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Clean up helpers for GetOrAddImpl (Refactor Impl construction 5/7 and 6/7) (#6469)

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Make the `AssignImplIdInWitness` into a `static` helper function since
it's only used inside `GetOrAddImpl`. Restructure the diagnostic for
unused generic bindings to move more logic into the helper, and out of
`GetOrAddImpl` so that it has more clear steps.

This is part of #6420 which is being split up into a chain of smaller
PRs. It is based on #6468.
This commit is contained in:
Dana Jansens
2025-12-11 22:22:43 +00:00
committed by GitHub
parent c0b335b87f
commit 463ba0e1db
2 changed files with 69 additions and 76 deletions
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toolchain/check/impl.cpp
+69 -72
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@@ -262,22 +262,6 @@ auto FillImplWitnessWithErrors(Context& context, SemIR::Impl& impl) -> void {
impl.witness_id = SemIR::ErrorInst::InstId;
}
auto AssignImplIdInWitness(Context& context, SemIR::ImplId impl_id,
SemIR::InstId witness_id) -> void {
if (witness_id == SemIR::ErrorInst::InstId) {
return;
}
auto witness = context.insts().GetAs<SemIR::ImplWitness>(witness_id);
auto witness_table =
context.insts().GetAs<SemIR::ImplWitnessTable>(witness.witness_table_id);
witness_table.impl_id = impl_id;
// Note: The `ImplWitnessTable` instruction is `Unique`, so while this marks
// the instruction as being a dependent instruction of a generic impl, it will
// not be substituted into the eval block.
ReplaceInstBeforeConstantUse(context, witness.witness_table_id,
witness_table);
}
auto IsImplEffectivelyFinal(Context& context, const SemIR::Impl& impl) -> bool {
return impl.is_final ||
(context.constant_values().Get(impl.self_id).is_concrete() &&
@@ -379,6 +363,65 @@ static auto IsValidImplRedecl(Context& context, SemIR::Impl& new_impl,
return true;
}
// Sets the `ImplId` in the `ImplWitnessTable`.
static auto AssignImplIdInWitness(Context& context, SemIR::ImplId impl_id,
SemIR::InstId witness_id) -> void {
if (witness_id == SemIR::ErrorInst::InstId) {
return;
}
auto witness = context.insts().GetAs<SemIR::ImplWitness>(witness_id);
auto witness_table =
context.insts().GetAs<SemIR::ImplWitnessTable>(witness.witness_table_id);
witness_table.impl_id = impl_id;
// Note: The `ImplWitnessTable` instruction is `Unique`, so while this marks
// the instruction as being a dependent instruction of a generic impl, it will
// not be substituted into the eval block.
ReplaceInstBeforeConstantUse(context, witness.witness_table_id,
witness_table);
}
// Looks for any unused generic bindings. If one is found, it is diagnosed and
// false is returned.
static auto VerifyAllGenericBindingsUsed(Context& context, SemIR::LocId loc_id,
SemIR::LocId implicit_params_loc_id,
SemIR::Impl& impl) -> bool {
if (impl.witness_id == SemIR::ErrorInst::InstId) {
return true;
}
if (!impl.generic_id.has_value()) {
return true;
}
if (impl.implicit_param_patterns_id.has_value()) {
for (auto inst_id :
context.inst_blocks().Get(impl.implicit_param_patterns_id)) {
if (inst_id == SemIR::ErrorInst::InstId) {
// An error was already diagnosed for a generic binding.
return true;
}
}
}
auto deduced_specific_id = DeduceImplArguments(
context, loc_id, impl, context.constant_values().Get(impl.self_id),
impl.interface.specific_id);
if (deduced_specific_id.has_value()) {
// Deduction succeeded, all bindings were used.
return true;
}
CARBON_DIAGNOSTIC(ImplUnusedBinding, Error,
"`impl` with unused generic binding");
// TODO: This location may be incorrect, the binding may be inherited
// from an outer declaration. It would be nice to get the particular
// binding that was undeducible back from DeduceImplArguments here and
// use that.
