carbon-lang/parser/parse_tree_test.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 "parser/parse_tree.h"

#include <forward_list>

#include "diagnostics/diagnostic_emitter.h"
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "lexer/tokenized_buffer.h"
#include "lexer/tokenized_buffer_test_helpers.h"
#include "llvm/ADT/Sequence.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/YAMLParser.h"
#include "parser/parse_node_kind.h"
#include "parser/parse_test_helpers.h"

namespace Carbon {
namespace {

using Carbon::Testing::IsKeyValueScalars;
using Carbon::Testing::MatchParseTreeNodes;
using ::testing::Eq;
using ::testing::Ne;
using ::testing::NotNull;
using ::testing::StrEq;

struct ParseTreeTest : ::testing::Test {
  std::forward_list<SourceBuffer> source_storage;
  std::forward_list<TokenizedBuffer> token_storage;
  DiagnosticConsumer& consumer = ConsoleDiagnosticConsumer();

  auto GetSourceBuffer(llvm::Twine t) -> SourceBuffer& {
    source_storage.push_front(SourceBuffer::CreateFromText(t.str()));
    return source_storage.front();
  }

  auto GetTokenizedBuffer(llvm::Twine t) -> TokenizedBuffer& {
    token_storage.push_front(
        TokenizedBuffer::Lex(GetSourceBuffer(t), consumer));
    return token_storage.front();
  }
};

TEST_F(ParseTreeTest, Empty) {
  TokenizedBuffer tokens = GetTokenizedBuffer("");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes({{.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, EmptyDeclaration) {
  TokenizedBuffer tokens = GetTokenizedBuffer(";");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  auto it = tree.Postorder().begin();
  auto end = tree.Postorder().end();
  ASSERT_THAT(it, Ne(end));
  ParseTree::Node n = *it++;
  ASSERT_THAT(it, Ne(end));
  ParseTree::Node eof = *it++;
  EXPECT_THAT(it, Eq(end));

  // Directly test the main API so that we get easier to understand errors in
  // simple cases than what the custom matcher will produce.
  EXPECT_FALSE(tree.HasErrorInNode(n));
  EXPECT_FALSE(tree.HasErrorInNode(eof));
  EXPECT_THAT(tree.GetNodeKind(n), Eq(ParseNodeKind::EmptyDeclaration()));
  EXPECT_THAT(tree.GetNodeKind(eof), Eq(ParseNodeKind::FileEnd()));

  auto t = tree.GetNodeToken(n);
  ASSERT_THAT(tokens.Tokens().begin(), Ne(tokens.Tokens().end()));
  EXPECT_THAT(t, Eq(*tokens.Tokens().begin()));
  EXPECT_THAT(tokens.GetTokenText(t), Eq(";"));

  EXPECT_THAT(tree.Children(n).begin(), Eq(tree.Children(n).end()));
  EXPECT_THAT(tree.Children(eof).begin(), Eq(tree.Children(eof).end()));

  EXPECT_THAT(tree.Postorder().begin(), Eq(tree.Postorder(n).begin()));
  EXPECT_THAT(tree.Postorder(n).end(), Eq(tree.Postorder(eof).begin()));
  EXPECT_THAT(tree.Postorder(eof).end(), Eq(tree.Postorder().end()));
}

