From fa7278e616940d7c4978592ef9fee96b37986a1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ibrahim=20Numanagic=CC=81?= <ibrahimpasa@gmail.com>
Date: Tue, 28 Dec 2021 20:58:20 -0800
Subject: [PATCH] Support for overloaded functions [wip; base logic done]

---
 codon/parser/cache.cpp                        |   3 +
 codon/parser/cache.h                          |  30 +++--
 codon/parser/peg/peg.cpp                      |   2 -
 .../parser/visitors/simplify/simplify_ctx.cpp |  22 ++--
 codon/parser/visitors/simplify/simplify_ctx.h |   9 +-
 .../visitors/simplify/simplify_stmt.cpp       | 120 +++++++++---------
 codon/parser/visitors/translate/translate.cpp |   3 +-
 codon/parser/visitors/typecheck/typecheck.h   |   2 +
 .../visitors/typecheck/typecheck_ctx.cpp      |  19 +--
 .../visitors/typecheck/typecheck_expr.cpp     |  80 +++++++++---
 .../visitors/typecheck/typecheck_stmt.cpp     |  14 +-
 stdlib/internal/str.codon                     |   1 +
 test/parser/simplify_stmt.codon               |   2 +-
 test/parser/typecheck_expr.codon              |  12 +-
 test/parser/typecheck_stmt.codon              |  12 +-
 test/parser/types.codon                       |  75 ++++++-----
 16 files changed, 241 insertions(+), 165 deletions(-)

diff --git a/codon/parser/cache.cpp b/codon/parser/cache.cpp
index 4d774c1b..e94ca102 100644
--- a/codon/parser/cache.cpp
+++ b/codon/parser/cache.cpp
@@ -50,6 +50,9 @@ types::ClassTypePtr Cache::findClass(const std::string &name) const {
 
 types::FuncTypePtr Cache::findFunction(const std::string &name) const {
   auto f = typeCtx->find(name);
+  if (f && f->type && f->kind == TypecheckItem::Func)
+    return f->type->getFunc();
+  f = typeCtx->find(name + ":0");
   if (f && f->type && f->kind == TypecheckItem::Func)
     return f->type->getFunc();
   return nullptr;
diff --git a/codon/parser/cache.h b/codon/parser/cache.h
index 16db95cc..7adcb4c8 100644
--- a/codon/parser/cache.h
+++ b/codon/parser/cache.h
@@ -106,19 +106,9 @@ struct Cache : public std::enable_shared_from_this<Cache> {
     /// Non-simplified AST. Used for base class instantiation.
     std::shared_ptr<ClassStmt> originalAst;
 
-    /// A class function method.
-    struct ClassMethod {
-      /// Canonical name of a method (e.g. __init__.1).
-      std::string name;
-      /// A corresponding generic function type.
-      types::FuncTypePtr type;
-      /// Method age (how many class extension were seen before a method definition).
-      /// Used to prevent the usage of a method before it was defined in the code.
-      int age;
-    };
-    /// Class method lookup table. Each name points to a list of ClassMethod instances
-    /// that share the same method name (a list because methods can be overloaded).
-    std::unordered_map<std::string, std::vector<ClassMethod>> methods;
+    /// Class method lookup table. Each non-canonical name points
+    /// to a root function name of a corresponding method.
+    std::unordered_map<std::string, std::string> methods;
 
     /// A class field (member).
     struct ClassField {
@@ -177,6 +167,20 @@ struct Cache : public std::enable_shared_from_this<Cache> {
   /// corresponding Function instance.
   std::unordered_map<std::string, Function> functions;
 
+
+  struct Overload {
+    /// Canonical name of an overload (e.g. Foo.__init__.1).
+    std::string name;
+    /// Overload age (how many class extension were seen before a method definition).
+    /// Used to prevent the usage of an overload before it was defined in the code.
+    /// TODO: I have no recollection of how this was supposed to work. Most likely
+    /// it does not work at all...
+    int age;
+  };
+  /// Maps a "root" name of each function to the list of names of the function
+  /// overloads.
+  std::unordered_map<std::string, std::vector<Overload>> overloads;
+
   /// Pointer to the later contexts needed for IR API access.
   std::shared_ptr<TypeContext> typeCtx;
   std::shared_ptr<TranslateContext> codegenCtx;
diff --git a/codon/parser/peg/peg.cpp b/codon/parser/peg/peg.cpp
index f8b8dcc9..80ef9f49 100644
--- a/codon/parser/peg/peg.cpp
+++ b/codon/parser/peg/peg.cpp
@@ -52,8 +52,6 @@ std::shared_ptr<peg::Grammar> initParser() {
 template <typename T>
 T parseCode(Cache *cache, const std::string &file, std::string code, int line_offset,
             int col_offset, const std::string &rule) {
-  TIME("peg");
-
   // Initialize
   if (!grammar)
     grammar = initParser();
diff --git a/codon/parser/visitors/simplify/simplify_ctx.cpp b/codon/parser/visitors/simplify/simplify_ctx.cpp
index 3f87dec2..517518db 100644
--- a/codon/parser/visitors/simplify/simplify_ctx.cpp
+++ b/codon/parser/visitors/simplify/simplify_ctx.cpp
@@ -14,8 +14,9 @@ namespace codon {
 namespace ast {
 
 SimplifyItem::SimplifyItem(Kind k, std::string base, std::string canonicalName,
-                           bool global)
-    : kind(k), base(move(base)), canonicalName(move(canonicalName)), global(global) {}
+                           bool global, std::string moduleName)
+    : kind(k), base(move(base)), canonicalName(move(canonicalName)), global(global),
+      moduleName(move(moduleName)) {}
 
 SimplifyContext::SimplifyContext(std::string filename, Cache *cache)
     : Context<SimplifyItem>(move(filename)), cache(move(cache)),
@@ -31,6 +32,7 @@ std::shared_ptr<SimplifyItem> SimplifyContext::add(SimplifyItem::Kind kind,
                                                    bool global) {
   seqassert(!canonicalName.empty(), "empty canonical name for '{}'", name);
   auto t = std::make_shared<SimplifyItem>(kind, getBase(), canonicalName, global);
+  t->moduleName = getModule();
   Context<SimplifyItem>::add(name, t);
   Context<SimplifyItem>::add(canonicalName, t);
   return t;
@@ -60,6 +62,14 @@ std::string SimplifyContext::getBase() const {
   return bases.back().name;
 }
 
