Merge pull request #535 from epage/seq

fix(comb): Clarify `seq`s behavior

src/macros/seq.rs

@@ -1,5 +1,13 @@
 /// Initialize a struct or tuple out of a sequences of parsers
 ///
+/// Unlike normal struct initialization syntax:
+/// - `_` fields can exist to run a parser but ignore the result
+/// - Parse results for a field can later be referenced using the field name
+///
+/// Unlike normal tuple initialization syntax:
+/// - Struct-style initialization (`{ 0: _, 1: _}`) is not supported
+/// - `_: <parser>` fields can exist to run a parser but ignore the result
+///
 ///# Example
 ///
 /// ```
@@ -53,39 +61,6 @@
 /// },
 /// )),
 /// );
-///
-/// // Or parse into enum variants
-/// #[derive(Debug, PartialEq, Eq)]
-/// enum Expr {
-/// Add { lhs: u32, rhs: u32 },
-/// Mul(u32, u32),
-/// }
-///
-/// fn add(input: &mut &[u8]) -> PResult<Expr> {
-/// seq!{Expr::Add {
-/// lhs: dec_uint::<_, u32, ContextError>,
-/// _: b" + ",
-/// rhs: dec_uint::<_, u32, ContextError>,
-/// }}.parse_next(input)
-/// }
-///
-/// fn mul(input: &mut &[u8]) -> PResult<Expr> {
-/// seq!(Expr::Mul(
-/// dec_uint::<_, u32, ContextError>,
-/// _: b" * ",
-/// dec_uint::<_, u32, ContextError>,
-/// )).parse_next(input)
-/// }
-///
-/// assert_eq!(
-/// add.parse_peek(&b"1 + 2"[..]),
-/// Ok((&b""[..], Expr::Add { lhs: 1, rhs: 2 })),
-/// );
-///
-/// assert_eq!(
-/// mul.parse_peek(&b"3 * 4"[..]),
-/// Ok((&b""[..], Expr::Mul(3, 4))),
-/// );
 /// ```
 #[macro_export]
 #[doc(alias = "tuple")]
@@ -99,15 +74,13 @@
 macro_rules! seq {
  ($($name: ident)::* { $($fields: tt)* }) => {
  $crate::combinator::trace(stringify!($($name)::*), move |input: &mut _| {
- use $crate::Parser;
  $crate::seq_parse_struct_fields!(input; $($fields)*);
  #[allow(clippy::redundant_field_names)]
  Ok($crate::seq_init_struct_fields!( ($($fields)*); $($name)::*;))
  })
  };
  ($($name: ident)::* ( $($elements: tt)* )) => {
  $crate::combinator::trace(stringify!($($name)::*), move |input: &mut _| {
- use $crate::Parser;
  $crate::seq_parse_tuple_fields!( ($($elements)*) ; ).map(|t| {
  $crate::seq_init_tuple_fields!(
  ($($elements)*);
@@ -141,27 +114,27 @@ macro_rules! seq_parse_struct_fields {
  $input: ident;
  _ : $head_parser: expr, $($fields: tt)*
  ) => {
- let _ = $head_parser.parse_next($input)?;
+ let _ = $crate::Parser::parse_next(&mut $head_parser, $input)?;
  $crate::seq_parse_struct_fields!($input; $($fields)*)
  };
  (
  $input: ident;
  _ : $head_parser: expr
  ) => {
- let _ = $head_parser.parse_next($input)?;
+ let _ = $crate::Parser::parse_next(&mut $head_parser, $input)?;
  };
  (
  $input: ident;
  $head_field: ident : $head_parser: expr, $($fields: tt)*
  ) => {
- let $head_field = $head_parser.parse_next($input)?;
+ let $head_field = $crate::Parser::parse_next(&mut $head_parser, $input)?;
  $crate::seq_parse_struct_fields!($input; $($fields)*)
  };
  (
  $input: ident;
  $head_field: ident : $head_parser: expr
  ) => {
- let $head_field = $head_parser.parse_next($input)?;
+ let $head_field = $crate::Parser::parse_next(&mut $head_parser, $input)?;
  };
  (
  $input: expr;

src/macros/test.rs

@@ -187,6 +187,43 @@ fn seq_struct_no_trailing_comma_elided() {
  }
 }
 
+#[test]
+fn seq_enum_struct_variant() {
+ #[derive(Debug, PartialEq, Eq)]
+ enum Expr {
+ Add { lhs: u32, rhs: u32 },
+ Mul(u32, u32),
+ }
+
+ fn add(input: &mut &[u8]) -> PResult<Expr> {
+ seq! {Expr::Add {
+ lhs: dec_uint::<_, u32, _>,
+ _: b" + ",
+ rhs: dec_uint::<_, u32, _>,
+ }}
+ .parse_next(input)
+ }
+
+ fn mul(input: &mut &[u8]) -> PResult<Expr> {
+ seq!(Expr::Mul(
+ dec_uint::<_, u32, _>,
+ _: b" * ",
+ dec_uint::<_, u32, _>,
+ ))
+ .parse_next(input)
+ }
+
+ assert_eq!(
+ add.parse_peek(&b"1 + 2"[..]),
+ Ok((&b""[..], Expr::Add { lhs: 1, rhs: 2 })),
+ );
+
+ assert_eq!(
+ mul.parse_peek(&b"3 * 4"[..]),
+ Ok((&b""[..], Expr::Mul(3, 4))),
+ );
+}
+
 #[test]
 fn seq_tuple_struct_basics() {
  #[derive(Debug, PartialEq)]