TEST_F(ParseTreeTest, BasicFunctionDeclaration) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  EXPECT_THAT(
      tree, MatchParseTreeNodes(
                {{.kind = ParseNodeKind::FunctionDeclaration(),
                  .text = "fn",
                  .children = {{ParseNodeKind::Identifier(), "F"},
                               {.kind = ParseNodeKind::ParameterList(),
                                .text = "(",
                                .children = {{ParseNodeKind::ParameterListEnd(),
                                              ")"}}},
                               {ParseNodeKind::DeclarationEnd(), ";"}}},
                 {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, NoDeclarationIntroducerOrSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer("foo bar baz");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes({{.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, NoDeclarationIntroducerWithSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer("foo;");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree,
              MatchParseTreeNodes({{.kind = ParseNodeKind::EmptyDeclaration(),
                                    .text = ";",
                                    .has_error = true},
                                   {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, JustFunctionIntroducerAndSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn;");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes(
                        {{.kind = ParseNodeKind::FunctionDeclaration(),
                          .has_error = true,
                          .children = {{ParseNodeKind::DeclarationEnd()}}},
                         {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, RepeatedFunctionIntroducerAndSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn fn;");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes(
                        {{.kind = ParseNodeKind::FunctionDeclaration(),
                          .has_error = true,
                          .children = {{ParseNodeKind::DeclarationEnd()}}},
                         {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationWithNoSignatureOrSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn foo");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes(
                        {{.kind = ParseNodeKind::FunctionDeclaration(),
                          .has_error = true,
                          .children = {{ParseNodeKind::Identifier(), "foo"}}},
                         {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest,
       FunctionDeclarationWithIdentifierInsteadOfSignatureAndSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn foo bar;");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes(
                        {{.kind = ParseNodeKind::FunctionDeclaration(),
                          .has_error = true,
                          .children = {{ParseNodeKind::Identifier(), "foo"},
                                       {ParseNodeKind::DeclarationEnd()}}},
                         {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationWithSingleIdentifierParameterList) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn foo(bar);");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  // Note: this might become valid depending on the parameter syntax, this test
  // shouldn't be taken as a sign it should remain invalid.
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(),
            .has_error = true,
            .children = {{ParseNodeKind::Identifier(), "foo"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .has_error = true,
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {ParseNodeKind::DeclarationEnd()}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationWithoutName) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn ();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes(
                        {{.kind = ParseNodeKind::FunctionDeclaration(),
                          .has_error = true,
                          .children = {{ParseNodeKind::DeclarationEnd()}}},
                         {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest,
       FunctionDeclarationWithoutNameAndManyTokensToSkipInGroupedSymbols) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn (a tokens c d e f g h i j k l m n o p q r s t u v w x y z);");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(tree, MatchParseTreeNodes(
                        {{.kind = ParseNodeKind::FunctionDeclaration(),
                          .has_error = true,
                          .children = {{ParseNodeKind::DeclarationEnd()}}},
                         {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationSkipToNewlineWithoutSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn ()\n"
      "fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(), .has_error = true},
           {.kind = ParseNodeKind::FunctionDeclaration(),
            .children = {{ParseNodeKind::Identifier(), "F"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {ParseNodeKind::DeclarationEnd()}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationSkipIndentedNewlineWithSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn (x,\n"
      "    y,\n"
      "    z);\n"
      "fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(),
            .has_error = true,
            .children = {{ParseNodeKind::DeclarationEnd()}}},
           {.kind = ParseNodeKind::FunctionDeclaration(),
            .children = {{ParseNodeKind::Identifier(), "F"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {ParseNodeKind::DeclarationEnd()}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationSkipIndentedNewlineWithoutSemi) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn (x,\n"
      "    y,\n"
      "    z)\n"
      "fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(), .has_error = true},
           {.kind = ParseNodeKind::FunctionDeclaration(),
            .children = {{ParseNodeKind::Identifier(), "F"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {ParseNodeKind::DeclarationEnd()}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationSkipIndentedNewlineUntilOutdent) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "  fn (x,\n"
      "      y,\n"
      "      z)\n"
      "fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(), .has_error = true},
           {.kind = ParseNodeKind::FunctionDeclaration(),
            .children = {{ParseNodeKind::Identifier(), "F"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {ParseNodeKind::DeclarationEnd()}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDeclarationSkipWithoutSemiToCurly) {
  // FIXME: We don't have a grammar construct that uses curlies yet so this just
  // won't parse at all. Once it does, we should ensure that the close brace
  // gets properly parsed for the struct (or whatever other curly-braced syntax
  // we have grouping function declarations) despite the invalid function
  // declaration missing a semicolon.
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "struct X { fn () }\n"
      "fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_TRUE(tree.HasErrors());
}

TEST_F(ParseTreeTest, BasicFunctionDefinition) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn F() {\n"
      "}");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(),
            .children = {{ParseNodeKind::Identifier(), "F"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {.kind = ParseNodeKind::CodeBlock(),
                          .text = "{",
                          .children = {{ParseNodeKind::CodeBlockEnd(), "}"}}}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDefinitionWithNestedBlocks) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn F() {\n"
      "  {\n"
      "    {{}}\n"
      "  }\n"
      "}");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(),
            .children =
                {{ParseNodeKind::Identifier(), "F"},
                 {.kind = ParseNodeKind::ParameterList(),
                  .children = {{ParseNodeKind::ParameterListEnd()}}},
                 {.kind = ParseNodeKind::CodeBlock(),
                  .children =
                      {{.kind = ParseNodeKind::CodeBlock(),
                        .children =
                            {{.kind = ParseNodeKind::CodeBlock(),
                              .children = {{.kind = ParseNodeKind::CodeBlock(),
                                            .children = {{ParseNodeKind::
                                                              CodeBlockEnd()}}},
                                           {ParseNodeKind::CodeBlockEnd()}}},
                             {ParseNodeKind::CodeBlockEnd()}}},
                       {ParseNodeKind::CodeBlockEnd()}}}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDefinitionWithIdenifierInStatements) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn F() {\n"
      "  bar\n"
      "}");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  // Note: this might become valid depending on the expression syntax. This test
  // shouldn't be taken as a sign it should remain invalid.
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(),
            .children = {{ParseNodeKind::Identifier(), "F"},
                         {.kind = ParseNodeKind::ParameterList(),
                          .children = {{ParseNodeKind::ParameterListEnd()}}},
                         {.kind = ParseNodeKind::CodeBlock(),
                          .has_error = true,
                          .children = {{ParseNodeKind::CodeBlockEnd()}}}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