+std::string SimplifyContext::getModule() const {
+  std::string base = moduleName.status == ImportFile::STDLIB ? "std." : "";
+  base += moduleName.module;
+  if (startswith(base, "__main__"))
+    base = base.substr(8);
+  return base;
+}
+
 std::string SimplifyContext::generateCanonicalName(const std::string &name,
                                                    bool includeBase,
                                                    bool zeroId) const {
@@ -67,12 +77,8 @@ std::string SimplifyContext::generateCanonicalName(const std::string &name,
   bool alreadyGenerated = name.find('.') != std::string::npos;
   if (includeBase && !alreadyGenerated) {
     std::string base = getBase();
-    if (base.empty()) {
-      base = moduleName.status == ImportFile::STDLIB ? "std." : "";
-      base += moduleName.module;
-      if (startswith(base, "__main__"))
-        base = base.substr(8);
-    }
+    if (base.empty())
+      base = getModule();
     newName = (base.empty() ? "" : (base + ".")) + newName;
   }
   auto num = cache->identifierCount[newName]++;
diff --git a/codon/parser/visitors/simplify/simplify_ctx.h b/codon/parser/visitors/simplify/simplify_ctx.h
index 11a628a1..468ded2a 100644
--- a/codon/parser/visitors/simplify/simplify_ctx.h
+++ b/codon/parser/visitors/simplify/simplify_ctx.h
@@ -32,13 +32,16 @@ struct SimplifyItem {
   bool global;
   /// Non-empty string if a variable is import variable
   std::string importPath;
+  /// Full module name
+  std::string moduleName;
 
 public:
-  SimplifyItem(Kind k, std::string base, std::string canonicalName,
-               bool global = false);
+  SimplifyItem(Kind k, std::string base, std::string canonicalName, bool global = false,
+               std::string moduleName = "");
 
   /// Convenience getters.
   std::string getBase() const { return base; }
+  std::string getModule() const { return moduleName; }
   bool isGlobal() const { return global; }
   bool isVar() const { return kind == Var; }
   bool isFunc() const { return kind == Func; }
@@ -107,6 +110,8 @@ public:
   /// Return a canonical name of the top-most base, or an empty string if this is a
   /// top-level base.
   std::string getBase() const;
+  /// Return the current module.
+  std::string getModule() const;
   /// Return the current base nesting level (note: bases, not blocks).
   int getLevel() const { return bases.size(); }
   /// Pretty-print the current context state.
diff --git a/codon/parser/visitors/simplify/simplify_stmt.cpp b/codon/parser/visitors/simplify/simplify_stmt.cpp
index 3c4b9386..7e9f2c3b 100644
--- a/codon/parser/visitors/simplify/simplify_stmt.cpp
+++ b/codon/parser/visitors/simplify/simplify_stmt.cpp
@@ -437,28 +437,30 @@ void SimplifyVisitor::visit(FunctionStmt *stmt) {
       if (stmt->decorators.size() != 1)
         error("__attribute__ cannot be mixed with other decorators");
       attr.isAttribute = true;
-    } else if (d->isId(Attr::LLVM))
+    } else if (d->isId(Attr::LLVM)) {
       attr.set(Attr::LLVM);
-    else if (d->isId(Attr::Python))
+    } else if (d->isId(Attr::Python)) {
       attr.set(Attr::Python);
-    else if (d->isId(Attr::Internal))
+    } else if (d->isId(Attr::Internal)) {
       attr.set(Attr::Internal);
-    else if (d->isId(Attr::Atomic))
+    } else if (d->isId(Attr::Atomic)) {
       attr.set(Attr::Atomic);
-    else if (d->isId(Attr::Property))
+    } else if (d->isId(Attr::Property)) {
       attr.set(Attr::Property);
-    else if (d->isId(Attr::ForceRealize))
+    } else if (d->isId(Attr::ForceRealize)) {
       attr.set(Attr::ForceRealize);
-    else {
+    } else {
       // Let's check if this is a attribute
       auto dt = transform(clone(d));
       if (dt && dt->getId()) {
         auto ci = ctx->find(dt->getId()->value);
         if (ci && ci->kind == SimplifyItem::Func) {
-          if (ctx->cache->functions[ci->canonicalName].ast->attributes.isAttribute) {
-            attr.set(ci->canonicalName);
-            continue;
-          }
+          if (ctx->cache->overloads[ci->canonicalName].size() == 1)
+            if (ctx->cache->functions[ctx->cache->overloads[ci->canonicalName][0].name]
+                    .ast->attributes.isAttribute) {
+              attr.set(ci->canonicalName);
+              continue;
+            }
         }
       }
       decorators.emplace_back(clone(d));
@@ -473,19 +475,22 @@ void SimplifyVisitor::visit(FunctionStmt *stmt) {
   }
 
   bool isClassMember = ctx->inClass();
-  if (isClassMember && !endswith(stmt->name, ".dispatch") &&
-      ctx->cache->classes[ctx->bases.back().name].methods[stmt->name].empty()) {
-    generateDispatch(stmt->name);
-  }
-  auto func_name = stmt->name;
-  if (endswith(stmt->name, ".dispatch"))
-    func_name = func_name.substr(0, func_name.size() - 9);
-  auto canonicalName = ctx->generateCanonicalName(
-      func_name, true, isClassMember && !endswith(stmt->name, ".dispatch"));
-  if (endswith(stmt->name, ".dispatch")) {
-    canonicalName += ".dispatch";
-    ctx->cache->reverseIdentifierLookup[canonicalName] = func_name;
+  std::string rootName;
+  if (isClassMember) {
+    auto &m = ctx->cache->classes[ctx->bases.back().name].methods;
+    auto i = m.find(stmt->name);
+    if (i != m.end())
+      rootName = i->second;
+  } else if (auto c = ctx->find(stmt->name)) {
+    if (c->isFunc() && c->getModule() == ctx->getModule() &&
+        c->getBase() == ctx->getBase())
+      rootName = c->canonicalName;
   }
+  if (rootName.empty())
+    rootName = ctx->generateCanonicalName(stmt->name, true);
+  auto canonicalName =
+      format("{}:{}", rootName, ctx->cache->overloads[rootName].size());
+  ctx->cache->reverseIdentifierLookup[canonicalName] = stmt->name;
   bool isEnclosedFunc = ctx->inFunction();
 
