Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 5823 insertions, 0 deletions

diff --git a/third_party/rust/wast/src/component/alias.rs b/third_party/rust/wast/src/component/alias.rs
new file mode 100644
index 0000000000..3c70a2d371
--- /dev/null
+++ b/third_party/rust/wast/src/component/alias.rs
@@ -0,0 +1,253 @@
+use crate::core::ExportKind;
+use crate::kw;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::{Id, Index, NameAnnotation, Span};
+
+/// A inline alias for component exported items.
+#[derive(Debug)]
+pub struct InlineExportAlias<'a> {
+    /// The instance to alias the export from.
+    pub instance: Index<'a>,
+    /// The name of the export to alias.
+    pub name: &'a str,
+}
+
+impl<'a> Parse<'a> for InlineExportAlias<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::alias>()?;
+        parser.parse::<kw::export>()?;
+        let instance = parser.parse()?;
+        let name = parser.parse()?;
+        Ok(Self { instance, name })
+    }
+}
+
+/// An alias to a component item.
+#[derive(Debug)]
+pub struct Alias<'a> {
+    /// Where this `alias` was defined.
+    pub span: Span,
+    /// An identifier that this alias is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this alias stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// The target of this alias.
+    pub target: AliasTarget<'a>,
+}
+
+impl<'a> Alias<'a> {
+    /// Parses only an outer type alias.
+    pub fn parse_outer_core_type_alias(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::alias>()?.0;
+        parser.parse::<kw::outer>()?;
+        let outer = parser.parse()?;
+        let index = parser.parse()?;
+
+        let (kind, id, name) = parser.parens(|parser| {
+            let mut kind: ComponentOuterAliasKind = parser.parse()?;
+            match kind {
+                ComponentOuterAliasKind::CoreType => {
+                    return Err(parser.error("expected type for outer alias"))
+                }
+                ComponentOuterAliasKind::Type => {
+                    kind = ComponentOuterAliasKind::CoreType;
+                }
+                _ => return Err(parser.error("expected core type or type for outer alias")),
+            }
+
+            Ok((kind, parser.parse()?, parser.parse()?))
+        })?;
+
+        Ok(Self {
+            span,
+            target: AliasTarget::Outer { outer, index, kind },
+            id,
+            name,
+        })
+    }
+}
+
+impl<'a> Parse<'a> for Alias<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::alias>()?.0;
+
+        let mut l = parser.lookahead1();
+
+        let (target, id, name) = if l.peek::<kw::outer>() {
+            parser.parse::<kw::outer>()?;
+            let outer = parser.parse()?;
+            let index = parser.parse()?;
+            let (kind, id, name) =
+                parser.parens(|parser| Ok((parser.parse()?, parser.parse()?, parser.parse()?)))?;
+
+            (AliasTarget::Outer { outer, index, kind }, id, name)
+        } else if l.peek::<kw::export>() {
+            parser.parse::<kw::export>()?;
+            let instance = parser.parse()?;
+            let export_name = parser.parse()?;
+            let (kind, id, name) =
+                parser.parens(|parser| Ok((parser.parse()?, parser.parse()?, parser.parse()?)))?;
+
+            (
+                AliasTarget::Export {
+                    instance,
+                    name: export_name,
+                    kind,
+                },
+                id,
+                name,
+            )
+        } else if l.peek::<kw::core>() {
+            parser.parse::<kw::core>()?;
+            parser.parse::<kw::export>()?;
+            let instance = parser.parse()?;
+            let export_name = parser.parse()?;
+            let (kind, id, name) = parser.parens(|parser| {
+                parser.parse::<kw::core>()?;
+                Ok((parser.parse()?, parser.parse()?, parser.parse()?))
+            })?;
+
+            (
+                AliasTarget::CoreExport {
+                    instance,
+                    name: export_name,
+                    kind,
+                },
+                id,
+                name,
+            )
+        } else {
+            return Err(l.error());
+        };
+
+        Ok(Self {
+            span,
+            target,
+            id,
+            name,
+        })
+    }
+}
+
+/// Represents the kind of instance export alias.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum ComponentExportAliasKind {
+    /// The alias is to a core module export.
+    CoreModule,
+    /// The alias is to a function export.
+    Func,
+    /// The alias is to a value export.
+    Value,
+    /// The alias is to a type export.
+    Type,
+    /// The alias is to a component export.
+    Component,
+    /// The alias is to an instance export.
+    Instance,
+}
+
+impl<'a> Parse<'a> for ComponentExportAliasKind {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::core>() {
+            parser.parse::<kw::core>()?;
+            let mut l = parser.lookahead1();
+            if l.peek::<kw::module>() {
+                parser.parse::<kw::module>()?;
+                Ok(Self::CoreModule)
+            } else {
+                Err(l.error())
+            }
+        } else if l.peek::<kw::func>() {
+            parser.parse::<kw::func>()?;
+            Ok(Self::Func)
+        } else if l.peek::<kw::value>() {
+            parser.parse::<kw::value>()?;
+            Ok(Self::Value)
+        } else if l.peek::<kw::r#type>() {
+            parser.parse::<kw::r#type>()?;
+            Ok(Self::Type)
+        } else if l.peek::<kw::component>() {
+            parser.parse::<kw::component>()?;
+            Ok(Self::Component)
+        } else if l.peek::<kw::instance>() {
+            parser.parse::<kw::instance>()?;
+            Ok(Self::Instance)
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+/// Represents the kind of outer alias.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum ComponentOuterAliasKind {
+    /// The alias is to an outer core module.
+    CoreModule,
+    /// The alias is to an outer core type.
+    CoreType,
+    /// The alias is to an outer type.
+    Type,
+    /// The alias is to an outer component.
+    Component,
+}
+
+impl<'a> Parse<'a> for ComponentOuterAliasKind {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::core>() {
+            parser.parse::<kw::core>()?;
+            let mut l = parser.lookahead1();
+            if l.peek::<kw::module>() {
+                parser.parse::<kw::module>()?;
+                Ok(Self::CoreModule)
+            } else if l.peek::<kw::r#type>() {
+                parser.parse::<kw::r#type>()?;
+                Ok(Self::CoreType)
+            } else {
+                Err(l.error())
+            }
+        } else if l.peek::<kw::r#type>() {
+            parser.parse::<kw::r#type>()?;
+            Ok(Self::Type)
+        } else if l.peek::<kw::component>() {
+            parser.parse::<kw::component>()?;
+            Ok(Self::Component)
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+/// The target of a component alias.
+#[derive(Debug)]
+pub enum AliasTarget<'a> {
+    /// The alias is to an export of a component instance.
+    Export {
+        /// The component instance exporting the item.
+        instance: Index<'a>,
+        /// The name of the exported item to alias.
+        name: &'a str,
+        /// The export kind of the alias.
+        kind: ComponentExportAliasKind,
+    },
+    /// The alias is to an export of a module instance.
+    CoreExport {
+        /// The module instance exporting the item.
+        instance: Index<'a>,
+        /// The name of the exported item to alias.
+        name: &'a str,
+        /// The export kind of the alias.
+        kind: ExportKind,
+    },
+    /// The alias is to an item from an outer component.
+    Outer {
+        /// The number of enclosing components to skip.
+        outer: Index<'a>,
+        /// The index of the item being aliased.
+        index: Index<'a>,
+        /// The outer alias kind.
+        kind: ComponentOuterAliasKind,
+    },
+}
diff --git a/third_party/rust/wast/src/component/binary.rs b/third_party/rust/wast/src/component/binary.rs
new file mode 100644
index 0000000000..6d57ed4380
--- /dev/null
+++ b/third_party/rust/wast/src/component/binary.rs
@@ -0,0 +1,972 @@
+use crate::component::*;
+use crate::core;
+use crate::token::{Id, Index, NameAnnotation};
+use wasm_encoder::{
+    CanonicalFunctionSection, ComponentAliasSection, ComponentDefinedTypeEncoder,
+    ComponentExportSection, ComponentImportSection, ComponentInstanceSection, ComponentNameSection,
+    ComponentSection, ComponentSectionId, ComponentStartSection, ComponentTypeEncoder,
+    ComponentTypeSection, CoreTypeEncoder, CoreTypeSection, InstanceSection, NameMap,
+    NestedComponentSection, RawSection, SectionId,
+};
+
+pub fn encode(component: &Component<'_>) -> Vec<u8> {
+    match &component.kind {
+        ComponentKind::Text(fields) => {
+            encode_fields(&component.id, &component.name, fields).finish()
+        }
+        ComponentKind::Binary(bytes) => bytes.iter().flat_map(|b| b.iter().copied()).collect(),
+    }
+}
+
+fn encode_fields(
+    // TODO: use the id and name for a future names section
+    component_id: &Option<Id<'_>>,
+    component_name: &Option<NameAnnotation<'_>>,
+    fields: &[ComponentField<'_>],
+) -> wasm_encoder::Component {
+    let mut e = Encoder::default();
+
+    for field in fields {
+        match field {
+            ComponentField::CoreModule(m) => e.encode_core_module(m),
+            ComponentField::CoreInstance(i) => e.encode_core_instance(i),
+            ComponentField::CoreType(t) => e.encode_core_type(t),
+            ComponentField::Component(c) => e.encode_component(c),
+            ComponentField::Instance(i) => e.encode_instance(i),
+            ComponentField::Alias(a) => e.encode_alias(a),
+            ComponentField::Type(t) => e.encode_type(t),
+            ComponentField::CanonicalFunc(f) => e.encode_canonical_func(f),
+            ComponentField::CoreFunc(_) | ComponentField::Func(_) => {
+                unreachable!("should be expanded already")
+            }
+            ComponentField::Start(s) => e.encode_start(s),
+            ComponentField::Import(i) => e.encode_import(i),
+            ComponentField::Export(ex) => e.encode_export(ex),
+            ComponentField::Custom(c) => e.encode_custom(c),
+        }
+    }
+
+    e.flush(None);
+    e.encode_names(component_id, component_name);
+
+    e.component
+}
+
+fn encode_core_type(encoder: CoreTypeEncoder, ty: &CoreTypeDef) {
+    match ty {
+        CoreTypeDef::Def(core::TypeDef::Func(f)) => {
+            encoder.function(
+                f.params.iter().map(|(_, _, ty)| (*ty).into()),
+                f.results.iter().copied().map(Into::into),
+            );
+        }
+        CoreTypeDef::Def(core::TypeDef::Struct(_)) | CoreTypeDef::Def(core::TypeDef::Array(_)) => {
+            todo!("encoding of GC proposal types not yet implemented")
+        }
+        CoreTypeDef::Module(t) => {
+            encoder.module(&t.into());
+        }
+    }
+}
+
+fn encode_type(encoder: ComponentTypeEncoder, ty: &TypeDef) {
+    match ty {
+        TypeDef::Defined(t) => {
+            encode_defined_type(encoder.defined_type(), t);
+        }
+        TypeDef::Func(f) => {
+            let mut encoder = encoder.function();
+            encoder.params(f.params.iter().map(|p| (p.name, &p.ty)));
+
+            if f.results.len() == 1 && f.results[0].name.is_none() {
+                encoder.result(&f.results[0].ty);
+            } else {
+                encoder.results(f.results.iter().map(|r| (r.name.unwrap_or(""), &r.ty)));
+            }
+        }
+        TypeDef::Component(c) => {
+            encoder.component(&c.into());
+        }
+        TypeDef::Instance(i) => {
+            encoder.instance(&i.into());
+        }
+    }
+}
+
+fn encode_defined_type(encoder: ComponentDefinedTypeEncoder, ty: &ComponentDefinedType) {
+    match ty {
+        ComponentDefinedType::Primitive(p) => encoder.primitive((*p).into()),
+        ComponentDefinedType::Record(r) => {
+            encoder.record(r.fields.iter().map(|f| (f.name, &f.ty)));
+        }
+        ComponentDefinedType::Variant(v) => {
+            encoder.variant(v.cases.iter().map(|c| {
+                (
+                    c.name,
+                    c.ty.as_ref().map(Into::into),
+                    c.refines.as_ref().map(Into::into),
+                )
+            }));
+        }
+        ComponentDefinedType::List(l) => {
+            encoder.list(l.element.as_ref());
+        }
+        ComponentDefinedType::Tuple(t) => {
+            encoder.tuple(t.fields.iter());
+        }
+        ComponentDefinedType::Flags(f) => {
+            encoder.flags(f.names.iter().copied());
+        }
+        ComponentDefinedType::Enum(e) => {
+            encoder.enum_type(e.names.iter().copied());
+        }
+        ComponentDefinedType::Union(u) => encoder.union(u.types.iter()),
+        ComponentDefinedType::Option(o) => {
+            encoder.option(o.element.as_ref());
+        }
+        ComponentDefinedType::Result(e) => {
+            encoder.result(
+                e.ok.as_deref().map(Into::into),
+                e.err.as_deref().map(Into::into),
+            );
+        }
+    }
+}
+
+#[derive(Default)]
+struct Encoder<'a> {
+    component: wasm_encoder::Component,
+    current_section_id: Option<u8>,
+
+    // Core sections
+    // Note: module sections are written immediately
+    core_instances: InstanceSection,
+    core_types: CoreTypeSection,
+
+    // Component sections
+    // Note: custom, component, start sections are written immediately
+    instances: ComponentInstanceSection,
+    aliases: ComponentAliasSection,
+    types: ComponentTypeSection,
+    funcs: CanonicalFunctionSection,
+    imports: ComponentImportSection,
+    exports: ComponentExportSection,
+
+    core_func_names: Vec<Option<&'a str>>,
+    core_table_names: Vec<Option<&'a str>>,
+    core_memory_names: Vec<Option<&'a str>>,
+    core_global_names: Vec<Option<&'a str>>,
+    core_type_names: Vec<Option<&'a str>>,
+    core_module_names: Vec<Option<&'a str>>,
+    core_instance_names: Vec<Option<&'a str>>,
+    func_names: Vec<Option<&'a str>>,
+    value_names: Vec<Option<&'a str>>,
+    type_names: Vec<Option<&'a str>>,
+    component_names: Vec<Option<&'a str>>,
+    instance_names: Vec<Option<&'a str>>,
+}
+
+impl<'a> Encoder<'a> {
+    fn encode_custom(&mut self, custom: &Custom) {
+        // Flush any in-progress section before encoding the customs section
+        self.flush(None);
+        self.component.section(custom);
+    }
+
+    fn encode_core_module(&mut self, module: &CoreModule<'a>) {
+        // Flush any in-progress section before encoding the module
+        self.flush(None);
+
+        self.core_module_names
+            .push(get_name(&module.id, &module.name));
+
+        match &module.kind {
+            CoreModuleKind::Import { .. } => unreachable!("should be expanded already"),
+            CoreModuleKind::Inline { fields } => {
+                // TODO: replace this with a wasm-encoder based encoding (should return `wasm_encoder::Module`)
+                let data = crate::core::binary::encode(&module.id, &module.name, fields);
+                self.component.section(&RawSection {
+                    id: ComponentSectionId::CoreModule.into(),
+                    data: &data,
+                });
+            }
+        }
+    }
+
+    fn encode_core_instance(&mut self, instance: &CoreInstance<'a>) {
+        self.core_instance_names
+            .push(get_name(&instance.id, &instance.name));
+        match &instance.kind {
+            CoreInstanceKind::Instantiate { module, args } => {
+                self.core_instances.instantiate(
+                    module.into(),
+                    args.iter().map(|arg| (arg.name, (&arg.kind).into())),
+                );
+            }
+            CoreInstanceKind::BundleOfExports(exports) => {
+                self.core_instances.export_items(exports.iter().map(|e| {
+                    let (kind, index) = (&e.item).into();
+                    (e.name, kind, index)
+                }));
+            }
+        }
+
+        self.flush(Some(self.core_instances.id()));
+    }
+
+    fn encode_core_type(&mut self, ty: &CoreType<'a>) {
+        self.core_type_names.push(get_name(&ty.id, &ty.name));
+        encode_core_type(self.core_types.ty(), &ty.def);
+        self.flush(Some(self.core_types.id()));
+    }
+
+    fn encode_component(&mut self, component: &NestedComponent<'a>) {
+        self.component_names
+            .push(get_name(&component.id, &component.name));
+        // Flush any in-progress section before encoding the component
+        self.flush(None);
+
+        match &component.kind {
+            NestedComponentKind::Import { .. } => unreachable!("should be expanded already"),
+            NestedComponentKind::Inline(fields) => {
+                self.component
+                    .section(&NestedComponentSection(&encode_fields(
+                        &component.id,
+                        &component.name,
+                        fields,
+                    )));
+            }
+        }
+    }
+
+    fn encode_instance(&mut self, instance: &Instance<'a>) {
+        self.instance_names
+            .push(get_name(&instance.id, &instance.name));
+        match &instance.kind {
+            InstanceKind::Import { .. } => unreachable!("should be expanded already"),
+            InstanceKind::Instantiate { component, args } => {
+                self.instances.instantiate(
+                    component.into(),
+                    args.iter().map(|arg| {
+                        let (kind, index) = (&arg.kind).into();
+                        (arg.name, kind, index)
+                    }),
+                );
+            }
+            InstanceKind::BundleOfExports(exports) => {
+                self.instances.export_items(exports.iter().map(|e| {
+                    let (kind, index) = (&e.kind).into();
+                    (e.name, kind, index)
+                }));
+            }
+        }
+
+        self.flush(Some(self.instances.id()));
+    }
+
+    fn encode_alias(&mut self, alias: &Alias<'a>) {
+        let name = get_name(&alias.id, &alias.name);
+        self.aliases.alias((&alias.target).into());
+        match &alias.target {
+            AliasTarget::Export { kind, .. } => {
+                self.names_for_component_export_alias(*kind).push(name);
+            }
+            AliasTarget::CoreExport { kind, .. } => {
+                self.names_for_core_export_alias(*kind).push(name);
+            }
+            AliasTarget::Outer { kind, .. } => {
+                self.names_for_component_outer_alias(*kind).push(name);
+            }
+        }
+
+        self.flush(Some(self.aliases.id()));
+    }
+
+    fn encode_start(&mut self, start: &Start) {
+        // Flush any in-progress section before encoding the start section
+        self.flush(None);
+
+        self.component.section(&ComponentStartSection {
+            function_index: start.func.into(),
+            args: start.args.iter().map(|a| a.idx.into()).collect::<Vec<_>>(),
+            results: start.results.len() as u32,
+        });
+    }
+
+    fn encode_type(&mut self, ty: &Type<'a>) {
+        self.type_names.push(get_name(&ty.id, &ty.name));
+        encode_type(self.types.ty(), &ty.def);
+        self.flush(Some(self.types.id()));
+    }
+
+    fn encode_canonical_func(&mut self, func: &CanonicalFunc<'a>) {
+        let name = get_name(&func.id, &func.name);
+        match &func.kind {
+            CanonicalFuncKind::Lift { ty, info } => {
+                self.func_names.push(name);
+                self.funcs.lift(
+                    info.func.idx.into(),
+                    ty.into(),
+                    info.opts.iter().map(Into::into),
+                );
+            }
+            CanonicalFuncKind::Lower(info) => {
+                self.core_func_names.push(name);
+                self.funcs
+                    .lower(info.func.idx.into(), info.opts.iter().map(Into::into));
+            }
+        }
+
+        self.flush(Some(self.funcs.id()));
+    }
+
+    fn encode_import(&mut self, import: &ComponentImport<'a>) {
+        let name = get_name(&import.item.id, &import.item.name);
+        self.names_for_item_kind(&import.item.kind).push(name);
+        self.imports.import(
+            import.name,
+            import.url.unwrap_or(""),
+            (&import.item.kind).into(),
+        );
+        self.flush(Some(self.imports.id()));
+    }
+
+    fn encode_export(&mut self, export: &ComponentExport<'a>) {
+        let name = get_name(&export.id, &export.debug_name);
+        let (kind, index) = (&export.kind).into();
+        self.exports.export(
+            export.name,
+            export.url.unwrap_or(""),
+            kind,
+            index,
+            export.ty.as_ref().map(|ty| (&ty.0.kind).into()),
+        );
+        match &export.kind {
+            ComponentExportKind::CoreModule(_) => self.core_module_names.push(name),
+            ComponentExportKind::Func(_) => self.func_names.push(name),
+            ComponentExportKind::Instance(_) => self.instance_names.push(name),
+            ComponentExportKind::Value(_) => self.value_names.push(name),
+            ComponentExportKind::Component(_) => self.component_names.push(name),
+            ComponentExportKind::Type(_) => self.type_names.push(name),
+        }
+        self.flush(Some(self.exports.id()));
+    }
+
+    fn flush(&mut self, section_id: Option<u8>) {
+        if self.current_section_id == section_id {
+            return;
+        }
+
+        if let Some(id) = self.current_section_id {
+            match id {
+                // 0 => custom sections are written immediately
+                // 1 => core modules sections are written immediately
+                2 => {
+                    assert_eq!(id, self.core_instances.id());
+                    self.component.section(&self.core_instances);
+                    self.core_instances = Default::default();
+                }
+                3 => {
+                    assert_eq!(id, self.core_types.id());
+                    self.component.section(&self.core_types);
+                    self.core_types = Default::default();
+                }
+                // 4 => components sections are written immediately
+                5 => {
+                    assert_eq!(id, self.instances.id());
+                    self.component.section(&self.instances);
+                    self.instances = Default::default();
+                }
+                6 => {
+                    assert_eq!(id, self.aliases.id());
+                    self.component.section(&self.aliases);
+                    self.aliases = Default::default();
+                }
+                7 => {
+                    assert_eq!(id, self.types.id());
+                    self.component.section(&self.types);
+                    self.types = Default::default();
+                }
+                8 => {
+                    assert_eq!(id, self.funcs.id());
+                    self.component.section(&self.funcs);
+                    self.funcs = Default::default();
+                }
+                // 9 => start sections are written immediately
+                10 => {
+                    assert_eq!(id, self.imports.id());
+                    self.component.section(&self.imports);
+                    self.imports = Default::default();
+                }
+                11 => {
+                    assert_eq!(id, self.exports.id());
+                    self.component.section(&self.exports);
+                    self.exports = Default::default();
+                }
+                _ => unreachable!("unknown incremental component section id: {}", id),
+            }
+        }
+
+        self.current_section_id = section_id
+    }
+
+    fn encode_names(
+        &mut self,
+        component_id: &Option<Id<'_>>,
+        component_name: &Option<NameAnnotation<'_>>,
+    ) {
+        let mut names = ComponentNameSection::new();
+        if let Some(name) = get_name(component_id, component_name) {
+            names.component(name);
+        }
+
+        let mut funcs = |list: &[Option<&str>], append: fn(&mut ComponentNameSection, &NameMap)| {
+            let mut map = NameMap::new();
+            for (i, entry) in list.iter().enumerate() {
+                if let Some(name) = entry {
+                    map.append(i as u32, name);
+                }
+            }
+            if !map.is_empty() {
+                append(&mut names, &map);
+            }
+        };
+
+        funcs(&self.core_func_names, ComponentNameSection::core_funcs);
+        funcs(&self.core_table_names, ComponentNameSection::core_tables);
+        funcs(&self.core_memory_names, ComponentNameSection::core_memories);
+        funcs(&self.core_global_names, ComponentNameSection::core_globals);
+        funcs(&self.core_type_names, ComponentNameSection::core_types);
+        funcs(&self.core_module_names, ComponentNameSection::core_modules);
+        funcs(
+            &self.core_instance_names,
+            ComponentNameSection::core_instances,
+        );
+        funcs(&self.func_names, ComponentNameSection::funcs);
+        funcs(&self.value_names, ComponentNameSection::values);
+        funcs(&self.type_names, ComponentNameSection::types);
+        funcs(&self.component_names, ComponentNameSection::components);
+        funcs(&self.instance_names, ComponentNameSection::instances);
+
+        if !names.is_empty() {
+            self.component.section(&names);
+        }
+    }
+
+    fn names_for_component_export_alias(
+        &mut self,
+        kind: ComponentExportAliasKind,
+    ) -> &mut Vec<Option<&'a str>> {
+        match kind {
+            ComponentExportAliasKind::Func => &mut self.func_names,
+            ComponentExportAliasKind::CoreModule => &mut self.core_module_names,
+            ComponentExportAliasKind::Value => &mut self.value_names,
+            ComponentExportAliasKind::Type => &mut self.type_names,
+            ComponentExportAliasKind::Component => &mut self.component_names,
+            ComponentExportAliasKind::Instance => &mut self.instance_names,
+        }
+    }
+
+    fn names_for_component_outer_alias(
+        &mut self,
+        kind: ComponentOuterAliasKind,
+    ) -> &mut Vec<Option<&'a str>> {
+        match kind {
+            ComponentOuterAliasKind::CoreModule => &mut self.core_module_names,
+            ComponentOuterAliasKind::CoreType => &mut self.core_type_names,
+            ComponentOuterAliasKind::Component => &mut self.component_names,
+            ComponentOuterAliasKind::Type => &mut self.type_names,
+        }
+    }
+
+    fn names_for_core_export_alias(&mut self, kind: core::ExportKind) -> &mut Vec<Option<&'a str>> {
+        match kind {
+            core::ExportKind::Func => &mut self.core_func_names,
+            core::ExportKind::Global => &mut self.core_global_names,
+            core::ExportKind::Table => &mut self.core_table_names,
+            core::ExportKind::Memory => &mut self.core_memory_names,
+            core::ExportKind::Tag => unimplemented!(),
+        }
+    }
+
+    fn names_for_item_kind(&mut self, kind: &ItemSigKind) -> &mut Vec<Option<&'a str>> {
+        match kind {
+            ItemSigKind::CoreModule(_) => &mut self.core_module_names,
+            ItemSigKind::Func(_) => &mut self.func_names,
+            ItemSigKind::Component(_) => &mut self.component_names,
+            ItemSigKind::Instance(_) => &mut self.instance_names,
+            ItemSigKind::Value(_) => &mut self.value_names,
+            ItemSigKind::Type(_) => &mut self.type_names,
+        }
+    }
+}
+
+fn get_name<'a>(id: &Option<Id<'a>>, name: &Option<NameAnnotation<'a>>) -> Option<&'a str> {
+    name.as_ref().map(|n| n.name).or_else(|| {
+        id.and_then(|id| {
+            if id.is_gensym() {
+                None
+            } else {
+                Some(id.name())
+            }
+        })
+    })
+}
+
+// This implementation is much like `wasm_encoder::CustomSection`, except
+// that it extends via a list of slices instead of a single slice.
