From cf7e5581369a6a6dc81f0cd507fd0fcc168e240a Mon Sep 17 00:00:00 2001
From: Owen Colley <169960024+penguinawesome1@users.noreply.github.com>
Date: Sat, 10 Oct 2026 22:26:59 -0400
Subject: [PATCH 1/4] fix: allow single multiline string lit to overflow after
 long ident

---
 src/expr.rs                |  6 +++++
 tests/source/issue_5029.rs | 49 ++++++++++++++++++++++++++++++++++++++
 tests/target/issue_5029.rs | 47 ++++++++++++++++++++++++++++++++++++
 3 files changed, 102 insertions(+)
 create mode 100644 tests/source/issue_5029.rs
 create mode 100644 tests/target/issue_5029.rs

diff --git a/src/expr.rs b/src/expr.rs
index 48f17fb0fd1..3c14fe554d4 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -1593,6 +1593,12 @@ pub(crate) fn can_be_overflowed_expr(
         | ast::ExprKind::While(..) => {
             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
         }
+        ast::ExprKind::Lit(lit) => {
+            context.config.style_edition() >= StyleEdition::Edition2027
+                && args_len == 1
+                && lit.kind == LitKind::Str
+                && lit.symbol.as_str().contains('\n')
+        }
 
         // Handle always block-like expressions
         ast::ExprKind::Gen(..)
diff --git a/tests/source/issue_5029.rs b/tests/source/issue_5029.rs
new file mode 100644
index 00000000000..91159386488
--- /dev/null
+++ b/tests/source/issue_5029.rs
@@ -0,0 +1,49 @@
+// rustfmt-style_edition: 2027
+
+pub const MAC: &str = foo!("
+    foo
+    bar
+");
+
+pub const SHORT_MAC: &str = f!("
+    foo
+    bar
+");
+
+pub const LONG_MAC: &str = long_foo!("
+    foo
+    bar
+");
+
+pub const FUN: &str = foo("
+    foo
+    bar
+");
+
+pub const SHORT_FUN: &str = f("
+    foo
+    bar
+");
+
+pub const LONG_FUN: &str = long_foo("
+    foo
+    bar
+");
+
+pub const BAR: &str = bar!("
+    foo bar
+");
+
+pub const BAZ: &str = baz!(
+    "
+    foo
+    bar
+"
+);
+
+fn main() {
+    let bytes1 = hex!("
+        00010203 04050607
+        08090a0b 0c0d0e0f
+    ");
+}
diff --git a/tests/target/issue_5029.rs b/tests/target/issue_5029.rs
new file mode 100644
index 00000000000..e98ac00e6ab
--- /dev/null
+++ b/tests/target/issue_5029.rs
@@ -0,0 +1,47 @@
+// rustfmt-style_edition: 2027
+
+pub const MAC: &str = foo!("
+    foo
+    bar
+");
+
+pub const SHORT_MAC: &str = f!("
+    foo
+    bar
+");
+
+pub const LONG_MAC: &str = long_foo!("
+    foo
+    bar
+");
+
+pub const FUN: &str = foo("
+    foo
+    bar
+");
+
+pub const SHORT_FUN: &str = f("
+    foo
+    bar
+");
+
+pub const LONG_FUN: &str = long_foo("
+    foo
+    bar
+");
+
+pub const BAR: &str = bar!("
+    foo bar
+");
+
+pub const BAZ: &str = baz!("
+    foo
+    bar
+");
+
+fn main() {
+    let bytes1 = hex!("
+        00010203 04050607
+        08090a0b 0c0d0e0f
+    ");
+}

From 26018dbbff283a5580408c61ba4cff98bf63b504 Mon Sep 17 00:00:00 2001
From: Owen Colley <169960024+penguinawesome1@users.noreply.github.com>
Date: Sat, 17 Oct 2026 10:08:54 -0400
Subject: [PATCH 2/4] test: ensure call with multiline string wraps on max
 width and fn call width