   if (attr.has(Attr::ForceRealize) && (ctx->getLevel() || isClassMember))
@@ -495,7 +500,7 @@ void SimplifyVisitor::visit(FunctionStmt *stmt) {
   ctx->bases = std::vector<SimplifyContext::Base>();
   if (!isClassMember)
     // Class members are added to class' method table
-    ctx->add(SimplifyItem::Func, func_name, canonicalName, ctx->isToplevel());
+    ctx->add(SimplifyItem::Func, stmt->name, rootName, ctx->isToplevel());
   if (isClassMember)
     ctx->bases.push_back(oldBases[0]);
   ctx->bases.emplace_back(SimplifyContext::Base{canonicalName}); // Add new base...
@@ -614,8 +619,7 @@ void SimplifyVisitor::visit(FunctionStmt *stmt) {
     // ... set the enclosing class name...
     attr.parentClass = ctx->bases.back().name;
     // ... add the method to class' method list ...
-    ctx->cache->classes[ctx->bases.back().name].methods[func_name].push_back(
-        {canonicalName, nullptr, ctx->cache->age});
+    ctx->cache->classes[ctx->bases.back().name].methods[stmt->name] = rootName;
     // ... and if the function references outer class variable (by definition a
     // generic), mark it as not static as it needs fully instantiated class to be
     // realized. For example, in class A[T]: def foo(): pass, A.foo() can be realized
@@ -624,6 +628,7 @@ void SimplifyVisitor::visit(FunctionStmt *stmt) {
     if (isMethod)
       attr.set(Attr::Method);
   }
+  ctx->cache->overloads[rootName].push_back({canonicalName, ctx->cache->age});
 
   std::vector<CallExpr::Arg> partialArgs;
   if (!captures.empty()) {
@@ -649,21 +654,21 @@ void SimplifyVisitor::visit(FunctionStmt *stmt) {
 
   ExprPtr finalExpr;
   if (!captures.empty())
-    finalExpr = N<CallExpr>(N<IdExpr>(func_name), partialArgs);
+    finalExpr = N<CallExpr>(N<IdExpr>(stmt->name), partialArgs);
   if (isClassMember && decorators.size())
     error("decorators cannot be applied to class methods");
   for (int j = int(decorators.size()) - 1; j >= 0; j--) {
     if (auto c = const_cast<CallExpr *>(decorators[j]->getCall())) {
       c->args.emplace(c->args.begin(),
-                      CallExpr::Arg{"", finalExpr ? finalExpr : N<IdExpr>(func_name)});
+                      CallExpr::Arg{"", finalExpr ? finalExpr : N<IdExpr>(stmt->name)});
       finalExpr = N<CallExpr>(c->expr, c->args);
     } else {
       finalExpr =
-          N<CallExpr>(decorators[j], finalExpr ? finalExpr : N<IdExpr>(func_name));
+          N<CallExpr>(decorators[j], finalExpr ? finalExpr : N<IdExpr>(stmt->name));
     }
   }
   if (finalExpr)
-    resultStmt = transform(N<AssignStmt>(N<IdExpr>(func_name), finalExpr));
+    resultStmt = transform(N<AssignStmt>(N<IdExpr>(stmt->name), finalExpr));
 }
 
 void SimplifyVisitor::visit(ClassStmt *stmt) {
@@ -744,6 +749,7 @@ void SimplifyVisitor::visit(ClassStmt *stmt) {
   ClassStmt *originalAST = nullptr;
   auto classItem =
       std::make_shared<SimplifyItem>(SimplifyItem::Type, "", "", ctx->isToplevel());
+  classItem->moduleName = ctx->getModule();
   if (!extension) {
     classItem->canonicalName = canonicalName =
         ctx->generateCanonicalName(name, !attr.has(Attr::Internal));
@@ -949,22 +955,29 @@ void SimplifyVisitor::visit(ClassStmt *stmt) {
   for (int ai = 0; ai < baseASTs.size(); ai++) {
     // FUNCS
     for (auto &mm : ctx->cache->classes[baseASTs[ai]->name].methods)
-      for (auto &mf : mm.second) {
+      for (auto &mf : ctx->cache->overloads[mm.second]) {
         auto f = ctx->cache->functions[mf.name].ast;
         if (f->attributes.has("autogenerated"))
           continue;
 
         auto subs = substitutions[ai];
-        if (ctx->cache->classes[ctx->bases.back().name]
-                .methods[ctx->cache->reverseIdentifierLookup[f->name]]
-                .empty())
-          generateDispatch(ctx->cache->reverseIdentifierLookup[f->name]);
-        auto newName = ctx->generateCanonicalName(
-            ctx->cache->reverseIdentifierLookup[f->name], true);
+
+        std::string rootName;
+        auto &mts = ctx->cache->classes[ctx->bases.back().name].methods;
+        auto it = mts.find(ctx->cache->reverseIdentifierLookup[f->name]);
+        if (it != mts.end())
+          rootName = it->second;
+        else
+          rootName = ctx->generateCanonicalName(
+              ctx->cache->reverseIdentifierLookup[f->name], true);
+        auto newCanonicalName =
+            format("{}:{}", rootName, ctx->cache->overloads[rootName].size());
+        ctx->cache->reverseIdentifierLookup[newCanonicalName] =
+            ctx->cache->reverseIdentifierLookup[f->name];
         auto nf = std::dynamic_pointer_cast<FunctionStmt>(
             replace(std::static_pointer_cast<Stmt>(f), subs));
-        subs[nf->name] = N<IdExpr>(newName);
-        nf->name = newName;
+        subs[nf->name] = N<IdExpr>(newCanonicalName);
+        nf->name = newCanonicalName;
         suite->stmts.push_back(nf);
         nf->attributes.parentClass = ctx->bases.back().name;
 