+impl wasm_encoder::Encode for Custom<'_> {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        let mut buf = [0u8; 5];
+        let encoded_name_len =
+            leb128::write::unsigned(&mut &mut buf[..], u64::try_from(self.name.len()).unwrap())
+                .unwrap();
+        let data_len = self.data.iter().fold(0, |acc, s| acc + s.len());
+
+        // name length
+        (encoded_name_len + self.name.len() + data_len).encode(sink);
+
+        // name
+        self.name.encode(sink);
+
+        // data
+        for s in &self.data {
+            sink.extend(*s);
+        }
+    }
+}
+
+impl wasm_encoder::ComponentSection for Custom<'_> {
+    fn id(&self) -> u8 {
+        SectionId::Custom.into()
+    }
+}
+
+// TODO: move these core conversion functions to the core module
+// once we update core encoding to use wasm-encoder.
+impl From<core::ValType<'_>> for wasm_encoder::ValType {
+    fn from(ty: core::ValType) -> Self {
+        match ty {
+            core::ValType::I32 => Self::I32,
+            core::ValType::I64 => Self::I64,
+            core::ValType::F32 => Self::F32,
+            core::ValType::F64 => Self::F64,
+            core::ValType::V128 => Self::V128,
+            core::ValType::Ref(r) => Self::Ref(r.into()),
+        }
+    }
+}
+
+impl From<core::RefType<'_>> for wasm_encoder::RefType {
+    fn from(r: core::RefType<'_>) -> Self {
+        wasm_encoder::RefType {
+            nullable: r.nullable,
+            heap_type: r.heap.into(),
+        }
+    }
+}
+
+impl From<core::HeapType<'_>> for wasm_encoder::HeapType {
+    fn from(r: core::HeapType<'_>) -> Self {
+        match r {
+            core::HeapType::Func => Self::Func,
+            core::HeapType::Extern => Self::Extern,
+            core::HeapType::Index(Index::Num(i, _)) => Self::TypedFunc(i),
+            core::HeapType::Index(_) => panic!("unresolved index"),
+            core::HeapType::Any
+            | core::HeapType::Eq
+            | core::HeapType::Struct
+            | core::HeapType::Array
+            | core::HeapType::NoFunc
+            | core::HeapType::NoExtern
+            | core::HeapType::None
+            | core::HeapType::I31 => {
+                todo!("encoding of GC proposal types not yet implemented")
+            }
+        }
+    }
+}
+
+impl From<&core::ItemKind<'_>> for wasm_encoder::EntityType {
+    fn from(kind: &core::ItemKind) -> Self {
+        match kind {
+            core::ItemKind::Func(t) => Self::Function(t.into()),
+            core::ItemKind::Table(t) => Self::Table((*t).into()),
+            core::ItemKind::Memory(t) => Self::Memory((*t).into()),
+            core::ItemKind::Global(t) => Self::Global((*t).into()),
+            core::ItemKind::Tag(t) => Self::Tag(t.into()),
+        }
+    }
+}
+
+impl From<core::TableType<'_>> for wasm_encoder::TableType {
+    fn from(ty: core::TableType) -> Self {
+        Self {
+            element_type: ty.elem.into(),
+            minimum: ty.limits.min,
+            maximum: ty.limits.max,
+        }
+    }
+}
+
+impl From<core::MemoryType> for wasm_encoder::MemoryType {
+    fn from(ty: core::MemoryType) -> Self {
+        let (minimum, maximum, memory64, shared) = match ty {
+            core::MemoryType::B32 { limits, shared } => {
+                (limits.min.into(), limits.max.map(Into::into), false, shared)
+            }
+            core::MemoryType::B64 { limits, shared } => (limits.min, limits.max, true, shared),
+        };
+
+        Self {
+            minimum,
+            maximum,
+            memory64,
+            shared,
+        }
+    }
+}
+
+impl From<core::GlobalType<'_>> for wasm_encoder::GlobalType {
+    fn from(ty: core::GlobalType) -> Self {
+        Self {
+            val_type: ty.ty.into(),
+            mutable: ty.mutable,
+        }
+    }
+}
+
+impl From<&core::TagType<'_>> for wasm_encoder::TagType {
+    fn from(ty: &core::TagType) -> Self {
+        match ty {
+            core::TagType::Exception(r) => Self {
+                kind: wasm_encoder::TagKind::Exception,
+                func_type_idx: r.into(),
+            },
+        }
+    }
+}
+
+impl<T: std::fmt::Debug> From<&core::TypeUse<'_, T>> for u32 {
+    fn from(u: &core::TypeUse<'_, T>) -> Self {
+        match &u.index {
+            Some(i) => (*i).into(),
+            None => unreachable!("unresolved type use in encoding: {:?}", u),
+        }
+    }
+}
+
+impl From<&CoreInstantiationArgKind<'_>> for wasm_encoder::ModuleArg {
+    fn from(kind: &CoreInstantiationArgKind) -> Self {
+        match kind {
+            CoreInstantiationArgKind::Instance(i) => {
+                wasm_encoder::ModuleArg::Instance(i.idx.into())
+            }
+            CoreInstantiationArgKind::BundleOfExports(..) => {
+                unreachable!("should be expanded already")
+            }
+        }
+    }
+}
+
+impl From<&CoreItemRef<'_, core::ExportKind>> for (wasm_encoder::ExportKind, u32) {
+    fn from(item: &CoreItemRef<'_, core::ExportKind>) -> Self {
+        match &item.kind {
+            core::ExportKind::Func => (wasm_encoder::ExportKind::Func, item.idx.into()),
+            core::ExportKind::Table => (wasm_encoder::ExportKind::Table, item.idx.into()),
+            core::ExportKind::Memory => (wasm_encoder::ExportKind::Memory, item.idx.into()),
+            core::ExportKind::Global => (wasm_encoder::ExportKind::Global, item.idx.into()),
+            core::ExportKind::Tag => (wasm_encoder::ExportKind::Tag, item.idx.into()),
+        }
+    }
+}
+
+impl From<core::ExportKind> for wasm_encoder::ExportKind {
+    fn from(kind: core::ExportKind) -> Self {
+        match kind {
+            core::ExportKind::Func => Self::Func,
+            core::ExportKind::Table => Self::Table,
+            core::ExportKind::Memory => Self::Memory,
+            core::ExportKind::Global => Self::Global,
+            core::ExportKind::Tag => Self::Tag,
+        }
+    }
+}
+
+impl From<Index<'_>> for u32 {
+    fn from(i: Index<'_>) -> Self {
+        match i {
+            Index::Num(i, _) => i,
+            Index::Id(_) => unreachable!("unresolved index in encoding: {:?}", i),
+        }
+    }
+}
+
+impl<T> From<&ItemRef<'_, T>> for u32 {
+    fn from(i: &ItemRef<'_, T>) -> Self {
+        assert!(i.export_names.is_empty());
+        i.idx.into()
+    }
+}
+
+impl<T> From<&CoreTypeUse<'_, T>> for u32 {
+    fn from(u: &CoreTypeUse<'_, T>) -> Self {
+        match u {
+            CoreTypeUse::Inline(_) => unreachable!("should be expanded already"),
+            CoreTypeUse::Ref(r) => r.idx.into(),
+        }
+    }
+}
+
+impl<T> From<&ComponentTypeUse<'_, T>> for u32 {
+    fn from(u: &ComponentTypeUse<'_, T>) -> Self {
+        match u {
+            ComponentTypeUse::Inline(_) => unreachable!("should be expanded already"),
+            ComponentTypeUse::Ref(r) => r.idx.into(),
+        }
+    }
+}
+
+impl From<&ComponentValType<'_>> for wasm_encoder::ComponentValType {
+    fn from(r: &ComponentValType) -> Self {
+        match r {
+            ComponentValType::Inline(ComponentDefinedType::Primitive(p)) => {
+                Self::Primitive((*p).into())
+            }
+            ComponentValType::Ref(i) => Self::Type(u32::from(*i)),
+            ComponentValType::Inline(_) => unreachable!("should be expanded by now"),
+        }
+    }
+}
+
+impl From<PrimitiveValType> for wasm_encoder::PrimitiveValType {
+    fn from(p: PrimitiveValType) -> Self {
+        match p {
+            PrimitiveValType::Bool => Self::Bool,
+            PrimitiveValType::S8 => Self::S8,
+            PrimitiveValType::U8 => Self::U8,
+            PrimitiveValType::S16 => Self::S16,
+            PrimitiveValType::U16 => Self::U16,
+            PrimitiveValType::S32 => Self::S32,
+            PrimitiveValType::U32 => Self::U32,
+            PrimitiveValType::S64 => Self::S64,
+            PrimitiveValType::U64 => Self::U64,
+            PrimitiveValType::Float32 => Self::Float32,
+            PrimitiveValType::Float64 => Self::Float64,
+            PrimitiveValType::Char => Self::Char,
+            PrimitiveValType::String => Self::String,
+        }
+    }
+}
+
+impl From<&Refinement<'_>> for u32 {
+    fn from(r: &Refinement) -> Self {
+        match r {
+            Refinement::Index(..) => unreachable!("should be resolved by now"),
+            Refinement::Resolved(i) => *i,
+        }
+    }
+}
+
+impl From<&ItemSigKind<'_>> for wasm_encoder::ComponentTypeRef {
+    fn from(k: &ItemSigKind) -> Self {
+        match k {
+            ItemSigKind::Component(c) => Self::Component(c.into()),
+            ItemSigKind::CoreModule(m) => Self::Module(m.into()),
+            ItemSigKind::Instance(i) => Self::Instance(i.into()),
+            ItemSigKind::Value(v) => Self::Value((&v.0).into()),
+            ItemSigKind::Func(f) => Self::Func(f.into()),
+            ItemSigKind::Type(TypeBounds::Eq(t)) => {
+                Self::Type(wasm_encoder::TypeBounds::Eq, (*t).into())
+            }
+        }
+    }
+}
+
+impl From<&ComponentType<'_>> for wasm_encoder::ComponentType {
+    fn from(ty: &ComponentType) -> Self {
+        let mut encoded = wasm_encoder::ComponentType::new();
+
+        for decl in &ty.decls {
+            match decl {
+                ComponentTypeDecl::CoreType(t) => {
+                    encode_core_type(encoded.core_type(), &t.def);
+                }
+                ComponentTypeDecl::Type(t) => {
+                    encode_type(encoded.ty(), &t.def);
+                }
+                ComponentTypeDecl::Alias(a) => {
+                    encoded.alias((&a.target).into());
+                }
+                ComponentTypeDecl::Import(i) => {
+                    encoded.import(i.name, i.url.unwrap_or(""), (&i.item.kind).into());
+                }
+                ComponentTypeDecl::Export(e) => {
+                    encoded.export(e.name, e.url.unwrap_or(""), (&e.item.kind).into());
+                }
+            }
+        }
+
+        encoded
+    }
+}
+
+impl From<&InstanceType<'_>> for wasm_encoder::InstanceType {
+    fn from(ty: &InstanceType) -> Self {
+        let mut encoded = wasm_encoder::InstanceType::new();
+
+        for decl in &ty.decls {
+            match decl {
+                InstanceTypeDecl::CoreType(t) => {
+                    encode_core_type(encoded.core_type(), &t.def);
+                }
+                InstanceTypeDecl::Type(t) => {
+                    encode_type(encoded.ty(), &t.def);
+                }
+                InstanceTypeDecl::Alias(a) => {
+                    encoded.alias((&a.target).into());
+                }
+                InstanceTypeDecl::Export(e) => {
+                    encoded.export(e.name, e.url.unwrap_or(""), (&e.item.kind).into());
+                }
+            }
+        }
+
+        encoded
+    }
+}
+
+impl From<&ModuleType<'_>> for wasm_encoder::ModuleType {
+    fn from(ty: &ModuleType) -> Self {
+        let mut encoded = wasm_encoder::ModuleType::new();
+
+        for decl in &ty.decls {
+            match decl {
+                ModuleTypeDecl::Type(t) => match &t.def {
+                    core::TypeDef::Func(f) => encoded.ty().function(
+                        f.params.iter().map(|(_, _, ty)| (*ty).into()),
+                        f.results.iter().copied().map(Into::into),
+                    ),
+                    core::TypeDef::Struct(_) | core::TypeDef::Array(_) => {
+                        todo!("encoding of GC proposal types not yet implemented")
+                    }
+                },
+                ModuleTypeDecl::Alias(a) => match &a.target {
+                    AliasTarget::Outer {
+                        outer,
+                        index,
+                        kind: ComponentOuterAliasKind::CoreType,
+                    } => {
+                        encoded.alias_outer_core_type(u32::from(*outer), u32::from(*index));
+                    }
+                    _ => unreachable!("only outer type aliases are supported"),
+                },
+                ModuleTypeDecl::Import(i) => {
+                    encoded.import(i.module, i.field, (&i.item.kind).into());
+                }
+                ModuleTypeDecl::Export(name, item) => {
+                    encoded.export(name, (&item.kind).into());
+                }
+            }
+        }
+
+        encoded
+    }
+}
+
+impl From<&InstantiationArgKind<'_>> for (wasm_encoder::ComponentExportKind, u32) {
+    fn from(kind: &InstantiationArgKind) -> Self {
+        match kind {
+            InstantiationArgKind::Item(i) => i.into(),
+            InstantiationArgKind::BundleOfExports(..) => unreachable!("should be expanded already"),
+        }
+    }
+}
+
+impl From<&ComponentExportKind<'_>> for (wasm_encoder::ComponentExportKind, u32) {
+    fn from(kind: &ComponentExportKind) -> Self {
+        match kind {
+            ComponentExportKind::CoreModule(m) => {
+                (wasm_encoder::ComponentExportKind::Module, m.idx.into())
+            }
+            ComponentExportKind::Func(f) => (wasm_encoder::ComponentExportKind::Func, f.idx.into()),
+            ComponentExportKind::Value(v) => {
+                (wasm_encoder::ComponentExportKind::Value, v.idx.into())
+            }
+            ComponentExportKind::Type(t) => (wasm_encoder::ComponentExportKind::Type, t.idx.into()),
+            ComponentExportKind::Component(c) => {
+                (wasm_encoder::ComponentExportKind::Component, c.idx.into())
+            }
+            ComponentExportKind::Instance(i) => {
+                (wasm_encoder::ComponentExportKind::Instance, i.idx.into())
+            }
+        }
+    }
+}
+
+impl From<ComponentOuterAliasKind> for wasm_encoder::ComponentOuterAliasKind {
+    fn from(kind: ComponentOuterAliasKind) -> Self {
+        match kind {
+            ComponentOuterAliasKind::CoreModule => Self::CoreModule,
+            ComponentOuterAliasKind::CoreType => Self::CoreType,
+            ComponentOuterAliasKind::Type => Self::Type,
+            ComponentOuterAliasKind::Component => Self::Component,
+        }
+    }
+}
+
+impl From<ComponentExportAliasKind> for wasm_encoder::ComponentExportKind {
+    fn from(kind: ComponentExportAliasKind) -> Self {
+        match kind {
+            ComponentExportAliasKind::CoreModule => Self::Module,
+            ComponentExportAliasKind::Func => Self::Func,
+            ComponentExportAliasKind::Value => Self::Value,
+            ComponentExportAliasKind::Type => Self::Type,
+            ComponentExportAliasKind::Component => Self::Component,
+            ComponentExportAliasKind::Instance => Self::Instance,
+        }
+    }
+}
+
+impl From<&CanonOpt<'_>> for wasm_encoder::CanonicalOption {
+    fn from(opt: &CanonOpt) -> Self {
+        match opt {
+            CanonOpt::StringUtf8 => Self::UTF8,
+            CanonOpt::StringUtf16 => Self::UTF16,
+            CanonOpt::StringLatin1Utf16 => Self::CompactUTF16,
+            CanonOpt::Memory(m) => Self::Memory(m.idx.into()),
+            CanonOpt::Realloc(f) => Self::Realloc(f.idx.into()),
+            CanonOpt::PostReturn(f) => Self::PostReturn(f.idx.into()),
+        }
+    }
+}
+
+impl<'a> From<&AliasTarget<'a>> for wasm_encoder::Alias<'a> {
+    fn from(target: &AliasTarget<'a>) -> Self {
+        match target {
+            AliasTarget::Export {
+                instance,
+                name,
+                kind,
+            } => wasm_encoder::Alias::InstanceExport {
+                instance: (*instance).into(),
+                kind: (*kind).into(),
+                name,
+            },
+            AliasTarget::CoreExport {
+                instance,
+                name,
+                kind,
+            } => wasm_encoder::Alias::CoreInstanceExport {
+                instance: (*instance).into(),
+                kind: (*kind).into(),
+                name,
+            },
+            AliasTarget::Outer { outer, index, kind } => wasm_encoder::Alias::Outer {
+                count: (*outer).into(),
+                kind: (*kind).into(),
+                index: (*index).into(),
+            },
+        }
+    }
+}
diff --git a/third_party/rust/wast/src/component/component.rs b/third_party/rust/wast/src/component/component.rs
new file mode 100644
index 0000000000..8424e083b8
--- /dev/null
+++ b/third_party/rust/wast/src/component/component.rs
@@ -0,0 +1,313 @@
+use crate::annotation;
+use crate::component::*;
+use crate::kw;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::Index;
+use crate::token::{Id, NameAnnotation, Span};
+
+/// A parsed WebAssembly component module.
+#[derive(Debug)]
+pub struct Component<'a> {
+    /// Where this `component` was defined
+    pub span: Span,
+    /// An optional identifier this component is known by
+    pub id: Option<Id<'a>>,
+    /// An optional `@name` annotation for this component
+    pub name: Option<NameAnnotation<'a>>,
+    /// What kind of component this was parsed as.
+    pub kind: ComponentKind<'a>,
+}
+
+/// The different kinds of ways to define a component.
+#[derive(Debug)]
+pub enum ComponentKind<'a> {
+    /// A component defined in the textual s-expression format.
+    Text(Vec<ComponentField<'a>>),
+    /// A component that had its raw binary bytes defined via the `binary`
+    /// directive.
+    Binary(Vec<&'a [u8]>),
+}
+
+impl<'a> Component<'a> {
+    /// Performs a name resolution pass on this [`Component`], resolving all
+    /// symbolic names to indices.
+    ///
+    /// The WAT format contains a number of shorthands to make it easier to
+    /// write, such as inline exports, inline imports, inline type definitions,
+    /// etc. Additionally it allows using symbolic names such as `$foo` instead
+    /// of using indices. This module will postprocess an AST to remove all of
+    /// this syntactic sugar, preparing the AST for binary emission.  This is
+    /// where expansion and name resolution happens.
+    ///
+    /// This function will mutate the AST of this [`Component`] and replace all
+    /// [`Index`](crate::token::Index) arguments with `Index::Num`. This will
+    /// also expand inline exports/imports listed on fields and handle various
+    /// other shorthands of the text format.
+    ///
+    /// If successful the AST was modified to be ready for binary encoding.
+    ///
+    /// # Errors
+    ///
+    /// If an error happens during resolution, such a name resolution error or
+    /// items are found in the wrong order, then an error is returned.
+    pub fn resolve(&mut self) -> std::result::Result<(), crate::Error> {
+        match &mut self.kind {
+            ComponentKind::Text(fields) => {
+                crate::component::expand::expand(fields);
+            }
+            ComponentKind::Binary(_) => {}
+        }
+        crate::component::resolve::resolve(self)
+    }
+
+    /// Encodes this [`Component`] to its binary form.
+    ///
+    /// This function will take the textual representation in [`Component`] and
+    /// perform all steps necessary to convert it to a binary WebAssembly
+    /// component, suitable for writing to a `*.wasm` file. This function may
+    /// internally modify the [`Component`], for example:
+    ///
+    /// * Name resolution is performed to ensure that `Index::Id` isn't present
+    ///   anywhere in the AST.
+    ///
+    /// * Inline shorthands such as imports/exports/types are all expanded to be
+    ///   dedicated fields of the component.
+    ///
+    /// * Component fields may be shuffled around to preserve index ordering from
+    ///   expansions.
+    ///
+    /// After all of this expansion has happened the component will be converted to
+    /// its binary form and returned as a `Vec<u8>`. This is then suitable to
+    /// hand off to other wasm runtimes and such.
+    ///
+    /// # Errors
+    ///
+    /// This function can return an error for name resolution errors and other
+    /// expansion-related errors.
+    pub fn encode(&mut self) -> std::result::Result<Vec<u8>, crate::Error> {
+        self.resolve()?;
+        Ok(crate::component::binary::encode(self))
+    }
+
+    pub(crate) fn validate(&self, parser: Parser<'_>) -> Result<()> {
+        let mut starts = 0;
+        if let ComponentKind::Text(fields) = &self.kind {
+            for item in fields.iter() {
+                if let ComponentField::Start(_) = item {
+                    starts += 1;
+                }
+            }
+        }
+        if starts > 1 {
+            return Err(parser.error("multiple start sections found"));
+        }
+        Ok(())
+    }
+}
+
+impl<'a> Parse<'a> for Component<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let _r = parser.register_annotation("custom");
+
+        let span = parser.parse::<kw::component>()?.0;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+
+        let kind = if parser.peek::<kw::binary>() {
+            parser.parse::<kw::binary>()?;
+            let mut data = Vec::new();
+            while !parser.is_empty() {
+                data.push(parser.parse()?);
+            }
+            ComponentKind::Binary(data)
+        } else {
+            ComponentKind::Text(ComponentField::parse_remaining(parser)?)
