Fix missing generic issue

codon/parser/ast/stmt.cpp

@@ -480,6 +480,56 @@ std::string FunctionStmt::getDocstr() {
   return "";
 }
 
+// Search expression tree for a identifier
+class IdSearchVisitor : public CallbackASTVisitor<bool, bool> {
+  std::string what;
+  bool result;
+
+public:
+  IdSearchVisitor(std::string what) : what(std::move(what)), result(false) {}
+  bool transform(const std::shared_ptr<Expr> &expr) override {
+    if (result)
+      return result;
+    IdSearchVisitor v(what);
+    if (expr)
+      expr->accept(v);
+    return result = v.result;
+  }
+  bool transform(const std::shared_ptr<Stmt> &stmt) override {
+    if (result)
+      return result;
+    IdSearchVisitor v(what);
+    if (stmt)
+      stmt->accept(v);
+    return result = v.result;
+  }
+  void visit(IdExpr *expr) override {
+    if (expr->value == what)
+      result = true;
+  }
+};
+
+/// Check if a function can be called with the given arguments.
+/// See @c reorderNamedArgs for details.
+std::unordered_set<std::string> FunctionStmt::getNonInferrableGenerics() {
+  std::unordered_set<std::string> nonInferrableGenerics;
+  for (auto &a : args) {
+    if (a.status == Param::Generic && !a.defaultValue) {
+      bool inferrable = false;
+      for (auto &b : args)
+        if (b.type && IdSearchVisitor(a.name).transform(b.type)) {
+          inferrable = true;
+          break;
+        }
+      if (ret && IdSearchVisitor(a.name).transform(ret))
+        inferrable = true;
+      if (!inferrable)
+        nonInferrableGenerics.insert(a.name);
+    }
+  }
+  return nonInferrableGenerics;
+}
+
 ClassStmt::ClassStmt(std::string name, std::vector<Param> args, StmtPtr suite,
                      std::vector<ExprPtr> decorators, std::vector<ExprPtr> baseClasses,
                      std::vector<ExprPtr> staticBaseClasses)

codon/parser/ast/stmt.h

@@ -482,6 +482,7 @@ struct FunctionStmt : public Stmt {
 
   FunctionStmt *getFunction() override { return this; }
   std::string getDocstr();
+  std::unordered_set<std::string> getNonInferrableGenerics();
 };
 
 /// Class statement (@(attributes...) class name[generics...]: args... ; suite).

codon/parser/visitors/typecheck/call.cpp

@@ -281,8 +281,10 @@ ExprPtr TypecheckVisitor::callReorderArguments(FuncTypePtr calleeFn, CallExpr *e
   };
 
   // Handle reordered arguments (see @c reorderNamedArgs for details)
+  bool partial = false;
   auto reorderFn = [&](int starArgIndex, int kwstarArgIndex,
-                       const std::vector<std::vector<int>> &slots, bool partial) {
+                       const std::vector<std::vector<int>> &slots, bool _partial) {
+    partial = _partial;
     ctx->addBlock(); // add function generics to typecheck default arguments
     addFunctionGenerics(calleeFn->getFunc().get());
     for (size_t si = 0, pi = 0; si < slots.size(); si++) {
@@ -410,18 +412,28 @@ ExprPtr TypecheckVisitor::callReorderArguments(FuncTypePtr calleeFn, CallExpr *e
                 (!expr->hasAttr(ExprAttr::OrderedCall) &&
                  typeArgs.size() == calleeFn->funcGenerics.size()),
             "bad vector sizes");
-  for (size_t si = 0;
-       !expr->hasAttr(ExprAttr::OrderedCall) && si < calleeFn->funcGenerics.size();
-       si++) {
-    if (typeArgs[si]) {
-      auto typ = typeArgs[si]->type;
-      if (calleeFn->funcGenerics[si].type->isStaticType()) {
-        if (!typeArgs[si]->isStatic()) {
-          E(Error::EXPECTED_STATIC, typeArgs[si]);
+  if (!calleeFn->funcGenerics.empty()) {
+    auto niGenerics = calleeFn->ast->getNonInferrableGenerics();
+    for (size_t si = 0;
+         !expr->hasAttr(ExprAttr::OrderedCall) && si < calleeFn->funcGenerics.size();
+         si++) {
+      if (typeArgs[si]) {
+        auto typ = typeArgs[si]->type;
+        if (calleeFn->funcGenerics[si].type->isStaticType()) {
+          if (!typeArgs[si]->isStatic()) {
+            E(Error::EXPECTED_STATIC, typeArgs[si]);
+          }
+          typ = Type::makeStatic(ctx->cache, typeArgs[si]);
+        }
+        unify(typ, calleeFn->funcGenerics[si].type);
+      } else {
+        if (calleeFn->funcGenerics[si].type->getUnbound() &&
+            !calleeFn->ast->args[si].defaultValue &&
+            !partial &&
+            in(niGenerics, calleeFn->funcGenerics[si].name)) {
+          error("generic '{}' not provided", calleeFn->funcGenerics[si].niceName);
         }
-        typ = Type::makeStatic(ctx->cache, typeArgs[si]);
       }
-      unify(typ, calleeFn->funcGenerics[si].type);
     }
   }
 

