| Age | Commit message (Collapse) | Author |
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Suggested by Kostis.
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Messages like "Invalid type specification for function
para3:exp_adt/0. The success typing is () -> 3" now look like
"The specification for para3:exp_adt/0 has an opaque subtype
para3_adt:exp1(para3_adt:exp2()) which is violated by the success
typing () -> 3".
The old message did not give any clue as to what invalidated the
contract, namely the opaque subtype.
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Messages like "The attempt to match a term of type rec_api:f()
against the variable _ breaks the opaqueness of rec_adt:f()" now
look like "The attempt to match a term of type rec_adt:f()
against the record field 'f' with type rec_api:f() breaks the
opaqueness of the term".
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Parameterized modules are no longer supported, so module() can only be
an atom().
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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
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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
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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
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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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Comparing two operands for (in)equality is allowed if both operands
are of the same unknown opaque type. Since OTP 17, there is a warning
if the types of the operands have nothing in common (this cannot
happen before OTP 17). However, the warning says there is a test
between opaque types, which is wrong. The warning now states that the
comparison cannot evaluate to 'true', which is more consistent.
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This ticket is about records in Erlang code, and when to check the
fields against the (optional) types given when defining records.
Dialyzer operates on the Erlang Core format, where there are no trace
of records. The fix implemented is a Real Hack:
Given the new option 'dialyzer' erl_expand_records marks the line
number of records in a way that is undone by v3_core, which in turn
inserts annotations that can be recognized by Dialyzer.
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The types array(), dict(), digraph(), gb_set(), gb_tree(), queue(),
set(), and tid() have been deprecated. They will be removed in OTP 18.0.
Instead the types array:array(), dict:dict(), digraph:graph(),
gb_set:set(), gb_tree:tree(), queue:queue(), sets:set(), and ets:tid()
can be used. (Note: it has always been necessary to use ets:tid().)
It is allowed in OTP 17.0 to locally re-define the types array(), dict(),
and so on.
New types array:array/1, dict:dict/2, gb_sets:set/1, gb_trees:tree/2,
queue:queue/1, and sets:set/1 have been added.
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It is now OK to inspect and modify the internals of opaque types within
the scope of the module.
The contracts are used for decorating types with opaqueness when it is
harmless to do so. The opaqueness is propagated by the typesig module
and also by the dataflow module.
A lot of details have been fixed or updated. In particular the modules
erl_types and erl_bif_types have been modified extensively.
The version in vsn.mk has been updated to 2.7. The reason is a
modification of #opaque{} in erl_types.
Dialyzer seems to be about five percent slower than it used to be.
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