dialyzer: Unfold cerl patterns containing maps

Dialyzer relies heavily on the assumption that the type of a literal
that is used as a pattern is the type of any value that can match that
pattern. For maps, that is not true, and it was causing bad analysis
results. A new help function dialyzer_utils:refold_pattern/1 identifies
maps in literal patterns, and unfolds and labels them, allowing them to
be properly analysed.

1 files changed, 1 insertions, 3 deletions

diff --git a/lib/dialyzer/test/map_SUITE_data/results/typeflow2 b/lib/dialyzer/test/map_SUITE_data/results/typeflow2
index aa47845fb1..3bce165275 100644
--- a/lib/dialyzer/test/map_SUITE_data/results/typeflow2
+++ b/lib/dialyzer/test/map_SUITE_data/results/typeflow2
@@ -5,11 +5,9 @@ typeflow2.erl:26: Function t2/1 has no local return
 typeflow2.erl:29: The call lists:sort(integer()) will never return since it differs in the 1st argument from the success typing arguments: ([any()])
 typeflow2.erl:42: The pattern ~{'a':=X}~ can never match since previous clauses completely covered the type #{'a':=integer()}
 typeflow2.erl:43: The variable _ can never match since previous clauses completely covered the type #{'a':=integer()}
-typeflow2.erl:48: The pattern ~{}~ can never match the type #{'a':=atom() | maybe_improper_list() | integer()}
+typeflow2.erl:48: The pattern ~{}~ can never match since previous clauses completely covered the type #{'a':=atom() | maybe_improper_list() | integer()}
 typeflow2.erl:58: The pattern ~{'a':=X}~ can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
 typeflow2.erl:59: The pattern ~{'a':=X}~ can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
 typeflow2.erl:60: The pattern ~{'a':=X}~ can never match the type #{'a'=>none(), _=>maybe_improper_list() | integer()}
-typeflow2.erl:80: The pattern ~{'a':=X}~ can never match the type #{}
-typeflow2.erl:81: The pattern ~{'a':=X}~ can never match the type #{}
 typeflow2.erl:82: The pattern ~{'a':=X}~ can never match the type #{}
 typeflow2.erl:83: The pattern ~{'a':=X}~ can never match the type #{}