Database Project with scalar functions as CHECK constraints - sql-server

Question

I've seen some related posts on SO, but haven't been able to figure out what is happening here. I have a Database Project in Visual Studio 2013. Here is some code for a simple "Users" table:
CREATE TABLE [dbo].[Users]
(
[ID] BIGINT IDENTITY(1,1) NOT NULL,
[Name] NVARCHAR(50) NOT NULL,
[Email] NVARCHAR(256) NOT NULL,
[Password] BINARY(20) NOT NULL,
CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([ID]),
CONSTRAINT [IX_Users_Email] UNIQUE ([Email]),
CONSTRAINT [CK_Users] CHECK ([dbo].[CheckUserIsValid]([Users].[Name], [Users].[Email]) = 1)
)
And here is the code for CheckUserIsValid:
CREATE FUNCTION [dbo].[CheckUserIsValid]
(
#name NVARCHAR(50),
#email NVARCHAR(256)
)
RETURNS BIT
WITH SCHEMABINDING
AS
BEGIN
IF #name = ''
OR #email = ''
OR EXISTS(SELECT 1
FROM [dbo].[BlockedEmails]
WHERE [dbo].[BlockedEmails].[Email] = #email)
OR EXISTS(SELECT 1
FROM [dbo].[ApprovalCodes]
WHERE [dbo].[ApprovalCodes].[Email] = #email)
RETURN 0
RETURN 1
END
Now, the weird part is that when I open the code files BEFORE building the project, VS does not show any errors. When I try to build it, the build fails and I get a couple of different errors:
SQL04121: Cannot find either column "dbo" or the user-defined function or aggregate "dbo.CheckUserIsValid", or the name is ambiguous. (this one is thrown on the Users table)
SQL00208: Invalid object name 'dbo.BlockedEmails'. (this one is thrown on the function)
I've read this may have something to do with how I am using a scalar function in my check constraint. Pretty stuck now though. Not sure what to try next.
UPDATE
So, if I leave the function unchanged, but change the table to:
CREATE TABLE [dbo].[Users]
(
[ID] BIGINT IDENTITY(1,1) NOT NULL,
[Name] NVARCHAR(50) NOT NULL,
[Email] NVARCHAR(256) NOT NULL,
[Password] BINARY(20) NOT NULL,
CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([ID]),
CONSTRAINT [IX_Users_Email] UNIQUE ([Email])
)
GO
ALTER TABLE [dbo].[Users] ADD CONSTRAINT [CK_Users] CHECK ([dbo].[CheckUserIsValid]([Users].[Name], [Users].[Email]) = 1)
GO
then bizarrely it builds fine. What the heck?