Move checkField to valueproof.go and rename checkPath to checkResolves

struct.go

@@ -317,37 +317,6 @@ func (k columnKind) holds(v proven) bool {
 	return v.lo >= k.lo && v.hi <= k.hi
 }
 
-// checkField rejects a column a field of Go type ft cannot fill: a datatype, which the Go type
-// sets, a null outside a pointer, or a value its kind's datatype or range refuses.
-func (p *valueProof) checkField(label string, ft reflect.Type, column node) error {
-	items, _ := columnItems(column)
-	for _, it := range items {
-		if it.datatype != DataTypeString {
-			return fmt.Errorf("%s: its Go type %s sets the datatype; drop \"datatype\"", label, ft)
-		}
-	}
-	elem := ft
-	if ft.Kind() == reflect.Pointer {
-		elem = ft.Elem()
-	} else if p.proveColumn(column).nullable {
-		return fmt.Errorf("%s: its tag can draw null, which %s cannot hold; make it *%s", label, ft, ft)
-	}
-	kind := columnKinds[elem.Kind()]
-	if kind.datatype == DataTypeString {
-		return nil
-	}
-	for _, it := range items {
-		v := p.proveColumnItem(it)
-		if reason := v.not[kind.datatype]; reason != "" {
-			return fmt.Errorf("%s (%s): %s", label, ft, reason)
-		}
-		if !kind.holds(v) {
-			return fmt.Errorf("%s (%s): %q is not proven within %s; narrow it to that range, or make the field %s", label, ft, it.format, elem.Kind(), kind.wider)
-		}
-	}
-	return nil
-}
-
 // fill draws the record into v's tagged fields, then each nested struct as a record of its own.
 func (s *structShape) fill(state *generatorState, v reflect.Value) {
 	if s.record != nil {