compiler.tree.propagation.transforms: fix problem with 'shift' transform when input was a bignum

basis/compiler/tests/optimizer.factor

@@ -443,5 +443,7 @@ M: object bad-dispatch-position-test* ;
 [ -1 ] [ 3 4 0 dispatch-branch-problem ] unit-test
 [ 12 ] [ 3 4 1 dispatch-branch-problem ] unit-test
 
+[ 1024 bignum ] [ 10 [ 1 >bignum swap >fixnum shift ] compile-call dup class ] unit-test
+
 ! Not sure if I want to fix this...
 ! [ t [ [ f ] [ 3 ] if >fixnum ] compile-call ] [ no-method? ] must-fail-with

basis/compiler/tree/propagation/transforms/transforms.factor

@@ -100,8 +100,12 @@ IN: compiler.tree.propagation.transforms
 ] each
 
 ! Speeds up 2^
+: 2^? ( #call -- ? )
+    in-d>> first value-info
+    { [ literal>> 1 = ] [ class>> fixnum class<= ] } 1&& ;
+
 \ shift [
-    in-d>> first value-info literal>> 1 = [
+     2^? [
         cell-bits tag-bits get - 1 -
         '[
             >fixnum dup 0 < [ 2drop 0 ] [