all: prefer else => |e| return e, over else => return err,

When switching on an error, using the captured value instead of the original
one is always preferable since its error set has been narrowed to only
contain errors which haven't already been handled by other switch prongs.

The subsequent commits will disallow this form as an unreachable `else` prong.

lib/std/tar/Writer.zig

@@ -114,7 +114,7 @@ fn writeHeader(
     if (typeflag == .symbolic_link)
         header.setLinkname(link_name) catch |err| switch (err) {
             error.NameTooLong => try w.writeExtendedHeader(.gnu_long_link, &.{link_name}),
-            else => return err,
+            else => |e| return e,
         };
     try header.write(w.underlying_writer);
 }
@@ -131,7 +131,7 @@ fn setPath(w: *Writer, header: *Header, sub_path: []const u8) Error!void {
                 &.{ w.prefix, "/", sub_path };
             try w.writeExtendedHeader(.gnu_long_name, buffers);
         },
-        else => return err,
+        else => |e| return e,
     };
 }
 

lib/std/testing.zig

@@ -1187,7 +1187,7 @@ pub fn checkAllAllocationFailures(backing_allocator: std.mem.Allocator, comptime
                     return error.MemoryLeakDetected;
                 }
             },
-            else => return err,
+            else => |e| return e,
         }
     }
 }