Dhall.TypeCheck

dhall-1.42.2: A configuration language guaranteed to terminate

Safe Haskell | None
Language | Haskell2010

Dhall.TypeCheck

Contents

- Type-checking
- Types

Description

This module contains the logic for type checking Dhall code

Synopsis

- typeWith :: Context (Expr s X) -> Expr s X -> Either (TypeError s X) (Expr s X)
- typeOf :: Expr s X -> Either (TypeError s X) (Expr s X)
- typeWithA :: (Eq a, Pretty a) => Typer a -> Context (Expr s a) -> Expr s a -> Either (TypeError s a) (Expr s a)
- checkContext :: Context (Expr s X) -> Either (TypeError s X) ()
- messageExpressions :: Applicative f => (Expr s a -> f (Expr t b)) -> TypeMessage s a -> f (TypeMessage t b)
- type Typer a = forall s. a -> Expr s a
- type X = Void
- absurd :: Void -> a
- data TypeError s a = TypeError {
  - context :: Context (Expr s a)
  - current :: Expr s a
  - typeMessage :: TypeMessage s a
  }
- newtype DetailedTypeError s a = DetailedTypeError (TypeError s a)
- data Censored
  - = CensoredDetailed (DetailedTypeError Src X)
  - | Censored (TypeError Src X)
- data TypeMessage s a
  - = UnboundVariable Text
  - | InvalidInputType (Expr s a)
  - | InvalidOutputType (Expr s a)
  - | NotAFunction (Expr s a) (Expr s a)
  - | TypeMismatch (Expr s a) (Expr s a) (Expr s a) (Expr s a)
  - | AnnotMismatch (Expr s a) (Expr s a) (Expr s a)
  - | Untyped
  - | MissingListType
  - | MismatchedListElements Int (Expr s a) (Expr s a) (Expr s a)
  - | InvalidListElement Int (Expr s a) (Expr s a) (Expr s a)
  - | InvalidListType (Expr s a)
  - | ListLitInvariant
  - | InvalidSome (Expr s a) (Expr s a) (Expr s a)
  - | InvalidPredicate (Expr s a) (Expr s a)
  - | IfBranchMismatch (Expr s a) (Expr s a) (Expr s a) (Expr s a)
  - | InvalidFieldType Text (Expr s a)
  - | InvalidAlternativeType Text (Expr s a)
  - | ListAppendMismatch (Expr s a) (Expr s a)
  - | MustUpdateARecord (Expr s a) (Expr s a) (Expr s a)
  - | MustCombineARecord Char (Expr s a) (Expr s a)
  - | InvalidDuplicateField Text (Expr s a) (Expr s a)
  - | InvalidRecordCompletion Text (Expr s a)
  - | CompletionSchemaMustBeARecord (Expr s a) (Expr s a)
  - | CombineTypesRequiresRecordType (Expr s a) (Expr s a)
  - | RecordTypeMismatch Const Const (Expr s a) (Expr s a)
  - | DuplicateFieldCannotBeMerged (NonEmpty Text)
  - | FieldCollision (NonEmpty Text)
  - | FieldTypeCollision (NonEmpty Text)
  - | MustMergeARecord (Expr s a) (Expr s a)
  - | MustMergeUnionOrOptional (Expr s a) (Expr s a)
  - | MustMapARecord (Expr s a) (Expr s a)
  - | InvalidToMapRecordKind (Expr s a) (Expr s a)
  - | HeterogenousRecordToMap (Expr s a) (Expr s a) (Expr s a)
  - | InvalidToMapType (Expr s a)
  - | MapTypeMismatch (Expr s a) (Expr s a)
  - | MissingToMapType
  - | UnusedHandler (Set Text)
  - | MissingHandler Text (Set Text)
  - | HandlerInputTypeMismatch Text (Expr s a) (Expr s a)
  - | DisallowedHandlerType Text (Expr s a) (Expr s a) Text
  - | HandlerOutputTypeMismatch Text (Expr s a) Text (Expr s a)
  - | InvalidHandlerOutputType Text (Expr s a) (Expr s a)
  - | MissingMergeType
  - | HandlerNotAFunction Text (Expr s a)
  - | CantAccess Text (Expr s a) (Expr s a)
  - | CantProject Text (Expr s a) (Expr s a)
  - | CantProjectByExpression (Expr s a)
  - | DuplicateProjectionLabel Text
  - | MissingField Text (Expr s a)
  - | MissingConstructor Text (Expr s a)
  - | ProjectionTypeMismatch Text (Expr s a) (Expr s a) (Expr s a) (Expr s a)
  - | AssertionFailed (Expr s a) (Expr s a)
  - | NotAnEquivalence (Expr s a)
  - | IncomparableExpression (Expr s a)
  - | EquivalenceTypeMismatch (Expr s a) (Expr s a) (Expr s a) (Expr s a)
  - | NotWithARecord (Expr s a) (Expr s a)
  - | CantAnd (Expr s a) (Expr s a)
  - | CantOr (Expr s a) (Expr s a)
  - | CantEQ (Expr s a) (Expr s a)
  - | CantNE (Expr s a) (Expr s a)
  - | CantInterpolate (Expr s a) (Expr s a)
  - | CantTextAppend (Expr s a) (Expr s a)
  - | CantListAppend (Expr s a) (Expr s a)
  - | CantAdd (Expr s a) (Expr s a)
  - | CantMultiply (Expr s a) (Expr s a)
  - | OptionalWithTypeMismatch
  - | NotALabelPath
  - | NotAQuestionPath Text
  - | ShowConstructorNotOnUnion
- prettyTypeMessage :: (Eq a, Pretty a) => TypeMessage s a -> ErrorMessages
- data ErrorMessages = ErrorMessages {
  - short :: Doc Ann
  - hints :: [Doc Ann]
  - long :: Doc Ann
  }

