Merge pull request #2036 from ronaldxs/grammar_totorial-role-clarification

grammar_totorial.pm6 clarification of extending grammars with roles

Author: JJ

doc/Language/grammar_tutorial.pod6

@@ -301,7 +301,14 @@ grammar Quoted-Other does Letters does Quote-Other {
 }
 =end code
 
-Will output exactly the same as the code above.
+Will output exactly the same as the code above.  Symptomatic of the difference
+between Classes and Roles, a conflict like defining C<token quote> twice
+using Role composition will result in an error:
+
+=begin code
+grammar Quoted-Quotes does Letters does Quote-Quotes does Quote-Other { ... }
+# OUTPUT: ... Error while compiling ... Method 'quote' must be resolved ...
+=end code
 
 =head2 Adding some constraints