capnproto

resolver.h (6031B)

---

 // Copyright (c) 2013-2020 Sandstorm Development Group, Inc. and contributors
 // Licensed under the MIT License:
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
 #pragma once
 
 #include <capnp/compiler/grammar.capnp.h>
 #include <capnp/schema.capnp.h>
 #include <capnp/schema.h>
 #include <kj/one-of.h>
 
 CAPNP_BEGIN_HEADER
 
 namespace capnp {
 namespace compiler {
 
 class Resolver {
   // Callback class used to find other nodes relative to some existing node.
   //
   // `Resolver` is used when compiling one declaration requires inspecting the compiled versions
   // of other declarations it depends on. For example, if struct type Foo contains a field of type
   // Bar, and specifies a default value for that field, then to parse that default value we need
   // the compiled version of `Bar`. Or, more commonly, if a struct type Foo refers to some other
   // type `Bar.Baz`, this requires doing a lookup that depends on at least partial compilation of
   // `Bar`, in order to discover its nested type `Baz`.
   //
   // Note that declarations are often compiled just-in-time the first time they are resolved. So,
   // the methods of Resolver may recurse back into other parts of the compiler. It must detect when
   // a dependency cycle occurs and report an error in order to prevent an infinite loop.
 
 public:
   struct ResolvedDecl {
     // Information about a resolved declaration.
 
     uint64_t id;
     // Type ID / node ID of the resolved declaration.
 
     uint genericParamCount;
     // If non-zero, the declaration is a generic with the given number of parameters.
 
     uint64_t scopeId;
     // The ID of the parent scope of this declaration.
 
     Declaration::Which kind;
     // What basic kind of declaration is this? E.g. struct, interface, const, etc.
 
     Resolver* resolver;
     // `Resolver` instance that can be used to further resolve other declarations relative to this
     // one.
 
     kj::Maybe<schema::Brand::Reader> brand;
     // If present, then it is necessary to replace the brand scope with the given brand before
     // using the target type. This happens when the decl resolved to an alias; all other fields
     // of `ResolvedDecl` refer to the target of the alias, except for `scopeId` which is the
     // scope that contained the alias.
   };
 
   struct ResolvedParameter {
     uint64_t id;  // ID of the node declaring the parameter.
     uint index;   // Index of the parameter.
   };
 
   typedef kj::OneOf<ResolvedDecl, ResolvedParameter> ResolveResult;
 
   virtual kj::Maybe<ResolveResult> resolve(kj::StringPtr name) = 0;
   // Look up the given name, relative to this node, and return basic information about the
   // target.
 
   virtual kj::Maybe<ResolveResult> resolveMember(kj::StringPtr name) = 0;
   // Look up a member of this node.
 
   virtual ResolvedDecl resolveBuiltin(Declaration::Which which) = 0;
   virtual ResolvedDecl resolveId(uint64_t id) = 0;
 
   virtual kj::Maybe<ResolvedDecl> getParent() = 0;
   // Returns the parent of this scope, or null if this is the top scope.
 
   virtual ResolvedDecl getTopScope() = 0;
   // Get the top-level scope containing this node.
 
   virtual kj::Maybe<Schema> resolveBootstrapSchema(uint64_t id, schema::Brand::Reader brand) = 0;
   // Get the schema for the given ID.  If a schema is returned, it must be safe to traverse its
   // dependencies via the Schema API.  A schema that is only at the bootstrap stage is
   // acceptable.
   //
   // Throws an exception if the id is not one that was found by calling resolve() or by
   // traversing other schemas.  Returns null if the ID is recognized, but the corresponding
   // schema node failed to be built for reasons that were already reported.
 
   virtual kj::Maybe<schema::Node::Reader> resolveFinalSchema(uint64_t id) = 0;
   // Get the final schema for the given ID.  A bootstrap schema is not acceptable.  A raw
   // node reader is returned rather than a Schema object because using a Schema object built
   // by the final schema loader could trigger lazy initialization of dependencies which could
   // lead to a cycle and deadlock.
   //
   // Throws an exception if the id is not one that was found by calling resolve() or by
   // traversing other schemas.  Returns null if the ID is recognized, but the corresponding
   // schema node failed to be built for reasons that were already reported.
 
   virtual kj::Maybe<ResolvedDecl> resolveImport(kj::StringPtr name) = 0;
   // Get the ID of an imported file given the import path.
 
   virtual kj::Maybe<kj::Array<const byte>> readEmbed(kj::StringPtr name) = 0;
   // Read and return the contents of a file for an `embed` expression.
 
   virtual kj::Maybe<Type> resolveBootstrapType(schema::Type::Reader type, Schema scope) = 0;
   // Compile a schema::Type into a Type whose dependencies may safely be traversed via the schema
   // API. These dependencies may have only bootstrap schemas. Returns null if the type could not
   // be constructed due to already-reported errors.
 };
 
 }  // namespace compiler
 }  // namespace capnp
 
 CAPNP_END_HEADER