diff --git a/Cargo.lock b/Cargo.lock
index ce5a23ebc..f42741471 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -67,6 +67,12 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "assert_matches"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b34d609dfbaf33d6889b2b7106d3ca345eacad44200913df5ba02bfd31d2ba9"
+
 [[package]]
 name = "autocfg"
 version = "1.5.0"
@@ -256,6 +262,7 @@ checksum = "645cbb3a84e60b7531617d5ae4e57f7e27308f6445f5abf653209ea76dec8dff"
 name = "fish"
 version = "4.3.3"
 dependencies = [
+ "assert_matches",
  "bitflags",
  "cc",
  "cfg-if",
@@ -376,6 +383,7 @@ version = "0.0.0"
 name = "fish-printf"
 version = "0.2.1"
 dependencies = [
+ "assert_matches",
  "libc",
  "unicode-segmentation",
  "unicode-width",
@@ -413,6 +421,7 @@ dependencies = [
 name = "fish-wgetopt"
 version = "0.0.0"
 dependencies = [
+ "assert_matches",
  "fish-wcstringutil",
  "fish-widestring",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 6190677cf..a8055c746 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,6 +11,7 @@ repository = "https://github.com/fish-shell/fish-shell"
 license = "GPL-2.0-only AND LGPL-2.0-or-later AND MIT AND PSF-2.0"
 
 [workspace.dependencies]
+assert_matches = "1.5.0"
 bitflags = "2.5.0"
 cc = "1.0.94"
 cfg-if = "1.0.3"
@@ -94,6 +95,7 @@ homepage = "https://fishshell.com"
 readme = "README.rst"
 
 [dependencies]
+assert_matches.workspace = true
 bitflags.workspace = true
 cfg-if.workspace = true
 errno.workspace = true
diff --git a/crates/printf/Cargo.toml b/crates/printf/Cargo.toml
index de87ad0bc..966d003cc 100644
--- a/crates/printf/Cargo.toml
+++ b/crates/printf/Cargo.toml
@@ -8,10 +8,11 @@ description = "printf implementation, based on musl"
 license = "MIT"
 
 [dependencies]
+assert_matches.workspace = true
 libc.workspace = true
-widestring = { workspace = true, optional = true }
 unicode-segmentation.workspace = true
 unicode-width.workspace = true
+widestring = { workspace = true, optional = true }
 
 [lints]
 workspace = true
diff --git a/crates/printf/src/arg.rs b/crates/printf/src/arg.rs
index 22dceb242..7064dbb20 100644
--- a/crates/printf/src/arg.rs
+++ b/crates/printf/src/arg.rs
@@ -199,27 +199,28 @@ fn to_arg(self) -> Arg<'a> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use assert_matches::assert_matches;
     #[cfg(feature = "widestring")]
     use widestring::utf32str;
 
     #[test]
     fn test_to_arg() {
-        assert!(matches!("test".to_arg(), Arg::Str("test")));
-        assert!(matches!(String::from("test").to_arg(), Arg::Str(_)));
+        assert_matches!("test".to_arg(), Arg::Str("test"));
+        assert_matches!(String::from("test").to_arg(), Arg::Str(_));
         #[cfg(feature = "widestring")]
-        assert!(matches!(utf32str!("test").to_arg(), Arg::WStr(_)));
+        assert_matches!(utf32str!("test").to_arg(), Arg::WStr(_));
         #[cfg(feature = "widestring")]
-        assert!(matches!(WString::from("test").to_arg(), Arg::WStr(_)));
-        assert!(matches!(42f32.to_arg(), Arg::Float(_)));
-        assert!(matches!(42f64.to_arg(), Arg::Float(_)));
-        assert!(matches!('x'.to_arg(), Arg::UInt(120)));
+        assert_matches!(WString::from("test").to_arg(), Arg::WStr(_));
+        assert_matches!(42f32.to_arg(), Arg::Float(_));
+        assert_matches!(42f64.to_arg(), Arg::Float(_));
+        assert_matches!('x'.to_arg(), Arg::UInt(120));
         let mut usize_val: usize = 0;
-        assert!(matches!((&mut usize_val).to_arg(), Arg::USizeRef(_)));
-        assert!(matches!(42i8.to_arg(), Arg::SInt(42)));
-        assert!(matches!(42i16.to_arg(), Arg::SInt(42)));
-        assert!(matches!(42i32.to_arg(), Arg::SInt(42)));
-        assert!(matches!(42i64.to_arg(), Arg::SInt(42)));
-        assert!(matches!(42isize.to_arg(), Arg::SInt(42)));
+        assert_matches!((&mut usize_val).to_arg(), Arg::USizeRef(_));
+        assert_matches!(42i8.to_arg(), Arg::SInt(42));
+        assert_matches!(42i16.to_arg(), Arg::SInt(42));
+        assert_matches!(42i32.to_arg(), Arg::SInt(42));
+        assert_matches!(42i64.to_arg(), Arg::SInt(42));
+        assert_matches!(42isize.to_arg(), Arg::SInt(42));
 