---
 tests/source/issue_5029.rs | 21 +++++++++++++++++++++
 tests/target/issue_5029.rs | 26 ++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/tests/source/issue_5029.rs b/tests/source/issue_5029.rs
index 91159386488..5819b0f4923 100644
--- a/tests/source/issue_5029.rs
+++ b/tests/source/issue_5029.rs
@@ -47,3 +47,24 @@ fn main() {
         08090a0b 0c0d0e0f
     ");
 }
+
+// Default settings: `fn_call_width` is 60. `max_width` is 100.
+// First line string length is 59. Line length is 98.
+pub const ABCDEFGHIJKLMN: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 98.
+pub const ABCDEFGHIJKLM: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+");
+
+// First line string length is 59. Line length is 99.
+pub const ABCDEFGHIJKLMNO: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 99.
+pub const ABCDEFGHIJKLMN: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+");
diff --git a/tests/target/issue_5029.rs b/tests/target/issue_5029.rs
index e98ac00e6ab..ea795634cc7 100644
--- a/tests/target/issue_5029.rs
+++ b/tests/target/issue_5029.rs
@@ -45,3 +45,29 @@ fn main() {
         08090a0b 0c0d0e0f
     ");
 }
+
+// Default settings: `fn_call_width` is 60. `max_width` is 100.
+// First line string length is 59. Line length is 98.
+pub const ABCDEFGHIJKLMN: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 98.
+pub const ABCDEFGHIJKLM: &str = foo!(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+"
+);
+
+// First line string length is 59. Line length is 99.
+pub const ABCDEFGHIJKLMNO: &str =
+    foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 99.
+pub const ABCDEFGHIJKLMN: &str = foo!(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+"
+);

From 0f2d98fb9f3d92a6bed9c6f13be17c13b851465a Mon Sep 17 00:00:00 2001
From: Owen Colley <169960024+penguinawesome1@users.noreply.github.com>
Date: Sat, 17 Oct 2026 10:33:29 -0400
Subject: [PATCH 3/4] chore: update issue_5029 test directives to new //@
 syntax

---
 tests/source/issue_5029.rs | 2 +-
 tests/target/issue_5029.rs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/source/issue_5029.rs b/tests/source/issue_5029.rs
index 5819b0f4923..a81852f8ebd 100644
--- a/tests/source/issue_5029.rs
+++ b/tests/source/issue_5029.rs
@@ -1,4 +1,4 @@
-// rustfmt-style_edition: 2027
+//@ rustfmt-style_edition: 2027
 
 pub const MAC: &str = foo!("
     foo
diff --git a/tests/target/issue_5029.rs b/tests/target/issue_5029.rs
index ea795634cc7..de2a130acd2 100644
--- a/tests/target/issue_5029.rs
+++ b/tests/target/issue_5029.rs
@@ -1,4 +1,4 @@
-// rustfmt-style_edition: 2027
+//@ rustfmt-style_edition: 2027
 
 pub const MAC: &str = foo!("
     foo

From c202318a2ab364a5192898d5af649af8e2c21174 Mon Sep 17 00:00:00 2001
From: Owen Colley <169960024+penguinawesome1@users.noreply.github.com>
Date: Sat, 17 Oct 2026 11:35:39 -0400
Subject: [PATCH 4/4] test: add multiline string cases for function calls

---
 tests/source/issue_5029.rs | 25 +++++++++++++++++++++++++
 tests/target/issue_5029.rs | 30 ++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/tests/source/issue_5029.rs b/tests/source/issue_5029.rs
index a81852f8ebd..966c67d86d4 100644
--- a/tests/source/issue_5029.rs
+++ b/tests/source/issue_5029.rs
@@ -49,6 +49,31 @@ fn main() {
 }
 
 // Default settings: `fn_call_width` is 60. `max_width` is 100.
+
+// functions:
+
+// First line string length is 59. Line length is 98.
+pub const ABCDEFGHIJKLMNO: &str = foo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 98.
+pub const ABCDEFGHIJKLMN: &str = foo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+");
+
+// First line string length is 59. Line length is 99.
+pub const ABCDEFGHIJKLMNOP: &str = foo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 99.
+pub const ABCDEFGHIJKLMNO: &str = foo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+");
+
+// function macros:
+
 // First line string length is 59. Line length is 98.
 pub const ABCDEFGHIJKLMN: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
     next_line
diff --git a/tests/target/issue_5029.rs b/tests/target/issue_5029.rs
index de2a130acd2..35924570971 100644
--- a/tests/target/issue_5029.rs
+++ b/tests/target/issue_5029.rs
@@ -47,6 +47,36 @@ fn main() {
 }
 
 // Default settings: `fn_call_width` is 60. `max_width` is 100.
+
+// functions:
+
+// First line string length is 59. Line length is 98.
+pub const ABCDEFGHIJKLMNO: &str = foo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 98.
+pub const ABCDEFGHIJKLMN: &str = foo(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+",
+);
+
+// First line string length is 59. Line length is 99.
+pub const ABCDEFGHIJKLMNOP: &str =
+    foo("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
+    next_line
+");
+
+// First line string length is 60. Line length is 99.
+pub const ABCDEFGHIJKLMNO: &str = foo(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567
+    next_line
+",
+);
+
+// function macros:
+
 // First line string length is 59. Line length is 98.
 pub const ABCDEFGHIJKLMN: &str = foo!("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456
     next_line