girard/types

The public type vocabulary girard reports: the inferred Type model and the Error describing why a module could not be typed. The inference engine and its helpers are implementation detail and live under girard/internal/*.

Types

Error

</>

Why a module could not be typed. Variants describe the failure in terms of the type system and the offending source construct.

pub type Error {
  TypeMismatch(left: Type, right: Type)
  ArityMismatch
  RecursiveType(id: Int, type_: Type)
  UnboundVariable(name: String)
  UnknownConstructor(name: String)
  UnknownModule(alias: String)
  NoSuchExport(module: String, name: String)
  NoSuchField(type_name: String, label: String)
  NotARecord
  NotATuple
  TupleIndexOutOfRange(index: Int)
  UnknownLabel(label: String)
  AmbiguousCall
  MissingArgument
  Unsupported(feature: String)
  ParseFailed(glance.Error)
}

Constructors

```
TypeMismatch(left: Type, right: Type)
```
```
ArityMismatch
```
```
RecursiveType(id: Int, type_: Type)
```
```
UnboundVariable(name: String)
```
```
UnknownConstructor(name: String)
```
```
UnknownModule(alias: String)
```

NoSuchExport(module: String, name: String)

NoSuchField(type_name: String, label: String)

```
NotARecord
```
```
NotATuple
```
```
TupleIndexOutOfRange(index: Int)
```
```
UnknownLabel(label: String)
```
```
AmbiguousCall
```
```
MissingArgument
```
```
Unsupported(feature: String)
```
```
ParseFailed(glance.Error)
```

Scheme

</>

A polymorphic type scheme forall vars. type_: the generalized type of a top-level function or constant. vars are the ids of the Vars in type_ that are universally quantified (generic); a monomorphic binding is Scheme([], type_).

pub type Scheme {
  Scheme(vars: List(Int), type_: Type)
}

Constructors

```
Scheme(vars: List(Int), type_: Type)
```

Type

</>

pub type Type {
  Named(module: String, name: String, arguments: List(Type))
  Fn(arguments: List(Type), return: Type)
  Var(id: Int)
  Tuple(elements: List(Type))
}

Constructors

```
Named(module: String, name: String, arguments: List(Type))
```
A named, nominal type such as Int, List(a), Result(a, e) or a user-defined custom type. module is "gleam" for prelude types.
```
Fn(arguments: List(Type), return: Type)
```
A function type fn(a, b) -> c.
```
Var(id: Int)
```
A type variable. Its state (unbound / bound / generic) lives in the substitution table keyed by id during inference.
```
Tuple(elements: List(Type))
```
A tuple type #(a, b, c).