         assert_eq!((-42i8).to_arg(), Arg::SInt(-42));
         assert_eq!((-42i16).to_arg(), Arg::SInt(-42));
@@ -227,14 +228,14 @@ fn test_to_arg() {
         assert_eq!((-42i64).to_arg(), Arg::SInt(-42));
         assert_eq!((-42isize).to_arg(), Arg::SInt(-42));
 
-        assert!(matches!(42u8.to_arg(), Arg::UInt(42)));
-        assert!(matches!(42u16.to_arg(), Arg::UInt(42)));
-        assert!(matches!(42u32.to_arg(), Arg::UInt(42)));
-        assert!(matches!(42u64.to_arg(), Arg::UInt(42)));
-        assert!(matches!(42usize.to_arg(), Arg::UInt(42)));
+        assert_matches!(42u8.to_arg(), Arg::UInt(42));
+        assert_matches!(42u16.to_arg(), Arg::UInt(42));
+        assert_matches!(42u32.to_arg(), Arg::UInt(42));
+        assert_matches!(42u64.to_arg(), Arg::UInt(42));
+        assert_matches!(42usize.to_arg(), Arg::UInt(42));
 
         let ptr = std::ptr::from_ref(&42f32);
-        assert!(matches!(ptr.to_arg(), Arg::UInt(_)));
+        assert_matches!(ptr.to_arg(), Arg::UInt(_));
     }
 
     #[test]
diff --git a/crates/printf/src/fmt_fp/mod.rs b/crates/printf/src/fmt_fp/mod.rs
index d1efa9172..fb0d1a3b3 100644
--- a/crates/printf/src/fmt_fp/mod.rs
+++ b/crates/printf/src/fmt_fp/mod.rs
@@ -4,6 +4,7 @@
 
 use super::locale::Locale;
 use super::printf_impl::{ConversionSpec, Error, ModifierFlags, pad};
+use assert_matches::debug_assert_matches;
 use decimal::{DIGIT_WIDTH, Decimal, DigitLimit};
 use std::cmp::min;
 use std::fmt::Write;
@@ -129,10 +130,10 @@ pub(crate) fn format_float(
 ) -> Result<usize, Error> {
     // Only float conversions are expected.
     type CS = ConversionSpec;
-    debug_assert!(matches!(
+    debug_assert_matches!(
         conv_spec,
         CS::e | CS::E | CS::f | CS::F | CS::g | CS::G | CS::a | CS::A
-    ));
+    );
     let prefix = match (y.is_sign_negative(), flags.mark_pos, flags.pad_pos) {
         (true, _, _) => "-",
         (false, true, _) => "+",
diff --git a/crates/printf/src/printf_impl.rs b/crates/printf/src/printf_impl.rs
index a7f39d83a..510e8c7d7 100644
--- a/crates/printf/src/printf_impl.rs
+++ b/crates/printf/src/printf_impl.rs
@@ -2,6 +2,7 @@
 use super::arg::Arg;
 use super::fmt_fp::format_float;
 use super::locale::Locale;
+use assert_matches::assert_matches;
 use std::fmt::{self, Write};
 use std::mem;
 use std::result::Result;
@@ -301,7 +302,7 @@ pub(super) fn pad(
     min_width: usize,
     current_width: usize,
 ) -> fmt::Result {
-    assert!(c == '0' || c == ' ');
+    assert_matches!(c, '0' | ' ');
     if current_width >= min_width {
         return Ok(());
     }
diff --git a/crates/wgetopt/Cargo.toml b/crates/wgetopt/Cargo.toml
index aff82797d..e03089a6b 100644
--- a/crates/wgetopt/Cargo.toml
+++ b/crates/wgetopt/Cargo.toml
@@ -7,6 +7,7 @@ repository.workspace = true
 license.workspace = true
 
