[Tolk] Rewrite the type system from Hindley-Milner to static typing

FunC's (and Tolk's before this PR) type system is based on Hindley-Milner.
This is a common approach for functional languages, where
types are inferred from usage through unification.
As a result, type declarations are not necessary:
() f(a,b) { return a+b; } // a and b now int, since `+` (int, int)

While this approach works for now, problems arise with the introduction
of new types like bool, where `!x` must handle both int and bool.
It will also become incompatible with int32 and other strict integers.
This will clash with structure methods, struggle with proper generics,
and become entirely impractical for union types.

This PR completely rewrites the type system targeting the future.
1) type of any expression is inferred and never changed
2) this is available because dependent expressions already inferred
3) forall completely removed, generic functions introduced
   (they work like template functions actually, instantiated while inferring)
4) instantiation `<...>` syntax, example: `t.tupleAt<int>(0)`
5) `as` keyword, for example `t.tupleAt(0) as int`
6) methods binding is done along with type inferring, not before
   ("before", as worked previously, was always a wrong approach)

tolk/ast.cpp

@@ -15,8 +15,9 @@
     along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include "ast.h"
+#ifdef TOLK_DEBUG
 #include "ast-stringifier.h"
-#include <iostream>
+#endif
 
 namespace tolk {
 
@@ -104,7 +105,7 @@ int Vertex<ast_parameter_list>::get_mutate_params_count() const {
 // Therefore, there is a guarantee, that all AST mutations are done via these methods,
 // easily searched by usages, and there is no another way to modify any other field.
 
-void ASTNodeExpressionBase::assign_inferred_type(TypeExpr* type) {
+void ASTNodeExpressionBase::assign_inferred_type(TypePtr type) {
   this->inferred_type = type;
 }
 
@@ -116,43 +117,79 @@ void ASTNodeExpressionBase::assign_lvalue_true() {
   this->is_lvalue = true;
 }
 
-void Vertex<ast_identifier>::assign_sym(const Symbol* sym) {
+void Vertex<ast_reference>::assign_sym(const Symbol* sym) {
   this->sym = sym;
 }
 
-void Vertex<ast_self_keyword>::assign_param_ref(const LocalVarData* self_param) {
-  this->param_ref = self_param;
-}
-
 void Vertex<ast_function_call>::assign_fun_ref(const FunctionData* fun_ref) {
   this->fun_maybe = fun_ref;
 }
 
-void Vertex<ast_dot_method_call>::assign_fun_ref(const FunctionData* fun_ref) {
-  this->fun_ref = fun_ref;
+void Vertex<ast_cast_as_operator>::assign_resolved_type(TypePtr cast_to_type) {
+  this->cast_to_type = cast_to_type;
 }
 
 void Vertex<ast_global_var_declaration>::assign_var_ref(const GlobalVarData* var_ref) {
   this->var_ref = var_ref;
 }
 
+void Vertex<ast_global_var_declaration>::assign_resolved_type(TypePtr declared_type) {
+  this->declared_type = declared_type;
+}
+
 void Vertex<ast_constant_declaration>::assign_const_ref(const GlobalConstData* const_ref) {
   this->const_ref = const_ref;
 }
 
+void Vertex<ast_constant_declaration>::assign_resolved_type(TypePtr declared_type) {
+  this->declared_type = declared_type;
+}
+
+void Vertex<ast_instantiationT_item>::assign_resolved_type(TypePtr substituted_type) {
+  this->substituted_type = substituted_type;
+}
+
 void Vertex<ast_parameter>::assign_param_ref(const LocalVarData* param_ref) {
   this->param_ref = param_ref;
 }
 
+void Vertex<ast_parameter>::assign_resolved_type(TypePtr declared_type) {
+  this->declared_type = declared_type;
+}
+
+void Vertex<ast_set_assign>::assign_fun_ref(const FunctionData* fun_ref) {
+  this->fun_ref = fun_ref;
+}
+
+void Vertex<ast_unary_operator>::assign_fun_ref(const FunctionData* fun_ref) {
+  this->fun_ref = fun_ref;
+}
+
+void Vertex<ast_binary_operator>::assign_fun_ref(const FunctionData* fun_ref) {
+  this->fun_ref = fun_ref;
+}
+
+void Vertex<ast_dot_access>::assign_target(const DotTarget& target) {
+  this->target = target;
+}
+
 void Vertex<ast_function_declaration>::assign_fun_ref(const FunctionData* fun_ref) {
   this->fun_ref = fun_ref;
 }
 
-void Vertex<ast_local_var>::assign_var_ref(const Symbol* var_ref) {
-  this->var_maybe = var_ref;
+void Vertex<ast_function_declaration>::assign_resolved_type(TypePtr declared_return_type) {
+  this->declared_return_type = declared_return_type;
 }
 
-void Vertex<ast_import_statement>::assign_src_file(const SrcFile* file) {
+void Vertex<ast_local_var_lhs>::assign_var_ref(const LocalVarData* var_ref) {
+  this->var_ref = var_ref;
+}
+
+void Vertex<ast_local_var_lhs>::assign_resolved_type(TypePtr declared_type) {
+  this->declared_type = declared_type;
+}
+
+void Vertex<ast_import_directive>::assign_src_file(const SrcFile* file) {
   this->file = file;
 }