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Basic support for implementing and using a parameterized interface. (#4203)

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The main change here is to form a specific when checking an interface
function against an impl function, instead of just substituting the
`Self` type.
This commit is contained in:
Richard Smith
2024-08-09 01:05:03 +00:00
committed by GitHub
parent b2a13afb73
commit 4a21b6af9b
54 changed files with 998 additions and 266 deletions
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toolchain/check/impl.cpp
+84 -29
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@@ -7,9 +7,10 @@
#include "toolchain/base/kind_switch.h"
#include "toolchain/check/context.h"
#include "toolchain/check/function.h"
#include "toolchain/check/generic.h"
#include "toolchain/check/import_ref.h"
#include "toolchain/check/subst.h"
#include "toolchain/diagnostics/diagnostic_emitter.h"
#include "toolchain/sem_ir/generic.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/impl.h"
#include "toolchain/sem_ir/inst.h"
@@ -27,13 +28,59 @@ static auto NoteAssociatedFunction(Context& context,
builder.Note(function.decl_id, ImplAssociatedFunctionHere, function.name_id);
}
// Gets the self specific of a generic declaration that is an interface member,
// given a specific for an enclosing generic, plus a type to use as `Self`.
static auto GetSelfSpecificForInterfaceMemberWithSelfType(
Context& context, SemIR::SpecificId enclosing_specific_id,
SemIR::GenericId generic_id, SemIR::TypeId self_type_id)
-> SemIR::SpecificId {
const auto& generic = context.generics().Get(generic_id);
auto bindings = context.inst_blocks().Get(generic.bindings_id);
llvm::SmallVector<SemIR::InstId> arg_ids;
arg_ids.reserve(bindings.size());
// Start with the enclosing arguments.
if (enclosing_specific_id.is_valid()) {
auto enclosing_specific_args_id =
context.specifics().Get(enclosing_specific_id).args_id;
auto enclosing_specific_args =
context.inst_blocks().Get(enclosing_specific_args_id);
arg_ids.assign(enclosing_specific_args.begin(),
enclosing_specific_args.end());
}
// Add the `Self` argument.
CARBON_CHECK(
context.entity_names()
.Get(context.insts()
.GetAs<SemIR::BindSymbolicName>(bindings[arg_ids.size()])
.entity_name_id)
.name_id == SemIR::NameId::SelfType)
<< "Expected a Self binding, found "
<< context.insts().Get(bindings[arg_ids.size()]);
arg_ids.push_back(context.types().GetInstId(self_type_id));
// Take any trailing argument values from the self specific.
// TODO: If these refer to outer arguments, for example in their types, we may
// need to perform extra substitutions here.
auto self_specific_args = context.inst_blocks().Get(
context.specifics().Get(generic.self_specific_id).args_id);
for (auto arg_id : self_specific_args.drop_front(arg_ids.size())) {
arg_ids.push_back(context.constant_values().GetConstantInstId(arg_id));
}
auto args_id = context.inst_blocks().AddCanonical(arg_ids);
return MakeSpecific(context, generic_id, args_id);
}
// Checks that `impl_function_id` is a valid implementation of the function
// described in the interface as `interface_function_id`. Returns the value to
// put into the corresponding slot in the witness table, which can be
// `BuiltinError` if the function is not usable.
static auto CheckAssociatedFunctionImplementation(
Context& context, SemIR::FunctionId interface_function_id,
SemIR::InstId impl_decl_id, Substitutions substitutions) -> SemIR::InstId {
Context& context, SemIR::FunctionType interface_function_type,
SemIR::InstId impl_decl_id, SemIR::TypeId self_type_id) -> SemIR::InstId {
auto impl_function_decl =
context.insts().TryGetAs<SemIR::FunctionDecl>(impl_decl_id);
if (!impl_function_decl) {
@@ -42,19 +89,32 @@ static auto CheckAssociatedFunctionImplementation(
SemIR::NameId);
auto builder = context.emitter().Build(
impl_decl_id, ImplFunctionWithNonFunction,
context.functions().Get(interface_function_id).name_id);
NoteAssociatedFunction(context, builder, interface_function_id);
context.functions().Get(interface_function_type.function_id).name_id);
NoteAssociatedFunction(context, builder,
interface_function_type.function_id);
builder.Emit();
return SemIR::InstId::BuiltinError;
}
// Map from the specific for the function type to the specific for the
// function signature. The function signature may have additional generic
// parameters.
