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Refactor function return type representation (#6463)

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This separates the return type from the return pattern, and replaces the
return pattern with a block of return patterns. This is a step toward
support for `ref` returns (where there's no corresponding return
pattern) and compund-form returns (where there may be multiple return
patterns).
This commit is contained in:
Geoff Romer
2025-12-10 18:34:23 +00:00
committed by GitHub
parent 77918d023b
commit bf45b1cbf5
57 changed files with 1668 additions and 1532 deletions
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toolchain/check/cpp/import.cpp
+48 -32
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@@ -1220,6 +1220,9 @@ static auto MapTagType(Context& context, const clang::TagType& type)
SemIR::TypeInstId record_type_inst_id =
context.types().GetAsTypeInstId(tag_inst_id);
return {
// TODO: inst_id's location should be the location of the usage, not
// the location of the type definition. Possibly we should synthesize a
// NameRef inst, to match how this would work in Carbon code.
.inst_id = record_type_inst_id,
.type_id = context.types().GetTypeIdForTypeInstId(record_type_inst_id)};
}
@@ -1559,19 +1562,28 @@ static auto GetReturnTypeExpr(Context& context, SemIR::LocId loc_id,
.type_id = context.types().GetTypeIdForTypeInstId(record_type_inst_id)};
}
// Returns the return pattern of the given function declaration. In case of an
// unsupported return type, it produces a diagnostic and returns
// `SemIR::ErrorInst::InstId`. Constructors are treated as returning a class
// instance.
static auto GetReturnPattern(Context& context, SemIR::LocId loc_id,
clang::FunctionDecl* clang_decl) -> SemIR::InstId {
// Information about a function's declared return type, corresponding to the
// fields of SemIR::Function with the same names.
struct ReturnInfo {
SemIR::TypeInstId return_type_inst_id;
SemIR::InstBlockId return_patterns_id;
};
// Returns information about the declared return type of the given function
// declaration. In case of an unsupported return type, it produces a diagnostic,
// and the returned return_type_inst_id will be `SemIR::ErrorInst::InstId`.
// Constructors are treated as returning a class instance.
static auto GetReturnInfo(Context& context, SemIR::LocId loc_id,
clang::FunctionDecl* clang_decl) -> ReturnInfo {
auto [type_inst_id, type_id] = GetReturnTypeExpr(context, loc_id, clang_decl);
if (!type_inst_id.has_value()) {
// void.
return SemIR::InstId::None;
return {.return_type_inst_id = type_inst_id,
.return_patterns_id = SemIR::InstBlockId::None};
}
if (type_inst_id == SemIR::ErrorInst::TypeInstId) {
return SemIR::ErrorInst::InstId;
return {.return_type_inst_id = type_inst_id,
.return_patterns_id = SemIR::InstBlockId::None};
}
auto pattern_type_id = GetPatternType(context, type_id);
clang::SourceLocation return_type_loc =
@@ -1597,33 +1609,34 @@ static auto GetReturnPattern(Context& context, SemIR::LocId loc_id,
SemIR::OutParamPattern({.type_id = pattern_type_id,
.subpattern_id = return_slot_pattern_id,
.index = SemIR::CallParamIndex::None})));
return param_pattern_id;
auto return_patterns_id = context.inst_blocks().Add({param_pattern_id});
return {.return_type_inst_id = type_inst_id,
.return_patterns_id = return_patterns_id};
}
namespace {
// Represents the parameter patterns block id, the return slot pattern id and
// the call parameters block id for a function declaration.
struct FunctionParamsInsts {
// Represents the insts and inst blocks associated with the parameters and
// returns of a function declaration, corresponding to the fields of
// SemIR::Function with the same names.
struct FunctionSignatureInsts {
SemIR::InstBlockId implicit_param_patterns_id;
SemIR::InstBlockId param_patterns_id;
SemIR::InstId return_slot_pattern_id;
SemIR::TypeInstId return_type_inst_id;
SemIR::InstBlockId return_patterns_id;
SemIR::InstBlockId call_params_id;
};
} // namespace
// Creates a block containing the parameter pattern instructions for the
// explicit parameters, a parameter pattern instruction for the return type and
// a block containing the call parameters of the function. Emits a callee
// pattern-match for the explicit parameter patterns and the return slot pattern
// to create the Call parameters instructions block. Currently the implicit
// parameter patterns are not taken into account. Returns the parameter patterns
// block id, the return slot pattern id, and the call parameters block id.
// Produces a diagnostic and returns `std::nullopt` if the function declaration
// has an unsupported parameter type.
static auto CreateFunctionParamsInsts(Context& context, SemIR::LocId loc_id,
clang::FunctionDecl* clang_decl,
int num_params)
-> std::optional<FunctionParamsInsts> {
// Creates the insts and inst blocks that represent the parameters and returns
// of the given C++ function's Carbon counterpart, including emitting a callee
// pattern match to create the `Call` parameters, and returns a
// FunctionSignatureInsts containing the results. Produces a diagnostic and
// returns `std::nullopt` if the function declaration has an unsupported
// parameter type.
static auto CreateFunctionSignatureInsts(Context& context, SemIR::LocId loc_id,
clang::FunctionDecl* clang_decl,
int num_params)
-> std::optional<FunctionSignatureInsts> {
auto implicit_param_patterns_id =
MakeImplicitParamPatternsBlockId(context, loc_id, *clang_decl);
if (!implicit_param_patterns_id.has_value()) {
@@ -1634,18 +1647,20 @@ static auto CreateFunctionParamsInsts(Context& context, SemIR::LocId loc_id,
if (!param_patterns_id.has_value()) {
return std::nullopt;
}
auto return_slot_pattern_id = GetReturnPattern(context, loc_id, clang_decl);
if (SemIR::ErrorInst::InstId == return_slot_pattern_id) {
auto [return_type_inst_id, return_patterns_id] =
GetReturnInfo(context, loc_id, clang_decl);
if (return_type_inst_id == SemIR::ErrorInst::TypeInstId) {
return std::nullopt;
}
auto call_params_id =
CalleePatternMatch(context, implicit_param_patterns_id, param_patterns_id,
return_slot_pattern_id);
return_patterns_id);
return {{.implicit_param_patterns_id = implicit_param_patterns_id,
.param_patterns_id = param_patterns_id,
.return_slot_pattern_id = return_slot_pattern_id,
.return_type_inst_id = return_type_inst_id,
.return_patterns_id = return_patterns_id,
.call_params_id = call_params_id}};
}
@@ -1689,7 +1704,7 @@ static auto ImportFunction(Context& context, SemIR::LocId loc_id,
context.pattern_block_stack().Push();
auto function_params_insts =
CreateFunctionParamsInsts(context, loc_id, clang_decl, num_params);
CreateFunctionSignatureInsts(context, loc_id, clang_decl, num_params);
auto pattern_block_id = context.pattern_block_stack().Pop();
auto decl_block_id = context.inst_block_stack().Pop();
@@ -1735,7 +1750,8 @@ static auto ImportFunction(Context& context, SemIR::LocId loc_id,
.first_owning_decl_id = decl_id,
.definition_id = SemIR::InstId::None},
{.call_params_id = function_params_insts->call_params_id,
.return_slot_pattern_id = function_params_insts->return_slot_pattern_id,
.return_type_inst_id = function_params_insts->return_type_inst_id,
.return_patterns_id = function_params_insts->return_patterns_id,
.virtual_modifier = virtual_modifier,
.virtual_index = virtual_index,
.self_param_id = FindSelfPattern(