 [dependencies]
+assert_matches.workspace = true
 fish-wcstringutil.workspace = true
 fish-widestring.workspace = true
 
diff --git a/crates/wgetopt/src/lib.rs b/crates/wgetopt/src/lib.rs
index 61b36a7d2..d2b1a1c59 100644
--- a/crates/wgetopt/src/lib.rs
+++ b/crates/wgetopt/src/lib.rs
@@ -24,6 +24,7 @@
 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
 Cambridge, MA 02139, USA.  */
 
+use assert_matches::assert_matches;
 use fish_widestring::prelude::*;
 
 /// Special char used with [`Ordering::ReturnInOrder`].
@@ -397,7 +398,7 @@ fn update_long_opt(
         option_index: usize,
     ) -> char {
         self.wopt_index += 1;
-        assert!(matches!(self.remaining_text.char_at(name_end), '\0' | '='));
+        assert_matches!(self.remaining_text.char_at(name_end), '\0' | '=');
 
         if self.remaining_text.char_at(name_end) == '=' {
             if opt_found.arg_type == ArgType::NoArgument {
diff --git a/src/ast.rs b/src/ast.rs
index 7d7fde1ee..31da44a7c 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -263,7 +263,7 @@ trait NodeMut: Node + AcceptorMut {}
 impl<T> NodeMut for T where T: Node + AcceptorMut {}
 
 /// The different kinds of nodes. Note that Token and Keyword have different subtypes.
-#[derive(Copy, Clone)]
+#[derive(Debug, Copy, Clone)]
 pub enum Kind<'a> {
     Redirection(&'a Redirection),
     Token(&'a dyn Token),
diff --git a/src/autoload.rs b/src/autoload.rs
index f12471733..dd8452160 100644
--- a/src/autoload.rs
+++ b/src/autoload.rs
@@ -51,11 +51,13 @@ enum AssetDir {
     Completions,
 }
 
+#[derive(Debug)]
 pub enum AutoloadPath {
     Embedded(String),
     Path(WString),
 }
 
+#[derive(Debug)]
 pub enum AutoloadResult {
     Path(AutoloadPath),
     Loaded,
@@ -455,6 +457,7 @@ mod tests {
     use super::{Autoload, AutoloadResult};
     use crate::prelude::*;
     use crate::tests::prelude::*;
+    use assert_matches::assert_matches;
 
     #[test]
     #[serial]
@@ -505,39 +508,39 @@ fn touch_file(path: &wstr) {
         autoload.invalidate_cache();
 
         assert!(!autoload.autoload_in_progress(L!("file1")));
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file1"), paths),
             AutoloadResult::Path(_)
-        ));
-        assert!(matches!(
+        );
+        assert_matches!(
             autoload.resolve_command_impl(L!("file1"), paths),
             AutoloadResult::Pending
-        ));
+        );
         assert!(autoload.autoload_in_progress(L!("file1")));
         assert_eq!(autoload.get_autoloaded_commands(), vec![L!("file1")]);
         autoload.mark_autoload_finished(L!("file1"));
         assert!(!autoload.autoload_in_progress(L!("file1")));
         assert_eq!(autoload.get_autoloaded_commands(), vec![L!("file1")]);
 
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file1"), paths),
             AutoloadResult::Loaded
-        ));
+        );
         assert!(
             autoload
                 .resolve_command_impl(L!("nothing"), paths)
                 .is_none()
         );
         assert!(autoload.resolve_command_impl(L!("file2"), paths).is_some());
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file2"), paths),
             AutoloadResult::Pending
-        ));
+        );
         autoload.mark_autoload_finished(L!("file2"));
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file2"), paths),
             AutoloadResult::Loaded
-        ));
+        );
         assert_eq!(
             autoload.get_autoloaded_commands(),
             vec![L!("file1"), L!("file2")]
@@ -546,26 +549,26 @@ fn touch_file(path: &wstr) {
         autoload.clear();
         assert!(autoload.resolve_command_impl(L!("file1"), paths).is_some());
         autoload.mark_autoload_finished(L!("file1"));
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file1"), paths),
             AutoloadResult::Loaded
-        ));
+        );
         assert!(
             autoload
                 .resolve_command_impl(L!("nothing"), paths)
                 .is_none()
         );
         assert!(autoload.resolve_command_impl(L!("file2"), paths).is_some());
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file2"), paths),
             AutoloadResult::Pending
-        ));
+        );
         autoload.mark_autoload_finished(L!("file2"));
 
