diff --git a/tests/ui/union/field_checks.rs b/tests/ui/union/field_checks.rs
index bb4eccb4cf896..6d5ddd52dfa56 100644
--- a/tests/ui/union/field_checks.rs
+++ b/tests/ui/union/field_checks.rs
@@ -1,3 +1,9 @@
+//@ reference: items.union.field-restrictions
+//@ reference: items.union.field-copy
+//@ reference: items.union.field-references
+//@ reference: items.union.field-manually-drop
+//@ reference: items.union.field-tuple
+//@ reference: type.union.constraint
 use std::mem::ManuallyDrop;
 
 union U1 { // OK
diff --git a/tests/ui/union/field_checks.stderr b/tests/ui/union/field_checks.stderr
index 32407a749709c..8c111cd940133 100644
--- a/tests/ui/union/field_checks.stderr
+++ b/tests/ui/union/field_checks.stderr
@@ -1,5 +1,5 @@
 error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
-  --> $DIR/field_checks.rs:24:5
+  --> $DIR/field_checks.rs:30:5
    |
 LL |     a: String,
    |     ^^^^^^^^^
@@ -11,7 +11,7 @@ LL |     a: std::mem::ManuallyDrop<String>,
    |        +++++++++++++++++++++++      +
 
 error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
-  --> $DIR/field_checks.rs:28:5
+  --> $DIR/field_checks.rs:34:5
    |
 LL |     a: std::cell::RefCell<i32>,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -23,7 +23,7 @@ LL |     a: std::mem::ManuallyDrop<std::cell::RefCell<i32>>,
    |        +++++++++++++++++++++++                       +
 
 error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
-  --> $DIR/field_checks.rs:32:5
+  --> $DIR/field_checks.rs:38:5
    |
 LL |     a: T,
    |     ^^^^
@@ -35,7 +35,7 @@ LL |     a: std::mem::ManuallyDrop<T>,
    |        +++++++++++++++++++++++ +
 
 error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
-  --> $DIR/field_checks.rs:44:5
+  --> $DIR/field_checks.rs:50:5
    |
 LL |     nest: U5,
    |     ^^^^^^^^
@@ -47,7 +47,7 @@ LL |     nest: std::mem::ManuallyDrop<U5>,
    |           +++++++++++++++++++++++  +
 
 error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
-  --> $DIR/field_checks.rs:48:5
+  --> $DIR/field_checks.rs:54:5
    |
 LL |     nest: [U5; 0],
    |     ^^^^^^^^^^^^^
diff --git a/tests/ui/union/union-backcomp.rs b/tests/ui/union/union-backcomp.rs
index a71813968e841..46b5eb48f0c4a 100644
--- a/tests/ui/union/union-backcomp.rs
+++ b/tests/ui/union/union-backcomp.rs
@@ -1,4 +1,5 @@
 //@ run-pass
+//@ reference: lex.keywords.weak.union
 
 #![allow(path_statements)]
 #![allow(dead_code)]
diff --git a/tests/ui/union/union-copy.rs b/tests/ui/union/union-copy.rs
index 7ad0a11c6ac6e..40b43b8f3466e 100644
--- a/tests/ui/union/union-copy.rs
+++ b/tests/ui/union/union-copy.rs
@@ -1,3 +1,4 @@
+//@ reference: lang-types.copy.constraint
 #[derive(Clone)]
 union U {
     a: u8
diff --git a/tests/ui/union/union-copy.stderr b/tests/ui/union/union-copy.stderr
index bd63908b49a2c..60cb49147b659 100644
--- a/tests/ui/union/union-copy.stderr
+++ b/tests/ui/union/union-copy.stderr
@@ -1,5 +1,5 @@
 error[E0204]: the trait `Copy` cannot be implemented for this type
-  --> $DIR/union-copy.rs:12:15
+  --> $DIR/union-copy.rs:13:15
    |
 LL |     a: std::mem::ManuallyDrop<String>
    |     --------------------------------- this field does not implement `Copy`
@@ -8,7 +8,7 @@ LL | impl Copy for W {}
    |               ^
    |
 note: the `Copy` impl for `ManuallyDrop<String>` requires that `String: Copy`
-  --> $DIR/union-copy.rs:8:8
+  --> $DIR/union-copy.rs:9:8
    |
 LL |     a: std::mem::ManuallyDrop<String>
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/union/union-drop.rs b/tests/ui/union/union-drop.rs
index 6f6d5c1416534..a29de4f69a9bf 100644
--- a/tests/ui/union/union-drop.rs
+++ b/tests/ui/union/union-drop.rs
@@ -1,4 +1,5 @@
 //@ run-pass
+//@ reference: items.union.drop
 