auto diag_loc_id =
implicit_params_loc_id.has_value() ? implicit_params_loc_id : loc_id;
context.emitter().Emit(diag_loc_id, ImplUnusedBinding);
return false;
}
// Apply an `extend impl` declaration by extending the parent scope with the
// `impl`. If there's an error it is diagnosed and false is returned.
static auto ApplyExtendImplAs(Context& context, SemIR::LocId loc_id,
@@ -443,38 +486,6 @@ static auto ApplyExtendImplAs(Context& context, SemIR::LocId loc_id,
return true;
}
// Diagnoses when an impl has an unused binding.
static auto DiagnoseUnusedGenericBinding(Context& context, SemIR::LocId loc_id,
SemIR::LocId implicit_params_loc_id,
SemIR::ImplId impl_id) -> void {
auto& impl = context.impls().Get(impl_id);
if (!impl.generic_id.has_value() ||
impl.witness_id == SemIR::ErrorInst::InstId) {
return;
}
auto deduced_specific_id = DeduceImplArguments(
context, loc_id, impl, context.constant_values().Get(impl.self_id),
impl.interface.specific_id);
if (deduced_specific_id.has_value()) {
// Deduction succeeded, all bindings were used.
return;
}
CARBON_DIAGNOSTIC(ImplUnusedBinding, Error,
"`impl` with unused generic binding");
// TODO: This location may be incorrect, the binding may be inherited
// from an outer declaration. It would be nice to get the particular
// binding that was undeducible back from DeduceImplArguments here and
// use that.
auto diag_loc_id =
implicit_params_loc_id.has_value() ? implicit_params_loc_id : loc_id;
context.emitter().Emit(diag_loc_id, ImplUnusedBinding);
// Don't try to match the impl at all, save us work and possible future
// diagnostics.
FillImplWitnessWithErrors(context, context.impls().Get(impl_id));
}
auto GetOrAddImpl(Context& context, SemIR::LocId loc_id,
SemIR::LocId implicit_params_loc_id, SemIR::Impl impl,
bool is_definition, Parse::NodeId extend_node)
@@ -535,37 +546,23 @@ auto GetOrAddImpl(Context& context, SemIR::LocId loc_id,
// in order to make and see any changes to the `Impl`.
impl_id = context.impls().Add(impl);
lookup_bucket_ref.push_back(impl_id);
AssignImplIdInWitness(context, impl_id, impl.witness_id);
auto& stored_impl_info = context.impls().Get(impl_id);
auto& stored_impl = context.impls().Get(impl_id);
// Looking to see if there are any generic bindings on the `impl`
// declaration that are not deducible. If so, and the `impl` does not
// actually use all its generic bindings, and will never be matched. This
// should be diagnossed to the user.
bool has_error_in_implicit_pattern = false;
if (impl.implicit_param_patterns_id.has_value()) {
for (auto inst_id :
context.inst_blocks().Get(impl.implicit_param_patterns_id)) {
if (inst_id == SemIR::ErrorInst::InstId) {
has_error_in_implicit_pattern = true;
break;
}
}
// Look to see if there are any generic bindings on the `impl` declaration
// that are not deducible. If so, and the `impl` does not actually use all its
// generic bindings, and will never be matched. This should be diagnosed to
// the user.
if (!VerifyAllGenericBindingsUsed(context, loc_id, implicit_params_loc_id,
stored_impl)) {
FillImplWitnessWithErrors(context, stored_impl);
}
if (!has_error_in_implicit_pattern) {
DiagnoseUnusedGenericBinding(context, loc_id, implicit_params_loc_id,
impl_id);
}
// For an `extend impl` declaration, mark the impl as extending this `impl`.
if (extend_node.has_value()) {
if (!ApplyExtendImplAs(context, loc_id, stored_impl_info, extend_node,
if (!ApplyExtendImplAs(context, loc_id, stored_impl, extend_node,
implicit_params_loc_id)) {
// Don't allow the invalid impl to be used.
FillImplWitnessWithErrors(context, stored_impl_info);
FillImplWitnessWithErrors(context, stored_impl);
}
}