diff --git a/test_suite/tests/ui/conflict/alias-enum.rs b/test_suite/tests/ui/conflict/alias-enum.rs
index 52af74b97..faceae3e7 100644
--- a/test_suite/tests/ui/conflict/alias-enum.rs
+++ b/test_suite/tests/ui/conflict/alias-enum.rs
@@ -76,4 +76,6 @@ enum E3 {
     b,
 }
 
-fn main() {}
+fn main() {
+    @//fail
+}
diff --git a/test_suite/tests/ui/conflict/alias-enum.stderr b/test_suite/tests/ui/conflict/alias-enum.stderr
index 36e036f65..aa0ca687c 100644
--- a/test_suite/tests/ui/conflict/alias-enum.stderr
+++ b/test_suite/tests/ui/conflict/alias-enum.stderr
@@ -1,71 +1,79 @@
-error: alias `b` conflicts with deserialization name of other field
-  --> tests/ui/conflict/alias-enum.rs:8:9
+error: expected expression, found `@`
+  --> tests/ui/conflict/alias-enum.rs:80:5
    |
-8  | /         /// Expected error on "alias b", because this is a name of other field
-9  | |         /// Error on "alias a" is not expected because this is a name of this field
-10 | |         /// Error on "alias c" is not expected because field `c` is skipped
-11 | |         #[serde(alias = "a", alias = "b", alias = "c")]
-12 | |         a: (),
-   | |_____________^
+80 |     @//fail
+   |     ^ expected expression
 
-error: alias `c` already used by field a
-  --> tests/ui/conflict/alias-enum.rs:14:9
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:16:9
    |
-14 | /         /// Expected error on "alias c", because it is already used as alias of `a`
-15 | |         #[serde(alias = "c")]
-16 | |         b: (),
-   | |_____________^
+11 |         #[serde(alias = "a", alias = "b", alias = "c")]
+   |                                      --- matches all the relevant values
+...
+16 |         b: (),
+   |         ^ no value can reach this
+   |
+   = note: `#[warn(unreachable_patterns)]` on by default
+
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:15:25
+   |
+11 |         #[serde(alias = "a", alias = "b", alias = "c")]
+   |                                                   --- matches all the relevant values
+...
+15 |         #[serde(alias = "c")]
+   |                         ^^^ no value can reach this
 
-error: alias `c` conflicts with deserialization name of other field
-  --> tests/ui/conflict/alias-enum.rs:23:9
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:28:26
    |
-23 | /         /// Expected error on "alias c", because this is a name of other field after
-24 | |         /// applying rename rules
-25 | |         #[serde(alias = "b", alias = "c")]
-26 | |         a: (),
-   | |_____________^
+25 |         #[serde(alias = "b", alias = "c")]
+   |                                      --- matches all the relevant values
+...
+28 |         #[serde(rename = "c")]
+   |                          ^^^ no value can reach this
 
-error: alias `B` conflicts with deserialization name of other field
-  --> tests/ui/conflict/alias-enum.rs:34:9
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:38:9
    |
-34 | /         /// Expected error on "alias B", because this is a name of field after
-35 | |         /// applying rename rules
-36 | |         #[serde(alias = "B", alias = "c")]
-37 | |         a: (),
-   | |_____________^
+36 |         #[serde(alias = "B", alias = "c")]
+   |                         --- matches all the relevant values
+37 |         a: (),
+38 |         b: (),
+   |         ^ no value can reach this
 
-error: alias `b` conflicts with deserialization name of other variant
-  --> tests/ui/conflict/alias-enum.rs:44:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:52:5
    |
-44 | /     /// Expected error on "alias b", because this is a name of other variant
-45 | |     /// Error on "alias a" is not expected because this is a name of this variant
-46 | |     /// Error on "alias c" is not expected because variant `c` is skipped
-47 | |     #[serde(alias = "a", alias = "b", alias = "c")]
-48 | |     a,
-   | |_____^
+47 |     #[serde(alias = "a", alias = "b", alias = "c")]
+   |                                  --- matches all the relevant values
+...
+52 |     b,
+   |     ^ no value can reach this
 
-error: alias `c` already used by variant a
-  --> tests/ui/conflict/alias-enum.rs:50:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:51:21
    |
-50 | /     /// Expected error on "alias c", because it is already used as alias of `a`
-51 | |     #[serde(alias = "c")]
-52 | |     b,
-   | |_____^
+47 |     #[serde(alias = "a", alias = "b", alias = "c")]
+   |                                               --- matches all the relevant values
+...
+51 |     #[serde(alias = "c")]
+   |                     ^^^ no value can reach this
 