+        };
+        Ok(Component {
+            span,
+            id,
+            name,
+            kind,
+        })
+    }
+}
+
+/// A listing of all possible fields that can make up a WebAssembly component.
+#[allow(missing_docs)]
+#[derive(Debug)]
+pub enum ComponentField<'a> {
+    CoreModule(CoreModule<'a>),
+    CoreInstance(CoreInstance<'a>),
+    CoreType(CoreType<'a>),
+    Component(NestedComponent<'a>),
+    Instance(Instance<'a>),
+    Alias(Alias<'a>),
+    Type(Type<'a>),
+    CanonicalFunc(CanonicalFunc<'a>),
+    CoreFunc(CoreFunc<'a>), // Supports inverted forms of other items
+    Func(Func<'a>),         // Supports inverted forms of other items
+    Start(Start<'a>),
+    Import(ComponentImport<'a>),
+    Export(ComponentExport<'a>),
+    Custom(Custom<'a>),
+}
+
+impl<'a> ComponentField<'a> {
+    fn parse_remaining(parser: Parser<'a>) -> Result<Vec<ComponentField>> {
+        let mut fields = Vec::new();
+        while !parser.is_empty() {
+            fields.push(parser.parens(ComponentField::parse)?);
+        }
+        Ok(fields)
+    }
+}
+
+impl<'a> Parse<'a> for ComponentField<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<kw::core>() {
+            if parser.peek2::<kw::module>() {
+                return Ok(Self::CoreModule(parser.parse()?));
+            }
+            if parser.peek2::<kw::instance>() {
+                return Ok(Self::CoreInstance(parser.parse()?));
+            }
+            if parser.peek2::<kw::r#type>() {
+                return Ok(Self::CoreType(parser.parse()?));
+            }
+            if parser.peek2::<kw::func>() {
+                return Ok(Self::CoreFunc(parser.parse()?));
+            }
+        } else {
+            if parser.peek::<kw::component>() {
+                return Ok(Self::Component(parser.parse()?));
+            }
+            if parser.peek::<kw::instance>() {
+                return Ok(Self::Instance(parser.parse()?));
+            }
+            if parser.peek::<kw::alias>() {
+                return Ok(Self::Alias(parser.parse()?));
+            }
+            if parser.peek::<kw::r#type>() {
+                return Ok(Self::Type(parser.parse()?));
+            }
+            if parser.peek::<kw::import>() {
+                return Ok(Self::Import(parser.parse()?));
+            }
+            if parser.peek::<kw::func>() {
+                return Ok(Self::Func(parser.parse()?));
+            }
+            if parser.peek::<kw::export>() {
+                return Ok(Self::Export(parser.parse()?));
+            }
+            if parser.peek::<kw::start>() {
+                return Ok(Self::Start(parser.parse()?));
+            }
+            if parser.peek::<annotation::custom>() {
+                return Ok(Self::Custom(parser.parse()?));
+            }
+        }
+        Err(parser.error("expected valid component field"))
+    }
+}
+
+/// A function to call at instantiation time.
+#[derive(Debug)]
+pub struct Start<'a> {
+    /// The function to call.
+    pub func: Index<'a>,
+    /// The arguments to pass to the function.
+    pub args: Vec<ItemRef<'a, kw::value>>,
+    /// Names of the result values.
+    pub results: Vec<Option<Id<'a>>>,
+}
+
+impl<'a> Parse<'a> for Start<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::start>()?;
+        let func = parser.parse()?;
+        let mut args = Vec::new();
+        while !parser.is_empty() && !parser.peek2::<kw::result>() {
+            args.push(parser.parens(|parser| parser.parse())?);
+        }
+
+        let mut results = Vec::new();
+        while !parser.is_empty() && parser.peek2::<kw::result>() {
+            results.push(parser.parens(|parser| {
+                parser.parse::<kw::result>()?;
+                parser.parens(|parser| {
+                    parser.parse::<kw::value>()?;
+                    parser.parse()
+                })
+            })?);
+        }
+
+        Ok(Start {
+            func,
+            args,
+            results,
+        })
+    }
+}
+
+/// A nested WebAssembly component.
+#[derive(Debug)]
+pub struct NestedComponent<'a> {
+    /// Where this `component` was defined
+    pub span: Span,
+    /// An optional identifier this component is known by
+    pub id: Option<Id<'a>>,
+    /// An optional `@name` annotation for this component
+    pub name: Option<NameAnnotation<'a>>,
+    /// If present, inline export annotations which indicate names this
+    /// definition should be exported under.
+    pub exports: InlineExport<'a>,
+    /// What kind of component this was parsed as.
+    pub kind: NestedComponentKind<'a>,
+}
+
+/// The different kinds of ways to define a nested component.
+#[derive(Debug)]
+pub enum NestedComponentKind<'a> {
+    /// This is actually an inline import of a component
+    Import {
+        /// The information about where this is being imported from.
+        import: InlineImport<'a>,
+        /// The type of component being imported.
+        ty: ComponentTypeUse<'a, ComponentType<'a>>,
+    },
+    /// The component is defined inline as a local definition with its fields
+    /// listed here.
+    Inline(Vec<ComponentField<'a>>),
+}
+
+impl<'a> Parse<'a> for NestedComponent<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.depth_check()?;
+
+        let span = parser.parse::<kw::component>()?.0;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let exports = parser.parse()?;
+
+        let kind = if let Some(import) = parser.parse()? {
+            NestedComponentKind::Import {
+                import,
+                ty: parser.parse()?,
+            }
+        } else {
+            let mut fields = Vec::new();
+            while !parser.is_empty() {
+                fields.push(parser.parens(|p| p.parse())?);
+            }
+            NestedComponentKind::Inline(fields)
+        };
+
+        Ok(NestedComponent {
+            span,
+            id,
+            name,
+            exports,
+            kind,
+        })
+    }
+}
diff --git a/third_party/rust/wast/src/component/custom.rs b/third_party/rust/wast/src/component/custom.rs
new file mode 100644
index 0000000000..b17a7fafb4
--- /dev/null
+++ b/third_party/rust/wast/src/component/custom.rs
@@ -0,0 +1,28 @@
+use crate::annotation;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::Span;
+
+/// A custom section within a component.
+#[derive(Debug)]
+pub struct Custom<'a> {
+    /// Where this `@custom` was defined.
+    pub span: Span,
+
+    /// Name of the custom section.
+    pub name: &'a str,
+
+    /// Payload of this custom section.
+    pub data: Vec<&'a [u8]>,
+}
+
+impl<'a> Parse<'a> for Custom<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<annotation::custom>()?.0;
+        let name = parser.parse()?;
+        let mut data = Vec::new();
+        while !parser.is_empty() {
+            data.push(parser.parse()?);
+        }
+        Ok(Self { span, name, data })
+    }
+}
diff --git a/third_party/rust/wast/src/component/expand.rs b/third_party/rust/wast/src/component/expand.rs
new file mode 100644
index 0000000000..2bf0b529e4
--- /dev/null
+++ b/third_party/rust/wast/src/component/expand.rs
@@ -0,0 +1,859 @@
+use crate::component::*;
+use crate::core;
+use crate::gensym;
+use crate::kw;
+use crate::token::Id;
+use crate::token::{Index, Span};
+use std::collections::HashMap;
+use std::mem;
+
+/// Performs an AST "expansion" pass over the component fields provided.
+///
+/// This expansion is intended to desugar the AST from various parsed constructs
+/// to bits and bobs amenable for name resolution as well as binary encoding.
+/// For example `(import "i" (func))` is split into a type definition followed by
+/// the import referencing that type definition.
+///
+/// Most forms of AST expansion happen in this file and afterwards the AST will
+/// be handed to the name resolution pass which will convert `Index::Id` to
+/// `Index::Num` wherever it's found.
+pub fn expand(fields: &mut Vec<ComponentField<'_>>) {
+    Expander::default().expand_component_fields(fields)
+}
+
+enum AnyType<'a> {
+    Core(CoreType<'a>),
+    Component(Type<'a>),
+}
+
+impl<'a> From<AnyType<'a>> for ComponentTypeDecl<'a> {
+    fn from(t: AnyType<'a>) -> Self {
+        match t {
+            AnyType::Core(t) => Self::CoreType(t),
+            AnyType::Component(t) => Self::Type(t),
+        }
+    }
+}
+
+impl<'a> From<AnyType<'a>> for InstanceTypeDecl<'a> {
+    fn from(t: AnyType<'a>) -> Self {
+        match t {
+            AnyType::Core(t) => Self::CoreType(t),
+            AnyType::Component(t) => Self::Type(t),
+        }
+    }
+}
+
+impl<'a> From<AnyType<'a>> for ComponentField<'a> {
+    fn from(t: AnyType<'a>) -> Self {
+        match t {
+            AnyType::Core(t) => Self::CoreType(t),
+            AnyType::Component(t) => Self::Type(t),
+        }
+    }
+}
+
+#[derive(Default)]
+struct Expander<'a> {
+    /// Fields, during processing, which should be prepended to the
+    /// currently-being-processed field. This should always be empty after
+    /// processing is complete.
+    types_to_prepend: Vec<AnyType<'a>>,
+    component_fields_to_prepend: Vec<ComponentField<'a>>,
+
+    /// Fields that are appended to the end of the module once everything has
+    /// finished.
+    component_fields_to_append: Vec<ComponentField<'a>>,
+}
+
+impl<'a> Expander<'a> {
+    fn expand_component_fields(&mut self, fields: &mut Vec<ComponentField<'a>>) {
+        let mut cur = 0;
+        while cur < fields.len() {
+            self.expand_field(&mut fields[cur]);
+            let amt = self.types_to_prepend.len() + self.component_fields_to_prepend.len();
+            fields.splice(cur..cur, self.component_fields_to_prepend.drain(..));
+            fields.splice(cur..cur, self.types_to_prepend.drain(..).map(Into::into));
+            cur += 1 + amt;
+        }
+        fields.append(&mut self.component_fields_to_append);
+    }
+
+    fn expand_decls<T>(&mut self, decls: &mut Vec<T>, expand: fn(&mut Self, &mut T))
+    where
+        T: From<AnyType<'a>>,
+    {
+        let mut cur = 0;
+        while cur < decls.len() {
+            expand(self, &mut decls[cur]);
+            assert!(self.component_fields_to_prepend.is_empty());
+            assert!(self.component_fields_to_append.is_empty());
+            let amt = self.types_to_prepend.len();
+            decls.splice(cur..cur, self.types_to_prepend.drain(..).map(From::from));
+            cur += 1 + amt;
+        }
+    }
+
+    fn expand_field(&mut self, item: &mut ComponentField<'a>) {
+        let expanded = match item {
+            ComponentField::CoreModule(m) => self.expand_core_module(m),
+            ComponentField::CoreInstance(i) => {
+                self.expand_core_instance(i);
+                None
+            }
+            ComponentField::CoreType(t) => {
+                self.expand_core_type(t);
+                None
+            }
+            ComponentField::Component(c) => self.expand_nested_component(c),
+            ComponentField::Instance(i) => self.expand_instance(i),
+            ComponentField::Type(t) => {
+                self.expand_type(t);
+                None
+            }
+            ComponentField::CanonicalFunc(f) => {
+                self.expand_canonical_func(f);
+                None
+            }
+            ComponentField::CoreFunc(f) => self.expand_core_func(f),
+            ComponentField::Func(f) => self.expand_func(f),
+            ComponentField::Import(i) => {
+                self.expand_item_sig(&mut i.item);
+                None
+            }
+            ComponentField::Export(e) => {
+                if let Some(sig) = &mut e.ty {
+                    self.expand_item_sig(&mut sig.0);
+                }
+                None
+            }
+            ComponentField::Start(_) | ComponentField::Alias(_) | ComponentField::Custom(_) => None,
+        };
+
+        if let Some(expanded) = expanded {
+            *item = expanded;
+        }
+    }
+
+    fn expand_core_module(&mut self, module: &mut CoreModule<'a>) -> Option<ComponentField<'a>> {
+        for (name, url) in module.exports.names.drain(..) {
+            let id = gensym::fill(module.span, &mut module.id);
+            self.component_fields_to_append
+                .push(ComponentField::Export(ComponentExport {
+                    span: module.span,
+                    id: None,
+                    debug_name: None,
+                    name,
+                    url,
+                    kind: ComponentExportKind::module(module.span, id),
+                    ty: None,
+                }));
+        }
+        match &mut module.kind {
+            // inline modules are expanded later during resolution
+            CoreModuleKind::Inline { .. } => None,
+            CoreModuleKind::Import { import, ty } => {
+                let idx = self.expand_core_type_use(ty);
+                Some(ComponentField::Import(ComponentImport {
+                    span: module.span,
+                    name: import.name,
+                    url: import.url,
+                    item: ItemSig {
+                        span: module.span,
+                        id: module.id,
+                        name: None,
+                        kind: ItemSigKind::CoreModule(CoreTypeUse::Ref(idx)),
+                    },
+                }))
+            }
+        }
+    }
+
+    fn expand_core_instance(&mut self, instance: &mut CoreInstance<'a>) {
+        match &mut instance.kind {
+            CoreInstanceKind::Instantiate { args, .. } => {
+                for arg in args {
+                    self.expand_core_instantiation_arg(&mut arg.kind);
+                }
+            }
+            CoreInstanceKind::BundleOfExports { .. } => {}
+        }
+    }
+
+    fn expand_nested_component(
+        &mut self,
+        component: &mut NestedComponent<'a>,
+    ) -> Option<ComponentField<'a>> {
+        for (name, url) in component.exports.names.drain(..) {
+            let id = gensym::fill(component.span, &mut component.id);
+            self.component_fields_to_append
+                .push(ComponentField::Export(ComponentExport {
+                    span: component.span,
+                    id: None,
+                    debug_name: None,
+                    name,
+                    url,
+                    kind: ComponentExportKind::component(component.span, id),
+                    ty: None,
+                }));
+        }
+        match &mut component.kind {
+            NestedComponentKind::Inline(fields) => {
+                expand(fields);
+                None
+            }
+            NestedComponentKind::Import { import, ty } => {
+                let idx = self.expand_component_type_use(ty);
+                Some(ComponentField::Import(ComponentImport {
+                    span: component.span,
+                    name: import.name,
+                    url: import.url,
+                    item: ItemSig {
+                        span: component.span,
+                        id: component.id,
+                        name: None,
+                        kind: ItemSigKind::Component(ComponentTypeUse::Ref(idx)),
+                    },
+                }))
+            }
+        }
+    }
+
+    fn expand_instance(&mut self, instance: &mut Instance<'a>) -> Option<ComponentField<'a>> {
+        for (name, url) in instance.exports.names.drain(..) {
+            let id = gensym::fill(instance.span, &mut instance.id);
+            self.component_fields_to_append
+                .push(ComponentField::Export(ComponentExport {
+                    span: instance.span,
+                    id: None,
+                    debug_name: None,
+                    name,
+                    url,
+                    kind: ComponentExportKind::instance(instance.span, id),
+                    ty: None,
+                }));
+        }
+        match &mut instance.kind {
+            InstanceKind::Import { import, ty } => {
+                let idx = self.expand_component_type_use(ty);
+                Some(ComponentField::Import(ComponentImport {
+                    span: instance.span,
+                    name: import.name,
+                    url: import.url,
+                    item: ItemSig {
+                        span: instance.span,
+                        id: instance.id,
+                        name: None,
+                        kind: ItemSigKind::Instance(ComponentTypeUse::Ref(idx)),
+                    },
+                }))
+            }
+            InstanceKind::Instantiate { args, .. } => {
+                for arg in args {
+                    self.expand_instantiation_arg(&mut arg.kind);
+                }
+                None
+            }
+            InstanceKind::BundleOfExports { .. } => None,
+        }
+    }
+
+    fn expand_canonical_func(&mut self, func: &mut CanonicalFunc<'a>) {
+        match &mut func.kind {
+            CanonicalFuncKind::Lift { ty, .. } => {
+                self.expand_component_type_use(ty);
+            }
+            CanonicalFuncKind::Lower(_) => {}
+        }
+    }
+
+    fn expand_core_func(&mut self, func: &mut CoreFunc<'a>) -> Option<ComponentField<'a>> {
+        match &mut func.kind {
+            CoreFuncKind::Alias(a) => Some(ComponentField::Alias(Alias {
+                span: func.span,
+                id: func.id,
+                name: func.name,
+                target: AliasTarget::CoreExport {
+                    instance: a.instance,
+                    name: a.name,
+                    kind: core::ExportKind::Func,
+                },
+            })),
+            CoreFuncKind::Lower(info) => Some(ComponentField::CanonicalFunc(CanonicalFunc {
+                span: func.span,
+                id: func.id,
+                name: func.name,
+                kind: CanonicalFuncKind::Lower(mem::take(info)),
+            })),
+        }
+    }
+
+    fn expand_func(&mut self, func: &mut Func<'a>) -> Option<ComponentField<'a>> {
+        for (name, url) in func.exports.names.drain(..) {
+            let id = gensym::fill(func.span, &mut func.id);
+            self.component_fields_to_append
+                .push(ComponentField::Export(ComponentExport {
+                    span: func.span,
+                    id: None,
+                    debug_name: None,
+                    name,
+                    url,
+                    kind: ComponentExportKind::func(func.span, id),
+                    ty: None,
+                }));
+        }
+        match &mut func.kind {
+            FuncKind::Import { import, ty } => {
+                let idx = self.expand_component_type_use(ty);
+                Some(ComponentField::Import(ComponentImport {
+                    span: func.span,
+                    name: import.name,
+                    url: import.url,
+                    item: ItemSig {
+                        span: func.span,
+                        id: func.id,
+                        name: None,
+                        kind: ItemSigKind::Func(ComponentTypeUse::Ref(idx)),
+                    },
+                }))
+            }
+            FuncKind::Lift { ty, info } => {
+                let idx = self.expand_component_type_use(ty);
+                Some(ComponentField::CanonicalFunc(CanonicalFunc {
+                    span: func.span,
+                    id: func.id,
+                    name: func.name,
+                    kind: CanonicalFuncKind::Lift {
+                        ty: ComponentTypeUse::Ref(idx),
+                        info: mem::take(info),
+                    },
+                }))
+            }
+            FuncKind::Alias(a) => Some(ComponentField::Alias(Alias {
+                span: func.span,
+                id: func.id,
+                name: func.name,
+                target: AliasTarget::Export {
+                    instance: a.instance,
+                    name: a.name,
+                    kind: ComponentExportAliasKind::Func,
+                },
+            })),
+        }
+    }
+
+    fn expand_core_type(&mut self, field: &mut CoreType<'a>) {
+        match &mut field.def {
+            CoreTypeDef::Def(_) => {}
+            CoreTypeDef::Module(m) => self.expand_module_ty(m),
+        }
+
+        let id = gensym::fill(field.span, &mut field.id);
+        let index = Index::Id(id);
+        match &field.def {
+            CoreTypeDef::Def(_) => {}
+            CoreTypeDef::Module(t) => t.key().insert(self, index),
+        }
+    }
+
+    fn expand_type(&mut self, field: &mut Type<'a>) {
+        match &mut field.def {
+            TypeDef::Defined(d) => self.expand_defined_ty(d),
+            TypeDef::Func(f) => self.expand_func_ty(f),
+            TypeDef::Component(c) => self.expand_component_ty(c),
+            TypeDef::Instance(i) => self.expand_instance_ty(i),
+        }
+
+        let id = gensym::fill(field.span, &mut field.id);
+        let index = Index::Id(id);
+        match &field.def {
+            TypeDef::Defined(t) => t.key().insert(self, index),
+            TypeDef::Func(t) => t.key().insert(self, index),
+            TypeDef::Component(t) => t.key().insert(self, index),
+            TypeDef::Instance(t) => t.key().insert(self, index),
+        }
+        for (name, url) in field.exports.names.drain(..) {
+            self.component_fields_to_append
+                .push(ComponentField::Export(ComponentExport {
+                    span: field.span,
+                    id: None,
+                    debug_name: None,
+                    name,
+                    url,
+                    kind: ComponentExportKind::ty(field.span, id),
+                    ty: None,
+                }));
+        }
+    }
+
+    fn expand_func_ty(&mut self, ty: &mut ComponentFunctionType<'a>) {
+        for param in ty.params.iter_mut() {
+            self.expand_component_val_ty(&mut param.ty);
+        }
+
+        for result in ty.results.iter_mut() {
+            self.expand_component_val_ty(&mut result.ty);
+        }
+    }
+
+    fn expand_module_ty(&mut self, ty: &mut ModuleType<'a>) {
+        use crate::core::resolve::types::{FuncKey, TypeKey, TypeReference};
+
+        // Note that this is a custom implementation from everything else in
+        // this file since this is using core wasm types instead of component
+        // types, so a small part of the core wasm expansion process is
+        // inlined here to handle the `TypeUse` from core wasm.
+
+        let mut func_type_to_idx = HashMap::new();
+        let mut to_prepend = Vec::new();
+        let mut i = 0;
+        while i < ty.decls.len() {
+            match &mut ty.decls[i] {
+                ModuleTypeDecl::Type(ty) => match &ty.def {
+                    core::TypeDef::Func(f) => {
+                        let id = gensym::fill(ty.span, &mut ty.id);
+                        func_type_to_idx.insert(f.key(), Index::Id(id));
+                    }
+                    core::TypeDef::Struct(_) => {}
+                    core::TypeDef::Array(_) => {}
+                },
+                ModuleTypeDecl::Alias(_) => {}
+                ModuleTypeDecl::Import(ty) => {
+                    expand_sig(&mut ty.item, &mut to_prepend, &mut func_type_to_idx);
+                }
+                ModuleTypeDecl::Export(_, item) => {
+                    expand_sig(item, &mut to_prepend, &mut func_type_to_idx);
+                }
+            }
+            ty.decls.splice(i..i, to_prepend.drain(..));
+            i += 1;
+        }
+
+        fn expand_sig<'a>(
+            item: &mut core::ItemSig<'a>,
+            to_prepend: &mut Vec<ModuleTypeDecl<'a>>,
+            func_type_to_idx: &mut HashMap<FuncKey<'a>, Index<'a>>,
+        ) {
+            match &mut item.kind {
+                core::ItemKind::Func(t) | core::ItemKind::Tag(core::TagType::Exception(t)) => {
+                    // If the index is already filled in then this is skipped
+                    if t.index.is_some() {
+                        return;
+                    }
+
+                    // Otherwise the inline type information is used to
+                    // generate a type into this module if necessary. If the
+                    // function type already exists we reuse the same key,
+                    // otherwise a fresh type definition is created and we use
+                    // that one instead.
