bolt/src/Parser.cc

#include "bolt/CST.hpp"
#include "bolt/Scanner.hpp"
#include "bolt/Parser.hpp"
#include "bolt/Diagnostics.hpp" 
#include <vector>

namespace bolt {

  std::optional<OperatorInfo> OperatorTable::getInfix(Token* T) {
    auto Match = Mapping.find(T->getText());
    if (Match == Mapping.end() || !Match->second.isInfix()) {
      return {};
    }
    return Match->second;
  }

  bool OperatorTable::isInfix(Token* T) {
    auto Match = Mapping.find(T->getText());
    return Match != Mapping.end() && Match->second.isInfix();
  }

  bool OperatorTable::isPrefix(Token* T) {
    auto Match = Mapping.find(T->getText());
    return Match != Mapping.end() && Match->second.isPrefix();
  }

  bool OperatorTable::isSuffix(Token* T) {
    auto Match = Mapping.find(T->getText());
    return Match != Mapping.end() && Match->second.isSuffix();
  }

  void OperatorTable::add(std::string Name, unsigned Flags, int Precedence) { 
    Mapping.emplace(Name, OperatorInfo { Precedence, Flags });
  }

  Parser::Parser(TextFile& File, Stream<Token*>& S):
    File(File), Tokens(S) {
      ExprOperators.add("**", OperatorFlags_InfixR, 10);
      ExprOperators.add("*", OperatorFlags_InfixL, 5);
      ExprOperators.add("/", OperatorFlags_InfixL, 5);
      ExprOperators.add("+", OperatorFlags_InfixL, 4);
      ExprOperators.add("-", OperatorFlags_InfixL, 4);
      ExprOperators.add("<", OperatorFlags_InfixL, 3);
      ExprOperators.add(">", OperatorFlags_InfixL, 3);
      ExprOperators.add("<=", OperatorFlags_InfixL, 3);
      ExprOperators.add(">=", OperatorFlags_InfixL, 3);
      ExprOperators.add("==", OperatorFlags_InfixL, 3);
      ExprOperators.add("!=", OperatorFlags_InfixL, 3);
      ExprOperators.add(":", OperatorFlags_InfixL, 2);
      ExprOperators.add("<|>", OperatorFlags_InfixL, 1);
      ExprOperators.add("$", OperatorFlags_InfixR, 0);
    }

  Token* Parser::peekFirstTokenAfterModifiers() {
    std::size_t I = 0;
    for (;;) {
      auto T0 = Tokens.peek(I++);
      switch (T0->Type) {
        case NodeType::PubKeyword:
        case NodeType::MutKeyword:
          continue;
        default:
          return T0;
      }
    }
  }

#define BOLT_EXPECT_TOKEN(name) \
  { \
    auto __Token = Tokens.get(); \
    if (__Token->Type != NodeType::name) { \
      throw UnexpectedTokenDiagnostic(__Token, std::vector<NodeType> { NodeType::name }); \
    } \
  }

  Pattern* Parser::parsePattern() {
    auto T0 = Tokens.peek();
    switch (T0->Type) {
      case NodeType::Identifier:
        Tokens.get();
        return new BindPattern(static_cast<Identifier*>(T0));
      default:
        throw UnexpectedTokenDiagnostic(T0, std::vector { NodeType::Identifier });
    }
  }

  QualifiedName* Parser::parseQualifiedName() {
    std::vector<Identifier*> ModulePath;
    auto Name = Tokens.get();
    if (Name->Type != NodeType::Identifier) {
      throw UnexpectedTokenDiagnostic(Name, std::vector { NodeType::Identifier });
    }
    for (;;) {
      auto T1 = Tokens.peek();
      if (T1->Type == NodeType::Dot) {
        break;
      }
      Tokens.get();
      ModulePath.push_back(static_cast<Identifier*>(Name));
      Name = Tokens.get();
      if (Name->Type != NodeType::Identifier) {
        throw UnexpectedTokenDiagnostic(Name, std::vector { NodeType::Identifier });
      }
    }
    return new QualifiedName(ModulePath, static_cast<Identifier*>(Name));
  }

  TypeExpression* Parser::parseTypeExpression() {
    auto T0 = Tokens.peek();
    switch (T0->Type) {
      case NodeType::Identifier:
        return new ReferenceTypeExpression(parseQualifiedName());
      default:
        throw UnexpectedTokenDiagnostic(T0, std::vector { NodeType::Identifier });
    }
  }

  Expression* Parser::parsePrimitiveExpression() {
    auto T0 = Tokens.peek();
    switch (T0->Type) {
      case NodeType::Identifier:
      {
        auto Name = parseQualifiedName();
        return new ReferenceExpression(Name);
      }
      case NodeType::IntegerLiteral:
      case NodeType::StringLiteral:
        Tokens.get();
        return new ConstantExpression(T0);
      default:
        throw UnexpectedTokenDiagnostic(T0, std::vector { NodeType::Identifier, NodeType::IntegerLiteral });
    }
  }

  Expression* Parser::parseCallExpression() {
    auto Operator = parsePrimitiveExpression();
    std::vector<Expression*> Args;
    for (;;) {
      auto T1 = Tokens.peek();
      if (T1->Type == NodeType::LineFoldEnd || ExprOperators.isInfix(T1)) {
        break;
      }
      Args.push_back(parsePrimitiveExpression());
    }
    if (Args.empty()) {
      return Operator;
    }
    return new CallExpression(Operator, Args);
  }

