     ^^^^^^^^^
 
 error: aborting due to previous error
 

test_suite/tests/ui/duplicate-attribute/two-rename-ser.stderr

@@ -1,8 +1,8 @@
 error: duplicate serde attribute `rename`
- --> $DIR/two-rename-ser.rs:4:10
+ --> $DIR/two-rename-ser.rs:7:13
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+7 |     #[serde(rename(serialize = "y"))]
+  |             ^^^^^^
 
 error: aborting due to previous error
 

test_suite/tests/ui/duplicate-attribute/with-and-serialize-with.stderr

@@ -1,8 +1,8 @@
 error: duplicate serde attribute `serialize_with`
- --> $DIR/with-and-serialize-with.rs:4:10
+ --> $DIR/with-and-serialize-with.rs:6:25
   |
-4 | #[derive(Serialize)]
-  |          ^^^^^^^^^
+6 |     #[serde(with = "w", serialize_with = "s")]
+  |                         ^^^^^^^^^^^^^^
 
 error: aborting due to previous error