type checking

bootstrap/error.cc

@@ -1,8 +1,16 @@
 #include <error.hh>
+#include <exception>
 #include <iostream>
 
 namespace xlang {
 
+void ErrorListener::printError(size_t line, size_t charPositionInLine,
+                               std::string_view msg) {
+  std::cerr << file << ":" << line << ":" << charPositionInLine + 1 << ": "
+            << msg << std::endl;
+  has_error = true;
+}
+
 ErrorListener::ErrorListener(std::string_view inputfile)
     : file{inputfile}, has_error{false} {}
 
@@ -10,21 +18,57 @@ bool ErrorListener::hasError() {
   return has_error;
 }
 
+void ErrorListener::compilerError(const std::string &file, size_t line) {
+  std::cerr << "compiler bug in " << file << ":" << line << std::endl;
+  std::terminate();
+}
+
+void ErrorListener::duplicateFunction(antlr4::Token *token,
+                                      const std::string &name) {
+  printError(token->getLine(), token->getCharPositionInLine(),
+             "duplicate function '" + name + "'");
+}
+
+void ErrorListener::shadowedVariable(antlr4::Token *token,
+                                     const std::string &name) {
+  printError(token->getLine(), token->getCharPositionInLine(),
+             "definition of variable '" + name +
+                 "' shadows previously defined variable");
+}
+
 void ErrorListener::syntaxError([[maybe_unused]] antlr4::Recognizer *recognizer,
                                 [[maybe_unused]] antlr4::Token *offendingSymbol,
                                 size_t line, size_t charPositionInLine,
                                 const std::string &msg,
                                 [[maybe_unused]] std::exception_ptr e) {
-  std::cerr << file << ":" << line << ":" << charPositionInLine + 1 << ": "
+  printError(line, charPositionInLine, msg);
-            << msg << std::endl;
-  has_error = true;
 }
 
-void ErrorListener::typeError(size_t line, size_t charPositionInLine,
+void ErrorListener::typeMismatch(antlr4::Token *token, Type expected,
-                              std::string_view msg) {
+                                 Type actual) {
-  std::cerr << file << ":" << line << ":" << charPositionInLine + 1 << ": "
+  printError(token->getLine(), token->getCharPositionInLine(),
-            << msg << std::endl;
+             "expected type '" + typeToString(expected) + "', but got '" +
-  has_error = true;
+                 typeToString(actual) + "'");
+}
+
+void ErrorListener::unknownFunction(antlr4::Token *token,
+                                    const std::string &name) {
+  printError(token->getLine(), token->getCharPositionInLine(),
+             "unknown function '" + name + "'");
+}
+
+void ErrorListener::unknownVariable(antlr4::Token *token,
+                                    const std::string &name) {
+  printError(token->getLine(), token->getCharPositionInLine(),
+             "unknown variable '" + name + "'");
+}
+
+void ErrorListener::wrongArgumentNumber(antlr4::Token *token,
+                                        const std::string &name,
+                                        size_t expected, size_t actual) {
+  printError(token->getLine(), token->getCharPositionInLine(),
+             "function '" + name + "' expects " + std::to_string(expected) +
+                 " arguments, but got " + std::to_string(actual));
 }
 
 }  // namespace xlang

bootstrap/error.hh

@@ -2,6 +2,7 @@
 
 #include <BaseErrorListener.h>
 #include <string_view>
+#include <typecheck.hh>
 
 namespace xlang {
 
@@ -9,15 +10,25 @@ class ErrorListener : public antlr4::BaseErrorListener {
   std::string_view file;
   bool has_error;
 
+  void printError(size_t line, size_t charPositionInLine, std::string_view msg);
+
  public:
   ErrorListener(std::string_view inputfile);
 
   bool hasError();
+
+  void compilerError(const std::string &file, size_t line);
+  void duplicateFunction(antlr4::Token *token, const std::string &name);
+  void shadowedVariable(antlr4::Token *token, const std::string &name);
   void syntaxError(antlr4::Recognizer *recognizer,
                    antlr4::Token *offendingSymbol, size_t line,
                    size_t charPositionInLine, const std::string &msg,
                    std::exception_ptr e) override;
-  void typeError(size_t line, size_t charPositionInLine, std::string_view msg);
+  void typeMismatch(antlr4::Token *token, Type expected, Type actual);
+  void unknownFunction(antlr4::Token *token, const std::string &name);
+  void unknownVariable(antlr4::Token *token, const std::string &name);
+  void wrongArgumentNumber(antlr4::Token *token, const std::string &name,
+                           size_t expected, size_t actual);
 };
 
