Fix limitations on Elem for TypeMap

helper/schema/schema.go

@@ -167,7 +167,8 @@ type Schema struct {
 	// The following fields are only set for a TypeList, TypeSet, or TypeMap.
 	//
 	// Elem represents the element type. For a TypeMap, it must be a *Schema
-	// with a Type of TypeString, otherwise it may be either a *Schema or a
+	// with a Type that is one of the primitives: TypeString, TypeBool,
+	// TypeInt or TypeFloat. Otherwise it may be either a *Schema or a
 	// *Resource. If it is *Schema, the element type is just a simple value.
 	// If it is *Resource, the element type is a complex structure,
 	// potentially with its own lifecycle.