A type inference error + location info.

Types of errors:

• ImpossibleExpr, ImpossiblePattern and ImpossibleType: for hand-crafted elm-syntax Files with nonsensical data, like a function call without arguments or a 4-tuple. You should never be able to reach these when using elm-syntax's parser on real Elm files.

• ImpossibleDocsType: Similar but for hand-crafted docs.json. Real docs.json files emitted by the Elm compiler should never produce these.

• MissingModuleName: Raised when Elm.TypeInference.project is called with a Dict key [].

• ModuleNotFound: Raised when Elm.TypeInference.inferModule is called with module that's not part of the indexed Project.

• VarNotFound:

  module Main exposing (foo)
  
  
  foo =
      bar
  
  
  --> VarNotFound
  --    { usedIn = [ "Main" ]
  --    , varName = "bar"
  --    }

• AmbiguousName:

  module Main exposing (foo)
  
  
  import A exposing (thing)
  import B exposing (thing)
  
  
  foo =
      thing
  
  
  --> AmbiguousName
  --    { usedIn = [ "Main" ]
  --    , varName = "thing"
  --    , possibleModules = [ [ "A" ], [ "B" ] ]
  --    }

• AmbiguousModuleOwner:

  Raised when two direct dependencies expose a module of the same name, eg. mdgriffith/elm-ui and mdgriffith/style-elements (both expose Element):

  module Main exposing (foo)
  
  
  import Element
  
  
  foo _ =
      Element.text "hi"
  
  
  --> AmbiguousModuleOwner
  --    { moduleName = "Element"
  --    , possiblePackages =
  --        [ "mdgriffith/elm-ui"
  --        , "mdgriffith/style-elements"
  --        ]
  --    }

• TypeMismatch:

  module Main exposing (foo)
  
  
  foo : Int
  foo =
      "abc"
  
  
  --> TypeMismatch Type.Int Type.String

• InfiniteType:

  module Main exposing (foo)
  
  
  foo x =
      x x
  
  
  --> InfiniteType
  --    (Type.TypeVar "a")
  --    (Type.Function
  --      { from = Type.TypeVar "a"
  --      , to = Type.TypeVar "b"
  --      }
  --    )

• ConstraintMismatch:

  module Main exposing (foo)
  
  
  foo x =
      x + "a"
  
  
  --> ConstraintMismatch
  --    (Type.TypeVar "number")
  --    Type.String

Render an error for diagnostic output.