Types

Any type (the top type of this type system). A variable of this type can contain any value, including undefined and null and any JS value. This type supports a very limited set of Scala operations, the ones common to all values. Basically only reference equality tests and instance tests. It also supports all JavaScript operations, since all Scala objects are also genuine JavaScript objects. The type java.lang.Object in the back-end maps to AnyType because it can hold JS values (not only instances of Scala.js classes).

Array type.

Array type.

Boolean type. It does not accept null nor undefined.

8-bit signed integer type. It does not accept null nor undefined.

Char type, a 16-bit UTF-16 code unit. It does not accept null nor undefined.

Class (or interface) type.

Class (or interface) type.

Double type (64-bit). It does not accept null nor undefined.

Float type (32-bit). It does not accept null nor undefined.

32-bit signed integer type. It does not accept null nor undefined.

64-bit signed integer type. It does not accept null nor undefined.

No type.

Nothing type (the bottom type of this type system). Expressions from which one can never come back are typed as Nothing. For example, throw and return.

The type of null. It does not accept undefined. The null type is a subtype of all class types and array types.

Primitive type reference.

Record type. Used by the optimizer to inline classes as records with multiple fields. They are desugared as several local variables by JSDesugaring. Record types cannot cross method boundaries, so they cannot appear as the type of fields or parameters, nor as result types of methods. The compiler itself never generates record types.

16-bit signed integer type. It does not accept null nor undefined.

String type. It does not accept null nor undefined.

Type of a term (expression or statement) in the IR.

There is a many-to-one relationship from TypeRefs to Types, because java.lang.Object and JS types all collapse to AnyType.

In fact, there are two Types that do not have any real equivalent in type refs: StringType and UndefType, as they refer to the non-null variants of java.lang.String and java.lang.Void, respectively.

Type reference (allowed for classOf[], is/asInstanceOf[]).

A TypeRef has exactly the same level of precision as a JVM type. There is a one-to-one relationship between a TypeRef and an instance of java.lang.Class at run-time. This means that:

• All primitive types have their TypeRef (including scala.Byte and scala.Short), and they are different from their boxed versions.
• JS types are not erased to any
• Array types are like on the JVM

A TypeRef therefore uniquely identifies a classOf[T]. It is also the type refs that are used in method signatures, and which therefore dictate JVM/IR overloading.

The type of undefined.

Tests whether a type lhs is a subtype of rhs (or equal). NoType is never a subtype or supertype of anything (including itself). All other types are subtypes of themselves.

Generates a literal zero of the given type.