@@ -972,10 +985,10 @@ void SimplifyVisitor::visit(ClassStmt *stmt) {
         if (nf->attributes.has(".changedSelf")) // replace self type with new class
           nf->args[0].type = transformType(ctx->bases.back().ast);
         preamble->functions.push_back(clone(nf));
-        ctx->cache->functions[newName].ast = nf;
+        ctx->cache->overloads[rootName].push_back({newCanonicalName, ctx->cache->age});
+        ctx->cache->functions[newCanonicalName].ast = nf;
         ctx->cache->classes[ctx->bases.back().name]
-            .methods[ctx->cache->reverseIdentifierLookup[f->name]]
-            .push_back({newName, nullptr, ctx->cache->age});
+            .methods[ctx->cache->reverseIdentifierLookup[f->name]] = rootName;
       }
   }
   for (auto sp : getClassMethods(stmt->suite))
@@ -1248,8 +1261,10 @@ StmtPtr SimplifyVisitor::transformCImport(const std::string &name,
   auto f = N<FunctionStmt>(name, ret ? ret->clone() : N<IdExpr>("void"), fnArgs,
                            nullptr, attr);
   StmtPtr tf = transform(f); // Already in the preamble
-  if (!altName.empty())
+  if (!altName.empty()) {
     ctx->add(altName, ctx->find(name));
+    ctx->remove(name);
+  }
   return tf;
 }
 
@@ -1392,10 +1407,11 @@ void SimplifyVisitor::transformNewImport(const ImportFile &file) {
     stmts[0] = N<SuiteStmt>();
     // Add a def import(): ... manually to the cache and to the preamble (it won't be
     // transformed here!).
-    ctx->cache->functions[importVar].ast =
-        N<FunctionStmt>(importVar, nullptr, std::vector<Param>{}, N<SuiteStmt>(stmts),
-                        Attr({Attr::ForceRealize}));
-    preamble->functions.push_back(ctx->cache->functions[importVar].ast->clone());
+    ctx->cache->overloads[importVar].push_back({importVar, ctx->cache->age});
+    ctx->cache->functions[importVar + ":0"].ast =
+        N<FunctionStmt>(importVar + ":0", nullptr, std::vector<Param>{},
+                        N<SuiteStmt>(stmts), Attr({Attr::ForceRealize}));
+    preamble->functions.push_back(ctx->cache->functions[importVar + ":0"].ast->clone());
     ;
   }
 }
@@ -1768,15 +1784,5 @@ std::vector<StmtPtr> SimplifyVisitor::getClassMethods(const StmtPtr &s) {
   return v;
 }
 
-void SimplifyVisitor::generateDispatch(const std::string &name) {
-  transform(N<FunctionStmt>(
-      name + ".dispatch", nullptr,
-      std::vector<Param>{Param("*args"), Param("**kwargs")},
-      N<SuiteStmt>(N<ReturnStmt>(N<CallExpr>(
-          N<DotExpr>(N<IdExpr>(ctx->bases.back().name), name),
-          N<StarExpr>(N<IdExpr>("args")), N<KeywordStarExpr>(N<IdExpr>("kwargs"))))),
-      Attr({"autogenerated"})));
-}
-
 } // namespace ast
 } // namespace codon
diff --git a/codon/parser/visitors/translate/translate.cpp b/codon/parser/visitors/translate/translate.cpp
index 492211d6..7e0ba953 100644
--- a/codon/parser/visitors/translate/translate.cpp
+++ b/codon/parser/visitors/translate/translate.cpp
@@ -296,7 +296,8 @@ void TranslateVisitor::visit(ForStmt *stmt) {
     auto c = stmt->decorator->getCall();
     seqassert(c, "for par is not a call: {}", stmt->decorator->toString());
     auto fc = c->expr->getType()->getFunc();
-    seqassert(fc && fc->ast->name == "std.openmp.for_par", "for par is not a function");
+    seqassert(fc && fc->ast->name == "std.openmp.for_par:0",
+              "for par is not a function");
     auto schedule =
         fc->funcGenerics[0].type->getStatic()->expr->staticValue.getString();
     bool ordered = fc->funcGenerics[1].type->getStatic()->expr->staticValue.getInt();
diff --git a/codon/parser/visitors/typecheck/typecheck.h b/codon/parser/visitors/typecheck/typecheck.h
index 97b77ac0..f8013fc6 100644
--- a/codon/parser/visitors/typecheck/typecheck.h
+++ b/codon/parser/visitors/typecheck/typecheck.h
@@ -313,6 +313,8 @@ private:
   int64_t translateIndex(int64_t idx, int64_t len, bool clamp = false);
   int64_t sliceAdjustIndices(int64_t length, int64_t *start, int64_t *stop,
                              int64_t step);
+  types::FuncTypePtr findDispatch(const std::string &fn);
+  std::string getRootName(const std::string &name);
 
   friend struct Cache;
 };
diff --git a/codon/parser/visitors/typecheck/typecheck_ctx.cpp b/codon/parser/visitors/typecheck/typecheck_ctx.cpp
index 2e5ba2f7..aac6eb51 100644
--- a/codon/parser/visitors/typecheck/typecheck_ctx.cpp
+++ b/codon/parser/visitors/typecheck/typecheck_ctx.cpp
@@ -142,22 +142,23 @@ std::vector<types::FuncTypePtr> TypeContext::findMethod(const std::string &typeN
   auto m = cache->classes.find(typeName);
   if (m != cache->classes.end()) {
     auto t = m->second.methods.find(method);
-    if (t != m->second.methods.end() && !t->second.empty()) {
-      seqassert(!t->second.empty() && endswith(t->second[0].name, ".dispatch"),
-                "first method '{}' is not dispatch", t->second[0].name);
+    if (t != m->second.methods.end()) {
+      auto mt = cache->overloads[t->second];
       std::unordered_set<std::string> signatureLoci;
       std::vector<types::FuncTypePtr> vv;
-      for (int mti = int(t->second.size()) - 1; mti > 0; mti--) {
-        auto &mt = t->second[mti];
-        if (mt.age <= age) {
+      for (int mti = int(mt.size()) - 1; mti >= 0; mti--) {
+        auto &m = mt[mti];
+        if (endswith(m.name, ":dispatch"))
+          continue;
+        if (m.age <= age) {
           if (hideShadowed) {
-            auto sig = cache->functions[mt.name].ast->signature();
+            auto sig = cache->functions[m.name].ast->signature();
             if (!in(signatureLoci, sig)) {
               signatureLoci.insert(sig);
-              vv.emplace_back(mt.type);
+              vv.emplace_back(cache->functions[m.name].type);
             }
           } else {
-            vv.emplace_back(mt.type);
+            vv.emplace_back(cache->functions[m.name].type);
           }
         }
       }
diff --git a/codon/parser/visitors/typecheck/typecheck_expr.cpp b/codon/parser/visitors/typecheck/typecheck_expr.cpp
index 0a390879..78d4171c 100644
--- a/codon/parser/visitors/typecheck/typecheck_expr.cpp
+++ b/codon/parser/visitors/typecheck/typecheck_expr.cpp
@@ -105,6 +105,9 @@ void TypecheckVisitor::visit(IdExpr *expr) {
     return;
   }
   auto val = ctx->find(expr->value);
+  if (!val) {
+    val = ctx->find(expr->value + ":0"); // is it function?!
+  }
   seqassert(val, "cannot find IdExpr '{}' ({})", expr->value, expr->getSrcInfo());
 
