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Restructure return declaration handling (#7076)

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- A function with a return declaration always has exactly one
`ReturnSlotPattern`, representing the whole return declaration (whereas
previously that was omitted for value and reference returns).
- The `ReturnSlotPattern` always has a subpattern with the same form.
`OutParamPattern` already plays that role for initializing forms, and
`TuplePattern` will play that role for tuple forms. This change
introduces `ValueReturnPattern` and `RefReturnPattern` to represent
value and reference return forms.
- As before, the `ReturnSlotPattern` has a corresponding `ReturnSlot`
that represents the output that is initialized by a `return` statement.
Its structure parallels the structure of the `ReturnSlotPattern`, so we
need `ValueReturn` and `RefReturn` insts that correspond to
`ValueReturnPattern` and `RefReturnPattern`.

This is a step toward supporting generic return forms, where the
`ReturnSlotPattern`'s subpattern may be an action: this change ensures
that evaluating the action for a specific form produces the same SemIR
as if the form were concrete to begin with. More speculatively, this
should simplify the implementation of `return` statements with compound
return forms.

---------

Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
This commit is contained in:
Geoff Romer
2026-04-22 23:38:21 +00:00
committed by GitHub
co-authored by Chandler Carruth
parent 3abc334c42
commit 49c7288619
40 changed files with 598 additions and 390 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/check/cpp/import.cpp
+12 -14
View File
@@ -1294,7 +1294,7 @@ static auto GetReturnTypeExpr(Context& context, SemIR::LocId loc_id,
struct ReturnInfo {
SemIR::TypeInstId return_type_inst_id;
SemIR::InstId return_form_inst_id;
SemIR::InstBlockId return_patterns_id;
SemIR::InstId return_pattern_id;
};
// Returns information about the declared return type of the given function
@@ -1309,12 +1309,12 @@ static auto GetReturnInfo(Context& context, SemIR::LocId loc_id,
// void.
return {.return_type_inst_id = SemIR::TypeInstId::None,
.return_form_inst_id = SemIR::InstId::None,
.return_patterns_id = SemIR::InstBlockId::None};
.return_pattern_id = SemIR::InstId::None};
}
if (form_inst_id == SemIR::ErrorInst::InstId) {
return {.return_type_inst_id = SemIR::ErrorInst::TypeInstId,
.return_form_inst_id = SemIR::ErrorInst::InstId,
.return_patterns_id = SemIR::InstBlockId::None};
.return_pattern_id = SemIR::InstId::None};
}
auto pattern_type_id = GetPatternType(context, type_id);
clang::SourceLocation return_type_loc =
@@ -1328,7 +1328,7 @@ static auto GetReturnInfo(Context& context, SemIR::LocId loc_id,
}
SemIR::ImportIRInstId return_type_import_ir_inst_id =
AddImportIRInst(context.sem_ir(), return_type_loc);
auto return_patterns_id = SemIR::InstBlockId::Empty;
auto return_pattern_id = SemIR::InstId::None;
if (auto init_form =
context.insts().TryGetAs<SemIR::InitForm>(form_inst_id)) {
auto param_pattern_id = AddInst(
@@ -1337,18 +1337,17 @@ static auto GetReturnInfo(Context& context, SemIR::LocId loc_id,
SemIR::OutParamPattern(
{.type_id = pattern_type_id,
.pretty_name_id = SemIR::NameId::ReturnSlot})));
SemIR::InstId return_slot_pattern_id =
return_pattern_id =
AddInst(context,
SemIR::LocIdAndInst::RuntimeVerified(
context.sem_ir(), return_type_import_ir_inst_id,
SemIR::ReturnSlotPattern({.type_id = pattern_type_id,
.subpattern_id = param_pattern_id,
.type_inst_id = type_inst_id})));
return_patterns_id = context.inst_blocks().Add({return_slot_pattern_id});
}
return {.return_type_inst_id = type_inst_id,
.return_form_inst_id = form_inst_id,
.return_patterns_id = return_patterns_id};
.return_pattern_id = return_pattern_id};
}
namespace {
@@ -1360,7 +1359,7 @@ struct FunctionSignatureInsts {
SemIR::InstBlockId param_patterns_id;
SemIR::TypeInstId return_type_inst_id;
SemIR::InstId return_form_inst_id;
SemIR::InstBlockId return_patterns_id;
SemIR::InstId return_pattern_id;
SemIR::InstBlockId call_param_patterns_id;
SemIR::InstBlockId call_params_id;
SemIR::Function::CallParamIndexRanges param_ranges;
@@ -1392,21 +1391,20 @@ static auto CreateFunctionSignatureInsts(
return std::nullopt;
}
context.full_pattern_stack().EndExplicitParamList();
auto [return_type_inst_id, return_form_inst_id, return_patterns_id] =
auto [return_type_inst_id, return_form_inst_id, return_pattern_id] =
GetReturnInfo(context, loc_id, clang_decl);
if (return_type_inst_id == SemIR::ErrorInst::TypeInstId) {
return std::nullopt;
}
auto match_results =
CalleePatternMatch(context, implicit_param_patterns_id, param_patterns_id,
return_patterns_id);
auto match_results = CalleePatternMatch(context, implicit_param_patterns_id,
param_patterns_id, return_pattern_id);
return {{.implicit_param_patterns_id = implicit_param_patterns_id,
.param_patterns_id = param_patterns_id,
.return_type_inst_id = return_type_inst_id,
.return_form_inst_id = return_form_inst_id,
.return_patterns_id = return_patterns_id,
.return_pattern_id = return_pattern_id,
.call_param_patterns_id = match_results.call_param_patterns_id,
.call_params_id = match_results.call_params_id,
.param_ranges = match_results.param_ranges}};
@@ -1518,7 +1516,7 @@ static auto ImportFunction(Context& context, SemIR::LocId loc_id,
.call_param_ranges = function_params_insts->param_ranges,
.return_type_inst_id = function_params_insts->return_type_inst_id,
.return_form_inst_id = function_params_insts->return_form_inst_id,
.return_patterns_id = function_params_insts->return_patterns_id,
.return_pattern_id = function_params_insts->return_pattern_id,
.virtual_modifier = virtual_modifier,
.virtual_index = virtual_index,
.evaluation_mode = evaluation_mode,