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Basic support for .Self within :! bindings and where expressions. (#1311)

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`.Self` is modeled as a new kind of expression, `DotSelfExpression`. Name resolution associates each occurrence of a `DotSelfExpression` with a generic binding, much like for an `IdentifierExpression`.

Both `:!` bindings and `where` expressions bring `.Self` into scope. The tentative intent is that if there are multiple `.Self`s in scope and they refer to different bindings, the result of using a `.Self` expression is an ambiguity error, but that is not implemented in this patch. Instead, like for `IdentifierExpression`s, we find the innermost enclosing definition of `.Self`.

`.Foo` expressions are rewritten to `.Self.Foo`, but this isn't enough to make them do anything useful, because associated constants aren't supported in general yet.
This commit is contained in:
Richard Smith
2022-06-14 21:49:01 -07:00
committed by GitHub
parent b83f5c3fc7
commit 2fef76e58c
26 changed files with 418 additions and 67 deletions
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explorer/interpreter/resolve_names.cpp
+22 -9
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@@ -166,6 +166,15 @@ static auto ResolveNames(Expression& expression,
identifier.set_value_node(value_node);
break;
}
case ExpressionKind::DotSelfExpression: {
auto& dot_self = cast<DotSelfExpression>(expression);
CARBON_ASSIGN_OR_RETURN(
const auto value_node,
enclosing_scope.Resolve(".Self", dot_self.source_loc()));
dot_self.set_self_binding(const_cast<GenericBinding*>(
&cast<GenericBinding>(value_node.base())));
break;
}
case ExpressionKind::IntrinsicExpression:
CARBON_RETURN_IF_ERROR(ResolveNames(
cast<IntrinsicExpression>(expression).args(), enclosing_scope));
@@ -182,13 +191,14 @@ static auto ResolveNames(Expression& expression,
}
case ExpressionKind::WhereExpression: {
auto& where = cast<WhereExpression>(expression);
// TODO: Introduce `.Self` into scope?
// StaticScope where_scope;
// where_scope.AddParent(&enclosing_scope);
// where_scope.Add(".Self", ???);
CARBON_RETURN_IF_ERROR(ResolveNames(where.base(), enclosing_scope));
CARBON_RETURN_IF_ERROR(
ResolveNames(where.self_binding().type(), enclosing_scope));
// Introduce `.Self` into scope on the right of the `where` keyword.
StaticScope where_scope;
where_scope.AddParent(&enclosing_scope);
CARBON_RETURN_IF_ERROR(where_scope.Add(".Self", &where.self_binding()));
for (Nonnull<WhereClause*> clause : where.clauses()) {
CARBON_RETURN_IF_ERROR(ResolveNames(*clause, enclosing_scope));
CARBON_RETURN_IF_ERROR(ResolveNames(*clause, where_scope));
}
break;
}
@@ -253,7 +263,11 @@ static auto ResolveNames(Pattern& pattern, StaticScope& enclosing_scope)
}
case PatternKind::GenericBinding: {
auto& binding = cast<GenericBinding>(pattern);
CARBON_RETURN_IF_ERROR(ResolveNames(binding.type(), enclosing_scope));
// `.Self` is in scope in the context of the type.
StaticScope self_scope;
self_scope.AddParent(&enclosing_scope);
CARBON_RETURN_IF_ERROR(self_scope.Add(".Self", &binding));
CARBON_RETURN_IF_ERROR(ResolveNames(binding.type(), self_scope));
if (binding.name() != AnonymousName) {
CARBON_RETURN_IF_ERROR(enclosing_scope.Add(binding.name(), &binding));
}
@@ -425,8 +439,7 @@ static auto ResolveNames(Declaration& declaration, StaticScope& enclosing_scope)
StaticScope function_scope;
function_scope.AddParent(&enclosing_scope);
for (Nonnull<GenericBinding*> binding : function.deduced_parameters()) {
CARBON_RETURN_IF_ERROR(ResolveNames(binding->type(), function_scope));
CARBON_RETURN_IF_ERROR(function_scope.Add(binding->name(), binding));
CARBON_RETURN_IF_ERROR(ResolveNames(*binding, function_scope));
}
if (function.is_method()) {
CARBON_RETURN_IF_ERROR(