repeated-string-growth

Disallow repeatedly rebuilding a growing string in an iteration

Concatenating into storage that survives an iteration repeatedly copies the text accumulated so far.
Instead, you SHOULD append into a StringBuilder and convert it into a string after the iteration.

Counted loops that append one invariant string can append a single repeat result.

- Category: performance
- Level: warning
- Fix: suggestion
- Scope: module

Reported

function indent(depth: isize): string {
    let output = "";
    for (const _ of 0..depth) {
        output += "  ";
    }

    return output;
}
Accepted

function indent(depth: isize): string {
    let output = "";
    output += "  ".repeat(depth > 0 ? depth : 0);

    return output;
}
language/linter/src/rules/performance/repeatedstringgrowth.rs:9