Add analysis of cpp2 declarations to check if deal with pointer type

Thanks to relocating pointer_declarators this change introduce deduction
of pointer types also from functions - if function or variable is defined
in cpp2 then cppfront has all information to deduce the proper type
during compilation.

Author: filipsajdak

a.out

@@ -1,3 +1,7 @@
+fun: (inout i:int) -> *int = {
+    return i&;
+}
+
 main: (argc : int, argv : **char) -> int = {
     a:     int = 2;
     pa:   *int = a&;
@@ -20,5 +24,8 @@ main: (argc : int, argv : **char) -> int = {
     pa5 := pppa**;
     pa5 = 0;  // caught
 
+    ff := fun(a);
+    ff = 0; // caught?
+
     return a*pa**ppa**; // 8
 }

regression-tests/pure2-deduced-pointers.cpp2

@@ -1,9 +1,10 @@
 pure2-deduced-pointers.cpp2...
-pure2-deduced-pointers.cpp2(6,8): error: = - pointer assignment from null or integer is illegal
-pure2-deduced-pointers.cpp2(9,9): error: = - pointer assignment from null or integer is illegal
-pure2-deduced-pointers.cpp2(12,9): error: = - pointer assignment from null or integer is illegal
-pure2-deduced-pointers.cpp2(13,9): error: += - pointer assignment from null or integer is illegal
-pure2-deduced-pointers.cpp2(17,9): error: = - pointer assignment from null or integer is illegal
+pure2-deduced-pointers.cpp2(10,8): error: = - pointer assignment from null or integer is illegal
+pure2-deduced-pointers.cpp2(13,9): error: = - pointer assignment from null or integer is illegal
+pure2-deduced-pointers.cpp2(16,9): error: = - pointer assignment from null or integer is illegal
+pure2-deduced-pointers.cpp2(17,9): error: += - pointer assignment from null or integer is illegal
 pure2-deduced-pointers.cpp2(21,9): error: = - pointer assignment from null or integer is illegal
+pure2-deduced-pointers.cpp2(25,9): error: = - pointer assignment from null or integer is illegal
+pure2-deduced-pointers.cpp2(28,8): error: = - pointer assignment from null or integer is illegal
   ==> program violates lifetime safety guarantee - see previous errors
 

regression-tests/test-results/pure2-deduced-pointers.cpp2.output

@@ -1568,6 +1568,37 @@ class cppfront
         if (!decl || !decl->declaration)
             return addr_cnt > deref_cnt;
 
+        // if it is a function check if it returns pointer type
+        if (auto* fun = std::get_if<declaration_node::function>(&decl->declaration->type)) {
+            if (auto* ret_id_expr = std::get_if<function_type_node::id>(&(*fun)->returns)) {
+                if (auto* unqual = std::get_if<id_expression_node::unqualified>(&(*ret_id_expr)->id)){
+                    return is_it_pointer_declaration(*unqual, deref_cnt, addr_cnt);
+                }
+            }
+        }
+
+        // if it is an object declaration check if we declare an pointer type
+        if (auto* obj_id_expr = std::get_if<declaration_node::object>(&decl->declaration->type)) {
+            if (auto* unqual = std::get_if<id_expression_node::unqualified>(&(*obj_id_expr)->id)){
+                return is_it_pointer_declaration(*unqual, deref_cnt, addr_cnt);
+            }
+        }
+
+        // if we initialize an object with a function check if it is initialized with a pointer type
+        if (decl->initializer && decl->initializer->suspicious_initialization) {
+            auto init_decl = sema.get_declaration_of(*decl->initializer->suspicious_initialization, true);
+            if (init_decl && init_decl->declaration) {
+                if (auto* fun = std::get_if<declaration_node::function>(&init_decl->declaration->type)) {
+                    if (auto* ret_id_expr = std::get_if<function_type_node::id>(&(*fun)->returns)) {
+                        if (auto* unqual = std::get_if<id_expression_node::unqualified>(&(*ret_id_expr)->id)){
+                            return is_it_pointer_declaration(*unqual, deref_cnt, addr_cnt);
+                        }
+                    }
+                }
+            }
+        }
+
+        // deduce if it is a pointer type based on number of dereferences and address of operations
         if (decl->declaration->dereference) {
             auto deref = sema.get_declaration_of(*decl->declaration->dereference, true);
             assert(deref && deref->declaration);
@@ -1604,18 +1635,9 @@ class cppfront
                 assert(unqual);
                 auto decl = sema.get_declaration_of(*unqual->identifier, true);
 
-                bool is_pointer = false;
-                if (decl && decl->declaration) {
-                    if (auto* obj_id_expr = std::get_if<declaration_node::object>(&decl->declaration->type)) {
-                        if (auto* unqual = std::get_if<id_expression_node::unqualified>(&(*obj_id_expr)->id)){
-                            is_pointer = !(*unqual)->pointer_declarators.empty();
-                        }
-                    }
-                }
-
                 // if initialized by something suspicious (that we have no information about) we need to add cpp1 safety checks
                 add_safetycheck = !decl && needs_safetycheck;
-                if (is_it_pointer_declaration(unqual) || !unqual->pointer_declarators.empty() || is_pointer) {
+                if (is_it_pointer_declaration(unqual)) {
                     if (n.ops.empty()) {
                         last_postfix_expr_was_pointer = true;
                     }