Config variables reader

Fixes: 182330871
Test: go test config_variables_test.go
Change-Id: I89240fb0f1900172cb4d62057c86907bb9a1f58f

mk2rbc/types.go

@@ -0,0 +1,55 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mk2rbc
+
+// Starlark expression types we use
+type starlarkType int
+
+const (
+	starlarkTypeUnknown starlarkType = iota
+	starlarkTypeList    starlarkType = iota
+	starlarkTypeString  starlarkType = iota
+	starlarkTypeInt     starlarkType = iota
+	starlarkTypeBool    starlarkType = iota
+	starlarkTypeVoid    starlarkType = iota
+)
+
+type varClass int
+
+const (
+	VarClassConfig varClass = iota
+	VarClassSoong  varClass = iota
+	VarClassLocal  varClass = iota
+)
+
+type variableRegistrar interface {
+	NewVariable(name string, varClass varClass, valueType starlarkType)
+}
+
+// ScopeBase is a dummy implementation of the mkparser.Scope.
+// All our scopes are read-only and resolve only simple variables.
+type ScopeBase struct{}
+
+func (s ScopeBase) Set(_, _ string) {
+	panic("implement me")
+}
+
+func (s ScopeBase) Call(_ string, _ []string) []string {
+	panic("implement me")
+}
+
+func (s ScopeBase) SetFunc(_ string, _ func([]string) []string) {
+	panic("implement me")
+}