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authorJoey Hess2016-03-08 17:54:49 -0400
committerJoey Hess2016-03-08 17:54:49 -0400
commit61a1ba8ff1fa496af24d22986057a7607ae55ff1 (patch)
treea8ceb1621f4f2cf74892bcec2977dc72135df851 /doc
parent4dab5fd328fc04ed006f32014330dac2621f0385 (diff)
make it a type error to intersect two OS lists if the result is empty
Diffstat (limited to 'doc')
-rw-r--r--doc/todo/type_level_OS_requirements.mdwn4
1 files changed, 3 insertions, 1 deletions
diff --git a/doc/todo/type_level_OS_requirements.mdwn b/doc/todo/type_level_OS_requirements.mdwn
index 65e6099f..6d5d7aaf 100644
--- a/doc/todo/type_level_OS_requirements.mdwn
+++ b/doc/todo/type_level_OS_requirements.mdwn
@@ -11,7 +11,9 @@ For example, `Property i '[Debian, FreeBSD]` combined with `Property i '[Debian,
yields a `Property i '[Debian]` -- the intersection of the OS's supported by
the combined properties.
-And, combining two properties that demand different OS's would need to be a
+Combining two properties that demand different OS's would yield a
+`Property i '[]` -- since the type level OS list is empty,
+
type error. Can a type level function combine two types successfully, and
fail to combine two others somehow? Don't know. Maybe combine to an
IncoherentOS and don't allow a `Property i IncoherentOS` to be used in a