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Stop special-casing empty structs. (#2849)

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This removes special-casing of empty structs, handling them as just a regular value instead of a builtin. Note the `{} as Type` is still special-cased.

In lowering, removes the test of calling a function using `{}` because it's missing the proper load/store. This setup notices that error whereas the prior worked due to said special-casing. Fixing this will need to be done as part of generally adding loads for variable uses.
This commit is contained in:
Jon Ross-Perkins
2023-05-26 10:33:17 -07:00
committed by GitHub
parent 1d56e165ef
commit 76151d1fff
13 changed files with 99 additions and 84 deletions
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toolchain/semantics/semantics_context.cpp
+10 -5
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@@ -251,10 +251,12 @@ auto SemanticsContext::ImplicitAsImpl(SemanticsNodeId value_id,
// If the value is invalid, we can't do much, but do "succeed".
return ImplicitAsKind::Identical;
}
auto value_type_id = semantics_->GetNode(value_id).type_id();
auto value = semantics_->GetNode(value_id);
auto value_type_id = value.type_id();
if (value_type_id == SemanticsNodeId::BuiltinInvalidType) {
return ImplicitAsKind::Identical;
}
if (as_type_id == SemanticsNodeId::BuiltinInvalidType) {
// Although the target type is invalid, this still changes the value.
if (output_value_id != nullptr) {
@@ -268,18 +270,21 @@ auto SemanticsContext::ImplicitAsImpl(SemanticsNodeId value_id,
return ImplicitAsKind::Identical;
}
// When converting to a Type, there are some automatic conversions that can be
// done.
if (as_type_id == SemanticsNodeId::BuiltinTypeType) {
// When converting `()` to a type, the result is `() as Type`.
// TODO: This might switch to be closer to the struct conversion below.
if (value_id == SemanticsNodeId::BuiltinEmptyTuple) {
if (output_value_id != nullptr) {
*output_value_id = SemanticsNodeId::BuiltinEmptyTupleType;
}
return ImplicitAsKind::Compatible;
}
if (value_id == SemanticsNodeId::BuiltinEmptyStruct) {
// When converting `{}` to a type, the result is `{} as Type`.
if (value.kind() == SemanticsNodeKind::StructValue &&
value.GetAsStructValue() == SemanticsNodeBlockId::Empty) {
if (output_value_id != nullptr) {
*output_value_id = SemanticsNodeId::BuiltinEmptyStructType;
*output_value_id = value_type_id;
}
return ImplicitAsKind::Compatible;
}