+                    let ty = t.inline.take().unwrap_or_default();
+                    let key = ty.key();
+                    if let Some(idx) = func_type_to_idx.get(&key) {
+                        t.index = Some(*idx);
+                        return;
+                    }
+                    let id = gensym::gen(item.span);
+                    to_prepend.push(ModuleTypeDecl::Type(core::Type {
+                        span: item.span,
+                        id: Some(id),
+                        name: None,
+                        def: key.to_def(item.span),
+                        parent: None,
+                    }));
+                    let idx = Index::Id(id);
+                    t.index = Some(idx);
+                }
+                core::ItemKind::Global(_)
+                | core::ItemKind::Table(_)
+                | core::ItemKind::Memory(_) => {}
+            }
+        }
+    }
+
+    fn expand_component_ty(&mut self, ty: &mut ComponentType<'a>) {
+        Expander::default().expand_decls(&mut ty.decls, |e, decl| match decl {
+            ComponentTypeDecl::CoreType(t) => e.expand_core_type(t),
+            ComponentTypeDecl::Type(t) => e.expand_type(t),
+            ComponentTypeDecl::Alias(_) => {}
+            ComponentTypeDecl::Export(t) => e.expand_item_sig(&mut t.item),
+            ComponentTypeDecl::Import(t) => e.expand_item_sig(&mut t.item),
+        })
+    }
+
+    fn expand_instance_ty(&mut self, ty: &mut InstanceType<'a>) {
+        Expander::default().expand_decls(&mut ty.decls, |e, decl| match decl {
+            InstanceTypeDecl::CoreType(t) => e.expand_core_type(t),
+            InstanceTypeDecl::Type(t) => e.expand_type(t),
+            InstanceTypeDecl::Alias(_) => {}
+            InstanceTypeDecl::Export(t) => e.expand_item_sig(&mut t.item),
+        })
+    }
+
+    fn expand_item_sig(&mut self, ext: &mut ItemSig<'a>) {
+        match &mut ext.kind {
+            ItemSigKind::CoreModule(t) => {
+                self.expand_core_type_use(t);
+            }
+            ItemSigKind::Func(t) => {
+                self.expand_component_type_use(t);
+            }
+            ItemSigKind::Component(t) => {
+                self.expand_component_type_use(t);
+            }
+            ItemSigKind::Instance(t) => {
+                self.expand_component_type_use(t);
+            }
+            ItemSigKind::Value(t) => {
+                self.expand_component_val_ty(&mut t.0);
+            }
+            ItemSigKind::Type(_) => {}
+        }
+    }
+
+    fn expand_defined_ty(&mut self, ty: &mut ComponentDefinedType<'a>) {
+        match ty {
+            ComponentDefinedType::Primitive(_)
+            | ComponentDefinedType::Flags(_)
+            | ComponentDefinedType::Enum(_) => {}
+            ComponentDefinedType::Record(r) => {
+                for field in r.fields.iter_mut() {
+                    self.expand_component_val_ty(&mut field.ty);
+                }
+            }
+            ComponentDefinedType::Variant(v) => {
+                for case in v.cases.iter_mut() {
+                    if let Some(ty) = &mut case.ty {
+                        self.expand_component_val_ty(ty);
+                    }
+                }
+            }
+            ComponentDefinedType::List(t) => {
+                self.expand_component_val_ty(&mut t.element);
+            }
+            ComponentDefinedType::Tuple(t) => {
+                for field in t.fields.iter_mut() {
+                    self.expand_component_val_ty(field);
+                }
+            }
+            ComponentDefinedType::Union(u) => {
+                for ty in u.types.iter_mut() {
+                    self.expand_component_val_ty(ty);
+                }
+            }
+            ComponentDefinedType::Option(t) => {
+                self.expand_component_val_ty(&mut t.element);
+            }
+            ComponentDefinedType::Result(r) => {
+                if let Some(ty) = &mut r.ok {
+                    self.expand_component_val_ty(ty);
+                }
+
+                if let Some(ty) = &mut r.err {
+                    self.expand_component_val_ty(ty);
+                }
+            }
+        }
+    }
+
+    fn expand_component_val_ty(&mut self, ty: &mut ComponentValType<'a>) {
+        let inline = match ty {
+            ComponentValType::Inline(ComponentDefinedType::Primitive(_))
+            | ComponentValType::Ref(_) => return,
+            ComponentValType::Inline(inline) => {
+                self.expand_defined_ty(inline);
+                mem::take(inline)
+            }
+        };
+        // If this inline type has already been defined within this context
+        // then reuse the previously defined type to avoid injecting too many
+        // types into the type index space.
+        if let Some(idx) = inline.key().lookup(self) {
+            *ty = ComponentValType::Ref(idx);
+            return;
+        }
+
+        // And if this type isn't already defined we append it to the index
+        // space with a fresh and unique name.
+        let span = Span::from_offset(0); // FIXME(#613): don't manufacture
+        let id = gensym::gen(span);
+
+        self.types_to_prepend.push(inline.into_any_type(span, id));
+
+        let idx = Index::Id(id);
+        *ty = ComponentValType::Ref(idx);
+    }
+
+    fn expand_core_type_use<T>(
+        &mut self,
+        item: &mut CoreTypeUse<'a, T>,
+    ) -> CoreItemRef<'a, kw::r#type>
+    where
+        T: TypeReference<'a>,
+    {
+        let span = Span::from_offset(0); // FIXME(#613): don't manufacture
+        let mut inline = match mem::take(item) {
+            // If this type-use was already a reference to an existing type
+            // then we put it back the way it was and return the corresponding
+            // index.
+            CoreTypeUse::Ref(idx) => {
+                *item = CoreTypeUse::Ref(idx.clone());
+                return idx;
+            }
+
+            // ... otherwise with an inline type definition we go into
+            // processing below.
+            CoreTypeUse::Inline(inline) => inline,
+        };
+        inline.expand(self);
+
+        // If this inline type has already been defined within this context
+        // then reuse the previously defined type to avoid injecting too many
+        // types into the type index space.
+        if let Some(idx) = inline.key().lookup(self) {
+            let ret = CoreItemRef {
+                idx,
+                kind: kw::r#type(span),
+                export_name: None,
+            };
+            *item = CoreTypeUse::Ref(ret.clone());
+            return ret;
+        }
+
+        // And if this type isn't already defined we append it to the index
+        // space with a fresh and unique name.
+        let id = gensym::gen(span);
+
+        self.types_to_prepend.push(inline.into_any_type(span, id));
+
+        let idx = Index::Id(id);
+        let ret = CoreItemRef {
+            idx,
+            kind: kw::r#type(span),
+            export_name: None,
+        };
+
+        *item = CoreTypeUse::Ref(ret.clone());
+        ret
+    }
+
+    fn expand_component_type_use<T>(
+        &mut self,
+        item: &mut ComponentTypeUse<'a, T>,
+    ) -> ItemRef<'a, kw::r#type>
+    where
+        T: TypeReference<'a>,
+    {
+        let span = Span::from_offset(0); // FIXME(#613): don't manufacture
+        let mut inline = match mem::take(item) {
+            // If this type-use was already a reference to an existing type
+            // then we put it back the way it was and return the corresponding
+            // index.
+            ComponentTypeUse::Ref(idx) => {
+                *item = ComponentTypeUse::Ref(idx.clone());
+                return idx;
+            }
+
+            // ... otherwise with an inline type definition we go into
+            // processing below.
+            ComponentTypeUse::Inline(inline) => inline,
+        };
+        inline.expand(self);
+
+        // If this inline type has already been defined within this context
+        // then reuse the previously defined type to avoid injecting too many
+        // types into the type index space.
+        if let Some(idx) = inline.key().lookup(self) {
+            let ret = ItemRef {
+                idx,
+                kind: kw::r#type(span),
+                export_names: Vec::new(),
+            };
+            *item = ComponentTypeUse::Ref(ret.clone());
+            return ret;
+        }
+
+        // And if this type isn't already defined we append it to the index
+        // space with a fresh and unique name.
+        let id = gensym::gen(span);
+
+        self.types_to_prepend.push(inline.into_any_type(span, id));
+
+        let idx = Index::Id(id);
+        let ret = ItemRef {
+            idx,
+            kind: kw::r#type(span),
+            export_names: Vec::new(),
+        };
+
+        *item = ComponentTypeUse::Ref(ret.clone());
+        ret
+    }
+
+    fn expand_core_instantiation_arg(&mut self, arg: &mut CoreInstantiationArgKind<'a>) {
+        let (span, exports) = match arg {
+            CoreInstantiationArgKind::Instance(_) => return,
+            CoreInstantiationArgKind::BundleOfExports(span, exports) => (*span, mem::take(exports)),
+        };
+        let id = gensym::gen(span);
+        self.component_fields_to_prepend
+            .push(ComponentField::CoreInstance(CoreInstance {
+                span,
+                id: Some(id),
+                name: None,
+                kind: CoreInstanceKind::BundleOfExports(exports),
+            }));
+        *arg = CoreInstantiationArgKind::Instance(CoreItemRef {
+            kind: kw::instance(span),
+            idx: Index::Id(id),
+            export_name: None,
+        });
+    }
+
+    fn expand_instantiation_arg(&mut self, arg: &mut InstantiationArgKind<'a>) {
+        let (span, exports) = match arg {
+            InstantiationArgKind::Item(_) => return,
+            InstantiationArgKind::BundleOfExports(span, exports) => (*span, mem::take(exports)),
+        };
+        let id = gensym::gen(span);
+        self.component_fields_to_prepend
+            .push(ComponentField::Instance(Instance {
+                span,
+                id: Some(id),
+                name: None,
+                exports: Default::default(),
+                kind: InstanceKind::BundleOfExports(exports),
+            }));
+        *arg = InstantiationArgKind::Item(ComponentExportKind::instance(span, id));
+    }
+}
+
+trait TypeReference<'a> {
+    type Key: TypeKey<'a>;
+    fn key(&self) -> Self::Key;
+    fn expand(&mut self, cx: &mut Expander<'a>);
+    fn into_any_type(self, span: Span, id: Id<'a>) -> AnyType<'a>;
+}
+
+impl<'a> TypeReference<'a> for ComponentDefinedType<'a> {
+    type Key = Todo; // FIXME(#598): should implement this
+
+    fn key(&self) -> Self::Key {
+        Todo
+    }
+
+    fn expand(&mut self, cx: &mut Expander<'a>) {
+        cx.expand_defined_ty(self)
+    }
+
+    fn into_any_type(self, span: Span, id: Id<'a>) -> AnyType<'a> {
+        AnyType::Component(Type {
+            span,
+            id: Some(id),
+            name: None,
+            exports: Default::default(),
+            def: TypeDef::Defined(self),
+        })
+    }
+}
+
+impl<'a> TypeReference<'a> for ComponentType<'a> {
+    type Key = Todo; // FIXME(#598): should implement this
+
+    fn key(&self) -> Self::Key {
+        Todo
+    }
+
+    fn expand(&mut self, cx: &mut Expander<'a>) {
+        cx.expand_component_ty(self)
+    }
+
+    fn into_any_type(self, span: Span, id: Id<'a>) -> AnyType<'a> {
+        AnyType::Component(Type {
+            span,
+            id: Some(id),
+            name: None,
+            exports: Default::default(),
+            def: TypeDef::Component(self),
+        })
+    }
+}
+
+impl<'a> TypeReference<'a> for ModuleType<'a> {
+    type Key = Todo; // FIXME(#598): should implement this
+
+    fn key(&self) -> Self::Key {
+        Todo
+    }
+
+    fn expand(&mut self, cx: &mut Expander<'a>) {
+        cx.expand_module_ty(self)
+    }
+
+    fn into_any_type(self, span: Span, id: Id<'a>) -> AnyType<'a> {
+        AnyType::Core(CoreType {
+            span,
+            id: Some(id),
+            name: None,
+            def: CoreTypeDef::Module(self),
+        })
+    }
+}
+
+impl<'a> TypeReference<'a> for InstanceType<'a> {
+    type Key = Todo; // FIXME(#598): should implement this
+
+    fn key(&self) -> Self::Key {
+        Todo
+    }
+
+    fn expand(&mut self, cx: &mut Expander<'a>) {
+        cx.expand_instance_ty(self)
+    }
+
+    fn into_any_type(self, span: Span, id: Id<'a>) -> AnyType<'a> {
+        AnyType::Component(Type {
+            span,
+            id: Some(id),
+            name: None,
+            exports: Default::default(),
+            def: TypeDef::Instance(self),
+        })
+    }
+}
+
+impl<'a> TypeReference<'a> for ComponentFunctionType<'a> {
+    type Key = Todo; // FIXME(#598): should implement this
+
+    fn key(&self) -> Self::Key {
+        Todo
+    }
+
+    fn expand(&mut self, cx: &mut Expander<'a>) {
+        cx.expand_func_ty(self)
+    }
+
+    fn into_any_type(self, span: Span, id: Id<'a>) -> AnyType<'a> {
+        AnyType::Component(Type {
+            span,
+            id: Some(id),
+            name: None,
+            exports: Default::default(),
+            def: TypeDef::Func(self),
+        })
+    }
+}
+
+trait TypeKey<'a> {
+    fn lookup(&self, cx: &Expander<'a>) -> Option<Index<'a>>;
+    fn insert(&self, cx: &mut Expander<'a>, index: Index<'a>);
+}
+
+struct Todo;
+
+impl<'a> TypeKey<'a> for Todo {
+    fn lookup(&self, _cx: &Expander<'a>) -> Option<Index<'a>> {
+        None
+    }
+
+    fn insert(&self, _cx: &mut Expander<'a>, _index: Index<'a>) {}
+}
diff --git a/third_party/rust/wast/src/component/export.rs b/third_party/rust/wast/src/component/export.rs
new file mode 100644
index 0000000000..ce9baaf453
--- /dev/null
+++ b/third_party/rust/wast/src/component/export.rs
@@ -0,0 +1,221 @@
+use super::{ItemRef, ItemSigNoName};
+use crate::kw;
+use crate::parser::{Cursor, Parse, Parser, Peek, Result};
+use crate::token::{Id, Index, NameAnnotation, Span};
+
+/// An entry in a WebAssembly component's export section.
+#[derive(Debug)]
+pub struct ComponentExport<'a> {
+    /// Where this export was defined.
+    pub span: Span,
+    /// Optional identifier bound to this export.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this instance stored in the custom `name` section.
+    pub debug_name: Option<NameAnnotation<'a>>,
+    /// The name of this export from the component.
+    pub name: &'a str,
+    /// The URL of the export.
+    pub url: Option<&'a str>,
+    /// The kind of export.
+    pub kind: ComponentExportKind<'a>,
+    /// The kind of export.
+    pub ty: Option<ItemSigNoName<'a>>,
+}
+
+impl<'a> Parse<'a> for ComponentExport<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::export>()?.0;
+        let id = parser.parse()?;
+        let debug_name = parser.parse()?;
+        let name = parser.parse()?;
+        let url = parser.parse()?;
+        let kind = parser.parse()?;
+        let ty = if !parser.is_empty() {
+            Some(parser.parens(|p| p.parse())?)
+        } else {
+            None
+        };
+        Ok(ComponentExport {
+            span,
+            id,
+            debug_name,
+            name,
+            url,
+            kind,
+            ty,
+        })
+    }
+}
+
+impl<'a> Parse<'a> for Vec<ComponentExport<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut exports = Vec::new();
+        while !parser.is_empty() {
+            exports.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(exports)
+    }
+}
+
+/// The kind of exported item.
+#[derive(Debug)]
+pub enum ComponentExportKind<'a> {
+    /// The export is a core module.
+    ///
+    /// Note this isn't a core item ref as currently only
+    /// components can export core modules.
+    CoreModule(ItemRef<'a, kw::module>),
+    /// The export is a function.
+    Func(ItemRef<'a, kw::func>),
+    /// The export is a value.
+    Value(ItemRef<'a, kw::value>),
+    /// The export is a type.
+    Type(ItemRef<'a, kw::r#type>),
+    /// The export is a component.
+    Component(ItemRef<'a, kw::component>),
+    /// The export is an instance.
+    Instance(ItemRef<'a, kw::instance>),
+}
+
+impl<'a> ComponentExportKind<'a> {
+    pub(crate) fn module(span: Span, id: Id<'a>) -> Self {
+        Self::CoreModule(ItemRef {
+            kind: kw::module(span),
+            idx: Index::Id(id),
+            export_names: Default::default(),
+        })
+    }
+
+    pub(crate) fn component(span: Span, id: Id<'a>) -> Self {
+        Self::Component(ItemRef {
+            kind: kw::component(span),
+            idx: Index::Id(id),
+            export_names: Default::default(),
+        })
+    }
+
+    pub(crate) fn instance(span: Span, id: Id<'a>) -> Self {
+        Self::Instance(ItemRef {
+            kind: kw::instance(span),
+            idx: Index::Id(id),
+            export_names: Default::default(),
+        })
+    }
+
+    pub(crate) fn func(span: Span, id: Id<'a>) -> Self {
+        Self::Func(ItemRef {
+            kind: kw::func(span),
+            idx: Index::Id(id),
+            export_names: Default::default(),
+        })
+    }
+
+    pub(crate) fn ty(span: Span, id: Id<'a>) -> Self {
+        Self::Type(ItemRef {
+            kind: kw::r#type(span),
+            idx: Index::Id(id),
+            export_names: Default::default(),
+        })
+    }
+}
+
+impl<'a> Parse<'a> for ComponentExportKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parens(|parser| {
+            let mut l = parser.lookahead1();
+            if l.peek::<kw::core>() {
+                // Remove core prefix
+                parser.parse::<kw::core>()?;
+                Ok(Self::CoreModule(parser.parse()?))
+            } else if l.peek::<kw::func>() {
+                Ok(Self::Func(parser.parse()?))
+            } else if l.peek::<kw::value>() {
+                Ok(Self::Value(parser.parse()?))
+            } else if l.peek::<kw::r#type>() {
+                Ok(Self::Type(parser.parse()?))
+            } else if l.peek::<kw::component>() {
+                Ok(Self::Component(parser.parse()?))
+            } else if l.peek::<kw::instance>() {
+                Ok(Self::Instance(parser.parse()?))
+            } else {
+                Err(l.error())
+            }
+        })
+    }
+}
+
+impl Peek for ComponentExportKind<'_> {
+    fn peek(cursor: Cursor) -> bool {
+        let cursor = match cursor.lparen() {
+            Some(c) => c,
+            None => return false,
+        };
+
+        let cursor = match cursor.keyword() {
+            Some(("core", c)) => match c.keyword() {
+                Some(("module", c)) => c,
+                _ => return false,
+            },
+            Some(("func", c))
+            | Some(("value", c))
+            | Some(("type", c))
+            | Some(("component", c))
+            | Some(("instance", c)) => c,
+            _ => return false,
+        };
+
+        Index::peek(cursor)
+    }
+
+    fn display() -> &'static str {
+        "component export"
+    }
+}
+
+/// A listing of inline `(export "foo" <url>)` statements on a WebAssembly
+/// component item in its textual format.
+#[derive(Debug, Default)]
+pub struct InlineExport<'a> {
+    /// The extra names to export an item as, if any.
+    pub names: Vec<(&'a str, Option<&'a str>)>,
+}
+
+impl<'a> Parse<'a> for InlineExport<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut names = Vec::new();
+        while parser.peek::<Self>() {
+            names.push(parser.parens(|p| {
+                p.parse::<kw::export>()?;
+                Ok((p.parse()?, p.parse()?))
+            })?);
+        }
+        Ok(InlineExport { names })
+    }
+}
+
+impl Peek for InlineExport<'_> {
+    fn peek(cursor: Cursor<'_>) -> bool {
+        let cursor = match cursor.lparen() {
+            Some(cursor) => cursor,
+            None => return false,
+        };
+        let cursor = match cursor.keyword() {
+            Some(("export", cursor)) => cursor,
+            _ => return false,
+        };
+        // Name
+        let mut cursor = match cursor.string() {
+            Some((_, cursor)) => cursor,
+            None => return false,
+        };
+        // Optional URL
+        if let Some((_, c)) = cursor.string() {
+            cursor = c;
+        }
+        cursor.rparen().is_some()
+    }
+
+    fn display() -> &'static str {
+        "inline export"
+    }
+}
diff --git a/third_party/rust/wast/src/component/func.rs b/third_party/rust/wast/src/component/func.rs
new file mode 100644
index 0000000000..4edbc63171
--- /dev/null
+++ b/third_party/rust/wast/src/component/func.rs
@@ -0,0 +1,372 @@
+use crate::component::*;
+use crate::kw;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::{Id, Index, LParen, NameAnnotation, Span};
+
+/// A declared core function.
+///
+/// This is a member of both the core alias and canon sections.
+#[derive(Debug)]
+pub struct CoreFunc<'a> {
+    /// Where this `core func` was defined.
+    pub span: Span,
+    /// An identifier that this function is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this function stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// The kind of core function.
+    pub kind: CoreFuncKind<'a>,
+}
+
+impl<'a> Parse<'a> for CoreFunc<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::core>()?.0;
+        parser.parse::<kw::func>()?;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let kind = parser.parse()?;
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            kind,
+        })
+    }
+}
+
+/// Represents the kind of core functions.
+#[derive(Debug)]
+pub enum CoreFuncKind<'a> {
+    /// The core function is defined in terms of lowering a component function.
+    ///
+    /// The core function is actually a member of the canon section.
+    Lower(CanonLower<'a>),
+    /// The core function is defined in terms of aliasing a module instance export.
+    ///
+    /// The core function is actually a member of the core alias section.
+    Alias(InlineExportAlias<'a>),
+}
+
+impl<'a> Parse<'a> for CoreFuncKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parens(|parser| {
+            let mut l = parser.lookahead1();
+            if l.peek::<kw::canon>() {
+                parser.parse::<kw::canon>()?;
+                Ok(Self::Lower(parser.parse()?))
+            } else if l.peek::<kw::alias>() {
+                Ok(Self::Alias(parser.parse()?))
+            } else {
+                Err(l.error())
+            }
+        })
+    }
+}
+
+/// A declared component function.
+///
+/// This may be a member of the import, alias, or canon sections.
+#[derive(Debug)]
+pub struct Func<'a> {
+    /// Where this `func` was defined.
+    pub span: Span,
+    /// An identifier that this function is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this function stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// If present, inline export annotations which indicate names this
+    /// definition should be exported under.
+    pub exports: InlineExport<'a>,
+    /// The kind of function.
+    pub kind: FuncKind<'a>,
+}
+
+impl<'a> Parse<'a> for Func<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::func>()?.0;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let exports = parser.parse()?;
+        let kind = parser.parse()?;
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            exports,
+            kind,
+        })
+    }
+}
+
+/// Represents the kind of component functions.
+#[derive(Debug)]
+pub enum FuncKind<'a> {
+    /// A function which is actually defined as an import, such as:
+    ///
+    /// ```text
+    /// (func (import "foo") (param string))
+    /// ```
+    Import {
+        /// The import name of this import.
+        import: InlineImport<'a>,
+        /// The type that this function will have.
+        ty: ComponentTypeUse<'a, ComponentFunctionType<'a>>,
+    },
+    /// The function is defined in terms of lifting a core function.
+    ///
+    /// The function is actually a member of the canon section.
+    Lift {
+        /// The lifted function's type.
+        ty: ComponentTypeUse<'a, ComponentFunctionType<'a>>,
+        /// Information relating to the lifting of the core function.
+        info: CanonLift<'a>,
+    },
+    /// The function is defined in terms of aliasing a component instance export.
+    ///
+    /// The function is actually a member of the alias section.
+    Alias(InlineExportAlias<'a>),
+}
+
+impl<'a> Parse<'a> for FuncKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if let Some(import) = parser.parse()? {
+            Ok(Self::Import {
+                import,
+                ty: parser.parse()?,
+            })
+        } else if parser.peek::<LParen>() && parser.peek2::<kw::alias>() {
+            parser.parens(|parser| Ok(Self::Alias(parser.parse()?)))
+        } else {
+            Ok(Self::Lift {
+                ty: parser.parse()?,
+                info: parser.parens(|parser| {
+                    parser.parse::<kw::canon>()?;
+                    parser.parse()
+                })?,
+            })
+        }
+    }
+}
+
+/// A WebAssembly canonical function to be inserted into a component.
