Auto merge of #79927 - tmandry:rollup-pwn4b1v, r=tmandry

Rollup of 11 pull requests

Successful merges:

 - #77027 (Improve documentation for `std::{f32,f64}::mul_add`)
 - #79375 (Make the kernel_copy tests more robust/concurrent.)
 - #79639 (Add long explanation for E0212)
 - #79698 (Add tracking issue template for library features.)
 - #79809 (Dogfood `str_split_once()`)
 - #79851 (Clarify the 'default is only allowed on...' error)
 - #79858 (Update const-fn doc in unstable-book)
 - #79860 (Clarify that String::split_at takes a byte index.)
 - #79871 (Fix small typo in `wrapping_shl` documentation)
 - #79896 (Make search results tab and help button focusable with keyboard)
 - #79917 (Use Symbol for inline asm register class names)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 34 insertions, 28 deletions

diff --git a/compiler/rustc_mir/src/transform/coverage/debug.rs b/compiler/rustc_mir/src/transform/coverage/debug.rs
index e9528557b33..af81d9af0e2 100644
--- a/compiler/rustc_mir/src/transform/coverage/debug.rs
+++ b/compiler/rustc_mir/src/transform/coverage/debug.rs
@@ -148,40 +148,46 @@ impl DebugOptions {
 
         if let Ok(env_debug_options) = std::env::var(RUSTC_COVERAGE_DEBUG_OPTIONS) {
             for setting_str in env_debug_options.replace(" ", "").replace("-", "_").split(',') {
-                let mut setting = setting_str.splitn(2, '=');
-                match setting.next() {
-                    Some(option) if option == "allow_unused_expressions" => {
-                        allow_unused_expressions = bool_option_val(option, setting.next());
+                let (option, value) = match setting_str.split_once('=') {
+                    None => (setting_str, None),
+                    Some((k, v)) => (k, Some(v)),
+                };
+                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
                         );
                     }
-                    Some(option) if option == "counter_format" => {
-                        if let Some(strval) = setting.next() {
-                            counter_format = counter_format_option_val(strval);
-                            debug!(
-                                "{} env option `counter_format` is set to {:?}",
-                                RUSTC_COVERAGE_DEBUG_OPTIONS, counter_format
-                            );
-                        } else {
-                            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
-                            );
-                        }
+                    "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
+                                );
+                            }
+                        };
                     }
-                    Some("") => {}
-                    Some(invalid) => bug!(
-                        "Unsupported setting `{}` in environment variable {}",
-                        invalid,
-                        RUSTC_COVERAGE_DEBUG_OPTIONS
-                    ),
-                    None => {}
-                }
+                    _ => {
+                        bug!(
+                            "Unsupported setting `{}` in environment variable {}",
+                            option,
+                            RUSTC_COVERAGE_DEBUG_OPTIONS
+                        )
+                    }
+                };
             }
         }