erl_types: Add a map type representation

The type of a map is represented as a three-tuple {Pairs, DefaultKey,
DefaultValue}. DefaultKey and DefaultValue are types. Pairs is a list of
three-tuples {Key, mandatory | optional, Value}, where Key and Value are
types. All types Key must be singleton, or "known at compile time," as
the EEP put it. Examples:

    #{integer()=>list()}       {[], integer(), list()}
    #{a=>char(), b=>atom()}    {[{a, optional, char()},
                                 {b, optional, atom()}],
                                none(), none()}
    map()                      {[], any(), any()}

A more formal description of the representation and its invariants can
be found in erl_types.erl

Special thanks to Daniel S. McCain (@dsmccain) that co-authored a very
early version of this with me back in April 2014, although only the
singleton type logic remains from that version.

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/dialyzer/test/small_SUITE_data/results/maps1 b/lib/dialyzer/test/small_SUITE_data/results/maps1
index e88c91f21f..773f037c47 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/maps1
+++ b/lib/dialyzer/test/small_SUITE_data/results/maps1
@@ -1,4 +1,8 @@
 
+maps1.erl:20: Function recv/3 has no local return
+maps1.erl:25: Function decode/1 has no local return
+maps1.erl:31: Function t1/0 has no local return
+maps1.erl:40: Function update/2 has no local return
 maps1.erl:43: Function t3/0 has no local return
-maps1.erl:44: The call maps1:foo(~{'greger'=>3, ~{'arne'=>'anka'}~=>45}~,1) will never return since it differs in the 2nd argument from the success typing arguments: (#{},'b')
+maps1.erl:46: Function foo/2 has no local return
 maps1.erl:52: The call Mod:'function'(~{'literal'=>'map'}~,'another_arg') requires that Mod is of type atom() not #{}