assert(format!"%-5,1g"(0.0) == "0    ");

Instead it throws:

core.exception.RangeError@/usr/include/dmd/phobos/std/format/internal/write.d(656): Range violation
----------------
??:? _d_arrayboundsp [0x563fc0971eed]
??:? @safe void std.format.internal.write.formatValueImpl!(std.stdio.File.LockingTextWriter, double, char).formatValueImpl(ref std.stdio.File.LockingTextWriter, double, scope ref const(std.format.spec.FormatSpec!(char).FormatSpec)) [0x563fc09678a8]
??:? @safe void std.format.write.formatValue!(std.stdio.File.LockingTextWriter, double, char).formatValue(ref std.stdio.File.LockingTextWriter, ref double, scope ref const(std.format.spec.FormatSpec!(char).FormatSpec)) [0x563fc0967107]
??:? @safe uint std.format.write.formattedWrite!(std.stdio.File.LockingTextWriter, char, double).formattedWrite(ref std.stdio.File.LockingTextWriter, scope const(char[]), double) [0x563fc0966270]
??:? @safe void std.stdio.File.writefln!(char, double).writefln(in char[], double) [0x563fc0965ef2]
??:? @safe void std.stdio.writefln!(char, double).writefln(in char[], double) [0x563fc0965e7a]
??:? @safe void std.stdio.writefln!("%-5,1g", double).writefln(double) [0x563fc09523cf]
??:? _Dmain [0x563fc0951b8f]