   auto t = ctx->instantiate(expr, val->type);
@@ -725,14 +728,17 @@ ExprPtr TypecheckVisitor::transformBinary(BinaryExpr *expr, bool isAtomic,
 
 ExprPtr TypecheckVisitor::transformStaticTupleIndex(ClassType *tuple, ExprPtr &expr,
                                                     ExprPtr &index) {
-  if (!tuple->getRecord() ||
-      in(std::set<std::string>{"Ptr", "pyobj", "str", "Array"}, tuple->name))
+  if (!tuple->getRecord())
+    return nullptr;
+  if (!startswith(tuple->name, TYPE_TUPLE) && !startswith(tuple->name, TYPE_PARTIAL))
+    // in(std::set<std::string>{"Ptr", "pyobj", "str", "Array"}, tuple->name))
     // Ptr, pyobj and str are internal types and have only one overloaded __getitem__
     return nullptr;
-  if (ctx->cache->classes[tuple->name].methods["__getitem__"].size() != 2)
-    // n.b.: there is dispatch as well
-    // TODO: be smarter! there might be a compatible getitem?
-    return nullptr;
+  // if (in(ctx->cache->classes[tuple->name].methods, "__getitem__")) {
+  //     ctx->cache->overloads[ctx->cache->classes[tuple->name].methods["__getitem__"]]
+  //             .size() != 1)
+  //   return nullptr;
+  // }
 
   // Extract a static integer value from a compatible expression.
   auto getInt = [&](int64_t *o, const ExprPtr &e) {
@@ -919,9 +925,7 @@ ExprPtr TypecheckVisitor::transformDot(DotExpr *expr,
   } else if (methods.size() > 1) {
     auto m = ctx->cache->classes.find(typ->name);
     auto t = m->second.methods.find(expr->member);
-    seqassert(!t->second.empty() && endswith(t->second[0].name, ".dispatch"),
-              "first method is not dispatch");
-    bestMethod = t->second[0].type;
+    bestMethod = findDispatch(t->second);
   } else {
     bestMethod = methods[0];
   }
@@ -1036,7 +1040,8 @@ ExprPtr TypecheckVisitor::transformCall(CallExpr *expr, const types::TypePtr &in
                             ctx->bases.back().supers, expr->args);
     if (m.empty())
       error("no matching super methods are available");
-    // LOG("found {} <- {}", ctx->bases.back().type->getFunc()->toString(), m[0]->toString());
+    // LOG("found {} <- {}", ctx->bases.back().type->getFunc()->toString(),
+    // m[0]->toString());
     ExprPtr e = N<CallExpr>(N<IdExpr>(m[0]->ast->name), expr->args);
     return transform(e, false, true);
   }
@@ -1700,7 +1705,7 @@ TypecheckVisitor::findBestMethod(const Expr *expr, const std::string &member,
 std::vector<types::FuncTypePtr>
 TypecheckVisitor::findSuperMethods(const types::FuncTypePtr &func) {
   if (func->ast->attributes.parentClass.empty() ||
-      endswith(func->ast->name, ".dispatch"))
+      endswith(func->ast->name, ":dispatch"))
     return {};
   auto p = ctx->find(func->ast->attributes.parentClass)->type;
   if (!p || !p->getClass())
@@ -1711,14 +1716,13 @@ TypecheckVisitor::findSuperMethods(const types::FuncTypePtr &func) {
   std::vector<types::FuncTypePtr> result;
   if (m != ctx->cache->classes.end()) {
     auto t = m->second.methods.find(methodName);
-    if (t != m->second.methods.end() && !t->second.empty()) {
-      seqassert(!t->second.empty() && endswith(t->second[0].name, ".dispatch"),
-                "first method '{}' is not dispatch", t->second[0].name);
-      for (int mti = 1; mti < t->second.size(); mti++) {
-        auto &mt = t->second[mti];
-        if (mt.type->ast->name == func->ast->name)
+    if (t != m->second.methods.end()) {
+      for (auto &m : ctx->cache->overloads[t->second]) {
+        if (endswith(m.name, ":dispatch"))
+          continue;
+        if (m.name == func->ast->name)
           break;
-        result.emplace_back(mt.type);
+        result.emplace_back(ctx->cache->functions[m.name].type);
       }
     }
   }
@@ -1860,5 +1864,45 @@ int64_t TypecheckVisitor::sliceAdjustIndices(int64_t length, int64_t *start,
   return 0;
 }
 
