Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 1006 insertions, 0 deletions

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..c0122ef73f
--- /dev/null
+++ b/third_party/rust/wast/src/component/resolve.rs
@@ -0,0 +1,1006 @@
+use crate::component::*;
+use crate::core::{self, ValType};
+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(_) | ComponentField::Producers(_) => 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),
+                TypeBounds::SubResource => Ok(()),
+            },
+        }
+    }
+
+    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
+            }
+            CanonicalFuncKind::ResourceNew(info) => return self.resolve_ns(&mut info.ty, Ns::Type),
+            CanonicalFuncKind::ResourceRep(info) => return self.resolve_ns(&mut info.ty, Ns::Type),
+            CanonicalFuncKind::ResourceDrop(info) => {
+                return self.resolve_ns(&mut info.ty, Ns::Type)
+            }
+        };
+
+        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::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)?;
+                }
+            }
+            ComponentDefinedType::Own(t) | ComponentDefinedType::Borrow(t) => {
+                self.resolve_ns(t, Ns::Type)?;
+            }
+        }
+        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();
+            }
+            TypeDef::Resource(r) => {
+                match &mut r.rep {
+                    ValType::I32 | ValType::I64 | ValType::F32 | ValType::F64 | ValType::V128 => {}
+                    ValType::Ref(r) => match &mut r.heap {
+                        core::HeapType::Func
+                        | core::HeapType::Extern
+                        | core::HeapType::Exn
+                        | core::HeapType::Any
+                        | core::HeapType::Eq
+                        | core::HeapType::Array
+                        | core::HeapType::I31
+                        | core::HeapType::Struct
+                        | core::HeapType::None
+                        | core::HeapType::NoFunc
+                        | core::HeapType::NoExtern => {}
+                        core::HeapType::Concrete(id) => {
+                            self.resolve_ns(id, Ns::Type)?;
+                        }
+                    },
+                }
+                if let Some(dtor) = &mut r.dtor {
+                    self.core_item_ref(dtor)?;
+                }
+            }
+        }
+        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(_)
+                | CanonicalFuncKind::ResourceNew(_)
+                | CanonicalFuncKind::ResourceRep(_)
+                | CanonicalFuncKind::ResourceDrop(_) => {
+                    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(_) | ComponentField::Producers(_) => 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,
+        }
+    }
+}