Add support for single-line # comments

Comments currently do not go into the AST, they are just ignored when
parsing the file.

Resolves #32.

Author: polybuildr

src/grammar.rustpeg

@@ -231,9 +231,13 @@ identifier -> String
 _identifier -> String
     = !reserved_identifier i:$([a-zA-Z_][a-zA-Z0-9_]*[!?]?) { i.to_string() }
 
-__ = whitespace*
+__ = #quiet<(whitespace / comment)*>
 
-whitespace = #quiet<[ \t\n]>
+comment = "#" (!eol_char .)*
+
+eol_char = [\n\r]
+
+whitespace = [ \t\n\r]
 
 EQUALS = #quiet<"="> / #expected("equals")
 

tests/run-pass/comments.bl

@@ -0,0 +1,15 @@
+# comment
+fn f() {#comment
+    var x = 5; # comment
+    if true { #comment
+        # comment
+        x = 20;#comment
+    } # comment
+    else {
+        x = 10;
+    } # comment
+    return x; #comment
+    # comment
+} #comment
+# comment
+assert_eq(f(), 20); # comment