Remove _validateFor.

Refs #222.

dump.py

@@ -24,7 +24,7 @@ def dumpLines(s):
     u"Void", u"Bool", u"Bytes", u"Char", u"Double", u"Int", u"Str",
     u"_makeOrderedSpace", u"Empty", u"List", u"Map", u"NullOk", u"Pair",
     u"Set", u"Vow", u"_mapEmpty", u"_mapExtract", u"_accumulateList",
-    u"_accumulateMap", u"_booleanFlow", u"_iterForever", u"_validateFor",
+    u"_accumulateMap", u"_booleanFlow", u"_iterForever",
     u"_switchFailed", u"_makeVerbFacet", u"_comparer", u"_suchThat",
     u"_matchSame", u"_bind", u"_quasiMatcher", u"_splitList", u"import",
     u"typhonEval", u"makeLazySlot", u"astBuilder", u"simple__quasiParser",

mast/lib/monte/monte_expander.mt

@@ -488,14 +488,10 @@ def expand(node, builder, fail) as DeepFrozen:
         validateFor(sw.getStaticScope(key) + sw.getStaticScope(value),
                     sw.getStaticScope(coll), fail, span)
         # `key` and `value` are patterns. We cannot permit any code to run
-        # within the loop until we've done _validateFor(), which normally
-        # means that we use temp nouns and postpone actually unifying the key
-        # and value until afterwards. This is a bit of a waste of time,
-        # especially in very tight loops, and none of our optimizers can
-        # improve it since it's (ironically) unsafe to move any defs around
-        # the _validateFor() call! So, instead, we're considering whether the
-        # patterns can be refuted. If a pattern is irrefutable, then we'll
-        # unify it directly in the method's parameters. ~ C.
+        # within the loop until we've match-bound these patterns. So, instead,
+        # we're considering whether the patterns can be refuted. If a pattern
+        # is irrefutable, then we'll unify it directly in the method's
+        # parameters, generating slightly tighter code. ~ C.
         def [patts, defs] := if (key.refutable()) {
             # The key is refutable, so we go with the traditional layout.
             def kTemp := tempNounExpr("key", span)

mast/prelude.mt

@@ -80,18 +80,6 @@ def Empty := makePredicateGuard(def pred(specimen) as DeepFrozenStamp {return sp
 # Alias for map patterns.
 def _mapEmpty := Empty
 
-
-# Must come before List. Must come after Void and Bool.
-def _validateFor(flag :Bool) :Void as DeepFrozenStamp:
-    "Ensure that `flag` is `true`.
-
-     This object is a safeguard against malicious loop objects. A flag is set
-     to `true` and closed over by a loop body; once the loop is finished, the
-     flag is set to `false` and the loop cannot be reëntered."
-
-    if (!flag):
-        throw("Failed to validate loop!")
-
 object _ListGuardStamp:
     to audit(audition):
         return true
@@ -810,7 +798,6 @@ def scopeNames := [
     => throw, => trace, => traceln,
     => _mapEmpty, => _mapExtract,
     => _accumulateList, => _accumulateMap, => _booleanFlow, => _iterForever,
-    => _validateFor,
     => _switchFailed, => _makeVerbFacet, => _comparer, => _suchThat,
     => _matchSame, => _bind, => _quasiMatcher, => _splitList,
     => M, => Ref,  => throw, => promiseAllFulfilled,