-        assert!(matches!(
+        assert_matches!(
             autoload.resolve_command_impl(L!("file1"), paths),
             AutoloadResult::Loaded
-        ));
+        );
         touch_file(&sprintf!("%s/file1.fish", p1));
         autoload.invalidate_cache();
         assert!(autoload.resolve_command_impl(L!("file1"), paths).is_some());
diff --git a/src/builtins/fish_indent.rs b/src/builtins/fish_indent.rs
index 0c0ea4791..05d670b5b 100644
--- a/src/builtins/fish_indent.rs
+++ b/src/builtins/fish_indent.rs
@@ -30,6 +30,7 @@
 use crate::tokenizer::{TOK_SHOW_BLANK_LINES, TOK_SHOW_COMMENTS, TokenType, Tokenizer};
 use crate::topic_monitor::topic_monitor_init;
 use crate::wutil::fish_iswalnum;
+use assert_matches::assert_matches;
 use fish_wcstringutil::count_preceding_backslashes;
 use fish_wgetopt::{ArgType, WGetopter, WOption, wopt};
 use std::fmt::Write as _;
@@ -394,7 +395,7 @@ fn gap_text_flags_before_node(&self, node: &dyn Node) -> GapFlags {
                             return result;
                         }
                         let p = self.traversal.parent(p);
-                        assert!(matches!(p.kind(), Kind::Statement(_)));
+                        assert_matches!(p.kind(), Kind::Statement(_));
                         let p = self.traversal.parent(p);
                         if let Kind::JobPipeline(job) = p.kind() {
                             if !job.variables.is_empty() {
diff --git a/src/complete.rs b/src/complete.rs
index 23da9f7a1..99cd27a5c 100644
--- a/src/complete.rs
+++ b/src/complete.rs
@@ -45,6 +45,7 @@
     localization::{LocalizableString, localizable_string},
     reader::{get_quote, is_backslashed},
 };
+use assert_matches::assert_matches;
 use bitflags::bitflags;
 use fish_util::wcsfilecmp;
 use fish_wcstringutil::{
@@ -720,7 +721,7 @@ fn perform_for_commandline_impl(&mut self, cmdline: WString) {
         }
         for tok in &tokens {
             // If there was an error, it was in the last token.
-            assert!(matches!(tok.type_, TokenType::String | TokenType::Redirect));
+            assert_matches!(tok.type_, TokenType::String | TokenType::Redirect);
         }
         // If we are completing a variable name or a tilde expansion user name, we do that and
         // return. No need for any other completions.
diff --git a/src/env/var.rs b/src/env/var.rs
index 7f78027c5..3225f8aa3 100644
--- a/src/env/var.rs
+++ b/src/env/var.rs
@@ -323,6 +323,7 @@ mod tests {
     use crate::env::environment::{EnvStack, Environment};
     use crate::prelude::*;
     use crate::tests::prelude::*;
+    use assert_matches::assert_matches;
     use std::{
         mem::MaybeUninit,
         time::{SystemTime, UNIX_EPOCH},
@@ -361,7 +362,7 @@ fn test_timezone_env_vars() {
         let first_tstamp = return_timezone_hour(tstamp, L!("UTC-1"));
         let second_tstamp = return_timezone_hour(tstamp, L!("UTC-2"));
         let delta = second_tstamp - first_tstamp;
-        assert!(delta == 1 || delta == -23);
+        assert_matches!(delta, 1 | -23);
     }
 
     // Verify that setting special env vars have the expected effect on the current shell process.
diff --git a/src/fd_monitor.rs b/src/fd_monitor.rs
index f974635a8..94e2b63b4 100644
--- a/src/fd_monitor.rs
+++ b/src/fd_monitor.rs
@@ -473,6 +473,7 @@ mod tests {
     use std::thread;
     use std::time::Duration;
 