+///
+/// This is a member of the canonical section.
+#[derive(Debug)]
+pub struct CanonicalFunc<'a> {
+    /// Where this `func` was defined.
+    pub span: Span,
+    /// An identifier that this function is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this function stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// What kind of function this is, be it a lowered or lifted function.
+    pub kind: CanonicalFuncKind<'a>,
+}
+
+impl<'a> Parse<'a> for CanonicalFunc<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::canon>()?.0;
+
+        if parser.peek::<kw::lift>() {
+            let info = parser.parse()?;
+            let (id, name, ty) = parser.parens(|parser| {
+                parser.parse::<kw::func>()?;
+                let id = parser.parse()?;
+                let name = parser.parse()?;
+                let ty = parser.parse()?;
+                Ok((id, name, ty))
+            })?;
+
+            Ok(Self {
+                span,
+                id,
+                name,
+                kind: CanonicalFuncKind::Lift { info, ty },
+            })
+        } else if parser.peek::<kw::lower>() {
+            let info = parser.parse()?;
+            let (id, name) = parser.parens(|parser| {
+                parser.parse::<kw::core>()?;
+                parser.parse::<kw::func>()?;
+                let id = parser.parse()?;
+                let name = parser.parse()?;
+                Ok((id, name))
+            })?;
+
+            Ok(Self {
+                span,
+                id,
+                name,
+                kind: CanonicalFuncKind::Lower(info),
+            })
+        } else {
+            Err(parser.error("expected `canon lift` or `canon lower`"))
+        }
+    }
+}
+
+/// Possible ways to define a canonical function in the text format.
+#[derive(Debug)]
+pub enum CanonicalFuncKind<'a> {
+    /// A canonical function that is defined in terms of lifting a core function.
+    Lift {
+        /// The lifted function's type.
+        ty: ComponentTypeUse<'a, ComponentFunctionType<'a>>,
+        /// Information relating to the lifting of the core function.
+        info: CanonLift<'a>,
+    },
+    /// A canonical function that is defined in terms of lowering a component function.
+    Lower(CanonLower<'a>),
+}
+
+/// Information relating to lifting a core function.
+#[derive(Debug)]
+pub struct CanonLift<'a> {
+    /// The core function being lifted.
+    pub func: CoreItemRef<'a, kw::func>,
+    /// The canonical options for the lifting.
+    pub opts: Vec<CanonOpt<'a>>,
+}
+
+impl<'a> Parse<'a> for CanonLift<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::lift>()?;
+
+        Ok(Self {
+            func: parser.parens(|parser| {
+                parser.parse::<kw::core>()?;
+                parser.parse()
+            })?,
+            opts: parser.parse()?,
+        })
+    }
+}
+
+impl Default for CanonLift<'_> {
+    fn default() -> Self {
+        let span = Span::from_offset(0);
+        Self {
+            func: CoreItemRef {
+                kind: kw::func(span),
+                idx: Index::Num(0, span),
+                export_name: None,
+            },
+            opts: Vec::new(),
+        }
+    }
+}
+
+/// Information relating to lowering a component function.
+#[derive(Debug)]
+pub struct CanonLower<'a> {
+    /// The function being lowered.
+    pub func: ItemRef<'a, kw::func>,
+    /// The canonical options for the lowering.
+    pub opts: Vec<CanonOpt<'a>>,
+}
+
+impl<'a> Parse<'a> for CanonLower<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::lower>()?;
+
+        Ok(Self {
+            func: parser.parens(|parser| parser.parse())?,
+            opts: parser.parse()?,
+        })
+    }
+}
+
+impl Default for CanonLower<'_> {
+    fn default() -> Self {
+        let span = Span::from_offset(0);
+        Self {
+            func: ItemRef {
+                kind: kw::func(span),
+                idx: Index::Num(0, span),
+                export_names: Vec::new(),
+            },
+            opts: Vec::new(),
+        }
+    }
+}
+
+#[derive(Debug)]
+/// Canonical ABI options.
+pub enum CanonOpt<'a> {
+    /// Encode strings as UTF-8.
+    StringUtf8,
+    /// Encode strings as UTF-16.
+    StringUtf16,
+    /// Encode strings as "compact UTF-16".
+    StringLatin1Utf16,
+    /// Use the specified memory for canonical ABI memory access.
+    Memory(CoreItemRef<'a, kw::memory>),
+    /// Use the specified reallocation function for memory allocations.
+    Realloc(CoreItemRef<'a, kw::func>),
+    /// Call the specified function after the lifted function has returned.
+    PostReturn(CoreItemRef<'a, kw::func>),
+}
+
+impl<'a> Parse<'a> for CanonOpt<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::string_utf8>() {
+            parser.parse::<kw::string_utf8>()?;
+            Ok(Self::StringUtf8)
+        } else if l.peek::<kw::string_utf16>() {
+            parser.parse::<kw::string_utf16>()?;
+            Ok(Self::StringUtf16)
+        } else if l.peek::<kw::string_latin1_utf16>() {
+            parser.parse::<kw::string_latin1_utf16>()?;
+            Ok(Self::StringLatin1Utf16)
+        } else if l.peek::<LParen>() {
+            parser.parens(|parser| {
+                let mut l = parser.lookahead1();
+                if l.peek::<kw::memory>() {
+                    let span = parser.parse::<kw::memory>()?.0;
+                    Ok(CanonOpt::Memory(parse_trailing_item_ref(
+                        kw::memory(span),
+                        parser,
+                    )?))
+                } else if l.peek::<kw::realloc>() {
+                    parser.parse::<kw::realloc>()?;
+                    Ok(CanonOpt::Realloc(
+                        parser.parse::<IndexOrCoreRef<'_, _>>()?.0,
+                    ))
+                } else if l.peek::<kw::post_return>() {
+                    parser.parse::<kw::post_return>()?;
+                    Ok(CanonOpt::PostReturn(
+                        parser.parse::<IndexOrCoreRef<'_, _>>()?.0,
+                    ))
+                } else {
+                    Err(l.error())
+                }
+            })
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+fn parse_trailing_item_ref<T>(kind: T, parser: Parser) -> Result<CoreItemRef<T>> {
+    Ok(CoreItemRef {
+        kind,
+        idx: parser.parse()?,
+        export_name: parser.parse()?,
+    })
+}
+
+impl<'a> Parse<'a> for Vec<CanonOpt<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut funcs = Vec::new();
+        while !parser.is_empty() {
+            funcs.push(parser.parse()?);
+        }
+        Ok(funcs)
+    }
+}
diff --git a/third_party/rust/wast/src/component/import.rs b/third_party/rust/wast/src/component/import.rs
new file mode 100644
index 0000000000..98fec55aa7
--- /dev/null
+++ b/third_party/rust/wast/src/component/import.rs
@@ -0,0 +1,176 @@
+use crate::component::*;
+use crate::kw;
+use crate::parser::{Cursor, Parse, Parser, Peek, Result};
+use crate::token::Index;
+use crate::token::{Id, NameAnnotation, Span};
+
+/// An `import` statement and entry in a WebAssembly component.
+#[derive(Debug)]
+pub struct ComponentImport<'a> {
+    /// Where this `import` was defined
+    pub span: Span,
+    /// The name of the item to import.
+    pub name: &'a str,
+    /// The optional URL of the import.
+    pub url: Option<&'a str>,
+    /// The item that's being imported.
+    pub item: ItemSig<'a>,
+}
+
+impl<'a> Parse<'a> for ComponentImport<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::import>()?.0;
+        let name = parser.parse()?;
+        let url = parser.parse()?;
+        let item = parser.parens(|p| p.parse())?;
+        Ok(ComponentImport {
+            span,
+            name,
+            url,
+            item,
+        })
+    }
+}
+
+/// An item signature for imported items.
+#[derive(Debug)]
+pub struct ItemSig<'a> {
+    /// Where this item is defined in the source.
+    pub span: Span,
+    /// An optional identifier used during name resolution to refer to this item
+    /// from the rest of the component.
+    pub id: Option<Id<'a>>,
+    /// An optional name which, for functions, will be stored in the
+    /// custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// What kind of item this is.
+    pub kind: ItemSigKind<'a>,
+}
+
+impl<'a> Parse<'a> for ItemSig<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parse_item_sig(parser, true)
+    }
+}
+
+/// An item signature for imported items.
+#[derive(Debug)]
+pub struct ItemSigNoName<'a>(pub ItemSig<'a>);
+
+impl<'a> Parse<'a> for ItemSigNoName<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        Ok(ItemSigNoName(parse_item_sig(parser, false)?))
+    }
+}
+
+fn parse_item_sig<'a>(parser: Parser<'a>, name: bool) -> Result<ItemSig<'a>> {
+    let mut l = parser.lookahead1();
+    let (span, parse_kind): (_, fn(Parser<'a>) -> Result<ItemSigKind>) = if l.peek::<kw::core>() {
+        let span = parser.parse::<kw::core>()?.0;
+        parser.parse::<kw::module>()?;
+        (span, |parser| Ok(ItemSigKind::CoreModule(parser.parse()?)))
+    } else if l.peek::<kw::func>() {
+        let span = parser.parse::<kw::func>()?.0;
+        (span, |parser| Ok(ItemSigKind::Func(parser.parse()?)))
+    } else if l.peek::<kw::component>() {
+        let span = parser.parse::<kw::component>()?.0;
+        (span, |parser| Ok(ItemSigKind::Component(parser.parse()?)))
+    } else if l.peek::<kw::instance>() {
+        let span = parser.parse::<kw::instance>()?.0;
+        (span, |parser| Ok(ItemSigKind::Instance(parser.parse()?)))
+    } else if l.peek::<kw::value>() {
+        let span = parser.parse::<kw::value>()?.0;
+        (span, |parser| Ok(ItemSigKind::Value(parser.parse()?)))
+    } else if l.peek::<kw::r#type>() {
+        let span = parser.parse::<kw::r#type>()?.0;
+        (span, |parser| {
+            Ok(ItemSigKind::Type(parser.parens(|parser| parser.parse())?))
+        })
+    } else {
+        return Err(l.error());
+    };
+    Ok(ItemSig {
+        span,
+        id: if name { parser.parse()? } else { None },
+        name: if name { parser.parse()? } else { None },
+        kind: parse_kind(parser)?,
+    })
+}
+
+/// The kind of signatures for imported items.
+#[derive(Debug)]
+pub enum ItemSigKind<'a> {
+    /// The item signature is for a core module.
+    CoreModule(CoreTypeUse<'a, ModuleType<'a>>),
+    /// The item signature is for a function.
+    Func(ComponentTypeUse<'a, ComponentFunctionType<'a>>),
+    /// The item signature is for a component.
+    Component(ComponentTypeUse<'a, ComponentType<'a>>),
+    /// The item signature is for an instance.
+    Instance(ComponentTypeUse<'a, InstanceType<'a>>),
+    /// The item signature is for a value.
+    Value(ComponentValTypeUse<'a>),
+    /// The item signature is for a type.
+    Type(TypeBounds<'a>),
+}
+
+/// Represents the bounds applied to types being imported.
+#[derive(Debug)]
+pub enum TypeBounds<'a> {
+    /// The equality type bounds.
+    Eq(Index<'a>),
+}
+
+impl<'a> Parse<'a> for TypeBounds<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        // Currently this is the only supported type bounds.
+        parser.parse::<kw::eq>()?;
+        Ok(Self::Eq(parser.parse()?))
+    }
+}
+
+/// A listing of a inline `(import "foo")` statement.
+///
+/// This is the same as `core::InlineImport` except only one string import is
+/// required.
+#[derive(Debug, Clone)]
+pub struct InlineImport<'a> {
+    /// The name of the item being imported.
+    pub name: &'a str,
+    /// The optional URL of the item being imported.
+    pub url: Option<&'a str>,
+}
+
+impl<'a> Parse<'a> for InlineImport<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parens(|p| {
+            p.parse::<kw::import>()?;
+            Ok(InlineImport {
+                name: p.parse()?,
+                url: p.parse()?,
+            })
+        })
+    }
+}
+
+impl Peek for InlineImport<'_> {
+    fn peek(cursor: Cursor<'_>) -> bool {
+        let cursor = match cursor.lparen() {
+            Some(cursor) => cursor,
+            None => return false,
+        };
+        let cursor = match cursor.keyword() {
+            Some(("import", cursor)) => cursor,
+            _ => return false,
+        };
+        let cursor = match cursor.string() {
+            Some((_, cursor)) => cursor,
+            None => return false,
+        };
+        cursor.rparen().is_some()
+    }
+
+    fn display() -> &'static str {
+        "inline import"
+    }
+}
diff --git a/third_party/rust/wast/src/component/instance.rs b/third_party/rust/wast/src/component/instance.rs
new file mode 100644
index 0000000000..888f4ee9f9
--- /dev/null
+++ b/third_party/rust/wast/src/component/instance.rs
@@ -0,0 +1,296 @@
+use crate::component::*;
+use crate::core;
+use crate::kw;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::{Id, LParen, NameAnnotation, Span};
+
+/// A core instance defined by instantiation or exporting core items.
+#[derive(Debug)]
+pub struct CoreInstance<'a> {
+    /// Where this `core instance` was defined.
+    pub span: Span,
+    /// An identifier that this instance is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this instance stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// What kind of instance this is.
+    pub kind: CoreInstanceKind<'a>,
+}
+
+impl<'a> Parse<'a> for CoreInstance<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::core>()?.0;
+        parser.parse::<kw::instance>()?;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let kind = parser.parse()?;
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            kind,
+        })
+    }
+}
+
+/// The kinds of core instances in the text format.
+#[derive(Debug)]
+pub enum CoreInstanceKind<'a> {
+    /// Instantiate a core module.
+    Instantiate {
+        /// The module being instantiated.
+        module: ItemRef<'a, kw::module>,
+        /// Arguments used to instantiate the instance.
+        args: Vec<CoreInstantiationArg<'a>>,
+    },
+    /// The instance is defined by exporting local items as an instance.
+    BundleOfExports(Vec<CoreInstanceExport<'a>>),
+}
+
+impl<'a> Parse<'a> for CoreInstanceKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<LParen>() && parser.peek2::<kw::instantiate>() {
+            parser.parens(|parser| {
+                parser.parse::<kw::instantiate>()?;
+                Ok(Self::Instantiate {
+                    module: parser.parse::<IndexOrRef<'_, _>>()?.0,
+                    args: parser.parse()?,
+                })
+            })
+        } else {
+            Ok(Self::BundleOfExports(parser.parse()?))
+        }
+    }
+}
+
+impl Default for kw::module {
+    fn default() -> kw::module {
+        kw::module(Span::from_offset(0))
+    }
+}
+
+/// An argument to instantiate a core module.
+#[derive(Debug)]
+pub struct CoreInstantiationArg<'a> {
+    /// The name of the instantiation argument.
+    pub name: &'a str,
+    /// The kind of core instantiation argument.
+    pub kind: CoreInstantiationArgKind<'a>,
+}
+
+impl<'a> Parse<'a> for CoreInstantiationArg<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::with>()?;
+        Ok(Self {
+            name: parser.parse()?,
+            kind: parser.parse()?,
+        })
+    }
+}
+
+impl<'a> Parse<'a> for Vec<CoreInstantiationArg<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut args = Vec::new();
+        while !parser.is_empty() {
+            args.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(args)
+    }
+}
+
+/// The kind of core instantiation argument.
+#[derive(Debug)]
+pub enum CoreInstantiationArgKind<'a> {
+    /// The argument is a reference to an instance.
+    Instance(CoreItemRef<'a, kw::instance>),
+    /// The argument is an instance created from local exported core items.
+    ///
+    /// This is syntactic sugar for defining a core instance and also using it
+    /// as an instantiation argument.
+    BundleOfExports(Span, Vec<CoreInstanceExport<'a>>),
+}
+
+impl<'a> Parse<'a> for CoreInstantiationArgKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parens(|parser| {
+            if let Some(r) = parser.parse()? {
+                Ok(Self::Instance(r))
+            } else {
+                let span = parser.parse::<kw::instance>()?.0;
+                Ok(Self::BundleOfExports(span, parser.parse()?))
+            }
+        })
+    }
+}
+
+/// An exported item as part of a core instance.
+#[derive(Debug)]
+pub struct CoreInstanceExport<'a> {
+    /// Where this export was defined.
+    pub span: Span,
+    /// The name of this export from the instance.
+    pub name: &'a str,
+    /// What's being exported from the instance.
+    pub item: CoreItemRef<'a, core::ExportKind>,
+}
+
+impl<'a> Parse<'a> for CoreInstanceExport<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        Ok(Self {
+            span: parser.parse::<kw::export>()?.0,
+            name: parser.parse()?,
+            item: parser.parens(|parser| parser.parse())?,
+        })
+    }
+}
+
+impl<'a> Parse<'a> for Vec<CoreInstanceExport<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut exports = Vec::new();
+        while !parser.is_empty() {
+            exports.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(exports)
+    }
+}
+
+/// A component instance defined by instantiation or exporting items.
+#[derive(Debug)]
+pub struct Instance<'a> {
+    /// Where this `instance` was defined.
+    pub span: Span,
+    /// An identifier that this instance is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this instance stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// If present, inline export annotations which indicate names this
+    /// definition should be exported under.
+    pub exports: InlineExport<'a>,
+    /// What kind of instance this is.
+    pub kind: InstanceKind<'a>,
+}
+
+impl<'a> Parse<'a> for Instance<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::instance>()?.0;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let exports = parser.parse()?;
+        let kind = parser.parse()?;
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            exports,
+            kind,
+        })
+    }
+}
+
+/// The kinds of instances in the text format.
+#[derive(Debug)]
+pub enum InstanceKind<'a> {
+    /// The `(instance (import "x"))` sugar syntax
+    Import {
+        /// The name of the import
+        import: InlineImport<'a>,
+        /// The type of the instance being imported
+        ty: ComponentTypeUse<'a, InstanceType<'a>>,
+    },
+    /// Instantiate a component.
+    Instantiate {
+        /// The component being instantiated.
+        component: ItemRef<'a, kw::component>,
+        /// Arguments used to instantiate the instance.
+        args: Vec<InstantiationArg<'a>>,
+    },
+    /// The instance is defined by exporting local items as an instance.
+    BundleOfExports(Vec<ComponentExport<'a>>),
+}
+
+impl<'a> Parse<'a> for InstanceKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if let Some(import) = parser.parse()? {
+            return Ok(Self::Import {
+                import,
+                ty: parser.parse()?,
+            });
+        }
+
+        if parser.peek::<LParen>() && parser.peek2::<kw::instantiate>() {
+            parser.parens(|parser| {
+                parser.parse::<kw::instantiate>()?;
+                Ok(Self::Instantiate {
+                    component: parser.parse::<IndexOrRef<'_, _>>()?.0,
+                    args: parser.parse()?,
+                })
+            })
+        } else {
+            Ok(Self::BundleOfExports(parser.parse()?))
+        }
+    }
+}
+
+impl Default for kw::component {
+    fn default() -> kw::component {
+        kw::component(Span::from_offset(0))
+    }
+}
+
+/// An argument to instantiate a component.
+#[derive(Debug)]
+pub struct InstantiationArg<'a> {
+    /// The name of the instantiation argument.
+    pub name: &'a str,
+    /// The kind of instantiation argument.
+    pub kind: InstantiationArgKind<'a>,
+}
+
+impl<'a> Parse<'a> for InstantiationArg<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::with>()?;
+        Ok(Self {
+            name: parser.parse()?,
+            kind: parser.parse()?,
+        })
+    }
+}
+
+impl<'a> Parse<'a> for Vec<InstantiationArg<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut args = Vec::new();
+        while !parser.is_empty() {
+            args.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(args)
+    }
+}
+
+/// The kind of instantiation argument.
+#[derive(Debug)]
+pub enum InstantiationArgKind<'a> {
+    /// The argument is a reference to a component item.
+    Item(ComponentExportKind<'a>),
+    /// The argument is an instance created from local exported items.
+    ///
+    /// This is syntactic sugar for defining an instance and also using it
+    /// as an instantiation argument.
+    BundleOfExports(Span, Vec<ComponentExport<'a>>),
+}
+
+impl<'a> Parse<'a> for InstantiationArgKind<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if let Some(item) = parser.parse()? {
+            Ok(Self::Item(item))
+        } else {
+            parser.parens(|parser| {
+                let span = parser.parse::<kw::instance>()?.0;
+                Ok(Self::BundleOfExports(span, parser.parse()?))
+            })
+        }
+    }
+}
diff --git a/third_party/rust/wast/src/component/item_ref.rs b/third_party/rust/wast/src/component/item_ref.rs
new file mode 100644
index 0000000000..c3bbf2f9f4
--- /dev/null
+++ b/third_party/rust/wast/src/component/item_ref.rs
@@ -0,0 +1,154 @@
+use crate::parser::{Cursor, Parse, Parser, Peek, Result};
+use crate::token::Index;
+
+fn peek<K: Peek>(cursor: Cursor) -> bool {
+    // This is a little fancy because when parsing something like:
+    //
+    //      (type (component (type $foo)))
+    //
+    // we need to disambiguate that from
+    //
+    //      (type (component (type $foo (func))))
+    //
+    // where the first is a type reference and the second is an inline
+    // component type defining a type internally. The peek here not only
+    // peeks for `K` but also for the index and possibly trailing
+    // strings.
+
+    // Peek for the given keyword type
+    if !K::peek(cursor) {
+        return false;
+    }
+
+    // Move past the given keyword
+    let cursor = match cursor.keyword() {
+        Some((_, c)) => c,
+        _ => return false,
+    };
+
+    // Peek an id or integer index, followed by `)` or string to disambiguate
+    match cursor
+        .id()
+        .map(|p| p.1)
+        .or_else(|| cursor.integer().map(|p| p.1))
+    {
+        Some(cursor) => cursor.rparen().is_some() || cursor.string().is_some(),
+        None => false,
+    }
+}
+
+/// Parses core item references.
+#[derive(Clone, Debug)]
+pub struct CoreItemRef<'a, K> {
+    /// The item kind being parsed.
+    pub kind: K,
+    /// The item or instance reference.
+    pub idx: Index<'a>,
+    /// Export name to resolve the item from.
+    pub export_name: Option<&'a str>,
+}
+
+impl<'a, K: Parse<'a>> Parse<'a> for CoreItemRef<'a, K> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        // This does not parse the surrounding `(` and `)` because
+        // core prefix is context dependent and only the caller knows if it should be
+        // present for core references; therefore, the caller parses the parens and any core prefix
+        let kind = parser.parse::<K>()?;
+        let idx = parser.parse()?;
+        let export_name = parser.parse()?;
+        Ok(Self {
+            kind,
+            idx,
+            export_name,
+        })
+    }
+}
+
+impl<'a, K: Peek> Peek for CoreItemRef<'a, K> {
+    fn peek(cursor: Cursor<'_>) -> bool {
+        peek::<K>(cursor)
+    }
+
+    fn display() -> &'static str {
+        "a core item reference"
+    }
+}
+
+/// Parses component item references.
+#[derive(Clone, Debug)]
+pub struct ItemRef<'a, K> {
+    /// The item kind being parsed.
+    pub kind: K,
+    /// The item or instance reference.
+    pub idx: Index<'a>,
+    /// Export names to resolve the item from.
