Bug fixes and improvements of dialyzer_typesig

1. Sometimes the solver forgot that a list had entered the error
   state. The bug has been fixed by storing the atom 'error' in
   MapDict. An example where the bug occurred is
   io_lib_pretty:printable_bin(). The returned spec was weaker than it
   should have been, but the fix-point loop hid the bug (in this case).

2. lists:partition() has been substituted for lists:splitwith() in
   enumerate_constraints(). This fix together with 3. solves a
   problem with long execution times for deeply nested fun:s. An
   example which is now much faster is
   lib/compiler/test/lc_SUITE:deeply_nested/1
   (included as dialyzer/test/small_SUITE_data/src/deep_lc.erl).

3. The calculation of components in enumerate_constraints() has been
   simplified and optimized. The important thing here is that _all_ of
   the simple constraints have been saturated before entering the
   complex part.

4. The pretty printing of constraints has been improved.

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/dialyzer/test/small_SUITE_data/src/deep_lc.erl b/lib/dialyzer/test/small_SUITE_data/src/deep_lc.erl
new file mode 100644
index 0000000000..d9ca0817d9
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/deep_lc.erl
@@ -0,0 +1,14 @@
+-module(deep_lc).
+
+-export([t/0]).
+
+%% This is compile/test/lc_SUITE:deeply_nested/1
+%%
+%% Used to be _very_ slow. Unknown how slow, but more than 15 hours.
+
+t() ->
+    [[X1,X2,X3,X4,X5,X6,X7(),X8,X9,X10,X11,X12,X13,X14,X15,X16,X17,X18(),X19,X20] ||
+        X1 <- [99],X2 <- [98],X3 <- [97],X4 <- [96],X5 <- [42],X6 <- [17],
+	X7 <- [fun() -> X5*X5 end],X8 <- [12],X9 <- [11],X10 <- [10],
+        X11 <- [9],X12 <- [8],X13 <- [7],X14 <- [6],X15 <- [5],
+	X16 <- [4],X17 <- [3],X18 <- [fun() -> X16+X17 end],X19 <- [2],X20 <- [1]].