initial checkin of SkSL compiler

src/sksl/ir/SkSLPrefixExpression.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_PREFIXEXPRESSION
+#define SKSL_PREFIXEXPRESSION
+
+#include "SkSLExpression.h"
+
+namespace SkSL {
+
+/**
+ * An expression modified by a unary operator appearing before it, such as '!flag'.
+ */
+struct PrefixExpression : public Expression {
+    PrefixExpression(Token::Kind op, std::unique_ptr<Expression> operand)
+    : INHERITED(operand->fPosition, kPrefix_Kind, operand->fType)
+    , fOperand(std::move(operand))
+    , fOperator(op) {}
+
+    virtual std::string description() const override {
+        return Token::OperatorName(fOperator) + fOperand->description();
+    }
+
+    const std::unique_ptr<Expression> fOperand;
+    const Token::Kind fOperator;
+
+    typedef Expression INHERITED;
+};
+
+} // namespace
+
+#endif