fix: rm extra indentation and use byte comparison

Author: konippi

library/std/src/panic.rs

@@ -498,26 +498,24 @@ pub fn get_backtrace_style() -> Option<BacktraceStyle> {
         // to optimize away callers.
         return None;
     }
-    BacktraceStyle::from_u8(SHOULD_CAPTURE.load(Ordering::Acquire)).map(Some).unwrap_or_else(|| {
-        let env_var = crate::env::var_os("RUST_BACKTRACE");
-        let style = env_var
-            .and_then(|var| {
-                var.to_str().map(|s| match s {
-                    "0" => BacktraceStyle::Off,
-                    "full" => BacktraceStyle::Full,
-                    _ => BacktraceStyle::Short,
-                })
-            })
-            .unwrap_or_else(|| {
-                if crate::sys::FULL_BACKTRACE_DEFAULT {
-                    BacktraceStyle::Full
-                } else {
-                    BacktraceStyle::Short
-                }
-            });
-        set_backtrace_style(style);
-        Some(style)
-    })
+    if let Some(style) = BacktraceStyle::from_u8(SHOULD_CAPTURE.load(Ordering::Acquire)) {
+        return Some(style);
+    }
+
+    let format = match crate::env::var_os("RUST_BACKTRACE") {
+        Some(x) if &x == "0" => BacktraceStyle::Off,
+        Some(x) if &x == "full" => BacktraceStyle::Full,
+        Some(_) => BacktraceStyle::Short,
+        None => {
+            if crate::sys::FULL_BACKTRACE_DEFAULT {
+                BacktraceStyle::Full
+            } else {
+                BacktraceStyle::Short
+            }
+        }
+    };
+    set_backtrace_style(format);
+    Some(format)
 }
 
 #[cfg(test)]