carbon-lang/toolchain/parser/precedence_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 "toolchain/parser/precedence.h"

#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "toolchain/lexer/token_kind.h"

namespace Carbon {
namespace {

using ::testing::Eq;

TEST(PrecedenceTest, OperatorsAreRecognized) {
  EXPECT_TRUE(PrecedenceGroup::ForLeading(TokenKind::Minus()).hasValue());
  EXPECT_TRUE(PrecedenceGroup::ForLeading(TokenKind::Tilde()).hasValue());
  EXPECT_FALSE(PrecedenceGroup::ForLeading(TokenKind::Slash()).hasValue());
  EXPECT_FALSE(PrecedenceGroup::ForLeading(TokenKind::Identifier()).hasValue());

  EXPECT_TRUE(
      PrecedenceGroup::ForTrailing(TokenKind::Minus(), false).hasValue());
  EXPECT_FALSE(
      PrecedenceGroup::ForTrailing(TokenKind::Tilde(), false).hasValue());
  EXPECT_TRUE(
      PrecedenceGroup::ForTrailing(TokenKind::Slash(), true).hasValue());
  EXPECT_FALSE(
      PrecedenceGroup::ForTrailing(TokenKind::Identifier(), false).hasValue());

  EXPECT_TRUE(
      PrecedenceGroup::ForTrailing(TokenKind::Minus(), true)->is_binary);
  EXPECT_FALSE(
      PrecedenceGroup::ForTrailing(TokenKind::MinusMinus(), false)->is_binary);
}

TEST(PrecedenceTest, InfixVsPostfix) {
  // A trailing `-` is always infix; a trailing `--` is always postfix.
  EXPECT_TRUE(
      PrecedenceGroup::ForTrailing(TokenKind::Minus(), false)->is_binary);
  EXPECT_FALSE(
      PrecedenceGroup::ForTrailing(TokenKind::MinusMinus(), true)->is_binary);

  // A trailing `*` is interpreted based on context.
  EXPECT_TRUE(PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->is_binary);
  EXPECT_FALSE(
      PrecedenceGroup::ForTrailing(TokenKind::Star(), false)->is_binary);

  // Infix `*` can appear in type contexts; binary `*` cannot.
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->level,
                  PrecedenceGroup::ForType()),
              Eq(OperatorPriority::Ambiguous));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Star(), false)->level,
                  PrecedenceGroup::ForType()),
              Eq(OperatorPriority::LeftFirst));

  // Binary `*` can appear in `+` contexts; binary `*` cannot.
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Plus(), true)->level),
              Eq(OperatorPriority::LeftFirst));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Star(), false)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Plus(), true)->level),
              Eq(OperatorPriority::Ambiguous));
}

TEST(PrecedenceTest, Associativity) {
  EXPECT_THAT(
      PrecedenceGroup::ForLeading(TokenKind::Minus())->GetAssociativity(),
      Eq(Associativity::RightToLeft));
  EXPECT_THAT(PrecedenceGroup::ForTrailing(TokenKind::PlusPlus(), false)
                  ->level.GetAssociativity(),
              Eq(Associativity::LeftToRight));
  EXPECT_THAT(PrecedenceGroup::ForTrailing(TokenKind::Plus(), true)
                  ->level.GetAssociativity(),
              Eq(Associativity::LeftToRight));
  EXPECT_THAT(PrecedenceGroup::ForTrailing(TokenKind::Equal(), true)
                  ->level.GetAssociativity(),
              Eq(Associativity::RightToLeft));
  EXPECT_THAT(PrecedenceGroup::ForTrailing(TokenKind::PlusEqual(), true)
                  ->level.GetAssociativity(),
              Eq(Associativity::None));
}

TEST(PrecedenceTest, DirectRelations) {
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Plus(), true)->level),
              Eq(OperatorPriority::LeftFirst));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Plus(), true)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->level),
              Eq(OperatorPriority::RightFirst));

  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Amp(), true)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Less(), true)->level),
              Eq(OperatorPriority::LeftFirst));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Less(), true)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Amp(), true)->level),
              Eq(OperatorPriority::RightFirst));
}

TEST(PrecedenceTest, IndirectRelations) {
  EXPECT_THAT(
      PrecedenceGroup::GetPriority(
          PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->level,
          PrecedenceGroup::ForTrailing(TokenKind::OrKeyword(), true)->level),
      Eq(OperatorPriority::LeftFirst));
  EXPECT_THAT(
      PrecedenceGroup::GetPriority(
          PrecedenceGroup::ForTrailing(TokenKind::OrKeyword(), true)->level,
          PrecedenceGroup::ForTrailing(TokenKind::Star(), true)->level),
      Eq(OperatorPriority::RightFirst));

  EXPECT_THAT(
      PrecedenceGroup::GetPriority(
          *PrecedenceGroup::ForLeading(TokenKind::Tilde()),
          PrecedenceGroup::ForTrailing(TokenKind::Equal(), true)->level),
      Eq(OperatorPriority::LeftFirst));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Equal(), true)->level,
                  *PrecedenceGroup::ForLeading(TokenKind::Tilde())),
              Eq(OperatorPriority::RightFirst));
}

TEST(PrecedenceTest, IncomparableOperators) {
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  *PrecedenceGroup::ForLeading(TokenKind::Tilde()),
                  *PrecedenceGroup::ForLeading(TokenKind::NotKeyword())),
              Eq(OperatorPriority::Ambiguous));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  *PrecedenceGroup::ForLeading(TokenKind::Tilde()),
                  *PrecedenceGroup::ForLeading(TokenKind::Minus())),
              Eq(OperatorPriority::Ambiguous));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  *PrecedenceGroup::ForLeading(TokenKind::Minus()),
                  PrecedenceGroup::ForTrailing(TokenKind::Amp(), true)->level),
              Eq(OperatorPriority::Ambiguous));
  EXPECT_THAT(
      PrecedenceGroup::GetPriority(
          PrecedenceGroup::ForTrailing(TokenKind::Equal(), true)->level,
          PrecedenceGroup::ForTrailing(TokenKind::PipeEqual(), true)->level),
      Eq(OperatorPriority::Ambiguous));
  EXPECT_THAT(PrecedenceGroup::GetPriority(
                  PrecedenceGroup::ForTrailing(TokenKind::Plus(), true)->level,
                  PrecedenceGroup::ForTrailing(TokenKind::Amp(), true)->level),
              Eq(OperatorPriority::Ambiguous));
}

}  // namespace
}  // namespace Carbon