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Implement support for copying C++ classes. (#6434)
When performing impl lookup for `Core.Copy` for a C++ class type, look for a copy constructor. If we find one, synthesize an impl witness that calls the constructor. This adds initial support for impl lookup to delegate to the C++ interop logic for queries involving C++ types. For now, we don't implement the rules from #6166 that compare a synthesized type structure for the C++ impl against the best Carbon type structure, but the framework for building that support is established here. Currently there is no caching of the lookup here, and we build unique `ImplWitnessTable`s for each lookup, which leads to each impl lookup producing a distinct facet value. This results in some errors in generic contexts; this will be addressed in follow-up changes. This PR aims only to support the non-generic case. --------- Co-authored-by: Dana Jansens <danakj@orodu.net> Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
This commit is contained in:
Richard Smith
co-authored by
Dana Jansens
Carbon Infra Bot
Dana Jansens
Carbon Infra Bot
parent
19660ccde0
commit
372f632d9d
+83
-66
@@ -9,6 +9,7 @@
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#include "toolchain/base/kind_switch.h"
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#include "toolchain/check/call.h"
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#include "toolchain/check/convert.h"
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#include "toolchain/check/cpp/operators.h"
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#include "toolchain/check/deferred_definition_worklist.h"
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#include "toolchain/check/diagnostic_helpers.h"
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#include "toolchain/check/function.h"
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@@ -213,67 +214,6 @@ static auto HasDeclaredReturnType(Context& context,
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.return_slot_pattern_id.has_value();
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}
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auto BuildThunk(Context& context, SemIR::FunctionId signature_id,
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SemIR::SpecificId signature_specific_id,
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SemIR::InstId callee_id) -> SemIR::InstId {
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auto callee = SemIR::GetCalleeAsFunction(context.sem_ir(), callee_id);
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// Check whether we can use the given function without a thunk.
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// TODO: For virtual functions, we want different rules for checking `self`.
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// TODO: This is too strict; for example, we should not compare parameter
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// names here.
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if (CheckFunctionTypeMatches(
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context, context.functions().Get(callee.function_id),
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context.functions().Get(signature_id), signature_specific_id,
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/*check_syntax=*/false, /*check_self=*/true, /*diagnose=*/false)) {
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return callee_id;
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}
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// From P3763:
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// If the function in the interface does not have a return type, the
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// program is invalid if the function in the impl specifies a return type.
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//
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// Call into the redeclaration checking logic to produce a suitable error.
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//
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// TODO: Consider a different rule: always use an explicit return type for the
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// thunk, and always convert the result of the wrapped call to the return type
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// of the thunk.
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if (!HasDeclaredReturnType(context, signature_id) &&
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HasDeclaredReturnType(context, callee.function_id)) {
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bool success = CheckFunctionReturnTypeMatches(
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context, context.functions().Get(callee.function_id),
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context.functions().Get(signature_id), signature_specific_id);
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CARBON_CHECK(!success, "Return type unexpectedly matches");
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return SemIR::ErrorInst::InstId;
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}
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// Create a scope for the function's parameters and generic parameters.
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context.scope_stack().PushForDeclName();
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// We can't use the function directly. Build a thunk.
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// TODO: Check for and diagnose obvious reasons why this will fail, such as
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// arity mismatch, before trying to build the thunk.
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auto [function_id, thunk_id] =
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CloneFunctionDecl(context, SemIR::LocId(callee_id), signature_id,
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signature_specific_id, callee.function_id);
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// Track that this function is a thunk.
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context.functions().Get(function_id).SetThunk(callee_id);
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// Register the thunk to be defined when we reach the end of the enclosing
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// deferred definition scope, for example an `impl` or `class` definition, as
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// if the thunk's body were written inline in this location.
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context.deferred_definition_worklist().SuspendThunkAndPush(
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context, {
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.signature_id = signature_id,
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.function_id = function_id,
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.decl_id = thunk_id,
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.callee_id = callee_id,
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});
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return thunk_id;
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}
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// Build an expression that names the value matched by a pattern.
