initial checkin of SkSL compiler

src/sksl/ir/SkSLExpression.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_EXPRESSION
+#define SKSL_EXPRESSION
+
+#include "SkSLIRNode.h"
+#include "SkSLType.h"
+
+namespace SkSL {
+
+/**
+ * Abstract supertype of all expressions. 
+ */
+struct Expression : public IRNode {
+    enum Kind {
+        kBinary_Kind,
+        kBoolLiteral_Kind,
+        kConstructor_Kind,
+        kIntLiteral_Kind,
+        kFieldAccess_Kind,
+        kFloatLiteral_Kind,
+        kFunctionReference_Kind,
+        kFunctionCall_Kind,
+        kIndex_Kind,
+        kPrefix_Kind,
+        kPostfix_Kind,
+        kSwizzle_Kind,
+        kVariableReference_Kind,
+        kTernary_Kind,
+        kTypeReference_Kind,
+    };
+
+    Expression(Position position, Kind kind, std::shared_ptr<Type> type)
+    : INHERITED(position)
+    , fKind(kind)
+    , fType(std::move(type)) {}
+
+    virtual bool isConstant() const {
+        return false;
+    }
+
+    const Kind fKind;
+    const std::shared_ptr<Type> fType;
+
+    typedef IRNode INHERITED;
+};
+
+} // namespace
+
+#endif