auto interface_function_specific_id =
GetSelfSpecificForInterfaceMemberWithSelfType(
context, interface_function_type.specific_id,
context.functions()
.Get(interface_function_type.function_id)
.generic_id,
self_type_id);
// TODO: This should be a semantic check rather than a syntactic one. The
// functions should be allowed to have different signatures as long as we can
// synthesize a suitable thunk.
if (!CheckFunctionTypeMatches(
context, context.functions().Get(impl_function_decl->function_id),
context.functions().Get(interface_function_id), substitutions,
context.functions().Get(interface_function_type.function_id),
interface_function_specific_id,
/*check_syntax=*/false)) {
return SemIR::InstId::BuiltinError;
}
@@ -63,18 +123,17 @@ static auto CheckAssociatedFunctionImplementation(
// Builds a witness that the specified impl implements the given interface.
static auto BuildInterfaceWitness(
Context& context, const SemIR::Impl& impl,
Context& context, const SemIR::Impl& impl, SemIR::TypeId interface_type_id,
SemIR::InterfaceType interface_type,
llvm::SmallVectorImpl<SemIR::InstId>& used_decl_ids) -> SemIR::InstId {
const auto& interface = context.interfaces().Get(interface_type.interface_id);
if (!interface.is_defined()) {
CARBON_DIAGNOSTIC(ImplOfUndefinedInterface, Error,
"Implementation of undefined interface {0}.",
SemIR::NameId);
auto builder = context.emitter().Build(
impl.definition_id, ImplOfUndefinedInterface, interface.name_id);
context.NoteUndefinedInterface(interface_type.interface_id, builder);
builder.Emit();
if (!context.TryToDefineType(interface_type_id, [&] {
CARBON_DIAGNOSTIC(ImplOfUndefinedInterface, Error,
"Implementation of undefined interface {0}.",
SemIR::NameId);
return context.emitter().Build(
impl.definition_id, ImplOfUndefinedInterface, interface.name_id);
})) {
return SemIR::InstId::BuiltinError;
}
@@ -85,18 +144,11 @@ static auto BuildInterfaceWitness(
context.inst_blocks().Get(interface.associated_entities_id);
table.reserve(assoc_entities.size());
// Substitute `Self` with the impl's self type when associated functions.
// TODO: Also substitute the arguments from interface_type.specific_id.
auto self_bind =
context.insts().GetAs<SemIR::BindSymbolicName>(interface.self_param_id);
Substitution substitutions[1] = {
{.bind_id =
context.entity_names().Get(self_bind.entity_name_id).bind_index,
.replacement_id = context.types().GetConstantId(impl.self_id)}};
for (auto decl_id : assoc_entities) {
LoadImportRef(context, decl_id);
decl_id = context.constant_values().GetConstantInstId(decl_id);
decl_id =
context.constant_values().GetInstId(SemIR::GetConstantValueInSpecific(
context.sem_ir(), interface_type.specific_id, decl_id));
CARBON_CHECK(decl_id.is_valid()) << "Non-constant associated entity";
auto decl = context.insts().Get(decl_id);
CARBON_KIND_SWITCH(decl) {
@@ -115,7 +167,7 @@ static auto BuildInterfaceWitness(
if (impl_decl_id.is_valid()) {
used_decl_ids.push_back(impl_decl_id);
table.push_back(CheckAssociatedFunctionImplementation(
context, fn_type->function_id, impl_decl_id, substitutions));
context, *fn_type, impl_decl_id, impl.self_id));
} else {
CARBON_DIAGNOSTIC(
ImplMissingFunction, Error,
@@ -137,7 +189,10 @@ static auto BuildInterfaceWitness(
"impl of interface with associated constant");
return SemIR::InstId::BuiltinError;
default:
CARBON_FATAL() << "Unexpected kind of associated entity " << decl;
CARBON_CHECK(decl_id == SemIR::InstId::BuiltinError)
<< "Unexpected kind of associated entity " << decl;
table.push_back(SemIR::InstId::BuiltinError);
break;
}
}
@@ -162,8 +217,8 @@ auto BuildImplWitness(Context& context, SemIR::ImplId impl_id)
llvm::SmallVector<SemIR::InstId> used_decl_ids;
auto witness_id =
BuildInterfaceWitness(context, impl, *interface_type, used_decl_ids);
auto witness_id = BuildInterfaceWitness(context, impl, impl.constraint_id,
*interface_type, used_decl_ids);
// TODO: Diagnose if any declarations in the impl are not in used_decl_ids.