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Richard SmithandChandler Carruth
1013d1773c
Start treating function calls as initializing expressions instead of as value expressions. This required adding support for expression categories. Value bindings and temporary materialization conversions are created where necessary to transition between expression categories. For a function call with a return slot, we speculatively create a materialized temporary before the call and either commit to it or replace it with something else later, once we see how the function call expression is actually used. This change follows the direction suggested in #3133 for initializing expressions: depending on the return type of a function, the return value will either be initialized in-place or returned directly. This is visible in the semantics IR, which is a little unfortunate but is probably necessary as this is part of the semantics of the program. --------- Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
91 lines
3.4 KiB
C++
91 lines
3.4 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "toolchain/semantics/semantics_context.h"
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#include "toolchain/semantics/semantics_node.h"
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namespace Carbon::Check {
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auto HandleExpressionStatement(Context& context, ParseTree::Node /*parse_node*/)
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-> bool {
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context.HandleDiscardedExpression(context.node_stack().PopExpression());
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return true;
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}
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auto HandleReturnStatement(Context& context, ParseTree::Node parse_node)
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-> bool {
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CARBON_CHECK(!context.return_scope_stack().empty());
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const auto& fn_node =
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context.semantics_ir().GetNode(context.return_scope_stack().back());
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const auto& callable =
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context.semantics_ir().GetFunction(fn_node.GetAsFunctionDeclaration());
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if (context.parse_tree().node_kind(context.node_stack().PeekParseNode()) ==
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ParseNodeKind::ReturnStatementStart) {
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context.node_stack()
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.PopAndDiscardSoloParseNode<ParseNodeKind::ReturnStatementStart>();
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if (callable.return_type_id.is_valid()) {
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// TODO: Add a note pointing at the return type's parse node.
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CARBON_DIAGNOSTIC(ReturnStatementMissingExpression, Error,
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"Must return a {0}.", std::string);
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context.emitter()
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.Build(parse_node, ReturnStatementMissingExpression,
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context.semantics_ir().StringifyType(callable.return_type_id))
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.Emit();
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}
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context.AddNode(SemIR::Node::Return::Make(parse_node));
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} else {
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auto arg = context.node_stack().PopExpression();
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context.node_stack()
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.PopAndDiscardSoloParseNode<ParseNodeKind::ReturnStatementStart>();
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if (!callable.return_type_id.is_valid()) {
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CARBON_DIAGNOSTIC(
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ReturnStatementDisallowExpression, Error,
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"No return expression should be provided in this context.");
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CARBON_DIAGNOSTIC(ReturnStatementImplicitNote, Note,
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"There was no return type provided.");
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context.emitter()
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.Build(parse_node, ReturnStatementDisallowExpression)
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.Note(fn_node.parse_node(), ReturnStatementImplicitNote)
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.Emit();
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context.AddNode(SemIR::Node::ReturnExpression::Make(parse_node, arg));
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} else if (callable.return_slot_id.is_valid()) {
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context.Initialize(parse_node, callable.return_slot_id, arg);
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context.AddNode(SemIR::Node::Return::Make(parse_node));
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} else {
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arg = context.ConvertToValueOfType(parse_node, arg,
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callable.return_type_id);
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if (SemIR::GetInitializingRepresentation(context.semantics_ir(),
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callable.return_type_id)
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.kind == SemIR::InitializingRepresentation::None) {
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context.AddNode(SemIR::Node::Return::Make(parse_node));
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} else {
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context.AddNode(SemIR::Node::ReturnExpression::Make(parse_node, arg));
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}
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}
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}
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// Switch to a new, unreachable, empty node block. This typically won't
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// contain any semantics IR, but it can do if there are statements following
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// the `return` statement.
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context.node_block_stack().Pop();
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context.node_block_stack().PushUnreachable();
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return true;
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}
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auto HandleReturnStatementStart(Context& context, ParseTree::Node parse_node)
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-> bool {
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// No action, just a bracketing node.
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context.node_stack().Push(parse_node);
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return true;
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}
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} // namespace Carbon::Check
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