Simplify Iterable eqv Iterable

By removing the specific Positional handling.  This every so lightly
improves performance on comparing arrays, while not affecting any
other performance.

This also removes the use of AT-POS in eqv handling, making it easier
to later introduce proper eqv handling of sparse arrays.

src/core.c/Iterable.pm6

@@ -110,51 +110,31 @@ multi sub infix:<eqv>(Iterable:D \a, Iterable:D \b) {
         nqp::if(                                 # not same object
           nqp::eqaddr(a.WHAT,b.WHAT),
           nqp::if(                               # same type
-            nqp::istype(a, Positional),
-            nqp::if(                             # Positional
-              a.is-lazy,
-              nqp::if(                           # a lazy
-                b.is-lazy,
-                Any.throw-iterator-cannot-be-lazy('eqv','') # a && b lazy
-              ),
-              nqp::if(                           # a NOT lazy
-                b.is-lazy,
-                0,                               # b lazy
-                nqp::if(                         # a && b NOT lazy
-                  nqp::iseq_i((my int $elems = a.elems),b.elems),
-                  nqp::stmts(                    # same # elems
-                    (my int $i = -1),
-                    nqp::while(
-                      nqp::islt_i(($i = nqp::add_i($i,1)),$elems) # not exhausted
-                        && a.AT-POS($i) eqv b.AT-POS($i),         # still same
-                      nqp::null
-                    ),
-                    nqp::iseq_i($i,$elems)       # exhausted = success!
-                  )
-                )
-              )
+            nqp::iseq_i(
+              nqp::istrue(my \ial := (my \ia := a.iterator).is-lazy),
+              nqp::istrue(           (my \ib := b.iterator).is-lazy)
             ),
-            nqp::if(                             # NOT Positional
-              nqp::iseq_i(
-                (my \ia := a.iterator).is-lazy,
-                (my \ib := b.iterator).is-lazy
-              ),
-              nqp::if(
-                ia.is-lazy,
-                Any.throw-iterator-cannot-be-lazy('eqv',''),
-                nqp::stmts(
-                  nqp::until(
-                    nqp::stmts(
-                      (my \pa := ia.pull-one),
-                      (my \pb := ib.pull-one),
-                      nqp::eqaddr(pa,IterationEnd)
-                        || nqp::eqaddr(pb,IterationEnd)
-                        || nqp::not_i(pa eqv pb)
-                    ),
-                    nqp::null
+            nqp::if(
+              ial,
+              Any.throw-iterator-cannot-be-lazy('eqv',''),
+              nqp::stmts(
+                nqp::if(
+                  nqp::istype(ia,PredictiveIterator)
+                    && nqp::istype(ib,PredictiveIterator)
+                    && nqp::isne_i(ia.count-only,ib.count-only),
+                  (return False)
+                ),
+                nqp::until(
+                  nqp::stmts(
+                    (my \pa := ia.pull-one),
+                    (my \pb := ib.pull-one),
+                    nqp::eqaddr(pa,IterationEnd)
+                      || nqp::eqaddr(pb,IterationEnd)
+                      || nqp::isfalse(pa eqv pb)
                   ),
-                  nqp::eqaddr(pa,pb)     # both IterationEnd = success!
-                )
+                  nqp::null
+                ),
+                nqp::eqaddr(pa,pb)     # both IterationEnd = success!
               )
             )
           )