# Type-checking

typeWith :: Context (Expr s X) -> Expr s X -> Either (TypeError s X) (Expr s X) #

Type-check an expression and return the expression's type if type-checking succeeds or an error if type-checking fails

`typeWith` does not necessarily normalize the type since full normalization is not necessary for just type-checking. If you actually care about the returned type then you may want to `normalize` it afterwards.

The supplied `Context` records the types of the names in scope. If these are ill-typed, the return value may be ill-typed.

typeOf :: Expr s X -> Either (TypeError s X) (Expr s X) #

`typeOf` is the same as `typeWith` with an empty context, meaning that the expression must be closed (i.e. no free variables), otherwise type-checking will fail.

typeWithA :: (Eq a, Pretty a) => Typer a -> Context (Expr s a) -> Expr s a -> Either (TypeError s a) (Expr s a) #

Generalization of `typeWith` that allows type-checking the `Embed` constructor with custom logic

checkContext :: Context (Expr s X) -> Either (TypeError s X) () #

This function verifies that a custom context is well-formed so that type-checking will not loop

Note that `typeWith` already calls `checkContext` for you on the `Context` that you supply

messageExpressions :: Applicative f => (Expr s a -> f (Expr t b)) -> TypeMessage s a -> f (TypeMessage t b) #

`Traversal` that traverses every `Expr` in a `TypeMessage`

# Types

type Typer a = forall s. a -> Expr s a #

Function that converts the value inside an `Embed` constructor into a new expression

type X = Void #

Deprecated: Use Data.Void.Void instead

A type synonym for `Void`

This is provided for backwards compatibility, since Dhall used to use its own `X` type instead of `Data.Void.`Void``. You should use `Void` instead of `X` now

absurd :: Void -> a #

Since `Void` values logically don't exist, this witnesses the logical reasoning tool of "ex falso quodlibet".

