carbon-lang/toolchain/check/handle_operator.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/control_flow.h"
#include "toolchain/check/convert.h"
#include "toolchain/check/core_identifier.h"
#include "toolchain/check/handle.h"
#include "toolchain/check/inst.h"
#include "toolchain/check/operator.h"
#include "toolchain/check/pointer_dereference.h"
#include "toolchain/check/type.h"
#include "toolchain/diagnostics/emitter.h"
#include "toolchain/parse/typed_nodes.h"
#include "toolchain/sem_ir/expr_info.h"

namespace Carbon::Check {

// Common logic for unary operator handlers.
static auto HandleUnaryOperator(Context& context, Parse::AnyExprId expr_node_id,
                                CoreIdentifier interface_name) -> bool {
  auto operand_id = context.node_stack().PopExpr();
  auto result_id = BuildUnaryOperator(
      context, expr_node_id, {.interface_name = interface_name}, operand_id);
  context.node_stack().Push(expr_node_id, result_id);
  return true;
}

// Common logic for binary operator handlers.
static auto HandleBinaryOperator(Context& context,
                                 Parse::AnyExprId expr_node_id,
                                 CoreIdentifier interface_name,
                                 CoreIdentifier op_name = CoreIdentifier::Op)
    -> bool {
  auto rhs_id = context.node_stack().PopExpr();
  auto lhs_id = context.node_stack().PopExpr();
  // All the `*With` binary operator interfaces take a single argument that is
  // the type of the RHS operand. `as` has different rules and we don't call
  // this function for it.
  SemIR::InstId args[] = {
      context.types().GetTypeInstId(context.insts().Get(rhs_id).type_id())};
  auto result_id = BuildBinaryOperator(context, expr_node_id,
                                       {.interface_name = interface_name,
                                        .interface_args_ref = args,
                                        .op_name = op_name},
                                       lhs_id, rhs_id);
  context.node_stack().Push(expr_node_id, result_id);
  return true;
}

auto HandleParseNode(Context& context, Parse::InfixOperatorAmpId node_id)
    -> bool {
  // TODO: Facet type intersection may need to be handled directly.
  return HandleBinaryOperator(context, node_id, CoreIdentifier::BitAndWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorAmpEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id,
                              CoreIdentifier::BitAndAssignWith);
}

auto HandleParseNode(Context& context, Parse::UnsafeModifierId node_id)
    -> bool {
  auto [rhs_node, rhs_id] = context.node_stack().PopExprWithNodeId();
  context.node_stack().Push(node_id, rhs_id);
  return true;
}

auto HandleParseNode(Context& context, Parse::InfixOperatorAsId node_id)
    -> bool {
  auto [rhs_node, rhs_id] = context.node_stack().PopExprWithNodeId();
  auto [lhs_node, lhs_id] = context.node_stack().PopExprWithNodeId();

  bool unsafe = context.parse_tree().node_kind(lhs_node) ==
                Parse::NodeKind::UnsafeModifier;

  auto rhs_type_id = ExprAsType(context, rhs_node, rhs_id).type_id;
  context.node_stack().Push(
      node_id,
      ConvertForExplicitAs(context, node_id, lhs_id, rhs_type_id, unsafe));
  return true;
}

auto HandleParseNode(Context& context, Parse::InfixOperatorCaretId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::BitXorWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorCaretEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id,
                              CoreIdentifier::BitXorAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorEqualId node_id)
    -> bool {
  // TODO: Switch to using assignment interface for most assignment. Some cases
  // may need to be handled directly.
  //
  //   return HandleBinaryOperator(context, node_id,
  //                               CoreIdentifier::AssignWith);

