unstabilize == between unbounded and bounded ranges over enums and bo…

…ols and return true (chapel-lang#23036)

In Issue chapel-lang#20896  we have decided that `==` for unbounded ranges with finite Idxtypes (i.e. enums and bools) should behave as if those ranges were bounded since the represented sequence is the same in both cases.
This means for example
```chapel
writeln(false..==false..true); // unstable; print 'true'
writeln(false.. by -1 ==..true by -1); // unstable; print 'true'
```

[Reviewed by @vasslitvinov ]

modules/internal/ChapelRange.chpl

@@ -1496,9 +1496,28 @@ module ChapelRange {
 
   @chpldoc.nodoc
   operator ==(r1: range(?), r2: range(?)) param
-    where r1.bounds != r2.bounds do
+    where r1.bounds != r2.bounds &&
+          (!isFiniteIdxType(r1.idxType) ||
+          !isFiniteIdxType(r2.idxType)) do
   return false;
 
+  @chpldoc.nodoc
+  @unstable("== between unbounded and bounded ranges is unstable and its behavior may change in the future")
+  operator ==(r1: range(?), r2: range(?)): bool
+    where r1.bounds != r2.bounds && isFiniteIdxType(r1.idxType) &&
+          isFiniteIdxType(r2.idxType)
+  {
+    const boundedr1 = if r1.bounds == boundKind.both then r1
+                       else new range(
+                          r1.idxType, boundKind.both, r1.strides,
+                          r1._low, r1._high, r1._stride, r1._alignment);
+    const boundedr2 = if r2.bounds == boundKind.both then r2
+                        else new range(
+                            r2.idxType, boundKind.both, r2.strides,
+                            r2._low, r2._high, r2._stride, r2._alignment);
+    return boundedr1 == boundedr2;
+  }
+
   @chpldoc.nodoc
   operator ==(r1: range(?), r2: range(?)): bool
     where r1.bounds == r2.bounds
@@ -1571,7 +1590,7 @@ module ChapelRange {
   {
     if r1._low != r2._low then return false;
     if r1._high != r2._high then return false;
-    // the following can be 'if none == none ...'
+    // the following can be 'if none != none ...'
         if r1._stride != r2._stride then return false;
         if r1._alignment != r2._alignment then return false;
     return true;

test/types/range/unbounded/compareEnumBool.chpl

@@ -4,6 +4,9 @@ use color;
 var rgb = red..blue;
 var rdd = red..;
 var ddb = ..blue;
+var negrgb = red..blue by -1;
+var negrdd = red.. by -1;
+var negddb = ..blue by -1;
 var dd: range(color, boundKind.neither);
 
 writeln(rgb == rdd);
@@ -14,12 +17,19 @@ writeln(rdd == ddb);
 writeln(rdd == dd);
 
 writeln(ddb == dd);
-
+writeln(negrgb == negrdd);
+writeln(negrdd == negddb);
+writeln(negrdd == dd);
+writeln(rdd == negrdd);
+writeln(ddb == negddb);
 
 {
 var ft = false..true;
 var fdd = false..;
 var ddt = ..true;
+var negft = false..true by -1;
+var negfdd = false.. by -1;
+var negddt = ..true by -1;
 var dd: range(bool, boundKind.neither);
 
 writeln(ft == fdd);
@@ -30,4 +40,9 @@ writeln(fdd == ddt);
 writeln(fdd == dd);
 
 writeln(ddt == dd);
+writeln(negft == negfdd);
+writeln(negfdd == negddt);
+writeln(negfdd == dd);
+writeln(fdd == negfdd);
+writeln(ddt == negddt);
 }

test/types/range/unbounded/compareEnumBool.good

@@ -1,12 +1,22 @@
-false
-false
-false
-false
-false
-false
-false
-false
-false
+true
+true
+true
+true
+true
+true
+true
+true
+false
+false
+false
+true
+true
+true
+true
+true
+true
+true
+true
 false
 false
 false

test/unstable/compareRangeUnboundedEnumBool.chpl

@@ -0,0 +1,44 @@
+enum color {red, green, blue};
+use color;
+
+var rgb = red..blue;
+var rdd = red..;
+var ddb = ..blue;
+var negrgb = red..blue by -1;
+var negrdd = red.. by -1;
+var negddb = ..blue by -1;
+var dd: range(color, boundKind.neither);
+
+writeln(rgb == rdd);
+writeln(rgb == ddb);
+writeln(rgb == dd);
+
+writeln(rdd == ddb);
+writeln(rdd == dd);
+
+writeln(ddb == dd);
+writeln(negrgb == negrdd);
+writeln(negrdd == negddb);
+writeln(negrdd == dd);
+
+{
+var ft = false..true;
+var fdd = false..;
+var ddt = ..true;
+var negft = false..true by -1;
+var negfdd = false.. by -1;
+var negddt = ..true by -1;
+var dd: range(bool, boundKind.neither);
+
+writeln(ft == fdd);
+writeln(ft == ddt);
+writeln(ft == dd);
+
+writeln(fdd == ddt);
+writeln(fdd == dd);
+
+writeln(ddt == dd);
+writeln(negft == negfdd);
+writeln(negfdd == negddt);
+writeln(negfdd == dd);
+}

test/unstable/compareRangeUnboundedEnumBool.good

@@ -0,0 +1,36 @@
+compareRangeUnboundedEnumBool.chpl:12: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:13: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:14: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:16: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:17: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:19: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:20: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:21: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:22: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:33: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:34: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:35: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:37: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:38: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:40: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:41: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:42: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+compareRangeUnboundedEnumBool.chpl:43: warning: == between unbounded and bounded ranges is unstable and its behavior may change in the future
+true
+true
+true
+true
+true
+true
+true
+true
+false
+true
+true
+true
+true
+true
+true
+true
+true
+false