Trait typst::foundations::Reflect

source ·

pub trait Reflect {
    // Required methods
    fn input() -> CastInfo;
    fn output() -> CastInfo;
    fn castable(value: &Value) -> bool;

    // Provided method
    fn error(found: &Value) -> EcoString { ... }
}

Expand description

Determine details of a type.

Type casting works as follows:

Reflect for T describes the possible Typst values for T (for documentation and autocomplete).
IntoValue for T is for conversion from T -> Value (infallible)
FromValue for T is for conversion from Value -> T (fallible).

We can’t use TryFrom<Value> due to conflicting impls. We could use From<T> for Value, but that inverses the impl and leads to tons of .into() all over the place that become hard to decipher.

Required Methods§

source

fn input() -> CastInfo

Describe what can be cast into this value.

source

fn output() -> CastInfo

Describe what this value can be cast into.

source

fn castable(value: &Value) -> bool

Whether the given value can be converted to T.

This exists for performance. The check could also be done through the CastInfo, but it would be much more expensive (heap allocation + dynamic checks instead of optimized machine code for each type).

Provided Methods§

source

fn error(found: &Value) -> EcoString

Produce an error message for an inacceptable value type.

assert_eq!(
  <i64 as Reflect>::error(&Value::None),
  "expected integer, found none",
);

Object Safety§

This trait is not object safe.

Trait typst::foundations::ReflectCopy item path

Required Methods§

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

Provided Methods§

fn error(found: &Value) -> EcoString

Object Safety§

Implementations on Foreign Types§

impl Reflect for Month

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for MathClass

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for bool

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for char

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for f64

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for i8

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for i16

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for i32

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for i64

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for isize

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for u8

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for u16

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for u32

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for u64

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for ()

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for usize

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for String

fn input() -> CastInfo

fn output() -> CastInfo

fn castable(value: &Value) -> bool

impl Reflect for NonZeroI64

fn input() -> CastInfo

fn output() -> CastInfo

Trait typst::foundations::Reflect