  auto [rhs_node, rhs_id] = context.node_stack().PopExprWithNodeId();
  auto [lhs_node, lhs_id] = context.node_stack().PopExprWithNodeId();
  auto lhs_type_id = context.insts().Get(lhs_id).type_id();
  auto lhs_quals =
      context.types().GetUnqualifiedTypeAndQualifiers(lhs_type_id).second;
  if (auto lhs_cat = SemIR::GetExprCategory(context.sem_ir(), lhs_id);
      (lhs_cat != SemIR::ExprCategory::Dependent &&
       lhs_cat != SemIR::ExprCategory::DurableRef &&
       lhs_cat != SemIR::ExprCategory::Error) ||
      lhs_quals.HasAnyOf(SemIR::TypeQualifiers::Const)) {
    CARBON_DIAGNOSTIC(AssignmentToNonAssignable, Error,
                      "expression is not assignable");
    context.emitter().Emit(lhs_node, AssignmentToNonAssignable);
  }
  // TODO: Destroy the old value before reinitializing. This will require
  // building the destruction code before we build the RHS subexpression.
  rhs_id = InitializeExisting(context, node_id, lhs_id, rhs_id);
  AddInst<SemIR::Assign>(context, node_id,
                         {.lhs_id = lhs_id, .rhs_id = rhs_id});
  // We model assignment as an expression, so we need to push a value for
  // it, even though it doesn't produce a value.
  // TODO: Consider changing our parse tree to model assignment as a
  // different kind of statement than an expression statement.
  context.node_stack().Push(node_id, lhs_id);
  return true;
}

auto HandleParseNode(Context& context, Parse::InfixOperatorEqualEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::EqWith,
                              CoreIdentifier::Equal);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorExclaimEqualId node_id) -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::EqWith,
                              CoreIdentifier::NotEqual);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorGreaterId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::OrderedWith,
                              CoreIdentifier::Greater);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorGreaterEqualId node_id) -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::OrderedWith,
                              CoreIdentifier::GreaterOrEquivalent);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorGreaterGreaterId node_id) -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::RightShiftWith);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorGreaterGreaterEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id,
                              CoreIdentifier::RightShiftAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorLessId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::OrderedWith,
                              CoreIdentifier::Less);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorLessEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::OrderedWith,
                              CoreIdentifier::LessOrEquivalent);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorLessEqualGreaterId node_id) -> bool {
  return context.TODO(node_id, "remove <=> operator that is not in the design");
}

auto HandleParseNode(Context& context, Parse::InfixOperatorLessLessId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::LeftShiftWith);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorLessLessEqualId node_id) -> bool {
  return HandleBinaryOperator(context, node_id,
                              CoreIdentifier::LeftShiftAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorMinusId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::SubWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorMinusEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::SubAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorPercentId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::ModWith);
}

auto HandleParseNode(Context& context,
                     Parse::InfixOperatorPercentEqualId node_id) -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::ModAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorPipeId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::BitOrWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorPipeEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id,
                              CoreIdentifier::BitOrAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorPlusId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::AddWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorPlusEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::AddAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorSlashId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::DivWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorSlashEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::DivAssignWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorStarId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::MulWith);
}

auto HandleParseNode(Context& context, Parse::InfixOperatorStarEqualId node_id)
    -> bool {
  return HandleBinaryOperator(context, node_id, CoreIdentifier::MulAssignWith);
}

auto HandleParseNode(Context& context, Parse::PostfixOperatorStarId node_id)
    -> bool {
  auto value_id = context.node_stack().PopExpr();
  auto inner_type = ExprAsType(context, node_id, value_id);
  AddInstAndPush<SemIR::PointerType>(
      context, node_id,
      {.type_id = SemIR::TypeType::TypeId, .pointee_id = inner_type.inst_id});
  return true;
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorAmpId node_id)
    -> bool {
  auto value_id = context.node_stack().PopExpr();
  auto type_id = context.insts().Get(value_id).type_id();
  // Only durable reference expressions can have their address taken.
  switch (SemIR::GetExprCategory(context.sem_ir(), value_id)) {
    case SemIR::ExprCategory::DurableRef:
    case SemIR::ExprCategory::Error:
      break;
    default:
      CARBON_DIAGNOSTIC(AddrOfNonRef, Error,
                        "cannot take the address of non-reference expression");
      context.emitter().Emit(LocIdForDiagnostics::TokenOnly(node_id),
                             AddrOfNonRef);
      value_id = SemIR::ErrorInst::InstId;
      break;
  }
  // TODO: Preserve spelling of type of operand where possible.
  auto type_inst_id = context.types().GetTypeInstId(type_id);
  AddInstAndPush<SemIR::AddrOf>(
      context, node_id,
      SemIR::AddrOf{.type_id = GetPointerType(context, type_inst_id),
                    .lvalue_id = value_id});
  return true;
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorCaretId node_id)
    -> bool {
  return HandleUnaryOperator(context, node_id, CoreIdentifier::BitComplement);
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorConstId node_id)
    -> bool {
  auto value_id = context.node_stack().PopExpr();

