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author | Edward Z. Yang <ezyang@cs.stanford.edu> | 2017-02-10 00:38:34 -0800 |
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committer | Edward Z. Yang <ezyang@cs.stanford.edu> | 2017-02-26 16:03:13 -0800 |
commit | 923d7ca2d90c1cb9816d14768abdd2e46adcd5dd (patch) | |
tree | 943e3c0dfff8e9674bbd6252b98101e713d47e3e /testsuite/tests/backpack/should_compile/T13140.stderr | |
parent | 9603de6ac7a75ea7c620ce05e3c5f500bcaf5dd6 (diff) | |
download | haskell-923d7ca2d90c1cb9816d14768abdd2e46adcd5dd.tar.gz |
Subtyping for roles in signatures.
Summary:
This commit implements the plan in #13140:
* Today, roles in signature files default to representational. Let's change the
default to nominal, as this is the most flexible implementation side. If a
client of the signature needs to coerce with a type, the signature can be
adjusted to have more stringent requirements.
* If a parameter is declared as nominal in a signature, it can be implemented
by a data type which is actually representational.
* When merging abstract data declarations, we take the smallest role for every
parameter. The roles are considered fix once we specify the structure of an
ADT.
* Critically, abstract types are NOT injective, so we aren't allowed to
make inferences like "if T a ~R T b, then a ~N b" based on the nominal
role of a parameter in an abstract type (this would be unsound if the
parameter ended up being phantom.) This restriction is similar to the
restriction we have on newtypes.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
Test Plan: validate
Reviewers: simonpj, bgamari, austin, goldfire
Subscribers: goldfire, thomie
Differential Revision: https://phabricator.haskell.org/D3123
Diffstat (limited to 'testsuite/tests/backpack/should_compile/T13140.stderr')
-rw-r--r-- | testsuite/tests/backpack/should_compile/T13140.stderr | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/testsuite/tests/backpack/should_compile/T13140.stderr b/testsuite/tests/backpack/should_compile/T13140.stderr new file mode 100644 index 0000000000..c40b6bc1df --- /dev/null +++ b/testsuite/tests/backpack/should_compile/T13140.stderr @@ -0,0 +1,28 @@ +[1 of 7] Processing p + [1 of 1] Compiling A[sig] ( p/A.hsig, nothing ) +[2 of 7] Processing q1 + Instantiating q1 + [1 of 1] Compiling A ( q1/A.hs, T13140.out/q1/A.o ) +[3 of 7] Processing q2 + Instantiating q2 + [1 of 1] Compiling A ( q2/A.hs, T13140.out/q2/A.o ) +[4 of 7] Processing q3 + Instantiating q3 + [1 of 1] Compiling A ( q3/A.hs, T13140.out/q3/A.o ) +[5 of 7] Processing r + Instantiating r + [1 of 3] Including p[A=q1:A] + Instantiating p[A=q1:A] + [1 of 1] Compiling A[sig] ( p/A.hsig, T13140.out/p/p-BwqqugG2ETwLIwrPGPdl6W/A.o ) + [2 of 3] Including p[A=q2:A] + Instantiating p[A=q2:A] + [1 of 1] Compiling A[sig] ( p/A.hsig, T13140.out/p/p-KZH5iDezOjj6YVcfuBlAG2/A.o ) + [3 of 3] Including p[A=q3:A] + Instantiating p[A=q3:A] + [1 of 1] Compiling A[sig] ( p/A.hsig, T13140.out/p/p-200ijkYDy133WhdgYYHZ24/A.o ) +[6 of 7] Processing p2 + [1 of 2] Compiling A[sig] ( p2/A.hsig, nothing ) + [2 of 2] Compiling M ( p2/M.hs, nothing ) +[7 of 7] Processing p3 + [1 of 2] Compiling A[sig] ( p3/A.hsig, nothing ) + [2 of 2] Compiling M2 ( p3/M2.hs, nothing ) |