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Record accessors respect subtyping

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* module/ice-9/boot-9.scm (make-record-type): Don't allow subtyping of
  final types.
  (%record-type-error): Remove helper.
  (record-accessor, record-modifier): Use computed record type
  predicate, to allow for subtyping.
  (define-record-type): Adapt to %record-type-error going away; these
  types are final so no accessor adaptation is needed.
* test-suite/tests/records.test: Add tests.
* doc/ref/api-data.texi (Records): Update.
This commit is contained in:
Andy Wingo 2019-10-22 15:05:14 +02:00
commit f060f1a4e6
3 changed files with 108 additions and 41 deletions
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28
doc/ref/api-data.texi
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@ -8630,7 +8630,8 @@ Note that @code{record?} may be true of any Scheme value; there is no
promise that records are disjoint with other Scheme types.
@end deffn
@deffn {Scheme Procedure} make-record-type type-name field-names [print]
@deffn {Scheme Procedure} make-record-type type-name field-names [print] @
[#:final?=@code{#t}] [parent=@code{#f}]
Create and return a new @dfn{record-type descriptor}.
@var{type-name} is a string naming the type. Currently it's only used
@ -8646,19 +8647,24 @@ The optional @var{print} argument is a function used by
@code{display}, @code{write}, etc, for printing a record of the new
type. It's called as @code{(@var{print} record port)} and should look
at @var{record} and write to @var{port}.
Pass the @code{#:parent} keyword to derive a record type from a
supertype. A derived record type has the fields from its parent type,
followed by fields declared in the @code{make-record-type} call. Record
predicates and field accessors for instance of a parent type will also
work on any instance of a subtype.
@cindex final record types
@cindex record types, final
Allowing record subtyping has a small amount of overhead. To avoid this
overhead, declare the record type as @dfn{final} by passing
@code{#:final? #t}. Record types in Guile are final by default.
@end deffn
@deffn {Scheme Procedure} record-constructor rtd [field-names]
@deffn {Scheme Procedure} record-constructor rtd
Return a procedure for constructing new members of the type represented
by @var{rtd}. The returned procedure accepts exactly as many arguments
as there are symbols in the given list, @var{field-names}; these are
used, in order, as the initial values of those fields in a new record,
which is returned by the constructor procedure. The values of any
fields not named in that list are unspecified. The @var{field-names}
argument defaults to the list of field names in the call to
@code{make-record-type} that created the type represented by @var{rtd};
if the @var{field-names} argument is provided, it is an error if it
contains any duplicates or any symbols not in the default list.
by @var{rtd}. The result will be a procedure accepting exactly as many
arguments as there are fields in the record type.
@end deffn
@deffn {Scheme Procedure} record-predicate rtd