 }  // namespace xlang

bootstrap/scope.hh

@@ -0,0 +1,42 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+namespace xlang {
+
+template <typename T>
+class Scope {
+  std::vector<std::unordered_map<std::string, T>> stack;
+
+ public:
+  void enter() {
+    stack.emplace_back();
+  }
+
+  void leave() {
+    stack.pop_back();
+  }
+
+  void add(const std::string &name, T v) {
+    stack.back().emplace(name, v);
+  }
+
+  std::optional<T> get(const std::string &name) {
+    for (auto scope = stack.end() - 1;; scope--) {
+      auto it = scope->find(name);
+
+      if (it != scope->end()) {
+        return it->second;
+      }
+      if (scope == stack.begin()) {
+        break;
+      }
+    }
+    return {};
+  }
+};
+
+}  // namespace xlang

bootstrap/typecheck.cc

@@ -1,17 +1,16 @@
+#include <error.hh>
 #include <typecheck.hh>
 
 namespace xlang {
 
-bool TypeCheckVisitor::inScope(const std::string &name) {
+std::string typeToString(Type type) {
-  for (auto it = scope.end() - 1;; it--) {
+  switch (type) {
-    if (it->find(name) != it->end()) {
+    case Type::Integer:
-      return true;
+      return "int";
-    }
+    case Type::Boolean:
-    if (it == scope.begin()) {
+      return "bool";
-      break;
-    }
   }
-  return false;
+  return "<invalid>";
 }
 
 TypeCheckVisitor::TypeCheckVisitor(ErrorListener &errorlistener)
@@ -21,91 +20,243 @@ std::any TypeCheckVisitor::visitFile(xlangParser::FileContext *ctx) {
   for (auto function : ctx->function()) {
     auto token = function->Identifier()->getSymbol();
     auto name = token->getText();
+    Signature signature{std::any_cast<Type>(visitType(function->type())), {}};
 
-    if (function_arity.find(name) != function_arity.end()) {
+    if (signatures.find(name) != signatures.end()) {
-      errorlistener.typeError(token->getLine(), token->getCharPositionInLine(),
+      errorlistener.duplicateFunction(token, name);
-                              "duplicate function '" + name + "'");
       continue;
     }
     if (auto param_list = function->parameterList()) {
-      function_arity[name] = param_list->Identifier().size();
+      for (auto type : param_list->type()) {
-    } else {
+        signature.parametertypes.push_back(
-      function_arity[name] = 0;
+            std::any_cast<Type>(visitType(type)));
+      }
     }
+    signatures.emplace(name, signature);
   }
   visitChildren(ctx);
   return {};
 }
 
 std::any TypeCheckVisitor::visitFunction(xlangParser::FunctionContext *ctx) {
-  scope.emplace_back();
+  scope.enter();
   if (auto param_list = ctx->parameterList()) {
-    for (const auto param : param_list->Identifier()) {
+    for (size_t i = 0, n = param_list->Identifier().size(); i < n; i++) {
-      scope.back().emplace(param->getSymbol()->getText());
+      auto name = param_list->Identifier(i)->getSymbol()->getText();
+      auto type = std::any_cast<Type>(visitType(param_list->type(i)));
+
+      scope.add(name, type);
     }
   }
+  returntype = std::any_cast<Type>(visitType(ctx->type()));
   visitBlock(ctx->block());
-  scope.pop_back();
+  scope.leave();
+  return {};
+}
+
+std::any TypeCheckVisitor::visitType(xlangParser::TypeContext *ctx) {
+  if (ctx->TypeInteger()) {
+    return Type::Integer;
+  }
+  if (ctx->TypeBoolean()) {
+    return Type::Boolean;
+  }
+  // unreachable
+  errorlistener.compilerError(__FILE__, __LINE__);
   return {};
 }
 
