diff --git a/tests/ui/for-loop-while/iter-from-mac-call.rs b/tests/ui/for-loop-while/iter-from-mac-call.rs
index 8df21456222c..58177444c3f9 100644
--- a/tests/ui/for-loop-while/iter-from-mac-call.rs
+++ b/tests/ui/for-loop-while/iter-from-mac-call.rs
@@ -1,13 +1,12 @@
+//! Tests for trait/type errors when dereferencing via macro in a for loop.
+
 macro_rules! deref {
-    ($e:expr) => { *$e };
+    ($e:expr) => {
+        *$e
+    };
 }
 
-fn f1<'a>(mut iter: Box<dyn Iterator<Item=&'a mut u8>>) {
-    for item in deref!(iter) { *item = 0 }
-    //~^ ERROR `dyn Iterator<Item = &'a mut u8>` is not an iterator
-}
-
-fn f2(x: &mut i32) {
+fn f1(x: &mut i32) {
     for _item in deref!(x) {}
     //~^ ERROR `i32` is not an iterator
 }
@@ -15,12 +14,16 @@ fn f2(x: &mut i32) {
 struct Wrapped(i32);
 
 macro_rules! borrow_deref {
-    ($e:expr) => { &mut *$e };
+    ($e:expr) => {
+        &mut *$e
+    };
 }
 
-fn f3<'a>(mut iter: Box<dyn Iterator<Item=&'a mut i32>>) {
-    for Wrapped(item) in borrow_deref!(iter) { *item = 0 }
-    //~^ ERROR mismatched types
+fn f2<'a>(mut iter: Box<dyn Iterator<Item = &'a mut i32>>) {
+    for Wrapped(item) in borrow_deref!(iter) {
+        //~^ ERROR mismatched types
+        *item = 0
+    }
 }
 
 fn main() {}
diff --git a/tests/ui/for-loop-while/iter-from-mac-call.stderr b/tests/ui/for-loop-while/iter-from-mac-call.stderr
index e62efb250e29..4cde6a8a86d3 100644
--- a/tests/ui/for-loop-while/iter-from-mac-call.stderr
+++ b/tests/ui/for-loop-while/iter-from-mac-call.stderr
@@ -1,18 +1,5 @@
-error[E0277]: `dyn Iterator<Item = &'a mut u8>` is not an iterator
-  --> $DIR/iter_from_mac_call.rs:6:17
-   |
-LL |     for item in deref!(iter) { *item = 0 }
-   |                 ^^^^^^^^^^^^ the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &'a mut u8>`
-   |
-   = note: the trait bound `dyn Iterator<Item = &'a mut u8>: IntoIterator` is not satisfied
-   = note: required for `dyn Iterator<Item = &'a mut u8>` to implement `IntoIterator`
-help: consider mutably borrowing here
-   |
-LL |     for item in &mut deref!(iter) { *item = 0 }
-   |                 ++++
-
 error[E0277]: `i32` is not an iterator
-  --> $DIR/iter_from_mac_call.rs:11:18
+  --> $DIR/iter-from-mac-call.rs:10:18
    |
 LL |     for _item in deref!(x) {}
    |                  ^^^^^^^^^ `i32` is not an iterator
@@ -22,14 +9,14 @@ LL |     for _item in deref!(x) {}
    = note: required for `i32` to implement `IntoIterator`
 
 error[E0308]: mismatched types
-  --> $DIR/iter_from_mac_call.rs:22:9
+  --> $DIR/iter-from-mac-call.rs:23:9
    |
-LL |     for Wrapped(item) in borrow_deref!(iter) { *item = 0 }
+LL |     for Wrapped(item) in borrow_deref!(iter) {
    |         ^^^^^^^^^^^^^    ------------------- this is an iterator with items of type `&mut i32`
    |         |
    |         expected `i32`, found `Wrapped`
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0277, E0308.
 For more information about an error, try `rustc --explain E0277`.
diff --git a/tests/ui/traits/dyn-iterator-deref-in-for-loop.current.stderr b/tests/ui/traits/dyn-iterator-deref-in-for-loop.current.stderr
index 1a66cb414649..b5a9b82a93a3 100644
--- a/tests/ui/traits/dyn-iterator-deref-in-for-loop.current.stderr
+++ b/tests/ui/traits/dyn-iterator-deref-in-for-loop.current.stderr
@@ -1,14 +1,14 @@
 error[E0277]: `dyn Iterator<Item = &'a mut u8>` is not an iterator
-  --> $DIR/issue-20605.rs:6:17
+  --> $DIR/dyn-iterator-deref-in-for-loop.rs:9:17
    |
-LL |     for item in *things { *item = 0 }
+LL |     for item in *things {
    |                 ^^^^^^^ the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &'a mut u8>`
    |
    = note: the trait bound `dyn Iterator<Item = &'a mut u8>: IntoIterator` is not satisfied
    = note: required for `dyn Iterator<Item = &'a mut u8>` to implement `IntoIterator`
 help: consider mutably borrowing here
    |
-LL |     for item in &mut *things { *item = 0 }
+LL |     for item in &mut *things {
    |                 ++++
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/traits/dyn-iterator-deref-in-for-loop.next.stderr b/tests/ui/traits/dyn-iterator-deref-in-for-loop.next.stderr
index 1a66cb414649..b5a9b82a93a3 100644
--- a/tests/ui/traits/dyn-iterator-deref-in-for-loop.next.stderr
+++ b/tests/ui/traits/dyn-iterator-deref-in-for-loop.next.stderr
@@ -1,14 +1,14 @@
 error[E0277]: `dyn Iterator<Item = &'a mut u8>` is not an iterator
-  --> $DIR/issue-20605.rs:6:17
+  --> $DIR/dyn-iterator-deref-in-for-loop.rs:9:17
    |
-LL |     for item in *things { *item = 0 }
+LL |     for item in *things {
    |                 ^^^^^^^ the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &'a mut u8>`
    |
    = note: the trait bound `dyn Iterator<Item = &'a mut u8>: IntoIterator` is not satisfied
    = note: required for `dyn Iterator<Item = &'a mut u8>` to implement `IntoIterator`
 help: consider mutably borrowing here
    |
-LL |     for item in &mut *things { *item = 0 }
+LL |     for item in &mut *things {
    |                 ++++
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/traits/dyn-iterator-deref-in-for-loop.rs b/tests/ui/traits/dyn-iterator-deref-in-for-loop.rs
index 5c56e64a0172..04587df1555d 100644
--- a/tests/ui/traits/dyn-iterator-deref-in-for-loop.rs
+++ b/tests/ui/traits/dyn-iterator-deref-in-for-loop.rs
@@ -1,10 +1,15 @@
+//! Tests that dereferencing a Box<dyn Iterator> in a for loop correctly yields an error,
+//! as the unsized trait object does not implement IntoIterator.
+//! regression test for <https://github.com/rust-lang/rust/issues/20605>
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-fn changer<'a>(mut things: Box<dyn Iterator<Item=&'a mut u8>>) {
-    for item in *things { *item = 0 }
-    //~^ ERROR `dyn Iterator<Item = &'a mut u8>` is not an iterator
+fn changer<'a>(mut things: Box<dyn Iterator<Item = &'a mut u8>>) {
+    for item in *things {
+        //~^ ERROR `dyn Iterator<Item = &'a mut u8>` is not an iterator
+        *item = 0
+    }
 }
 
 fn main() {}