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Propagate errors out of Substitute. (#2694)

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This is in preparation for template instantiation being triggered during substitution, and being able to fail.

Fix rule-of-three violation (missing assignment operator) in `Error` that got in the way of using it to hold an error temporarily in a failed transformation.
This commit is contained in:
Richard Smith
2023-03-20 13:15:11 -07:00
committed by GitHub
parent 28946d4b87
commit f50ca72797
5 changed files with 496 additions and 276 deletions
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explorer/interpreter/impl_scope.cpp
+34 -20
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@@ -121,8 +121,9 @@ auto ImplScope::TryResolve(Nonnull<const Value*> constraint_type,
bool diagnose_missing_impl) const
-> ErrorOr<std::optional<Nonnull<const Witness*>>> {
if (const auto* iface_type = dyn_cast<InterfaceType>(constraint_type)) {
iface_type =
cast<InterfaceType>(type_checker.Substitute(bindings, iface_type));
CARBON_ASSIGN_OR_RETURN(
iface_type,
type_checker.SubstituteCast<InterfaceType>(bindings, iface_type));
return TryResolveInterface(iface_type, impl_type, source_loc, type_checker,
diagnose_missing_impl);
}
@@ -144,13 +145,17 @@ auto ImplScope::TryResolve(Nonnull<const Value*> constraint_type,
}
Bindings local_bindings = bindings;
local_bindings.Add(constraint->self_binding(), impl_type, witness);
CARBON_ASSIGN_OR_RETURN(const auto* subst_interface,
type_checker.SubstituteCast<InterfaceType>(
local_bindings, impl.interface));
CARBON_ASSIGN_OR_RETURN(
Nonnull<const Value*> subst_type,
type_checker.Substitute(local_bindings, impl.type));
CARBON_ASSIGN_OR_RETURN(
std::optional<Nonnull<const Witness*>> result,
TryResolveInterface(
cast<InterfaceType>(
type_checker.Substitute(local_bindings, impl.interface)),
type_checker.Substitute(local_bindings, impl.type), source_loc,
type_checker, diagnose_missing_impl));
TryResolveInterface(subst_interface, subst_type, source_loc,
type_checker, diagnose_missing_impl));
if (!result) {
return {std::nullopt};
}
@@ -174,16 +179,22 @@ auto ImplScope::TryResolve(Nonnull<const Value*> constraint_type,
local_bindings.Add(constraint->self_binding(), impl_type, witness);
SingleStepEqualityContext equality_ctx(this);
for (const auto& intrinsic : intrinsics) {
CARBON_ASSIGN_OR_RETURN(
Nonnull<const Value*> type,
type_checker.Substitute(local_bindings, intrinsic.type));
IntrinsicConstraint converted = {
.type = type_checker.Substitute(local_bindings, intrinsic.type),
.kind = intrinsic.kind,
.arguments = {}};
.type = type, .kind = intrinsic.kind, .arguments = {}};
converted.arguments.reserve(intrinsic.arguments.size());
for (Nonnull<const Value*> argument : intrinsic.arguments) {
converted.arguments.push_back(
CARBON_ASSIGN_OR_RETURN(
Nonnull<const Value*> subst_arg,
type_checker.Substitute(local_bindings, argument));
converted.arguments.push_back(subst_arg);
}
if (!type_checker.IsIntrinsicConstraintSatisfied(converted, *this)) {
CARBON_ASSIGN_OR_RETURN(
bool intrinsic_satisfied,
type_checker.IsIntrinsicConstraintSatisfied(converted, *this));
if (!intrinsic_satisfied) {
if (!diagnose_missing_impl) {
return {std::nullopt};
}
@@ -193,11 +204,11 @@ auto ImplScope::TryResolve(Nonnull<const Value*> constraint_type,
}
for (const auto& equal : equals) {
auto it = equal.values.begin();
Nonnull<const Value*> first =
type_checker.Substitute(local_bindings, *it++);
CARBON_ASSIGN_OR_RETURN(Nonnull<const Value*> first,
type_checker.Substitute(local_bindings, *it++));
for (; it != equal.values.end(); ++it) {
Nonnull<const Value*> current =
type_checker.Substitute(local_bindings, *it);
CARBON_ASSIGN_OR_RETURN(Nonnull<const Value*> current,
type_checker.Substitute(local_bindings, *it));
if (!ValueEqual(first, current, &equality_ctx)) {
if (!diagnose_missing_impl) {
return {std::nullopt};
@@ -208,10 +219,13 @@ auto ImplScope::TryResolve(Nonnull<const Value*> constraint_type,
}
}
for (const auto& rewrite : rewrites) {
Nonnull<const Value*> constant =
type_checker.Substitute(local_bindings, rewrite.constant);
Nonnull<const Value*> value = type_checker.Substitute(
local_bindings, rewrite.converted_replacement);
CARBON_ASSIGN_OR_RETURN(
Nonnull<const Value*> constant,
type_checker.Substitute(local_bindings, rewrite.constant));
CARBON_ASSIGN_OR_RETURN(
Nonnull<const Value*> value,
type_checker.Substitute(local_bindings,
rewrite.converted_replacement));
if (!ValueEqual(constant, value, &equality_ctx)) {
if (!diagnose_missing_impl) {
return {std::nullopt};