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Don't treat dependent types as having a copy value representation. (#6055)

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Add `Dependent` value and initializing representations for types whose
representations are unknown because they are dependent. When generating
SemIR in such cases, use a worst-case initializing representation that
both provides a destination address and also propagates a potential
result value.

Use this to fix incorrect lowering and lowering crashes for specific
functions involving generic types that don't use a copy value
representation.

In lowering, be careful to distinguish between whether the initializing
representation for the generic return type uses a return slot (which
affects whether the SemIR declaration and call have one) and whether the
initializing representation for the specific return type uses a return
slot (which affects whether the LLVM IR declaration and call have one).
This commit is contained in:
Richard Smith
2025-09-15 23:59:00 +00:00
committed by GitHub
parent ca40e9d693
commit b44ba47cf3
53 changed files with 1375 additions and 670 deletions
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toolchain/lower/handle_aggregates.cpp
+10 -1
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@@ -79,6 +79,8 @@ static auto GetAggregateElement(FunctionContext& context,
switch (value_repr.repr.kind) {
case SemIR::ValueRepr::Unknown:
CARBON_FATAL("Lowering access to incomplete aggregate type");
case SemIR::ValueRepr::Dependent:
CARBON_FATAL("Lowering access to dependent aggregate type");
case SemIR::ValueRepr::None:
return aggr_value;
case SemIR::ValueRepr::Copy:
@@ -207,6 +209,10 @@ static auto EmitAggregateInitializer(FunctionContext& context,
case SemIR::InitRepr::Incomplete:
CARBON_FATAL("Lowering aggregate initialization of incomplete type {0}",
type.file->types().GetAsInst(type.type_id));
case SemIR::InitRepr::Dependent:
CARBON_FATAL("Lowering aggregate initialization of dependent type {0}",
type.file->types().GetAsInst(type.type_id));
}
}
@@ -241,7 +247,10 @@ static auto EmitAggregateValueRepr(FunctionContext& context,
auto value_type = value_repr.type();
switch (value_repr.repr.kind) {
case SemIR::ValueRepr::Unknown:
CARBON_FATAL("Incomplete aggregate type in lowering");
CARBON_FATAL("Lowering value of incomplete aggregate type");
case SemIR::ValueRepr::Dependent:
CARBON_FATAL("Lowering value of dependent aggregate type");
case SemIR::ValueRepr::None:
// TODO: Add a helper to get a "no value representation" value.