StructDefinition

std::meta::struct_def contains methods on the built-in StructDefinition type. This type corresponds to struct Name { field1: Type1, ... } items in the source program.

Methods

add_attribute

add_attribute

pub comptime fn add_attribute<let N: u32>(self, attribute: str<N>) {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L3-L5}}

Adds an attribute to the struct.

add_generic

add_generic

pub comptime fn add_generic<let N: u32>(self, generic_name: str<N>) -> Type {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L8-L10}}

Adds an generic to the struct. Returns the new generic type. Errors if the given generic name isn't a single identifier or if the struct already has a generic with the same name.

This method should be used carefully, if there is existing code referring to the struct type it may be checked before this function is called and see the struct with the original number of generics. This method should thus be preferred to use on code generated from other macros and structs that are not used in function signatures.

Example:

add-generic-example

comptime fn add_generic(s: StructDefinition) {
        assert_eq(s.generics().len(), 0);
        let new_generic = s.add_generic("T");

        let generics = s.generics();
        assert_eq(generics.len(), 1);
        assert_eq(generics[0], new_generic);
    }

^{_{Source code: test_programs/compile_success_empty/comptime_struct_definition/src/main.nr#L35-L44}}

as_type

as_type

pub comptime fn as_type(self) -> Type {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L15-L17}}

Returns this struct as a type in the source program. If this struct has any generics, the generics are also included as-is.

generics

generics

pub comptime fn generics(self) -> [Type] {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L26-L28}}

Returns each generic on this struct.

Example:

#[example]
struct Foo<T, U> {
    bar: [T; 2],
    baz: Baz<U, U>,
}

comptime fn example(foo: StructDefinition) {
    assert_eq(foo.generics().len(), 2);

    // Fails because `T` isn't in scope
    // let t = quote { T }.as_type();
    // assert_eq(foo.generics()[0], t);
}

fields

fields

pub comptime fn fields(self) -> [(Quoted, Type)] {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L33-L35}}

Returns each field of this struct as a pair of (field name, field type).

has_named_attribute

has_named_attribute

pub comptime fn has_named_attribute<let N: u32>(self, name: str<N>) -> bool {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L20-L22}}

Returns true if this struct has a custom attribute with the given name.

module

module

pub comptime fn module(self) -> Module {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L38-L40}}

Returns the module where the struct is defined.

name

name

pub comptime fn name(self) -> Quoted {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L43-L45}}

Returns the name of this struct

Note that the returned quoted value will be just the struct name, it will not be the full path to the struct, nor will it include any generics.

set_fields

set_fields

pub comptime fn set_fields(self, new_fields: [(Quoted, Type)]) {}

^{_{Source code: noir_stdlib/src/meta/struct_def.nr#L52-L54}}

Sets the fields of this struct to the given fields list where each element is a pair of the field's name and the field's type. Expects each field name to be a single identifier. Note that this will override any previous fields on this struct. If those should be preserved, use .fields() to retrieve the current fields on the struct type and append the new fields from there.

Example:

// Change this struct to:
// struct Foo {
//     a: u32,
//     b: i8,
// }
#[mangle_fields]
struct Foo { x: Field }

comptime fn mangle_fields(s: StructDefinition) {
    s.set_fields(&[
        (quote { a }, quote { u32 }.as_type()),
        (quote { b }, quote { i8 }.as_type()),
    ]);
}

Trait Implementations

impl Eq for StructDefinition
impl Hash for StructDefinition

Note that each struct is assigned a unique ID internally and this is what is used for equality and hashing. So even structs with identical generics and fields may not be equal in this sense if they were originally different items in the source program.