Place compile-fail expected errors on their own line

test_suite/tests/compile-fail/conflict/adjacent-tag.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: 12:10: 12:19: enum tags `conflict` for type and content conflict with each other
+#[derive(Serialize)]
 #[serde(tag = "conflict", content = "conflict")]
+//~^^ ERROR: enum tags `conflict` for type and content conflict with each other
 enum E {
     A,
     B,

test_suite/tests/compile-fail/conflict/flatten-newtype-struct.rs

@@ -9,7 +9,8 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: 12:10: 12:19: #[serde(flatten)] cannot be used on newtype structs
+#[derive(Serialize)]
 struct Foo(#[serde(flatten)] HashMap<String, String>);
+//~^^ ERROR: #[serde(flatten)] cannot be used on newtype structs
 
 fn main() {}

test_suite/tests/compile-fail/conflict/flatten-skip-deserializing.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Deserialize)] //~ ERROR: 12:10: 12:21: #[serde(flatten] can not be combined with #[serde(skip_deserializing)]
+#[derive(Deserialize)]
 struct Foo {
     #[serde(flatten, skip_deserializing)]
+    //~^^^ ERROR: #[serde(flatten] can not be combined with #[serde(skip_deserializing)]
     other: Other,
 }
 

test_suite/tests/compile-fail/conflict/flatten-skip-serializing-if.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: 12:10: 12:19: #[serde(flatten] can not be combined with #[serde(skip_serializing_if = "...")]
+#[derive(Serialize)]
 struct Foo {
     #[serde(flatten, skip_serializing_if="Option::is_none")]
+    //~^^^ ERROR: #[serde(flatten] can not be combined with #[serde(skip_serializing_if = "...")]
     other: Option<Other>,
 }
 

test_suite/tests/compile-fail/conflict/flatten-skip-serializing.rs

@@ -9,9 +9,10 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: 12:10: 12:19: #[serde(flatten] can not be combined with #[serde(skip_serializing)]
+#[derive(Serialize)]
 struct Foo {
     #[serde(flatten, skip_serializing)]
+    //~^^^ ERROR: #[serde(flatten] can not be combined with #[serde(skip_serializing)]
     other: Other,
 }
 

test_suite/tests/compile-fail/conflict/flatten-tuple-struct.rs

@@ -9,7 +9,8 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: 12:10: 12:19: #[serde(flatten)] cannot be used on tuple structs
+#[derive(Serialize)]
 struct Foo(u32, #[serde(flatten)] HashMap<String, String>);
+//~^^ ERROR: #[serde(flatten)] cannot be used on tuple structs
 
 fn main() {}

test_suite/tests/compile-fail/conflict/internal-tag.rs

@@ -9,8 +9,9 @@
 #[macro_use]
 extern crate serde_derive;
 
-#[derive(Serialize)] //~ ERROR: 12:10: 12:19: variant field name `conflict` conflicts with internal tag
+#[derive(Serialize)]
 #[serde(tag = "conflict")]
+//~^^ ERROR: variant field name `conflict` conflicts with internal tag
 enum E {
     A {
         #[serde(rename = "conflict")]