clippy: fix clippy::manual_assert lint

https://rust-lang.github.io/rust-clippy/master/index.html#manual_assert

Closes #12341

Cargo.toml

@@ -198,6 +198,7 @@ format_push_string = "warn"
 implicit_clone = "warn"
 len_without_is_empty = "allow"    # we're not a library crate
 let_and_return = "allow"
+manual_assert = "warn"
 manual_range_contains = "allow"
 map_unwrap_or = "warn"
 mut_mut = "warn"

crates/build-man-pages/build.rs

@@ -75,12 +75,12 @@ macro_rules! as_os_strs {
         .spawn()
     {
         Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
-            if env_var("FISH_BUILD_DOCS") == Some("1".to_string()) {
-                panic!(
-                    "Could not find sphinx-build required to build man pages.\n\
-                     Install Sphinx or disable building the docs by setting $FISH_BUILD_DOCS=0."
-                );
-            }
+            assert_ne!(
+                env_var("FISH_BUILD_DOCS"),
+                Some("1".to_string()),
+                "Could not find sphinx-build required to build man pages.\n\
+                 Install Sphinx or disable building the docs by setting $FISH_BUILD_DOCS=0."
+            );
             rsconf::warn!(
                 "Could not find sphinx-build required to build man pages. \
                  If you install Sphinx now, you need to trigger a rebuild to include man pages. \
@@ -107,9 +107,10 @@ macro_rules! as_os_strs {
                 rsconf::warn!("sphinx-build: {}", String::from_utf8_lossy(&out.stderr));
             }
             assert_eq!(&String::from_utf8_lossy(&out.stdout), "");
-            if !out.status.success() {
-                panic!("sphinx-build failed to build the man pages.");
-            }
+            assert!(
+                out.status.success(),
+                "sphinx-build failed to build the man pages."
+            )
         }
     }
 }

crates/gettext-extraction/src/lib.rs

@@ -47,11 +47,10 @@ enum State {
 // unsynchronized writers to the same file.
 fn write_po_entry_to_file(message: &TokenStream, dir: &OsString) {
     let message_string = unescape_multiline_rust_string(message.to_string());
-    if message_string.contains('\n') {
-        panic!(
-            "Gettext strings may not contain unescaped newlines. Unescaped newline found in '{message_string}'"
-        )
-    }
+    assert!(
+        !message_string.contains('\n'),
+        "Gettext strings may not contain unescaped newlines. Unescaped newline found in '{message_string}'"
+    );
     // Crude check for format strings. This might result in false positives.
     let format_string_annotation = if message_string.contains('%') {
         "#, c-format\n"
@@ -90,11 +89,10 @@ pub fn gettext_extract(message: TokenStream) -> TokenStream {
         let first_token = token_trees
             .next()
             .expect("gettext_extract got empty token stream. Expected one token.");
-        if token_trees.next().is_some() {
-            panic!(
-                "Invalid number of tokens passed to gettext_extract. Expected one token, but got more."
-            )
-        }
+        assert!(
+            token_trees.next().is_none(),
+            "Invalid number of tokens passed to gettext_extract. Expected one token, but got more."
+        );
         let proc_macro2::TokenTree::Group(group) = first_token else {
             panic!("Expected group in gettext_extract, but got: {first_token:?}");
         };
@@ -102,11 +100,10 @@ pub fn gettext_extract(message: TokenStream) -> TokenStream {
         let first_group_token = group_tokens
             .next()
             .expect("gettext_extract expected one group token but got none.");
-        if group_tokens.next().is_some() {
-            panic!(
-                "Invalid number of tokens in group passed to gettext_extract. Expected one token, but got more."
-            )
-        }
+        assert!(
+            group_tokens.next().is_none(),
+            "Invalid number of tokens in group passed to gettext_extract. Expected one token, but got more."
+        );
         if let proc_macro2::TokenTree::Literal(_) = first_group_token {
             write_po_entry_to_file(&message, &dir_path);
         } else {

crates/gettext-maps/build.rs

@@ -115,12 +115,11 @@ fn embed_localizations(cache_dir: &Path) {
                     .output()
                     .unwrap()
                 };
-                if !output.status.success() {
-                    panic!(
-                        "msgfmt failed:\n{}",
-                        String::from_utf8(output.stderr).unwrap()
-                    );
-                }
+                assert!(
+                    output.status.success(),
+                    "msgfmt failed:\n{}",
+                    String::from_utf8(output.stderr).unwrap()
+                );
                 let mo_data =
                     tmp_mo_file.map_or(output.stdout, |path| std::fs::read(path).unwrap());
 

src/threads/threads.rs

@@ -508,11 +508,12 @@ struct Context {
                 false
             })
             .unwrap();
-        if timeout.timed_out() {
-            panic!(concat!(
+        assert!(
+            !timeout.timed_out(),
+            concat!(
                 "Timeout waiting for condition variable to be notified! ",
                 "Does the platform support signalling a condvar without the mutex held?"
-            ));
-        }
+            )
+        )
     }
 }