+types::FuncTypePtr TypecheckVisitor::findDispatch(const std::string &fn) {
+  for (auto &m : ctx->cache->overloads[fn])
+    if (endswith(ctx->cache->functions[m.name].ast->name, ":dispatch"))
+      return ctx->cache->functions[m.name].type;
+
+  // Generate dispatch and return it!
+  auto name = fn + ":dispatch";
+
+  ExprPtr root;
+  auto a = ctx->cache->functions[ctx->cache->overloads[fn][0].name].ast;
+  if (!a->attributes.parentClass.empty())
+    root = N<DotExpr>(N<IdExpr>(a->attributes.parentClass),
+                      ctx->cache->reverseIdentifierLookup[fn]);
+  else
+    root = N<IdExpr>(fn);
+  root = N<CallExpr>(root, N<StarExpr>(N<IdExpr>("args")),
+                     N<KeywordStarExpr>(N<IdExpr>("kwargs")));
+  auto ast = N<FunctionStmt>(
+      name, nullptr, std::vector<Param>{Param("*args"), Param("**kwargs")},
+      N<SuiteStmt>(N<IfStmt>(
+          N<CallExpr>(N<IdExpr>("isinstance"), root->clone(), N<IdExpr>("void")),
+          N<ExprStmt>(root->clone()), N<ReturnStmt>(root))),
+      Attr({"autogenerated"}));
+  ctx->cache->reverseIdentifierLookup[name] = ctx->cache->reverseIdentifierLookup[fn];
+
+  auto baseType =
+      ctx->instantiate(N<IdExpr>(name).get(), ctx->find(generateFunctionStub(2))->type,
+                       nullptr, false)
+          ->getRecord();
+  auto typ = std::make_shared<FuncType>(baseType, ast.get());
+  typ = std::static_pointer_cast<FuncType>(typ->generalize(ctx->typecheckLevel));
+  ctx->add(TypecheckItem::Func, name, typ);
+
+  ctx->cache->overloads[fn].insert(ctx->cache->overloads[fn].begin(), {name, 0});
+  ctx->cache->functions[name].ast = ast;
+  ctx->cache->functions[name].type = typ;
+  prependStmts->push_back(ast);
+  return typ;
+}
+
 } // namespace ast
 } // namespace codon
diff --git a/codon/parser/visitors/typecheck/typecheck_stmt.cpp b/codon/parser/visitors/typecheck/typecheck_stmt.cpp
index edbe2ad2..42ece717 100644
--- a/codon/parser/visitors/typecheck/typecheck_stmt.cpp
+++ b/codon/parser/visitors/typecheck/typecheck_stmt.cpp
@@ -474,12 +474,12 @@ void TypecheckVisitor::visit(FunctionStmt *stmt) {
   typ = std::static_pointer_cast<FuncType>(typ->generalize(ctx->typecheckLevel));
   // Check if this is a class method; if so, update the class method lookup table.
   if (isClassMember) {
-    auto &methods = ctx->cache->classes[attr.parentClass]
-                        .methods[ctx->cache->reverseIdentifierLookup[stmt->name]];
+    auto m = ctx->cache->classes[attr.parentClass]
+                 .methods[ctx->cache->reverseIdentifierLookup[stmt->name]];
     bool found = false;
-    for (auto &i : methods)
+    for (auto &i : ctx->cache->overloads[m])
       if (i.name == stmt->name) {
-        i.type = typ;
+        ctx->cache->functions[i.name].type = typ;
         found = true;
         break;
       }
@@ -570,5 +570,11 @@ void TypecheckVisitor::visit(ClassStmt *stmt) {
   stmt->done = true;
 }
 
+std::string TypecheckVisitor::getRootName(const std::string &name) {
+  auto p = name.rfind(':');
+  seqassert(p != std::string::npos, ": not found in {}", name);
+  return name.substr(0, p);
+}
+
 } // namespace ast
 } // namespace codon
diff --git a/stdlib/internal/str.codon b/stdlib/internal/str.codon
index 67a8dd67..ad062b5a 100644
--- a/stdlib/internal/str.codon
+++ b/stdlib/internal/str.codon
@@ -44,6 +44,7 @@ class str:
             if c == '\n': d = "\\n"
             elif c == '\r': d = "\\r"
             elif c == '\t': d = "\\t"
+            elif c == '\a': d = "\\a"
             elif c == '\\': d = "\\\\"
             elif c == q: d = qe
             else:
diff --git a/test/parser/simplify_stmt.codon b/test/parser/simplify_stmt.codon
index 6de479b8..d849b7dd 100644
--- a/test/parser/simplify_stmt.codon
+++ b/test/parser/simplify_stmt.codon
@@ -538,7 +538,7 @@ def foo() -> int:
     a{=a}
 foo()
 #! not a type or static expression
-#! while realizing foo (arguments foo)
+#! while realizing foo:0 (arguments foo:0)
 
 #%% function_llvm_err_4,barebones
 a = 5
diff --git a/test/parser/typecheck_expr.codon b/test/parser/typecheck_expr.codon
index 1403319e..ce02e25b 100644
--- a/test/parser/typecheck_expr.codon
+++ b/test/parser/typecheck_expr.codon
@@ -374,7 +374,7 @@ def foo(i, j, k):
     return i + j + k
 print foo(1.1, 2.2, 3.3)  #: 6.6
 p = foo(6, ...)
-print p.__class__ #: foo[int,...,...]
+print p.__class__ #: foo:0[int,...,...]
 print p(2, 1)  #: 9
 print p(k=3, j=6) #: 15
 q = p(k=1, ...)
@@ -390,11 +390,11 @@ print 42 |> add_two  #: 44
 def moo(a, b, c=3):
     print a, b, c
 m = moo(b=2, ...)
-print m.__class__ #: moo[...,int,...]
+print m.__class__ #: moo:0[...,int,...]
 m('s', 1.1) #: s 2 1.1
 # #
 n = m(c=2.2, ...)
-print n.__class__ #: moo[...,int,float]
+print n.__class__ #: moo:0[...,int,float]
 n('x') #: x 2 2.2
 print n('y').__class__ #: void
 
@@ -403,11 +403,11 @@ def ff(a, b, c):
 print ff(1.1, 2, True).__class__ #: Tuple[float,int,bool]
 print ff(1.1, ...)(2, True).__class__ #: Tuple[float,int,bool]
 y = ff(1.1, ...)(c=True, ...)
-print y.__class__ #: ff[float,...,bool]
+print y.__class__ #: ff:0[float,...,bool]
 print ff(1.1, ...)(2, ...)(True).__class__ #: Tuple[float,int,bool]
 print y('hei').__class__ #: Tuple[float,str,bool]
 z = ff(1.1, ...)(c='s', ...)
-print z.__class__ #: ff[float,...,str]
+print z.__class__ #: ff:0[float,...,str]
 
