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vector assertions.rs

//#![feature(trace_macros)]
//trace_macros!(true);

macro_rules! assert_vec_match{
    (@empty $vector:expr) => {
        if $vector.len() > 0 {
            panic!("Expected an empty vector, but the vector contained {} elements", $vector.len());
        }
    };

    (@match $idx:expr, $vector:expr, $pattern:pat if $cond:expr => $success:expr) => {
        if $vector.len() <= $idx {
            panic!("Could not match on index {} as the vector only has {} values", $idx, $vector.len());
        }
        
        match $vector[$idx] {
            $pattern if $cond => $success,
            _ => panic!("Match failed on index {}: {:?} vs {} ", $idx, $vector[$idx], stringify!($pattern)) 
        };
    };

    (@step $idx:expr, $vector:expr,) => {
        if $vector.len() > $idx {
            panic!("Vector contained {} elements but only {} was expected!", $vector.len(), $idx);
        }
    };
    
    (@step $idx:expr, $vector:expr) => {
        if $vector.len() > $idx {
            panic!("Vector contained {} elements but only {} was expected!", $vector.len(), $idx);
        }
    };
    
    // pattern if condition
    (@step $idx:expr, $vector:expr, $pattern:pat if $cond:expr, $($rest:tt)*) => {
        assert_vec_match!(@match $idx, $vector, $pattern if $cond => ());
        assert_vec_match!(@step $idx + 1usize, $vector, $($rest)*);
    };
    
    (@step $idx:expr, $vector:expr, $pattern:pat if $cond:expr) => {
        assert_vec_match!(@match $idx, $vector, $pattern if $cond => $success);
    };

    // pattern if condition => success
    (@step $idx:expr, $vector:expr, $pattern:pat if $cond:expr => $success:expr, $($rest:tt)*) => {
        assert_vec_match!(@match $idx, $vector, $pattern if $cond => $success);
        assert_vec_match!(@step $idx + 1usize, $vector, $($rest)*);
    };
    
    (@step $idx:expr, $vector:expr, $pattern:pat if $cond:expr => $success:expr) => {
        assert_vec_match!(@match $idx, $vector, $pattern if $cond => $success);
    };
    
    // pattern => success
    (@step $idx:expr, $vector:expr, $pattern:pat => $success:expr, $($rest:tt)*) => {
        assert_vec_match!(@match $idx, $vector, $pattern if true => $success);
        assert_vec_match!(@step $idx + 1usize, $vector, $($rest)*);
    };
    
    (@step $idx:expr, $vector:expr, $pattern:pat => $success:expr) => {
        assert_vec_match!(@match $idx, $vector, $pattern if true => $success);
    };
    
    // pattern only
    (@step $idx:expr, $vector:expr, $pattern:pat, $($rest:tt)*) => {
        assert_vec_match!(@match $idx, $vector, $pattern if true => ());
        assert_vec_match!(@step $idx + 1usize, $vector, $($rest)*);
    };
    
    (@step $idx:expr, $vector:expr, $pattern:pat) => {
        assert_vec_match!(@match $idx, $vector, $pattern if true => ());
    };
    
    // Entrypoints
    ($vector:expr, $pattern:pat if $cond:expr, $($rest:tt)*) => {
        assert_vec_match!(@step 0usize, $vector, $pattern if $cond => (), $($rest)*);
    };
    
    ($vector:expr, $pattern:pat => $success:expr, $($rest:tt)*) => {
        assert_vec_match!(@step 0usize, $vector, $pattern if true => $success, $($rest)*);
    };

    ($vector:expr, $pattern:pat if $cond:expr => $success:expr, $($rest:tt)*) => {
        assert_vec_match!(@step 0usize, $vector, $pattern if $cond => $success, $($rest)*);
    };
    
    ($vector:expr, $pattern:pat, $($rest:tt)*) => {
        assert_vec_match!(@step 0usize, $vector, $pattern if true => (), $($rest)*);
    };
    
    
    // Empty macro after vector
    ($vector:expr) => {
        assert_vec_match!(@empty $vector);
    };
    
    ($vector:expr,) => {
        assert_vec_match!(@empty $vector);
    };
}

fn main() {
    let test1 = Test::Value1 { v1: 5, v2: "test".to_string() };
    let test2 = Test::Value1 { v1: 8, v2: "test2".to_string() };
    let test3 = Test::Value1 { v1: 8, v2: "test3".to_string() };
    let test4 = Test::Value1 { v1: 8, v2: "test4".to_string() };
    let vector = vec![test2, test1, test3, test4];
    
    let result;
    
    assert_vec_match!(vector,
        Test::Value1 { v1: _, ref v2} if v2 == "test2",
        Test::Value1 { v1, ref v2} if v2 == "test" => {result = v1},
        Test::Value1 { v1: 8, v2: _} => (),
        Test::Value1 { v1: 8, v2: _},
    );
    
    //assert_vec_match!(vector);
    
    println!("{}", result);
}

#[derive(Debug)]
enum Test {
    Value1 { v1: u32, v2: String }
}