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rollup merge of #20563: cmr/macro-input-future-proofing

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Alex Crichton 2015-01-06 15:49:15 -08:00
commit 26cd8eae48
12 changed files with 404 additions and 187 deletions
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36
src/doc/guide-macros.md
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@ -161,7 +161,7 @@ instead of `*` to mean "at least one".
# let input_1 = T::SpecialA(0);
# let input_2 = T::SpecialA(0);
macro_rules! early_return {
($inp:expr, [ $($sp:path)|+ ]) => (
($inp:expr, [ $($sp:path),+ ]) => (
match $inp {
$(
$sp(x) => { return x; }
@ -171,7 +171,7 @@ macro_rules! early_return {
)
}
// ...
early_return!(input_1, [T::SpecialA|T::SpecialC|T::SpecialD]);
early_return!(input_1, [T::SpecialA,T::SpecialC,T::SpecialD]);
// ...
early_return!(input_2, [T::SpecialB]);
# return 0;
@ -245,7 +245,7 @@ can solve the problem:
~~~~
macro_rules! biased_match {
// special case: `let (x) = ...` is illegal, so use `let x = ...` instead
( ($e:expr) ~ ($p:pat) else $err:stmt ;
( ($e:expr) -> ($p:pat) else $err:stmt ;
binds $bind_res:ident
) => (
let $bind_res = match $e {
@ -254,7 +254,7 @@ macro_rules! biased_match {
};
);
// more than one name; use a tuple
( ($e:expr) ~ ($p:pat) else $err:stmt ;
( ($e:expr) -> ($p:pat) else $err:stmt ;
binds $( $bind_res:ident ),*
) => (
let ( $( $bind_res ),* ) = match $e {
@ -268,9 +268,9 @@ macro_rules! biased_match {
# struct T2 { body: T3 }
# enum T3 { Good2(uint), Bad2}
# fn f(x: T1) -> uint {
biased_match!((x) ~ (T1::Good1(g1, val)) else { return 0 };
biased_match!((x) -> (T1::Good1(g1, val)) else { return 0 };
binds g1, val );
biased_match!((g1.body) ~ (T3::Good2(result) )
biased_match!((g1.body) -> (T3::Good2(result) )
else { panic!("Didn't get good_2") };
binds result );
// complicated stuff goes here
@ -286,7 +286,7 @@ pattern we want is clear:
~~~~
# fn main() {}
# macro_rules! b {
( $( ($e:expr) ~ ($p:pat) else $err:stmt ; )*
( $( ($e:expr) -> ($p:pat) else $err:stmt ; )*
binds $( $bind_res:ident ),*
)
# => (0) }
@ -317,8 +317,8 @@ input patterns:
~~~~
# fn main() {}
# macro_rules! b {
( ($e :expr) ~ ($p :pat) else $err :stmt ;
$( ($e_rest:expr) ~ ($p_rest:pat) else $err_rest:stmt ; )*
( ($e :expr) -> ($p :pat) else $err :stmt ;
$( ($e_rest:expr) -> ($p_rest:pat) else $err_rest:stmt ; )*
binds $( $bind_res:ident ),*
)
# => (0) }
@ -333,14 +333,14 @@ piece of syntax (the `let`) which we only want to transcribe once.
macro_rules! biased_match_rec {
// Handle the first layer
( ($e :expr) ~ ($p :pat) else $err :stmt ;
$( ($e_rest:expr) ~ ($p_rest:pat) else $err_rest:stmt ; )*
( ($e :expr) -> ($p :pat) else $err :stmt ;
$( ($e_rest:expr) -> ($p_rest:pat) else $err_rest:stmt ; )*
binds $( $bind_res:ident ),*
) => (
match $e {
$p => {
// Recursively handle the next layer
biased_match_rec!($( ($e_rest) ~ ($p_rest) else $err_rest ; )*
biased_match_rec!($( ($e_rest) -> ($p_rest) else $err_rest ; )*
binds $( $bind_res ),*
)
}
@ -354,20 +354,20 @@ macro_rules! biased_match_rec {
// Wrap the whole thing in a `let`.
macro_rules! biased_match {
// special case: `let (x) = ...` is illegal, so use `let x = ...` instead
( $( ($e:expr) ~ ($p:pat) else $err:stmt ; )*
( $( ($e:expr) -> ($p:pat) else $err:stmt ; )*
binds $bind_res:ident
) => (
let $bind_res = biased_match_rec!(
$( ($e) ~ ($p) else $err ; )*
$( ($e) -> ($p) else $err ; )*
binds $bind_res
);
);
// more than one name: use a tuple
( $( ($e:expr) ~ ($p:pat) else $err:stmt ; )*
( $( ($e:expr) -> ($p:pat) else $err:stmt ; )*
binds $( $bind_res:ident ),*
) => (
let ( $( $bind_res ),* ) = biased_match_rec!(
$( ($e) ~ ($p) else $err ; )*
$( ($e) -> ($p) else $err ; )*
binds $( $bind_res ),*
);
)
@ -379,8 +379,8 @@ macro_rules! biased_match {
# enum T3 { Good2(uint), Bad2}
# fn f(x: T1) -> uint {
biased_match!(
(x) ~ (T1::Good1(g1, val)) else { return 0 };
(g1.body) ~ (T3::Good2(result) ) else { panic!("Didn't get Good2") };
(x) -> (T1::Good1(g1, val)) else { return 0 };
(g1.body) -> (T3::Good2(result) ) else { panic!("Didn't get Good2") };
binds val, result );
// complicated stuff goes here
return result + val;