  // `const (const T)` is probably not what the developer intended.
  // TODO: Detect `const (const T)*` and suggest moving the `*` inside the
  // parentheses.
  if (context.insts().Get(value_id).kind() == SemIR::ConstType::Kind) {
    CARBON_DIAGNOSTIC(RepeatedConst, Warning,
                      "`const` applied repeatedly to the same type has no "
                      "additional effect");
    context.emitter().Emit(node_id, RepeatedConst);
  }
  auto inner_type = ExprAsType(context, node_id, value_id);
  AddInstAndPush<SemIR::ConstType>(
      context, node_id,
      {.type_id = SemIR::TypeType::TypeId, .inner_id = inner_type.inst_id});
  return true;
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorMinusId node_id)
    -> bool {
  return HandleUnaryOperator(context, node_id, CoreIdentifier::Negate);
}

auto HandleParseNode(Context& context,
                     Parse::PrefixOperatorMinusMinusId node_id) -> bool {
  return HandleUnaryOperator(context, node_id, CoreIdentifier::Dec);
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorNotId node_id)
    -> bool {
  auto value_id = context.node_stack().PopExpr();
  value_id = ConvertToBoolValue(context, node_id, value_id);
  AddInstAndPush<SemIR::UnaryOperatorNot>(
      context, node_id,
      {.type_id = context.insts().Get(value_id).type_id(),
       .operand_id = value_id});
  return true;
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorPartialId node_id)
    -> bool {
  auto value_id = context.node_stack().PopExpr();
  auto inner_type = ExprAsType(context, node_id, value_id);
  auto class_type =
      context.types().TryGetAs<SemIR::ClassType>(inner_type.type_id);

  if (!class_type ||
      context.classes().Get(class_type->class_id).inheritance_kind ==
          SemIR::Class::InheritanceKind::Final) {
    CARBON_DIAGNOSTIC(PartialOnFinal, Error,
                      "`partial` applied to final type {0}", SemIR::TypeId);
    context.emitter().Emit(node_id, PartialOnFinal, inner_type.type_id);
  }

  AddInstAndPush<SemIR::PartialType>(
      context, node_id,
      {.type_id = SemIR::TypeType::TypeId, .inner_id = inner_type.inst_id});
  return true;
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorPlusPlusId node_id)
    -> bool {
  return HandleUnaryOperator(context, node_id, CoreIdentifier::Inc);
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorRefId node_id)
    -> bool {
  auto expr_id = context.node_stack().PopExpr();
  auto ref_id = AddInst<SemIR::RefTagExpr>(
      context, node_id,
      {.type_id = context.insts().Get(expr_id).type_id(), .expr_id = expr_id});
  context.node_stack().Push(node_id, ref_id);
  return true;
}

auto HandleParseNode(Context& context, Parse::PrefixOperatorStarId node_id)
    -> bool {
  auto base_id = context.node_stack().PopExpr();

  auto deref_base_id = PerformPointerDereference(
      context, node_id, base_id,
      [&context, &node_id](SemIR::TypeId not_pointer_type_id) {
        // TODO: Pass in the expression we're trying to dereference to produce a
        // better diagnostic.
        CARBON_DIAGNOSTIC(DerefOfNonPointer, Error,
                          "cannot dereference operand of non-pointer type {0}",
                          SemIR::TypeId);

        auto builder =
            context.emitter().Build(LocIdForDiagnostics::TokenOnly(node_id),
                                    DerefOfNonPointer, not_pointer_type_id);

        // TODO: Check for any facet here, rather than only a type.
        if (not_pointer_type_id == SemIR::TypeType::TypeId) {
          CARBON_DIAGNOSTIC(
              DerefOfType, Note,
              "to form a pointer type, write the `*` after the pointee type");
          builder.Note(LocIdForDiagnostics::TokenOnly(node_id), DerefOfType);
        }

        builder.Emit();
      });

  context.node_stack().Push(node_id, deref_base_id);
  return true;
}

// Adds the branch for a short circuit operand.
static auto HandleShortCircuitOperand(Context& context, Parse::NodeId node_id,
                                      bool is_or) -> bool {
  // Convert the condition to `bool`.
  auto [cond_node, cond_value_id] = context.node_stack().PopExprWithNodeId();
  cond_value_id = ConvertToBoolValue(context, node_id, cond_value_id);
  auto bool_type_id = context.insts().Get(cond_value_id).type_id();