    >>> let x :: Either Void Int; x = Right 5
    >>> :{
    case x of
        Right r -> r
        Left l  -> absurd l
    :}
    5

@since base-4.8.0.0

data TypeError s a #

A structured type error that includes context

Constructors

TypeError |
Fields context :: Context (Expr s a) current :: Expr s a typeMessage :: TypeMessage s a

#### Instances

Instances details

(Eq a, Pretty s, Pretty a, Typeable s, Typeable a) => Exception (TypeError s a) # |
Instance details Defined in Dhall.TypeCheck Methods toException :: TypeError s a -> SomeException # fromException :: SomeException -> Maybe (TypeError s a) # displayException :: TypeError s a -> String # backtraceDesired :: TypeError s a -> Bool #
(Eq a, Pretty s, Pretty a) => Show (TypeError s a) # |
Instance details Defined in Dhall.TypeCheck Methods showsPrec :: Int -> TypeError s a -> ShowS # show :: TypeError s a -> String # showList :: [TypeError s a] -> ShowS #
(Eq a, Pretty s, Pretty a) => Pretty (TypeError s a) # |
Instance details Defined in Dhall.TypeCheck Methods pretty :: TypeError s a -> Doc ann # prettyList :: [TypeError s a] -> Doc ann #

newtype DetailedTypeError s a #

Newtype used to wrap error messages so that they render with a more detailed explanation of what went wrong

Constructors

DetailedTypeError (TypeError s a) |

#### Instances

Instances details

(Eq a, Pretty s, Pretty a, Typeable s, Typeable a) => Exception (DetailedTypeError s a) # |
Instance details Defined in Dhall.TypeCheck Methods toException :: DetailedTypeError s a -> SomeException # fromException :: SomeException -> Maybe (DetailedTypeError s a) # displayException :: DetailedTypeError s a -> String # backtraceDesired :: DetailedTypeError s a -> Bool #
(Eq a, Pretty s, Pretty a) => Show (DetailedTypeError s a) # |
Instance details Defined in Dhall.TypeCheck Methods showsPrec :: Int -> DetailedTypeError s a -> ShowS # show :: DetailedTypeError s a -> String # showList :: [DetailedTypeError s a] -> ShowS #
(Eq a, Pretty s, Pretty a) => Pretty (DetailedTypeError s a) # |
Instance details Defined in Dhall.TypeCheck Methods pretty :: DetailedTypeError s a -> Doc ann # prettyList :: [DetailedTypeError s a] -> Doc ann #

data Censored #

Wrap a type error in this exception type to censor source code and `Text` literals from the error message

Constructors

CensoredDetailed (DetailedTypeError Src X) |
Censored (TypeError Src X) |

#### Instances

Instances details

Exception Censored # |
Instance details Defined in Dhall.TypeCheck Methods toException :: Censored -> SomeException # fromException :: SomeException -> Maybe Censored # displayException :: Censored -> String # backtraceDesired :: Censored -> Bool #
Show Censored # |
Instance details Defined in Dhall.TypeCheck Methods showsPrec :: Int -> Censored -> ShowS # show :: Censored -> String # showList :: [Censored] -> ShowS #
Pretty Censored # |
Instance details Defined in Dhall.TypeCheck Methods pretty :: Censored -> Doc ann # prettyList :: [Censored] -> Doc ann #

