Conversions
This section describes which type conversions are available.
Explicit conversions may occur as either T(v) (strict conversion) or v as T (optional conversion). The behavior of the call operator over a type may not always be a conversion depending on if T implements the static shock_proxy::call() method.
T(v) // failure throws a TypeError
v as T // failure returns a default value
Constant coercions
Constant coercions occur implicitly both at compile-time and runtime, converting a constant into another constant.
| Kind | Result |
|---|---|
undefined to flag enumeration | Interned instance whose value is zero (0). |
null to flag enumeration | Interned instance whose value is zero (0). |
undefined to T containing both undefined and null | undefined |
undefined to T containing undefined and no null | undefined |
undefined to T containing null and no undefined | null |
null to T containing undefined but not null | undefined |
null to T containing null but not undefined | null |
null to T containing both undefined or null | null |
Numeric constant to * or Object | Equivalent constant of the target type. |
String constant to * or Object or union containing String | Equivalent constant of the target type. |
Boolean constant to * or Object or union containing Boolean | Equivalent constant of the target type. |
Namespace constant to * or Object or union containing Namespace | Equivalent constant of the target type. |
Type constant to * or Object or union containing Class | Equivalent constant of the target type. |
| Numeric constant to another compatible numeric type | Numeric constant with value coerced to target type. |
| Numeric constant to union containing at least one compatible numeric type | Numeric constant of the target type containing value coerced to the containing numeric type, preferring the same numeric type or otherwise the first numeric type found. |
NaN to float | NaN |
-Infinity to float | -Infinity |
+Infinity to float | +Infinity |
Implicit coercion
Implicit coercions occur implicitly both at compile-time and runtime, after trying a constant coercion.
| Kind | Result |
|---|---|
From * | |
To * | |
| From numeric type to compatible numeric type | |
| To covariant (includes base classes, implemented interfaces, unions and inherited record type) | |
| From union to compatible union | |
| From union member to union | |
| From structural function type to another compatible function type |
Note:
interfacetypes inheritObject.
Explicit conversions
Explicit conversions occur when resolving v as T or T(v), after trying an implicit coercion.
| Kind | Result |
|---|---|
To contravariant (from interface to interface subtype, from class to subclass, or record type subtype) | |
| To union member | |
From * or Object to interface | |
To another [T] type | An array filtering out incompatible elements. |
String to enumeration | Identification of an enumeration variant by its String name. |
| Number to enumeration (using the same numeric type) | For regular enumerations, identifies a variant by its numeric value. For flag enumerations, identifies variant bits. |
To String | For undefined, returns "undefined"; for null, returns "null"; for other types, invokes toString(). |
To Boolean | Evaluates truthy value. |
To Number | Forced conversion to double-precision floating point. |
To float | Forced conversion to single-precision floating point. |
To decimal | Forced conversion to 128-bit decimal number. |
To int | Forced conversion to 32-bit signed integer. |
To uint | Forced conversion to 32-bit unsigned uninteger. |
To BigInt | Forced conversion to an arbitrary range integer. |
| Record type into equivalent record type of non-uniform field order | |
| From type parameter |
Note:
interfacetypes inheritObject.