 #![allow(dead_code)]
 #![allow(unused_variables)]
diff --git a/tests/ui/union/union-empty.rs b/tests/ui/union/union-empty.rs
index 79b7e68ee6beb..60b6668b6e245 100644
--- a/tests/ui/union/union-empty.rs
+++ b/tests/ui/union/union-empty.rs
@@ -1,3 +1,4 @@
+//@ reference: items.union.fieldless
 union U {} //~ ERROR unions cannot have zero fields
 
 fn main() {}
diff --git a/tests/ui/union/union-empty.stderr b/tests/ui/union/union-empty.stderr
index 03a939769c78b..aeec4eca5a996 100644
--- a/tests/ui/union/union-empty.stderr
+++ b/tests/ui/union/union-empty.stderr
@@ -1,5 +1,5 @@
 error: unions cannot have zero fields
-  --> $DIR/union-empty.rs:1:1
+  --> $DIR/union-empty.rs:2:1
    |
 LL | union U {}
    | ^^^^^^^^^^
diff --git a/tests/ui/union/union-fields-2.rs b/tests/ui/union/union-fields-2.rs
index 71b204fcdc5b8..981fbff63ebda 100644
--- a/tests/ui/union/union-fields-2.rs
+++ b/tests/ui/union/union-fields-2.rs
@@ -1,3 +1,4 @@
+//@ reference: items.union.init.intro
 union U {
     a: u8,
     b: u16,
diff --git a/tests/ui/union/union-fields-2.stderr b/tests/ui/union/union-fields-2.stderr
index 142186885caa8..4a39f5ec36c50 100644
--- a/tests/ui/union/union-fields-2.stderr
+++ b/tests/ui/union/union-fields-2.stderr
@@ -1,17 +1,17 @@
 error[E0784]: union expressions should have exactly one field
-  --> $DIR/union-fields-2.rs:7:13
+  --> $DIR/union-fields-2.rs:8:13
    |
 LL |     let u = U {};
    |             ^
 
 error[E0784]: union expressions should have exactly one field
-  --> $DIR/union-fields-2.rs:9:13
+  --> $DIR/union-fields-2.rs:10:13
    |
 LL |     let u = U { a: 0, b: 1 };
    |             ^
 
 error[E0560]: union `U` has no field named `c`
-  --> $DIR/union-fields-2.rs:10:29
+  --> $DIR/union-fields-2.rs:11:29
    |
 LL |     let u = U { a: 0, b: 1, c: 2 };
    |                             ^ `U` does not have this field
@@ -19,61 +19,61 @@ LL |     let u = U { a: 0, b: 1, c: 2 };
    = note: all struct fields are already assigned
 
 error[E0784]: union expressions should have exactly one field
-  --> $DIR/union-fields-2.rs:10:13
+  --> $DIR/union-fields-2.rs:11:13
    |
 LL |     let u = U { a: 0, b: 1, c: 2 };
    |             ^
 
 error[E0784]: union expressions should have exactly one field
-  --> $DIR/union-fields-2.rs:12:13
+  --> $DIR/union-fields-2.rs:13:13
    |
 LL |     let u = U { ..u };
    |             ^
 
 error[E0436]: functional record update syntax requires a struct
-  --> $DIR/union-fields-2.rs:12:19
+  --> $DIR/union-fields-2.rs:13:19
    |
 LL |     let u = U { ..u };
    |                   ^
 
 error: union patterns should have exactly one field
-  --> $DIR/union-fields-2.rs:15:9
+  --> $DIR/union-fields-2.rs:16:9
    |
 LL |     let U {} = u;
    |         ^^^^
 
 error: union patterns should have exactly one field
-  --> $DIR/union-fields-2.rs:17:9
+  --> $DIR/union-fields-2.rs:18:9
    |
 LL |     let U { a, b } = u;
    |         ^^^^^^^^^^
 
 error: union patterns should have exactly one field
-  --> $DIR/union-fields-2.rs:18:9
+  --> $DIR/union-fields-2.rs:19:9
    |
 LL |     let U { a, b, c } = u;
    |         ^^^^^^^^^^^^^
 
 error[E0026]: union `U` does not have a field named `c`
-  --> $DIR/union-fields-2.rs:18:19
+  --> $DIR/union-fields-2.rs:19:19
    |
 LL |     let U { a, b, c } = u;
    |                   ^ union `U` does not have this field
 
 error: union patterns should have exactly one field
-  --> $DIR/union-fields-2.rs:20:9
+  --> $DIR/union-fields-2.rs:21:9
    |
 LL |     let U { .. } = u;
    |         ^^^^^^^^
 
 error: `..` cannot be used in union patterns
-  --> $DIR/union-fields-2.rs:20:9
+  --> $DIR/union-fields-2.rs:21:9
    |
 LL |     let U { .. } = u;
    |         ^^^^^^^^
 
 error: `..` cannot be used in union patterns
-  --> $DIR/union-fields-2.rs:22:9
+  --> $DIR/union-fields-2.rs:23:9
    |
 LL |     let U { a, .. } = u;
    |         ^^^^^^^^^^^
diff --git a/tests/ui/union/union-overwrite.rs b/tests/ui/union/union-overwrite.rs
index cd9a370ff6663..a49d0b5dfe8c8 100644
--- a/tests/ui/union/union-overwrite.rs
+++ b/tests/ui/union/union-overwrite.rs
@@ -1,4 +1,7 @@
 //@ run-pass
+//@ reference: items.union.common-storage
+//@ reference: items.union.fields.read
+//@ reference: type.union.constraint
 
