Precision can be provided as a constant in the format string, as a named parameter or a positional parameter. For example there are these 3 possibilities to display pi as 3.142:
let pi = 3.141592;
println!("{:.3}", pi);
println!("{:.precision$}", pi, precision=3);
println!("{:.*}", 3, pi);
But width can only be provided in the first two forms and not as a positional parameter. For example to right-align with a specified width:
let one = 1;
println!("{:>3}", one);
println!("{:>width$}", one, width=3);
// println!("{:>*}", 3, one); // => error: invalid format string: expected `'}'`, found `'*'`
The corresponding third possibility doesn’t compile.
What is the justification of this inconsistency?