Invalid type passed!
Received:
{type}
Expected one of:
{asideVariants.join(", ")}
: <>
{title &&
{title}
}
{children}
}
;
};
Tolk supports enums, similar to TypeScript and C++ enums.
In the [TVM](/tvm/overview), all enums are represented as integers. At the compiler level, an enum is a distinct type.
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
// will be 0 1 2
enum Color {
Red
Green
Blue
}
```
## Enum members
Values can be specified manually. Otherwise, they are auto-calculated as `+1`.
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
enum Mode {
Foo = 256,
Bar, // implicitly 257
}
```
## Enum types
Enums are distinct types, not integers. `Color.Red` has type `Color`, not `int`, although it holds the value `0` at runtime.
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
fun isRed(c: Color) {
return c == Color.Red
}
fun demo() {
isRed(Color.Blue); // ok
isRed(1); // error, pass `int` to `Color`
}
```
Since enums are types, they can be:
* used as variables and parameters,
* extended with methods,
* used in struct fields, unions, generics, and other type contexts.
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
struct Gradient {
from: Color
to: Color? = null
}
fun Color.isRed(self) {
return self == Color.Red
}
var g: Gradient = { from: Color.Blue };
g.from.isRed(); // false
Color.Red.isRed(); // true
match (g.to) {
null => ...
Color => ...
}
```
## Exhaustive pattern matching
[`match`](/languages/tolk/syntax/pattern-matching) on enums requires coverage of all cases:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
match (someColor) {
Color.Red => {}
Color.Green => {}
// error: Color.Blue is missing
}
```
Alternatively, use `else` to handle remaining values:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
match (someColor) {
Color.Red => {}
else => {}
}
```
Operator `==` compares values directly:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
if (someColor == Color.Red) {}
else {}
```
## Integer representation
At the TVM level, every enum is represented as `int`. Casting between the enum and `int` is allowed:
* `Color.Blue as int` evaluates to `2`;
* `2 as Color` evaluates to `Color.Blue`.
During deserialization with `fromCell()`, the compiler validates that encoded integers correspond to valid enum values.
## Usage in `throw` and `assert`
Enums are allowed in `throw` and `assert`:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
enum Err {
InvalidId = 0x100
TooHighId
}
fun validate(id: int) {
assert (id < 1000) throw Err.TooHighId; // excno = 257
}
```
## Stack layout and serialization
Every enum is [backed by TVM](/languages/tolk/types/overall-tvm-stack) `INT` and [serialized](/languages/tolk/types/overall-serialization) as `(u)intN`, where `N` is:
* specified manually, for example: `enum Role: int8 { ... }`;
* or calculated automatically to fit all values.