 #[repr(C)]
 #[derive(Copy, Clone)]
diff --git a/tests/ui/union/union-pat-refutability.rs b/tests/ui/union/union-pat-refutability.rs
index 826bd42cd2113..c0d24379c4966 100644
--- a/tests/ui/union/union-pat-refutability.rs
+++ b/tests/ui/union/union-pat-refutability.rs
@@ -1,4 +1,8 @@
 //@ run-pass
+//@ reference: items.union.pattern
+//@ reference: items.union.pattern.intro
+//@ reference: items.union.pattern.safety
+//@ reference: items.union.pattern.subpattern
 
 #![allow(dead_code)]
 
diff --git a/tests/ui/union/union-unsafe.rs b/tests/ui/union/union-unsafe.rs
index beb074f4e8ebc..085031f24e87e 100644
--- a/tests/ui/union/union-unsafe.rs
+++ b/tests/ui/union/union-unsafe.rs
@@ -1,3 +1,6 @@
+//@ reference: items.union.fields.read-safety
+//@ reference: safety.unsafe-union-access
+//@ reference: type.union.safety
 use std::cell::RefCell;
 use std::mem::ManuallyDrop;
 use std::ops::Deref;
diff --git a/tests/ui/union/union-unsafe.stderr b/tests/ui/union/union-unsafe.stderr
index 01f4d95eb649d..6fa01992f5451 100644
--- a/tests/ui/union/union-unsafe.stderr
+++ b/tests/ui/union/union-unsafe.stderr
@@ -1,5 +1,5 @@
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:36:6
+  --> $DIR/union-unsafe.rs:39:6
    |
 LL |     *(u.p) = 13;
    |      ^^^^^ access to union field
@@ -7,7 +7,7 @@ LL |     *(u.p) = 13;
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:50:26
+  --> $DIR/union-unsafe.rs:53:26
    |
 LL |     let _p = &raw const *(u.p);
    |                          ^^^^^ access to union field
@@ -15,7 +15,7 @@ LL |     let _p = &raw const *(u.p);
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:62:6
+  --> $DIR/union-unsafe.rs:65:6
    |
 LL |     *u3.a = T::default();
    |      ^^^^ access to union field
@@ -23,7 +23,7 @@ LL |     *u3.a = T::default();
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:68:6
+  --> $DIR/union-unsafe.rs:71:6
    |
 LL |     *u3.a = T::default();
    |      ^^^^ access to union field
@@ -31,7 +31,7 @@ LL |     *u3.a = T::default();
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:76:13
+  --> $DIR/union-unsafe.rs:79:13
    |
 LL |     let a = u1.a;
    |             ^^^^ access to union field
@@ -39,7 +39,7 @@ LL |     let a = u1.a;
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:91:29
+  --> $DIR/union-unsafe.rs:94:29
    |
 LL |     let _a = &raw const vec[u4.a];
    |                             ^^^^ access to union field
@@ -47,7 +47,7 @@ LL |     let _a = &raw const vec[u4.a];
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:93:14
+  --> $DIR/union-unsafe.rs:96:14
    |
 LL |     let U1 { a } = u1;
    |              ^ access to union field
@@ -55,7 +55,7 @@ LL |     let U1 { a } = u1;
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:94:20
+  --> $DIR/union-unsafe.rs:97:20
    |
 LL |     if let U1 { a: 12 } = u1 {}
    |                    ^^ access to union field
@@ -63,7 +63,7 @@ LL |     if let U1 { a: 12 } = u1 {}
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:95:25
+  --> $DIR/union-unsafe.rs:98:25
    |
 LL |     if let Some(U1 { a: 13 }) = Some(u1) {}
    |                         ^^ access to union field
@@ -71,7 +71,7 @@ LL |     if let Some(U1 { a: 13 }) = Some(u1) {}
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:100:6
+  --> $DIR/union-unsafe.rs:103:6
    |
 LL |     *u2.a = String::from("new");
    |      ^^^^ access to union field
@@ -79,7 +79,7 @@ LL |     *u2.a = String::from("new");
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:104:6
+  --> $DIR/union-unsafe.rs:107:6
    |
 LL |     *u3.a = 1;
    |      ^^^^ access to union field
@@ -87,7 +87,7 @@ LL |     *u3.a = 1;
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:108:6
+  --> $DIR/union-unsafe.rs:111:6
    |
 LL |     *u3.a = String::from("new");
    |      ^^^^ access to union field
@@ -95,7 +95,7 @@ LL |     *u3.a = String::from("new");
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:117:28
+  --> $DIR/union-unsafe.rs:120:28
    |
 LL |     let _p = &raw const (**a.b).c;
    |                            ^^^ access to union field
@@ -103,7 +103,7 @@ LL |     let _p = &raw const (**a.b).c;
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0133]: access to union field is unsafe and requires unsafe function or block
-  --> $DIR/union-unsafe.rs:148:27
+  --> $DIR/union-unsafe.rs:151:27
    |
 LL |     let _p = &raw const (*a.b).c;
    |                           ^^^ access to union field