 std::any TypeCheckVisitor::visitBlock(xlangParser::BlockContext *ctx) {
-  scope.emplace_back();
+  scope.enter();
   visitChildren(ctx);
-  scope.pop_back();
+  scope.leave();
   return {};
 }
 
 std::any TypeCheckVisitor::visitStatement(xlangParser::StatementContext *ctx) {
   if (auto identifier = ctx->Identifier()) {
-    visitValue(ctx->value());
+    auto name = identifier->getSymbol()->getText();
-    scope.back().emplace(identifier->getSymbol()->getText());
+    auto type = std::any_cast<Type>(visitValue(ctx->value()));
+
+    if (ctx->Define()) {
+      if (scope.get(name)) {
+        errorlistener.shadowedVariable(identifier->getSymbol(), name);
+      }
+      scope.add(name, type);
+      return {};
+    }
+    if (ctx->Assign()) {
+      if (auto expected = scope.get(name)) {
+        if (type != *expected) {
+          errorlistener.typeMismatch(identifier->getSymbol(), *expected, type);
+        }
+      } else {
+        errorlistener.unknownVariable(identifier->getSymbol(), name);
+      }
+      return {};
+    }
+    // unreachable
+    errorlistener.compilerError(__FILE__, __LINE__);
     return {};
   }
+  if (auto condition = ctx->condition()) {
+    auto type = std::any_cast<Type>(visitCondition(condition));
+
+    if (type != Type::Boolean) {
+      errorlistener.typeMismatch(condition->getStart(), Type::Boolean, type);
+    }
+    visitBlock(ctx->block(0));
+    if (ctx->Else()) {
+      visitBlock(ctx->block(1));
+    }
+    return {};
+  }
+  if (ctx->Return()) {
+    auto type = std::any_cast<Type>(visitValue(ctx->value()));
+
+    if (type != returntype) {
+      errorlistener.typeMismatch(ctx->value()->getStart(), returntype, type);
+    }
+  }
   visitChildren(ctx);
   return {};
 }
 
+std::any TypeCheckVisitor::visitValue(xlangParser::ValueContext *ctx) {
+  if (auto expr = ctx->expr()) {
+    return visitExpr(expr);
+  }
+  if (auto condition = ctx->condition()) {
+    return visitCondition(condition);
+  }
+  // unreachable
+  errorlistener.compilerError(__FILE__, __LINE__);
+  return {};
+}
+
+#define CHECKOPERATOR(visitLeft, left, visitRight, right, expected)     \
+  auto lefttype = std::any_cast<Type>(visitLeft(left));                 \
+  auto righttype = std::any_cast<Type>(visitRight(right));              \
+                                                                        \
+  if (lefttype != expected) {                                           \
+    errorlistener.typeMismatch(left->getStart(), expected, lefttype);   \
+  }                                                                     \
+  if (righttype != expected) {                                          \
+    errorlistener.typeMismatch(right->getStart(), expected, righttype); \
+  }
+
+std::any TypeCheckVisitor::visitCondition(xlangParser::ConditionContext *ctx) {
+  if (auto condition = ctx->condition()) {
+    CHECKOPERATOR(visitCondition, condition, visitBoolean, ctx->boolean(),
+                  Type::Boolean);
+    return Type::Boolean;
+  }
+  return visitBoolean(ctx->boolean());
+}
+
+std::any TypeCheckVisitor::visitBoolean(xlangParser::BooleanContext *ctx) {
+  if (auto boolean = ctx->boolean()) {
+    auto type = std::any_cast<Type>(visitBoolean(boolean));
+
+    if (type != Type::Boolean) {
+      errorlistener.typeMismatch(boolean->getStart(), Type::Boolean, type);
+    }
+    return Type::Boolean;
+  }
+  if (ctx->True() || ctx->False()) {
+    return Type::Boolean;
+  }
+  if (ctx->expr().size()) {
+    CHECKOPERATOR(visitExpr, ctx->expr(0), visitExpr, ctx->expr(1),
+                  Type::Integer);
+    return Type::Boolean;
+  }
+  if (auto variable = ctx->variable()) {
+    return visitVariable(variable);
+  }
+  return visitCondition(ctx->condition());
+}
+
+std::any TypeCheckVisitor::visitExpr(xlangParser::ExprContext *ctx) {
+  if (auto expr = ctx->expr()) {
+    CHECKOPERATOR(visitExpr, expr, visitTerm, ctx->term(), Type::Integer);
+    return Type::Integer;
+  }
+  return visitTerm(ctx->term());
+}
+
+std::any TypeCheckVisitor::visitTerm(xlangParser::TermContext *ctx) {
+  if (auto term = ctx->term()) {
+    CHECKOPERATOR(visitTerm, term, visitFactor, ctx->factor(), Type::Integer);
+    return Type::Integer;
+  }
+  return visitFactor(ctx->factor());
+}
+
+std::any TypeCheckVisitor::visitFactor(xlangParser::FactorContext *ctx) {
+  if (auto factor = ctx->factor()) {
+    auto type = std::any_cast<Type>(visitFactor(factor));
+
+    if (type != Type::Integer) {
+      errorlistener.typeMismatch(factor->getStart(), Type::Integer, type);
+    }
+    return Type::Integer;
+  }
+  if (ctx->Integer()) {
+    return Type::Integer;
+  }
+  if (auto variable = ctx->variable()) {
+    return visitVariable(variable);
+  }
+  return visitExpr(ctx->expr());
+}
+
 std::any TypeCheckVisitor::visitVariable(xlangParser::VariableContext *ctx) {
   auto token = ctx->Identifier()->getSymbol();
   auto name = token->getText();
-  auto line = token->getLine();
-  auto charPositionInLine = token->getCharPositionInLine();
 
