"No unfolding" error in Visual Studio Code

Question

I copied the Plutus starter template, Plutus Platform starter project, and created a file, BasicPlutusTx.hs (and added it under exposed-modules in the .cabal file).

Then I started copying over all the code from the introductory tutorial, Using Plutus Tx.

When I added the code,

functions :: CompiledCode Integer
functions = $$(compile [|| myProgram ||])

it caused Visual Studio Code to complain, giving an error at the top of the file:

Program error: GHC Core to PLC plugin: E043:Error: Reference to a name which is not a local, a builtin, or an external INLINABLE function: Variable PlutusTx.Builtins.addInteger
            No unfolding
Context: Compiling expr: PlutusTx.Builtins.addInteger
Context: Compiling expr: PlutusTx.Builtins.addInteger
                           (PlutusTx.Builtins.addInteger 1 1)
Context: Compiling expr: PlutusTx.Builtins.addInteger
                           (PlutusTx.Builtins.addInteger 1 1) (BasicPlutusTx.plusOne 1)
Context: Compiling definition of: BasicPlutusTx.myProgram
Context: Compiling expr: BasicPlutusTx.myProgram
Context: Compiling expr at "main:BasicPlutusTx:(76,16)-(76,41)"compile

However, cabal build still works.