initial checkin of SkSL compiler

src/sksl/ast/SkSLASTExpression.h

Index: src/sksl/ast/SkSLASTExpression.h
diff --git a/src/sksl/ast/SkSLASTExpression.h b/src/sksl/ast/SkSLASTExpression.h
new file mode 100644
index 0000000000000000000000000000000000000000..8a48271042a8f212acd28ad473672d90182e7785
--- /dev/null
+++ b/src/sksl/ast/SkSLASTExpression.h
@@ -0,0 +1,41 @@
+/*
+ * 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