+    pub export_names: Vec<&'a str>,
+}
+
+impl<'a, K: Parse<'a>> Parse<'a> for ItemRef<'a, K> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let kind = parser.parse::<K>()?;
+        let idx = parser.parse()?;
+        let mut export_names = Vec::new();
+        while !parser.is_empty() {
+            export_names.push(parser.parse()?);
+        }
+        Ok(Self {
+            kind,
+            idx,
+            export_names,
+        })
+    }
+}
+
+impl<'a, K: Peek> Peek for ItemRef<'a, K> {
+    fn peek(cursor: Cursor<'_>) -> bool {
+        peek::<K>(cursor)
+    }
+
+    fn display() -> &'static str {
+        "a component item reference"
+    }
+}
+
+/// Convenience structure to parse `$f` or `(item $f)`.
+#[derive(Clone, Debug)]
+pub struct IndexOrRef<'a, K>(pub ItemRef<'a, K>);
+
+impl<'a, K> Parse<'a> for IndexOrRef<'a, K>
+where
+    K: Parse<'a> + Default,
+{
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<Index<'_>>() {
+            Ok(IndexOrRef(ItemRef {
+                kind: K::default(),
+                idx: parser.parse()?,
+                export_names: Vec::new(),
+            }))
+        } else {
+            Ok(IndexOrRef(parser.parens(|p| p.parse())?))
+        }
+    }
+}
+
+/// Convenience structure to parse `$f` or `(item $f)`.
+#[derive(Clone, Debug)]
+pub struct IndexOrCoreRef<'a, K>(pub CoreItemRef<'a, K>);
+
+impl<'a, K> Parse<'a> for IndexOrCoreRef<'a, K>
+where
+    K: Parse<'a> + Default,
+{
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<Index<'_>>() {
+            Ok(IndexOrCoreRef(CoreItemRef {
+                kind: K::default(),
+                idx: parser.parse()?,
+                export_name: None,
+            }))
+        } else {
+            Ok(IndexOrCoreRef(parser.parens(|p| p.parse())?))
+        }
+    }
+}
diff --git a/third_party/rust/wast/src/component/module.rs b/third_party/rust/wast/src/component/module.rs
new file mode 100644
index 0000000000..6871af8d4c
--- /dev/null
+++ b/third_party/rust/wast/src/component/module.rs
@@ -0,0 +1,75 @@
+use crate::component::*;
+use crate::core;
+use crate::kw;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::{Id, NameAnnotation, Span};
+
+/// A core WebAssembly module to be created as part of a component.
+///
+/// This is a member of the core module section.
+#[derive(Debug)]
+pub struct CoreModule<'a> {
+    /// Where this `core module` was defined.
+    pub span: Span,
+    /// An identifier that this module is resolved with (optionally) for name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this module stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// If present, inline export annotations which indicate names this
+    /// definition should be exported under.
+    pub exports: InlineExport<'a>,
+    /// What kind of module this is, be it an inline-defined or imported one.
+    pub kind: CoreModuleKind<'a>,
+}
+
+/// Possible ways to define a core module in the text format.
+#[derive(Debug)]
+pub enum CoreModuleKind<'a> {
+    /// A core module which is actually defined as an import
+    Import {
+        /// Where this core module is imported from
+        import: InlineImport<'a>,
+        /// The type that this core module will have.
+        ty: CoreTypeUse<'a, ModuleType<'a>>,
+    },
+
+    /// Modules that are defined inline.
+    Inline {
+        /// Fields in the core module.
+        fields: Vec<core::ModuleField<'a>>,
+    },
+}
+
+impl<'a> Parse<'a> for CoreModule<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.depth_check()?;
+
+        let span = parser.parse::<kw::core>()?.0;
+        parser.parse::<kw::module>()?;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let exports = parser.parse()?;
+
+        let kind = if let Some(import) = parser.parse()? {
+            CoreModuleKind::Import {
+                import,
+                ty: parser.parse()?,
+            }
+        } else {
+            let mut fields = Vec::new();
+            while !parser.is_empty() {
+                fields.push(parser.parens(|p| p.parse())?);
+            }
+            CoreModuleKind::Inline { fields }
+        };
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            exports,
+            kind,
+        })
+    }
+}
diff --git a/third_party/rust/wast/src/component/resolve.rs b/third_party/rust/wast/src/component/resolve.rs
new file mode 100644
index 0000000000..e87350e329
--- /dev/null
+++ b/third_party/rust/wast/src/component/resolve.rs
@@ -0,0 +1,973 @@
+use crate::component::*;
+use crate::core;
+use crate::kw;
+use crate::names::Namespace;
+use crate::token::Span;
+use crate::token::{Id, Index};
+use crate::Error;
+
+/// Resolve the fields of a component and everything nested within it, changing
+/// `Index::Id` to `Index::Num` and expanding alias syntax sugar.
+pub fn resolve(component: &mut Component<'_>) -> Result<(), Error> {
+    let fields = match &mut component.kind {
+        ComponentKind::Text(fields) => fields,
+        ComponentKind::Binary(_) => return Ok(()),
+    };
+    let mut resolver = Resolver::default();
+    resolver.fields(component.id, fields)
+}
+
+impl<'a> From<Alias<'a>> for ComponentField<'a> {
+    fn from(a: Alias<'a>) -> Self {
+        Self::Alias(a)
+    }
+}
+
+impl<'a> From<Alias<'a>> for ModuleTypeDecl<'a> {
+    fn from(a: Alias<'a>) -> Self {
+        Self::Alias(a)
+    }
+}
+
+impl<'a> From<Alias<'a>> for ComponentTypeDecl<'a> {
+    fn from(a: Alias<'a>) -> Self {
+        Self::Alias(a)
+    }
+}
+
+impl<'a> From<Alias<'a>> for InstanceTypeDecl<'a> {
+    fn from(a: Alias<'a>) -> Self {
+        Self::Alias(a)
+    }
+}
+
+#[derive(Default)]
+struct Resolver<'a> {
+    stack: Vec<ComponentState<'a>>,
+
+    // When a name refers to a definition in an outer scope, we'll need to
+    // insert an outer alias before it. This collects the aliases to be
+    // inserted during resolution.
+    aliases_to_insert: Vec<Alias<'a>>,
+}
+
+/// Context structure used to perform name resolution.
+#[derive(Default)]
+struct ComponentState<'a> {
+    id: Option<Id<'a>>,
+
+    // Namespaces within each component. Note that each namespace carries
+    // with it information about the signature of the item in that namespace.
+    // The signature is later used to synthesize the type of a component and
+    // inject type annotations if necessary.
+    core_funcs: Namespace<'a>,
+    core_globals: Namespace<'a>,
+    core_tables: Namespace<'a>,
+    core_memories: Namespace<'a>,
+    core_types: Namespace<'a>,
+    core_tags: Namespace<'a>,
+    core_instances: Namespace<'a>,
+    core_modules: Namespace<'a>,
+
+    funcs: Namespace<'a>,
+    types: Namespace<'a>,
+    instances: Namespace<'a>,
+    components: Namespace<'a>,
+    values: Namespace<'a>,
+}
+
+impl<'a> ComponentState<'a> {
+    fn new(id: Option<Id<'a>>) -> ComponentState<'a> {
+        ComponentState {
+            id,
+            ..ComponentState::default()
+        }
+    }
+
+    fn register_item_sig(&mut self, sig: &ItemSig<'a>) -> Result<u32, Error> {
+        match &sig.kind {
+            ItemSigKind::CoreModule(_) => self.core_modules.register(sig.id, "core module"),
+            ItemSigKind::Func(_) => self.funcs.register(sig.id, "func"),
+            ItemSigKind::Component(_) => self.components.register(sig.id, "component"),
+            ItemSigKind::Instance(_) => self.instances.register(sig.id, "instance"),
+            ItemSigKind::Value(_) => self.values.register(sig.id, "value"),
+            ItemSigKind::Type(_) => self.types.register(sig.id, "type"),
+        }
+    }
+}
+
+impl<'a> Resolver<'a> {
+    fn current(&mut self) -> &mut ComponentState<'a> {
+        self.stack
+            .last_mut()
+            .expect("should have at least one component state")
+    }
+
+    fn fields(
+        &mut self,
+        id: Option<Id<'a>>,
+        fields: &mut Vec<ComponentField<'a>>,
+    ) -> Result<(), Error> {
+        self.stack.push(ComponentState::new(id));
+        self.resolve_prepending_aliases(fields, Resolver::field, ComponentState::register)?;
+        self.stack.pop();
+        Ok(())
+    }
+
+    fn resolve_prepending_aliases<T>(
+        &mut self,
+        fields: &mut Vec<T>,
+        resolve: fn(&mut Self, &mut T) -> Result<(), Error>,
+        register: fn(&mut ComponentState<'a>, &T) -> Result<(), Error>,
+    ) -> Result<(), Error>
+    where
+        T: From<Alias<'a>>,
+    {
+        assert!(self.aliases_to_insert.is_empty());
+
+        // Iterate through the fields of the component. We use an index
+        // instead of an iterator because we'll be inserting aliases
+        // as we go.
+        let mut i = 0;
+        while i < fields.len() {
+            // Resolve names within the field.
+            resolve(self, &mut fields[i])?;
+
+            // Name resolution may have emitted some aliases. Insert them before
+            // the current definition.
+            let amt = self.aliases_to_insert.len();
+            fields.splice(i..i, self.aliases_to_insert.drain(..).map(T::from));
+            i += amt;
+
+            // Definitions can't refer to themselves or to definitions that appear
+            // later in the format. Now that we're done resolving this field,
+            // assign it an index for later definitions to refer to.
+            register(self.current(), &fields[i])?;
+
+            i += 1;
+        }
+
+        Ok(())
+    }
+
+    fn field(&mut self, field: &mut ComponentField<'a>) -> Result<(), Error> {
+        match field {
+            ComponentField::CoreModule(m) => self.core_module(m),
+            ComponentField::CoreInstance(i) => self.core_instance(i),
+            ComponentField::CoreType(t) => self.core_ty(t),
+            ComponentField::Component(c) => self.component(c),
+            ComponentField::Instance(i) => self.instance(i),
+            ComponentField::Alias(a) => self.alias(a, false),
+            ComponentField::Type(t) => self.ty(t),
+            ComponentField::CanonicalFunc(f) => self.canonical_func(f),
+            ComponentField::CoreFunc(_) => unreachable!("should be expanded already"),
+            ComponentField::Func(_) => unreachable!("should be expanded already"),
+            ComponentField::Start(s) => self.start(s),
+            ComponentField::Import(i) => self.item_sig(&mut i.item),
+            ComponentField::Export(e) => {
+                if let Some(ty) = &mut e.ty {
+                    self.item_sig(&mut ty.0)?;
+                }
+                self.export(&mut e.kind)
+            }
+            ComponentField::Custom(_) => Ok(()),
+        }
+    }
+
+    fn core_module(&mut self, module: &mut CoreModule) -> Result<(), Error> {
+        match &mut module.kind {
+            CoreModuleKind::Inline { fields } => {
+                crate::core::resolve::resolve(fields)?;
+            }
+
+            CoreModuleKind::Import { .. } => {
+                unreachable!("should be expanded already")
+            }
+        }
+
+        Ok(())
+    }
+
+    fn component(&mut self, component: &mut NestedComponent<'a>) -> Result<(), Error> {
+        match &mut component.kind {
+            NestedComponentKind::Import { .. } => unreachable!("should be expanded already"),
+            NestedComponentKind::Inline(fields) => self.fields(component.id, fields),
+        }
+    }
+
+    fn core_instance(&mut self, instance: &mut CoreInstance<'a>) -> Result<(), Error> {
+        match &mut instance.kind {
+            CoreInstanceKind::Instantiate { module, args } => {
+                self.component_item_ref(module)?;
+                for arg in args {
+                    match &mut arg.kind {
+                        CoreInstantiationArgKind::Instance(i) => {
+                            self.core_item_ref(i)?;
+                        }
+                        CoreInstantiationArgKind::BundleOfExports(..) => {
+                            unreachable!("should be expanded already");
+                        }
+                    }
+                }
+            }
+            CoreInstanceKind::BundleOfExports(exports) => {
+                for export in exports {
+                    self.core_item_ref(&mut export.item)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn instance(&mut self, instance: &mut Instance<'a>) -> Result<(), Error> {
+        match &mut instance.kind {
+            InstanceKind::Instantiate { component, args } => {
+                self.component_item_ref(component)?;
+                for arg in args {
+                    match &mut arg.kind {
+                        InstantiationArgKind::Item(e) => {
+                            self.export(e)?;
+                        }
+                        InstantiationArgKind::BundleOfExports(..) => {
+                            unreachable!("should be expanded already")
+                        }
+                    }
+                }
+            }
+            InstanceKind::BundleOfExports(exports) => {
+                for export in exports {
+                    self.export(&mut export.kind)?;
+                }
+            }
+            InstanceKind::Import { .. } => {
+                unreachable!("should be expanded already")
+            }
+        }
+        Ok(())
+    }
+
+    fn item_sig(&mut self, item: &mut ItemSig<'a>) -> Result<(), Error> {
+        match &mut item.kind {
+            // Here we must be explicit otherwise the module type reference will
+            // be assumed to be in the component type namespace
+            ItemSigKind::CoreModule(t) => self.core_type_use(t),
+            ItemSigKind::Func(t) => self.component_type_use(t),
+            ItemSigKind::Component(t) => self.component_type_use(t),
+            ItemSigKind::Instance(t) => self.component_type_use(t),
+            ItemSigKind::Value(t) => self.component_val_type(&mut t.0),
+            ItemSigKind::Type(b) => match b {
+                TypeBounds::Eq(i) => self.resolve_ns(i, Ns::Type),
+            },
+        }
+    }
+
+    fn export(&mut self, kind: &mut ComponentExportKind<'a>) -> Result<(), Error> {
+        match kind {
+            // Here we do *not* have to be explicit as the item ref is to a core module
+            ComponentExportKind::CoreModule(r) => self.component_item_ref(r),
+            ComponentExportKind::Func(r) => self.component_item_ref(r),
+            ComponentExportKind::Value(r) => self.component_item_ref(r),
+            ComponentExportKind::Type(r) => self.component_item_ref(r),
+            ComponentExportKind::Component(r) => self.component_item_ref(r),
+            ComponentExportKind::Instance(r) => self.component_item_ref(r),
+        }
+    }
+
+    fn start(&mut self, start: &mut Start<'a>) -> Result<(), Error> {
+        self.resolve_ns(&mut start.func, Ns::Func)?;
+        for arg in start.args.iter_mut() {
+            self.component_item_ref(arg)?;
+        }
+        Ok(())
+    }
+
+    fn outer_alias<T: Into<Ns>>(
+        &mut self,
+        outer: &mut Index<'a>,
+        index: &mut Index<'a>,
+        kind: T,
+        span: Span,
+        enclosing_only: bool,
+    ) -> Result<(), Error> {
+        // Short-circuit when both indices are already resolved as this
+        // helps to write tests for invalid modules where wasmparser should
+        // be the one returning the error.
+        if let Index::Num(..) = outer {
+            if let Index::Num(..) = index {
+                return Ok(());
+            }
+        }
+
+        // Resolve `outer`, and compute the depth at which to look up
+        // `index`.
+        let depth = match outer {
+            Index::Id(id) => {
+                let mut depth = 0;
+                for resolver in self.stack.iter().rev() {
+                    if resolver.id == Some(*id) {
+                        break;
+                    }
+                    depth += 1;
+                }
+                if depth as usize == self.stack.len() {
+                    return Err(Error::new(
+                        span,
+                        format!("outer component `{}` not found", id.name()),
+                    ));
+                }
+                depth
+            }
+            Index::Num(n, _span) => *n,
+        };
+
+        if depth as usize >= self.stack.len() {
+            return Err(Error::new(
+                span,
+                format!("outer count of `{}` is too large", depth),
+            ));
+        }
+
+        if enclosing_only && depth > 1 {
+            return Err(Error::new(
+                span,
+                "only the local or enclosing scope can be aliased".to_string(),
+            ));
+        }
+
+        *outer = Index::Num(depth, span);
+
+        // Resolve `index` within the computed scope depth.
+        let computed = self.stack.len() - 1 - depth as usize;
+        self.stack[computed].resolve(kind.into(), index)?;
+
+        Ok(())
+    }
+
+    fn alias(&mut self, alias: &mut Alias<'a>, enclosing_only: bool) -> Result<(), Error> {
+        match &mut alias.target {
+            AliasTarget::Export {
+                instance,
+                name: _,
+                kind: _,
+            } => self.resolve_ns(instance, Ns::Instance),
+            AliasTarget::CoreExport {
+                instance,
+                name: _,
+                kind: _,
+            } => self.resolve_ns(instance, Ns::CoreInstance),
+            AliasTarget::Outer { outer, index, kind } => {
+                self.outer_alias(outer, index, *kind, alias.span, enclosing_only)
+            }
+        }
+    }
+
+    fn canonical_func(&mut self, func: &mut CanonicalFunc<'a>) -> Result<(), Error> {
+        let opts = match &mut func.kind {
+            CanonicalFuncKind::Lift { ty, info } => {
+                self.component_type_use(ty)?;
+                self.core_item_ref(&mut info.func)?;
+                &mut info.opts
+            }
+            CanonicalFuncKind::Lower(info) => {
+                self.component_item_ref(&mut info.func)?;
+                &mut info.opts
+            }
+        };
+
+        for opt in opts {
+            match opt {
+                CanonOpt::StringUtf8 | CanonOpt::StringUtf16 | CanonOpt::StringLatin1Utf16 => {}
+                CanonOpt::Memory(r) => self.core_item_ref(r)?,
+                CanonOpt::Realloc(r) | CanonOpt::PostReturn(r) => self.core_item_ref(r)?,
+            }
+        }
+
+        Ok(())
+    }
+
+    fn core_type_use<T>(&mut self, ty: &mut CoreTypeUse<'a, T>) -> Result<(), Error> {
+        let item = match ty {
+            CoreTypeUse::Ref(r) => r,
+            CoreTypeUse::Inline(_) => {
+                unreachable!("inline type-use should be expanded by now")
+            }
+        };
+        self.core_item_ref(item)
+    }
+
+    fn component_type_use<T>(&mut self, ty: &mut ComponentTypeUse<'a, T>) -> Result<(), Error> {
+        let item = match ty {
+            ComponentTypeUse::Ref(r) => r,
+            ComponentTypeUse::Inline(_) => {
+                unreachable!("inline type-use should be expanded by now")
+            }
+        };
+        self.component_item_ref(item)
+    }
+
+    fn defined_type(&mut self, ty: &mut ComponentDefinedType<'a>) -> Result<(), Error> {
+        match ty {
+            ComponentDefinedType::Primitive(_) => {}
+            ComponentDefinedType::Flags(_) => {}
+            ComponentDefinedType::Enum(_) => {}
+            ComponentDefinedType::Record(r) => {
+                for field in r.fields.iter_mut() {
+                    self.component_val_type(&mut field.ty)?;
+                }
+            }
+            ComponentDefinedType::Variant(v) => {
+                // Namespace for case identifier resolution
+                let mut ns = Namespace::default();
+                for case in v.cases.iter_mut() {
+                    let index = ns.register(case.id, "variant case")?;
+
+                    if let Some(ty) = &mut case.ty {
+                        self.component_val_type(ty)?;
+                    }
+
+                    if let Some(refines) = &mut case.refines {
+                        if let Refinement::Index(span, idx) = refines {
+                            let resolved = ns.resolve(idx, "variant case")?;
+                            if resolved == index {
+                                return Err(Error::new(
+                                    *span,
+                                    "variant case cannot refine itself".to_string(),
+                                ));
+                            }
+
+                            *refines = Refinement::Resolved(resolved);
+                        }
+                    }
+                }
+            }
+            ComponentDefinedType::List(l) => {
+                self.component_val_type(&mut l.element)?;
+            }
+            ComponentDefinedType::Tuple(t) => {
+                for field in t.fields.iter_mut() {
+                    self.component_val_type(field)?;
+                }
+            }
+            ComponentDefinedType::Union(t) => {
+                for ty in t.types.iter_mut() {
+                    self.component_val_type(ty)?;
+                }
+            }
+            ComponentDefinedType::Option(o) => {
+                self.component_val_type(&mut o.element)?;
+            }
+            ComponentDefinedType::Result(r) => {
+                if let Some(ty) = &mut r.ok {
+                    self.component_val_type(ty)?;
+                }
+
+                if let Some(ty) = &mut r.err {
+                    self.component_val_type(ty)?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    fn component_val_type(&mut self, ty: &mut ComponentValType<'a>) -> Result<(), Error> {
+        match ty {
+            ComponentValType::Ref(idx) => self.resolve_ns(idx, Ns::Type),
+            ComponentValType::Inline(ComponentDefinedType::Primitive(_)) => Ok(()),
+            ComponentValType::Inline(_) => unreachable!("should be expanded by now"),
+        }
+    }
+
+    fn core_ty(&mut self, field: &mut CoreType<'a>) -> Result<(), Error> {
+        match &mut field.def {
+            CoreTypeDef::Def(_) => {}
+            CoreTypeDef::Module(t) => {
+                self.stack.push(ComponentState::new(field.id));
+                self.module_type(t)?;
+                self.stack.pop();
+            }
+        }
+        Ok(())
+    }
+
+    fn ty(&mut self, field: &mut Type<'a>) -> Result<(), Error> {
+        match &mut field.def {
+            TypeDef::Defined(t) => {
+                self.defined_type(t)?;
+            }
+            TypeDef::Func(f) => {
+                for param in f.params.iter_mut() {
+                    self.component_val_type(&mut param.ty)?;
+                }
+
+                for result in f.results.iter_mut() {
+                    self.component_val_type(&mut result.ty)?;
+                }
+            }
+            TypeDef::Component(c) => {
+                self.stack.push(ComponentState::new(field.id));
+                self.component_type(c)?;
+                self.stack.pop();
+            }
+            TypeDef::Instance(i) => {
+                self.stack.push(ComponentState::new(field.id));
+                self.instance_type(i)?;
+                self.stack.pop();
+            }
+        }
+        Ok(())
+    }
+
+    fn component_type(&mut self, c: &mut ComponentType<'a>) -> Result<(), Error> {
+        self.resolve_prepending_aliases(
+            &mut c.decls,
+            |resolver, decl| match decl {
+                ComponentTypeDecl::Alias(alias) => resolver.alias(alias, false),
+                ComponentTypeDecl::CoreType(ty) => resolver.core_ty(ty),
+                ComponentTypeDecl::Type(ty) => resolver.ty(ty),
+                ComponentTypeDecl::Import(import) => resolver.item_sig(&mut import.item),
+                ComponentTypeDecl::Export(export) => resolver.item_sig(&mut export.item),
+            },
+            |state, decl| {
+                match decl {
+                    ComponentTypeDecl::Alias(alias) => {
+                        state.register_alias(alias)?;
+                    }
+                    ComponentTypeDecl::CoreType(ty) => {
+                        state.core_types.register(ty.id, "core type")?;
+                    }
+                    ComponentTypeDecl::Type(ty) => {
+                        state.types.register(ty.id, "type")?;
+                    }
+                    ComponentTypeDecl::Export(e) => {
+                        state.register_item_sig(&e.item)?;
+                    }
+                    ComponentTypeDecl::Import(i) => {
+                        state.register_item_sig(&i.item)?;
+                    }
+                }
+                Ok(())
+            },
+        )
+    }
+
+    fn instance_type(&mut self, c: &mut InstanceType<'a>) -> Result<(), Error> {
+        self.resolve_prepending_aliases(
+            &mut c.decls,
+            |resolver, decl| match decl {
+                InstanceTypeDecl::Alias(alias) => resolver.alias(alias, false),
+                InstanceTypeDecl::CoreType(ty) => resolver.core_ty(ty),
+                InstanceTypeDecl::Type(ty) => resolver.ty(ty),
+                InstanceTypeDecl::Export(export) => resolver.item_sig(&mut export.item),
+            },
+            |state, decl| {
+                match decl {
+                    InstanceTypeDecl::Alias(alias) => {
+                        state.register_alias(alias)?;
+                    }
+                    InstanceTypeDecl::CoreType(ty) => {
+                        state.core_types.register(ty.id, "core type")?;
+                    }
+                    InstanceTypeDecl::Type(ty) => {
+                        state.types.register(ty.id, "type")?;
+                    }
+                    InstanceTypeDecl::Export(export) => {
+                        state.register_item_sig(&export.item)?;
+                    }
+                }
+                Ok(())
+            },
+        )
+    }
+
+    fn core_item_ref<K>(&mut self, item: &mut CoreItemRef<'a, K>) -> Result<(), Error>
+    where
+        K: CoreItem + Copy,
+    {
+        // Check for not being an instance export reference
+        if item.export_name.is_none() {
+            self.resolve_ns(&mut item.idx, item.kind.ns())?;
+            return Ok(());
+        }
+
+        // This is a reference to a core instance export
+        let mut index = item.idx;
+        self.resolve_ns(&mut index, Ns::CoreInstance)?;
+
+        // Record an alias to reference the export
+        let span = item.idx.span();
+        let alias = Alias {
+            span,
+            id: None,
+            name: None,
+            target: AliasTarget::CoreExport {
+                instance: index,
+                name: item.export_name.unwrap(),
+                kind: item.kind.ns().into(),
+            },
+        };
+
+        index = Index::Num(self.current().register_alias(&alias)?, span);
+        self.aliases_to_insert.push(alias);
+
+        item.idx = index;
+        item.export_name = None;
+
+        Ok(())
+    }
+
+    fn component_item_ref<K>(&mut self, item: &mut ItemRef<'a, K>) -> Result<(), Error>
+    where
+        K: ComponentItem + Copy,
+    {
+        // Check for not being an instance export reference
+        if item.export_names.is_empty() {
+            self.resolve_ns(&mut item.idx, item.kind.ns())?;
+            return Ok(());
+        }
+
+        // This is a reference to an instance export
+        let mut index = item.idx;
+        self.resolve_ns(&mut index, Ns::Instance)?;
+
+        let span = item.idx.span();
+        for (pos, export_name) in item.export_names.iter().enumerate() {
+            // Record an alias to reference the export
+            let alias = Alias {
+                span,
+                id: None,
+                name: None,
+                target: AliasTarget::Export {
+                    instance: index,
+                    name: export_name,
+                    kind: if pos == item.export_names.len() - 1 {
+                        item.kind.ns().into()
+                    } else {
+                        ComponentExportAliasKind::Instance
+                    },
+                },
+            };
+
+            index = Index::Num(self.current().register_alias(&alias)?, span);
+            self.aliases_to_insert.push(alias);
+        }
+
+        item.idx = index;
+        item.export_names = Vec::new();
+
+        Ok(())
+    }
+
+    fn resolve_ns(&mut self, idx: &mut Index<'a>, ns: Ns) -> Result<(), Error> {
+        // Perform resolution on a local clone walking up the stack of components
+        // that we have. Note that a local clone is used since we don't want to use
+        // the parent's resolved index if a parent matches, instead we want to use
+        // the index of the alias that we will automatically insert.