TEST_F(ParseTreeTest, FunctionDefinitionWithIdenifierInNestedBlock) {
  TokenizedBuffer tokens = GetTokenizedBuffer(
      "fn F() {\n"
      "  {bar}\n"
      "}");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  // Note: this might become valid depending on the expression syntax. This test
  // shouldn't be taken as a sign it should remain invalid.
  EXPECT_TRUE(tree.HasErrors());
  EXPECT_THAT(
      tree,
      MatchParseTreeNodes(
          {{.kind = ParseNodeKind::FunctionDeclaration(),
            .children =
                {{ParseNodeKind::Identifier(), "F"},
                 {.kind = ParseNodeKind::ParameterList(),
                  .children = {{ParseNodeKind::ParameterListEnd()}}},
                 {.kind = ParseNodeKind::CodeBlock(),
                  .children = {{.kind = ParseNodeKind::CodeBlock(),
                                .has_error = true,
                                .children = {{ParseNodeKind::CodeBlockEnd()}}},
                               {ParseNodeKind::CodeBlockEnd()}}}}},
           {.kind = ParseNodeKind::FileEnd()}}));
}

auto GetAndDropLine(llvm::StringRef& s) -> std::string {
  auto newline_offset = s.find_first_of('\n');
  llvm::StringRef line = s.slice(0, newline_offset);

  if (newline_offset != llvm::StringRef::npos) {
    s = s.substr(newline_offset + 1);
  } else {
    s = "";
  }

  return line.str();
}

TEST_F(ParseTreeTest, Printing) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  std::string print_storage;
  llvm::raw_string_ostream print_stream(print_storage);
  tree.Print(print_stream);
  llvm::StringRef print = print_stream.str();
  EXPECT_THAT(GetAndDropLine(print), StrEq("["));
  EXPECT_THAT(GetAndDropLine(print),
              StrEq("{node_index: 4, kind: 'FunctionDeclaration', text: 'fn', "
                    "subtree_size: 5, children: ["));
  EXPECT_THAT(GetAndDropLine(print),
              StrEq("  {node_index: 0, kind: 'Identifier', text: 'F'},"));
  EXPECT_THAT(GetAndDropLine(print),
              StrEq("  {node_index: 2, kind: 'ParameterList', text: '(', "
                    "subtree_size: 2, children: ["));
  EXPECT_THAT(GetAndDropLine(print),
              StrEq("    {node_index: 1, kind: 'ParameterListEnd', "
                    "text: ')'}]},"));
  EXPECT_THAT(GetAndDropLine(print),
              StrEq("  {node_index: 3, kind: 'DeclarationEnd', text: ';'}]},"));
  EXPECT_THAT(GetAndDropLine(print),
              StrEq("{node_index: 5, kind: 'FileEnd', text: ''},"));
  EXPECT_THAT(GetAndDropLine(print), StrEq("]"));
  EXPECT_TRUE(print.empty()) << print;
}

TEST_F(ParseTreeTest, PrintingAsYAML) {
  TokenizedBuffer tokens = GetTokenizedBuffer("fn F();");
  ParseTree tree = ParseTree::Parse(tokens, consumer);
  EXPECT_FALSE(tree.HasErrors());
  std::string print_output;
  llvm::raw_string_ostream print_stream(print_output);
  tree.Print(print_stream);
  print_stream.flush();

  // Parse the output into a YAML stream. This will print errors to stderr.
  llvm::SourceMgr source_manager;
  llvm::yaml::Stream yaml_stream(print_output, source_manager);
  auto di = yaml_stream.begin();
  auto* root_node = llvm::dyn_cast<llvm::yaml::SequenceNode>(di->getRoot());
  ASSERT_THAT(root_node, NotNull());