 #%% call_arguments_partial,barebones
 def doo[R, T](a: Callable[[T], R], b: Generator[T], c: Optional[T], d: T):
@@ -432,7 +432,7 @@ l = [1]
 def adder(a, b): return a+b
 doo(b=l, d=Optional(5), c=l[0], a=adder(b=4, ...))
 #: int int
-#: adder[.. Generator[int]
+#: adder:0[ Generator[int]
 #: 5
 #: 1 Optional[int]
 #: 5 int
diff --git a/test/parser/typecheck_stmt.codon b/test/parser/typecheck_stmt.codon
index ace31779..a3099c5c 100644
--- a/test/parser/typecheck_stmt.codon
+++ b/test/parser/typecheck_stmt.codon
@@ -252,7 +252,7 @@ try:
 except MyError:
     print "my"
 except OSError as o:
-    print "os", o._hdr[0], len(o._hdr[1]), o._hdr[3][-20:], o._hdr[4]
+    print "os", o._hdr.typename, len(o._hdr.msg), o._hdr.file[-20:], o._hdr.line
     #: os std.internal.types.error.OSError 9 typecheck_stmt.codon 249
 finally:
     print "whoa"  #: whoa
@@ -263,7 +263,7 @@ def foo():
 try:
     foo()
 except MyError as e:
-    print e._hdr[0], e._hdr[1] #: MyError foo!
+    print e._hdr.typename, e._hdr.msg #: MyError foo!
 
 #%% throw_error,barebones
 raise 'hello' #! cannot throw non-exception (first object member must be of type ExcHeader)
@@ -291,13 +291,13 @@ def foo(x):
     print len(x)
 foo(5) #: 4
 
-def foo(x):
+def foo2(x):
     if isinstance(x, int):
         print  x+1
         return
     print len(x)
-foo(1) #: 2
-foo('s') #: 1
+foo2(1) #: 2
+foo2('s') #: 1
 
 #%% super,barebones
 class Foo:
@@ -341,4 +341,4 @@ class Foo:
         print 'foo-1', a
 Foo.foo(1)
 #! no matching super methods are available
-#! while realizing Foo.foo.2
+#! while realizing Foo.foo:0
diff --git a/test/parser/types.codon b/test/parser/types.codon
index 764a38a9..5302905a 100644
--- a/test/parser/types.codon
+++ b/test/parser/types.codon
@@ -199,10 +199,10 @@ def f[T](x: T) -> T:
 print f(1.2).__class__ #: float
 print f('s').__class__ #: str
 
-def f[T](x: T):
-    return f(x - 1, T) if x else 1
-print f(1) #: 1
-print f(1.1).__class__ #: int
+def f2[T](x: T):
+    return f2(x - 1, T) if x else 1
+print f2(1) #: 1
+print f2(1.1).__class__ #: int
 
 
 #%% recursive_error,barebones
@@ -215,7 +215,7 @@ def rec3(x, y): #- ('a, 'b) -> 'b
         return y
 rec3(1, 's')
 #! cannot unify str and int
-#! while realizing rec3 (arguments rec3[int,str])
+#! while realizing rec3:0 (arguments rec3:0[int,str])
 
 #%% instantiate_function_2,barebones
 def fx[T](x: T) -> T:
@@ -447,13 +447,13 @@ def f(x):
     return g(x)
 print f(5), f('s') #: 5 s
 
-def f[U](x: U, y):
+def f2[U](x: U, y):
     def g[T, U](x: T, y: U):
         return (x, y)
     return g(y, x)
 x, y = 1, 'haha'
-print f(x, y).__class__ #: Tuple[str,int]
-print f('aa', 1.1, U=str).__class__ #: Tuple[float,str]
+print f2(x, y).__class__ #: Tuple[str,int]
+print f2('aa', 1.1, U=str).__class__ #: Tuple[float,str]
 
 #%% nested_fn_generic_error,barebones
 def f[U](x: U, y): # ('u, 'a) -> tuple['a, 'u]
@@ -464,7 +464,7 @@ print f(1.1, 1, int).__class__ #! cannot unify float and int
 
 #%% fn_realization,barebones
 def ff[T](x: T, y: tuple[T]):
-      print ff(T=str,...).__class__ #: ff[str,Tuple[str],str]
+      print ff(T=str,...).__class__ #: ff:0[str,Tuple[str],str]
       return x
 x = ff(1, (1,))
 print x, x.__class__ #: 1 int
@@ -474,7 +474,7 @@ def fg[T](x:T):
     def g[T](y):
         z = T()
         return z
-    print fg(T=str,...).__class__  #: fg[str,str]
+    print fg(T=str,...).__class__  #: fg:0[str,str]
     print g(1, T).__class__ #: int
 fg(1)
 print fg(1).__class__ #: void
@@ -515,7 +515,7 @@ class A[T]:
             def foo[W](t: V, u: V, v: V, w: W):
                 return (t, u, v, w)
 
-print A.B.C[bool].foo(W=str, ...).__class__ #: A.B.C.foo.2[bool,bool,bool,str,str]
+print A.B.C[bool].foo(W=str, ...).__class__ #: A.B.C.foo:0[bool,bool,bool,str,str]
 print A.B.C.foo(1,1,1,True) #: (1, 1, 1, True)
 print A.B.C.foo('x', 'x', 'x', 'x') #: ('x', 'x', 'x', 'x')
 print A.B.C.foo('x', 'x', 'x', 'x') #: ('x', 'x', 'x', 'x')
@@ -734,10 +734,10 @@ def test(name, sort, key):
 def foo(l, f):
     return [f(i) for i in l]
 test('hi', foo, lambda x: x+1) #: hi [2, 3, 4, 5]
-# TODO
-# def foof(l: List[int], x, f: Callable[[int], int]):
-#     return [f(i)+x for i in l]
-# test('qsort', foof(..., 3, ...))
+
+def foof(l: List[int], x, f: Callable[[int], int]):
+    return [f(i)+x for i in l]
+test('qsort', foof(x=3, ...), lambda x: x+1) #: qsort [5, 6, 7, 8]
 
 #%% class_fn_access,barebones
 class X[T]:
@@ -745,8 +745,7 @@ class X[T]:
         return (x+x, y+y)
 y = X[X[int]]()
 print y.__class__ #: X[X[int]]
-print X[float].foo(U=int, ...).__class__ #: X.foo.2[X[float],float,int,int]
-# print y.foo.1[float].__class__
+print X[float].foo(U=int, ...).__class__ #: X.foo:0[X[float],float,int,int]
 print X[int]().foo(1, 's') #: (2, 'ss')
 
