Calls to std::format and std::vformat can receive either format strings whose replacement fields are fully indexed or
fully non-indexed.
Explicitly indexing replacement fields is useful when arguments are not used in order or are used multiple times. Implicit indexing has the
advantage of being terse and simple.
Using explicit indexing in a context where implicit indexing would have the same behavior is more verbose and error-prone. It might confuse the
reader, who might expect the arguments not to be used in order.
This rule raises an issue on explicit indexing that should be replaced by implicit indexing.
Noncompliant code example
std::string printRectangle(Rectangle const& r) {
return std::format("[{0},{1}]:({2},{3})", r.x, r.y, r.width, r.height); // Noncompliant
}
Compliant solution
std::string printRectangle(Rectangle const& r) {
return std::format("[{},{}]:({},{})", r.x, r.y, r.width, r.height); // Compliant
}
Exceptions
Format strings with nested replacement fields are not considered by this rule as their order is less intuitive.
std::string printNDigits() {
return std::format("{0:*<{1}} {2:*>{3}}", 10, 2, 11, 3); // Compliant
}
