carbon-lang/toolchain/parse/handle_period.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/parse/context.h"

namespace Carbon::Parse {

// Handles PeriodAs variants and ArrowExpr.
// TODO: This currently only supports identifiers on the rhs, but will in the
// future need to handle things like `object.(Interface.member)` for qualifiers.
static auto HandlePeriodOrArrow(Context& context, NodeKind node_kind,
                                bool is_arrow) -> void {
  auto state = context.PopState();

  // We're handling `.something` or `->something`.
  auto dot = context.ConsumeChecked(is_arrow ? Lex::TokenKind::MinusGreater
                                             : Lex::TokenKind::Period);

  if (context.ConsumeAndAddLeafNodeIf(Lex::TokenKind::Identifier,
                                      NodeKind::IdentifierName)) {
    // OK, `.` identifier.
  } else if (node_kind != NodeKind::QualifiedName &&
             context.ConsumeAndAddLeafNodeIf(Lex::TokenKind::Base,
                                             NodeKind::BaseName)) {
    // OK, `.base`. This is allowed in any name context other than declaring a
    // new qualified name: `fn Namespace.base() {}`
  } else {
    CARBON_DIAGNOSTIC(ExpectedIdentifierAfterDotOrArrow, Error,
                      "Expected identifier after `{0}`.", llvm::StringLiteral);
    context.emitter().Emit(
        *context.position(), ExpectedIdentifierAfterDotOrArrow,
        is_arrow ? llvm::StringLiteral("->") : llvm::StringLiteral("."));
    // If we see a keyword, assume it was intended to be a name.
    // TODO: Should keywords be valid here?
    if (context.PositionKind().is_keyword()) {
      context.AddLeafNode(NodeKind::IdentifierName, context.Consume(),
                          /*has_error=*/true);
    } else {
      context.AddLeafNode(NodeKind::IdentifierName, *context.position(),
                          /*has_error=*/true);
      // Indicate the error to the parent state so that it can avoid producing
      // more errors.
      context.ReturnErrorOnState();
    }
  }

  context.AddNode(node_kind, dot, state.subtree_start, state.has_error);
}

auto HandlePeriodAsDecl(Context& context) -> void {
  HandlePeriodOrArrow(context, NodeKind::QualifiedName,
                      /*is_arrow=*/false);
}

auto HandlePeriodAsExpr(Context& context) -> void {
  HandlePeriodOrArrow(context, NodeKind::MemberAccessExpr,
                      /*is_arrow=*/false);
}

auto HandlePeriodAsStruct(Context& context) -> void {
  HandlePeriodOrArrow(context, NodeKind::StructFieldDesignator,
                      /*is_arrow=*/false);
}

auto HandleArrowExpr(Context& context) -> void {
  HandlePeriodOrArrow(context, NodeKind::PointerMemberAccessExpr,
                      /*is_arrow=*/true);
}

}  // namespace Carbon::Parse