[Tolk] AST-based semantic analysis, get rid of Expr

This is a huge refactoring focusing on untangling compiler internals
(previously forked from FunC).
The goal is to convert AST directly to Op (a kind of IR representation),
doing all code analysis at AST level.

Noteable changes:
- AST-based semantic kernel includes: registering global symbols,
  scope handling and resolving local/global identifiers,
  lvalue/rvalue calc and check, implicit return detection,
  mutability analysis, pure/impure validity checks,
  simple constant folding
- values of `const` variables are calculated NOT based on CodeBlob,
  but via a newly-introduced AST-based constant evaluator
- AST vertices are now inherited from expression/statement/other;
  expression vertices have common properties (TypeExpr, lvalue/rvalue)
- symbol table is rewritten completely, SymDef/SymVal no longer exist,
  lexer now doesn't need to register identifiers
- AST vertices have references to symbols, filled at different
  stages of pipeline
- the remaining "FunC legacy part" is almost unchanged besides Expr
  which was fully dropped; AST is converted to Ops (IR) directly

tolk/pipe-refine-lvalue-for-mutate.cpp

@@ -0,0 +1,118 @@
+/*
+    This file is part of TON Blockchain source code.
+
+    TON Blockchain is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; either version 2
+    of the License, or (at your option) any later version.
+
+    TON Blockchain is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with TON Blockchain.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "tolk.h"
+#include "ast.h"
+#include "ast-visitor.h"
+
+/*
+ *   This pipe refines rvalue/lvalue and checks `mutate` arguments validity.
+ *   It happens after type inferring (after methods binding), because it uses fun_ref of calls.
+ *
+ *   Example: `a.increment().increment()`, the first `a.increment()` becomes lvalue (assume that increment mutates self).
+ *   Example: `increment(a)` is invalid, should be `increment(mutate a)`.
+ *
+ *   Note, that explicitly specifying `mutate` for arguments, like `increment(mutate a)` is on purpose.
+ * If we wished `increment(a)` to be valid (to work and mutate `a`, like passing by ref), it would also be done here,
+ * refining `a` to be lvalue. But to avoid unexpected mutations, `mutate` keyword for an argument is required.
+ * So, for mutated arguments, instead of setting lvalue, we check its presence.
+ */
+
+namespace tolk {
+
+GNU_ATTRIBUTE_NORETURN GNU_ATTRIBUTE_COLD
+static void fire_error_invalid_mutate_arg_passed(AnyV v, const FunctionData* fun_ref, const LocalVarData& p_sym, bool called_as_method, bool arg_passed_as_mutate, AnyV arg_expr) {
+  std::string arg_str(arg_expr->type == ast_identifier ? arg_expr->as<ast_identifier>()->name : "obj");
+
+  // case: `loadInt(cs, 32)`; suggest: `cs.loadInt(32)`
+  if (p_sym.is_mutate_parameter() && !arg_passed_as_mutate && !called_as_method && p_sym.idx == 0 && fun_ref->does_accept_self()) {
+    v->error("`" + fun_ref->name + "` is a mutating method; consider calling `" + arg_str + "." + fun_ref->name + "()`, not `" + fun_ref->name + "(" + arg_str + ")`");
+  }
+  // case: `cs.mutating_function()`; suggest: `mutating_function(mutate cs)` or make it a method
+  if (p_sym.is_mutate_parameter() && called_as_method && p_sym.idx == 0 && !fun_ref->does_accept_self()) {
+    v->error("function `" + fun_ref->name + "` mutates parameter `" + p_sym.name + "`; consider calling `" + fun_ref->name + "(mutate " + arg_str + ")`, not `" + arg_str + "." + fun_ref->name + "`(); alternatively, rename parameter to `self` to make it a method");
+  }
+  // case: `mutating_function(arg)`; suggest: `mutate arg`
+  if (p_sym.is_mutate_parameter() && !arg_passed_as_mutate) {
+    v->error("function `" + fun_ref->name + "` mutates parameter `" + p_sym.name + "`; you need to specify `mutate` when passing an argument, like `mutate " + arg_str + "`");
+  }
+  // case: `usual_function(mutate arg)`
+  if (!p_sym.is_mutate_parameter() && arg_passed_as_mutate) {
+    v->error("incorrect `mutate`, since `" + fun_ref->name + "` does not mutate this parameter");
+  }
+  throw Fatal("unreachable");
+}
+
+
+class RefineLvalueForMutateArgumentsVisitor final : public ASTVisitorFunctionBody {
+  void visit(V<ast_function_call> v) override {
+    // most likely it's a global function, but also may be `some_var(args)` or even `getF()(args)`
+    const FunctionData* fun_ref = v->fun_maybe;
+    if (!fun_ref) {
+      parent::visit(v);
+      for (int i = 0; i < v->get_num_args(); ++i) {
+        auto v_arg = v->get_arg(i);
+        if (v_arg->passed_as_mutate) {
+          v_arg->error("`mutate` used for non-mutate argument");
+        }
+      }
+      return;
+    }
+
+    tolk_assert(static_cast<int>(fun_ref->parameters.size()) == v->get_num_args());
+
+    for (int i = 0; i < v->get_num_args(); ++i) {
+      const LocalVarData& p_sym = fun_ref->parameters[i];
+      auto arg_i = v->get_arg(i);
+      if (p_sym.is_mutate_parameter() != arg_i->passed_as_mutate) {
+        fire_error_invalid_mutate_arg_passed(arg_i, fun_ref, p_sym, false, arg_i->passed_as_mutate, arg_i->get_expr());
+      }
+      parent::visit(arg_i);
+    }
+  }
+
+  void visit(V<ast_dot_method_call> v) override {
+    parent::visit(v);
+
+    const FunctionData* fun_ref = v->fun_ref;
+    tolk_assert(static_cast<int>(fun_ref->parameters.size()) == 1 + v->get_num_args());
+
+    if (fun_ref->does_mutate_self()) {
+      bool will_be_extracted_as_tmp_var = v->get_obj()->type == ast_function_call || v->get_obj()->type == ast_dot_method_call;
+      if (!will_be_extracted_as_tmp_var) {
+        v->get_obj()->mutate()->assign_lvalue_true();
+      }
+    }
+
+    if (!fun_ref->does_accept_self() && fun_ref->parameters[0].is_mutate_parameter()) {
+      fire_error_invalid_mutate_arg_passed(v, fun_ref, fun_ref->parameters[0], true, false, v->get_obj());
+    }
+
+    for (int i = 0; i < v->get_num_args(); ++i) {
+      const LocalVarData& p_sym = fun_ref->parameters[1 + i];
+      auto arg_i = v->get_arg(i);
+      if (p_sym.is_mutate_parameter() != arg_i->passed_as_mutate) {
+        fire_error_invalid_mutate_arg_passed(arg_i, fun_ref, p_sym, false, arg_i->passed_as_mutate, arg_i->get_expr());
+      }
+    }
+  }
+};
+
+void pipeline_refine_lvalue_for_mutate_arguments(const AllSrcFiles& all_src_files) {
+  visit_ast_of_all_functions<RefineLvalueForMutateArgumentsVisitor>(all_src_files);
+}
+
+} // namespace tolk