Enum ArgDefault 

pub enum ArgDefault {
    Required,
    None,
    Literal(ArgValue),
    UseSelection,
    UseCursorWord,
    UseLastResponse,
}

What the runtime should fall back to when an arg is unsupplied at invocation time (DESIGN.md §B.1). For interactive entry, the fallback chain is: caller-supplied value -> default -> prompt the user.

What the host acts on today: Required on an ex-command’s first arg arms the cmdline missing-arg prompt when the command is run bare, and Literal fills unset slots when a transient projects its state into Args. The Use* variants are declared and rendered by :describe-command, but nothing resolves them yet – a command that declares one must still cope with the arg being absent.

Variants

Required

No fallback – the runtime prompts (or errors, in non-interactive callers) when this arg is missing.

None

Optional. Missing means “absent”; the apply closure must handle the absence gracefully.

Literal(ArgValue)

A literal default value.

UseSelection

Use the current visual selection’s text. Useful for :s invoked over a visual range: the default pattern is “the selected text”.

UseCursorWord

Use the word under the cursor. Useful for :grep-style commands.

UseLastResponse

Use the most recently entered value of this argument. Useful for :s to default to the previous pattern + replacement.

Trait Implementations

impl Clone for ArgDefault

fn clone(&self) -> ArgDefault

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ArgDefault

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ArgDefault

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for ArgDefault

fn eq(&self, other: &ArgDefault) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for ArgDefault

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ArgDefault