Error found:
in module Main
at tests/purs/failing/3701.purs:39:8 - 39:34 (line 39, column 8 - line 39, column 34)

  Could not match type
           
    ( ... )
           
  with type
                      
    ( thing1 :: String
    ...               
    )                 
                      

while solving type class constraint
                                 
  Prim.Row.Nub ( thing1 :: String
               , thing1 :: String
               , thing2 :: Int   
               )                 
               ( thing1 :: String
               , thing1 :: String
               , thing2 :: Int   
               )                 
                                 
while applying a function fooMerge
  of type Union @Type t0               
            ( thing1 :: String         
            , thing2 :: Int            
            )                          
            ( thing1 :: String         
            , thing2 :: Int            
            | t0                       
            )                          
           => Nub @Type                
                ( thing1 :: String     
                , thing2 :: Int        
                | t0                   
                )                      
                ( thing1 :: String     
                , thing2 :: Int        
                | t0                   
                )                      
               => Record t0            
                  -> { thing1 :: String
                     , thing2 :: Int   
                     | t0              
                     }                 
  to argument { thing1: "foo"
              }              
while checking that expression fooMerge { thing1: "foo"
                                        }              
  has type { thing1 :: String
           , thing1 :: String
           , thing2 :: Int   
           }                 
in value declaration foo2

where t0 is an unknown type

See https://github.com/purescript/documentation/blob/master/errors/TypesDoNotUnify.md for more information,
or to contribute content related to this error.