Enum ErrorKind

#[non_exhaustive]
pub enum ErrorKind<Prim: PrimitiveType> {
    TypeMismatch(Type<Prim>, Type<Prim>),
    TupleLenMismatch {
        lhs: TupleLen,
        rhs: TupleLen,
        context: TupleContext,
    },
    UndefinedVar(String),
    RecursiveType(Type<Prim>),
    RepeatedAssignment(String),
    InvalidFieldName(String),
    CannotIndex,
    UnsupportedIndex,
    IndexOutOfBounds {
        index: usize,
        len: TupleLen,
    },
    RepeatedField(String),
    CannotAccessFields,
    FieldsMismatch {
        lhs_fields: HashSet<String>,
        rhs_fields: HashSet<String>,
    },
    MissingFields {
        fields: HashSet<String>,
        available_fields: HashSet<String>,
    },
    UnresolvedParam,
    FailedConstraint {
        ty: Type<Prim>,
        constraint: Box<dyn Constraint<Prim>>,
    },
    DynamicLen(TupleLen),
    UnsupportedFeature(UnsupportedType),
    UnsupportedType(Type<Prim>),
    UnsupportedParam,
    AstConversion(AstConversionError),
}

Kinds of errors that can occur during type inference.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

TypeMismatch(Type<Prim>, Type<Prim>)

Trying to unify incompatible types. The first type is LHS, the second one is RHS.

TupleLenMismatch

Incompatible tuple lengths.

Fields

lhs: TupleLen

Length of the LHS. This is the length determined by type annotations for assignments and the number of actually supplied args in function calls.

rhs: TupleLen

Length of the RHS. This is usually the actual tuple length in assignments and the number of expected args in function calls.

context: TupleContext

Context in which the error has occurred.

UndefinedVar(String)

Undefined variable occurrence.

RecursiveType(Type<Prim>)

Trying to unify a type with a type containing it.

RepeatedAssignment(String)

Repeated assignment to the same variable in function args or tuple destructuring.

InvalidFieldName(String)

Field name is invalid.

CannotIndex

Value cannot be indexed (i.e., not a tuple).

UnsupportedIndex

Unsupported indexing operation. For example, the receiver type is not known, or it is a tuple with an unknown length, and the type of the element cannot be decided.

IndexOutOfBounds

Index is out of bounds for the indexed tuple.

Fields

index: usize

Index.

len: TupleLen

Actual tuple length.

RepeatedField(String)

Repeated field in object initialization / destructuring.

CannotAccessFields

Cannot access fields in a value (i.e., it’s not an object).

FieldsMismatch

Field set differs between LHS and RHS, which are both concrete objects.

Fields

lhs_fields: HashSet<String>

Fields in LHS.

rhs_fields: HashSet<String>

Fields in RHS.

MissingFields

Concrete object does not have required fields.

Fields

fields: HashSet<String>

Missing fields.

available_fields: HashSet<String>

Available object fields.

UnresolvedParam

Mention of a bounded type or length variable in a type supplied to Substitutions::unify().

Bounded variables are instantiated into free vars automatically during type inference, so this error can only occur with types manually supplied to Substitutions::unify().

FailedConstraint

Failure when applying constraint to a type.

Fields

ty: Type<Prim>

Type that fails constraint requirement.

constraint: Box<dyn Constraint<Prim>>

Failing constraint.

DynamicLen(TupleLen)

Length with the static constraint is actually dynamic (contains UnknownLen::Dynamic).

UnsupportedFeature(UnsupportedType)

Language feature not supported by type inference logic.

UnsupportedType(Type<Prim>)

Type not supported by type inference logic. For example, a TypeArithmetic or Constraint implementations may return this error if they encounter an unknown Type variant.

UnsupportedParam

Unsupported use of type or length params in a function declaration.

Type or length params are currently not supported in type annotations. Here’s an example of code that triggers this error:

identity: (('T,)) -> ('T,) = |x| x;

AstConversion(AstConversionError)

Error while instantiating a type from AST.

Implementations

impl<Prim: PrimitiveType> ErrorKind<Prim>

pub fn unsupported<T: Into<UnsupportedType>>(ty: T) -> Self

Creates an error for an lvalue type not supported by the interpreter.

pub fn failed_constraint( ty: Type<Prim>, constraint: impl Constraint<Prim> + Clone, ) -> Self

Creates a “failed constraint” error.

Trait Implementations

impl<Prim: Clone + PrimitiveType> Clone for ErrorKind<Prim>

fn clone(&self) -> ErrorKind<Prim>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<Prim: Debug + PrimitiveType> Debug for ErrorKind<Prim>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<Prim: PrimitiveType> Display for ErrorKind<Prim>

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<Prim: PrimitiveType> Error for ErrorKind<Prim>

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.