reify the list values before validation

If the list was marked as computed, all values will be raw config
values. Fetch the individual keys from the config to get any known
values before validating.

helper/schema/schema.go

@@ -1219,6 +1219,13 @@ func (m schemaMap) validateList(
 	for i, raw := range raws {
 		key := fmt.Sprintf("%s.%d", k, i)
 
+		// Reify the key value from the ResourceConfig.
+		// If the list was computed we have all raw values, but some of these
+		// may be known in the config, and aren't individually marked as Computed.
+		if r, ok := c.Get(key); ok {
+			raw = r
+		}
+
 		var ws2 []string
 		var es2 []error
 		switch t := schema.Elem.(type) {