codon/parser/visitors/typecheck/collections.cpp

@@ -199,6 +199,7 @@ ExprPtr TypecheckVisitor::transformComprehension(const std::string &type,
 /// @example
 ///   `(a1, ..., aN)` -> `Tuple.N.__new__(a1, ..., aN)`
 void TypecheckVisitor::visit(TupleExpr *expr) {
+  expr->setType(ctx->getUnbound());
   for (int ai = 0; ai < expr->items.size(); ai++)
     if (auto star = expr->items[ai]->getStar()) {
       // Case: unpack star expressions (e.g., `*arg` -> `arg.item1, arg.item2, ...`)
@@ -226,6 +227,7 @@ void TypecheckVisitor::visit(TupleExpr *expr) {
   auto tupleName = generateTuple(expr->items.size());
   resultExpr =
       transform(N<CallExpr>(N<DotExpr>(tupleName, "__new__"), clone(expr->items)));
+  unify(expr->type, resultExpr->type);
 }
 
 /// Transform a tuple generator expression.

codon/parser/visitors/typecheck/typecheck.cpp

@@ -217,20 +217,55 @@ types::FuncTypePtr TypecheckVisitor::findBestMethod(
   return m.empty() ? nullptr : m[0];
 }
 
+// Search expression tree for a identifier
+class IdSearchVisitor : public CallbackASTVisitor<bool, bool> {
+  std::string what;
+  bool result;
+
+public:
+  IdSearchVisitor(std::string what) : what(std::move(what)), result(false) {}
+  bool transform(const std::shared_ptr<Expr> &expr) override {
+    if (result)
+      return result;
+    IdSearchVisitor v(what);
+    if (expr)
+      expr->accept(v);
+    return v.result;
+  }
+  bool transform(const std::shared_ptr<Stmt> &stmt) override {
+    if (result)
+      return result;
+    IdSearchVisitor v(what);
+    if (stmt)
+      stmt->accept(v);
+    return v.result;
+  }
+  void visit(IdExpr *expr) override {
+    if (expr->value == what)
+      result = true;
+  }
+};
+
 /// Check if a function can be called with the given arguments.
 /// See @c reorderNamedArgs for details.
 int TypecheckVisitor::canCall(const types::FuncTypePtr &fn,
                               const std::vector<CallExpr::Arg> &args) {
   std::vector<std::pair<types::TypePtr, size_t>> reordered;
+  auto niGenerics = fn->ast->getNonInferrableGenerics();
   auto score = ctx->reorderNamedArgs(
       fn.get(), args,
       [&](int s, int k, const std::vector<std::vector<int>> &slots, bool _) {
         for (int si = 0; si < slots.size(); si++) {
           if (fn->ast->args[si].status == Param::Generic) {
-            if (slots[si].empty())
+            if (slots[si].empty()) {
+              // is this "real" type?
+              if (in(niGenerics, fn->ast->args[si].name) &&
+                  !fn->ast->args[si].defaultValue)
+                return -1;
               reordered.push_back({nullptr, 0});
-            else
+            } else {
               reordered.push_back({args[slots[si][0]].value->type, slots[si][0]});
+            }
           } else if (si == s || si == k || slots[si].size() != 1) {
             // Ignore *args, *kwargs and default arguments
             reordered.push_back({nullptr, 0});

test/parser/simplify_stmt.codon

@@ -590,7 +590,7 @@ def f(x):
     return g(x)
 print f(5) #: 6
 
-##% nested_generic_static,barebones
+#%% nested_generic_static,barebones
 def foo():
     N: Static[int] = 5
     Z: Static[int] = 15

test/parser/typecheck_expr.codon

@@ -191,7 +191,7 @@ foo(int, float)  #! foo() takes 1 arguments (2 given)
 #%% instantiate_err_2,barebones
 def foo[N, T]():
     return N()
-foo(int)  #! cannot typecheck the program
+foo(int)  #! generic 'T' not provided
 
 #%% instantiate_err_3,barebones
 Ptr[int, float]()  #! Ptr takes 1 generics (2 given)

test/parser/types.codon

@@ -1856,3 +1856,14 @@ a.test2(2)
 #: test:B 1
 #: test2:B 2
 
+
+#%% no_generic,barebones
+def foo(a, b: Static[int]):
+    pass
+foo(5)  #! generic 'b' not provided
+
+
+#%% no_generic_2,barebones
+def f(a, b, T: type):
+    print(a, b)
+f(1, 2)  #! generic 'T' not provided