Macro has_structure

macro_rules! has_structure {
    ( $variant:path { $( $field:ident : $matcher:expr ),* $(,)* } ) => { ... };
    ( $variant:path [ $( $matchers:expr ),* ] ) => { ... };
}

Write patterns of structs/enums which use Matchers instead of field values.

When providing matchers for multiple fields, not that all matchers will be evaluated. Even if one of them returns MatchResult::Failed.

For struct-like structs/enum-variants not all fields need to be listed in the pattern. Unwanted fields can safely be ommitted. For tuple-like structs/enum-variants all fields need to be listed in the correct order. Although you can use any_value() to effectively ignore the field.

Note that the correct brace/bracket style for tuple-like structs/enums is Variant[any_value(), any_value()] not Variant(any_value(), any_value()). This discrepancy is due to macro parsing reasons.

#Examples

// Matching a struct-like ...
use galvanic_assert::matchers::*;
struct Foo { x: i32, y: f64 }
let foo = Foo { x: 12, y: 23.4 };
assert_that!(&foo, has_structure!(Foo {
    x: eq(12),
    y: lt(25.0)
}));
assert_that!(&foo, has_structure!(Foo {
    y: lt(25.0) // not all fields need to be given for struct-likes
}));

// Matching a tuple-like ...
struct Bar(i32, f64);
let bar = Bar(12, 23.4);
assert_that!(&bar, has_structure!(Bar[ eq(12), lt(25.0) ]));

// Matching enum variants ...
enum Baz {
    Var1 { x: i32, y: f64 },
    Var2(i32, f64)
}
let var1 = Baz::Var1 { x: 12, y: 23.4 };
assert_that!(&var1, has_structure!(Baz::Var1 {
    x: eq(12),
    y: lt(25.0)
}));

let var2 = Baz::Var2(12, 23.4);
assert_that!(&var2, has_structure!(Baz::Var2 [eq(12), lt(25.0)] ));