  // Compute the branch value: the condition for `and`, inverted for `or`.
  SemIR::InstId branch_value_id =
      is_or ? AddInst<SemIR::UnaryOperatorNot>(
                  context, node_id,
                  {.type_id = bool_type_id, .operand_id = cond_value_id})
            : cond_value_id;
  auto short_circuit_result_id = AddInst<SemIR::BoolLiteral>(
      context, node_id,
      {.type_id = bool_type_id, .value = SemIR::BoolValue::From(is_or)});

  // Create a block for the right-hand side and for the continuation.
  auto rhs_block_id =
      AddDominatedBlockAndBranchIf(context, node_id, branch_value_id);
  auto end_block_id = AddDominatedBlockAndBranchWithArg(
      context, node_id, short_circuit_result_id);

  // Push the branch condition and result for use when handling the complete
  // expression.
  context.node_stack().Push(cond_node, branch_value_id);
  context.node_stack().Push(cond_node, short_circuit_result_id);

  // Push the resumption and the right-hand side blocks, and start emitting the
  // right-hand operand.
  context.inst_block_stack().Pop();
  context.inst_block_stack().Push(end_block_id);
  context.inst_block_stack().Push(rhs_block_id);
  context.region_stack().AddToRegion(rhs_block_id, node_id);

  // HandleShortCircuitOperator will follow, and doesn't need the operand on the
  // node stack.
  return true;
}

auto HandleParseNode(Context& context, Parse::ShortCircuitOperandAndId node_id)
    -> bool {
  return HandleShortCircuitOperand(context, node_id, /*is_or=*/false);
}

auto HandleParseNode(Context& context, Parse::ShortCircuitOperandOrId node_id)
    -> bool {
  return HandleShortCircuitOperand(context, node_id, /*is_or=*/true);
}

// Short circuit operator handling is uniform because the branching logic
// occurs during operand handling.
static auto HandleShortCircuitOperator(Context& context, Parse::NodeId node_id)
    -> bool {
  if (!context.scope_stack().IsInFunctionScope()) {
    return context.TODO(node_id,
                        "Control flow expressions are currently only supported "
                        "inside functions.");
  }
  auto [rhs_node, rhs_id] = context.node_stack().PopExprWithNodeId();
  auto short_circuit_result_id = context.node_stack().PopExpr();
  auto branch_value_id = context.node_stack().PopExpr();

  // The first operand is wrapped in a ShortCircuitOperand, which we
  // already handled by creating a RHS block and a resumption block, which
  // are the current block and its enclosing block.
  rhs_id = ConvertToBoolValue(context, node_id, rhs_id);

  // When the second operand is evaluated, the result of `and` and `or` is
  // its value.
  auto resume_block_id = context.inst_block_stack().PeekOrAdd(/*depth=*/1);
  AddInst<SemIR::BranchWithArg>(
      context, node_id, {.target_id = resume_block_id, .arg_id = rhs_id});
  context.inst_block_stack().Pop();
  context.region_stack().AddToRegion(resume_block_id, node_id);

  // Collect the result from either the first or second operand.
  auto result_id = AddInst<SemIR::BlockArg>(
      context, node_id,
      {.type_id = context.insts().Get(rhs_id).type_id(),
       .block_id = resume_block_id});
  SetBlockArgResultBeforeConstantUse(context, result_id, branch_value_id,
                                     rhs_id, short_circuit_result_id);
  context.node_stack().Push(node_id, result_id);
  return true;
}

auto HandleParseNode(Context& context, Parse::ShortCircuitOperatorAndId node_id)
    -> bool {
  return HandleShortCircuitOperator(context, node_id);
}

auto HandleParseNode(Context& context, Parse::ShortCircuitOperatorOrId node_id)
    -> bool {
  return HandleShortCircuitOperator(context, node_id);
}

}  // namespace Carbon::Check