-error: alias `c` conflicts with deserialization name of other variant
-  --> tests/ui/conflict/alias-enum.rs:60:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:65:22
    |
-60 | /     /// Expected error on "alias c", because this is a name of other variant after
-61 | |     /// applying rename rules
-62 | |     #[serde(alias = "b", alias = "c")]
-63 | |     a,
-   | |_____^
+62 |     #[serde(alias = "b", alias = "c")]
+   |                                  --- matches all the relevant values
+...
+65 |     #[serde(rename = "c")]
+   |                      ^^^ no value can reach this
 
-error: alias `B` conflicts with deserialization name of other variant
-  --> tests/ui/conflict/alias-enum.rs:72:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias-enum.rs:76:5
    |
-72 | /     /// Expected error on "alias B", because this is a name of variant after
-73 | |     /// applying rename rules
-74 | |     #[serde(alias = "B", alias = "c")]
-75 | |     a,
-   | |_____^
+74 |     #[serde(alias = "B", alias = "c")]
+   |                     --- matches all the relevant values
+75 |     a,
+76 |     b,
+   |     ^ no value can reach this
diff --git a/test_suite/tests/ui/conflict/alias.rs b/test_suite/tests/ui/conflict/alias.rs
index f52a90586..3f6cee295 100644
--- a/test_suite/tests/ui/conflict/alias.rs
+++ b/test_suite/tests/ui/conflict/alias.rs
@@ -37,4 +37,6 @@ struct S3 {
     b: (),
 }
 
-fn main() {}
+fn main() {
+    @//fail
+}
diff --git a/test_suite/tests/ui/conflict/alias.stderr b/test_suite/tests/ui/conflict/alias.stderr
index 2115b21b1..7e665a630 100644
--- a/test_suite/tests/ui/conflict/alias.stderr
+++ b/test_suite/tests/ui/conflict/alias.stderr
@@ -1,35 +1,43 @@
-error: alias `b` conflicts with deserialization name of other field
- --> tests/ui/conflict/alias.rs:5:5
-  |
-5 | /     /// Expected error on "alias b", because this is a name of other field
-6 | |     /// Error on "alias a" is not expected because this is a name of this field
-7 | |     /// Error on "alias c" is not expected because field `c` is skipped
-8 | |     #[serde(alias = "a", alias = "b", alias = "c")]
-9 | |     a: (),
-  | |_________^
+error: expected expression, found `@`
+  --> tests/ui/conflict/alias.rs:41:5
+   |
+41 |     @//fail
+   |     ^ expected expression
+
+warning: unreachable pattern
+  --> tests/ui/conflict/alias.rs:13:5
+   |
+8  |     #[serde(alias = "a", alias = "b", alias = "c")]
+   |                                  --- matches all the relevant values
+...
+13 |     b: (),
+   |     ^ no value can reach this
+   |
+   = note: `#[warn(unreachable_patterns)]` on by default
 
-error: alias `c` already used by field a
-  --> tests/ui/conflict/alias.rs:11:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias.rs:12:21
    |
-11 | /     /// Expected error on "alias c", because it is already used as alias of `a`
-12 | |     #[serde(alias = "c")]
-13 | |     b: (),
-   | |_________^
+8  |     #[serde(alias = "a", alias = "b", alias = "c")]
+   |                                               --- matches all the relevant values
+...
+12 |     #[serde(alias = "c")]
+   |                     ^^^ no value can reach this
 
-error: alias `c` conflicts with deserialization name of other field
-  --> tests/ui/conflict/alias.rs:21:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias.rs:26:22
    |
-21 | /     /// Expected error on "alias c", because this is a name of other field after
-22 | |     /// applying rename rules
-23 | |     #[serde(alias = "b", alias = "c")]
-24 | |     a: (),
-   | |_________^
+23 |     #[serde(alias = "b", alias = "c")]
+   |                                  --- matches all the relevant values
+...
+26 |     #[serde(rename = "c")]
+   |                      ^^^ no value can reach this
 
-error: alias `B` conflicts with deserialization name of other field
-  --> tests/ui/conflict/alias.rs:33:5
+warning: unreachable pattern
+  --> tests/ui/conflict/alias.rs:37:5
    |
-33 | /     /// Expected error on "alias B", because this is a name of field after
-34 | |     /// applying rename rules
-35 | |     #[serde(alias = "B", alias = "c")]
-36 | |     a: (),
-   | |_________^
+35 |     #[serde(alias = "B", alias = "c")]
+   |                     --- matches all the relevant values
+36 |     a: (),
+37 |     b: (),
+   |     ^ no value can reach this