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fibonacci1729 merged 1 commit into from
Dec 6, 2022
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WIT Syntax: world #83

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33 changes: 25 additions & 8 deletions design/mvp/WIT.md
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,9 @@ keyword ::= 'use'
| 'tuple'
| 'future'
| 'stream'
| 'world'
| 'import'
| 'export'
```

## Top-level items
Expand All @@ -122,20 +125,32 @@ readability but this isn't required.

Concretely, the structure of a `wit` document is:
```
wit-document ::= interface-item*
wit-document ::= (interface-item | world-item)*
```

## Item: `interface`
## Item: `world`

Interfaces can be defined in a `wit` document. Interfaces have a name and a sequence of items and functions.
Worlds define a [componenttype](https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#type-definitions) as a collection of imports and exports.

Concretely, the structure of a world is:

```wit
interface example {
thunk: func() -> ()
fibonacci: func(n: u32) -> u32
}
world-item ::= 'world' id '{' world-items* '}'

world-items ::= export-item | import-item

export-item ::= 'export' id ':' extern-type
import-item ::= 'import' id ':' extern-type

extern-type ::= ty | func-type | interface-type

interface-type ::= 'interface' '{' interface-items* '}'
```

## Item: `interface`

Interfaces can be defined in a `wit` document. Interfaces have a name and a sequence of items and functions.

Specifically interfaces have the structure:

```wit
Expand All @@ -151,7 +166,9 @@ interface-items ::= resource-item
| use-item
| func-item

func-item ::= id ':' 'func' param-list '->' result-list
func-item ::= id ':' func-type

func-type ::= 'func' param-list '->' result-list

param-list ::= '(' named-type-list ')'

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