Fix last nits
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2919e32686
commit
471370a16b
3 changed files with 54 additions and 49 deletions
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@ -1581,7 +1581,8 @@ pub fn expand_type(t: P<ast::Ty>, fld: &mut MacroExpander) -> P<ast::Ty> {
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"type_macros",
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t.span,
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"type macros are experimental (see issue: #27336)");
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t
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DummyResult::raw_ty(t.span)
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}
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}
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_ => t
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@ -14,6 +14,7 @@ macro_rules! Id {
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struct Foo<T> {
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x: Id!(T)
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//~^ ERROR: type macros are experimental (see issue: #27336)
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}
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fn main() {
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@ -13,74 +13,77 @@
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use std::ops::*;
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#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
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struct Nil; // empty HList
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struct Nil;
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// empty HList
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#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
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struct Cons<H, T: HList>(H, T); // cons cell of HList
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struct Cons<H, T: HList>(H, T);
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// cons cell of HList
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// trait to classify valid HLists
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trait HList {}
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impl HList for Nil {}
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impl<H, T: HList> HList for Cons<H, T> {}
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// trait to classify valid HLists
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trait HList { }
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impl HList for Nil { }
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impl <H, T: HList> HList for Cons<H, T> { }
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// term-level macro for HLists
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macro_rules! hlist {
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{} => { Nil };
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{ $head:expr } => { Cons($head, Nil) };
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{ $head:expr, $($tail:expr),* } => { Cons($head, hlist!($($tail),*)) };
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}
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macro_rules! hlist({ } => { Nil } ; { $ head : expr } => {
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Cons ( $ head , Nil ) } ; {
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$ head : expr , $ ( $ tail : expr ) , * } => {
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Cons ( $ head , hlist ! ( $ ( $ tail ) , * ) ) } ;);
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// type-level macro for HLists
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macro_rules! HList {
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{} => { Nil };
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{ $head:ty } => { Cons<$head, Nil> };
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{ $head:ty, $($tail:ty),* } => { Cons<$head, HList!($($tail),*)> };
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}
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macro_rules! HList({ } => { Nil } ; { $ head : ty } => {
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Cons < $ head , Nil > } ; {
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$ head : ty , $ ( $ tail : ty ) , * } => {
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Cons < $ head , HList ! ( $ ( $ tail ) , * ) > } ;);
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// nil case for HList append
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impl<Ys: HList> Add<Ys> for Nil {
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type Output = Ys;
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impl <Ys: HList> Add<Ys> for Nil {
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type
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Output
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=
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Ys;
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fn add(self, rhs: Ys) -> Ys {
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rhs
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}
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fn add(self, rhs: Ys) -> Ys { rhs }
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}
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// cons case for HList append
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impl<Rec: HList + Sized, X, Xs: HList, Ys: HList> Add<Ys> for Cons<X, Xs> where
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Xs: Add<Ys, Output = Rec>,
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{
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type Output = Cons<X, Rec>;
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impl <Rec: HList + Sized, X, Xs: HList, Ys: HList> Add<Ys> for Cons<X, Xs>
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where Xs: Add<Ys, Output = Rec> {
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type
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Output
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=
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Cons<X, Rec>;
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fn add(self, rhs: Ys) -> Cons<X, Rec> {
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Cons(self.0, self.1 + rhs)
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}
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fn add(self, rhs: Ys) -> Cons<X, Rec> { Cons(self.0, self.1 + rhs) }
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}
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// type macro Expr allows us to expand the + operator appropriately
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macro_rules! Expr {
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{ ( $($LHS:tt)+ ) } => { Expr!($($LHS)+) };
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{ HList ! [ $($LHS:tt)* ] + $($RHS:tt)+ } => {
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<Expr!(HList![$($LHS)*]) as Add<Expr!($($RHS)+)>>::Output
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};
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{ $LHS:tt + $($RHS:tt)+ } => { <Expr!($LHS) as Add<Expr!($($RHS)+)>>::Output };
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{ $LHS:ty } => { $LHS };
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}
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macro_rules! Expr({ ( $ ( $ LHS : tt ) + ) } => { Expr ! ( $ ( $ LHS ) + ) } ;
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{ HList ! [ $ ( $ LHS : tt ) * ] + $ ( $ RHS : tt ) + } => {
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< Expr ! ( HList ! [ $ ( $ LHS ) * ] ) as Add < Expr ! (
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$ ( $ RHS ) + ) >> :: Output } ; {
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$ LHS : tt + $ ( $ RHS : tt ) + } => {
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< Expr ! ( $ LHS ) as Add < Expr ! ( $ ( $ RHS ) + ) >> ::
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Output } ; { $ LHS : ty } => { $ LHS } ;);
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// test demonstrating term level `xs + ys` and type level `Expr!(Xs + Ys)`
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fn main() {
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fn aux<Xs: HList, Ys: HList>(xs: Xs, ys: Ys) -> Expr!(Xs + Ys)
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where Xs: Add<Ys> {
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xs + ys
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}
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fn aux<Xs: HList, Ys: HList>(xs: Xs, ys: Ys) -> Expr!(Xs + Ys) where
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Xs: Add<Ys> {
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xs + ys
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}
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let xs: HList![&str, bool, Vec<u64>] = hlist!["foo", false, vec![]];
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let ys: HList![u64, [u8; 3], ()] = hlist![0, [0, 1, 2], ()];
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let xs: HList!(& str , bool , Vec < u64 >) =
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hlist!("foo" , false , vec ! [ ]);
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let ys: HList!(u64 , [ u8 ; 3 ] , ( )) =
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hlist!(0 , [ 0 , 1 , 2 ] , ( ));
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// demonstrate recursive expansion of Expr!
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let zs: Expr!((HList![&str] + HList![bool] + HList![Vec<u64>]) +
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(HList![u64] + HList![[u8; 3], ()]) +
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HList![])
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= aux(xs, ys);
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assert_eq!(zs, hlist!["foo", false, vec![], 0, [0, 1, 2], ()])
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let zs:
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Expr!((
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HList ! [ & str ] + HList ! [ bool ] + HList ! [ Vec < u64 >
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] ) + ( HList ! [ u64 ] + HList ! [ [ u8 ; 3 ] , ( ) ] ) +
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HList ! [ ]) = aux(xs, ys);
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assert_eq!(zs , hlist ! [
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"foo" , false , vec ! [ ] , 0 , [ 0 , 1 , 2 ] , ( ) ])
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}
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