   if (ctx->LeftParen()) {
-    auto it = function_arity.find(name);
+    auto it = signatures.find(name);
 
-    if (it == function_arity.end()) {
+    if (it == signatures.end()) {
-      errorlistener.typeError(line, charPositionInLine,
+      errorlistener.unknownFunction(token, name);
-                              "unknown function '" + name + "'");
+      return Type::Integer;
     } else {
-      auto arity = it->second;
+      auto signature = it->second;
+      auto arity = signature.parametertypes.size();
 
       if (auto arg_list = ctx->argumentList()) {
         auto arg_num = arg_list->value().size();
 
         if (arity != arg_num) {
-          errorlistener.typeError(
+          errorlistener.wrongArgumentNumber(token, name, arity, arg_num);
-              line, charPositionInLine,
+        }
-              "function '" + name + "' expects " + std::to_string(arity) +
+        for (size_t i = 0; i < arg_num && i < arity; i++) {
-                  " arguments, but got " + std::to_string(arg_num));
+          auto type = std::any_cast<Type>(visitValue(arg_list->value(i)));
+          auto token = arg_list->value(i)->getStart();
+
+          if (type != signature.parametertypes[i]) {
+            errorlistener.typeMismatch(token, signature.parametertypes[i],
+                                       type);
+          }
         }
       } else {
         if (arity) {
-          errorlistener.typeError(line, charPositionInLine,
+          errorlistener.wrongArgumentNumber(token, name, arity, 0);
-                                  "function '" + name + "' expects " +
-                                      std::to_string(arity) +
-                                      " arguments, but got none");
         }
       }
+      return signature.returntype;
     }
-    visitChildren(ctx);
   } else {
-    if (!inScope(name)) {
+    auto type = scope.get(name);
-      errorlistener.typeError(line, charPositionInLine,
+    if (!type) {
-                              "variable '" + name + "' is not in scope");
+      errorlistener.unknownVariable(token, name);
+      return Type::Integer;
     }
+    return *type;
   }
+  // unreachable
+  errorlistener.compilerError(__FILE__, __LINE__);
   return {};
 }
 

bootstrap/typecheck.hh

@@ -1,28 +1,48 @@
 #pragma once
 
-#include <error.hh>
+#include <scope.hh>
 #include <string>
 #include <unordered_map>
-#include <unordered_set>
 #include <vector>
 #include <xlangBaseVisitor.h>
 
 namespace xlang {
 
-class TypeCheckVisitor : public xlangBaseVisitor {
+class ErrorListener;
-  ErrorListener &errorlistener;
-  std::unordered_map<std::string, unsigned int> function_arity;
-  std::vector<std::unordered_set<std::string>> scope;
 
