diff --git a/compiler/rustc_mir/src/transform/coverage/debug.rs b/compiler/rustc_mir/src/transform/coverage/debug.rs
index 1347656c23e..af81d9af0e2 100644
--- a/compiler/rustc_mir/src/transform/coverage/debug.rs
+++ b/compiler/rustc_mir/src/transform/coverage/debug.rs
@@ -152,38 +152,42 @@ impl DebugOptions {
                     None => (setting_str, None),
                     Some((k, v)) => (k, Some(v)),
                 };
-                if option == "allow_unused_expressions" {
-                    allow_unused_expressions = bool_option_val(option, value);
-                    debug!(
-                        "{} env option `allow_unused_expressions` is set to {}",
-                        RUSTC_COVERAGE_DEBUG_OPTIONS, allow_unused_expressions
-                    );
-                } else if option == "counter_format" {
-                    match value {
-                        None => {
-                            bug!(
-                                "`{}` option in environment variable {} requires one or more \
-                                plus-separated choices (a non-empty subset of \
-                                `id+block+operation`)",
-                                option,
-                                RUSTC_COVERAGE_DEBUG_OPTIONS
-                            );
-                        }
-                        Some(val) => {
-                            counter_format = counter_format_option_val(val);
-                            debug!(
-                                "{} env option `counter_format` is set to {:?}",
-                                RUSTC_COVERAGE_DEBUG_OPTIONS, counter_format
-                            );
-                        }
-                    };
-                } else {
-                    bug!(
-                        "Unsupported setting `{}` in environment variable {}",
-                        option,
-                        RUSTC_COVERAGE_DEBUG_OPTIONS
-                    )
-                }
+                match option {
+                    "allow_unused_expressions" => {
+                        allow_unused_expressions = bool_option_val(option, value);
+                        debug!(
+                            "{} env option `allow_unused_expressions` is set to {}",
+                            RUSTC_COVERAGE_DEBUG_OPTIONS, allow_unused_expressions
+                        );
+                    }
+                    "counter_format" => {
+                        match value {
+                            None => {
+                                bug!(
+                                    "`{}` option in environment variable {} requires one or more \
+                                    plus-separated choices (a non-empty subset of \
+                                    `id+block+operation`)",
+                                    option,
+                                    RUSTC_COVERAGE_DEBUG_OPTIONS
+                                );
+                            }
+                            Some(val) => {
+                                counter_format = counter_format_option_val(val);
+                                debug!(
+                                    "{} env option `counter_format` is set to {:?}",
+                                    RUSTC_COVERAGE_DEBUG_OPTIONS, counter_format
+                                );
+                            }
+                        };
+                    }
+                    _ => {
+                        bug!(
+                            "Unsupported setting `{}` in environment variable {}",
+                            option,
+                            RUSTC_COVERAGE_DEBUG_OPTIONS
+                        )
+                    }
+                };
             }
         }
 
diff --git a/src/tools/tidy/src/error_codes_check.rs b/src/tools/tidy/src/error_codes_check.rs
index 1c175901be8..a7199fdfce6 100644
--- a/src/tools/tidy/src/error_codes_check.rs
+++ b/src/tools/tidy/src/error_codes_check.rs
@@ -85,10 +85,16 @@ fn extract_error_codes(
     for line in f.lines() {
         let s = line.trim();
         if !reached_no_explanation && s.starts_with('E') && s.contains("include_str!(\"") {
-            let err_code = match s.split_once(':') {
-                None => continue,
-                Some((err_code, _)) => err_code.to_owned(),
-            };
+            let err_code = s
+                .split_once(':')
+                .expect(
+                    format!(
+                        "Expected a line with the format `E0xxx: include_str!(\"..\")`, but got {} without a `:` delimiter",
+                        s,
+                    ).as_str()
+                )
+                .0
+                .to_owned();
             if !error_codes.contains_key(&err_code) {
                 error_codes.insert(err_code.clone(), false);
             }
diff --git a/src/tools/tidy/src/ui_tests.rs b/src/tools/tidy/src/ui_tests.rs
index 4c8c1d58ed7..03f4efea983 100644
--- a/src/tools/tidy/src/ui_tests.rs
+++ b/src/tools/tidy/src/ui_tests.rs
@@ -19,6 +19,9 @@ pub fn check(path: &Path, bad: &mut bool) {
                     //
                     // For now, just make sure that there is a corresponding
                     // `$testname.rs` file.
+                    //
+                    // NB: We do not use file_stem() as some file names have multiple `.`s and we
+                    // must strip all of them.
                     let testname =
                         file_path.file_name().unwrap().to_str().unwrap().split_once('.').unwrap().0;
                     if !file_path.with_file_name(testname).with_extension("rs").exists() {