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Syntactic impl declaration matching updates (#4762)

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* Implement ignoring the difference between `Self as` and `as`, as well
as `where` clauses at the end of an `impl` declaration when checking
whether `impl` declarations match, from #3763.
* Allow impl declarations with different constraint ids to match, as
long as the facet type of the constraint has the same interface_id and
specific_id.
* Add some TODOs reflecting future facet type resolution.

---------

Co-authored-by: Josh L <josh11b@users.noreply.github.com>
This commit is contained in:
josh11b
2025-01-07 23:31:31 +00:00
committed by GitHub
co-authored by Josh L
parent 8cac0c398a
commit 1d379ff7f8
6 changed files with 320 additions and 21 deletions
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toolchain/check/handle_impl.cpp
+36 -7
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@@ -212,21 +212,45 @@ static auto PopImplIntroducerAndParamsAsNameComponent(
Parse::NodeId first_param_node_id =
context.node_stack().PopForSoloNodeId<Parse::NodeKind::ImplIntroducer>();
// Subtracting 1 since we don't want to include the final `{` or `;` of the
// declaration when performing syntactic match.
// TODO: Following proposal #3763, we should exclude any `where` clause, and
// add `Self` before `as` if needed, see:
auto end_node_kind = context.parse_tree().node_kind(end_of_decl_node_id);
CARBON_CHECK(end_node_kind == Parse::NodeKind::ImplDefinitionStart ||
end_node_kind == Parse::NodeKind::ImplDecl);
Parse::Tree::PostorderIterator last_param_iter(end_of_decl_node_id);
--last_param_iter;
// Following proposal #3763, exclude a final `where` clause, if present. See:
// https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p3763.md#redeclarations
auto node_kind = context.parse_tree().node_kind(end_of_decl_node_id);
CARBON_CHECK(node_kind == Parse::NodeKind::ImplDefinitionStart ||
node_kind == Parse::NodeKind::ImplDecl);
Parse::NodeId last_param_node_id(end_of_decl_node_id.index - 1);
// Caches the NodeKind for the current value of *last_param_iter so
if (context.parse_tree().node_kind(*last_param_iter) ==
Parse::NodeKind::WhereExpr) {
int where_operands_to_skip = 1;
--last_param_iter;
CARBON_CHECK(Parse::Tree::PostorderIterator(first_param_node_id) <
last_param_iter);
do {
auto node_kind = context.parse_tree().node_kind(*last_param_iter);
if (node_kind == Parse::NodeKind::WhereExpr) {
// If we have a nested `where`, we need to see another `WhereOperand`
// before we find the one that matches our original `WhereExpr` node.
++where_operands_to_skip;
} else if (node_kind == Parse::NodeKind::WhereOperand) {
--where_operands_to_skip;
}
--last_param_iter;
CARBON_CHECK(Parse::Tree::PostorderIterator(first_param_node_id) <
last_param_iter);
} while (where_operands_to_skip > 0);
}
return {
.name_loc_id = Parse::NodeId::Invalid,
.name_id = SemIR::NameId::Invalid,
.first_param_node_id = first_param_node_id,
.last_param_node_id = last_param_node_id,
.last_param_node_id = *last_param_iter,
.implicit_params_loc_id = implicit_params_loc_id,
.implicit_param_patterns_id =
implicit_param_patterns_id.value_or(SemIR::InstBlockId::Invalid),
@@ -297,6 +321,11 @@ static auto BuildImplDecl(Context& context, Parse::AnyImplDeclId node_id,
// TODO: Check that its constant value is a constraint.
auto [constraint_inst_id, constraint_type_id] =
ExprAsType(context, constraint_node, constraint_id);
// TODO: Do facet type resolution here.
// TODO: Determine `interface_id` and `specific_id` once and save it in the
// resolved facet type, instead of in multiple functions called below.
// TODO: Skip work below if facet type resolution fails, so we don't have a
// valid/non-error `interface_id` at all.
// Process modifiers.
// TODO: Should we somehow permit access specifiers on `impl`s?