carbon-lang/toolchain/check/pattern.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_CHECK_PATTERN_H_
#define CARBON_TOOLCHAIN_CHECK_PATTERN_H_

#include "toolchain/check/context.h"
#include "toolchain/sem_ir/ids.h"

namespace Carbon::Check {

// Marks the start of a region of insts in a pattern context that might
// represent an expression or a pattern. Typically this is called when
// handling a parse node that can immediately precede a subpattern (such
// as `let` or a `,` in a pattern list), and the handler for the subpattern
// node makes the matching `EndSubpatternAs*` call.
auto BeginSubpattern(Context& context) -> void;

// Ends a region started by BeginSubpattern (in stack order), treating it as
// an expression with the given result, and returns the ID of the region. The
// region will not yet have any control-flow edges into or out of it.
auto EndSubpatternAsExpr(Context& context, SemIR::InstId result_id)
    -> SemIR::ExprRegionId;

// Ends a region started by BeginSubpattern (in stack order), asserting that
// it had no expression content.
auto EndSubpatternAsNonExpr(Context& context) -> void;

// Information about a created binding pattern.
struct BindingPatternInfo {
  SemIR::InstId pattern_id;
  SemIR::InstId bind_id;
};

// TODO: Add EndSubpatternAsPattern, when needed.

// The phase of a binding pattern.
enum class BindingPhase { Template, Symbolic, Runtime };

// Creates an entity name for a binding pattern with the given properties.
auto AddBindingEntityName(Context& context, SemIR::NameId name_id,
                          SemIR::ConstantId form_id, bool is_unused,
                          BindingPhase phase) -> SemIR::EntityNameId;

// Creates a binding pattern and the associated binding inst, and returns their
// IDs. `type_region_id` is the region representing the binding's type
// expression.
auto AddBindingPattern(Context& context, SemIR::LocId name_loc,
                       SemIR::ExprRegionId type_region_id,
                       SemIR::AnyBindingPattern pattern) -> BindingPatternInfo;

// Creates storage for `var` patterns nested within the given pattern at the
// current location in the output SemIR. For a `returned var`, this
// reuses the function's return slot when present.
auto AddPatternVarStorage(Context& context, SemIR::InstBlockId pattern_block_id,
                          bool is_returned_var) -> void;

// Adds a parameter pattern with the specified name and type information. The
// pattern emulates `x: T` or `ref x: T` depending on the value of
// `is_ref` (`var x: T` is not supported). This only sets up the parameter
// pattern, binding pattern and type; callers are expected to add the returned
// parameter pattern instruction to appropriate blocks. This is used when
// generating functions, rather than processing a user-authored declaration.
auto AddParamPattern(Context& context, SemIR::LocId loc_id,
                     SemIR::NameId name_id,
                     SemIR::ExprRegionId type_expr_region_id,
                     SemIR::TypeId type_id, bool is_ref) -> SemIR::InstId;

}  // namespace Carbon::Check

#endif  // CARBON_TOOLCHAIN_CHECK_PATTERN_H_