Struct Argument

pub struct Argument<'a> {
    ty: ArgumentType<'a>,
}

🔬This is a nightly-only experimental API. (fmt_internals)

This struct represents a generic “argument” which is taken by format_args!().

This can be either a placeholder argument or a count argument.

• A placeholder argument contains a function to format the given value. At compile time it is ensured that the function and the value have the correct types, and then this struct is used to canonicalize arguments to one type. Placeholder arguments are essentially an optimized partially applied formatting function, equivalent to exists T.(&T, fn(&T, &mut Formatter<'_>) -> Result.
• A count argument contains a count for dynamic formatting parameters like precision and width.

Fields

ty: ArgumentType<'a>

🔬This is a nightly-only experimental API. (fmt_internals)

Implementations

impl Argument<'_>

pub const fn new_display<T: Display>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_debug<T: Debug>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_debug_noop<T: Debug>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_octal<T: Octal>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_lower_hex<T: LowerHex>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_upper_hex<T: UpperHex>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_pointer<T: Pointer>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_binary<T: Binary>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_lower_exp<T: LowerExp>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn new_upper_exp<T: UpperExp>(x: &T) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn from_usize(x: &usize) -> Argument<'_>

🔬This is a nightly-only experimental API. (fmt_internals)

pub(super) unsafe fn fmt(&self, f: &mut Formatter<'_>) -> Result

🔬This is a nightly-only experimental API. (fmt_internals)

Format this placeholder argument.

Safety

This argument must actually be a placeholder argument.

pub(super) const fn as_u16(&self) -> Option<u16>

🔬This is a nightly-only experimental API. (fmt_internals)

pub const fn none() -> [Self; 0]

🔬This is a nightly-only experimental API. (fmt_internals)

Used by format_args when all arguments are gone after inlining, when using &[] would incorrectly allow for a bigger lifetime.

This fails without format argument inlining, and that shouldn’t be different when the argument is inlined:

let f = format_args!("{}", "a");
println!("{f}");

Trait Implementations

impl<'a> Clone for Argument<'a>

fn clone(&self) -> Argument<'a>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Copy for Argument<'a>