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static auto BuildPatternRef(Context& context,
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llvm::ArrayRef<SemIR::InstId> arg_ids,
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@@ -303,16 +243,25 @@ auto PerformThunkCall(Context& context, SemIR::LocId loc_id,
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SemIR::InstId callee_id) -> SemIR::InstId {
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auto& function = context.functions().Get(function_id);
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llvm::SmallVector<SemIR::InstId> args;
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// If we have a self parameter, form `self.<callee_id>`.
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if (function.self_param_id.has_value()) {
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callee_id = PerformCompoundMemberAccess(
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context, loc_id,
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BuildPatternRef(context, call_arg_ids, function.self_param_id),
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callee_id);
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auto self_arg_id =
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BuildPatternRef(context, call_arg_ids, function.self_param_id);
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if (IsCppConstructorOrNonMethodOperator(context, callee_id)) {
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// When calling a C++ constructor to implement `Copy`, or calling a C++
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// non-method operator to implement a Carbon operator, the interface has a
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// `self` parameter but C++ models that parameter as an explicit argument
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// instead, so add the `self` to the argument list instead in that case.
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args.push_back(self_arg_id);
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} else {
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callee_id =
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PerformCompoundMemberAccess(context, loc_id, self_arg_id, callee_id);
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}
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}
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// Form an argument list.
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llvm::SmallVector<SemIR::InstId> args;
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for (auto pattern_id :
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context.inst_blocks().Get(function.param_patterns_id)) {
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args.push_back(BuildPatternRef(context, call_arg_ids, pattern_id));
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@@ -423,4 +372,72 @@ auto BuildThunkDefinition(Context& context,
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context.scope_stack().Pop();
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}
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auto BuildThunk(Context& context, SemIR::FunctionId signature_id,
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SemIR::SpecificId signature_specific_id,
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SemIR::InstId callee_id, bool defer_definition)
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-> SemIR::InstId {
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auto callee = SemIR::GetCalleeAsFunction(context.sem_ir(), callee_id);
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// Check whether we can use the given function without a thunk.
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// TODO: For virtual functions, we want different rules for checking `self`.
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// TODO: This is too strict; for example, we should not compare parameter
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// names here.
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if (CheckFunctionTypeMatches(
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context, context.functions().Get(callee.function_id),
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context.functions().Get(signature_id), signature_specific_id,
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/*check_syntax=*/false, /*check_self=*/true, /*diagnose=*/false)) {
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return callee_id;
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}
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// From P3763:
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// If the function in the interface does not have a return type, the
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// program is invalid if the function in the impl specifies a return type.
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//
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// Call into the redeclaration checking logic to produce a suitable error.
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//
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// TODO: Consider a different rule: always use an explicit return type for the
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// thunk, and always convert the result of the wrapped call to the return type
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// of the thunk.
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if (!HasDeclaredReturnType(context, signature_id) &&
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HasDeclaredReturnType(context, callee.function_id)) {
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bool success = CheckFunctionReturnTypeMatches(
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context, context.functions().Get(callee.function_id),
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context.functions().Get(signature_id), signature_specific_id);
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CARBON_CHECK(!success, "Return type unexpectedly matches");
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return SemIR::ErrorInst::InstId;
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}
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// Create a scope for the function's parameters and generic parameters.
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context.scope_stack().PushForDeclName();
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// We can't use the function directly. Build a thunk.
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// TODO: Check for and diagnose obvious reasons why this will fail, such as
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// arity mismatch, before trying to build the thunk.
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auto [function_id, thunk_id] =
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CloneFunctionDecl(context, SemIR::LocId(callee_id), signature_id,
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signature_specific_id, callee.function_id);
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// Track that this function is a thunk.
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context.functions().Get(function_id).SetThunk(callee_id);
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if (defer_definition) {
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// Register the thunk to be defined when we reach the end of the enclosing
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// deferred definition scope, for example an `impl` or `class` definition,
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// as if the thunk's body were written inline in this location.
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context.deferred_definition_worklist().SuspendThunkAndPush(
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context, {
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.signature_id = signature_id,
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.function_id = function_id,
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.decl_id = thunk_id,
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.callee_id = callee_id,
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});
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} else {
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BuildThunkDefinition(context, signature_id, function_id, thunk_id,
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callee_id);
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context.scope_stack().Pop();
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}
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return thunk_id;
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}
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} // namespace Carbon::Check
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