  // The root node is just an array of top-level parse nodes.
  auto ni = root_node->begin();
  auto ne = root_node->end();
  auto* node = llvm::dyn_cast<llvm::yaml::MappingNode>(&*ni);
  ASSERT_THAT(node, NotNull());
  auto nkvi = node->begin();
  auto nkve = node->end();
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("node_index", "4"));
  ++nkvi;
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("kind", "FunctionDeclaration"));
  ++nkvi;
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("text", "fn"));
  ++nkvi;
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("subtree_size", "5"));
  ++nkvi;
  auto* children_node = llvm::dyn_cast<llvm::yaml::KeyValueNode>(&*nkvi);
  ASSERT_THAT(children_node, NotNull());
  auto* children_key_node =
      llvm::dyn_cast<llvm::yaml::ScalarNode>(children_node->getKey());
  ASSERT_THAT(children_key_node, NotNull());
  EXPECT_THAT(children_key_node->getRawValue(), StrEq("children"));
  auto* children_value_node =
      llvm::dyn_cast<llvm::yaml::SequenceNode>(children_node->getValue());
  ASSERT_THAT(children_value_node, NotNull());

  auto ci = children_value_node->begin();
  auto ce = children_value_node->end();
  ASSERT_THAT(ci, Ne(ce));
  node = llvm::dyn_cast<llvm::yaml::MappingNode>(&*ci);
  ASSERT_THAT(node, NotNull());
  auto ckvi = node->begin();
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("node_index", "0"));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("kind", "Identifier"));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("text", "F"));
  ++ckvi;
  EXPECT_THAT(ckvi, Eq(node->end()));

  ++ci;
  ASSERT_THAT(ci, Ne(ce));
  node = llvm::dyn_cast<llvm::yaml::MappingNode>(&*ci);
  ASSERT_THAT(node, NotNull());
  ckvi = node->begin();
  auto ckve = node->end();
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("node_index", "2"));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("kind", "ParameterList"));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("text", "("));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("subtree_size", "2"));
  ++ckvi;
  children_node = llvm::dyn_cast<llvm::yaml::KeyValueNode>(&*ckvi);
  ASSERT_THAT(children_node, NotNull());
  children_key_node =
      llvm::dyn_cast<llvm::yaml::ScalarNode>(children_node->getKey());
  ASSERT_THAT(children_key_node, NotNull());
  EXPECT_THAT(children_key_node->getRawValue(), StrEq("children"));
  children_value_node =
      llvm::dyn_cast<llvm::yaml::SequenceNode>(children_node->getValue());
  ASSERT_THAT(children_value_node, NotNull());

  auto c2_i = children_value_node->begin();
  auto c2_e = children_value_node->end();
  ASSERT_THAT(c2_i, Ne(c2_e));
  node = llvm::dyn_cast<llvm::yaml::MappingNode>(&*c2_i);
  ASSERT_THAT(node, NotNull());
  auto c2_kvi = node->begin();
  EXPECT_THAT(&*c2_kvi, IsKeyValueScalars("node_index", "1"));
  ++c2_kvi;
  EXPECT_THAT(&*c2_kvi, IsKeyValueScalars("kind", "ParameterListEnd"));
  ++c2_kvi;
  EXPECT_THAT(&*c2_kvi, IsKeyValueScalars("text", ")"));
  ++c2_kvi;
  EXPECT_THAT(c2_kvi, Eq(node->end()));
  ++c2_i;
  EXPECT_THAT(c2_i, Eq(c2_e));
  ++ckvi;
  EXPECT_THAT(ckvi, Eq(ckve));

  ++ci;
  ASSERT_THAT(ci, Ne(ce));
  node = llvm::dyn_cast<llvm::yaml::MappingNode>(&*ci);
  ASSERT_THAT(node, NotNull());
  ckvi = node->begin();
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("node_index", "3"));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("kind", "DeclarationEnd"));
  ++ckvi;
  EXPECT_THAT(&*ckvi, IsKeyValueScalars("text", ";"));
  ++ckvi;
  EXPECT_THAT(ckvi, Eq(node->end()));
  ++ci;
  EXPECT_THAT(ci, Eq(ce));

  ++nkvi;
  EXPECT_THAT(nkvi, Eq(nkve));

  ++ni;
  ASSERT_THAT(ni, Ne(ne));
  node = llvm::dyn_cast<llvm::yaml::MappingNode>(&*ni);
  ASSERT_THAT(node, NotNull());
  nkvi = node->begin();
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("node_index", "5"));
  ++nkvi;
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("kind", "FileEnd"));
  ++nkvi;
  EXPECT_THAT(&*nkvi, IsKeyValueScalars("text", ""));
  ++nkvi;
  EXPECT_THAT(nkvi, Eq(node->end()));

  ++ni;
  EXPECT_THAT(ni, Eq(ne));
  ++di;
  EXPECT_THAT(di, Eq(yaml_stream.end()));
}

}  // namespace
}  // namespace Carbon