Crate wast

A crate for low-level parsing of the WebAssembly text formats: WAT and WAST.

This crate is intended to be a low-level detail of the wat crate, providing a low-level parsing API for parsing WebAssembly text format structures. The API provided by this crate is very similar to syn and provides the ability to write customized parsers which may be an extension to the core WebAssembly text format. For more documentation see the parser module.

High-level Overview

This crate provides a few major pieces of functionality

• lexer - this is a raw lexer for the wasm text format. This is not customizable, but if you'd like to iterate over raw tokens this is the module for you. You likely won't use this much.

• parser - this is the workhorse of this crate. The parser module provides the Parse trait primarily and utilities around working with a Parser to parse streams of tokens.

• Module - this contains an Abstract Syntax Tree (AST) of the WebAssembly Text format (WAT) as well as the unofficial WAST format. This also has a Module::encode method to emit a module in its binary form.

Stability and WebAssembly Features

This crate provides support for many in-progress WebAssembly features such as reference types, multi-value, etc. Be sure to check out the documentation of the wast crate for policy information on crate stability vs WebAssembly Features. The tl;dr; version is that this crate will issue semver-non-breaking releases which will break the parsing of the text format. This crate, unlike wast, is expected to have numerous Rust public API changes, all of which will be accompanied with a semver-breaking release.

Compile-time Cargo features

This crate has a wasm-module feature which is turned on by default which includes all necessary support to parse full WebAssembly modules. If you don't need this (for example you're parsing your own s-expression format) then this feature can be disabled.

Modules

annotation	Common annotations used to parse WebAssembly text files.
kw	Common keyword used to parse WebAssembly text files.
lexer	Definition of a lexer for the WebAssembly text format.
parser	Traits for parsing the WebAssembly Text format

Macros

annotation	A macro, like custom_keyword, to create a type which can be used to parse/peek annotation directives.
custom_keyword	A macro to create a custom keyword parser.
custom_reserved	A macro for defining custom reserved symbols.

Structs

BlockType	Extra information associated with block-related instructions.
BrOnExn	Payload of the br_on_exn instruction
BrTableIndices	Extra information associated with the br_table instruction.
CallIndirect	Extra data associated with the call_indirect instruction.
Custom	A wasm custom section within a module.
Data	A data directive in a WebAssembly module.
Elem	An elem segment in a WebAssembly module.
Error	A convenience error type to tie together all the detailed errors produced by this crate.
Event	A WebAssembly event directive, part of the exception handling proposal.
Export	A entry in a WebAssembly module's export section.
Expression	An expression, or a list of instructions, in the WebAssembly text format.
Float32	A parsed floating-point type
Float64	A parsed floating-point type
Func	A WebAssembly function to be inserted into a module.
FunctionType	A function type with parameters and results.
GcOptIn	A WebAssembly GC opt-in directive, part of the GC prototype.
Global	A WebAssembly global in a module
GlobalType	Type for a global in a wasm module
Id	An identifier in a WebAssembly module, prefixed by $ in the textual format.
Import	An import statement and entry in a WebAssembly module.
InlineExport	A listing of inline (export "foo") statements on a WebAssembly item in its textual format.
LParen	A convenience type to use with Parser::peek to see if the next token is an s-expression.
Limits	Min/max limits used for tables/memories.
MemArg	Payload for memory-related instructions indicating offset/alignment of memory accesses.
Memory	A defined WebAssembly memory instance inside of a module.
MemoryInit	Extra data associated with the memory.init instruction
MemoryType	Configuration for a memory of a wasm module
Module	A parsed WebAssembly module.
NameAnnotation	An @name annotation in source, currently of the form @name "foo"
Names	Representation of the results of name resolution for a module.
SelectTypes	Payload of the select instructions
Span	A position in the original source stream, used to render errors.
StructAccess	Extra data associated with the struct.get/set instructions
StructField	A field of a struct type.
StructNarrow	Extra data associated with the struct.narrow instruction
StructType	A struct type with fields.
Table	A WebAssembly table directive in a module.
TableArg	Extra data associated with unary table instructions.
TableCopy	Extra data associated with the table.copy instruction.
TableInit	Extra data associated with the table.init instruction
TableType	Configuration for a table of a wasm mdoule
Type	A type declaration in a module
TypeUse	A reference to a type defined in this module.
V8x16Shuffle	Lanes being shuffled in the v8x16.shuffle instruction
Wast	A parsed representation of a *.wast file.
WastInvoke
Wat	A *.wat file parser, or a parser for one parenthesized module.

Enums

AssertExpression	An expression that is valid inside an assert_return directive.
CustomPlace	Possible locations to place a custom section within a module.
CustomPlaceAnchor	Known sections that custom sections can be placed relative to.
DataKind	Different kinds of data segments, either passive or active.
ElemKind	Different ways to define an element segment in an mdoule.
ElemPayload	Different ways to define the element segment payload in a module.
EventType	Listing of various types of events that can be defined in a wasm module.
ExportKind	Different kinds of elements that can be exported from a WebAssembly module, contained in an Export.
FuncKind	Possible ways to define a function in the text format.
GlobalKind	Different kinds of globals that can be defined in a module.
ImportKind	All possible types of items that can be imported into a wasm module.
Index	A reference to another item in a wasm module.
Instruction	A listing of all WebAssembly instructions that can be in a module that this crate currently parses.
MemoryKind	Different syntactical ways a memory can be defined in a module.
ModuleField	A listing of all possible fields that can make up a WebAssembly module.
ModuleKind	The different kinds of ways to define a module.
NanPattern	Either a NaN pattern (nan:canonical, nan:arithmetic) or a value of type T.
QuoteModule
TableElemType	List of different kinds of table types we can have.
TableKind	Different ways to textually define a table.
TypeDef	A definition of a type.
V128Pattern	A version of V128Const that allows NanPatterns.
V128Const	Different ways to specify a v128.const instruction
ValType	The value types for a wasm module.
WastDirective	The different kinds of directives found in a *.wast file.
WastExecute