-  bool inScope(const std::string &name);
+enum class Type
+{
+  Integer,
+  Boolean,
+};
+
+std::string typeToString(Type type);
+
+class TypeCheckVisitor : public xlangBaseVisitor {
+  struct Signature {
+    Type returntype;
+    std::vector<Type> parametertypes;
+  };
+
+  ErrorListener &errorlistener;
+  std::unordered_map<std::string, Signature> signatures;
+  Type returntype;
+  Scope<Type> scope;
 
  public:
   TypeCheckVisitor(ErrorListener &errorlistener);
 
   std::any visitFile(xlangParser::FileContext *ctx) override;
   std::any visitFunction(xlangParser::FunctionContext *ctx) override;
+  std::any visitType(xlangParser::TypeContext *ctx) override;
   std::any visitBlock(xlangParser::BlockContext *ctx) override;
   std::any visitStatement(xlangParser::StatementContext *ctx) override;
+  std::any visitValue(xlangParser::ValueContext *ctx) override;
+  std::any visitCondition(xlangParser::ConditionContext *ctx) override;
+  std::any visitBoolean(xlangParser::BooleanContext *ctx) override;
+  std::any visitExpr(xlangParser::ExprContext *ctx) override;
+  std::any visitTerm(xlangParser::TermContext *ctx) override;
+  std::any visitFactor(xlangParser::FactorContext *ctx) override;
   std::any visitVariable(xlangParser::VariableContext *ctx) override;
 };
 

bootstrap/xlang.g4

@@ -1,10 +1,14 @@
 grammar xlang;
 
 file  : function+ EOF;
-function  : Identifier LeftParen parameterList? RightParen block;
+function  : Identifier LeftParen parameterList? RightParen Colon type block;
-parameterList  : Identifier (Comma Identifier)*;
+parameterList  : Identifier Colon type (Comma Identifier Colon type)*;
+type  : TypeInteger
+      | TypeBoolean
+      ;
 block : LeftBrace statement* RightBrace;
-statement : Identifier Assign value Semicolon
+statement : Identifier Define value Semicolon
+          | Identifier Assign value Semicolon
           | If condition block (Else block)?
           | While condition block
           | Return value Semicolon
@@ -40,6 +44,8 @@ variable  : Identifier
           ;
 argumentList  : value (Comma value)*;
 
+TypeInteger : 'int';
+TypeBoolean : 'bool';
 If  : 'if';
 Else  : 'else';
 While : 'while';
@@ -54,8 +60,10 @@ False : 'false';
 
 LeftParen : '(';
 RightParen  : ')';
+Colon : ':';
 LeftBrace : '{';
 RightBrace  : '}';
+Define  : ':=';
 Assign  : '=';
 Less  : '<';
 LessEqual : '<=';

test/42.x

@@ -1,3 +1,3 @@
-main() {
+main() : int {
   print 42;
 }

test/fib.x

@@ -1,5 +1,5 @@
-main() {
+main() : int {
-  i = 0;
+  i := 0;
   while i < 10 {
     print fib_rec(i);
     print fib_iter(i);
@@ -7,19 +7,19 @@ main() {
   }
 }
 
-fib_rec(n) {
+fib_rec(n : int) : int {
   if n < 2 {
     return 1;
   }
   return fib_rec(n - 1) + fib_rec(n - 2);
 }
 
-fib_iter(n) {
+fib_iter(n : int) : int {
-  x0 = 1;
+  x0 := 1;
-  x1 = 1;
+  x1 := 1;
-  i = 0;
+  i := 0;
   while i < n {
-    t = x0 + x1;
+    t := x0 + x1;
     x0 = x1;
     x1 = t;
     i = i + 1;