0004182: 'exception Exc of (string * string)' and 'exception Exc of string * string' not necessarily the same

Notes
(0003874) Colas (reporter) 2006-12-13 18:08	* has precedence, thus exception Exc of string * string is (exception Exc of string) * string whichi is different from exception Exc of (string * string)

(0003875) garrigue (manager) 2006-12-14 01:20	exception E of string * string and exception E of (string * string) have different internal representations, so they are incompatible. This is also true for types! module M : sig type t = E of (string * string) end = struct type t = E of string * string end;; Type declarations do not match: type t = E of string * string is not included in type t = E of (string * string) All this is documented in the reference manual.

(0003876) cookedm (reporter) 2006-12-14 02:05	Responding to Colas: If `exception Exc of string * string` is equal to `(exception Exc of string) * string`, then `Exc ("a","b")` should be a type error. Which it isn't. `((Exc "a"), "b")` is, though. Responding to garrigue: The reference manual, 6.4 Type Expressions -> Parenthesized types, says: The type expression ( typexpr ) denotes the same type as typexpr I thought that was pretty clear :-) The other problem is that the output produced by ocaml is the same for both ways. Using types: # type t1 = E1 of string * string;; type t1 = E1 of string * string # type t2 = E2 of (string * string);; type t2 = E2 of (string * string) # E1 ("a", "b");; - : t1 = E1 ("a", "b") # E2 ("a", "b");; - : t2 = E2 ("a", "b") so the pretty-printed version of the two values is identical. Either: 1) E of string * string and E of (string * string) should be identical 2) or, they're different, and should act differently. For instance, E of string * string should be (E of string) * string (which isn't a valid type expression).

(0003878) oandrieu (reporter) 2006-12-14 09:57	cookedm: there is a difference between a constructor with one tuple argument (declared by "E of (string * string)" and a constructor with multiple arguments "E of string * string". The revised syntax of camlp4 makes this distinction way more clear by using a different keyword for the multiple arguments case: type t = [ E of (string * string) ] vs. type t = [ E of string and string ] But I'm not sure where this is documented in the reference manual. Section 6.8.1, "Type definitions" says: "The constructor declaration constr-name of typexpr declares the name constr-name as a non-constant constructor, whose argument has type typexpr." It doesn't explain anything about constructors with multiple arguments.

(0003887) doligez (manager) 2006-12-18 14:59	> Hardly a major bug, but it is surprising, as typexpr and (typexpr) should be equivalent. In fact, it's a bug in the documentation. typexpr and (typexpr) are indeed equivalent, but in "Exc of string * string", "string * string" is not parsed as a typexpr, it's two typexprs separated by a "*" which is part of the syntax of exception declarations. As oandrieu notes, this is made clear by the revised syntax. On the other hand, the documentation is currently misleading on this subject. The documentation will be fixed in 3.10.0.

Issue History
Date Modified	Username	Field	Change
2006-12-07 09:43	cookedm	New Issue
2006-12-13 18:08	Colas	Note Added: 0003874
2006-12-14 01:20	garrigue	Status	new => closed
2006-12-14 01:20	garrigue	Note Added: 0003875
2006-12-14 01:20	garrigue	Resolution	open => no change required
2006-12-14 02:05	cookedm	Status	closed => feedback
2006-12-14 02:05	cookedm	Resolution	no change required => reopened
2006-12-14 02:05	cookedm	Note Added: 0003876
2006-12-14 09:57	oandrieu	Note Added: 0003878
2006-12-18 14:59	doligez	Note Added: 0003887
2006-12-18 14:59	doligez	Status	feedback => closed
2006-12-18 14:59	doligez	Resolution	reopened => fixed
2006-12-18 14:59	doligez	Category	OCaml general => OCaml documentation
2006-12-18 14:59	doligez	Fixed in Version	=> 3.10+dev

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