carbon-lang/toolchain/check/handle_pattern_binding.cpp

// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "toolchain/check/context.h"
#include "toolchain/check/convert.h"
#include "toolchain/sem_ir/inst.h"

namespace Carbon::Check {

auto HandleAddress(Context& context, Parse::Node parse_node) -> bool {
  auto self_param_id =
      context.node_stack().Peek<Parse::NodeKind::PatternBinding>();
  if (auto self_param =
          context.insts().Get(self_param_id).TryAs<SemIR::SelfParameter>()) {
    self_param->is_addr_self = SemIR::BoolValue::True;
    context.insts().Set(self_param_id, *self_param);
  } else {
    CARBON_DIAGNOSTIC(AddrOnNonSelfParameter, Error,
                      "`addr` can only be applied to a `self` parameter");
    context.emitter().Emit(parse_node, AddrOnNonSelfParameter);
  }
  return true;
}

auto HandleGenericPatternBinding(Context& context, Parse::Node parse_node)
    -> bool {
  return context.TODO(parse_node, "GenericPatternBinding");
}

auto HandlePatternBinding(Context& context, Parse::Node parse_node) -> bool {
  auto [type_node, parsed_type_id] =
      context.node_stack().PopExprWithParseNode();
  auto type_node_copy = type_node;
  auto cast_type_id = ExprAsType(context, type_node, parsed_type_id);

  // A `self` binding doesn't have a name.
  if (auto self_node =
          context.node_stack()
              .PopForSoloParseNodeIf<Parse::NodeKind::SelfValueName>()) {
    if (context.parse_tree().node_kind(context.node_stack().PeekParseNode()) !=
        Parse::NodeKind::ImplicitParameterListStart) {
      CARBON_DIAGNOSTIC(
          SelfOutsideImplicitParameterList, Error,
          "`self` can only be declared in an implicit parameter list");
      context.emitter().Emit(parse_node, SelfOutsideImplicitParameterList);
    }
    context.AddInstAndPush(
        parse_node,
        SemIR::SelfParameter{*self_node, cast_type_id,
                             /*is_addr_self=*/SemIR::BoolValue::False});
    return true;
  }

  // TODO: Handle `_` bindings.

  // Every other kind of pattern binding has a name.
  auto [name_node, name_id] =
      context.node_stack().PopWithParseNode<Parse::NodeKind::Name>();

  // Allocate an instruction of the appropriate kind, linked to the name for
  // error locations.
  switch (auto context_parse_node_kind = context.parse_tree().node_kind(
              context.node_stack().PeekParseNode())) {
    case Parse::NodeKind::VariableIntroducer: {
      // A `var` declaration at class scope introduces a field.
      auto enclosing_class_decl = context.GetCurrentScopeAs<SemIR::ClassDecl>();
      if (!context.TryToCompleteType(cast_type_id, [&] {
            CARBON_DIAGNOSTIC(IncompleteTypeInVarDecl, Error,
                              "{0} has incomplete type `{1}`.", llvm::StringRef,
                              std::string);
            return context.emitter().Build(
                type_node_copy, IncompleteTypeInVarDecl,
                enclosing_class_decl ? "Field" : "Variable",
                context.sem_ir().StringifyType(cast_type_id, true));
          })) {
        cast_type_id = SemIR::TypeId::Error;
      }
      SemIR::InstId value_id = SemIR::InstId::Invalid;
      SemIR::TypeId value_type_id = cast_type_id;
      if (enclosing_class_decl) {
        auto& class_info =
            context.classes().Get(enclosing_class_decl->class_id);
        auto field_type_inst_id = context.AddInst(SemIR::UnboundFieldType{
            parse_node, context.GetBuiltinType(SemIR::BuiltinKind::TypeType),
            class_info.self_type_id, cast_type_id});
        value_type_id = context.CanonicalizeType(field_type_inst_id);
        value_id = context.AddInst(
            SemIR::Field{parse_node, value_type_id, name_id,
                         SemIR::MemberIndex(context.args_type_info_stack()
                                                .PeekCurrentBlockContents()
                                                .size())});

        // Add a corresponding field to the object representation of the class.
        context.args_type_info_stack().AddInst(
            SemIR::StructTypeField{parse_node, name_id, cast_type_id});
      } else {
        value_id = context.AddInst(
            SemIR::VarStorage{name_node, value_type_id, name_id});
      }
      context.AddInstAndPush(
          parse_node,
          SemIR::BindName{name_node, value_type_id, name_id, value_id});
      break;
    }

    case Parse::NodeKind::ImplicitParameterListStart:
    case Parse::NodeKind::ParameterListStart:
      // Parameters can have incomplete types in a function declaration, but not
      // in a function definition. We don't know which kind we have here.
      context.AddInstAndPush(
          parse_node, SemIR::Parameter{name_node, cast_type_id, name_id});
      // TODO: Create a `BindName` instruction.
      break;

    case Parse::NodeKind::LetIntroducer:
      if (!context.TryToCompleteType(cast_type_id, [&] {
            CARBON_DIAGNOSTIC(IncompleteTypeInLetDecl, Error,
                              "`let` binding has incomplete type `{0}`.",
                              std::string);
            return context.emitter().Build(
                type_node_copy, IncompleteTypeInLetDecl,
                context.sem_ir().StringifyType(cast_type_id, true));
          })) {
        cast_type_id = SemIR::TypeId::Error;
      }
      // Create the instruction, but don't add it to a block until after we've
      // formed its initializer.
      // TODO: For general pattern parsing, we'll need to create a block to hold
      // the `let` pattern before we see the initializer.
      context.node_stack().Push(
          parse_node,
          context.insts().AddInNoBlock(SemIR::BindName{
              name_node, cast_type_id, name_id, SemIR::InstId::Invalid}));
      break;

    default:
      CARBON_FATAL() << "Found a pattern binding in unexpected context "
                     << context_parse_node_kind;
  }
  return true;
}

auto HandleTemplate(Context& context, Parse::Node parse_node) -> bool {
  return context.TODO(parse_node, "HandleTemplate");
}

}  // namespace Carbon::Check