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The expression in a bit string comprehension is limited to a
literal bit string expression. That is, the following code
is legal:
<< <<X>> || X <- List >>
but not this code:
<< foo(X) || X <- List >>
The limitation is annoying. For one thing, tools that transform
the abstract format must be careful not to produce code such as:
<< begin
%% Some instrumentation code.
<<X>>
end || X <- List >>
One reason for the limitation could be that we'll get
reduce/reduce conflicts if we try to allow an arbitrary
expression in a bit string comprehension:
binary_comprehension -> '<<' expr '||' lc_exprs '>>' :
{bc,?anno('$1'),'$2','$4'}.
Unfortunately, there does not seem to be an easy way to work
around that problem. The best we can do is to allow 'expr_max'
expressions (as in the binary syntax):
binary_comprehension -> '<<' expr_max '||' lc_exprs '>>' :
{bc,?anno('$1'),'$2','$4'}.
That will work, but functions calls must be enclosed in
parentheses:
<< (foo(X)) || X <- List >>
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Calls to map_anno(), fold_anno(), and mapfold_anno() with lists of
erl_parse trees have been replaced. Those functions accept lists of
erl_parse trees, but it was not the intention when the functions were
introduced, and it is not documented.
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The syntax -spec/callback F/A :: FunctionType; has been removed.
No deprecation was deemed necessary.
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Background
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In record fields with a type declaration but without an initializer, the
Erlang parser inserted automatically the singleton type 'undefined' to
the list of declared types, if that value was not present there.
I.e. the record declaration:
-record(rec, {f1 :: float(),
f2 = 42 :: integer(),
f3 :: some_mod:some_typ()}).
was translated by the parser to:
-record(rec, {f1 :: float() | 'undefined',
f2 = 42 :: integer(),
f3 :: some_mod:some_typ() | 'undefined'}).
The rationale for this was that creation of a "dummy" #rec{} record
should not result in a warning from dialyzer that e.g. the implicit
initialization of the #rec.f1 field violates its type declaration.
Problems
---------
This seemingly innocent action has some unforeseen consequences.
For starters, there is no way for programmers to declare that e.g. only
floats make sense for the f1 field of #rec{} records when there is no
`obvious' default initializer for this field. (This also affects tools
like PropEr that use these declarations produced by the Erlang parser to
generate random instances of records for testing purposes.)
It also means that dialyzer does not warn if e.g. an is_atom/1 test or
something more exotic like an atom_to_list/1 call is performed on the
value of the f1 field.
Similarly, there is no way to extend dialyzer to warn if it finds record
constructions where f1 is not initialized to some float.
Last but not least, it is semantically problematic when the type of the
field is an opaque type: creating a union of an opaque and a structured
type is very problematic for analysis because it fundamentally breaks
the opacity of the term at that point.
Change
-------
To solve these problems the parser will not automatically insert the
'undefined' value anymore; instead the user has the option to choose the
places where this value makes sense (for the field) and where it does
not and insert the | 'undefined' there manually.
Consequences of this change
----------------------------
This change means that dialyzer will issue a warning for all places
where records with uninitialized fields are created and those fields have
a declared type that is incompatible with 'undefined' (e.g. float()).
This warning can be suppressed easily by adding | 'undefined' to the
type of this field. This also adds documentation that the user really
intends to create records where this field is uninitialized.
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The recently added module erl_anno can no longer handle
negative line numbers.
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Add new functions erl_parse:type_inop_prec() and
erl_parse:type_preop_prec().
Get rid of paren_type used for parentheses in types.
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Introduce erl_anno, an abstraction of the second element of tokens and
tuples in the abstract format. The convention that negative line
numbers can be used for silencing compiler warnings will no longer
work in OTP 19; instead the annotation 'generated' is to be used.
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Robert has OK'ed the removal of the token ':-'.
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Currently Name/Arity syntax is supported in list and tuple terms. This change makes it possible to use this syntax in map terms for consistency and convenience.
Example:
-custom(#{test1 => init/2, test2 => [val/1, val/2]}).
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* fenollp/remove-erl_parse-legacy-map:
Replace local mapl/2 (Erlang < 5.0) unique call by a LC
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Types are represented by quadruples {type, LINE, Name, Args},
but maps were represented by five-tuples
{type, LINE, map_field_assoc, Dom, Range}.
Note: this is *not* about the quadruples used for representing
expressions, {map_field_assoc,L,K,V}.
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"... when _ :: ..." used to compile, but Dialyzer crashed.
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product/_, union/_, range/2 as well as tuple/N (N > 0), map/N (N > 0),
atom/1, integer/1, binary/2, record/_, and 'fun'/_ can now be used as
type names.
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The 'encoding' option of erl_parse:abstract/2 has been extended to
include 'none' and a callback function (a predicate).
The rationale is that a more general means of determining what integer
lists are to be represented as strings may help readability when
generating Erlang code given input in some other encoding than Latin-1
or UTF-8.
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Name conforms to EEP.
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In the current iteration of Maps we should deny *any* variables in
Map keys.
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Did not handle Maps.
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Example how to construct:
#{ K1 => V1, K2 => V2 }
How to update:
M#{ K1 => V1, K2 := V2 }
How to match:
#{ K1 := V1, K2 := V2 } = M
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Example how to match or construct:
#{ K1 => V1, K2 => V2 }
How to update:
M#{ K => V }
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This adds optional names to fun expressions. A named fun expression
is parsed as a tuple `{named_fun,Loc,Name,Clauses}` in erl_parse.