+        let mut idx_clone = *idx;
+        for (depth, resolver) in self.stack.iter_mut().rev().enumerate() {
+            let depth = depth as u32;
+            let found = match resolver.resolve(ns, &mut idx_clone) {
+                Ok(idx) => idx,
+                // Try the next parent
+                Err(_) => continue,
+            };
+
+            // If this is the current component then no extra alias is necessary, so
+            // return success.
+            if depth == 0 {
+                *idx = idx_clone;
+                return Ok(());
+            }
+            let id = match idx {
+                Index::Id(id) => *id,
+                Index::Num(..) => unreachable!(),
+            };
+
+            // When resolution succeeds in a parent then an outer alias is
+            // automatically inserted here in this component.
+            let span = idx.span();
+            let alias = Alias {
+                span,
+                id: Some(id),
+                name: None,
+                target: AliasTarget::Outer {
+                    outer: Index::Num(depth, span),
+                    index: Index::Num(found, span),
+                    kind: ns.into(),
+                },
+            };
+            let local_index = self.current().register_alias(&alias)?;
+            self.aliases_to_insert.push(alias);
+            *idx = Index::Num(local_index, span);
+            return Ok(());
+        }
+
+        // If resolution in any parent failed then simply return the error from our
+        // local namespace
+        self.current().resolve(ns, idx)?;
+        unreachable!()
+    }
+
+    fn module_type(&mut self, ty: &mut ModuleType<'a>) -> Result<(), Error> {
+        return self.resolve_prepending_aliases(
+            &mut ty.decls,
+            |resolver, decl| match decl {
+                ModuleTypeDecl::Alias(alias) => resolver.alias(alias, true),
+                ModuleTypeDecl::Type(_) => Ok(()),
+                ModuleTypeDecl::Import(import) => resolve_item_sig(resolver, &mut import.item),
+                ModuleTypeDecl::Export(_, item) => resolve_item_sig(resolver, item),
+            },
+            |state, decl| {
+                match decl {
+                    ModuleTypeDecl::Alias(alias) => {
+                        state.register_alias(alias)?;
+                    }
+                    ModuleTypeDecl::Type(ty) => {
+                        state.core_types.register(ty.id, "type")?;
+                    }
+                    // Only the type namespace is populated within the module type
+                    // namespace so these are ignored here.
+                    ModuleTypeDecl::Import(_) | ModuleTypeDecl::Export(..) => {}
+                }
+                Ok(())
+            },
+        );
+
+        fn resolve_item_sig<'a>(
+            resolver: &Resolver<'a>,
+            sig: &mut core::ItemSig<'a>,
+        ) -> Result<(), Error> {
+            match &mut sig.kind {
+                core::ItemKind::Func(ty) | core::ItemKind::Tag(core::TagType::Exception(ty)) => {
+                    let idx = ty.index.as_mut().expect("index should be filled in");
+                    resolver
+                        .stack
+                        .last()
+                        .unwrap()
+                        .core_types
+                        .resolve(idx, "type")?;
+                }
+                core::ItemKind::Memory(_)
+                | core::ItemKind::Global(_)
+                | core::ItemKind::Table(_) => {}
+            }
+            Ok(())
+        }
+    }
+}
+
+impl<'a> ComponentState<'a> {
+    fn resolve(&mut self, ns: Ns, idx: &mut Index<'a>) -> Result<u32, Error> {
+        match ns {
+            Ns::CoreFunc => self.core_funcs.resolve(idx, "core func"),
+            Ns::CoreGlobal => self.core_globals.resolve(idx, "core global"),
+            Ns::CoreTable => self.core_tables.resolve(idx, "core table"),
+            Ns::CoreMemory => self.core_memories.resolve(idx, "core memory"),
+            Ns::CoreType => self.core_types.resolve(idx, "core type"),
+            Ns::CoreTag => self.core_tags.resolve(idx, "core tag"),
+            Ns::CoreInstance => self.core_instances.resolve(idx, "core instance"),
+            Ns::CoreModule => self.core_modules.resolve(idx, "core module"),
+            Ns::Func => self.funcs.resolve(idx, "func"),
+            Ns::Type => self.types.resolve(idx, "type"),
+            Ns::Instance => self.instances.resolve(idx, "instance"),
+            Ns::Component => self.components.resolve(idx, "component"),
+            Ns::Value => self.values.resolve(idx, "value"),
+        }
+    }
+
+    /// Assign an index to the given field.
+    fn register(&mut self, item: &ComponentField<'a>) -> Result<(), Error> {
+        match item {
+            ComponentField::CoreModule(m) => self.core_modules.register(m.id, "core module")?,
+            ComponentField::CoreInstance(i) => {
+                self.core_instances.register(i.id, "core instance")?
+            }
+            ComponentField::CoreType(t) => self.core_types.register(t.id, "core type")?,
+            ComponentField::Component(c) => self.components.register(c.id, "component")?,
+            ComponentField::Instance(i) => self.instances.register(i.id, "instance")?,
+            ComponentField::Alias(a) => self.register_alias(a)?,
+            ComponentField::Type(t) => self.types.register(t.id, "type")?,
+            ComponentField::CanonicalFunc(f) => match &f.kind {
+                CanonicalFuncKind::Lift { .. } => self.funcs.register(f.id, "func")?,
+                CanonicalFuncKind::Lower(_) => self.core_funcs.register(f.id, "core func")?,
+            },
+            ComponentField::CoreFunc(_) | ComponentField::Func(_) => {
+                unreachable!("should be expanded already")
+            }
+            ComponentField::Start(s) => {
+                for r in &s.results {
+                    self.values.register(*r, "value")?;
+                }
+                return Ok(());
+            }
+            ComponentField::Import(i) => self.register_item_sig(&i.item)?,
+            ComponentField::Export(e) => match &e.kind {
+                ComponentExportKind::CoreModule(_) => {
+                    self.core_modules.register(e.id, "core module")?
+                }
+                ComponentExportKind::Func(_) => self.funcs.register(e.id, "func")?,
+                ComponentExportKind::Instance(_) => self.instances.register(e.id, "instance")?,
+                ComponentExportKind::Value(_) => self.values.register(e.id, "value")?,
+                ComponentExportKind::Component(_) => self.components.register(e.id, "component")?,
+                ComponentExportKind::Type(_) => self.types.register(e.id, "type")?,
+            },
+            ComponentField::Custom(_) => return Ok(()),
+        };
+
+        Ok(())
+    }
+
+    fn register_alias(&mut self, alias: &Alias<'a>) -> Result<u32, Error> {
+        match alias.target {
+            AliasTarget::Export { kind, .. } => match kind {
+                ComponentExportAliasKind::CoreModule => {
+                    self.core_modules.register(alias.id, "core module")
+                }
+                ComponentExportAliasKind::Func => self.funcs.register(alias.id, "func"),
+                ComponentExportAliasKind::Value => self.values.register(alias.id, "value"),
+                ComponentExportAliasKind::Type => self.types.register(alias.id, "type"),
+                ComponentExportAliasKind::Component => {
+                    self.components.register(alias.id, "component")
+                }
+                ComponentExportAliasKind::Instance => self.instances.register(alias.id, "instance"),
+            },
+            AliasTarget::CoreExport { kind, .. } => match kind {
+                core::ExportKind::Func => self.core_funcs.register(alias.id, "core func"),
+                core::ExportKind::Table => self.core_tables.register(alias.id, "core table"),
+                core::ExportKind::Memory => self.core_memories.register(alias.id, "core memory"),
+                core::ExportKind::Global => self.core_globals.register(alias.id, "core global"),
+                core::ExportKind::Tag => self.core_tags.register(alias.id, "core tag"),
+            },
+            AliasTarget::Outer { kind, .. } => match kind {
+                ComponentOuterAliasKind::CoreModule => {
+                    self.core_modules.register(alias.id, "core module")
+                }
+                ComponentOuterAliasKind::CoreType => {
+                    self.core_types.register(alias.id, "core type")
+                }
+                ComponentOuterAliasKind::Type => self.types.register(alias.id, "type"),
+                ComponentOuterAliasKind::Component => {
+                    self.components.register(alias.id, "component")
+                }
+            },
+        }
+    }
+}
+
+#[derive(PartialEq, Eq, Hash, Copy, Clone, Debug)]
+enum Ns {
+    CoreFunc,
+    CoreGlobal,
+    CoreTable,
+    CoreMemory,
+    CoreType,
+    CoreTag,
+    CoreInstance,
+    CoreModule,
+    Func,
+    Type,
+    Instance,
+    Component,
+    Value,
+}
+
+trait ComponentItem {
+    fn ns(&self) -> Ns;
+}
+
+trait CoreItem {
+    fn ns(&self) -> Ns;
+}
+
+macro_rules! component_item {
+    ($kw:path, $kind:ident) => {
+        impl ComponentItem for $kw {
+            fn ns(&self) -> Ns {
+                Ns::$kind
+            }
+        }
+    };
+}
+
+macro_rules! core_item {
+    ($kw:path, $kind:ident) => {
+        impl CoreItem for $kw {
+            fn ns(&self) -> Ns {
+                Ns::$kind
+            }
+        }
+    };
+}
+
+component_item!(kw::func, Func);
+component_item!(kw::r#type, Type);
+component_item!(kw::r#instance, Instance);
+component_item!(kw::component, Component);
+component_item!(kw::value, Value);
+component_item!(kw::module, CoreModule);
+
+core_item!(kw::func, CoreFunc);
+core_item!(kw::memory, CoreMemory);
+core_item!(kw::r#type, CoreType);
+core_item!(kw::r#instance, CoreInstance);
+
+impl From<Ns> for ComponentExportAliasKind {
+    fn from(ns: Ns) -> Self {
+        match ns {
+            Ns::CoreModule => Self::CoreModule,
+            Ns::Func => Self::Func,
+            Ns::Type => Self::Type,
+            Ns::Instance => Self::Instance,
+            Ns::Component => Self::Component,
+            Ns::Value => Self::Value,
+            _ => unreachable!("not a component exportable namespace"),
+        }
+    }
+}
+
+impl From<Ns> for ComponentOuterAliasKind {
+    fn from(ns: Ns) -> Self {
+        match ns {
+            Ns::CoreModule => Self::CoreModule,
+            Ns::CoreType => Self::CoreType,
+            Ns::Type => Self::Type,
+            Ns::Component => Self::Component,
+            _ => unreachable!("not an outer alias namespace"),
+        }
+    }
+}
+
+impl From<Ns> for core::ExportKind {
+    fn from(ns: Ns) -> Self {
+        match ns {
+            Ns::CoreFunc => Self::Func,
+            Ns::CoreTable => Self::Table,
+            Ns::CoreGlobal => Self::Global,
+            Ns::CoreMemory => Self::Memory,
+            Ns::CoreTag => Self::Tag,
+            _ => unreachable!("not a core exportable namespace"),
+        }
+    }
+}
+
+impl From<ComponentOuterAliasKind> for Ns {
+    fn from(kind: ComponentOuterAliasKind) -> Self {
+        match kind {
+            ComponentOuterAliasKind::CoreModule => Self::CoreModule,
+            ComponentOuterAliasKind::CoreType => Self::CoreType,
+            ComponentOuterAliasKind::Type => Self::Type,
+            ComponentOuterAliasKind::Component => Self::Component,
+        }
+    }
+}
+
+impl CoreItem for core::ExportKind {
+    fn ns(&self) -> Ns {
+        match self {
+            Self::Func => Ns::CoreFunc,
+            Self::Table => Ns::CoreTable,
+            Self::Global => Ns::CoreGlobal,
+            Self::Memory => Ns::CoreMemory,
+            Self::Tag => Ns::CoreTag,
+        }
+    }
+}
diff --git a/third_party/rust/wast/src/component/types.rs b/third_party/rust/wast/src/component/types.rs
new file mode 100644
index 0000000000..0ff8cc0183
--- /dev/null
+++ b/third_party/rust/wast/src/component/types.rs
@@ -0,0 +1,965 @@
+use crate::component::*;
+use crate::core;
+use crate::kw;
+use crate::parser::Lookahead1;
+use crate::parser::Peek;
+use crate::parser::{Parse, Parser, Result};
+use crate::token::Index;
+use crate::token::LParen;
+use crate::token::{Id, NameAnnotation, Span};
+
+/// A core type declaration.
+#[derive(Debug)]
+pub struct CoreType<'a> {
+    /// Where this type was defined.
+    pub span: Span,
+    /// An optional identifier to refer to this `core type` by as part of name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this type stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// The core type's definition.
+    pub def: CoreTypeDef<'a>,
+}
+
+impl<'a> Parse<'a> for CoreType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::core>()?.0;
+        parser.parse::<kw::r#type>()?;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let def = parser.parens(|p| p.parse())?;
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            def,
+        })
+    }
+}
+
+/// Represents a core type definition.
+///
+/// In the future this may be removed when module types are a part of
+/// a core module.
+#[derive(Debug)]
+pub enum CoreTypeDef<'a> {
+    /// The type definition is one of the core types.
+    Def(core::TypeDef<'a>),
+    /// The type definition is a module type.
+    Module(ModuleType<'a>),
+}
+
+impl<'a> Parse<'a> for CoreTypeDef<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<kw::module>() {
+            parser.parse::<kw::module>()?;
+            Ok(Self::Module(parser.parse()?))
+        } else {
+            Ok(Self::Def(parser.parse()?))
+        }
+    }
+}
+
+/// A type definition for a core module.
+#[derive(Debug)]
+pub struct ModuleType<'a> {
+    /// The declarations of the module type.
+    pub decls: Vec<ModuleTypeDecl<'a>>,
+}
+
+impl<'a> Parse<'a> for ModuleType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.depth_check()?;
+        Ok(Self {
+            decls: parser.parse()?,
+        })
+    }
+}
+
+/// The declarations of a [`ModuleType`].
+#[derive(Debug)]
+pub enum ModuleTypeDecl<'a> {
+    /// A core type.
+    Type(core::Type<'a>),
+    /// An alias local to the component type.
+    Alias(Alias<'a>),
+    /// An import.
+    Import(core::Import<'a>),
+    /// An export.
+    Export(&'a str, core::ItemSig<'a>),
+}
+
+impl<'a> Parse<'a> for ModuleTypeDecl<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::r#type>() {
+            Ok(Self::Type(parser.parse()?))
+        } else if l.peek::<kw::alias>() {
+            Ok(Self::Alias(Alias::parse_outer_core_type_alias(parser)?))
+        } else if l.peek::<kw::import>() {
+            Ok(Self::Import(parser.parse()?))
+        } else if l.peek::<kw::export>() {
+            parser.parse::<kw::export>()?;
+            let name = parser.parse()?;
+            let et = parser.parens(|parser| parser.parse())?;
+            Ok(Self::Export(name, et))
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+impl<'a> Parse<'a> for Vec<ModuleTypeDecl<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut decls = Vec::new();
+        while !parser.is_empty() {
+            decls.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(decls)
+    }
+}
+
+/// A type declaration in a component.
+#[derive(Debug)]
+pub struct Type<'a> {
+    /// Where this type was defined.
+    pub span: Span,
+    /// An optional identifier to refer to this `type` by as part of name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// An optional name for this type stored in the custom `name` section.
+    pub name: Option<NameAnnotation<'a>>,
+    /// If present, inline export annotations which indicate names this
+    /// definition should be exported under.
+    pub exports: InlineExport<'a>,
+    /// The type definition.
+    pub def: TypeDef<'a>,
+}
+
+impl<'a> Parse<'a> for Type<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::r#type>()?.0;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let exports = parser.parse()?;
+        let def = parser.parse()?;
+
+        Ok(Self {
+            span,
+            id,
+            name,
+            exports,
+            def,
+        })
+    }
+}
+
+/// A definition of a component type.
+#[derive(Debug)]
+pub enum TypeDef<'a> {
+    /// A defined value type.
+    Defined(ComponentDefinedType<'a>),
+    /// A component function type.
+    Func(ComponentFunctionType<'a>),
+    /// A component type.
+    Component(ComponentType<'a>),
+    /// An instance type.
+    Instance(InstanceType<'a>),
+}
+
+impl<'a> Parse<'a> for TypeDef<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<LParen>() {
+            parser.parens(|parser| {
+                let mut l = parser.lookahead1();
+                if l.peek::<kw::func>() {
+                    parser.parse::<kw::func>()?;
+                    Ok(Self::Func(parser.parse()?))
+                } else if l.peek::<kw::component>() {
+                    parser.parse::<kw::component>()?;
+                    Ok(Self::Component(parser.parse()?))
+                } else if l.peek::<kw::instance>() {
+                    parser.parse::<kw::instance>()?;
+                    Ok(Self::Instance(parser.parse()?))
+                } else {
+                    Ok(Self::Defined(ComponentDefinedType::parse_non_primitive(
+                        parser, l,
+                    )?))
+                }
+            })
+        } else {
+            // Only primitive types have no parens
+            Ok(Self::Defined(ComponentDefinedType::Primitive(
+                parser.parse()?,
+            )))
+        }
+    }
+}
+
+/// A primitive value type.
+#[allow(missing_docs)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PrimitiveValType {
+    Bool,
+    S8,
+    U8,
+    S16,
+    U16,
+    S32,
+    U32,
+    S64,
+    U64,
+    Float32,
+    Float64,
+    Char,
+    String,
+}
+
+impl<'a> Parse<'a> for PrimitiveValType {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::bool_>() {
+            parser.parse::<kw::bool_>()?;
+            Ok(Self::Bool)
+        } else if l.peek::<kw::s8>() {
+            parser.parse::<kw::s8>()?;
+            Ok(Self::S8)
+        } else if l.peek::<kw::u8>() {
+            parser.parse::<kw::u8>()?;
+            Ok(Self::U8)
+        } else if l.peek::<kw::s16>() {
+            parser.parse::<kw::s16>()?;
+            Ok(Self::S16)
+        } else if l.peek::<kw::u16>() {
+            parser.parse::<kw::u16>()?;
+            Ok(Self::U16)
+        } else if l.peek::<kw::s32>() {
+            parser.parse::<kw::s32>()?;
+            Ok(Self::S32)
+        } else if l.peek::<kw::u32>() {
+            parser.parse::<kw::u32>()?;
+            Ok(Self::U32)
+        } else if l.peek::<kw::s64>() {
+            parser.parse::<kw::s64>()?;
+            Ok(Self::S64)
+        } else if l.peek::<kw::u64>() {
+            parser.parse::<kw::u64>()?;
+            Ok(Self::U64)
+        } else if l.peek::<kw::float32>() {
+            parser.parse::<kw::float32>()?;
+            Ok(Self::Float32)
+        } else if l.peek::<kw::float64>() {
+            parser.parse::<kw::float64>()?;
+            Ok(Self::Float64)
+        } else if l.peek::<kw::char>() {
+            parser.parse::<kw::char>()?;
+            Ok(Self::Char)
+        } else if l.peek::<kw::string>() {
+            parser.parse::<kw::string>()?;
+            Ok(Self::String)
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+impl Peek for PrimitiveValType {
+    fn peek(cursor: crate::parser::Cursor<'_>) -> bool {
+        matches!(
+            cursor.keyword(),
+            Some(("bool", _))
+                | Some(("s8", _))
+                | Some(("u8", _))
+                | Some(("s16", _))
+                | Some(("u16", _))
+                | Some(("s32", _))
+                | Some(("u32", _))
+                | Some(("s64", _))
+                | Some(("u64", _))
+                | Some(("float32", _))
+                | Some(("float64", _))
+                | Some(("char", _))
+                | Some(("string", _))
+        )
+    }
+
+    fn display() -> &'static str {
+        "primitive value type"
+    }
+}
+
+/// A component value type.
+#[allow(missing_docs)]
+#[derive(Debug)]
+pub enum ComponentValType<'a> {
+    /// The value type is an inline defined type.
+    Inline(ComponentDefinedType<'a>),
+    /// The value type is an index reference to a defined type.
+    Ref(Index<'a>),
+}
+
+impl<'a> Parse<'a> for ComponentValType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<Index<'_>>() {
+            Ok(Self::Ref(parser.parse()?))
+        } else {
+            Ok(Self::Inline(InlineComponentValType::parse(parser)?.0))
+        }
+    }
+}
+
+impl Peek for ComponentValType<'_> {
+    fn peek(cursor: crate::parser::Cursor<'_>) -> bool {
+        Index::peek(cursor) || ComponentDefinedType::peek(cursor)
+    }
+
+    fn display() -> &'static str {
+        "component value type"
+    }
+}
+
+/// An inline-only component value type.
+///
+/// This variation does not parse type indexes.
