Package structure refactor.

internal/jet/alias.go

@@ -0,0 +1,34 @@
+package jet
+
+type alias struct {
+	expression Expression
+	alias      string
+}
+
+func newAlias(expression Expression, aliasName string) Projection {
+	return &alias{
+		expression: expression,
+		alias:      aliasName,
+	}
+}
+
+func (a *alias) fromImpl(subQuery SelectTable) Projection {
+	column := newColumn(a.alias, "", nil)
+	column.parent = &column
+	column.subQuery = subQuery
+
+	return &column
+}
+
+func (a *alias) serializeForProjection(statement StatementType, out *SqlBuilder) error {
+	err := a.expression.serialize(statement, out)
+
+	if err != nil {
+		return err
+	}
+
+	out.WriteString("AS")
+	out.writeAlias(a.alias)
+
+	return nil
+}