  Expression* Parser::parseUnaryExpression() {
    std::vector<Token*> Prefix;
    for (;;) {
      auto T0 = Tokens.peek();
      if (!ExprOperators.isPrefix(T0)) {
        break;
      }
      Tokens.get();
      Prefix.push_back(T0);
    }
    auto E = parseCallExpression();
    for (auto Iter = Prefix.rbegin(); Iter != Prefix.rend(); Iter++) {
      E = new UnaryExpression(*Iter, E);
    }
    return E;
  }

  Expression* Parser::parseInfixOperatorAfterExpression(Expression* LHS, int MinPrecedence) {
    for (;;) {
      auto T0 = Tokens.peek();
      auto Info0 = ExprOperators.getInfix(T0);
      if (!Info0 || Info0->Precedence < MinPrecedence) {
        break;
      }
      Tokens.get();
      auto RHS = parseUnaryExpression();
      for (;;) {
        auto T1 = Tokens.peek();
        auto Info1 = ExprOperators.getInfix(T1);
        if (!Info1 || Info1->Precedence < Info0->Precedence && (Info1->Precedence > Info0->Precedence || Info1->isRightAssoc())) {
          break;
        }
        RHS = parseInfixOperatorAfterExpression(RHS, Info1->Precedence);
      }
      LHS = new InfixExpression(LHS, T0, RHS);
    }
    return LHS;
  }

  Expression* Parser::parseExpression() {
    return parseInfixOperatorAfterExpression(parseUnaryExpression(), 0);
  }

  ExpressionStatement* Parser::parseExpressionStatement() {
    auto E = parseExpression();
    BOLT_EXPECT_TOKEN(LineFoldEnd);
    return new ExpressionStatement(E);
  }

  LetDeclaration* Parser::parseLetDeclaration() {

    PubKeyword* Pub;
    LetKeyword* Let;
    MutKeyword* Mut;
    auto T0 = Tokens.get();
    if (T0->Type == NodeType::PubKeyword) {
      Pub = static_cast<PubKeyword*>(T0);
      T0 = Tokens.get();
    }
    if (T0->Type != NodeType::LetKeyword) {
      throw UnexpectedTokenDiagnostic(T0, std::vector { NodeType::LetKeyword });
    }
    Let = static_cast<LetKeyword*>(T0);
    auto T1 = Tokens.peek();
    if (T1->Type == NodeType::MutKeyword) {
      Mut = static_cast<MutKeyword*>(T1);
      Tokens.get();
    }

    auto Patt = parsePattern();

    std::vector<Param*> Params;
    Token* T2;
    for (;;) {
      T2 = Tokens.peek();
      switch (T2->Type) {
        case NodeType::LineFoldEnd:
        case NodeType::BlockStart:
        case NodeType::Equals:
        case NodeType::Colon:
          goto after_params;
        default:
          Params.push_back(new Param(parsePattern(), nullptr));
      }
    }

after_params:

    TypeAssert* TA = nullptr;
    if (T2->Type == NodeType::Colon) {
      Tokens.get();
      auto TE = parseTypeExpression();
      TA = new TypeAssert(static_cast<Colon*>(T2), TE);
      T2 = Tokens.peek();
    }

    LetBody* Body;
    switch (T2->Type) {
      case NodeType::BlockStart:
      {
        Tokens.get();
        std::vector<Node*> Elements;
        for (;;) {
          auto T3 = Tokens.peek();
          if (T3->Type == NodeType::BlockEnd) {
            break;
          }
          Elements.push_back(parseLetBodyElement());
        }
        Tokens.get();
        Body = new LetBlockBody(static_cast<BlockStart*>(T2), Elements);
        break;
      }
      case NodeType::Equals:
        Tokens.get();
        Body = new LetExprBody(static_cast<Equals*>(T2), parseExpression());
        break;
      case NodeType::LineFoldEnd:
        Body = nullptr;
        break;
      default:
        std::vector<NodeType> Expected { NodeType::BlockStart, NodeType::LineFoldEnd, NodeType::Equals };
        if (TA == nullptr) {
          // First tokens of TypeAssert
          Expected.push_back(NodeType::Colon);
          // First tokens of Pattern
          Expected.push_back(NodeType::Identifier);
        }
        throw UnexpectedTokenDiagnostic(T2, Expected);
    }

    BOLT_EXPECT_TOKEN(LineFoldEnd);

    return new LetDeclaration(
      Pub,
      Let,
      Mut,
      Patt,
      Params,
      TA,
      Body
    );
  }

  Node* Parser::parseLetBodyElement() {
    auto T0 = peekFirstTokenAfterModifiers();
    switch (T0->Type) {
      case NodeType::LetKeyword:
        return parseLetDeclaration();
      default:
        return parseExpressionStatement();
    }
  }

  Node* Parser::parseSourceElement() {
    auto T0 = peekFirstTokenAfterModifiers();
    switch (T0->Type) {
      case NodeType::LetKeyword:
        return parseLetDeclaration();
      default:
        return parseExpressionStatement();
    }
  }

  SourceFile* Parser::parseSourceFile() {
    std::vector<Node*> Elements;
    for (;;) {
      auto T0 = Tokens.peek();
      if (T0->Type == NodeType::EndOfFile) {
        break;
      }
      Elements.push_back(parseSourceElement());
    }
    return new SourceFile(File, Elements);
  }

}