+#[allow(missing_docs)]
+#[derive(Debug)]
+pub struct InlineComponentValType<'a>(ComponentDefinedType<'a>);
+
+impl<'a> Parse<'a> for InlineComponentValType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<LParen>() {
+            parser.parens(|parser| {
+                Ok(Self(ComponentDefinedType::parse_non_primitive(
+                    parser,
+                    parser.lookahead1(),
+                )?))
+            })
+        } else {
+            Ok(Self(ComponentDefinedType::Primitive(parser.parse()?)))
+        }
+    }
+}
+
+// A component defined type.
+#[allow(missing_docs)]
+#[derive(Debug)]
+pub enum ComponentDefinedType<'a> {
+    Primitive(PrimitiveValType),
+    Record(Record<'a>),
+    Variant(Variant<'a>),
+    List(List<'a>),
+    Tuple(Tuple<'a>),
+    Flags(Flags<'a>),
+    Enum(Enum<'a>),
+    Union(Union<'a>),
+    Option(OptionType<'a>),
+    Result(ResultType<'a>),
+}
+
+impl<'a> ComponentDefinedType<'a> {
+    fn parse_non_primitive(parser: Parser<'a>, mut l: Lookahead1<'a>) -> Result<Self> {
+        parser.depth_check()?;
+        if l.peek::<kw::record>() {
+            Ok(Self::Record(parser.parse()?))
+        } else if l.peek::<kw::variant>() {
+            Ok(Self::Variant(parser.parse()?))
+        } else if l.peek::<kw::list>() {
+            Ok(Self::List(parser.parse()?))
+        } else if l.peek::<kw::tuple>() {
+            Ok(Self::Tuple(parser.parse()?))
+        } else if l.peek::<kw::flags>() {
+            Ok(Self::Flags(parser.parse()?))
+        } else if l.peek::<kw::enum_>() {
+            Ok(Self::Enum(parser.parse()?))
+        } else if l.peek::<kw::union>() {
+            Ok(Self::Union(parser.parse()?))
+        } else if l.peek::<kw::option>() {
+            Ok(Self::Option(parser.parse()?))
+        } else if l.peek::<kw::result>() {
+            Ok(Self::Result(parser.parse()?))
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+impl Default for ComponentDefinedType<'_> {
+    fn default() -> Self {
+        Self::Primitive(PrimitiveValType::Bool)
+    }
+}
+
+impl Peek for ComponentDefinedType<'_> {
+    fn peek(cursor: crate::parser::Cursor<'_>) -> bool {
+        if PrimitiveValType::peek(cursor) {
+            return true;
+        }
+
+        match cursor.lparen() {
+            Some(cursor) => matches!(
+                cursor.keyword(),
+                Some(("record", _))
+                    | Some(("variant", _))
+                    | Some(("list", _))
+                    | Some(("tuple", _))
+                    | Some(("flags", _))
+                    | Some(("enum", _))
+                    | Some(("union", _))
+                    | Some(("option", _))
+                    | Some(("result", _))
+            ),
+            None => false,
+        }
+    }
+
+    fn display() -> &'static str {
+        "component defined type"
+    }
+}
+
+/// A record defined type.
+#[derive(Debug)]
+pub struct Record<'a> {
+    /// The fields of the record.
+    pub fields: Vec<RecordField<'a>>,
+}
+
+impl<'a> Parse<'a> for Record<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::record>()?;
+        let mut fields = Vec::new();
+        while !parser.is_empty() {
+            fields.push(parser.parens(|p| p.parse())?);
+        }
+        Ok(Self { fields })
+    }
+}
+
+/// A record type field.
+#[derive(Debug)]
+pub struct RecordField<'a> {
+    /// The name of the field.
+    pub name: &'a str,
+    /// The type of the field.
+    pub ty: ComponentValType<'a>,
+}
+
+impl<'a> Parse<'a> for RecordField<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::field>()?;
+        Ok(Self {
+            name: parser.parse()?,
+            ty: parser.parse()?,
+        })
+    }
+}
+
+/// A variant defined type.
+#[derive(Debug)]
+pub struct Variant<'a> {
+    /// The cases of the variant type.
+    pub cases: Vec<VariantCase<'a>>,
+}
+
+impl<'a> Parse<'a> for Variant<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::variant>()?;
+        let mut cases = Vec::new();
+        while !parser.is_empty() {
+            cases.push(parser.parens(|p| p.parse())?);
+        }
+        Ok(Self { cases })
+    }
+}
+
+/// A case of a variant type.
+#[derive(Debug)]
+pub struct VariantCase<'a> {
+    /// Where this `case` was defined
+    pub span: Span,
+    /// An optional identifier to refer to this case by as part of name
+    /// resolution.
+    pub id: Option<Id<'a>>,
+    /// The name of the case.
+    pub name: &'a str,
+    /// The optional type of the case.
+    pub ty: Option<ComponentValType<'a>>,
+    /// The optional refinement.
+    pub refines: Option<Refinement<'a>>,
+}
+
+impl<'a> Parse<'a> for VariantCase<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::case>()?.0;
+        let id = parser.parse()?;
+        let name = parser.parse()?;
+        let ty = parser.parse()?;
+        let refines = if !parser.is_empty() {
+            Some(parser.parse()?)
+        } else {
+            None
+        };
+        Ok(Self {
+            span,
+            id,
+            name,
+            ty,
+            refines,
+        })
+    }
+}
+
+/// A refinement for a variant case.
+#[derive(Debug)]
+pub enum Refinement<'a> {
+    /// The refinement is referenced by index.
+    Index(Span, Index<'a>),
+    /// The refinement has been resolved to an index into
+    /// the cases of the variant.
+    Resolved(u32),
+}
+
+impl<'a> Parse<'a> for Refinement<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parens(|parser| {
+            let span = parser.parse::<kw::refines>()?.0;
+            let id = parser.parse()?;
+            Ok(Self::Index(span, id))
+        })
+    }
+}
+
+/// A list type.
+#[derive(Debug)]
+pub struct List<'a> {
+    /// The element type of the array.
+    pub element: Box<ComponentValType<'a>>,
+}
+
+impl<'a> Parse<'a> for List<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::list>()?;
+        Ok(Self {
+            element: Box::new(parser.parse()?),
+        })
+    }
+}
+
+/// A tuple type.
+#[derive(Debug)]
+pub struct Tuple<'a> {
+    /// The types of the fields of the tuple.
+    pub fields: Vec<ComponentValType<'a>>,
+}
+
+impl<'a> Parse<'a> for Tuple<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::tuple>()?;
+        let mut fields = Vec::new();
+        while !parser.is_empty() {
+            fields.push(parser.parse()?);
+        }
+        Ok(Self { fields })
+    }
+}
+
+/// A flags type.
+#[derive(Debug)]
+pub struct Flags<'a> {
+    /// The names of the individual flags.
+    pub names: Vec<&'a str>,
+}
+
+impl<'a> Parse<'a> for Flags<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::flags>()?;
+        let mut names = Vec::new();
+        while !parser.is_empty() {
+            names.push(parser.parse()?);
+        }
+        Ok(Self { names })
+    }
+}
+
+/// An enum type.
+#[derive(Debug)]
+pub struct Enum<'a> {
+    /// The tag names of the enum.
+    pub names: Vec<&'a str>,
+}
+
+impl<'a> Parse<'a> for Enum<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::enum_>()?;
+        let mut names = Vec::new();
+        while !parser.is_empty() {
+            names.push(parser.parse()?);
+        }
+        Ok(Self { names })
+    }
+}
+
+/// A union type.
+#[derive(Debug)]
+pub struct Union<'a> {
+    /// The types of the union.
+    pub types: Vec<ComponentValType<'a>>,
+}
+
+impl<'a> Parse<'a> for Union<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::union>()?;
+        let mut types = Vec::new();
+        while !parser.is_empty() {
+            types.push(parser.parse()?);
+        }
+        Ok(Self { types })
+    }
+}
+
+/// An optional type.
+#[derive(Debug)]
+pub struct OptionType<'a> {
+    /// The type of the value, when a value is present.
+    pub element: Box<ComponentValType<'a>>,
+}
+
+impl<'a> Parse<'a> for OptionType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::option>()?;
+        Ok(Self {
+            element: Box::new(parser.parse()?),
+        })
+    }
+}
+
+/// A result type.
+#[derive(Debug)]
+pub struct ResultType<'a> {
+    /// The type on success.
+    pub ok: Option<Box<ComponentValType<'a>>>,
+    /// The type on failure.
+    pub err: Option<Box<ComponentValType<'a>>>,
+}
+
+impl<'a> Parse<'a> for ResultType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::result>()?;
+
+        let ok: Option<ComponentValType> = parser.parse()?;
+        let err: Option<ComponentValType> = if parser.peek::<LParen>() {
+            Some(parser.parens(|parser| {
+                parser.parse::<kw::error>()?;
+                parser.parse()
+            })?)
+        } else {
+            None
+        };
+
+        Ok(Self {
+            ok: ok.map(Box::new),
+            err: err.map(Box::new),
+        })
+    }
+}
+
+/// A component function type with parameters and result.
+#[derive(Debug)]
+pub struct ComponentFunctionType<'a> {
+    /// The parameters of a function, optionally each having an identifier for
+    /// name resolution and a name for the custom `name` section.
+    pub params: Box<[ComponentFunctionParam<'a>]>,
+    /// The result of a function, optionally each having an identifier for
+    /// name resolution and a name for the custom `name` section.
+    pub results: Box<[ComponentFunctionResult<'a>]>,
+}
+
+impl<'a> Parse<'a> for ComponentFunctionType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut params: Vec<ComponentFunctionParam> = Vec::new();
+        while parser.peek2::<kw::param>() {
+            params.push(parser.parens(|p| p.parse())?);
+        }
+
+        let mut results: Vec<ComponentFunctionResult> = Vec::new();
+        while parser.peek2::<kw::result>() {
+            results.push(parser.parens(|p| p.parse())?);
+        }
+
+        Ok(Self {
+            params: params.into(),
+            results: results.into(),
+        })
+    }
+}
+
+/// A parameter of a [`ComponentFunctionType`].
+#[derive(Debug)]
+pub struct ComponentFunctionParam<'a> {
+    /// The name of the parameter
+    pub name: &'a str,
+    /// The type of the parameter.
+    pub ty: ComponentValType<'a>,
+}
+
+impl<'a> Parse<'a> for ComponentFunctionParam<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::param>()?;
+        Ok(Self {
+            name: parser.parse()?,
+            ty: parser.parse()?,
+        })
+    }
+}
+
+/// A result of a [`ComponentFunctionType`].
+#[derive(Debug)]
+pub struct ComponentFunctionResult<'a> {
+    /// An optionally-specified name of this result
+    pub name: Option<&'a str>,
+    /// The type of the result.
+    pub ty: ComponentValType<'a>,
+}
+
+impl<'a> Parse<'a> for ComponentFunctionResult<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.parse::<kw::result>()?;
+        Ok(Self {
+            name: parser.parse()?,
+            ty: parser.parse()?,
+        })
+    }
+}
+
+/// The type of an exported item from an component or instance type.
+#[derive(Debug)]
+pub struct ComponentExportType<'a> {
+    /// Where this export was defined.
+    pub span: Span,
+    /// The name of this export.
+    pub name: &'a str,
+    /// The optional URL of this export.
+    pub url: Option<&'a str>,
+    /// The signature of the item.
+    pub item: ItemSig<'a>,
+}
+
+impl<'a> Parse<'a> for ComponentExportType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let span = parser.parse::<kw::export>()?.0;
+        let id = parser.parse()?;
+        let debug_name = parser.parse()?;
+        let name = parser.parse()?;
+        let url = parser.parse()?;
+        let item = parser.parens(|p| {
+            let mut item = p.parse::<ItemSigNoName<'_>>()?.0;
+            item.id = id;
+            item.name = debug_name;
+            Ok(item)
+        })?;
+        Ok(Self {
+            span,
+            name,
+            url,
+            item,
+        })
+    }
+}
+
+/// A type definition for a component type.
+#[derive(Debug, Default)]
+pub struct ComponentType<'a> {
+    /// The declarations of the component type.
+    pub decls: Vec<ComponentTypeDecl<'a>>,
+}
+
+impl<'a> Parse<'a> for ComponentType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.depth_check()?;
+        Ok(Self {
+            decls: parser.parse()?,
+        })
+    }
+}
+
+/// A declaration of a component type.
+#[derive(Debug)]
+pub enum ComponentTypeDecl<'a> {
+    /// A core type definition local to the component type.
+    CoreType(CoreType<'a>),
+    /// A type definition local to the component type.
+    Type(Type<'a>),
+    /// An alias local to the component type.
+    Alias(Alias<'a>),
+    /// An import of the component type.
+    Import(ComponentImport<'a>),
+    /// An export of the component type.
+    Export(ComponentExportType<'a>),
+}
+
+impl<'a> Parse<'a> for ComponentTypeDecl<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::core>() {
+            Ok(Self::CoreType(parser.parse()?))
+        } else if l.peek::<kw::r#type>() {
+            Ok(Self::Type(parser.parse()?))
+        } else if l.peek::<kw::alias>() {
+            Ok(Self::Alias(parser.parse()?))
+        } else if l.peek::<kw::import>() {
+            Ok(Self::Import(parser.parse()?))
+        } else if l.peek::<kw::export>() {
+            Ok(Self::Export(parser.parse()?))
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+impl<'a> Parse<'a> for Vec<ComponentTypeDecl<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut decls = Vec::new();
+        while !parser.is_empty() {
+            decls.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(decls)
+    }
+}
+
+/// A type definition for an instance type.
+#[derive(Debug)]
+pub struct InstanceType<'a> {
+    /// The declarations of the instance type.
+    pub decls: Vec<InstanceTypeDecl<'a>>,
+}
+
+impl<'a> Parse<'a> for InstanceType<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.depth_check()?;
+        Ok(Self {
+            decls: parser.parse()?,
+        })
+    }
+}
+
+/// A declaration of an instance type.
+#[derive(Debug)]
+pub enum InstanceTypeDecl<'a> {
+    /// A core type definition local to the component type.
+    CoreType(CoreType<'a>),
+    /// A type definition local to the instance type.
+    Type(Type<'a>),
+    /// An alias local to the instance type.
+    Alias(Alias<'a>),
+    /// An export of the instance type.
+    Export(ComponentExportType<'a>),
+}
+
+impl<'a> Parse<'a> for InstanceTypeDecl<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut l = parser.lookahead1();
+        if l.peek::<kw::core>() {
+            Ok(Self::CoreType(parser.parse()?))
+        } else if l.peek::<kw::r#type>() {
+            Ok(Self::Type(parser.parse()?))
+        } else if l.peek::<kw::alias>() {
+            Ok(Self::Alias(parser.parse()?))
+        } else if l.peek::<kw::export>() {
+            Ok(Self::Export(parser.parse()?))
+        } else {
+            Err(l.error())
+        }
+    }
+}
+
+impl<'a> Parse<'a> for Vec<InstanceTypeDecl<'a>> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let mut decls = Vec::new();
+        while !parser.is_empty() {
+            decls.push(parser.parens(|parser| parser.parse())?);
+        }
+        Ok(decls)
+    }
+}
+
+/// A value type declaration used for values in import signatures.
+#[derive(Debug)]
+pub struct ComponentValTypeUse<'a>(pub ComponentValType<'a>);
+
+impl<'a> Parse<'a> for ComponentValTypeUse<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        match ComponentTypeUse::<'a, InlineComponentValType<'a>>::parse(parser)? {
+            ComponentTypeUse::Ref(i) => Ok(Self(ComponentValType::Ref(i.idx))),
+            ComponentTypeUse::Inline(t) => Ok(Self(ComponentValType::Inline(t.0))),
+        }
+    }
+}
+
+/// A reference to a core type defined in this component.
+///
+/// This is the same as `TypeUse`, but accepts `$T` as shorthand for
+/// `(type $T)`.
+#[derive(Debug, Clone)]
+pub enum CoreTypeUse<'a, T> {
+    /// The type that we're referencing.
+    Ref(CoreItemRef<'a, kw::r#type>),
+    /// The inline type.
+    Inline(T),
+}
+
+impl<'a, T: Parse<'a>> Parse<'a> for CoreTypeUse<'a, T> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        // Here the core context is assumed, so no core prefix is expected
+        if parser.peek::<LParen>() && parser.peek2::<CoreItemRef<'a, kw::r#type>>() {
+            Ok(Self::Ref(parser.parens(|parser| parser.parse())?))
+        } else {
+            Ok(Self::Inline(parser.parse()?))
+        }
+    }
+}
+
+impl<T> Default for CoreTypeUse<'_, T> {
+    fn default() -> Self {
+        let span = Span::from_offset(0);
+        Self::Ref(CoreItemRef {
+            idx: Index::Num(0, span),
+            kind: kw::r#type(span),
+            export_name: None,
+        })
+    }
+}
+
+/// A reference to a type defined in this component.
+///
+/// This is the same as `TypeUse`, but accepts `$T` as shorthand for
+/// `(type $T)`.
+#[derive(Debug, Clone)]
+pub enum ComponentTypeUse<'a, T> {
+    /// The type that we're referencing.
+    Ref(ItemRef<'a, kw::r#type>),
+    /// The inline type.
+    Inline(T),
+}
+
+impl<'a, T: Parse<'a>> Parse<'a> for ComponentTypeUse<'a, T> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        if parser.peek::<LParen>() && parser.peek2::<ItemRef<'a, kw::r#type>>() {
+            Ok(Self::Ref(parser.parens(|parser| parser.parse())?))
+        } else {
+            Ok(Self::Inline(parser.parse()?))
+        }
+    }
+}
+
+impl<T> Default for ComponentTypeUse<'_, T> {
+    fn default() -> Self {
+        let span = Span::from_offset(0);
+        Self::Ref(ItemRef {
+            idx: Index::Num(0, span),
+            kind: kw::r#type(span),
+            export_names: Vec::new(),
+        })
+    }
+}
diff --git a/third_party/rust/wast/src/component/wast.rs b/third_party/rust/wast/src/component/wast.rs
new file mode 100644
index 0000000000..8409a6c969
--- /dev/null
+++ b/third_party/rust/wast/src/component/wast.rs
@@ -0,0 +1,166 @@
+use crate::kw;
+use crate::parser::{Cursor, Parse, Parser, Peek, Result};
+use crate::token::{Float32, Float64};
+
+/// Expression that can be used inside of `invoke` expressions for core wasm
+/// functions.
+#[derive(Debug)]
+#[allow(missing_docs)]
+pub enum WastVal<'a> {
+    Bool(bool),
+    U8(u8),
+    S8(i8),
+    U16(u16),
+    S16(i16),
+    U32(u32),
+    S32(i32),
+    U64(u64),
+    S64(i64),
+    Float32(Float32),
+    Float64(Float64),
+    Char(char),
+    String(&'a str),
+    List(Vec<WastVal<'a>>),
+    Record(Vec<(&'a str, WastVal<'a>)>),
+    Tuple(Vec<WastVal<'a>>),
+    Variant(&'a str, Option<Box<WastVal<'a>>>),
+    Enum(&'a str),
+    Union(u32, Box<WastVal<'a>>),
+    Option(Option<Box<WastVal<'a>>>),
+    Result(Result<Option<Box<WastVal<'a>>>, Option<Box<WastVal<'a>>>>),
+    Flags(Vec<&'a str>),
+}
+
+static CASES: &[(&str, fn(Parser<'_>) -> Result<WastVal<'_>>)] = {
+    use WastVal::*;
+    &[
+        ("bool.const", |p| {
+            let mut l = p.lookahead1();
+            if l.peek::<kw::true_>() {
+                p.parse::<kw::true_>()?;
+                Ok(Bool(true))
+            } else if l.peek::<kw::false_>() {
+                p.parse::<kw::false_>()?;
+                Ok(Bool(false))
+            } else {
+                Err(l.error())
+            }
+        }),
+        ("u8.const", |p| Ok(U8(p.parse()?))),
+        ("s8.const", |p| Ok(S8(p.parse()?))),
+        ("u16.const", |p| Ok(U16(p.parse()?))),
+        ("s16.const", |p| Ok(S16(p.parse()?))),
+        ("u32.const", |p| Ok(U32(p.parse()?))),
+        ("s32.const", |p| Ok(S32(p.parse()?))),
+        ("u64.const", |p| Ok(U64(p.parse()?))),
+        ("s64.const", |p| Ok(S64(p.parse()?))),
+        ("f32.const", |p| Ok(Float32(p.parse()?))),
+        ("f64.const", |p| Ok(Float64(p.parse()?))),
+        ("char.const", |p| {
+            let s = p.parse::<&str>()?;
+            let mut ch = s.chars();
+            let ret = match ch.next() {
+                Some(c) => c,
+                None => return Err(p.error("empty string")),
+            };
+            if ch.next().is_some() {
+                return Err(p.error("more than one character"));
+            }
+            Ok(Char(ret))
+        }),
+        ("str.const", |p| Ok(String(p.parse()?))),
+        ("list.const", |p| {
+            let mut ret = Vec::new();
+            while !p.is_empty() {
+                ret.push(p.parens(|p| p.parse())?);
+            }
+            Ok(List(ret))
+        }),
+        ("record.const", |p| {
+            let mut ret = Vec::new();
+            while !p.is_empty() {
+                ret.push(p.parens(|p| {
+                    p.parse::<kw::field>()?;
+                    Ok((p.parse()?, p.parse()?))
+                })?);
+            }
+            Ok(Record(ret))
+        }),
+        ("tuple.const", |p| {
+            let mut ret = Vec::new();
+            while !p.is_empty() {
+                ret.push(p.parens(|p| p.parse())?);
+            }
+            Ok(Tuple(ret))
+        }),
+        ("variant.const", |p| {
+            let name = p.parse()?;
+            let payload = if p.is_empty() {
+                None
+            } else {
+                Some(Box::new(p.parens(|p| p.parse())?))
+            };
+            Ok(Variant(name, payload))
+        }),
+        ("enum.const", |p| Ok(Enum(p.parse()?))),
+        ("union.const", |p| {
+            let num = p.parse()?;
+            let payload = Box::new(p.parens(|p| p.parse())?);
+            Ok(Union(num, payload))
+        }),
+        ("option.none", |_| Ok(Option(None))),
+        ("option.some", |p| {
+            Ok(Option(Some(Box::new(p.parens(|p| p.parse())?))))
+        }),
+        ("result.ok", |p| {
+            Ok(Result(Ok(if p.is_empty() {
+                None
+            } else {
+                Some(Box::new(p.parens(|p| p.parse())?))
+            })))
+        }),
+        ("result.err", |p| {
+            Ok(Result(Err(if p.is_empty() {
+                None
+            } else {
+                Some(Box::new(p.parens(|p| p.parse())?))
+            })))
+        }),
+        ("flags.const", |p| {
+            let mut ret = Vec::new();
+            while !p.is_empty() {
+                ret.push(p.parse()?);
+            }
+            Ok(Flags(ret))
+        }),
+    ]
+};
+
+impl<'a> Parse<'a> for WastVal<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        parser.depth_check()?;
+        let parse = parser.step(|c| {
+            if let Some((kw, rest)) = c.keyword() {
+                if let Some(i) = CASES.iter().position(|(name, _)| *name == kw) {
+                    return Ok((CASES[i].1, rest));
+                }
+            }
+            Err(c.error("expected a [type].const expression"))
+        })?;
+        parse(parser)
+    }
+}
+
+impl Peek for WastVal<'_> {
+    fn peek(cursor: Cursor<'_>) -> bool {
+        let kw = match cursor.keyword() {
+            Some((kw, _)) => kw,
+            None => return false,
+        };
+        CASES.iter().any(|(name, _)| *name == kw)
+    }
+
+    fn display() -> &'static str {
+        "core wasm argument"
+    }
+}