If a fun expression has a name, it must be present and be the same in
every of its clauses. The function name shadows the environment of the
expression shadowing the environment and it is shadowed by the
environment of the clauses' arguments. An unused function name triggers
a warning unless it is prefixed by _, just as every variable.
Variable _ is allowed as a function name.
It is not an error to put a named function in a record field default
value.
When transforming to Core Erlang, the named fun Fun is changed into
the following expression:
letrec 'Fun'/Arity =
fun (Args) ->
let <Fun> = 'Fun'/Arity
in Case
in 'Fun'/Arity
where Args is the list of arguments of 'Fun'/Arity and Case the
Core Erlang expression corresponding to the clauses of Fun.
This transformation allows us to entirely skip any k_var to k_local
transformation in the fun's clauses bodies.
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A bug has been fixed: when given the option {encoding,utf8} a list of
floating point numbers (in the correct interval) was mistakenly
returned as a string.
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The type erl_parse:token() used to be a two-tuple, but it can also be
a three-tuple.
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Expect modifications, additions and corrections.
There is a kludge in file_io_server and
erl_scan:continuation_location() that's not so pleasing.
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Currently, the external fun syntax "fun M:F/A" only supports
literals. That is, "fun lists:reverse/1" is allowed but not
"fun M:F/A".
In many real-life situations, some or all of M, F, A are
not known until run-time, and one is forced to either use
the undocumented erlang:make_fun/3 BIF or to use a
"tuple fun" (which is deprecated).
EEP-23 suggests that the parser (erl_parse) should immediately
transform "fun M:F/A" to "erlang:make_fun(M, F, A)". We have
not followed that approach in this implementation, because we
want the abstract code to mirror the source code as closely
as possible, and we also consider erlang:make_fun/3 to
be an implementation detail that we might want to remove in
the future.
Instead, we will change the abstract format for "fun M:F/A" (in a way
that is not backwards compatible), and while we are at it, we will
move the translation from "fun M:F/A" to "erlang:make_fun(M, F, A)"
from sys_pre_expand down to the v3_core pass. We will also update
the debugger and xref to use the new format.
We did consider making the abstract format backward compatible if
no variables were used in the fun, but decided against it. Keeping
it backward compatible would mean that there would be different
abstract formats for the no-variable and variable case, and tools
would have to handle both formats, probably forever.
Reference: http://www.erlang.org/eeps/eep-0023.html
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Behaviours may define specs for their callbacks using the familiar spec syntax,
replacing the '-spec' keyword with '-callback'. Simple lint checks are performed
to ensure that no callbacks are defined twice and all types referred are
declared.
These attributes can be then used by tools to provide documentation to the
behaviour or find discrepancies in the callback definitions in the callback
module.
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The default value 'undefined' was added to records field types in such
a way that the result was not always a well-formed type. This bug has
been fixed.
---
erl_pp has since OTP-8150 formatted types so that 'undefined' was
removed from union types assigned to record fields. Since one cannot
distinguish between 'undefined' added by the parser or supplied by the
user, a side effect was that user supplied 'undefined's were also
removed.
Now the pretty printer shows 'undefined' even if added by the parser.
This is a minor issue.
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Expressions evaluating to integers can now be used in types and function
specifications where hitherto only integers were allowed
("Erlang_Integer").
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The Erlang scanner has been augmented with two new tokens: .. and ....
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Original patch from YAMASHINA Hio posted to erlang-patches@
on Tue Jun 12 11:27:53 CEST 2007:
http://www.erlang.org/pipermail/erlang-patches/2007-June/000182.html
http://fleur.hio.jp/pub/erlang/record2.patch
Only had to do minor changes to port the patch to the
current R14A development tree.
Also added compiler/record_SUITE:nested_access/2 to test
nested record access with or without parentheses.
With this change the following will work.
-record(nrec0, {name = <<"nested0">>}).
-record(nrec1, {name = <<"nested1">>, nrec0=#nrec0{}}).
-record(nrec2, {name = <<"nested2">>, nrec1=#nrec1{}}).
nested_access() ->
N0 = #nrec0{},
N1 = #nrec1{},
N2 = #nrec2{},
<<"nested0">> = N0#nrec0.name,
<<"nested1">> = N1#nrec1.name,
<<"nested2">> = N2#nrec2.name,
<<"nested0">> = N1#nrec1.nrec0#nrec0.name,
<<"nested0">> = N2#nrec2.nrec1#nrec1.nrec0#nrec0.name,
<<"nested1">> = N2#nrec2.nrec1#nrec1.name,
<<"nested0">> = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0.name,
N1a = N2#nrec2.nrec1#nrec1{name = <<"nested1a">>},
<<"nested1a">> = N1a#nrec1.name,
N2a = N2#nrec2.nrec1#nrec1.nrec0#nrec0{name = <<"nested0a">>},
N2b = ((N2#nrec2.nrec1)#nrec1.nrec0)#nrec0{name = <<"nested0a">>},
<<"nested0a">> = N2a#nrec0.name,
N2a = N2b,
ok.
Signed-off-by: Tuncer Ayaz <[email protected]>
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The function erl_scan:reserved_word/1 no longer returns true when given the
word spec. This bug was introduced in STDLIB-1.15.3 (R12B-3).
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Unfortunately, commit 1e2ecf8c492b6d499880b8676e3c1fe0c5793103
removed all cond support except for two lines.
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The Erlang parser no longer duplicates the singleton type undefined in the
type of record fields without initial value.
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'cond' is an experimental feature that was never completed.
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