ast: Unexport the GetPrefix function

This change does not affect any functionality it just unexports the
GetPrefix function to keep the TypeEnv API as mimimal as possible. The
function has been moved into check.go to live next to other similar
helpers (e.g., getArgTypes).

Signed-off-by: Torin Sandall <torinsandall@gmail.com>

ast/check.go

@@ -157,7 +157,7 @@ func (tc *typeChecker) checkRule(env *TypeEnv, rule *Rule) {
 				tc.err([]*Error{err})
 				continue
 			}
-			prefixRef, t := env.GetPrefix(ref)
+			prefixRef, t := getPrefix(env, ref)
 			if t == nil || len(prefixRef) == len(ref) {
 				env.tree.Put(ref, refType)
 			} else {
@@ -1015,6 +1015,23 @@ func getArgTypes(env *TypeEnv, args []*Term) []types.Type {
 	return pre
 }
 
+// getPrefix returns the shortest prefix of ref that exists in env
+func getPrefix(env *TypeEnv, ref Ref) (Ref, types.Type) {
+	if len(ref) == 1 {
+		t := env.Get(ref)
+		if t != nil {
+			return ref, t
+		}
+	}
+	for i := 1; i < len(ref); i++ {
+		t := env.Get(ref[:i])
+		if t != nil {
+			return ref[:i], t
+		}
+	}
+	return nil, nil
+}
+
 // override takes a type t and returns a type obtained from t where the path represented by ref within it has type o (overriding the original type of that path)
 func override(ref Ref, t types.Type, o types.Type, rule *Rule) (types.Type, *Error) {
 	newStaticProps := []*types.StaticProperty{}

ast/env.go

@@ -29,23 +29,6 @@ func (env *TypeEnv) WithSchemas(schemas *SchemaSet) *TypeEnv {
 	return env
 }
 
-// GetPrefix returns the shortest prefix of ref that exists in env
-func (env *TypeEnv) GetPrefix(ref Ref) (Ref, types.Type) {
-	if len(ref) == 1 {
-		t := env.Get(ref)
-		if t != nil {
-			return ref, t
-		}
-	}
-	for i := 1; i < len(ref); i++ {
-		t := env.Get(ref[:i])
-		if t != nil {
-			return ref[:i], t
-		}
-	}
-	return nil, nil
-}
-
 // Get returns the type of x.
 func (env *TypeEnv) Get(x interface{}) types.Type {