carbon-lang/toolchain/sem_ir/expr_info.h

// 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

#ifndef CARBON_TOOLCHAIN_SEM_IR_EXPR_INFO_H_
#define CARBON_TOOLCHAIN_SEM_IR_EXPR_INFO_H_

#include <cstdint>

#include "toolchain/sem_ir/file.h"
#include "toolchain/sem_ir/ids.h"

namespace Carbon::SemIR {

// The expression category of a sem_ir instruction. See /docs/design/values.md
// for details.
enum class ExprCategory : int8_t {
  // This instruction does not correspond to an expression, and as such has no
  // category.
  NotExpr,
  // The category of this instruction is not known due to an error.
  Error,
  // This instruction represents a value expression.
  Value,
  // This instruction represents a durable reference expression, that denotes an
  // object that outlives the current full expression context.
  DurableRef,
  // This instruction represents an ephemeral reference expression, that denotes
  // an object that does not outlive the current full expression context.
  EphemeralRef,
  // This instruction represents an initializing expression, that describes how
  // to initialize an object.
  Initializing,
  // This instruction represents a syntactic combination of expressions that are
  // permitted to have different expression categories. This is used for tuple
  // and struct literals, where the subexpressions for different elements can
  // have different categories.
  Mixed,
  Last = Mixed
};

// Returns the expression category for an instruction.
auto GetExprCategory(const File& file, InstId inst_id) -> ExprCategory;

// Returns whether the given expression category is for a reference expression.
inline auto IsRefCategory(ExprCategory cat) -> bool {
  return cat == ExprCategory::DurableRef || cat == ExprCategory::EphemeralRef;
}

// Given an initializing expression, find its return slot argument. Returns
// `None` if there is no return slot, because the initialization is not
// performed in place.
auto FindReturnSlotArgForInitializer(const File& sem_ir, InstId init_id)
    -> InstId;

}  // namespace Carbon::SemIR

#endif  // CARBON_TOOLCHAIN_SEM_IR_EXPR_INFO_H_