Revert "Restore the CachedIterator role"

This reverts commit dfae760.

Alas, not enough time to check this out before the 2021.4 release.
Better luck for the 2021.5 release I hope.

src/core.c/Iterator.pm6

@@ -129,12 +129,4 @@ my role PredictiveIterator does Iterator {
     method bool-only(--> Bool:D) { self.count-only.Bool }
 }
 
-# The CachedIterator role is a refinement of the PredictiveIterator role for
-# those cases where the source of the iterator is a Positional structure that
-# supports the AT-POS interface.  With such a structure, there is no need to
-# build a separate cache for the PositionalBindFailover functionality.
-my role CachedIterator does PredictiveIterator {
-    method cache(--> Positional:D) { ... }
-}
-
 # vim: expandtab shiftwidth=4

src/core.c/Rakudo/Iterator.pm6

@@ -1702,18 +1702,13 @@ class Rakudo::Iterator {
 
     # Returns a sentinel Iterator object that will never generate any value.
     # Does not take a parameter.
-    my class Empty does CachedIterator {
+    my class Empty does PredictiveIterator {
         method new() { nqp::create(self) }
         method pull-one(--> IterationEnd)  { }
         method push-all($ --> IterationEnd) { }
         method sink-all(--> IterationEnd)  { }
         method skip-one(--> 0) { }
         method skip-at-least($ --> 0) { }
-        method cache() {
-            BEGIN nqp::p6bindattrinvres(
-              nqp::create(List),List,'$!reified',nqp::create(IterationBuffer)
-            )
-        }
         method count-only(--> 0) { }
         method bool-only(--> False) { }
     }
@@ -3300,7 +3295,7 @@ class Rakudo::Iterator {
     # Return an iterator for an Array that has been completely reified
     # already.  Returns a assignable container for elements don't exist
     # before the end of the reified array.
-    my class ReifiedArrayIterator does CachedIterator {
+    my class ReifiedArrayIterator does PredictiveIterator {
         has $!reified;
         has $!descriptor;
         has int $!i;
@@ -3376,13 +3371,6 @@ class Rakudo::Iterator {
               )
             )
         }
-        method cache() is raw {
-            nqp::iseq_i($!i,-1)
-              ?? nqp::p6bindattrinvres(
-                   nqp::create(List),List,'$!reified',$!reified
-                 )
-              !! List.from-iterator(self)
-        }
         method count-only(--> Int:D) {
             nqp::elems($!reified) - $!i - nqp::islt_i($!i,nqp::elems($!reified))
         }
@@ -3395,7 +3383,7 @@ class Rakudo::Iterator {
     # Return an iterator for a List that has been completely reified
     # already.  Returns an nqp::null for elements that don't exist
     # before the end of the reified list.
-    my class ReifiedListIterator does CachedIterator {
+    my class ReifiedListIterator does PredictiveIterator {
         has $!reified;
         has int $!i;
 
@@ -3464,13 +3452,6 @@ class Rakudo::Iterator {
               )
             )
         }
-        method cache() is raw {
-            nqp::iseq_i($!i,-1)
-              ?? nqp::p6bindattrinvres(
-                   nqp::create(List),List,'$!reified',$!reified
-                 )
-              !! List.from-iterator(self)
-        }
         method count-only(--> Int:D) {
             nqp::elems($!reified) - $!i - nqp::islt_i($!i,nqp::elems($!reified))
         }

src/core.c/Seq.pm6

@@ -11,10 +11,6 @@ my class Seq is Cool does Iterable does Sequence {
     multi method new(Seq: Iterator:D $iter) {
         nqp::p6bindattrinvres(nqp::create(self),Seq,'$!iter',nqp::decont($iter))
     }
-    # Special handling for CachedIterators, setting the cache up immediately
-    multi method new(Seq: CachedIterator:D $iter) {
-        nqp::p6bindattrinvres(nqp::create(self),Seq,'$!list',$iter.cache)
-    }
     # This candidate exists purely for being able to EVAL a .raku
     # representation of a Seq of which the iterator has already been taken,
     multi method new(Seq:) { nqp::create(self) }

t/02-rakudo/03-corekeys-6c.t

@@ -501,7 +501,6 @@ my @expected = (
   Q{Broken},
   Q{Buf},
   Q{CX},
-  Q{CachedIterator},
   Q{CallFrame},
   Q{Callable},
   Q{Cancellation},

t/02-rakudo/03-corekeys-6d.t

@@ -501,7 +501,6 @@ my @expected = (
     Q{Broken},
     Q{Buf},
     Q{CX},
-    Q{CachedIterator},
     Q{CallFrame},
     Q{Callable},
     Q{Cancellation},

t/02-rakudo/03-corekeys-6e.t

@@ -503,7 +503,6 @@ my @expected = (
     Q{Broken},
     Q{Buf},
     Q{CX},
-    Q{CachedIterator},
     Q{CallFrame},
     Q{Callable},
     Q{Cancellation},

t/02-rakudo/03-corekeys.t

@@ -504,7 +504,6 @@ my @allowed =
       Q{Broken},
       Q{Buf},
       Q{CX},
-      Q{CachedIterator},
       Q{CallFrame},
       Q{Callable},
       Q{Cancellation},

t/02-rakudo/04-settingkeys-6c.t

@@ -501,7 +501,6 @@ my %allowed = (
     Q{Buf},
     Q{CORE-SETTING-REV},
     Q{CX},
-    Q{CachedIterator},
     Q{CallFrame},
     Q{Callable},
     Q{Cancellation},

t/02-rakudo/04-settingkeys-6e.t

@@ -501,7 +501,6 @@ my %allowed = (
     Q{Buf},
     Q{CORE-SETTING-REV},
     Q{CX},
-    Q{CachedIterator},
     Q{CallFrame},
     Q{Callable},
     Q{Cancellation},