Change typedesc:constructFrom to value:cloneWithType

Fixes #471.
Changing return type will be done in #426 and #386.

lang/lib/typedesc.bal

@@ -13,37 +13,3 @@
 // KIND, either express or implied.  See the License for the
 // specific language governing permissions and limitations
 // under the License.
-
-# A type parameter that is a subtype of `anydata`.
-# Has the special semantic that when used in a declaration
-# all uses in the declaration must refer to same type. 
-@typeParam
-type AnydataType anydata;
-
-# Constructs a value with a specified type by copying another value.
-# + t - the type for the copy to be constructed
-# + v - the value to be copied
-# + return - a new value that belongs to type `t`, or an error if this cannot be done
-# 
-# When `v` is a structural value, the inherent type of the value to be constructed
-# comes from `t`. When `t` is a union, it must be possible to determine which
-# member of the union to use for the inherent type by following the same rules
-# that are used by list constructor expressions and mapping constructor expressions
-# with the contextually expected type. If not, then an error is returned.
-# The `constructFrom` operation is recursively applied to each member of `v` using
-# the type descriptor that the inherent type requires for that member.
-# 
-# Like the Clone abstract operation, this does a deep copy, but differs in
-# the following respects:
-# - the inherent type of any structural values constructed comes from the specified
-#   type descriptor rather than the value being constructed
-# - the read-only bit of values and fields comes from the specified type descriptor
-# - the graph structure of `v` is not preserved; the result will always be a tree;
-#   an error will be returned if `v` has cycles
-# - immutable structural values are copied rather being returned as is; all
-#   structural values in the result will be mutable, except for error values
-#   (which are always immutable)
-# - numeric values can be converted using the NumericConvert abstract operation
-# - if a record type descriptor specifies default values, these will be used
-#   to supply any missing members
-public function constructFrom(typedesc<AnydataType> t, anydata v) returns AnydataType|error = external;

lang/lib/value.bal

@@ -45,6 +45,34 @@ public function clone(CloneableType v) returns CloneableType = external;
 # + return - immutable clone of `v`
 public function cloneReadOnly(CloneableType v) returns CloneableType = external;
 
+# Constructs a value with a specified type by cloning another value.
+# + v - the value to be cloned
+# + t - the type for the cloned to be constructed
+# + return - a new value that belongs to type `t`, or an error if this cannot be done
+# 
+# When `v` is a structural value, the inherent type of the value to be constructed
+# comes from `t`. When `t` is a union, it must be possible to determine which
+# member of the union to use for the inherent type by following the same rules
+# that are used by list constructor expressions and mapping constructor expressions
+# with the contextually expected type. If not, then an error is returned.
+# The `constructFrom` operation is recursively applied to each member of `v` using
+# the type descriptor that the inherent type requires for that member.
+# 
+# Like the Clone abstract operation, this does a deep copy, but differs in
+# the following respects:
+# - the inherent type of any structural values constructed comes from the specified
+#   type descriptor rather than the value being constructed
+# - the read-only bit of values and fields comes from the specified type descriptor
+# - the graph structure of `v` is not preserved; the result will always be a tree;
+#   an error will be returned if `v` has cycles
+# - immutable structural values are copied rather being returned as is; all
+#   structural values in the result will be mutable, except for error values
+#   (which are always immutable)
+# - numeric values can be converted using the NumericConvert abstract operation
+# - if a record type descriptor specifies default values, these will be used
+#   to supply any missing members
+public function cloneWithType(anydata v, typedesc<AnydataType> t) returns AnydataType|error = external;
+
 # Tests whether `v` is read-only, i.e. immutable
 # Returns true if read-only, false otherwise.
 #