dialyzer: Modify warning for comparison of opaque types

Comparing two operands for (in)equality is allowed if both operands
are of the same unknown opaque type. Since OTP 17, there is a warning
if the types of the operands have nothing in common (this cannot
happen before OTP 17). However, the warning says there is a test
between opaque types, which is wrong. The warning now states that the
comparison cannot evaluate to 'true', which is more consistent.

3 files changed, 73 insertions, 4 deletions

diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/para/para5.erl b/lib/dialyzer/test/opaque_SUITE_data/src/para/para5.erl
new file mode 100644
index 0000000000..76ea3e76b5
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/para/para5.erl
@@ -0,0 +1,33 @@
+-module(para5).
+
+-export([d/0, dd/0, da1/0]).
+
+d() ->
+    I1 = adt_d1(),
+    I2 = adt_d2(),
+    I1 =:= I2. % can never evaluate to true
+
+dd() ->
+    I1 = adt_d1(),
+    I2 = adt_dd(),
+    I1 =/= I2. % incompatible opaque types
+
+da1() ->
+    I1 = adt_da1(),
+    I2 = adt_da2(),
+    I1 =:= I2.
+
+adt_d1() ->
+    para5_adt:d1().
+
+adt_d2() ->
+    para5_adt:d2().
+
+adt_dd() ->
+    para5_adt:dd().
+
+adt_da1() ->
+    para5_adt:da1().
+
+adt_da2() ->
+    para5_adt:da2().
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/para/para5_adt.erl b/lib/dialyzer/test/opaque_SUITE_data/src/para/para5_adt.erl
new file mode 100644
index 0000000000..a62e0488e0
--- /dev/null
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/para/para5_adt.erl
@@ -0,0 +1,36 @@
+-module(para5_adt).
+
+-export([d1/0, d2/0, dd/0, da1/0, da2/0]).
+
+-export_type([d/0, dd/1, da/2]).
+
+-opaque d() :: 1 | 2.
+
+-spec d1() -> d().
+
+d1() ->
+    1.
+
+-spec d2() -> d().
+
+d2() ->
+    2.
+
+-opaque dd(A) :: A.
+
+-spec dd() -> dd(atom()).
+
+dd() ->
+    foo:atom().
+
+-opaque da(A, B) :: {A, B}.
+
+-spec da1() -> da(any(), atom()).
+
+da1() ->
+    {3, a}.
+
+-spec da2() -> da(integer(), any()).
+
+da2() ->
+    {3, a}.
diff --git a/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl
index eef2074e0c..7db1100597 100644
--- a/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl
+++ b/lib/dialyzer/test/opaque_SUITE_data/src/simple/simple1_api.erl
@@ -145,7 +145,7 @@ adt_t4() ->
     A = simple1_adt:n1(),
     B = simple1_adt:n2(),
     A = A, % OK
-    A = B. % opaque term
+    A = B. % opaque terms
 
 adt_t7() ->
     A = simple1_adt:n1(),
@@ -178,7 +178,7 @@ c2(A, B) ->
 c2() ->
     A = simple1_adt:d1(),
     B = simple1_adt:d2(),
-    if A =< B -> ok end. % opaque term
+    if A =< B -> ok end. % opaque terms
 
 c3() ->
     B = simple1_adt:d2(),
@@ -516,7 +516,7 @@ eq1() ->
     A = simple1_adt:d2(),
     B = simple1_adt:d1(),
     if
-        A == B -> % opaque term
+        A == B -> % opaque terms
             0;
         A == A ->
             1;
@@ -555,7 +555,7 @@ c6(A, B) ->
 c7(A, B) ->
     A = simple1_adt:d1(),
     B = simple1_adt:d2(),
-    A =< B. % opaque term
+    A =< B. % opaque terms
 
 c8() ->
     D = digraph:new(),