* The double semicolon at the end of an interface-file signature is so that
the lexer can run through the pragmas very fast when -O isn't being used.
-* In export lists, T!(A,B) says that constructors A and B are exported,
- but not the type T. Similarly for classes.
+* In export lists, T|(A,B) says that constructors A and B are exported,
+ but not the type T. Similarly for classes.
+ We can't say T(T,A,B) and T(A,B) to export or not-export T respectively,
+ because the type T might have a constructor T.
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