 #%% class_partial_access,barebones
@@ -754,7 +753,7 @@ class X[T]:
     def foo[U](self, x, y: U):
         return (x+x, y+y)
 y = X[X[int]]()
-print y.foo(U=float,...).__class__ #: X.foo.2[X[X[int]],...,...]
+print y.foo(U=float,...).__class__ #: X.foo:0[X[X[int]],...,...]
 print y.foo(1, 2.2, float) #: (2, 4.4)
 
 #%% forward,barebones
@@ -765,10 +764,10 @@ def bar[T](x):
     print x, T.__class__
 foo(bar, 1)
 #: 1 int
-#: bar[...]
+#: bar:0[...]
 foo(bar(...), 's')
 #: s str
-#: bar[...]
+#: bar:0[...]
 z = bar
 z('s', int)
 #: s int
@@ -786,8 +785,8 @@ def foo(f, x):
 def bar[T](x):
     print x, T.__class__
 foo(bar(T=int,...), 1)
-#! too many arguments for bar[T1,int] (expected maximum 2, got 2)
-#! while realizing foo (arguments foo[bar[...],int])
+#! too many arguments for bar:0[T1,int] (expected maximum 2, got 2)
+#! while realizing foo:0 (arguments foo:0[bar:0[...],int])
 
 #%% sort_partial
 def foo(x, y):
@@ -806,16 +805,16 @@ def frec(x, y):
     return grec(x, y) if bl(y) else 2
 print frec(1, 2).__class__, frec('s', 1).__class__
 #! expression with void type
-#! while realizing frec (arguments frec[int,int])
+#! while realizing frec:0 (arguments frec:0[int,int])
 
 #%% return_fn,barebones
 def retfn(a):
     def inner(b, *args, **kwargs):
         print a, b, args, kwargs
-    print inner.__class__ #: retfn.inner[...,...,int,...]
+    print inner.__class__ #: retfn:0.inner:0[...,...,int,...]
     return inner(15, ...)
 f = retfn(1)
-print f.__class__ #: retfn.inner[int,...,int,...]
+print f.__class__ #: retfn:0.inner:0[int,...,int,...]
 f(2,3,foo='bar') #: 1 15 (2, 3) (foo: 'bar')
 
 #%% decorator_manual,barebones
@@ -823,7 +822,7 @@ def foo(x, *args, **kwargs):
     print x, args, kwargs
     return 1
 def dec(fn, a):
-    print 'decorating', fn.__class__ #: decorating foo[...,...,...]
+    print 'decorating', fn.__class__ #: decorating foo:0[...,...,...]
     def inner(*args, **kwargs):
         print 'decorator', args, kwargs #: decorator (5.5, 's') (z: True)
         return fn(a, *args, **kwargs)
@@ -846,7 +845,7 @@ def dec(fn, a):
     return inner
 ff = dec(foo, 10)
 print ff(5.5, 's', z=True)
-#: decorating foo[...,...,...]
+#: decorating foo:0[...,...,...]
 #: decorator (5.5, 's') (z: True)
 #: 10 (5.5, 's') (z: True)
 #: 1
@@ -856,7 +855,7 @@ def zoo(e, b, *args):
     return f'zoo: {e}, {b}, {args}'
 print zoo(2, 3)
 print zoo('s', 3)
-#: decorating zoo[...,...,...]
+#: decorating zoo:0[...,...,...]
 #: decorator (2, 3) ()
 #: zoo: 5, 2, (3)
 #: decorator ('s', 3) ()
@@ -869,9 +868,9 @@ def mydecorator(func):
         print("after")
     return inner
 @mydecorator
-def foo():
+def foo2():
     print("foo")
-foo()
+foo2()
 #: before
 #: foo
 #: after
@@ -891,7 +890,7 @@ def factorial(num):
     return n
 factorial(10)
 #: 3628800
-#: time needed for factorial[...] is 3628799
+#: time needed for factorial:0[...] is 3628799
 
 def dx1(func):
     def inner():
@@ -921,9 +920,9 @@ def dy2(func):
     return inner
 @dy1
 @dy2
-def num(a, b):
+def num2(a, b):
     return a+b
-print(num(10, 20)) #: 3600
+print(num2(10, 20)) #: 3600
 
 #%% hetero_iter,barebones
 e = (1, 2, 3, 'foo', 5, 'bar', 6)
@@ -970,14 +969,14 @@ def tee(iterable, n=2):
     return list(gen(d) for d in deques)
 it = [1,2,3,4]
 a, b = tee(it) #! cannot typecheck the program
-#! while realizing tee (arguments tee[List[int],int])
+#! while realizing tee:0 (arguments tee:0[List[int],int])
 
 #%% new_syntax,barebones
 def foo[T,U](x: type, y, z: Static[int] = 10):
     print T.__class__, U.__class__, x.__class__, y.__class__, Int[z+1].__class__
     return List[x]()
-print foo(T=int,U=str,...).__class__ #: foo[T1,x,z,int,str]
-print foo(T=int,U=str,z=5,x=bool,...).__class__ #: foo[T1,bool,5,int,str]
+print foo(T=int,U=str,...).__class__ #: foo:0[T1,x,z,int,str]
+print foo(T=int,U=str,z=5,x=bool,...).__class__ #: foo:0[T1,bool,5,int,str]
 print foo(float,3,T=int,U=str,z=5).__class__ #: List[float]
 foo(float,1,10,str,int) #: str int float int Int[11]
 
@@ -993,11 +992,11 @@ print Foo[5,int,float,6].__class__ #: Foo[5,int,float,6]
 print Foo(1.1, 10i32, [False], 10u66).__class__ #: Foo[66,bool,float,32]
 
 
-def foo[N: Static[int]]():
+def foo2[N: Static[int]]():
     print Int[N].__class__, N
 x: Static[int] = 5
 y: Static[int] = 105 - x * 2
-foo(y-x) #: Int[90] 90
+foo2(y-x) #: Int[90] 90
 
 if 1.1+2.2 > 0:
     x: Static[int] = 88