data TypeMessage s a #

The specific type error

Constructors

UnboundVariable Text |
InvalidInputType (Expr s a) |
InvalidOutputType (Expr s a) |
NotAFunction (Expr s a) (Expr s a) |
TypeMismatch (Expr s a) (Expr s a) (Expr s a) (Expr s a) |
AnnotMismatch (Expr s a) (Expr s a) (Expr s a) |
Untyped |
MissingListType |
MismatchedListElements Int (Expr s a) (Expr s a) (Expr s a) |
InvalidListElement Int (Expr s a) (Expr s a) (Expr s a) |
InvalidListType (Expr s a) |
ListLitInvariant |
InvalidSome (Expr s a) (Expr s a) (Expr s a) |
InvalidPredicate (Expr s a) (Expr s a) |
IfBranchMismatch (Expr s a) (Expr s a) (Expr s a) (Expr s a) |
InvalidFieldType Text (Expr s a) |
InvalidAlternativeType Text (Expr s a) |
ListAppendMismatch (Expr s a) (Expr s a) |
MustUpdateARecord (Expr s a) (Expr s a) (Expr s a) |
MustCombineARecord Char (Expr s a) (Expr s a) |
InvalidDuplicateField Text (Expr s a) (Expr s a) |
InvalidRecordCompletion Text (Expr s a) |
CompletionSchemaMustBeARecord (Expr s a) (Expr s a) |
CombineTypesRequiresRecordType (Expr s a) (Expr s a) |
RecordTypeMismatch Const Const (Expr s a) (Expr s a) |
DuplicateFieldCannotBeMerged (NonEmpty Text) |
FieldCollision (NonEmpty Text) |
FieldTypeCollision (NonEmpty Text) |
MustMergeARecord (Expr s a) (Expr s a) |
MustMergeUnionOrOptional (Expr s a) (Expr s a) |
MustMapARecord (Expr s a) (Expr s a) |
InvalidToMapRecordKind (Expr s a) (Expr s a) |
HeterogenousRecordToMap (Expr s a) (Expr s a) (Expr s a) |
InvalidToMapType (Expr s a) |
MapTypeMismatch (Expr s a) (Expr s a) |
MissingToMapType |
UnusedHandler (Set Text) |
MissingHandler Text (Set Text) |
HandlerInputTypeMismatch Text (Expr s a) (Expr s a) |
DisallowedHandlerType Text (Expr s a) (Expr s a) Text |
HandlerOutputTypeMismatch Text (Expr s a) Text (Expr s a) |
InvalidHandlerOutputType Text (Expr s a) (Expr s a) |
MissingMergeType |
HandlerNotAFunction Text (Expr s a) |
CantAccess Text (Expr s a) (Expr s a) |
CantProject Text (Expr s a) (Expr s a) |
CantProjectByExpression (Expr s a) |
DuplicateProjectionLabel Text |
MissingField Text (Expr s a) |
MissingConstructor Text (Expr s a) |
ProjectionTypeMismatch Text (Expr s a) (Expr s a) (Expr s a) (Expr s a) |
AssertionFailed (Expr s a) (Expr s a) |
NotAnEquivalence (Expr s a) |
IncomparableExpression (Expr s a) |
EquivalenceTypeMismatch (Expr s a) (Expr s a) (Expr s a) (Expr s a) |
NotWithARecord (Expr s a) (Expr s a) |
CantAnd (Expr s a) (Expr s a) |
CantOr (Expr s a) (Expr s a) |
CantEQ (Expr s a) (Expr s a) |
CantNE (Expr s a) (Expr s a) |
CantInterpolate (Expr s a) (Expr s a) |
CantTextAppend (Expr s a) (Expr s a) |
CantListAppend (Expr s a) (Expr s a) |
CantAdd (Expr s a) (Expr s a) |
CantMultiply (Expr s a) (Expr s a) |
OptionalWithTypeMismatch |
NotALabelPath |
NotAQuestionPath Text |
ShowConstructorNotOnUnion |

#### Instances

Instances details

(Show s, Show a) => Show (TypeMessage s a) # |
Instance details Defined in Dhall.TypeCheck Methods showsPrec :: Int -> TypeMessage s a -> ShowS # show :: TypeMessage s a -> String # showList :: [TypeMessage s a] -> ShowS #

prettyTypeMessage :: (Eq a, Pretty a) => TypeMessage s a -> ErrorMessages #

Convert a `TypeMessage` to short- and long-form `ErrorMessages`

data ErrorMessages #

Output of `prettyTypeMessage`, containing short- and long-form error messages

Constructors

ErrorMessages |
Fields short :: Doc Ann Default succinct 1-line explanation of what went wrong hints :: [Doc Ann] Possibly-empty hints based on specific types involved in the error long :: Doc Ann Longer and more detailed explanation of the error