initial checkin of SkSL compiler

src/sksl/ast/SkSLASTExpression.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+ 
+#ifndef SKSL_ASTEXPRESSION
+#define SKSL_ASTEXPRESSION
+
+#include "SkSLASTPositionNode.h"
+
+namespace SkSL {
+
+/**
+ * Abstract supertype of all expressions. 
+ */
+struct ASTExpression : public ASTPositionNode {
+    enum Kind {
+        kFloat_Kind,
+        kIdentifier_Kind,
+        kInt_Kind,
+        kBool_Kind,
+        kPrefix_Kind,
+        kSuffix_Kind,
+        kBinary_Kind,
+        kTernary_Kind
+    };
+
+    ASTExpression(Position position, Kind kind)
+    : INHERITED(position)
+    , fKind(kind) {}
+
+    const Kind fKind;
+
+    typedef ASTPositionNode INHERITED;
+};
+
+} // namespace
+
+#endif