Make match_ignore_ascii_case! future-proof.

Change the usage syntax to require a comma on the last non-fallback arm,
which is a [breaking-change].

The old definition has started to emit a warning in recent nightlies
and is likely to be an error in future versions:
rust-lang/rfcs#1384

The new definition is recursive to resolve ambiguities.
Unfortunately this makes error reporting terrible:
rust-lang/rust#31022

Author: SimonSapin

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cssparser"
-version = "0.4.0"
+version = "0.5.0"
 authors = [ "Simon Sapin <simon.sapin@exyr.org>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"

src/color.rs

@@ -258,7 +258,7 @@ pub fn parse_color_keyword(ident: &str) -> Result<Color, ()> {
         "yellowgreen" => rgb(154., 205., 50.),
 
         "transparent" => Ok(Color::RGBA(RGBA { red: 0., green: 0., blue: 0., alpha: 0. })),
-        "currentcolor" => Ok(Color::CurrentColor)
+        "currentcolor" => Ok(Color::CurrentColor),
         _ => Err(())
     }
 }
@@ -312,7 +312,7 @@ fn parse_color_function(name: &str, arguments: &mut Parser) -> Result<Color, ()>
         "rgba" => (true, true),
         "rgb" => (true, false),
         "hsl" => (false, false),
-        "hsla" => (false, true)
+        "hsla" => (false, true),
         _ => return Err(())
     };
 

src/lib.rs

@@ -69,6 +69,8 @@ fn parse_border_spacing(_context: &ParserContext, input: &mut Parser)
 
 */
 
+#![recursion_limit="200"]  // For color::parse_color_keyword
+
 extern crate encoding;
 #[macro_use] extern crate matches;
 #[cfg(test)] extern crate tempdir;
@@ -99,21 +101,29 @@ Usage example:
 match_ignore_ascii_case! { string,
     "foo" => Some(Foo),
     "bar" => Some(Bar),
-    "baz" => Some(Baz)
+    "baz" => Some(Baz),
     _ => None
 }
 ```
 
 The macro also takes a slice of the value,
 so that a `String` or `CowString` could be passed directly instead of a `&str`.
 
-Note that because of `macro_rules` ambiguity resolutions quirks,
-each arm except the fallback and the one before it must end with a comma.
-
 */
 #[macro_export]
 macro_rules! match_ignore_ascii_case {
-    ( $value: expr, $( $string: expr => $result: expr ),+ _ => $fallback: expr ) => {
+    // parse the last case plus the fallback
+    (@inner $value:expr, ($string:expr => $result:expr, _ => $fallback:expr) -> ($($parsed:tt)*) ) => {
+        match_ignore_ascii_case!(@inner $value, () -> ($($parsed)* ($string => $result)) $fallback)
+    };
+
+    // parse a case (not the last one)
+    (@inner $value:expr, ($string:expr => $result:expr, $($rest:tt)*) -> ($($parsed:tt)*) ) => {
+        match_ignore_ascii_case!(@inner $value, ($($rest)*) -> ($($parsed)* ($string => $result)))
+    };
+
+    // finished parsing
+    (@inner $value:expr, () -> ($(($string:expr => $result:expr))*) $fallback:expr ) => {
         {
             use std::ascii::AsciiExt;
             match &$value[..] {
@@ -124,8 +134,12 @@ macro_rules! match_ignore_ascii_case {
             }
         }
     };
-}
 
+    // entry point, start parsing
+    ( $value:expr, $($rest:tt)* ) => {
+        match_ignore_ascii_case!(@inner $value, ($($rest)*) -> ())
+    };
+}
 
 mod rules_and_declarations;
 mod tokenizer;

src/nth.rs

@@ -18,7 +18,7 @@ pub fn parse_nth(input: &mut Parser) -> Result<(i32, i32), ()> {
             let a = try!(value.int_value.ok_or(())) as i32;
             match_ignore_ascii_case! { unit,
                 "n" => parse_b(input, a),
-                "n-" => parse_signless_b(input, a, -1)
+                "n-" => parse_signless_b(input, a, -1),
                 _ => Ok((a, try!(parse_n_dash_digits(&*unit))))
             }
         }
@@ -29,7 +29,7 @@ pub fn parse_nth(input: &mut Parser) -> Result<(i32, i32), ()> {
                 "n" => parse_b(input, 1),
                 "-n" => parse_b(input, -1),
                 "n-" => parse_signless_b(input, 1, -1),
-                "-n-" => parse_signless_b(input, -1, -1)
+                "-n-" => parse_signless_b(input, -1, -1),
                 _ => if value.starts_with("-") {
                     Ok((-1, try!(parse_n_dash_digits(&value[1..]))))
                 } else {
@@ -41,7 +41,7 @@ pub fn parse_nth(input: &mut Parser) -> Result<(i32, i32), ()> {
             Token::Ident(value) => {
                 match_ignore_ascii_case! { value,
                     "n" => parse_b(input, 1),
-                    "n-" => parse_signless_b(input, 1, -1)
+                    "n-" => parse_signless_b(input, 1, -1),
                     _ => Ok((1, try!(parse_n_dash_digits(&*value))))
                 }
             }