+    use assert_matches::assert_matches;
     use errno::errno;
 
     use crate::fd_monitor::{FdEventSignaller, FdMonitor};
@@ -694,8 +695,9 @@ fn test_dup2_during_select_ebadf() {
             Some(read_fd)
         };
         let result = do_something_bad_during_select(dup2_it);
-        assert!(
-            matches!(result, Err(libc::EBADF) | Ok(0 | 1)),
+        assert_matches!(
+            result,
+            Err(libc::EBADF) | Ok(0 | 1),
             "select/poll should have failed with EBADF or timed out or the fd should be ready"
         );
         // Ensure these stay alive until after thread is joined.
diff --git a/src/parser.rs b/src/parser.rs
index abc4f1c7a..71680e7ca 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -35,6 +35,7 @@
 use crate::wait_handle::WaitHandleStore;
 use crate::wutil::perror;
 use crate::{flog, flogf, function};
+use assert_matches::assert_matches;
 use fish_util::get_time;
 use fish_widestring::WExt;
 use libc::c_int;
@@ -568,7 +569,7 @@ pub fn eval_parsed_source(
         block_type: BlockType,
         test_only_suppress_stderr: bool,
     ) -> EvalRes {
-        assert!(matches!(block_type, BlockType::top | BlockType::subst));
+        assert_matches!(block_type, BlockType::top | BlockType::subst);
         let job_list = ps.top_job_list();
         if !job_list.is_empty() {
             // Execute the top job list.
@@ -647,8 +648,9 @@ pub fn eval_node<T: Node>(
         test_only_suppress_stderr: bool,
     ) -> EvalRes {
         // Only certain blocks are allowed.
-        assert!(
-            matches!(block_type, BlockType::top | BlockType::subst),
+        assert_matches!(
+            block_type,
+            BlockType::top | BlockType::subst,
             "Invalid block type"
         );
 
diff --git a/src/reader/reader.rs b/src/reader/reader.rs
index 5ebcdb63a..0fbbaf78f 100644
--- a/src/reader/reader.rs
+++ b/src/reader/reader.rs
@@ -142,6 +142,7 @@
 use crate::wildcard::wildcard_has;
 use crate::wutil::{fstat, perror, write_to_fd, wstat};
 use crate::{abbrs, event, function};
+use assert_matches::assert_matches;
 use fish_fallback::fish_wcwidth;
 use fish_wcstringutil::{
     CaseSensitivity, StringFuzzyMatch, count_preceding_backslashes, join_strings,
@@ -6782,10 +6783,7 @@ fn reader_can_replace(s: &wstr, flags: CompleteFlags) -> bool {
 impl<'a> Reader<'a> {
     /// Compute completions and update the pager and/or commandline as needed.
     fn compute_and_apply_completions(&mut self, c: ReadlineCmd) {
-        assert!(matches!(
-            c,
-            ReadlineCmd::Complete | ReadlineCmd::CompleteAndSearch
-        ));
+        assert_matches!(c, ReadlineCmd::Complete | ReadlineCmd::CompleteAndSearch);
         assert!(
             !get_tty_protocols_active(),
             "should not be called with TTY protocols active"
diff --git a/src/terminal.rs b/src/terminal.rs
index 74533249c..95852e54c 100644
--- a/src/terminal.rs
+++ b/src/terminal.rs
@@ -39,14 +39,14 @@ pub fn set_color_support(val: ColorSupport) {
     COLOR_SUPPORT.store(val.bits(), Ordering::Relaxed);
 }
 
-#[derive(Clone, Copy)]
+#[derive(Debug, Clone, Copy)]
 pub(crate) enum Paintable {
     Foreground,
     Background,
     Underline,
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub(crate) enum TerminalCommand<'a> {
     // Text attributes
     ExitAttributeMode,
@@ -311,7 +311,7 @@ fn rgb_color(out: &mut impl Output, paintable: Paintable, rgb: Color24) -> bool
     true
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub(crate) enum CardinalDirection {
     Up,
     Left,
diff --git a/src/wutil/dir_iter.rs b/src/wutil/dir_iter.rs
index 5ba650c8b..69162b671 100644
--- a/src/wutil/dir_iter.rs
+++ b/src/wutil/dir_iter.rs
@@ -331,6 +331,7 @@ fn next(&mut self) -> Option<Self::Item> {
 mod tests {
     use super::{DirEntryType, DirIter};
     use crate::prelude::*;
+    use assert_matches::assert_matches;
     use fish_widestring::L;
     use nix::sys::stat::Mode;
     use std::fs::File;
@@ -383,7 +384,7 @@ fn test_dir_iter() {
             panic!("Expected error");
         };
         let err = err.raw_os_error().expect("Should have an errno value");
-        assert!(err == ENOENT || err == EACCES);
+        assert_matches!(err, ENOENT | EACCES);
 
         let temp_dir = fish_tempfile::new_dir().unwrap();
         let basepath = WString::from(temp_dir.path().to_str().unwrap());