Attribute Macro assert_type_match

#[assert_type_match]

An attribute macro that can be used to statically verify that the annotated struct or enum matches the structure of a foreign type.

For structs, it will verify that the fields of the annotated struct match the fields of the foreign struct.

For enums, it will verify that the variants of the annotated enum match the variants of the foreign enum, and that the fields of each variant match the fields of the corresponding variant in the foreign enum.

This will also output the original annotated struct or enum, unless the test_only argument is set to true.

Arguments

This macro accepts arguments to control its behavior. These arguments are passed as a comma-separated list after the foreign type.

All boolean arguments may be set to true by using either the foo or foo = true syntax.

test_only

Type: bool

Controls whether to output the annotated struct or enum in the generated code.

from

Type: bool

Controls whether a From implementation should be generated.

If true, two From implementations will be generated: one for converting from the annotated type to the foreign type, and one for converting from the foreign type to the annotated type.

skip_name

Type: bool

Controls whether checking that the name of the annotated struct or enum matches the name of the foreign type should be skipped.

For example, comparing struct Foo(u32) to struct Bar(u32) would pass when this argument is set to true.

skip_types

Type: bool

Controls whether checking field types should be skipped.

For example, comparing struct Foo(i32) to struct Foo(f32) would pass when this argument is set to true.

Field Arguments

This macro also supports field attributes.

These are also defined with the #[assert_type_match(...)] attribute.

skip

Type: bool

Controls whether the field should be skipped.

This allows you to skip fields that are not present on the foreign type.

skip_type

Type: bool

Controls whether checking the field type should be skipped.

Variant Arguments

This macro also supports variant attributes.

These are also defined with the #[assert_type_match(...)] attribute.

skip

Type: bool

Controls whether the variant should be skipped.

This allows you to skip variants that are not present on the foreign type.

Example

A passing example:

mod other {
    pub struct Test {
        pub x: i32,
        pub y: i32,
    }
}

#[assert_type_match(other::Test)]
struct Test {
    x: i32,
    y: i32,
}

A failing example:

mod other {
    pub struct Test {
        pub x: i32,
        pub y: i32,
    }
}

#[assert_type_match(other::Test)]
struct Test {
    x: i32,
    z: i32, // Error: struct `other::Test` has no field named `z`
}