[parser] parser: Implement Restore for IsTruthExpr (#90)

parser/ast/expressions.go

@@ -715,7 +715,20 @@ type IsTruthExpr struct {
 
 // Restore implements Node interface.
 func (n *IsTruthExpr) Restore(ctx *RestoreCtx) error {
-	return errors.New("Not implemented")
+	if err := n.Expr.Restore(ctx); err != nil {
+		return errors.Trace(err)
+	}
+	if n.Not {
+		ctx.WriteKeyWord(" IS NOT")
+	} else {
+		ctx.WriteKeyWord(" IS")
+	}
+	if n.True > 0 {
+		ctx.WriteKeyWord(" TRUE")
+	} else {
+		ctx.WriteKeyWord(" FALSE")
+	}
+	return nil
 }
 
 // Format the ExprNode into a Writer.

parser/ast/expressions_test.go

@@ -142,6 +142,19 @@ func (tc *testExpressionsSuite) TestIsNullExprRestore(c *C) {
 	RunNodeRestoreTest(c, testCases, "select %s", extractNodeFunc)
 }
 
+func (tc *testExpressionsSuite) TestIsTruthRestore(c *C) {
+	testCases := []NodeRestoreTestCase{
+		{"a is true", "`a` IS TRUE"},
+		{"a is not true", "`a` IS NOT TRUE"},
+		{"a is FALSE", "`a` IS FALSE"},
+		{"a is not false", "`a` IS NOT FALSE"},
+	}
+	extractNodeFunc := func(node Node) Node {
+		return node.(*SelectStmt).Fields.Fields[0].Expr
+	}
+	RunNodeRestoreTest(c, testCases, "select %s", extractNodeFunc)
+}
+
 func (tc *testExpressionsSuite) TestBetweenExprRestore(c *C) {
 	testCases := []NodeRestoreTestCase{
 		{"b between 1 and 2", "`b` BETWEEN 1 AND 2"},